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Clinical decision making in glaucoma

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The College of Optometrists

Continuing Education
Andrew I. McNaught, MD, FRCOphth, Cheltenham Eye Unit, Gloucestershire

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Clinical decision making in glaucoma
Introduction
The hospital management of a patient referred as a glaucoma suspect can be usefully divided into three stages: 1) diagnosis 2) monitoring 3) clinical decision making (including therapy and frequency of review) When establishing a diagnosis, it is important to reach a clear decision as to whether the patient has glaucoma, is normal, or shows some suspicious signs which might indicate a higher risk of developing glaucoma in the future. In the case of primary open-angle glaucoma (POAG), especially early disease, this can sometimes be surprisingly difficult, and the decision rests on logical interpretation of the signs visible at the optic disc, and within the visual field (VF). The intraocular pressure (IOP), and other risk factors, e.g. family history (Fhx) provide useful confirmatory information. Glaucoma is conventionally diagnosed as the presence of glaucomatous cupping of the optic nerve head associated with perimetric evidence of a glaucomatous VF defect. The IOP will often, but not always, be higher than 21mmHg. Research work has shown that the earliest signs of glaucomatous damage are structural, i.e. cupping, and other optic disc signs and/or retinal nerve fibre layer (RNFL) loss, which may be focal or diffuse. Indeed, even in the absence of a VF defect, a sufficiently suspicious optic disc appearance in association with a raised IOP will be diagnosed, and treated as glaucoma by many clinicians. VF defects as measured by conventional white-on-white (W-W) perimetry are typically a later sign of disease, although may be the earliest sign in patients with small, anomalous, or otherwise difficult to interpret discs. There are, however, more recently described tests of visual function, e.g. motion sensitivity, or blue on yellow (B-Y) perimetry which may detect the disease at an earlier stage. IOP may be measured using contact, or non-contact tonometry. The IOP provides invaluable confirmatory evidence of suspected primary open-angle glaucoma, and is an essential diagnostic test to detect cases of angleclosure glaucoma and the secondary glaucomas. The monitoring process uses the same clinical measurements as the diagnostic stage, but the emphasis is now on the most efficient use of the data to decide if the patient is either stable on the chosen treatment, or deteriorating in spite of therapy. This clinical impression may need to be modified in the (often long) period of followup, and a diagnostic decision may be required in the case of glaucoma suspects who ÔconvertÕ to glaucoma during monitoring. Monitoring the progress of a patient, who has been diagnosed as suffering from glaucoma, requires serial measurement of the IOP, as well as the VF and optic disc appearance. IOP is straightforward to measure, but is inadequate as the only measure of a patientÕs response to treatment: the recent concept of Ôtarget pressureÕ recognises the fact that the actual magnitude of IOP lowering required to arrest visual loss in any individual patient is not constant, and cannot be precisely determined Ôin advanceÕ. Whether the patient can be well managed with modest medical treatment, or whether aggressive surgical treatment will be required can only be determined by careful follow-up of the visual field and, ideally, the optic disc appearance. There are technical reasons why follow-up of early glaucoma is ideally performed with emphasis on the optic disc, and advanced glaucoma using the VF. Monitoring of patients with signs at the optic disc, or VFs which are not unequivocally

The College of Optometrists has allocated this article 2 CE credits. There are 12 MCQs with a pass mark of 66%.

glaucomatous, or with elevated IOP alone (glaucoma suspects) will involve optic disc imaging and, perhaps, one of the more recently described psychophysical tests of early damage. In this situation, development of unequivocal evidence of glaucomatous damage will imply progression of disease. A diagnosis of glaucoma, or Ôhigh-riskÕ glaucoma suspect status (i.e. probable early glaucoma) will lead to a clinical decision to treat elevated IOP (or possibly impaired ocular blood flow in normal tension glaucoma). Later evidence of disease progression in spite of apparently adequate IOP control may lead to a decision to apply more aggressive treatment in an effort to halt deterioration. These decisions will be tempered by the patientÕs own wishes, age, general health, and careful consideration of any co-existing ocular disease.

1) Diagnosis
a) Structural signs of glaucoma (optic disc/RNFL) Accurate diagnosis of a glaucomatous disc requires an understanding of the normal disc size and shape. Recent work by J. Jonas (1993) has greatly improved understanding of the normal disc configuration. i) Disc size and cup/disc ratio The optic nerve head is the conduit for approximately 1.2 million axons which are the central projections of the retinal ganglion cells. The damaging effect of elevated IOP, and possibly, impaired blood flow, which cause the signs of glaucoma, are thought to occur at the level of the optic nerve head. The damage results in loss of axons, which correlates with a reduction of the neuroretinal rim (area enclosed by the perimeter of the optic disc and the rim of the optic disc cup) resulting in increased cupping of the optic disc. Recent work has confirmed a large Continued overleaf È 27

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normal variation in the size of the scleral orifice and, hence, optic disc, which these fibres pass through. Patients with a large diameter optic disc, therefore, tend to have a larger cup, whereas those with a smaller disc have a small cup (or sometimes no cup), although the total number of axons is similar. Knowledge of this normal variation is useful when interpreting the optic disc appearance. When examining a patient, an attempt to measure the size of the optic disc should be made. The most accurate method is the use of the slit lamp biomicroscope: a narrow vertical slit beam is projected onto the disc and the length adjusted until it is equivalent to the vertical diameter of the disc (Figure 1): the diameter of the disc can be calculated by Ôreading offÕ the slit beam length from the dial on the slit lamp, and multiplying this figure by the correction factor for the type of indirect ophthalmoscopic lens used (1.1 if 78D, 1.4 for 90D). It is apparent that when the disc size is taken into account, the familiar cup/disc (c/d) ratio Ôcut offÕ for abnormality of 0.5 is inadequate: specifically, if the disc is small (<1.3mm), a c/d ratio of 0.5 may be pathological, equally, if the disc is large (>1.9mm), 0.6 may be normal. Figure 2 shows the mean and upper range of normality (normal mean + 95% confidence interval) of c/d ratio for a range of disc sizes. ii) Disc shape The normal disc shape is a slight vertical oval. The normal cup shape is a slight horizontal oval. If the neuroretinal rim is divided into quadrants, the relative thickness of the normal neuroretinal rim conforms to a pattern which is easily remembered using the ÔISNTÕ rule: ÔIÕ stands for inferior rim, which is normally the thickest, followed by superior, then nasal, with the temporal rim usually the thinnest (J. Jonas). This is shown graphically in Figure 3. If this rule is applied, departures from normal are easily spotted. In particular, abnormal thinning (or ÔnotchingÕ) of the superior, and especially the inferior rims are very suggestive of glaucomatous damage. This change in the shape of the neuroretinal rim is possibly the most useful, and specific, disc sign of glaucoma. iii) Other disc signs The presence of a disc haemorrhage is very suspicious of glaucoma: commonly, these occur adjacent to a area of thinning, or ÔnotchingÕ of the neuroretinal rim (Figure 4). The apparent undermining of a circumpapillary disc vessel is also suspicious, though these signs are not as useful as the disc c/d ratio and rim shape signs described above, as they are rather rarely seen as the sole sign of disease. Many glaucomatous discs never show haemorrhages, and only approximately 40% of normals have a circumpapillary disc vessel. iv) RNFL changes If a focal, wedge-shaped RNFL defect is present, it is always abnormal, and is usually a sign of glaucoma (Figure 4). Such clear signs are, however, rare, and will

Figure 1 Simulated slit lamp biomicroscopic view of technique of optic disc diameter measurement

Figure 2 Nomogram summarising work by J. Jonas on the relationship between disc diameter and cup/disc ratio. The mean and upper 95% confidence limits for normality are shown

Figure 3 Schematic illustration of the ‘ISNT’ rule of J. Jonas. The typical vertical oval shape of the disc, and the horizontal oval of the cup are shown

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Figure 4 Optic disc showing several signs of glaucomatous damage: 1) Increased cup/disc ratio of >0.8 2) Thinning of both the inferior and superior neuroretinal rims 3) Disc haemorrhage adjacent to the inferior ‘notch’ 4) Focal,‘wedge-shaped’ RNFL defect extending from the inferior disc edge

be difficult to visualise in the presence of even quite early cataract. Diffuse atrophy of the RNFL is present in all cases of advanced glaucoma, but is a difficult sign to recognise. b) Functional signs of glaucoma (perimetry and other psychophysical tests) i) The visual field in glaucoma Ideally, the VF will be measured using an automated static perimeter which performs a white-on-white (W-W) threshold estimation at each point. Simple suprathreshold testing strategies demonstrate lower sensitivity in detecting glaucomatous loss, and are not commonly used in a hospital setting. The earliest signs of glaucomatous visual field loss may simply be an increase in the intra and inter test fluctuation in light sensitivity. This may manifest as an increase in a global index of variability (short term fluctuation and/or false negative responses when using a Humphrey field analyser, HFA, San Leandro CA). The plotted field may show a field defect in, say, the nasal step area which fluctuates in depth between patient visits, and may seem to ÔdisappearÕ on some tests, only to reappear at the same location at a later visit; if the disease is progressive, the defect will become permanent (Figure 5). There are many causes of artefactual visual field loss: an important clinical skill is to recognise when these artefacts are likely eg if the patient is known to have cataract, diffuse loss of sensitivity may be anticipated. Likewise, a ÔdroopyÕ upper lid may cause a superior field defect if not taped up. Classification of the different stages of glaucomatous field loss in progressive disease was described by Althorn and Harms (1967). Stages: 1) Isolated paracentral scotomata or ÔbaringÕ of blindspot 2) Arcuate scotomata 3) Arcuate scotoma with peripheral breakthrough 4) Extensive loss but sparing of central field (also temporal island) 5) Total field loss This classification is still useful, and the tendency for early defects to appear in the paracentral field has been confirmed by other workers. ii) Other psychophysical tests It is known that there is loss of ganglion cells in glaucoma before the appearance of W-W VF defects (Quigley et al, 1981).

Knowledge of the probable selective nature of early glaucomatous damage (Quigley et al, 1987) has prompted investigators to explore other measures of visual function which may be more sensitive to early disturbances than conventional luminance sensitivity perimetry. Blue on yellow perimetry (short wavelength perimetry) Blue ganglion cells are relatively sparsely distributed (1% of total) throughout the retina, being absent at the foveola: losses due to early glaucoma may be detected earlier than in visual pathways which exhibit greater redundancy (Johnson, 1993). Blue on yellow perimetry (B-Y) has been described using a modified Humphrey perimeter with a yellow background and blue stimuli (Johnson, 1993). Recent work has demonstrated: a) scotomas detected using B-Y perimetry are more extensive and ÔdeeperÕ than conventional W-W perimetry (Johnson et al, 1993 and Wild et al, 1995); and b) blue on yellow defects precede the later development of W-W defects by several years in glaucoma suspects. A disadvantage of short-wavelength perimetry is the effect of ocular transmission loss in the ageing lens which may be indistinguishable from early glaucomatous losses. Another potential disadvantage of B-Y perimetry is increased test variability which may result in less sensitive detection of visual field progression (Wild et al, 1995). Motion and frequency doubling perimetry Recent work has identified a group of ocular hypertensives with abnormally elevated motion thresholds in the presence of normal automated W-W fields. Furthermore, abnormal motion sensitivity may precede the development of conventional VF loss by

Figure 5 Two successive visual fields from a patient developing early glaucomatous inferior arcuate scotomata. This patient was originally a glaucoma suspect (ocular hypertension). Appearance of this field defect prompted treatment of elevated IOP

several years. Motion sensitivity is an example of a hyperacuity measurement and, as such, is relatively resistant to the confounding effects of media opacity, refractive blur, and pupil size (Fitzke et al, 1988). There is a significant correlation between motion sensitivity and optic disc neuroretinal rim area in glaucoma patients and suspects (Ruben et al, 1994). Frequency doubling perimetry (FDP) is a recently described psychophysical test which
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disc and visual function measurements are used only to establish initial diagnosis. Since the long-term aim in glaucoma treatment is to halt progressive visual loss rather than monitor the height of the intraocular pressure, it has been suggested that IOP should be considered as a surrogate outcome measure and that optic disc change and/or visual field survival is the Ôgold standardÕ for treatment effect. Unfortunately, a thorough review of published trials comparing treatment effect in glaucoma has shown that visual field and/or optic disc outcome is rarely evaluated, and even use of the surrogate IOP outcome is limited by the small numbers of studied patients, inadequate follow-up and widely varying criteria for ÔsuccessÕ and ÔfailureÕ of the treatment modality studied (Rossetti and Orsalesi, 1993). b) Methods of monitoring optic disc change As detailed above, the important glaucomatous optic disc signs are an abnormal shape to the neuroretinal rim (especially thinning of the inferior rim), and an abnormally large c/d ratio (ideally corrected for optic disc size). As glaucoma progresses, the size and shape of the cup changes. The RNFL also becomes more atrophic, but sensitive and reproducible techniques for imaging the RNFL, and demonstrating subtle changes over time are still at the research stage: retinal nerve fibre polarimetry does, however, seem a promising method. Currently, most clinicians concentrate on the optic disc in an attempt to diagnose disease progression. The most commonly used method of recording the appearance of the disc at each clinic visit is still a drawing in the notes: typically including a visual estimate of the c/d ratio, increasingly combined with a measurement of the disc size (using the slit-lamp biomicroscopic method described above). This is certainly useful (especially if the drawings are made by the same clinician each visit) and has the added advantage of helping the clinician ÔorganiseÕ his impression of the disc by the discipline of having to complete a drawing. The method, unfortunately, has only limited usefulness as ÔintertestÕ variability and/or poor clinical agreement within, and between, clinicians is too high to allow the necessary accuracy in the detection of even quite marked disc change. Fundus photography greatly improves the accuracy of disc monitoring. Importantly, archiving of previous disc photos allows any clinician to easily compare the current disc appearance with previous clinic visits. A stereophotographic image pair provides a further improvement over a non-stereo disc image. This is because a clinician examining a stereoimage is more easily able to delineate where the cup/neuroretinal rim ÔedgeÕ lies. This advantage is especially important if planimetry of the disc is attempted: planimetry is a technique whereby the stereodisc image is used to allow precise measurement of the neuroretinal rim area. Planimetry is very time-consuming, and also requires skilled operators to produce reproducible results: it certainly allows the detection of subtle neuroretinal rim loss in progressive glaucoma, but is impractical in all but the most specialised units, and even then only in select groups of early glaucoma cases. It is important to be aware of the difficulties in diagnosing disc progression in the case of more advanced glaucomatous cupping (c/d ratio >0.8). This is because the neuroretinal rim area is now much smaller than in early disease, and is correspondingly closer to the magnitude of the variability or ÔnoiseÕ involved in the planimetry process itself: this reduced Ôsignal-to-noise ratioÕ makes detection of progression in advanced glaucoma more difficult. If formal planimetry is not performed, a sensitive qualitative technique for detecting disc change is flicker chronoscopy - two sequential images of the same disc are displayed in quick succession, and areas of the neuroretinal rim, which are dissimilar between the images, appear to ÔflickerÕ (or may demonstrate a ÔpseudostereoÕ effect, if the images are arranged so that one image is viewed with one eye, and the later image is viewed with the other eye). More recent developments in disc imaging include the use of digital fundus cameras. These offer the same advantages over simple disc drawings as photographic emulsion fundus cameras, especially if a stereodisc image is obtained: there are now systems to allow viewing of stereodisc images on VDU screens. Conventional planimetric techniques can be applied to digital images. Advantages include instant review of the recorded image, ease of archiving the images to allow straightforward comparison with previous images, and flicker chronoscopy can also be performed. Disadvantages include the lower resolution of digital images compared with emulsion; though this may may be less of a problem in a few years as imaging chip technology develops. The more sophisticated technology of the confocal scanning laser ophthalmoscope (SLO) does allow measurement of disc topography,

has close similarities to motion sensitivity testing, i.e. it may test the visual pathway which suffers early damage in glaucoma. FDP is a rapid test which promises to fulfil a useful role as a convenient, and sensitive, visual screening test in the primary eyecare setting (Johnson et al, 1996). Experience with this new test is, however, currently limited.

2) Monitoring glaucoma over time
a) Background (and limitations of IOP monitoring alone) In hospital-based clinical practice, detection of glaucomatous damage using optic disc imaging and conventional perimetry, or one of the more recently described psychophysical tests, helps to establish the diagnosis of glaucoma. At diagnosis, the disease may be more, or less advanced depending on the time elapsed before presentation. Following diagnosis, the patient will require therapy and ideally knowledge of his prognosis with (or without) the recommended treatment. Quantification of change over time of clinical measurements in glaucoma is therefore essential: i) to assess response to treatment (of individuals, as well as cohorts in research); ii) to allow estimation of risk/benefit ratio of any proposed changes in treatment; and iii) to provide prognostic information. Much work has been directed at assessing the effects of treatment of raised IOP in glaucoma. IOP elevated above the population threshold for abnormality (population mean plus 2 standard deviations: 21mmHg) is considered the most important risk factor for the development and subsequent progression of glaucoma. IOP can be reduced by medical and/or surgical intervention including laser. Knowledge of IOP response to treatment is important to allow comparison between different treatments, and measurement of IOP is technically straightforward and reproducible. However, it has been shown that even a large IOP fall on treatment does not prevent progression of glaucomatous damage in some subjects, whereas others may tolerate high levels of IOP, for long periods, without apparent injury (Chauhan et al, 1992). Many studies investigating the long-term effects of treatment in glaucoma have placed much emphasis on the size and persistence of the IOP lowering effect; optic 30

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combined with the convenience of a digital imaging system. Furthermore, recent research has shown that the SLO is a sensitive detector of changes in disc topography in ocular hypertensives prior to the development of visual field defects, i.e. ÔconversionÕ to glaucoma. Disadvantages include a rather slow image acquisition time and, importantly, the SLO is expensive and its use is currently restricted to large, specialist units. c) Methods of monitoring visual field change As discussed above, imaging of the optic disc has an important and increasing role in the monitoring of early glaucoma (and glaucoma suspects). This is because the neuroretinal rim area is easier to measure in early glaucoma and the VF changes are minimal, or absent, at this stage. However, in moderate and advanced disease, VF measurement is rapidly becoming the accepted Ôgold standardÕ outcome measure, not least because it is the measurement of most immediate concern to the glaucoma sufferer. The development of automated perimetry has allowed more objective, reproducible measurements of the field to be made, though the problem of fluctuation between successive fields remains. Detection of progression - from a series of automated VFs - has traditionally relied on the subjective opinion of the clinician inspecting a series of VF ÔprintoutsÕ. There is evidence that this approach may lack sensitivity, and there is poor agreement between clinicians on what constitutes progression even when examining the same field series. Moreover, the critical measure of progression is the rate of sensitivity loss, which cannot be easily deduced by subjective inspection of the VF printouts. Several approaches to a more objective method of measuring the rate of visual field progression have been reported recently. One approach, Ôpointwise linear regressionÕ, is a technique used in the PROGRESSOR software (Fitzke et al, 1996). The program automatically calculates both the rate of sensitivity decay (dB/year) and the statistical significance of this decay. This information is then summarised in colour-coded VDU display which allows the clinician to determine whether decay is occurring, how rapidly (in dB/year), and whether the sites of decay within the visual field are consistent with glaucomatous loss (and do not represent developing cataract, for example). A series

Figure 6 PROGRESSOR software analysis of 13 Humphrey visual fields from the left eye of a patient with progressive POAG. This software demonstrates graphically the deterioration of visual fields by increasing bar length at the affected locations in the inferior nasal step area, as well as the development of a red colour code. This indicates a statistically significant rate of sensitivity loss

of Humphrey automated perimetry tests are shown, together with the PROGRESSOR program analysis in Figure 6. The precise role of the more recently described tests of very early visual loss, i.e. blue on yellow, and motion perimetry (including frequency doubling perimetry) is still uncertain. Clearly, the development of a scotoma detectable by conventional W-W perimetry in an area of field previously normal to W-W, but previously abnormal to one of the more sensitive visual function tests, indicates progressive disease, and would suggest the need for more aggressive treatment.

3) Use of clinical data in decision making, and a hospital-based approach to therapy
The preceding discussion outlined the uses and limitations of the three important clinical measurements, namely IOP, disc and visual field. Careful examination of the anterior segment (including gonioscopy) is also very important and, at the diagnostic stage, will often be definitive in confirmation of angle closure glaucoma, and the various secondary glaucomas. It is worth noting here that in the case of angle closure especially, the history of intermittent visual blurring, sometimes associated with dull ocular pain, which resolves spontaneously on going to sleep (and associated miosis) will itself be a very useful diagnostic clue. This history (which describes

self-limiting episodes of pupil block causing angle closure) combined with a very narrow, or closed drainage angle on gonioscopy, especially if associated with an elevated IOP, will, on referral, lead directly to treatment with Nd YAG laser iridotomies in both eyes. In the more insidious chronic, or ÔcreepingÕ angle closure, this history will not be forthcoming, and the patient will often be asymptomatic until visual loss becomes advanced ˆ la POAG. Patients who are referred to the hospital eye clinic as glaucoma suspects will undergo assessment of their IOP , optic disc and visual field. The diagnostic process will (as described above) determine if the patient is treated, simply observed at regular intervals to check for evidence of developing glaucoma, or discharged if no risk factors for glaucoma are found. This ‘triage’ of referrals can be best summarised with a few examples (though these are not exhaustive):

Clinical findings
a) Open drainage angle, normal optic disc appearance, intact RNFL, normal VF and IOP <21mmHg. No other risk factors, e.g. family history (Fhx) of glaucoma. No other ocular disease. Action: Patient discharged, informed that 31

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treatment would be added. More aggressive management (surgical) would follow if significant VF loss developed, especially if the patient was young. d) Open drainage angle, discs c/d ratio 0.9, glaucomatous visual field loss both eyes, IOPs 30mmHg on presentation. Action: This is a case of advanced POAG. IOP needs to be reduced urgently. Usually an attempt will be made to treat medically, but with such advanced disc and field damage, the IOP should be as low as possible. Many clinicians would proceed to drainage surgery at an early stage, if medical treatment proved inadequate. If the patient was very elderly, argon laser trabeculoplasty (ALTP) could be performed: this would not, however, be very useful if the patient was young, as the majority of ALTPs will have failed after only five years. e) Open drainage angles, discs c/d ratio 0.9, glaucomatous field loss, IOPs 18mmHg. Action: This is probably a case of Ônormal tensionÕ glaucoma (NTG). It would be wise to exclude IOP ÔspikesÕ by performing 12 or 24 hour IOP monitoring (often as an inpatient). If the IOP spikes above 21mmHg, many clinicians would treat the patient as POAG though, obviously, the target pressure would be low; perhaps <12mmHg. If the IOP is consistently low, the management of these patients is controversial. Some clinicians believe that the principal pathology is still the IOP, and treat these patients with medical hypotensive (and sometimes surgical) treatment. Other surgeons prefer to leave these patients untreated, and simply monitor the optic disc and visual field very carefully for signs of progression; drainage surgery is offered only if deterioration is detected, especially if there is symptomatic VF progression. There is some justification for this approach as only about 1/3 of a group of NTG patients actually progressed, when observed for five years, and small trials of drainage surgery in NTG have shown a beneficial effect. There is another view that NTG is mainly caused by poor ocular blood flow, and that IOP has a very minor role. Some research has shown impaired circulation to the eye in NTG cases, and there have been trials of vasoactive drugs in an attempt to arrest visual loss. The clinical implications of these findings are presently unclear. The ideal instrumentation for the measurement of ocular blood flow is also the subject of current research work.

their risk of developing glaucoma in the future is small, and no higher than the general population. Advised, nonetheless, to attend optometrist at least every two years for regular eye check. b) As above, but borderline elevated IOP of say 24mmHg. Also positive Fhx of glaucoma. Action: Somewhat higher risk of developing POAG - most clinicians would arrange infrequent (perhaps annual) review, with special attention to the optic disc appearance (and RNFL). This patient would ideally have stereodisc images recorded at each visit. If the IOP increased to >268mmHg or above, especially if accompanied by an increase in the c/d ratio, or perhaps the appearance of a disc haemorrhage, treatment with a topical hypotensive would be started. Review would become more frequent, perhaps every six to eight months. If the IOP was 22mmHg, with no Fhx, and the disc remained normal, many clinicians would discharge the patient, but suggest annual visits to the optometrist for examination. c) IOP >30mmHg, drainage angle open, no other risk factors. Action: Most clinicians would commence hypotensive treatment in this case, as there is a significant risk of progression to POAG with such a high IOP. There is also an increased risk of a central vein occlusion. The patient would be reviewed within a few weeks to check for treatment effect. If satisfactory, review would be perhaps biannual. Monitoring of disc and VF would be performed (as above) - any evidence of glaucomatous damage would prompt a review of the level of IOP attained with treatment. If the IOP was much higher than perhaps 16mmHg, additional medical

Summary
This article has summarised current hospital techniques used in glaucoma diagnosis and monitoring. The overriding importance of careful follow-up of the optic disc and the visual field is stressed. These clinical measures are the most important determinants of whether the treatment of elevated IOP is considered adequate in each individual patient. The impact of the patientÕs general condition is touched on: especially important is understanding that the primary aim of glaucoma therapy is to preserve the patientÕs vision during their lifetime, whilst at the same time not damaging the patientÕs quality of life with any complications of treatment. This pragmatic approach hopefully avoids the overly aggressive treatment of mild glaucoma in very elderly patients, but equally avoids undertreatment of young patients with moderate or advanced disease, whose untreated risk of vision impairment is high. The article does not discuss specific medication in detail, and the rarer secondary glaucomas have not been discussed. This information is available elsewhere.

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Multiple Choice Questions
Please note that for each question, there is only ONE correct answer
1) Which one of the following statements regarding the assessment of the optic disc is correct? a) A cup/disc ratio of 0.7 always indicates glaucoma b) A disc with a diameter of 2.5mm would be described as a small disc c) Glaucoma may be present in an eye with a cup/disc ratio of 0.3 d) Large diameter optic discs tend to have small cups 5) Which one of the following statements regarding visual field defects (using conventional perimetry) in glaucoma is correct? a) Defects are typically very reproducible between visits b) Defects usually cause early loss of visual acuity c) Defects may be predated by abnormalities of motion sensitivity d) Defects usually occur before signs of damage at the optic disc 9) Which one of the following statements regarding the confocal scanning laser ophthalmoscope is incorrect? a) It allows measurement of disc topography using a digital imaging system b) It is a sensitive indicator of disc topography changes c) It is useful for monitoring ocular hypertensives d) It requires photographic emulsion to record images

2) Which one of the following is not usually a sign of glaucoma? a) Tortuous retinal blood vessels b) Thinning of the inferior neuroretinal rim c) Undermining of a circumpapillary blood vessel d) Optic disc (peripapillary) haemorrhage

3) Which one of the following statements regarding the diagnosis and management of glaucoma is correct? a) The IOP is the best clinical measure to diagnose and monitor glaucoma b) A patient with an IOP of 22mm Hg, and a normal visual field is likely to be treated with urgent drainage surgery c) Young patients with glaucoma are at higher risk of visual impairment if undertreated d) Examination of the anterior segment of the eye is unhelpful in suspected angle closure glaucoma

6) Which of the following statements regarding normal tension glaucoma (NTG) is correct? a) NTG may be caused by poor blood flow to the eye b) NTG is monitored using only measurements of the IOP c) NTG does not cause cupping of the optic disc d) NTG is never bilateral

10) Which one of the following statements regarding the visual field test is correct? a) It is most sensitive if a suprathreshold strategy is used b) It is useful to monitor very advanced glaucoma c) It is usually the most sensitive method to detect early glaucoma damage d) It is not affected by cataract

7) Which one of the following statements is the most likely indicator of early POAG? a) Patients complaining of a transient loss of vision b) Patients complaining of intermittent eye pain c) A macular haemorrhage d) Increased variability when testing visual fields

11) Which one of the following statements regarding retinal nerve fibre layer (RNFL) defects is correct? a) RNFL defects are easy to visualise b) RNFL defects tend to be circular c) Atrophy of the RNFL is present in all cases of advanced glaucoma d) RNFL defects may be present in normal patients 12) Which one of the following statements regarding blue on yellow (B-Y) perimetry is incorrect? a) Scotomas detected using B-Y perimetry are more extensive and deeper than W-W perimetry b) B-Y defects precede W-W defects c) B-Y perimetry may be affected by ocular transmission loss in the ageing lens d) Early research has shown that there is little test variability

4) The monitoring of glaucoma is ideally based upon which one of the following? a) IOP recording only b) Optic disc drawings performed by a different clinician at each clinic visit c) Cup/disc ratios only d) Optic disc imaging and visual field measurement to determine the patient’s target IOP

8) When estimating disc size using an indirect ophthalmoscopic lens with the slit lamp biomicroscope, what is the correction factor for a 90D lens? a) 1.1 b) 0.8 c) 1.4 d) 2.2

An answer return form is included in this issue. It should be completed and returned to:

Model answers will be published in our February 12, 1999 issue.

CPD Initiatives (CDM1), Optometry Today, Victoria House, 178-180 Fleet Road, Fleet, Hampshire, GU13 8DA, by February 10, 1999.

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Multiple choice answers
Differential diagnosis and management of red eye
Here are the correct answers to Part 12 of Module 3 on Anterior Segment Eye Disease, which appeared on December 4, 1998.
1. Which one of the following statements is true? Alkali burns of the eye: a. should only be irrigated with water which has been boiled and cooled. b. are not serious if the conjunctiva appears very white. c. are less serious than those caused by an acid. d. should be immediately irrigated with water. d is correct It is imperative to irrigate immediately an eye, which has received a chemical insult. Extensive damage can occur while looking for a sterile solutions - tap water is a suitable choice. 2. Which one of the following statements is true? When a foreign body sensation is present and fine linear abrasions are visible on the cornea: a. it is mandatory to evert the upper lid. b. intraocular foreign body should be suspected. c. recurrent erosion syndrome should be suspected. d. herpes keratitis is the likely cause. a is correct Linear abrasions are due to the presence of foreign bodies embedded on the palpebral conjunctiva which scratch the corneal epithelium during lid and eye movement. Intraocular foreign bodies will not do this. 3. Which one of the following statements is true? Faint rust rings present in the cornea after removal of a metal foreign body: a. may later cause retinal abnormalities. b. produce intraocular inflammation. c. are unlikely to cause further problems. d. may spread over large areas and prove unsightly. c is correct Faint rust rings present in the cornea after removal of a metal foreign body are unlikely to cause further problems. Iron particles can continue to oxidise and form rust after being deposited on the corneal surface. Although large amounts of pigment can be toxic to the epithelium, a small amount is generally well tolerated. Visually significant scarring can be associated with overaggressive attempts at removal. 4. Which one of the following statements is true? Infectious keratitis: a. is not serious. b. is rare in patients with ocular surface disorders. c. may occur if contact lenses are cleaned in tap water. d. is distinguished by the presence of ischemia. c is correct Infectious keratitis may occur if contact lenses are cleaned in tap water. Tap water, while appropriate for immediate care in toxic chemical injuries, is entirely unacceptable for cleaning or storage of contact lenses. Microbial pathogens adhere to the surface of lenses and can lead to devastating corneal infections. This must be emphasised when dispensing lenses. Proper hygiene including hand-washing must also be stressed. Ocular surface disorders predispose to infectious keratitis. 5. Which one of the following statements is true? Corneal flash burns: a. are associated with minimal discomfort. b. result in partial thickness tissue loss with subsequent severe scarring. c. require treatment with intensive topical steroids. d. may be prevented during welding by wearing appropriate safety goggles. d is correct Corneal flash burns may be prevented during welding by wearing appropriate safety goggles. Corneal flash burns are associated with marked discomfort and result in punctate epithelial keratitis which resolves without sequelae. This condition is treated with lubrication, mydriasis and analgesia. 6. Which one of the following statements is true? Anterior uveitis: a. often has redness which increases towards the conjunctival fornices. b. symptoms include diplopia. c. should be treated with prophylactic antibiotics. d. usually is associated with low intraocular pressure initially. d is correct Anterior uveitis is usually associated with low intraocular pressure initially. Inflammation of the ciliary body leads to decreased aqueous production with decreased intraocular pressures. Infection plays no part in true acute anterior uveitis, which is an inflammatory disease antibiotics are not indicated. Symptoms include blurred vision and photobia.

7. Which one of the following is not indicative of acute angle closure glaucoma? a. Abdominal pain and vomiting. b. Mid-dilated unreactive pupils. c. An intraocular pressure around 20mmHg. d. Iris bombe and an oedematous cornea.

c is correct Acute angle-closure glaucoma classically presents with a painful red eye, complaints of reduced vision and seeing haloes around lights. Sometimes, patients have seemingly unrelated symptoms such as headache, abdominal pain, nausea and vomiting. Examination may show an oedematous or hazy cornea, mid-dilated unreactive pupil, iris bombe and shallow anterior chamber. Intraocular pressure is often very high, measuring 50mm Hg or more. Acute angle closure requires immediate referral in order to minimise damage to the optic nerve.

8. Which one of the following statements is true? Orbital cellulitis: a. is always associated with acute angle closure glaucoma. b. almost never needs more than oral antibiotic treatment. c. may present with proptosis and reduced ocular movements. d. usually has a viral aetiology.

c is correct Orbital cellulitis may present with proptosis and reduced ocular movements. It frequently occurs in children as an extension of sinusitis. It requires treatment with intravenous antibiotics and usually has a bacterial aetiology.

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JANUARY 15 • 1998 OPTOMETRY TODAY


The College of Optometrists

Clinical decision making in glaucoma

DISTANCE LEARNING MODULE 1 PART 1

Multiple choice answers
Differential diagnosis and management of red eye
Here are the correct answers to Part 12 of Module 3 on Anterior Segment Eye Disease, which appeared on December 4, 1998.
9) Which one of the following statements is true? Pupil distortion a. is a sign of acute angle closure glaucoma. b. never follows formation of posterior synechiae. c. may be associated with penetrating ocular trauma. d. is a frequent complication of infectious keratitis. c is correct Pupil distortion may be associated with penetrating ocular trauma. Mid-dilated and unreactive pupil is a sign of acute angle closure glaucoma. Pupil distortion may follow formation of posterior synechiae. Pupil distortion is not usually a complication of infectious keratitis. 10. Which one of the following statements regarding scleritis is false? a. It may be associated with rheumatoid arthritis. b. It may be associated with pain. c. Treatment may involve the use of non-steroidal antiinflammatory agents. d. The redness blanches with phenylphrine. d is correct Scleritis is a more serious inflammation occurring in an older age group and may be associated with systemic disease such as rheumatoid arthritis or infections such as herpes zoster. Pain is often a prominent symptom and vision may be reduced if the inflammation occurs posteriorly because the retina or optic nerve may be secondarily involved. The redness is more violaceous than that of episcleritis and does not blanch with topical phenylephrine. Because of the associated pain and potential for complications, including those of systemic disease, these patients should be referred for assessment. Treatment will usually involve oral nonsteroidal anti-inflammatory agents or steroid therapy. 11. Which one of the following statements regarding subconjunctival haemorrhages is false? a. They are frequenlty spontaneous. b. They may be associated with hypertension. c. They will resolve within 1-2 days. d. If haemorrhages are recurrent, a clotting disorder may be suspected. c is correct Subconjunctival haemorrhages are frequently spontaneous and the patient will notice a localised area of bright red discolouration. Patients who use topical medication are particularly at risk through self-induced trauma. Patients with isolated unilateral haemorrhage require nothing more than reassurance although occasionally hypertension may be related. Clotting disorders should be excluded if there are recurrent episodes. The haemorrhage will fade over the course of 7-10 days. Note that some viral infections can cause diffuse or scattered subconjunctival haemorrhages. These are often bilateral and associated with a watery discharge. Diffuse bilateral confluent haemorrhage needs referral as head injury should be ruled out.

JANUARY 15 • 1998 OPTOMETRY TODAY

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