The census from year 2000 recorded that Singaporean Indians are predominantly persons with ancestry traced to the southern region of India (from the states of Tamil Nadu and Kerala) and account for 66.6% of the Indian community in Singapore.
25 A detailed analysis of our study sample revealed that the proportion of subjects with a South Indian ancestry was close to 90%. This aspect has important implications because our data become directly comparable to recent studies on subjects from this region in India, such as the Aravind Comprehensive Eye Survey (ACES),
22 Chennai Glaucoma Study (CGS),
12,13 and the Andhra Pradesh Eye Disease Study (APEDS).
14 A compilation of comparative data from glaucoma prevalence from various parts of southern India is shown in
Table 5. The POAG prevalence in our study has a close match to the prevalence noted in ACES with both reporting a prevalence of 1.2%.
22 An important aspect of this data is that the population sample in ACES was derived from a predominantly rural setting. In comparison, the CGS reported age-standardized POAG prevalence of 1.57% in the rural arm of their study and APEDS reported a prevalence of 1.6%.
12,14 Although the prevalence of POAG in our sample was lower, the trend follows that of the rural arms of the CGS and APEDS and of note, there is an overlap of the confidence intervals (95% CI, 0.89–1.73 vs. 1.19–1.95 [CGS]; 1.13–2.06 [APEDS]).
12,14 The overall prevalence of POAG in our study samples correspond to the prevalence noted in the rural samples of the ACES, CGS, and APEDS, which is intriguing. Though the Singaporean Indians by all means would be considered highly urbanized, the prevalence of POAG did not match the urban South Indians of the CGS (3.46%) and the APEDS (4.0%). The authors from the CGS study attributed the discrepancy of POAG prevalence between their rural and urban populations to significant socioeconomic and lifestyle differences.
12 Interestingly, these aspects of urbanization did not seem to affect the prevalence of POAG among the Singaporean Indians, who may be considered to have a higher socioeconomic status compared to the rural and urban counterparts in the CGS or the APEDS. The prevalence of PACG was also low at 0.12% and matched that of the Malay subjects in Singapore but was far lower than that reported in native southern Indian population (0.5%–1.8%).
13,14,22 The urban subjects in the CGS
13 and APEDS
14 reported rates of 0.80% and 1.8%, respectively, whereas the prevalence in the rural subjects of ACES,
22 CGS,
13 and APEDS
14 study was 0.5%, 0.85%, and 0.7%, respectively. We have to acknowledge the likelihood of the disparities between the urban glaucoma prevalence rates noted between CGS, APEDS, and our study could be due to differences in methodologies. The definitions of glaucoma in our study and the CGS were based on the ISGEO
18 ; however, in the CGS, gonioscopy and automated perimetry were done for every patient, and this could have contributed to a higher yield of suspected glaucoma cases. Further, factors that could contribute to this large variation could be subjective differences in gonioscopic assessment and the proportion and mean age of nonresponders. We noted that there were 1094 (32.1%) nonresponders for the study; these subjects had a significantly higher mean age than the responders (61.1 vs. 57.8 years;
P < 0.001), and this could have also partially contributed to the low prevalence rate. We also considered the possibility of a higher cataract surgery rate in Singapore as a potential cause for lower prevalence of PACG but found that the age-adjusted cataract surgery rates were marginally lower compared to CGS (9.7% vs. 10.16%)
26 and far lower than that reported in APEDS (9.7% vs. 14.6%).
27