Academic journal article Bulletin of the World Health Organization

Monitoring Visual Outcome of Cataract Surgery in India

Academic journal article Bulletin of the World Health Organization

Monitoring Visual Outcome of Cataract Surgery in India

Article excerpt

Voir page 458 le resume en francais. En la pagina 459 figura un resume en espanol.

Introduction

Cataract is the major cause of blindness and of severe visual impairment in many developing countries, leading to bilateral blindness in an estimated 20 million people worldwide. The latest available national data on cataract blindness in India date from 1989 (1). By projecting prevalence data, we estimated that in 1997 there were 5.4 million persons who were bilaterally blind (visual acuity [is less than] 3/60) and 11.5 million with bilateral severe visual impairment (visual acuity [is less than] 6/60) from cataract throughout the country.

The performance of cataract intervention programmes is assessed by the number of cataract operations conducted each year. In India, this number has increased from 1.2 million in 1989 to 2.7 million in 1996 (Central Ophthalmic Cell, Directorate General Health Services, Government of India, unpublished data, 1997). The crude cataract surgical rate (CSR) can be estimated using the total population as denominator; age-specific rates can also be calculated if population and surgery data are available for defined age groups (2). For India, the CSR in 1996 was approximately 2800 per million of the total population.

Cataract surgery aims to rehabilitate blind or visually impaired persons by restoring their eyesight so that their quality of life and ability to function are returned to normal or as near normal as possible. The outcome of cataract surgery for an individual or for a defined population is therefore as important as measuring the quantity of surgical operations performed. Outcome can be measured simply as the visual acuity in the operated eye or in the patient (3), and also in terms of ability to function, quality of life (4, 5), and economic rehabilitation (6). The last three of these parameters can only be assessed through time-consuming studies and fall outside the scope of this article.

Here we describe the evaluation of two simple methods for determining visual outcome following cataract surgery, which might be used by ophthalmologists and programme managers to monitor the quality of cataract surgery services.

Materials and methods

The first method consisted of examining the records of patients who had undergone cataract surgery. Following field trials in several districts of India, a standardized cataract surgical record was introduced in April 1996 by the National Programme for Control of Blindness to record the age, sex, pre- and postoperative visual acuity for each eye with provided correction, place and type of surgery and complications.(a) The postoperative visual acuity is to be measured 4-6 weeks after the surgery. Data from such records from several districts in the states of Gujarat, Karnataka and Maharashtra were collected and analysed. The data were not collected by a randomized method and therefore may not be representative.

Measures of outcome were classified as "good", "borderline" or "poor". "Good outcome" was defined as a visual acuity of [is greater than or equal to] 6/18 with the available correction; "borderline outcome" as 6/24-6/60; and "poor outcome" as [is less than] 6/60. Using patients' records it was possible to calculate the proportion of cataract operations that had resulted in sight restoration in bilaterally blind (or severely visually impaired) persons. This sight restoration rate (SRR) is a measure of the efficiency of a programme in reducing the prevalence of cataract blindness and is given by the following expression:

SRR = P (pre) - P (post) x 100/C

where

P (pre) = number of persons with the specified preoperative visual acuity in the better eye (e.g. [is less than] 3/60);

P (post) = number of persons with the specified postoperative visual acuity in the better eye (e.g. [is less than] 3/60); and

C = total number of cataract operations evaluated in the period. …

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