Dineen BP, Bourne RRA, Ali SM, Noourl Haq DM, Johnson GJ, Br J Ophthalmol 2003;87:820-8

According to the World Health Organization worldwide there are an estimated 45 million people that are blind with an additional 135 million individuals visually impaired. Globally it is known that cataract is the leading caused of blindness, with some 16-20 million people suffering from blinding cataract^2,3. In country specific terms, India is the country with the highest number of blind people (over 9 million) with the most prevalent cause of blindness and low vision being unoperated cataract, as indicated by several population based studies over the past two decades.

In the neighboring region, blindness prevalence surveys have been conducted in Nepal nationally and in one region of Pakistan that yielded all age blindness prevalence rates of 0.8% and 1.0% respectively. A subsequent survey in two administrative regions of Nepal identified a blindness prevalence of 3.0% in people 45 years and older. Before this present study, no nationwide study had been conducted in Bangladesh-a country of over 130 million inhabitants-concerning the extent of blindness or the main causes of vision impairment. This lack of vital information is particularly serious, given the strategies identified in the WHO Global Initiative for the Elimination of Avoidable blindness by 2020 (Vision 2020). The absence of reliable population based epidemiological data on blindness and low vision in Banglandesh is a serious impediment to the effective national planning of eye care programmes.

In order to redress the lack of blindness and low vision data among adults for this populous country, a nationwide survey was designed. The purpose of this study was to estimate the age and sex specific prevalence rates of blindness and visual impairment in adults 30 years of age and older in Banglandesh and to identify the cause specific prevalence in the sample.

A nationally representative sample of 12782 adults 30 years of age and older was selected based on multistage, cluster random sampling with probability proportional to size procedures. The breakdown of the cluster sites was proportional to the rural/urban distribution of the national population. The examination protocol consisted of an interview, visual acuity (VA) testing, auto refraction, and optic disc examination on all subjects. Corrected VA retesting, cataract grading, and a dilated fundal examination were performed on all visual impaired subjects. The definitions of blindness (<3/60) and low vision (<6/12 to > 3/60) were based on the presenting visual acuity in the better eye. The world Health Organization/Prevention of Blindness proforma and its classification system for identifying the main cause of low vision and blindness for each examined subject was used.

In total, 11 624 eligible subjects were examined (90.9% response rate) across the 154 cluster sites. A total of 162 people were bilaterally blind (1.53% age standardized prevalence) while a further 1608 subjects (13.8%) had low vision (<6/12 VA) binocularly. Visual acuity was > 6/12 in the “better eye” in the remaining 9854 subjects (84.8%); however, 748 of these people had low vision in the fellow eye. The main causes of low vision were cataract (74.2%), refractive error (18.7%), and macular degeneration (1.9%). Cataract was the predominant cause (79.6%) of bilateral blindness followed by uncorrected aphakia (6.2%) and macular degeneration (3.1%).

The authors concluded with the remarks that there are an estimated 650000 blind adults (95% CI 552 175 to 740 736) aged 30 and over in Banglandesh, the large majority of whom are suffering from operable cataract. This survey indicates the need for the development and implementation of a national plan for the delivery of effective eye care services, aimed principally at resolving the large cataract backlog and the inordinate burden of refractive error.

Incidence of visual loss in Rural southwest Uganda

Mbulaiteye SM, Reeves BC, Mulwanyi F Whitworth JAG, Johnson G

Br J Ophthalmol 2003;87:829-33.

Blindness and visual impairment contribute to significant avoidable handicap in Africa, mainly because of cataract, refractive errors, nutrition, and various infections and trachoma. Several studies have described the prevalence of blindness or visual impairment (referred to as visual loss in this paper) in sub-Saharan Africa. A recent review identified 22 surveys conducted between 1980 and 2000, but none provided incidence data. These studies have focused mainly on nutritional and infective causes of visual loss in countries where these conditions are common. As the proportion of visual impairment attributable to these conditions falls, the relative importance of other causes will increase. No studies have looked at the incidence of visual loss in Africa in settings in which infectious conditions are not the dominant cause of visual impairment, partly because of the large expense and the need for specialized staff that is usually required.

Recently, “Vision 2020” was initiated as a worldwide programme to reduce the number of blind people from 75 million to 25 million by 2020. The initiative calls for staff, infrastructure, and capacity development by governments and non-governmental organization involved in eye care and to improve coordinated and targeted delivery of diagnostic, therapeutic, and surveillance technologies to populations in need of services. However, the lack of data on incidence of visual loss in parts of Africa limits forecasting of the needs and the service provision relevant to particular populations. We recently reported the use of an E-optotype chart as a simple cheap tool with high sensitivity and specificity for identifying visual loss in a rural population in southwest Uganda.¹² We now report the incidence and causes of visual loss in this population, using the E-optotype chart, followed between 1994 and 1998.

Bacterial keratitis: predisposing factors, clinical and microbiological review of 300 cases

Bourcier T, Thomas F, Borderie V. Chaumeil C, Laroche L. Br J Ophthalmol 2003;87:834-8

Bacterial keratitis is a serious ocular infectious disease that can lead to servere visual disability. The severity of the corneal infection usually depends on the underlying condition of the cornea and the pathogenicity of the infecting bacteria. Many patients have a poor clinical outcome if aggressive and appropriate therapy is not promptly initiated.

Bacterial keratitis is rare in the absence of predisposing factors. Until recently, most cases of bacterial keratitis were associated with ocular trauma or ocular surface diseases. However, the widespread use of contact lenses has dramatically increased the incidence of contact lens related keratitis. The spectrum of bacterial keratitis can also be influenced by geographic and climatic factors. Many differences in keratitis profile have been noted between populations living in rural or in city areas, in western, or in developing countries.

In recent years the literature extensively addressed this issue but only a few publications reviewed large series of patients with bacterial keratitis. Very little information is available on the frequency of factors predisposing to bacterial keratitis and on the demographic characteristics of those patients.

The purpose of this study was to identify predisposing factors and to define clinical and microbiological characteristics of bacterial keratitis in current practice.

A retrospective analysis of the hospital records of patients presenting with bacterial keratitis and treated at the Quinze-Vingts National Center of Ophthalmology, Paris, France, was performed during a 20 month period. A bacterial keratitis was defined as a suppurative corneal infiltrate and overlying epithelial defect associated with presence of bacteria on corneal scraping and/or that was cured with antibiotic therapy. Risk factors, clinical and microbiological data were collected.

300 cases (291 patients) of presumed bacterial kertitis were included. Potential predisposing factors, usually multiple, were identified in 90.6% of cases. Contact lens wear was the main risk factor (50.3%). Trauma or a history of keratopathy was found in 15% and 21% of cases, respectively. An organism was identified in 201 eyes (68%). 83% of the infections involved Gram positive bacteria, 17% involved Gram negative bacteria, and 2% were polymicrobial. Gram negative bacteria were associated with severe anterior chamber inflammation (p=0.004), as well as greater surface of infiltrates (p=0.01). 99% of ulcers resolved with treatment, but only 60% of patients had visual acuity better than the level at admission, and 5% had very poor visual outcome.

The authors concluded that contact lens wear is the most important risk factor. Most community acquired bacterial ulcers resolve with appropriate treatment.

Is manual small incision cataract surgery affordable in the developing countries? A cost comparison with extracapsular

cataract extraction

Gogate PM, Deshpande M, Wormald RP. Br J Ophthalmol 2003;87:843-6

A single masked randomized trial was used to compare the safety, efficacy, time, and patient satisfaction of surgery by both the techniques. The fixed facility and recurrent cost for the two procedures was calculated based on information collected form different sources. Average cost per procedure was calculated by dividing the total cost by the number of procedures performed.

The average cost of an ECCE procedure for the hospital was Rs 727.76 (US$15.82) and the average cost of a MSICS procedure was Rs 721.40 ($ 15.68), of which Rs 521.51 ($11.34) was the fixed facility cost common to both.

The authors reached the conclusion that both ECCE and MSICS are economical in community eye care settings, but MSICS is economical and given better uncorrected visual acuity in a greater proportion of patients.

A 10 year retrospective survey of cataract Surgery and endophthalmitis in a Single Eye  Unit: injectable lenses lower

The incidence of endophthalmitis

Mayer E, Cadman D, Ewings P, Twomey JM. Gray RH, Claridge KG,  Hakin KN, Bates AK

Br J Ophthalmol 2003;87:867-9

Cataract surgery is one of the most commonly performed and successful surgical procedures in the world. Over the past 10 years in the United Kingdom, there has been a progressive change from extracapsular extraction (ECCE) to phacoemulsification (phaco). Concurrent with this change has been the development of foldable and injectable intraocular lenses (IOLs), obviating the need for incision enlargement.

Complications after cataract surgery occur with similar frequency for both phaco and ECCE. Endophthalmitis can be one of the most devastating of these, since it can lead to complete blindness in the affected eye; unchecked it can even give rise to cavernous sinus thrombosis and death. Fortunately it is rare, with a reported frequency in the UK National Cataract Surgery Survey of between 0.1 and 0.2%, a figure comparable with other reports.

Most cases of postoperative endophthalmitis occur acutely, with a speed and severity that reflect bacterial load and virulence. Virulent organisms present early, usually with hypopyon and severe inflammation. Less virulent organisms cause milder and later onset disease, which may respond to topical steroids, and are difficult to distinguish from persistent postoperative inflammation. The purpose of this study was to study the incidence of endophthalmitis following cataract surgery over a 10 year period, and to examine ways in which this may be related to changes in surgical technique.

All cases of endophthalmitis occurring over a 10 year period within a single ophthalmic unit in the United Kingdom were reviewed, and possible risk factors identified. During the study period, as the technique of extracapsular cataract surgery was replaced by phacoemulsification, there was a commensurate reduction in the incidence of endophthalmitis. Injectable IOLs were associated with the lowest risk of postoperative endophthalmitis (0.028%). The authors observed and concluded with remarks that injectable intraocular lenses do not make contact with the ocular surface and this may result in the observed lower rate of endophthalmitis. This, and the ease with which they can be inserted through small incisions, support their use as the first line method of lens insertion.

Retinal thickness decreases with age: An OCT study

Alamouti B, Funk J. Br. J Ophthalmol 2003;87:899-901.

Confocal laser scanning tomography (Heidelberg retina tomograph, HRT) is a useful tool to monitor the progression of optic disc cupping in glaucoma or ocular hypertension. When optic disc parameters are calculated by the HRT, a reference plane is used. The height of this reference plane depends on the retinal thickness at the temporal disc margin. It was assumed that the retinal thickness and the RNFL (retinal nerve fibre layer) thickness at this particular position do no decrease with age.

The purpose of the present study was to verify whether the latter hypothesis is right or wrong using optical coherence tomography (OCT: OCT 2000, Humphrey Instruments, San Leandro, CA, USA). In addition authors wanted to determine the reproducibility of OCT measurements at the temporal disc margin.

In three dimensional optic disc tomography a reference plane is required to calculate optic disc rim or cup values. The position of the reference plane often depends on the retinal thickness at the temporal disc margin. Originally it was assumed that the retinal thickness at the temporal disc margin is independent of age.

100 eyes of 100 healthy volunteers were included in this study. Three OCT scans were performed on each eye. The scans were aligned vertically and placed at the temporal edge of the optic disc. For each eye, the thickness of the whole retina as well as the thickness of the retinal nerve fibre layer were calculated together with their coefficients of variation. Thereafter retinal thickness and nerve fibre layer thickness were correlated with age.

The mean retinal thickness was 249 (SD 22) μm. The mean nerve fibre layer thickness was 109 (22) μm. The mean coefficients of variation were 3.5% (total retinal thickness) and 8.0% (nerve fibre layer thickness). Both the total retinal thickness and the nerve fibre layer thickness were significantly correlated with age (total retina: y=269.5 – 0.53 x x; R²=0.133; p = 0.0002, nerve fibre layer: y = 126.8 – 0.44 x x; R² = 0.094; p <0.0019.

The authors concluded that using OCT scans the total retinal thickness can be calculated with high reproducibility (coefficient of variation = 3.5%). The reproducibility of nerve fibre layer thickness measurements is clearly lower (coefficient of variation = 8.0%). Both the total retinal thickness and the nerve fibre layer thickness significantly decrease with age. This influence of the age related decrease in RNFL/retinal thickness on the reference plane, however, is negligible. 

Detecting chloroquine retinopathy: Electro-oculogram versus colour vision

Neubauer AS, Samari-Kermani K, Schaller U.  Welge-Lϋβen U, Rudolph G.

Br J Ophthalmol 2003;87:902-8

Ocular toxicity caused by antimalarials was first described in the literature as early as 1957. As antimalarials were found effective not only for treatment and prophylaxis of malaria but also for many rheumatoid diseases they are used ever more frequently nowadays and are given as a long term medication. The risk of ocular toxicity is given as a along term medication. The risk of ocular toxicity is therefore considerable. The incidence of early retinopathy in ophthalmologically unmonitored patients was estimated as 10% for chloroquine and 3-4% for hydroxychloroquine. Advanced retinopathy had an incidence of 0.5%. These risks might be reduced substantially be regular observation and testing.

Some degree of corneal deposits (verticillata) can be demonstrated in most patients taking chloroquine, but these changes very rarely impair vision. Corneal deposits occur more frequently with chloroquine than with hydroxychloroquine, are located in the epithelium and subepithelial stroma and are mostly reversible. By contrast, retinopathy is severe ocular side effect presenting with bilateral, reproducible, and permanent visual field abnormalities. Early retinal changes consist of a pigmentary stippling or granular appearance of the macula, with the patient still being asymptomatic. Advanced retinopathy may show the typical “bull’s eye’ maculopathy associated with impaired visual acuity and central visual field defects. These changes of advanced maculopathy are irreversible and may progress even after cessation of the drug.

To purpose of this study was to investigate the relative sensitivity and specificity of two tests of retinal function (the electro-oculogram (EOG) and a computerized colour vision test) in screening for ocular toxicity caused by chloroquine and hydroxychloroquine.

93 patients with rheumatic diseases receiving long term chloroquine and hydroxychloroquine therapy were followed for an average of 2.6 years. Clinical examination, an EOG, and a quantitative test of colour vision were carried out every 6 months.

Mild fundus changes were observed in 38 patients. Four patients developed typical bull’s eye maculopathy, three of whom had received 250,365, and 550 g total dose of chloroquine, and one 1500  g of hydroxychloroquine. Statistical analysis of all patients showed that for those with no fundus changes or stippled pigmentation a number showed elevation of tritan threshold, so that if macular stippling is a sign of mild retinopathy the test on tritan changes has a 64% sensitivity and 63% specificity for an upper threshold value of 7%. All four patients with bull’s eye lesions showed a marked disturbance of tritan colour vision, with a threshold of 14.8%, a sensitivity of 75%, and a specificity of 94%. For protan colour vision a threshold of 10% gives 75% sensitivity and 91% specificity. By contrast, neither an absolute nor a relative EOG reduction was a valid criterion for early or late chloroquine retinopathy. In advanced retinopathy an Arden coefficient (AQ) < 180% yields 50% sensitivity and 54% specificity. When AQ < (160% is the threshold, sensitivity does not increase but specificity rises to 82%. Occurrence of marked corneal deposits on clinical examination yields 50% sensitivity and 90% specificity in this situation.

The authors concluded that screening for chloroquine retinopathy can be improved by using a sensitive colour test. Disturbance of the tritan axis appears to occur first. A normal test result on computerized colour testing virtually excludes any retinopathy by antimalarials. The EOG is of little diagnostic value.