Problems with UK Glaucoma (POAG) Treatment
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CHAPTER 1: INTRODUCTION
Glaucomas are a group of diseases which have the potential of causing damage to the eye and are distinguished from other eye related diseases by the fact that they can cause an increase in intraocular pressure inside which in turn causes damage to the optic nerve and to the retina.
Primary Open Angle glaucoma (POAG) is the second commonest cause of registerable blindness and partial sight registrations in the UK (Bougard et al 2000). It is particularly dangerous because of its progressive nature and ability to go unnoticed for years thereby preventing treatment of the disease until, in some cases it can be too late to rescue the vision completely. Therefore the only way to detect the disease before it becomes a serious problem is with a thorough screening program. Optometrists usually are the first in line to examine a patient's ocular health and refer patients onto the hospital based on several risk factors.
The prevalence of POAG increases with age. This was shown in the Framingham Eye Study which estimated prevalence to be 1.2% between 50 and 64 years, 2.3% from 65 to 74 years and 3.5% in 75 years and over (Leibowitz et al, 1980). Another study has shown that POAG is positively related to the levels of intraocular pressure. The Baltimore Eye Survey concluded that the prevalence of the disease was 1.18% in patients with IOPs less than 22mmHg and 10.32% above this IOP level (Tielsch, 1991). Hereditary links have also been associated with POAG especially African-Americans who are at higher risk of developing the condition than Caucasians and, if there is a family history of glaucoma, the risk is up to six times higher than for the general population. Also, patients who are highly myopic, have diabetes mellitus or cardiovascular problems are at high risk of developing glaucoma and so these are the individuals who need to be monitored and checked regularly.
Thus, in the first instance it may seem appropriate to test all individuals who present as being at a (low) threshold risk of developing the disease at regular intervals for disease progression; however the numbers of patients who are referred for suspect chronic open angle glaucoma and then found to have no glaucoma is around 40%. These false positive referrals are thought to cause unnecessary anxiety to the patient, alongside adding to the volume of paperwork that is needed to be completed by the practitioner and also thought to be a waste of local hospital resources (Parkins, 2006). Hence, these matters alongside the increasing requirements for patient centered care and reducing the costs occurred by the NHS have led to the development of certain criteria which enables optometrists to refine their own referrals for glaucoma prior to deciding whether or not a patient should be referred. This can be made easier by carrying out simple procedures or following specific protocols, for example, repeating suspicious IOP measurements preferably at a different time of day by using a contact method (Perkins or Goldmann) and repeating visual field tests on a separate occasion. (Parkins, 2006).
More importantly, further schemes have been introduced where referrals are directed to specially trained optometrists who then decide on whether to refer the patient to the hospital eye service (HES) or return the patient for management under primary care. This appears to have ultimately increased the role played by optometrists in diagnosing and referring patients thought to be suffering from POAG, increasing their abilities to reach and treat individuals within the community more effectively. This in turn reduces the number of cases of POAG observed within the population as individuals are able to gain access to primary or more conventional methods of health care, i.e. hospitals. By reviewing the literature which has been published regarding the treatment and management of patients with POAG by optometrists, this paper aims to look at the way new schemes and interventions will affect the treatment and management of the disease within the UK. In addition, the ability of optometrists to prescribe certain drugs and the potential benefits will be discussed.
CHAPTER 2: GLAUCOMA IN THE UK. (EPIDEMIOLOGY)
This chapter will focus on the distribution, occurrence and control of the disease within the UK population. Glaucoma, as described above is one of the most frequent causes of blindness, predominantly in the industrialized world and therefore accounts for a high proportion of blindness observed within the UK. (Coyle and Drummond, 1995) The disease accounts for 14% of blind registrations in the UK and many cases around the country present at an advanced 'symptomatic' stage (Aclimandos & Galloway, 1988). With the potential to cause blindness in both eyes glaucoma has a dramatic effect on the individuals who are suffering from it but it also has a severe economic burden upon the nation, including direct and indirect costs. Within the UK alone these were estimated to be £132 million in 1990. (Zhang et al, 2001)
The most frequently prescribed drug for treatment of glaucoma is timolol which is a non-selective beta-adrenergic receptor blocker. The drug is used to treat open-angle glaucoma due to its ability to reduce the aqueous humour production by blocking the beta receptors on the ciliary epithelium. However, beta-adrenergic receptors blockers are thought to have serious side effects on patients who are suffering from cardiovascular or pulmonary disorders. For this reason an additional drug, 2-4 Pilocarpine, which is a cholinergic agonist may be used. This acts on a specific type of muscarinic receptor (M3) found on the iris sphincter muscle which causes contraction of the muscle and therefore miosis. This widens the trabecular meshwork through increased pressure on the scleral spur which aids the aqueous humor to leave the eye and reduce intraocular pressure. However this drug also has its limitations which are primarily associated with the requirement for it to be administrated four times per day and its ability to cause miosis, myopia and occasionally in some patients, retinal detachment and progressive closure of the anterior chamber angle. Thus, new drugs which will be more effective and safer methods of treating open-angle glaucoma are required. There have been many agents suggested for use for the treatment of the disease, however they often fail on several counts, including their failure to control intraocular pressure. (Schwab et al, 2003) This problem is observed within the three non-beta blocker drugs: latanoprost (a prostaglandin F2á analogue), dorzolamide (a topical carbonic anhydrase inhibitor), and brimonidine (a Selective á2 agonist). However, out of these three drugs, Latanoprost seems to be the most highly promising because of its comparable or, in some cases, better efficacy when compared with timolol. (Zhang et al, 2001)
Risk factors, which are associated with the development of the disease, include individuals who are members of a family pedigree, which have suffered from glaucoma in the past. (OMIM, 2006) It is thought that a family history of the disease increases ones likelihood of developing the disease by 6%. This is suggestive of a genetic link or predisposing factor which may be associated with the development of the disease. Diabetes and being of African descent are also factors which are thought to increase the likelihood of developing the disease, and individuals with either of these factors, are three times more likely to develop the disease than the average individual.
Asian populations have a dramatically higher risk of developing glaucoma than Caucasians, increasing their chances of disease development by a staggering twenty to forty percent. Men are also three times more likely to develop open-angle glaucoma than women due to the presence of wider anterior chambers in the eye. (Paron and Craig, 1976)
Evidence is becoming increasingly available to suggest that the levels of ocular blood flow are involved within the pathogenesis of glaucoma. Fluctuations in blood flow are more harmful in those with glaucomatous optic neuropathy than those who experience a steady reduction in the blood flow to their eye through the optic nerve head. This also correlates with the damage observed to the optic nerve head and to the deterioration in the visual field acuity. (National Institute of Health, web Reference)
There are also a number of studies which suggest that there is a correlation between glaucoma and systemic hypertension. This is linked with the fluctuations in blood flow mentioned above, as varying blood pressure can affect blood flow. There is however, no evidence that vitamin deficiencies play any role in the development of glaucoma. A survey carried out (Rhee et al, 2002) revealed that it is highly unlikely that vitamin supplements provide a useful treatment method for any individual suffering from the disease.
CHAPTER 3: SCREENING FOR GLAUCOOMA IN THE UK.
As we are now aware of the epidemiology of glaucoma within the population in the UK, it is clear that screening of individuals, particularly of those individuals at high risk of disease development is required. Many factors influence whether or not screening is considered a necessary precaution by ophthalmologists. However, it is perhaps first, most useful to provide an overview of what screening is and why it is a procedure invested in for treatment of open angle glaucoma.
3.1 Definition of screening
Screening may be defined as the examination of a group of usually asymptomatic individuals to allow the early diagnosis or detection of those individuals with a high probability of having a given disease, (Collegeboard, 2008) and it is often carried out on individuals who are considered to theoretically have a high chance of inheriting or suffering from the disease, due to either genetic or environmental factors or even a combination of these issues. It is thought that screening is useful when it enables the diagnosis of a disease earlier than it would usually have been detected giving the ability to improve the patient's outcome.
However, there are several ethical issues surrounding screening processes as some individuals are of the opinion that it is only right to screen for some diseases when an individual is at an age to consent to such a procedure. This raises issues surrounding the onset of screening procedures, and whether siblings and offspring of individuals with a family history of open angle glaucoma should be screened for the disease because of certain opinions that suggest the patient themselves should decide whether or not to be screened. This is debatable because of the implications on the individual's life and the worry which is associated with the knowledge of perhaps developing such a disease which could eventually lead to blindness.
However, due to the fact that the screening procedure gives the potential for treatment of the disease symptoms, it is likely that many ethical issues which surround some screening processes are not relevant to the screening of individuals at high risk of open angle glaucoma, particularly due to the fact that the genetic risk is minimal in comparison to the environmental risk factors and thus, genetic screening of parents and their offspring is not yet (and is unlikely to become) an issue.
3.2 Tests for glaucoma
There are several tests that are used to identify those patients with glaucoma, however, there is no single test that can determine whether a patient has the disease or not. To start with a thorough eye examination is a prerequisite prior to undergoing the specific tests for glaucoma. Following this examination, the management of glaucoma involves serial tests which are carried out at regular intervals over several years allowing the practitioner to determine whether the pressure in the eye has become stable and hence further damage will be avoided. Good record keeping is vital as it is only possible to determine whether the pressure has worsened by using previous values and measurements as a comparison.
The ‘Gold Standard' tests for glaucoma are determination of eye pressure with an application tonometer, assessment of optic nerve head and visual field screening. In optometric practice these tests are carried out once every year under NHS regulation, however, a patient under hospital management will usually be seen at least 3 or 4 times to monitor their intraocular pressure.
The established ‘Gold Standard' for intraocular pressure measurement is the Goldman applanation tonometer. To carry out this procedure, the Goldman head is mounted on a slit lamp and a drop of anesthetic a dye (fluorescein) is placed in the eye. Then a gonioprism is placed in contact with the cornea through which practitioner is able to see green rings and make adjustments to arrive at the end point where the half rings overlap. The eye pressure reading (in mmHg) is recorded at this position. There are several other means of recording intraocular pressure using different types of tonometers, which include the air puff tonometer, Perkins tonometer, Pneumotonometer and Schiotz tonometer. In addition, there are tonometers, which allow the estimation of eye pressure at home. One such example is the ‘proview eye pressure monitor' (Bausch and Lomb, 2001).
The visual field is usually the first to be affected in glaucoma and by the time the central vision is affected, the disease is already far advanced with almost all of the vision in the periphery permanently lost (Parks, 2006). Perimetric threshold-measuring techniques are sensitive to the early progression of such glaucomatous field loss and full threshold screening programs are seen as the ‘Gold Standard'. However, threshold tests can be lengthy and can induce fatigue within a patient causing them to lose fixation and overall lead to unreliable results. This lead to the development of SITA testing which reduced the testing time while maintaining the same quality of results as full threshold testing (Bengtsson, et al 1998). The computers, which are used to compute the visual field, are those such as the Humphrey or the Octopus perimeters. These machines use a light point that is presented in a predetermined fashion (location sequence) in a lighted bowl and the patient is asked to press a button when they see the light point. The patient's responses are analyzed statistically and compared with a database of ‘normal' responses. From this information, any deviations from normal are marked on a printout as black squares which represent visual field-defect areas. â€¨
Optic nerve head assessment is mandatory in all eye examinations performed and the ‘Gold Standard' method is the use of a Volk lens with the patient dilated. The preliminary signs of the disease occur at the optic nerve head where nerve fibre loss is apparent. However, it only until the loss of fibres exceeds a certain threshold that visual field impairment is noticed. Evidence from histological studies and glaucoma modelling has shown that up to 40% of optic fibres can be damaged before a loss of visual function takes place (Quigley, et al 1982). Diffused thinning and localised notching of the neuroretinal rim (NRR) indicate early signs of the disease. The cup is affected due to the loss of fibres and it widens and deepens as a result. Also, the optic disc of a glaucomatous patient will not follow Jonas' ISNT rule where the NRR is thickest at the inferotemporal sector, then at superotemporal, followed by nasal and temporal.
Clinical examination using a Volk lens is, however, affected by inter-observer variability amongst optometrists. Another useful technique is stereoscopic optic nerve photography which is a cost-effective method for the detection of glaucoma and its progression. With the benefit of 3-dimensional and permanent data, practitioners can study the optic nerve features (disc cupping, vessel baring) over time (Tielsch et al, 1988). Under hospital management, comparison of these photos which have been taken over the course of the year is a highly effective method of following glaucoma progression.
CHAPTER 4:HOW SUCCESSFUL ARE OPTOMETRISTS AT SCREENING FOR GLAUCOMA?
A number of studies and clinical trials have been carries out on the effects of treatment on newly discovered primary open-angle glaucoma patients, and it has been noted on several occasions that immediate treatment leads to a slower rate of disease progression. (Bullimore, 2002) As one must first identify that a patient has the disease before the individual can be treated, this ultimately implies that effective screening procedures would be beneficial in the treatment of glaucoma. However, one question which this leads to is: how successful are optometrists at screening for glaucoma and are all patients who should be screened, being checked for disease progression or any clinical symptoms.
4.1 The Baltimore eye Survey
The Baltimore eye survey (Tielsch, 1991) was carried out to evaluate the efficacy of population level screening procedures and evaluate the performance of the screening methods used to test for glaucoma. The research team noted that “…screening for glaucoma has a long history and is a well-established activity” (Tielsch, 1991). However, they also were aware that most screening organizations used tonometry as the screening technique even though it is known to have several limitations associated with its use. The efficacy of the other known screening processes were thought, by the research team, to have not received deep enough investigations into their effectiveness, and this was considered to be a reason why these methods were not being utilized in the screening processes.
In research studies which had been carried out prior to this study, only small research groups had been used or the studies had proved to being biased towards individuals who have a family history of the disease and therefore highly likely to developing glaucoma themselves. (Leibowitz et al, 1980) Hence the studies were thought to provide false information about the usefulness of the analyzed screening methods.
The Baltimore Eye survey looked at a total of 5,308 individuals who were forty years of age or older, including both black and white individuals and analyzed the success of screening each individual for glaucoma using “…tomometry, visual fields, stereoscopic fundus photography and a detailed medical and ophthalmic history.” (Tielsch et al, 1991) The survey was not limited to looking at individuals who were known to be at a high risk of developing glaucoma as this would influence the analysis of the success of certain screening methods. After the examination was complete, a diagnosis of glaucoma was made for any participant found to have indicative symptoms. Out of the 5,308 individuals participating in the study, 196 were diagnosed with glaucoma. (Tielsch et al, 1991)
The research team then evaluated tonometry, cup to disc ratio, and narrowest neuroretinal rim width for their ability to correctly classify subjects into diseased or non-diseased states. There was no defined cutoff values at which these variables provided a reasonable balance of sensitivity and specificity, (separately or in combination) as this made the test more robust and thus allowed the screening method to only gain positive results if it was able to identify an individual who did indeed have glaucoma. The statistical analytical methods used to analyze the data obtained from the study included making logistic regression models of the results, which were then fit to the data. These models included demographic and other risk factors, to ensure that the analysis of the data was as accurate as possible. Sensitivities and specificities were then calculated for varying cutoff levels on the distribution of predicted probabilities.
The research team came to the conclusion that there was no cut off for reasonable sensitivity and specificity and that the effectiveness of current techniques for glaucoma screening was limited. (Tielsch et al, 1991) The research said that although “at first glance, glaucoma fits the model of a disease for which screening could make a significant impact on the burden of disability in the population…unfortunately, objective assessments of the most commonly used technique for screening…demonstrate its ineffectiveness.” (Tielsch et al, 1991) The study identified that tonometry was a poor technique when it came to correctly classifying subjects as diseased or non-diseased. It also mentioned that despite intraocular pressure remaining as one of the strongest known risk factors for open angle glaucoma; measurements of this were not used as a criterion for referral in order to maximize the sensitivity of the screening examination. Tielsch et al (1991) identified only Only 215 subjects out of 1770 who were referred for further tests simply because of their intraocular pressure measurements and only four of these individuals actually had definite or probable glaucoma. This was a detection rate of 1.86 percent which is very low. Thus, the use of the intraocular pressure as a guide added little additional sensitivity beyond what was contributed by the other referral criteria. Other methods of screening for the development of glaucoma were also considered to be ineffective and cumbersome.
Despite this study being carried out forty years after the initiation of screening programmes for glaucoma, the program still appeared to require extra work in order to develop a more successful screening programme.
4.2 Frequency-doubling technology study
In contrast to the study carried out by Tielsh et al (1991) a study was carried out by Yamada et al (1999) with the aim to assess glaucoma screening using frequency-doubling technology (FDT) and Damato campimetry. The research group carried out a two day public glaucoma screening programme which was implicated at two different institutions. Each participant underwent the following visual field tests: Damato campimetry, FDT perimetry in screeningmode and Humphrey perimetry(24-2 FASTPAC). A full ophthalmologic examination, for each eye was also carried out. The data collected from this study was then divided into four categories, including normal, ocular hypertensive, glaucoma suspect and definite glaucoma. The sensitivity and specificity level of each test was then estimated with “receiver operating characteristic curves” (Yamada et al, 1999). The results of the eye examinations revealed that out of the 240 individuals who underwent testing, 151 were identified as being normal, 28 were classified as ocular hypertensive, 35 were described as having suspect glaucoma and 26 were classified as being definite glaucoma individuals when using the FDT perimetry screening mode. Out of the one hundred and seventy five subjects who underwent Damato campimetry, the numbers for the same groups were 118, 19, 19 and 19 respectively. The specificities for each test were 92-93% for the FDF perimetry and 53-90% for the Damato campimetry tests respectively, hence leading to the conclusion that FDT perimetry was superior to Damato campimetry in the screening for glaucoma within the study. (Yamada et al, 1999) However, these methods for screening are rarer than the usual tonometer and visual field analysis methods described within this paper. Despite the fact that they appear to be useful and effective methods for glaucoma screening in this case, the tests are rarely used in conventional practice and therefore the results of this study should be regarded with caution.
4.3 Burton Hospital screening study
The aim of this study was to investigate the “referral practices to the outpatient clinic of a consultant ophthalmologist” and also to identify the current screening routines of optometrists and general practitioners in regards to glaucoma and diabetic retinopathy diagnosis. (Harrison, et al 1988)
A total of 1437 patients were referred to Burton District Hospital, from 1 November 1986 to 31 December 1987, to be viewed by a consultant ophthalmologist. The patients were grouped into urgent, semi-urgent or non-urgent depending on their referral letters. Only 1113 patients were ultimately reviewed as the remaining 324 could not be seen by the end of the study. (Harrison, et al 1988) Selected biographical data was recorded from the case notes such as age, sex and more importantly the source of referral. Any symptoms as well as the reasons for referral were looked for in the referral letters. A classification system was used for the reason for referral; this was based on symptoms and bodily location. Furthermore, there was an analysis on the referral data for the procedures used by the referring source, in this case assessment of visual acuity, visual fields, binocular vision and the optic nerve head. Also, intraocular pressure readings as well as any fluorescein checks for corneal staining. (Harrison, et al 1988)
The results showed that optometrists were responsible for 39% of the referrals (439 patients) in comparison to the 49% (546 patients) of general practitioners. The most important reason for referral was visual field loss which account for 31% (345) of cases, followed by suspected glaucoma which accounted for 13% (145). The reasons for referral were also different when comparing the two referrers. GPs referred 107 (84%) patients due to eyelid disorders and 66 (77%) patients with conditions on the outer adnexa. On the other hand optometrists were responsible for referring 118 (81%) of the patients on suspicion of glaucoma. (Harrison, et al 1988)
In total there were 70 referrals for possible asymptomatic glaucoma and another 77 for symptomatic disease. In 33 cases glaucoma was confirmed (20 asymptomatic) and borderline glaucoma was found in 73 cases (48 asymptomatic). “The diagnosis was confirmed in 96 (80%) of the referrals from ophthalmic opticians but in only 10 (37%) cases referred by general practitioners.” (Harrison, et al 1988) This showed that optometrists were far more accurate in referring suspect glaucoma patients, i.e. a greater number of true positives. Using information from the referral letters, the diagnostic procedures undertaken by both referral sources was explored. Optometrists relied on intraocular pressure readings in 52 of the 96 referrals (54%). The rest of the patients were referred because of suspicious cup-disc ratios, visual field loss or other clinical aspects. However, GPs would refer mainly on the grounds of symptoms that are present. Also, the ophthalmologist did not confirm suspect glaucoma in 24 patients from the optometrists' referrals and 17 from the referrals by GPs.
The main conclusions from the report show that optometrist were far more likely to refer retinal or optic disc disorders. There was insufficient evidence to show that GPs screened for glaucoma “whereas ophthalmic opticians screened for glaucoma with considerable skill.” (Harrison, et al 1988). Several factors contribute to these differences between the referral abilities of both professional groups. Patients will normally visit an optometrist when they are experiencing visual loss because they are usually under the impression that they require new glasses. However, when patients have external symptoms they normally go to their GP. Due to the equipment available to optometrists they are also more likely to pick up on pathologies within the eye especially those affecting the retina and optic nerve head, hence “maintaining a high degree of vigilance for asymptomatic conditions such as glaucoma.” (Harrison, et al 1988) The suggested diagnostic accuracy, however, undermined the actual accuracy of the opticians' examination. Any difference was due to the importance given to the findings of the ophthalmologist.
The quality of referrals to the hospital is vital for maintaining an effective service, especially in Britain where many outpatients departments are overstretched. Improvement in the accuracy of referrals eventually leads to less false positive referrals, therefore enhancing the value of true positive referrals. One of the protruding reasons for false positive referrals in this study was suspected glaucoma but with “greater utilisation or development of community based screening programmes” the false positive referral rate could be reduced. Harrison, et al (1988) states that currently the closest approach to a screening programme is offered by optometrists.
Harrison et al (1988) is also of the opinion that by establishing a planned screening service where ophthalmologists and optometrists work in conjunction on the basis of a fixed referral criteria, the progression of the disease in patients will reduce and so will the burden on HES. There is evidence from the data within the study to show that such glaucoma screening programme would have an influence. The 41 false positive glaucoma referrals would have been prevented and so would most of the 73 referrals for borderline glaucoma. A potential 100 outpatient appointments could have been saved with a community based screening strategy and this in turn would free up follow-up appointments.
The study does show the benefit of current screening procedures and how optometrists are successful at accurately referring suspect glaucoma patients. Harrison, et al (1998) highlights that this is an invaluable skill which would prove more beneficial if used within a community based screening scheme.
4.4 England and Wales survey
The objective of this survey was to investigate “the efficiency of referral for suspected glaucoma to general practitioners and consultants by optometrists.” (Tuck & Crick, 1991) This survey involved 241 optometrists who represented areas clustered in England and Wales. Majority were enrolled through an interview procedure, but some responded to an advert in optometric publications. The scheme ran from November 1988 to February 1989 and each time a referral took place the optometrist would fill out a questionnaire on the individual patient. In total the respondents completed 275600 sight tests, which accounted for “about five per cent of the national total”.
The actual number of referrals was 1505 for those suspected of glaucoma. For people over the age of 40 an estimated 0.9% referral rate was found. The end result of the referral was established for 1228 individuals. There were 125 patients were not examined at all and the remaining 1103 were examined by a consultant ophthalmologist. (Tuck & Crick, 1991)
An analysis was done on 704 cases to assess the accuracy of the referrals. Glaucoma was confirmed in 40.19% (283) of patients and 31.53% (222) of patients were further monitored. The data showed that in nearly all the confirmed patients the disease was at a chronic stage. Optometrists were further questioned to specify the key reasons for referral in each of the cases. There were 171 patients referred due to intraocular pressure in at least one eye being greater than 30mmHg. From these, 112 (65%) were positively diagnosed with glaucoma and only 20 were discharged as false positives. It was noted, however, that accuracy of referral in patients with lower IOPs (20-25mmHg) was much less. Only 7 individuals out of the 87 with lower IOPs were found to have glaucoma. Amongst them 50 patients who were released with no glaucoma. (Tuck & Crick, 1991)
When the optometrist recorded optic nerve head changes and visual field plots, the IOP referral accuracy was greater. However, when the referral was based on optic disc appearance and visual fields alone the accuracy was low. This category of referral accounted for 28 (10%) of confirmed cases. Furthermore, only 331 of the 704 patients had undergone a visual field test. This explained those cases in which visual field loss was not described as a reason for referral because the screening test had not been carried out in the first place. Even so, the analysis stressed “that field screening generally enables a case to be more precisely described and the risk of glaucoma thereby better assessed at the primary level.” (Tuck & Crick, 1991)
Gathering the evidence from the survey, it was shown that two in three referrals were justifiable based on the patient either being diagnosed with glaucoma or being called back for additional tests. IOP readings alone resulted in 13% of referrals from optometrists with two fifths of confirmed cases having readings above 30mmHg. Further analysis of the data suggested that at the point of referral optometrists could rightly judge whether a patient was almost certain to have glaucoma. (Tuck, 1990)
Tuck & Crick (1991) are of the opinion that detection rates would benefit if optometrists were encouraged to utilise all three main testing procedures for glaucoma. Tonometry when carried out routinely is significant especially when carried out in patients over 40; this is shown in survey results. Also, the error present when referral is based on an individual test can be minimised if using the three tests in combination. Optometrists should test their referred patient using a visual field screening programme which would allow “the patient's risk of glaucoma to be better defined.” (Tuck & Crick, 1991) Overall, the survey has shown that the screening system currently in UK is suitable but further improvement would be necessary. Optometrists are generally accurate with their referrals especially when using all three tests as a basis. This is where a community-based screening programme could be developed with set referral criteria including the main testing procedures.
4.5 Health Technology Assessment case study
The Health Technology Assessment (HTA) system carried out research into the procedures which were carried out by researchers from the University of Aberdeen to see whether the screening procedures in current practice for open angle glaucoma met the standards set by the UK's National Screening Committee. (Burr, et al 2007) The research team also reviewed previous studies to assess the accuracy of screening tests for POAG and to determine the cost-effectiveness of alternate strategies.
Two alternate strategies were developed for a screening programme, which were compared to the current procedure in the UK of “opportunistic screening”. The first strategy which the research team investigated was the use of a glaucoma-trained optometrist. These optometrists receive extra training in the diagnosis and monitoring of glaucoma and are certified by a consultant ophthalmologist. In this strategy, a thorough ophthalmic examination was carried out, including optic nerve assessment, visual fields and IOP measurement. Any participant considered to be at a high risk of glaucoma was referred immediately to an ophthalmologist for a definitive diagnosis. (Burr, et al 2007)
The second screening strategy participants underwent a measurement of IOP and a single screening test by a trained technician. There was a cut-off in IOP of 26mmHg, carried out with applanation tonometry, in order to identify groups at “higher pretest probability of developing serious OAG”. (Burr, et al 2007) Those with an IOP less than 26mmHg were examined with a second test, chosen on the basis of diagnostic accuracy as well as on patient ability to undergo the test. If the results on this second test aroused any suspicion the patient was referred to a glaucoma-trained optometrist for further diagnostic procedures.
Markov sub-models were then constructed to represent and compare the cost-effectiveness of the strategies. These models are useful when representing “the logical and temporal sequence of events following the implementation of alternative screening strategies”. In this case the model illustrated the estimated costs and outcomes of selected groups of patients for the screening strategies involved. (Burr, et al 2007)
The results of the trial appeared to conclude that the technician strategy was the most cost effective strategy especially in populations where there is a higher prevalence of the disease. A 3-4% prevalence is required in 40 year olds with a 10 year screening interval in order to approach cost-effectiveness. For 50 year olds a similar prevalence of 4% is needed with a 10 year screening interval. However it was noted that general population level screening for glaucoma at any age was not a cost effective screening strategy and did not meet the National Screening Committees (NSC) criteria for initiation of a screening programme. Despite these conclusions however, it was noted that the screening of special sub-populations or individual groups of people, especially those with family history or Afro-Caribbean ethnicity, was effective. (Burr, et al 2007)
In regards to accuracy of individual screening tests, most proved to have a specificity of over 85%. However, it was not possible to determine whether any individual test was superior because of the “strongly heterogeneous nature of the data”. (Burr, et al 2007)
4.6 The effects of screening case study
Harris (2005) published a paper which aimed to address whether screening for glaucoma could be an effective method of helping patients to avoid glaucoma. His paper addresses some of the negative implications associated with the screening process, and is of the opinion that “although it is difficult to be opposed to finding disease earlier—screeningsometimes does extend life and/or improve the quality of life—screeningalso has its down side.” (Harris, 2005) The idea behind this statement is that screening individuals for disease can ultimately lead to individuals who are asymptomatic and who do not have a disease looking for one, thus creating unnecessary worries within the population. Harris says that “the harder we look for disease in asymptomaticpeople, the more we find not only the diseases that we seek,but also ‘pseudo-disease'—conditions that have some appearanceof disease but never cause problems for real people.” (Harris, 2005) This opinion leads to the ideology that there are seldom screening methods developed which do not ultimately lead to a pseudo-disease status arising. The development of pseudo-disease can cause as many problems as the screening procedure may be able to solve, because although it is highly unlikely that individuals will die from a pseudo disease, their lives may be affected to arguably as great a level as those individuals who are identified as having a diseased status.
In addition, it is often to distinguish pseudo disease from real disease and as “our current medico-legal climate limits the degree towhich we can ignore pseudo-disease.” (Harris, 2005) Many of the cases of pseudo-disease ultimately lead to the investigation, monitoring and treatment of pseudo-disease which costs the NHS money which instead could be spent on helping individuals who are actually suffering from real glaucoma and not merely a hypothetical version of the disease. Ultimately, this leads to the overtreatment of a high percentage of individuals, which is a major downside of carrying out screening procedures. Also, the referrals from optometrists are further scrutinised because they will contain a large number of false positives, contributing to pseudo-disease. Therefore, Harris (2005) is of the opinion that the ideal way to control overtreatment and pseudo-diseaseis to manage the screening process in the first place.
The paper further highlights the fact that visual impairment due to glaucoma is an importantproblem for many elderly people and especially within the African-American population. As a consequence of this, glaucoma is a condition worthy of ourattention and continued research. However, there is one issue in regards to the screening process, which Harris (2005) does not agree with and this is the methods which are currently practiced for dealing with the disease. US Preventive Services Task Force (1996) state that evidence based medicine has for years highlighted the lack of evidence that “reducing intra-ocularpressure (IOP), the primary treatment for primary open-angleglaucoma, improves vision.”
There has however, been research carried out by the ophthalmologicalcommunity in the form of randomized controlled trials which were able to clear any doubts regarding the ineffective methods. According to Kass et al (2002), a meta-analysis of the bestof these trials on the effectiveness of using IOP as a screening method for glaucoma was carried out. The first debatable question is whether lowering IOP amongpeople who have increased IOP but no visual field defects reducesthe development of visual field defects, and this was researched by using a single large trial to study the effects. A group of 1636 participants with no evidence of glaucomatous damage were treated with topical hypotensive medication. They were between 40 to 80 years old and had IOPs between 21-32 mmHg in both eyes. (Kass et al, 2002) The findings of the study showed that treatment of patients withincreased IOP reduces the development of visual field defectsby more than 40%. This is a significant percentage, hence highlighting the importance of screening using IOP as a method for identifying patients with glaucoma.
The second question which was addressed was whether lowering IOP among people withearly, asymptomatic visual field defects would reduce the developmentof further visual field defects. The results of the meta-analysis, based on a single, large trial (Heijl et al, 2002) again suggested that yes, this did reduce the progression of further visual field defects by approximately 35%.
However, one must be careful when analyzing the results of studies which have been carried out to assess the effectivity of such research trials. For example, these studies used very sensitive devices to measure the differences between patients, which the patient themselves may have been unaware of. In addition, theextent to which these small visual defects will allow the diction and diagnosis of patients suffering from glaucoma is largely unknown and thus when research teams declare that the lowering of IOP is beneficial to each patient in the reduction of long term damage, they are actually discussing benefits which are not usually noticed by the patients themselves. For this reason, it may be questionable as to how this suggests that the use of screening methods to detect such changes is a justifiable method for use in optometric practice. To add to this, neither of the research trials which were carried out were able to demonstrate a clear difference in visual acuity between the treated and un-treated patients. Furthermore, a recently published study found that there was no difference observed between the vision-related lifestyles of treated and un-treated patients. (Hyman et al 2005) This leads one to ask the question as to how beneficial IOP tests and treatments are in the treatment of glaucoma, especially when these tests form a crucial part of an optometrist's decision to refer a patient on for further screening. When asking this question however, one must bear in mind that open-angle glaucoma is a chronic condition which effects mainly the older generation and thus as a consequence, the symptoms of the disease are rarely observed within the younger generation. Also, some individuals who have early field defects may not evenlive long enough to develop significant visual problems. (Quigley, 1996)
The vision is what crucially becomes affected by glaucoma and the main question is whether screening helps to identify those patients in order to avoid the negative impact on their vision-related everyday life. Further analysis of the research studies that assess vision-related quality of life will help in answering this uncertain question. Also, as seen above there are doubts placed on the screening procedures within primary care as many of the tests are seen as not feasible, nor accurate or reliable. Patient psychology is also affected by these procedures, with many reporting depression and fear when being diagnosed as having glaucoma. (Harris, 2005)
CHAPTER 5: NEW SCHEMES FOR IMPROVING THE QUALITY OF REFERRALS FROM OPTOMETRISTS FOR GALUCOMA.
Optometrists are responsible for the majority (90%) of referrals of patients for glaucoma in the UK. The current strategy involves opportunistic based screening, where the optometrist will rely on the results of the tests available in practice. Wormald & Rauf (1995) described the current situation as “opportunisticsurveillance, with no attempt to define clearly, or cover, the entirepopulation at risk”. Working to new locally agreed protocols, specially trained optometrists can decide if patients can continue to be managed in the community or if they need to be seen again by the Hospital Eye Services (HES) before the routine review. These optometrists receive further training in the diagnosis and management of glaucoma so that they are able to make such decisions. Overall, this ensures that only the patients who require hospital based treatment will be referred for further medical attention, thus cutting down the number of unnecessary referrals and enhancing the treatment of individuals who are referred.
In addition, the glaucoma referral scheme includes HES determined levels of required equipment (such as Goldmann tonometry instead of NCT) and standardized methods of visual field analysis, and the initiation of any new schemes are required to be financially viable for all parties. The new schemes aim to allow patients to be seen who are more appropriate for that service, with shorter waiting times. (Association of Optometrists, 2000)
There are a variety of different refinement schemes in progress within different areas of the country. Although these schemes all operate on a slightly different basis, they are ultimately aiming to achieve enhanced and effective patient treatment as well as availability of the HES to those patients who require it. The Newcastle scheme for glaucoma management exemplified this by reducing waiting times and ensured that only individuals who require hospital eye services received them so that there is little waste of resources and patients time. (Vernon, 2003)
5.1 The Macclesfield Scheme
The Macclesfield scheme was set up to investigate the viability of utilising the skills of optometrists to support the GPs in the diagnosis and management of open angle glaucoma. Alongside this argument is the fact that optometrists also have the desired equipment to carry out eye assessments and with the newly assigned prescribing rights, this allows optometrists to manage the care of their patients to a much greater degree.
As the knowledge of diagnosing eye disease to the required level is well within the capabilities of community optometrists, GPs can provide a better standard of care for patients, which is faster and more convenient. This is achieved with the introduction of a referral refinement schemes which use a glaucoma-trained optometrist as “a triage resource” hence reducing the unnecessary referrals to the HES. The patient is referred to such an optometrist by the GP for preliminary screening if there is any suspicion of the disease. Then by working to an agreed protocol optometrists refer only those individuals who show a high probability of developing glaucoma to the ophthalmologist. “This refinement of the referral would be identical to that undertaken within the HES, but would cut back on unnecessary hospital visits.” (Association of Optometrists, 2000) The scheme was run for a year with the intention of reviewing the outcomes at the end and basing its long-term future on the findings. Optometrists were selected from the local area and had to meet a certain requirements, e.g. the successful completion of a course in therapeutics. Statistical evidence which supports the success of the referral scheme has shown that the scheme has reduced the number of false positive patient referrals, and thereby increased the percentage of patients who are referred who end up having surgical interventions from 64% to 97%. (Association of Optometrists, 2000) Thus is clear evidence that the scheme is working in increasing the efficiency of patient treatment and glaucoma diagnosis, as no patient would be allowed to undergo unnecessary surgery.
5.2 The Manchester Scheme
The Manchester referral scheme was similarly based upon referral of a patient with suspected glaucoma to an accredited, community trained optometrist. The scheme co-ordinators initially invited 100 Manchester optometrists for a preliminary conference where details of the scheme were explained. The end result was that 18 optometrists continued with the course for accreditation, after which they were equipped with “superior skill” necessary to work under the scheme. A pre-determined and fixed set of referral criteria was then agreed so that any patients who met these conditions were referred directly to Manchester Royal Eye Hospital (MREH) and those who did not were sent back to the referring non-accredited optometrist. In all cases, information about the patient's assessment was sent to the GP (Association of Optometrists, 2000).
Over the course of the year 194 patients were monitored through the scheme, and 58% of them (112) were referred to the hospital. Overall, the scheme was observed to reduce the number of suspect glaucoma cases referred to the MREH by 40% and this figure reflected the number of false-positive referrals to the hospital which were observed in 1997. (Henson et al, 2003) Referred patients were also examined within 2-3 weeks time in comparison to the 2-3 month wait using the old referral system. This reduction in the number of patient referrals is a result of several factors. Firstly, examination by the accredited optometrist with the use of IOP testing, visual field screening and optic nerve assessment, reiterated the findings of the original optometrist. Furthermore, the accredited optometrist was at the advantage of applanation tonometry and binocular indirect viewing of the optic nerve head, which is thought to produce more accurate results compared to non-contact tonometry and direct ophthalmoscopy. (Henson et al, 2003) These factors contributed to the reduction in referrals in conjunction with the training programme for the optometrists where they were able to refine their skills on optic nerve head evaluation.
One of the outcomes of the scheme was a reduction in waiting times for appointments and in addition, information accompanying referral has found a financial cost saving to the NHS of approximately £17 per patient. Also, patients would feel less anxiety and stress as all the tests are carried out in one session instead of being passed around within the healthcare system. Another benefit of the scheme was the “clear reporting pathway with clear lines of responsibility.” (Henson et al, 2003) This made the accredited optometrists liable for any decisions they undertook with protection from their professional insurance.
One aspect of screening procedures that has not been reported is the false positive rate of the accredited optometrists. This type of data would be valuable as it would allow an assessment on the accuracy of referrals made by these optometrists. Patients would have to make several visits to the MREH in order to produce reliable statistics in regards to this. It is reported though that 36% of referrals are being monitored under the hospital and in the imminent future they could either be discharged (a false positive) or further treated (a true positive). A future study on this would prove very useful in reviewing the success of the scheme. As a whole, Henson et al (2003) are of the opinion that “the community refinement of suspect glaucoma offers some important benefits over the current referral pathway.”
5.2 The Peterborough scheme
The primary aim and objective outlined by this scheme was to “share the management of new and existing glaucoma patients in the community with specialist ophthalmologists.” (Ramirez-Florez, 2008) It was thought that the scheme would save many patients from coming into the hospital as well as freeing up many of the appointments for patients with greater risk of disease development. Therefore resulting in a positive impact upon the functioning of the NHS by speeding up the time taken for treatment and providing patients with coherent information in regards to their condition. In 2004-2005 the eye department within Peterborough Hospitals dealt with 7100 fresh referrals and 29100 patients requiring follow-ups. It was estimated that 20% of these routines were due to glaucoma. (Ramirez-Florez, 2008) Sometimes, referred patients would go 8-10 months without being seen and due to the lack of clinical capacity it became very difficult to meet patient's needs. As the government introduced a target to see patients within 17 weeks the eye department encountered extra costs to pay for locum staff as well as extra clinics. Ultimately this led to the initiation of this referral scheme where the consultants judge the urgency of the appointment and pass the patient to a community “trained and approved specialist optometrist in glaucoma (SOG).” (Ramirez-Florez, 2008) A framework was set in place by the hospital with clear protocol and guidelines dictated by inclusion and exclusion criteria which would enable the optometrist to decide whether or not it was necessary for a patient to be then referred to a Consultant Ophthalmologist.
All the eye doctors in the eye department are involved in the training of future SOGs. Theory sessions were organised in July 2004 and February 2005 which consisted of 3 evenings of 2 hours each, after which practical sessions took place on visual fields, applanation tonometry, optic nerve head assessment and further examination techniques. Then at the discretion of the training doctors, certain optometrists were accredited to examine patients within the scheme. Three phases are in use as a progression for the scheme where the first phase involves the SOG examining patients and sending the clinical findings and data to the hospital for review. A Consultant Ophthalmologist then fills the audit form and sends this with an outcome letter to the patient, GP, SOG and the original referrer. The GP then starts the treatment process. The SOG refrains from discussing any findings with patients as there may be possible disagreements between the SOG and consultant. All the results are audited and when there is very close agreement then the second phase is initiated. The SOG is given more independence in this second phase where they only need to send information if they believe that a patient requires further treatment. They can advise those patients who are normal and discharge them back into the hands of community optometrists. In the third phase optometrists might be able to start treatment of patients directly through potential prescribing rights. This is on the condition that both parties are in firm agreement on the completion of the previous two stages.
To assess the extent to which the Peterborough scheme was successful, a study was completed by (Ramirez-Florez, 2008) which included 392 patients, of which 15 % had stable glaucoma, 49% were thought to be at risk of glaucoma, 17% had ocular hypertension and the rest were normal. These patients were seen by 7 SOGs between February 2005 and January 2006. The completed forms were assessed by a Consultant Ophthalmologist in regards to cup disc ratio, visual field assessment, diagnosis, suitability, treatment plan and outcome. There was an agreement of 66%, 83%, 77.75%, 91%, 86% and 57% respectively, between the consultant and SOG. One hundred questionnaires were also sent out to patients with 72% being returned. The key highlights from the results were that 98% of patients were extremely satisfied with the scheme, 94% felt that appointments were completed in a convenient time and 80% of patients waited no longer than 15minutes before the appointment time. There is data to support this, showing that “the initial standard of assessment have significantly improved quality of care; all patients are seen in the time requested, all having had visual fields done at the same time, all patients have optic nerve recorded images for future assessments.” (Ramirez-Florez, 2008)
Therefore it can be concluded that this community glaucoma shared care scheme has resulted in a uniform, punctual and high standard of management combined with treatment of patients. From the evidence gathered, it would be fair to say that such schemes could be a practical alternative to the current referral procedures in the UK. However, it must be noted that further long-term evaluation is necessary in order to develop a safe and effective protocol. (Ramirez-Florez, 2008)
CHAPTER 6:CO-MANAGEMENT SCHEMES FOR GLAUCOMA.
Alongside the newly designed schemes in which trained optometrists are responsible for referring patients with glaucoma to be seen by a hospital specialist, patient co-management schemes exist in which the patient care is managed in conjunction with both ophthalmologists and GPs. Examples of such schemes include the Bristol and Peterborough schemes.
6.1 The Bristol scheme
The aims of this randomised controlled study were to assess whether community optometrist were “able to make valid measurements of visual parameters in patients with established or suspect primary open angle glaucoma” and to determine patient contentment in regards to this. (Gray et al, 1997) Collected data from glaucoma clinics within Bristol Eye Hospital has revealed that nearly 23% of outpatient attendances are for patients with glaucoma follow-up. Also two thirds of consultant ophthalmologists in South Western England estimated that between 10 and 25% of their outpatient time was allocated to glaucoma patients. (Spencer, 1992)
In total 403 patients with established or suspected POAG from the hospital were recruited for the study based on set inclusion and exclusion criteria. Eligible patients were then invited for a thorough assessment by an independent research team which included a registered optometrist, and ophthalmological registrar and a special nurse with training in field testing. Now the patients were randomly allocated to either the HES or to optometrists within the community. The split was 200 and 203 patients respectively. (Gray et al, 1997) Those within community care were seen at 6 month intervals and the optometrists “were provided with the patient's personal details, diagnosis, medical and surgical treatments, and the threshold for Henson CFA3000 field analysis.” The hospital patients represented a control group to find out the degree of change over the two year study period and the groups were reassessed after two years.
All optometrists in the region were sent a questionnaire to establish whether any would be interested in taking part in the study. Only twelve were suitable in terms of equipment available and geographical location. The non-participating optometrists were asked permission to allow their patients to be seen by the study optometrists if necessary. As with previously mentioned schemes, the study optometrists required training to a degree in which they would be able to recognize and successfully treat certain symptoms of glaucoma and would be able to acknowledge when the appropriate time would be to refer the patient to the hospital. This included 15 hours of theory and 10 hours of practical experience on glaucoma patients who willingly volunteered. (Gray et al, 1997)
Patients were also content with this scheme and the majority of patients who participated completed questionnaires. The response from the HES group was acceptable but not comparable to that from the community group. It is possible that patients within the HES felt less engaged by the study compared to the community group who received care at routine intervals.
After two years the research team carried out measurements again on all patients which were compared to those taken before randomisation two years ago. “The mean number ofmissed points on visual field testing in the worse eye, mean intraocular pressure(mm Hg), and cup disc ratio using a “better/worse” eye analysis in each group” were measured (Gray et al, 2000). By calculating the covariance an analysis was carried out to compare the results. Extra controls were established for sex, age, diagnostic group (suspect glaucoma/established POAG) and treatment if any. For visual field screening the mean number of missed points for the better eye was 7.9 points for hospital and 6.8 for community and the worse eye produced 20.2 and 18.4 respectively. Pressure readings for the better eye was 19.3mmHg in hospital and 19.3mmHg for community with the worse eye reading 19.1mmHg and 19.0mmHg respectively. The cup-disc ratio in the better eye was 0.72 for both groups and 0.74 in the worse eye again for both groups. The differences in the key variables between the two groups were not significant and this was even after making adjustments for baseline values. (Gray et al, 2000)
In conclusion the scheme proved that it can work effectively for a proportion of patients with POAG using community optometrists. However, after two years there was no significant statistical difference in the result between HES patients and those within community care. To successfully implement such schemes the cost and “local circumstances, including geographical access and the current organisation of glaucoma care within the hospital eye service need to be taken into account.” (Gray et al, 2000)
6.3. Hospital based schemes
In the ideal world, any patients thought to be suffering from glaucoma would be seen regularly by a glaucoma specialist, who would have enough time and resources to provide the patient with an informed choice of management. However, in today's aging population, this is becoming increasingly difficult due to the number of elderly individuals within the population and the subsequent increase in the number of glaucoma cases observed. However, the Nottingham scheme for management of glaucoma patients is based on a hospital scheme, in which all patients suffering from glaucoma are seen by specialist optometrists within their normal clinical sessions in the hospital setting. (Vernon and Davidson, 2007) Here, the specialists will assess patients referred from the Community Optometrist to establish if they have glaucoma and undertake appropriate management and follow up for each patient themselves. Thus, unlike the Peterbourgh and Bristol schemes, in this case it is the specialist and not nursing or other less qualified professionals who look after the health of patients once they have been referred. The outcomes of this care scheme are the maximisation of patient care and management, whilst providing the patient with the necessary information about their disease. In addition, the outcomes of the consultations made by the specialists will be referred to the patients GP to ensure that the patient has a close port of contact if necessary. Although this scheme appears to fit in well with the desired and optimal situation which could be seen for the patient care and management in glaucoma, it is debatable whether this scheme will meet the necessary targets and minimise the waiting times of patients with glaucoma. If the scheme does not meet the necessary requirements, it is unlikely that the scheme will prove to be successful because many patients will fail to be seen in the clinic in time for effective treatment to commence.
CHAPTER 7:NEW LEGISLATION FOR THE USE OF THERAPEUTIC DRUGS BY OPTOMETRISTS.
Optometrists have been allowed to prescribe ophthalmic therapeutic drugs for many years via exemptions from the Medicines Act 1968. However, in the past, the reagents prescribed have been severely limited in number. New legislations in the prescribing rights of optometrists have been granted by the Medicines and Healthcare products Regulatory Agency (MHRA) due to the Crown Review of 1999, which recommended that &ldqu
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