J M Sparrow

The lens in diabetes

This paper reviews the changes which occur in the human lens in diabetes. They include refractive changes and cataract and age-related increases in thickness, curvatures, light scattering, autofluorescence and yellowing. The incidence of cataract is greatly increased over the age of 50 years, slightly more so in women, compared with non-diabetics. Experimental models of sugar cataract provide some evidence for the mechanism of the uncommon, but morphologically distinct, juvenile form of human diabetic cataract, where an osmotic mechanism due to sugar alcohol accumulation has been thoroughly studied in diabetic or galactose-fed rats. The discrepancy between the ready accumulation of sugar alcohol in the lens in model systems and the very slow kinetics of aldose reductase (AR) has not been satisfactorily explained and suggests that the mechanism of polyol formation is not yet fully understood in mammalian systems. The activity of AR in the human lens lies mainly in the epithelium and there appears to be a marginal expectation that sufficient sorbi-tol accumulates in cortical lens fibres to explain the lens swelling and cataract on an osmotic basis. This is even more so in the cataracts of adult diabetics, which resemble those of age-related non-diabetic cataracts in appearance. The very low levels of sorbitol in adult diabetic lenses make an osmotic mechanism for the increased risk of cataract even less likely. Other mechanisms, including glycation and oxidative stress, are discussed. The occurrence of cataract is a predictor for increased mortality in the diabetic.

Prevalence and risk factors for common vision problems in children: data from the ALSPAC study

Objective: To estimate the distribution and predictors of some common visual problems (strabismus, amblyopia, hypermetropia) within a population-based cohort of children at the age of 7 years. Methods: Children participating in a birth cohort study were examined by orthoptists who carried out cover/uncover, alternate cover, visual acuity and non-cycloplegic refraction tests. Prospectively collected data on potential risk factors were available from the study. Results: Data were available for 7825 seven-year-old children. 2.3% (95% CI 2.0% to 2.7%) had manifest strabismus, 3.6% (95% CI 3.3% to 4.1%) had past/present amblyopia, and 4.8% (95% CI 4.4% to 5.3%) were hypermetropic. Children from the lowest occupational social class background were 1.82 (95% CI 1.03% to 3.23%) times more likely to be hypermetropic than children from the highest social class. Amblyopia (p = 0.089) and convergent strabismus (p = 0.066) also tended to increase as social class decreased. Conclusions: Although strabismus has decreased in the UK, it and amblyopia remain common problems. Children from less advantaged backgrounds were more at risk of hypermetropia and to a lesser extent of amblyopia and convergent strabismus. Children’s eye-care services may need to take account of this socio-economic gradient in prevalence to avoid inequity in access to care.

Amblyopia treatment outcomes after screening before or at age 3 years: follow up from randomised trial

Abstract Objective: To assess the effectiveness of early treatment for amblyopia in children. Design: Follow up of outcomes of treatment for amblyopia in a randomised controlled trial comparing intensive orthoptic screening at 8, 12, 18, 25, 31, and 37 months (intensive group) with orthoptic screening at 37 months only (control group). Setting: Avon, southwest England. Participants: 3490 children who were part of a birth cohort study. Main outcome measures: Prevalence of amblyopia and visual acuity of the worse seeing eye at 7.5 years of age. Results: Amblyopia at 7.5 years was less prevalent in the intensive group than in the control group (0.6% v 1.8%; P=0.02). Mean visual acuities in the worse seeing eye were better for children who had been treated for amblyopia in the intensive group than for similar children in the control group (0.15 v 0.26 LogMAR units; P<0.001). A higher proportion of the children who were treated for amblyopia had been seen in a hospital eye clinic before 3 years of age in the intensive group than in the control group (48% v 13%; P=0.0002). Conclusions: The intensive screening protocol was associated with better acuity in the amblyopic eye and a lower prevalence of amblyopia at 7.5 years of age, in comparison with screening at 37 months only. These data support the hypothesis that early treatment for amblyopia leads to a better outcome than later treatment and may act as a stimulus for research into feasible screening programmes. What is already known on this topic Observational studies have produced conflicting results about whether early treatment for amblyopia gives better results than later treatment A recent systematic review highlighted the lack of high quality data available and recommended the cessation of preschool vision screening programmes This has led to fierce debate and to confusion about the provision of vision screening services What this study adds Children treated for amblyopia are four times more likely to remain amblyopic if they were screened at 37 months only than if they were screened repeatedly between 8 and 37 months Children screened early can see an average of one line more with their amblyopic eye after treatment than children screened at 37 months Early treatment is more effective than later treatment for amblyopia, supporting the principle of preschool vision screening

Amblyopia treatment outcomes after preschool screening v school entry screening: observational data from a prospective cohort study

Background/aims: Preschool screening for amblyopia has controversially been abandoned in some localities within the United Kingdom, on the basis that there is no clear evidence of benefit to support its continuation. Data collected within a birth cohort study were used to examine visual outcomes at 7½ years in children who did or did not receive preschool vision screening. Methods: Monocular logMAR visual acuity with and without a pinhole was assessed by orthoptists. Contemporary records were used to identify children who had been offered and/or received preschool screening. Results: Of 6081 children, 24.9% had been offered preschool screening and 16.7% had attended. The prevalence of amblyopia was approximately 45% lower in the children who received preschool screening than in those who did not (1.1% v 2.0%, p = 0.05). The mean acuity in the worse seeing eyes after patching treatment was better for amblyopic children who received preschool screening than for those who did not; 0.14 v 0.20 logMAR (p <0.001). These effects did not persist in an intention to screen analysis. Conclusions: Preschool screening at 37 months was associated with an improved treatment outcome for individuals with amblyopia. However, the improvement was clinically small and disappeared when considering all children offered screening rather than only those who received it. Further research is needed into improving the effectiveness of vision screening for preschool children, while in the interim these data do not conflict with current recommendations for school entry screening by orthoptists.

Screening for amblyopia in preschool children: results of a population-based, randomised controlled trial. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood

Abstract INTRODUCTION The rationale for preschool vision screening programmes has recently been questioned. Evidence about the effects of early treatment is needed, but it is not known how early the target conditions can reliably be detected. In this study, an intensive programme comprising several different screening methods, used at different ages up to 37 months, was compared with the usual practice of visual surveillance and ad hoc referrals. METHODS Two groups were randomly selected from children in a population birth cohort study. The control group (n = 1461) received visual surveillance only. The intervention group (n = 2029) was offered in addition a programme of regular visual assessments by orthoptists testing visual acuity, ocular alignment, stereopsis and non-cycloplegic photorefraction. RESULTS The intervention group programme yielded more children with amblyopia (1.6% vs. 0.5%, p < 0.01), and was more specific (95% vs. 92%, p < 0.01), than the control programme. The individual components of the intervention programme were compared. The cover test and visual acuity tests were poorly sensitive until the children were 37 months, but were always >99% specific. Photorefraction was more sensitive than acuity testing at all ages below 37 months, with specificity >95% at 31 and 37 months. CONCLUSIONS Photorefraction would have detected more children less than 37 months of age with straight-eyed amblyopia than did visual acuity testing, but with more false positives. At 37 months, photore-fraction plus a cover test would have been comparable in effectiveness to visual acuity testing plus a cover test.

The prevalence of diabetic retinopathy and maculopathy and their risk factors in the non-insulin-treated diabetic patients of an English town.

A total population study of the ocular status of all known non-insulin-treated diabetic patients resident in the English town of Melton Mowbray has been conducted. The population prevalence of non-insulin-treated diabetes in the town was 6.7/1000. There were 215 patients in the target population, with 65% of the resident survivors participating in the study. Further data on ocular status were gathered from hospital records, bringing the total percentage for whom some information on ocular status was available to 74%. Corrected Snellen acuity was 6/12 or better in 76% of patients and the overall prevalence rate for any diabetic retinopathy was 52%, for proliferative retinopathy was 4%, and for maculopathy requiring treatment was 10%. In a multivariate analysis, risk factors for retinopathy and/or maculopathy included longer diabetic duration, female sex, higher blood pressure, the use of anti-hypertensive drugs and cigarette smoking.

The Royal College of Ophthalmologists’ National Ophthalmology Database study of cataract surgery: report 1, visual outcomes and complications

AimsTo describe the outcomes of cataract surgery in the United Kingdom.MethodsAnonymised data on 180 114 eyes from 127 685 patients undergoing cataract surgery between August 2006 and November 2010 were collected prospectively from 28 sites. Outcome measures included intraoperative and postoperative complication rates, and preoperative and postoperative visual acuities.ResultsMedian age at first eye surgery was 77.1 years, 36.9% cases had ocular co-pathology and 41.0% patients underwent cataract surgery on both eyes. Preoperative visual acuity was 0.30 logMAR or better in 32.0% first eyes and 47.7% second eyes. Postoperative best-measured visual acuity was 0.00 and 0.30 logMAR or better in 50.8 and 94.6% eyes without ocular co-pathology, and 32.5 and 79.9% in eyes with co-pathology. For eyes without co-pathology, postoperative uncorrected distance visual acuity was 0.00 and 0.30 logMAR or better in 27.3 and 80.9% eyes. Posterior capsule rupture or vitreous loss or both occurred in 1.95% cases, and was associated with a 42 times higher risk of retinal detachment surgery within 3 months and an eight times higher risk of endophthalmitis.ConclusionThese results provide updated data for the benchmarking of cataract surgery. Visual outcomes, and the rate of posterior capsule rupture or vitreous loss or both appear stable over the past decade.

The objective assessment of cataract.

The objective assessment of cataract is central to any epidemiological or therapeutic study of cataract. The objective methods consist of:1: A resolution target projection ophthalmoscope (Acuity scope) for the estimation of potential visual acuity.2: The Oxford Clinical Cataract Classification and Grading System, which records and quantifies the features of the lens that are visible at the slit-lamp microscope. This system is essential since photographic methods cannot define the morphology of cataract.3: Two photographic methods; slit-lamp photography and retro-illumination photography are needed to give a comprehensive statement about the amount of cataract. The negatives are measured by computerised image analysis systems.

The Bristol shared care glaucoma study: outcome at follow up at 2 years

AIM To examine the outcome of care for patients with glaucoma followed up by the hospital eye service compared with those followed up by community optometrists. METHODS A randomised study with patients allocated to follow up by the hospital eye service or community optometrists was carried out in the former county of Avon in south west England. 403 patients with established or suspected primary open angle glaucoma attending Bristol Eye Hospital and meeting defined inclusion and exclusion criteria were studied. The mean number of missed points on visual field testing in the better eye (using a “better/worse” eye analysis) in each group were measured. The visual field was measured using the Henson semiautomated central field analyser (CFA 3000). Measurements were made by the research team on all patients at baseline before randomisation and again 2 years after randomisation. The mean number of missed 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 at 2 years were also measured. Measurements were made by the research team on all patients at baseline before randomisation and again 2 years after randomisation. An analysis of covariance comparing method of follow up taking into account baseline measurements of outcome variables was carried out. Additional control was considered for age, sex, diagnostic group (glaucoma suspect/established primary open angle glaucoma), and treatment (any/none). RESULTS From examination of patient notes, 2780 patients with established or suspected glaucoma were identified. Of these, 752 (27.1%) fulfilled the entry criteria. For hospital and community follow up group respectively, mean number of missed points on visual field testing at 2 year follow up for better eye was 7.9 points and 6.8 points; for the worse eye 20.2 points and 18.4 points. Similarly, intraocular pressure was 19.3 mm Hg and 19.3 mm Hg (better eye), and 19.1 mm Hg and 19.0 mm Hg (worse eye); cup disc ratio at 2 year follow up was 0.72 and 0.72 (better eye), and 0.74 and 0.74 for hospital and community follow up group respectively. No significant differences in any of the key visual variables were found between the two groups before or after adjusting for baseline values and age, sex, treatment, and type of glaucoma. CONCLUSIONS It is feasible to set and run shared care schemes for a proportion of patients with suspected and established glaucoma using community optometrists. After 2 years (a relatively short time in the life of a patient with glaucoma), there were no marked or statistically significant differences in outcome between patients followed up in the hospital eye service or by community optometrists. Decisions to implement such schemes need to be based on careful consideration of the costs of such schemes and local circumstances, including geographical access and the current organisation of glaucoma care within the hospital eye service.

The Bristol Shared Care Glaucoma Study: reliability of community optometric and hospital eye service test measures

BACKGROUND/AIMS Primary open angle glaucoma patients and glaucoma suspects make up a considerable proportion of outpatient ophthalmological attendances and require lifelong review. Community optometrists can be suitably trained for assessment of glaucoma. This randomised controlled trial aims to assess the ability of community optometrists in the monitoring of this group of patients. METHODS Measures of cup to disc ratio, visual field score, and intraocular pressure were taken by community optometrists, the hospital eye service and a research clinic reference “gold” standard in 405 stable glaucoma patients and ocular hypertensives. Agreement between and within the three centres was assessed using mean differences and intraclass correlation coefficients. Tolerance limits for a change in status at the level of individual pairs of measurements were also calculated. RESULTS Compared with a research clinic reference standard, measurements made by community optometrists and those made in the routine hospital eye service were similar. Mean measurement differences and variability were similar across all three groups compared for each of the test variables (IOP, cup to disc ratio, and visual field). Overall, the visual field was found to be the most reliable measurement and the cup to disc ratio the least. CONCLUSIONS Trained community optometrists are able to make reliable measurements of the factors important in the assessment of glaucoma patients and glaucoma suspects. This clinical ability should allow those optometrists with appropriate training to play a role in the monitoring of suitable patients.