doi:10.1136/bjo.2006.110973 2007 91 927-932 originally published online 1 Feb 2007 Br. J. Ophthalmol. Sarah Polack, Hannah Kuper, Wanjiku Mathenge, Astrid Fletcher and Allen Foster Kenyan population Cataract visual impairment and quality of life in a http://bjo.bmj.com/cgi/content/full/91/7/927 Updated information and services can be found at: These include: References http://bjo.bmj.com/cgi/content/full/91/7/927#BIBL This article cites 22 articles, 8 of which can be accessed free at: Rapid responses http://bjo.bmj.com/cgi/eletter-submit/91/7/927 You can respond to this article at: service Email alerting top right corner of the article Receive free email alerts when new articles cite this article - sign up in the box at the Notes http://journals.bmj.com/cgi/reprintform To order reprints of this article go to: http://journals.bmj.com/subscriptions/ go to: British Journal of Ophthalmology To subscribe to on 30 May 2008 bjo.bmj.com Downloaded from

met the case definition. This hospital is the main centre for cataract surgery in Nakuru district and serves people from across the district. Three different methods were employed because of logistical and time constraints. Procedures for ophthalmic examination, case selection criteria and consent were the same in each. Ophthalmic examination and case definition The case definition was people aged 50 years with best corrected VA ,6/24 in the better eye due to cataract, living in Nakuru district. All clinical examinations and diagnoses were made by ophthalmologists. VA was measured with available correction using a tumbling ������E������ chart. For each case in the survey, one or two age- and sex-matched control subjects (VA 6/18) were randomly selected from the same cluster. Vision-related quality of life The WHO/PBD VFQ2013 was translated into Swahili and two local languages (Kikuyu and Kalenjin), and back-translated by independent translators, who were asked to comment on the appropriateness of language used for the target population. A review was held to discuss differences in the translations and to modify them accordingly. The scale was pilot tested on 20 patients in the eye unit, Nakuru District Hospital, and small modifications to the wording of some items were made to ensure local understanding. One question, ������how much diffi- culty do you have in seeing because of glare from bright lights?������, caused difficulties for respondents from rural areas where there was a lack of electricity or car lights. Following consultation with an ophthalmologist, this question was removed. For test���retest reliability assessment, the question- naire was administered to 20 patients at the eye unit, Nakuru Hospital in the afternoon, and again the next morning by the same interviewer. Health-related quality of life To assess health-related quality of life, items from the European Quality of Life Questionnaire (EQ-5D) were used. This scale was designed by the European quality of life (EuroQol) group to be brief, simple and practical for use in surveys alongside disease-specific measures.17 Evidence of validity and reliability in high- and low-income settings has been shown.18���20 The EQ- 5D includes two components. The first consists of five descriptive dimensions: mobility, self-care, usual activity, pain/discomfort and anxiety/depression, each with three response options: no problem, some problem or extreme problem. The second is a visual analogue scale (VAS), with scores ranging from 0 (������worst imaginable health state������) to 100 (������best imaginable health state������). Respondents are asked to indicate on the scale where they rate their ������own health state today������. For all study members this scale was described verbally, enabling those members unable to see the scale to respond. The same translation procedure described above was used to translate the EQ-5D. However, due to time constraints, this was carried out independently from the EuroQol group, and the versions used in this study have therefore not been approved by the EuroQol group. Interviews Six interviewers were trained for 1 week, and interviews were observed periodically throughout the study. Ethical considerations Informed signed or thumb-printed consent was obtained from all study subjects. All cases were offered free cataract surgery at the district hospital. People with visual impairment, but not eligible to be study cases, were examined and referred to the district hospital accordingly. Ethical approval for this study was obtained from the ethics committees of the London School of Hygiene & Tropical Medicine, London, UK, and the Kenya Medical Research Institute, Nairobi, Kenya. Statistical analysis Visual acuity For analysis, presenting VA in the better eye with available correction was grouped into the following categories: normal vision ( 6/18, controls only), moderate visual impairment (,6/ 24, 6/60), severe visual impairment (,6/60, 3/60), blind (,3/60, .PL) and perception of light (PL). Vision-related quality of life Validity and reliability of the WHO/PBD VF20 (minus one item) were evaluated by standard psychometric methods, including item acceptability, internal consistency, test���retest reliability, within-scale analyses and analyses against external criteria, and using thresholds specified by Lamping et al.21 Analyses were conducted on data from cases only, except for testing the ability Table 1 Characteristics of cases and controls Cases, n (%) Controls, n (%) Age- and sex- adjusted OR (95% CI) Age (years) 50���59 9 (4.6) 11 (8.6) Baseline 60���69 34 (17.4) 30 (23.4) 1.3 (0.5 to 3.8) 70���79 66 (33.7) 51 (39.8) 1.6 (0.6 to 4.1) 80 87 (44.4) 36 (28.1) 2.9 (1.1 to 7.8) Sex Male 79 (40.3) 51 (39.8) Baseline Female 117 (59.7) 77 (60.2) 1.0 (0.6 to 1.6) Education None 148 (76.7) 74 (58.7) Baseline Some 45 (23.3) 52 (41.3) 0.4 (0.2 to 0.7) Literacy Cannot read 148 (75.9) 65 (50.8) Baseline Can read 47 (24.1) 63 (49.2) 0.3 (0.1 to 0.5) Marital status Single/widowed 110 (56.7) 59 (46.8) Baseline Married 84 (43.3) 67 (53.2) 0.7 (0.4 to 1.2) Socioeconomic status 1 (poorest) 57 (29.8) 22 (17.9) Baseline 2 52 (27.2) 27 (22.0) 0.8 (0.4 to 1.6) 3 46 (24.1) 35 (28.5) 0.5 (0.3 to 1.0) 4 (least poor) 36 (18.9) 39 (31.7) 0.4 (0.2 to 0.8) Visual acuity 6/18 0 (0.0) 128 (100.0) N/A ,6/24, 6/60 78 (39.8) 0 (0.0) ,6/60, 3/60 41 (20.9) 0 (0.0) ,3/60, .PL 36 (18.4) 0 (0.0) PL 41 (20.9) 0 (0.0) Mean (95% CI) Mean (95% CI) p Value Vision-related quality of life* Overall eyesight 3.9 (3.9 to 4.1) 2.1 (2.0���2.3) ,0.001 General functioning 43.6 (41.5 to 45.8) 17.8 (16.6���19.1) ,0.001 Psychosocial 12.2 (11.4 to 12.9) 5.5 (5.0���6.0) ,0.001 Self-rated health�� 47.6 (45.1 to 50.1) 59.4 (56.3���62.5) ,0.001 PL, perception of light. Some data were missing. *Higher score denotes poorer quality of life. ��Higher score denotes better self-rated health. 928 Polack, Kuper, Mathenge, et al www.bjophthalmol.com on 30 May 2008 bjo.bmj.com Downloaded from