Third National Survey on Blindness
Leo D.P. Cubillan, MD, MPH Evangeline O. Olivar-Santos, MD, MHA
The Prevention of Blindness Program (PBP) and Vision 2020 Philippines of the Department of Health (DOH) have been implemented to address avoidable causes of blindness. Population-based surveys every 5 to 8 years are utilized to monitor and evaluate these programs. The third National Survey on Blindness in the Philippines was conducted from October 2001 to May 2002 to determine the prevalence and major causes of visual impairment in the Philippines at both the national and regional levels. The results were also compared with those of the first (1987) and second (1995) surveys.
A nationally representative sample was selected based on multistage, cluster, random sampling. The 16 administrative regions of the Philippines served as the cluster sites where 9 villages each were randomly sampled using probability proportional to size procedures. Visual acuity (VA) with or without glasses was determined using a modified Snellen acuity chart. Anterior-eye examination was performed with a penlight. The posterior-eye segment was examined with an ophthalmoscope. When indicated, eye pressures were obtained with the Schiotz tonometer. The World Health Organization’s (WHO) definitions of blindness and low vision were used to categorize visual impairment. Diagnoses of eye disease were in accordance with the International Classification of Diseases.
Questionnaires were entered and analyzed using Epi Info 6.0. National and regional prevalence rates and 95% confidence intervals were computed. Chi-square test was used to detect differences among regions and compare results with the 1987 and 1995 blindness surveys.
A total of 29,888 people in 6,757 households were enumerated, of which 24,624 (82.39%) were examined. Nationwide, the prevalence of visual impairment (VA worse than 6/18 in the better eye) is 4.62%; the prevalence of bilateral blindness [VA less than counting finger (CF) at 3 meters] is 0.58%, monocular blindness is 0.71%, bilateral low vision (VA worse than 6/18 but equal to or better than CF at 3 meters) 1.43%, and monocular low vision 0.87%. Regionally, the prevalence of blindness is from 0.16% to 1.08% and low vision 0.60% to 4.07%.
Cataract is the most common cause of blindness (62% of all persons with bilateral blindness), and error of refraction (53%) is the most common cause of low vision.
The current prevalence of bilateral blindness is 46% lower than the 1987 prevalence (1.07%, p < 0.001) and 17% lower than the 1995 prevalence (0.70%, p = 0.108).
There are over 400,000 bilaterally blind people in the Philippines, of which 62% is due to cataract. The prevalence of blindness has been reduced compared with the 1987 and 1995 national surveys. Vision 2020 Philippines has contributed to this reduction. With continued support and implementation of the blindnessprevention program, the prevalence is expected to be reduced to the WHO target of less than 0.5% by year 2020.
Keywords: Blindness, Visual impairment, Cataract, Low vision, Error of refraction