Teleglaucoma: ready to go?

Telemedicine technologies and services allow today's ophthalmic clinicians to remotely diagnose, manage and monitor several ophthalmic conditions from a distance. But is this the case for glaucomas? There has been a proliferation of telemedicine friendly devices in recent years that improves the capabilities of the clinician in managing glaucomas. The existing instruments still need to align themselves with accepted industry standards. There are successful programmes running in several areas of the world. The safety and efficacy of these programmes needs further exploration. The inability of a single device or test to diagnose glaucomas satisfactorily has also hampered progress in remotely diagnosing these conditions. There is, however, significant potential for telemedicine-friendly devices to remotely monitor the progress of glaucoma and, thereby, reduce some of the workload on an overstretched health service.

The African Programme for Onchocerciasis Control: impact on onchocercal skin disease.

OBJECTIVES: To assess the long-term impact of the African Programme for Onchocerciasis Control on itching and onchocercal skin disease (OSD). METHODS: Seven study sites in Cameroon, Sudan, Nigeria and Uganda participated. Two cross-sectional surveys were conducted of communities meso- and hyper-endemic for onchocerciasis before and after 5 or 6 years of community-directed treatment with ivermectin (CDTI). Individuals were asked about any general health symptoms including itching and underwent full cutaneous examinations. Onchocercal skin lesions were documented according to a standard classification. RESULTS: Five thousand one hundred and ninety three people were examined in phase I and 5,180 people in phase II. The presence of onchocercal nodules was a strongly significant (P < 0·001) risk factor for all forms of onchocercal skin disease: APOD (OR 1·66); CPOD (OR 2·84); LOD (OR 2·68); reactive skin lesions (OR 2·38) and depigmentation (OR 3·36). The effect of community-directed treatment with ivermectin was profound. At phase II, there were significant (P < 0·001) reductions in the odds of itching (OR 0·32), APOD (OR 0·28); CPOD (OR 0·34); reactive skin lesions (OR 0·33); depigmentation (OR 0·31) and nodules (OR 0·37). Reduction in the odds of LOD was also significant (OR 0.54, P < 0.03). CONCLUSIONS: This first multi-country report of the long-term impact of CDTI reveals a substantial reduction in itching and OSD. APOC operations are having a major effect in improving skin health in poor rural populations in Africa.

Poor public health knowledge about glaucoma: fact or fiction?

PURPOSE: To document public awareness and knowledge of glaucoma. PATIENTS AND METHODS: The study used health knowledge questionnaires. (a) A short, structured telephone interview was performed with a nationally representative sample of 1009 people. (b) A more detailed questionnaire was administered in two contrasting regions by telephone (500 interviews from the Isle of Wight and 226 interviews from Ealing) or face to face (300 interviews from Ealing). RESULTS: Between 71 and 93% of those interviewed by telephone reported having heard of glaucoma, compared with only 23% of those interviewed face to face in Ealing. Of those who reported having heard of glaucoma, over 80% had at least some knowledge about the disease. CONCLUSION: This is the first study of public awareness of glaucoma across the UK. We found a relatively high level of awareness and knowledge of glaucoma in the general UK population, but identified at least one pocket of poor knowledge in a specific sub-population.

Combined cataract and trabeculectomy surgery for advanced glaucoma in East Africa; visual and intra-ocular pressure outcomes.

AIM: To investigate visual and intra-ocular pressure (IOP) outcomes of combined cataract and glaucoma surgery at a high-volume centre in East Africa carried out over a 1-year period (2006). METHODS: A retrospective analysis of patient records. RESULTS: A total of 163 patients were identified. Mean age was 67 years (SD 11, range 21-86 years) and 113 (69%) were men. Presenting visual acuity in the operated eye was 6/60 or worse in 135/163 (93%) and was <3/60 in 76 of 163 (47%) patients. Mean presenting IOP was 28 mm Hg (SD 9, range 12-60). Pre-operative cup disc ratios were 0.8 or worse in 131 of 163 (85%) patients. Phacotrabeculectomy (PT) was carried out in 130 (80%) cases, small incision cataract surgery trabeculectomy (SICST) in 10 (6.1%) cases, and extra-capsular cataract extraction trabeculectomy (ECCET) in 23 (14.1%) cases. In all, 107 (66%) attended for follow-up (mean interval 104 days, range: 6-390 years, SD 88) and at follow-up 75 (70%) patients had improved visual acuity pre-operatively. Pre-operative cup disc ratio of 0.9 or greater predicted failure to improve VA at follow-up (OR 4.0 95% confidence interval (CI) 1.30-12.1). Fifty-nine (62% (95%CI 52-71%)) patients had follow-up IOPs of 6-15 mm Hg and 82 (85% (95% CI 78-92%)) had follow-up IOPs of 6-20 mm Hg. CONCLUSION: Combined surgery produces visual benefit for most patients with similar pressure control to pure trabeculectomy and is therefore a useful option in practises where follow-up may be doubtful.

Can a public health intervention improve awareness and health-seeking behaviour for glaucoma?

AIM: To investigate whether a public education campaign can increase awareness and change help-seeking behaviour with respect to ocular health in an Indian population. METHODS: A health knowledge questionnaire was used investigating and assessing the health campaign. The health campaign comprised four components: (1) television, (2) local press, (3) local radio and (4) places of worship. The target population were Indian residents in Southall, Ealing aged 60+. The aim was to get people to go and have their eyes tested at their local optometric practice. Optometric practices within the borough of Ealing collected sight-test data for the study over 6 months before and after the advertising campaign. RESULTS: The repeat in-depth glaucoma knowledge questionnaire showed a significant increase in the number of people who had heard of glaucoma rising from 22% to 53%. Before intervention, most people had heard about glaucoma from their GP, friend or relative. After intervention, the majority (69%) had heard of glaucoma from the radio. CONCLUSION: This study has shown a significant increase in awareness from using different kinds of media and has shown radio to be the most effective in our target community. Although the campaign has raised awareness, this study has not shown a change in health-seeking behaviour.

Glaucoma detection in the community: does ongoing training of optometrists have a lasting effect?

PURPOSE: To establish whether the effect of improved glaucoma detection in the community suggested by an intervention study is maintained when intervention is extended to include all optometrists in the area. METHODS: Optometrists' in the Ealing, Hammersmith, and Hounslow area were invited to ongoing training sessions following completion of an intervention study. The number of optometrist initiated referrals to Ealing Hospital Eye Clinic (EHEC) for suspect glaucoma was assessed over a 12-month period. The positive predictive value (PPV) of those referrals was calculated and a historical comparison made with the results of the original study. RESULTS: A total of 376 new referrals for suspected glaucoma were assessed at EHEC during the 12-month period of data collection. This represents an increase in the number of referrals of 58% compared with an equivalent 12-month period during the initial intervention trial (376 vs. 238). The PPV was maintained at 0.45 (95% CI 0.41-0.51). CONCLUSION: The rising number of new referrals for glaucoma together with maintenance of the PPV suggests an impact on the number of new cases of glaucoma detected in the community. The increase in referral numbers was limited to glaucoma when compared with new referrals for cataract. This implies a targeted effect of the intervention in terms of glaucoma detection. We believe the next step is to perform the study in an alternative location to see if the effect is repeatable elsewhere. If proven to be the case, there is a coherent argument for widespread adoption of this strategy to improve glaucoma case finding.

Can a public health package on glaucoma reach its target population?

PURPOSE: A pilot study to assess how successful a newspaper advertisement and a radio interview about glaucoma are at reaching their target population. METHODS: The health intervention comprised two components: an interview on local radio and an advertisement in the local paper. Our target population were residents aged 45 years and above in either Southall (West London) or the Isle of Wight (IOW). A questionnaire was developed to be carried out pre- and post-intervention. The data from both locations pre and post were coded and cleaned. Tests of significance were carried out to assess statistical significance for differences in proportion, with tests for trend used where appropriate. All statistical analyses were carried out using Stata7. RESULTS: Overall, the proportion who had heard of glaucoma increased from 54% before the intervention to 60% after (chi(2) = 3.7, P = 0.055). The proportion who had heard of the disease increased by 13% (chi(2) = 8.76, P = 0.003) in Southall and by 8% (chi(2) = 5.02, P = 0.025) on the IOW. The proportion reporting seeing the advert increased significantly in both areas with greater effect in Southall. Those reporting hearing the radio interview only increased in Southall. On the IOW, females were more knowledgeable and responded more positively to the intervention. This differed in Southall where males tended to be the positive responders. Conclusion In both areas a significant effect on those having heard of glaucoma was found. This could be attributed to both the advert and interview in Southall but would appear to be attributable to the newspaper advertisement alone on the IOW.

Early postoperative trabeculectomy leakage: incidence, time course, severity, and impact on surgical outcome.

AIM: To establish the incidence, time course, and severity of conjunctival wound leakage following trabeculectomy, and also to establish whether early wound leakage adversely affects the ultimate outcome of the surgery. METHOD: A prospective, observational case series of sequential trabeculectomies performed in a single institution over a 12 month period. Datasets on 286 operations were analysed. A fornix based conjunctival flap was used in 254 cases and a limbus based conjunctival flap in 41 cases. At every postoperative visit trabeculectomies were assessed for four grades of leakage (none; mild; moderate; severe), and for success or failure at the 6 month follow up post surgery. Pressure was applied to the trabeculectomy bleb to record the maximum rates of leakage and improve kappa statistics. Study clinicians were validated with respect to their scoring of leaks before starting the study. RESULTS: 169 of the 286 trabeculectomies (59%) showed leakage at some stage postoperatively. 159 of 245 fornix based flaps (65%) leaked compared with 10 of 41 limbus based flaps (24%). Median time to leak was 3.5 (range 0-408) days. Median duration of leakage was 14 (range 2-457) days. 14 (5%) of trabeculectomies failed completely. A further 40 (14%) were a partial failure. In total, 23 of 117 (20%) without postoperative leaks partially or completely failed compared with 31 of 169 (18%) with leaks. Cross tabulation of partial and complete failure by leak shows no evidence of an adverse effect of leaking on the outcome (chi(2) = 1.81, p = 0.4). CONCLUSIONS: There is no evidence to support the hypothesis that early postoperative leakage of fornix based conjunctival flaps affects the outcome of trabeculectomy.

Evaluating clinical signs in trabeculectomized eyes.

AIM: To evaluate interobserver agreement for clinical signs in trabeculectomized eyes when examined face-to-face with slit-lamp biomicroscopy (SL) or by remote examination using telemedicine (real-time remote video imaging; TM). METHOD: A system for examining trabeculectomized eyes was devised and validated. A prospective randomized interobserver agreement study was then undertaken to compare standard SL biomicroscopy and TM. Remote examination was performed using a 384 kbps Sony 5100 videoconferencing system. Three ophthalmologists each examined 40 eyes of 40 patients, who had previously undergone trabeculectomy. In rotation, two examiners used SL biomicroscopy. The third examined the eye remotely by TM. Analysis was performed to determine the variability in clinical signs and the presence or absence of systematic bias between ophthalmologists and examination methods. RESULTS: High levels of agreement were observed for paired examinations by SL biomicroscopy (SL/SL) for bleb vascularity (score range 0-10) with no systematic bias. Paired examination by SL and TM (SL/TM) also showed good levels of agreement for bleb vascularity, although the spread of disagreement was wider (95% limits of agreement 2.57 vs 2.98 (P=0.054)). For anterior chamber depth, observers agreed within +/- 10% of anterior chamber depth for 68% of eyes (SL/SL) and 51% of eyes (SL/TM) (P=0.68). Agreement was 'good' for wall thickness (kappa=0.63 +/- 0.08), bleb height (kappa=0.67 +/- 0.1), and the existence of bleb leak (kappa=0.63 +/- 0.19), but poor for bleb morphology (kappa=0.26 +/- 0.12). For the SL/TM comparison, agreement was fair for wall thickness (kappa=0.39 +/- 0.13), poor for bleb height (kappa=0.17 +/- 0.12), good for bleb leak (kappa=0.56 +/- 0.19), and fair for bleb morphology (kappa=0.31 +/- 0.12). Microcysts were not reliably detected using either technique. CONCLUSION: SL biomicroscopy and TM telemedicine examination may permit reliable clinical assessment of trabeculectomized eyes. However, remote examination with TM is more limited with respect to assessing bleb height and bleb wall thickness. The assessment of bleb morphology and microcysts was unreliable with both instruments. We propose that TM examination of trabeculectomized eyes appears safe and appropriate in situations where face-to-face examination by an ophthalmologist is not practical.

Determining clinician satisfaction with telemedicine.

We compared two methods of assessing clinician satisfaction with telemedicine. Clinicians completed a self-administered questionnaire with a preference ranking scale and a discrete choice method. Sixty-three clinicians completed the questionnaire (a 78% response rate). The preference ranking method showed that clinicians ranked the level of skill of the other clinician as the most important (55%) attribute of a teleconsultation and the completeness of the history as the second most important attribute (42%). The discrete choice method showed that clinicians ranked completeness of the patient's history as the most important attribute and risk of receiving wrong advice as the second most important. The use of discrete choice preferences provides an alternative and more objective method for collecting data about preferences in telemedicine. However, its use is not simple and requires the participants to be engaged in person rather than sent a questionnaire by post.

Improving on ETDRS acuities: design and results for a computerised thresholding device.

AIMS: All visual acuity data are subject to test-retest variability (TRV). This measurement error obscures true clinical change and reduces the statistical power of clinical trials using acuity as a primary outcome measure. This study was designed to assess whether a computerised system can reduce TRV by taking repeated acuity measurements and averaging them. A computerised system (PC-test) was developed for this purpose and compared in terms of TRV with the current Gold Standard ETDRS logMAR chart. METHODS: A total of 19 subjects with a mean acuity of +0.16 logMAR (range +0.49 to -0.10 logMAR) were recruited. The performance of two computerised tests (one averaging 10 repeats and one five) was compared with that of the ETDRS logMAR chart in terms of TRV and agreement of acuity data. Results The 10 and five repeat computerised tests (PC-tests) produced a TRV of +/-0.11 and +/-0.10 logMAR, respectively, compared with +/-0.18 logMAR for the ETDRS chart. No significant bias was observed between PC-test and ETDRS acuities. CONCLUSIONS: A computerised system that takes repeated acuity measurements and averages them is subject to less TRV than a single ETDRS acuity measurement. A reduced TRV of visual acuity data allows earlier detection of true clinical change in individual patients. It also allows smaller differences between groups to be detected in clinical trials for a given degree of statistical confidence and power.

Reliability of telemedicine for diagnosing and managing eye problems in accident and emergency departments.

OBJECTIVES: To assess the accuracy and efficiency of telemedicine in diagnosing and managing eye problems presenting to accident and emergency departments. DESIGN: A controlled trial with a face-to-face and telemedicine phases, each involving 40 patients undergoing two consecutive consultations. In the face-to-face phase, both consultations were in person; in the telemedicine phase, observer 1 used videoconferencing technology at 384 kbit/s (separate nonslit lamp-torchlight and slit lamp examinations) and observer 2 saw the patient face to face. Setting The accident and emergency department at Moorfields Eye Hospital.Participants In total, 80 consenting new patients presenting to the department. MAIN OUTCOME MEASURES: (1) Agreement levels between the two observers for each phase (judged by an independent masked investigator), (2) length of consultation, and (3) number of unnecessary recalls. RESULTS: Agreement rates were as follows. Face-to-face phase: total agreement (30/40=75%), trivial disagreement (8/40=20%), clinically important disagreement (2/40=5%). Telemedicine phase (torchlight): complete agreement (16/40=40%), trivial disagreement (20/40=50%), clinically important disagreement (4/40=10%). Telemedicine phase (slit lamp): total agreement (23/40=58%), trivial disagreement (15/40=37%), clinically important disagreement (2/40=5%). Agreement levels in the telemedicine phase with torchlight examination were significantly lower (chi(2)=10.07, P=0.007) for any disagreement. Telemedicine consultations erred on the side of clinical caution and were no slower than face-to-face consultations (mean 6 min for observer 1 in both phases). Recalls were more likely (chi(2)=5.16, P=0.02) after telemedicine consultations with torchlight only (9/40) compared with face-to-face consultations (2/40). Although there were more significant disagreements using the telemedicine, in each case the telemedicine diagnosis and management erred on the side of safety; hence, no patient would have suffered by wrong management because of the consultation using telemedicine. CONCLUSIONS: Telemedicine was found to be an accurate, safe, and efficient method of diagnosing and managing these patients, especially if slit lamp images were used. Advice using telemedicine erred on the side of caution, which resulted in more recalls.

Evaluating a new logMAR chart designed to improve visual acuity assessment in population-based surveys.

AIMS: This study aimed to evaluate a new chart designed to improve the collection of visual acuity data in population-based surveys. The Reduced logMAR E chart (RLME) employs three letters per line, 'tumbling E' optotypes, and conforms to accepted contemporary design principles. METHODS: The performance of the chart was assessed within a population-based glaucoma survey in Thailand. Performance indices were test-retest variability (TRV) and agreement with acuity data measured using the ETDRS logMAR chart which acted as the 'gold standard'. RESULTS: The 95% confidence limits for TRV of RLME acuity data were +/-0.15 logMAR. This figure is consistent with published data on the TRV of acuities measured using five-letter-per-line logMAR charts. The mean difference between RLME and ETDRS acuity data was 0.00 logMAR (95% confidence intervals of +/-0.05 logMAR) indicating that RLME acuities agreed well with those of the ETDRS chart. The chart and its method of use was readily accepted by the local ancillary staff who required only minimal training before acuity measurement could be delegated to them. CONCLUSIONS: The study demonstrated that the RLME chart is capable of accurate and repeatable acuity measurements. Certain aspects of the design of the RLME chart may be particularly pertinent to the measurement of vision in population-based surveys.

Free-floating melanin particles in the anterior chamber: a normal finding in African eyes?

PURPOSE: Pigment dispersion syndrome (PDS) is a well-described entity with Krukenberg's spindle, heavy trabecular pigmentation and retroilluminating iris defects. We have observed a group of patients in mesoendemic onchocercal communities of Kaduna State, Nigeria, with significant amounts of free-floating melanin in the anterior chamber, normal angle pigmentation and absence of iris defects. A pseudo-Krukenberg spindle forms when the patients are asked to maintain a 2 min head-down posture as is often done when examining eyes for the presence of anterior chamber microfilaria. This spindle gradually disappears (tumbles back) after about 2 min of return to the erect posture. This paper describes this finding, which does not appear to fit into accepted notions of pigment dispersion. METHODS: As part of the seventh annual ivermectin dosing exercise during which evidence of optic nerve damage was sought, 455 patients were examined for the presence of microfilaria in the anterior chamber. A total of 352 had been selected for signs of optic nerve disease during an earlier screening exercise, while 103 belonged to a random sample of 5 years and above. Signs of onchocerciasis were sought, while gonioscopy and intraocular pressure measurements were carried out. RESULTS: Of the 455 (11%) individuals examined, 53 demonstrated this phenomenon. Within the random sample, the prevalence was 20%. These tumbling Krukenberg positive (TK+) individuals are significantly younger than TK- individuals and the prevalence, highest in the first decade, dropped steadily to zero levels over the age of 75. Sex distribution was about equal. There was no difference in intraocular pressure, cup-disc ratio and angle pigmentation. Distributions of sclerosing keratitis and chorioretinitis were not statistically different. Optic nerve disease was more common in TK- but this was attributable to the older age distribution. Five TK+ were re-examined after a period of 7 years and had not developed PDS or glaucoma. Four of the five remained TK+. A familial tendency was noted and hereditary factors may be at play, possibly autosomal recessive. The same phenomenon was noted in two of 44 patients in an ophthalmic clinic in Abuja, Nigeria, an urban, non-endemic city south of Kaduna. CONCLUSIONS: This phenomenon does not fit into accepted notions of PDS and may well be a normal finding.

Beta irradiation: new uses for an old treatment: a review.

Beta radiation has a long history as a treatment modality in ophthalmology. It is a convenient and practical method of applying radiation and has the advantage of minimal tissue penetration. There has been a recent resurgence in the use of beta radiation in other areas in medicine, such as the prevention of restenosis after coronary artery stenting. Beta radiation has been shown in vitro and in vivo to inhibit proliferation of human Tenon's fibroblasts, which enter a period of growth arrest but do not die. Effects on the cell cycle controller p53 have been shown to be important in this process. In ophthalmology, beta radiation has been used widely for the treatment of pterygium and is under evaluation for treatment of age-related macular degeneration and for controlling wound healing after glaucoma drainage surgery. In this latter role, beta radiation may be particularly appropriate for use in developing countries to improve the results of trabeculectomy while potentially avoiding some of the side effects of other antimetabolites.

Blindness: how to assess numbers and causes?

BACKGROUND: Traditionally, blindness surveys have modelled themselves on the "gold standard" of a census and examination of a whole population. Blindness, however, is a relatively rare condition even in badly affected communities; hence, large sample sizes are required to gain adequate estimates of prevalence, particularly by cause. METHODS: Three assessments of blindness prevalence and aetiology in the same communities are reported. One involved asking individuals questions concerning their visual status during a census (perceived visual status, PVD), one involved examination of all ostensibly visually disabled people presenting to a central point within each community (examination of the visually disabled, EVD), and the final assessment involved a gold standard examination of the whole population (whole community examination, WCE). RESULTS: In a population of 8139 the blindness prevalence was 2.7% PVS, 3.6% EVD, and 3.1% WCE. Attributed causes of blindness were not representative in the PVS except for cataract. The END yielded cause specific estimates not far from those found at WE except for a relative under-representation of glaucoma and optic atrophy. CONCLUSION: Since cataract is, by a significant margin, the most common cause of blindness in the world such a simple method as asking individuals if they are blind and what they believe to be the cause may yield adequate estimates of the problem for planning eye care strategies for this condition. Alternatively, an ophthalmologist visiting villages and examining allcomers for visual disability may provide reasonably accurate cause specific prevalence estimates without the expense of a major blindness survey.

The development of a "reduced logMAR" visual acuity chart for use in routine clinical practice.

BACKGROUND/AIMS: The advantages of logMAR acuity data over the Snellen fraction are well known, and yet existing logMAR charts have not been adopted into routine ophthalmic clinical use. As this may be due in part to the time required for a logMAR measurement, this study was performed to determine whether an abbreviated logMAR chart design could combine the advantages of existing charts with a clinically acceptable measurement time. METHODS: The test-retest variability, agreement (with the gold standard), and time taken for "single letter" (interpolated) acuity measurements taken using three prototype "reduced logMAR" (RLM) charts and the Snellen chart were compared with those of the ETDRS chart which acted as the gold standard. The Snellen chart was also scored with the more familiar "line assignment" method. The subjects undergoing these measurements were drawn from a typical clinical outpatient population exhibiting a range of acuities. RESULTS: The RLM A prototype chart achieved a test-retest variability of +/-0.24 logMAR compared with +/-0.18 for the ETDRS chart. Test-retest variability for the Snellen chart was +/-0.24 logMAR using clinically prohibitive "single letter" scoring increasing to +/-0.33 with the more usual "line assignment" method. All charts produced acuity data which agreed well with those of the ETDRS chart. "Single letter" acuity measurements using the prototype RLM charts were completed in approximately half the time of those taken using the ETDRS and Snellen charts. The duration of a Snellen "line assignment" measurement was not evaluated. CONCLUSION: The RLM A chart offers an acceptable level of test-retest variability when compared with the gold standard ETDRS chart, while reducing the measurement time by half. Also, by allowing a faster, less variable acuity measurement than the Snellen chart, the RLM A chart can bring the benefits of logMAR acuity to routine clinical practice.

Corneal changes of uncertain etiology in mesoendemic onchocercal communities of Northern Nigeria.

BACKGROUND: We report an unusual type of corneal change in some communities mesoendemic for onchocerciasis in Kaduna State of Northern Nigeria. METHODS: Thirty-four villages with an overall average microfilarial skin snip positivity rate of 71% and a total population of about 10,000 were included in a controlled trial of ivermectin for onchocerciasis. Detailed slit lamp examination of 806 persons within this population revealed at least 27 individuals with these lesions. There were 11 women and 16 men, aged between 5 and 70 years with a mean age of 45 years and a SD of 15 years. Drawings and photographs of 22 of these individuals were available for assessment. RESULTS: The lesions were peripheral, silvery white, and of two main types: the first group's lesions were flaky, refractile, and crystalline in appearance; the second group's lesions were more cylindrical in outline and were crisscrossed, giving a lattice-like pattern. There were indeterminate forms in between these polar topographies. Of the 25 subjects who had skin snips performed, 23 were microfilaria-positive. There was no accompanying inflammation and the posterior segments showed no evidence of crystalline deposits or retinitis pigmentosa, as is found in Bietti's dystrophy. The lesions coexisted with typical sclerosing keratitis in six individuals, and changes noted in the posterior pole of ten individuals were typical of onchocercal chorioretinitis. The evidence for consanguinity was not compelling. Differences between and similarities to Bietti's and Schnyder's crystalline corneal dystrophy, which are known to be composed of cholesterol crystals, are discussed. The lesions are also compared with lattice dystrophy known to be composed of amyloid. These lesions may be related to onchocercal infection. CONCLUSIONS: We describe some unusual peripheral corneal changes in individuals living within areas of Northern Nigeria mesoendemic for onchocerciasis. These changes take the form of flaky crystals or lattice within the anterior stroma and are common in middle-aged individuals. This may be related to onchocercal infection.

Glaucoma prevalence may not be uniformly high in all 'black' populations.

Epidemiological data on the prevalence of glaucoma are generally presented for populations described as "whites" or "blacks". "Black" populations appear to have a higher glaucoma preva lence than "white" populations. We describe a population-baseed survey for glaucoma in rural Northern Nigeria. A total of 1563 Hausa/Fulani individuals aged 5 years and above, underwent an extensive screening test and a detailed ophthalmological examination was performed on individuals who failed the test. The overall prevalence of open angle glaucoma in this population was 1.02% (0.12 to 3.64, 95% confidence interval) in individuals 45 years of age and older. This is lower than the prevalence rates reported for other "black" populations. The low prevalence of glaucoma detected in this African population may be, to some extent, a reflection of the age structure of the population studied or methodological differences in ophthalmic examinations performed. It is also possible that the prevalence of glaucoma varies considerably between "black" populations due to genetic heterogeneity or the effect of some unidentified environmental exposure. The use of the simple description of populations as 'black' (or 'white'), which focuses on a commonality, tends to obscure the potential heterogeneity within and between populations and thus may be unhelpful in some circumstances.