Importance of population-based studies in clinical practice

In the last decade, there have been reports on the prevalence of glaucoma from the Vellore Eye Survey, Andhra Pradesh Eye Diseases Survey, Aravind Comprehensive Eye Survey, Chennai Glaucoma Study and West Bengal Glaucoma Study. Population-based studies provide important information regarding the prevalence and risk factors for glaucoma. They also highlight regional differences in the prevalence of various types of glaucoma. It is possible to gather important insights regarding the number of persons affected with glaucoma and the proportion with undiagnosed disease. We reviewed the different population-based studies from India and compare their findings. The lacunae in ophthalmic care that can be inferred from these studies are identified and possible reasons and solutions are discussed. We also discuss the clinical relevance of the various findings, and how it reflects on clinical practice in the country. Since India has a significantly high disease burden, we examine the possibility of population-based screening for disease in the Indian context.

Comparison of Humphrey MATRIX and Swedish interactive threshold algorithm standard strategy in detecting early glaucomatous visual field loss

Purpose:

The aim of this study was to compare the Humphrey MATRIX visual field (frequency doubling technology threshold) and Swedish interactive threshold algorithm (SITA) standard strategy white on white perimetry in detecting glaucomatous visual field loss.

Material and Methods:

Twenty-eight adult subjects, diagnosed to have glaucoma at a tertiary eye care hospital, who fulfilled the inclusion criteria, were included in this prospective study. All subjects underwent a complete ophthalmic examination. Subjects with glaucomatous optic disc changes underwent repeat perimetric examination on the same day with the Humphrey visual field analyzer (HFA II) and Humphrey MATRIX, the order of testing being random. Only reliable fields, where the HFA results corresponded to the disc changes were considered for analysis. A cumulative defect depth in each hemifield in both HFA and MATRIX reports was calculated.

Results:

Thirty-seven eyes of 24 subjects had reliable fields corresponding to optic disc changes. The mean age of the subjects was 56 ± 12 years. There were 12 males and 12 females. The test duration was significantly less on the MATRIX, mean difference in test duration was −81 ± 81.3 sec (p < 0.001). The mean deviation and the pattern standard deviation between the two instruments showed no significant difference (p = 0.55, p = 0.64 respectively) and a positive correlation coefficient of 0.63 and 0.72 respectively. Poor agreement was found with the glaucoma hemifield test.

Conclusion:

The Humphrey MATRIX takes less time in performing the test than SITA Standard and shows good correlation for mean deviation and pattern standard deviation. However, the glaucoma hemifield test showed poor agreement. The Humphrey MATRIX diagnoses were similar to established perimetric standards.

Comparison of refractive errors and factors associated with spectacle use in a rural and urban South Indian population

PURPOSE

To compare the prevalence of refractive errors and factors associated with spectacle use in a rural and urban south Indian population.

MATERIALS AND METHODS

Four thousand eight hundred subjects (age> 39 years) each from rural and urban Tamil Nadu were enumerated for a population-based study. All participants underwent a complete ophthalmic evaluation including best-corrected visual acuity (BCVA), objective and subjective refraction. Out of 3924 rural responders 63.91% and out of 3850 urban responders 81.64% were phakic in the right eye with BCVA of 20/40 or better and were included in the study. Association of spectacle use and refractive errors with different parameters were analysed using logistic regression.

STATISTICAL ANALYSIS

Chi square, t test, Chi square for trend and Pearson's correlation coefficient were used for analysis.

RESULTS

Spectacle use was significantly higher and positively associated with literacy and employment in the urban population. The age and gender-adjusted prevalence of emmetropia, myopia of spherical equivalent (SE) < or =-0.50 diopter sphere (DS), high myopia (SE < or =-5.00DS), hyperopia (SE> 0.50DS) and astigmatism < or = 0.50 diopter cylinder (DC) were 46.8%, 31.0%, 4.3%, 17.9% and 60.4% respectively in the rural population and 29.0%, 17.6%, 1.5%, 51.9%, 59.1% respectively in the urban population. The prevalence of emmetropia decreased with age ( p p = 0.001) and were associated with nuclear sclerosis ( p = 0.001) in both populations. Hyperopia was commoner among women than men ( p = 0.001); was positively associated with diabetes mellitus ( p = 0.008) in the rural population and negatively with nuclear sclerosis ( p = 0.001) in both populations.

CONCLUSION

Spectacle use was found to be significantly lower in the rural population. The pattern of refractive errors was significantly different between both populations.