Context: Glaucoma, a progressive optic neuropathy, is one of the leading causes of irreversible blindness in the adult population worldwide. Primary open angle glaucoma (POAG) is the most reported type of glaucoma in various worldwide population-based studies. Elevated intraocular pressure is a major risk factor for POAG. In addition, there is growing evidence that other risk factors like age, gender, race, refractive errors, heredity, and systemic factors may play a role in glaucoma pathogenesis. High myopes have always been at a higher risk of POAG. Early detection of glaucoma in myopes can reduce blindness caused by glaucoma. For that, it is essential to know the association of glaucoma in different grades of myopia.
Aims: To study myopia as a risk factor for primary open angle glaucoma and find the association of different grades of myopia with glaucomatous changes at a Tertiary Care Centre in Central Gujarat, India.
Setting and Design: This is a descriptive analytical study which was conducted at Shree Krishna Hospital, Karamsad, Anand, Gujarat which is one of the largest tertiary Care Centres in Gujarat, India.
Materials and Method: Total of 100 myopic patients between the age of 40 years to 70 years, from general eye Out-Patients Department (OPD) were included as subjects for this study. Patients were divided in three subgroups based on grade of myopia into mild (<3D), moderate(3D-6D) and high(>6D). A comprehensive ophthalmic examination including best corrected visual acuity, intraocular pressure (IOP), gonioscopy, pachymetry, axial length, perimetry, disc evaluation and optical coherence tomography (OCT) was done, to evaluate these myopic patients for glaucoma.
Statistical Analysis: Chi square test was used to find association between myopia grade and different categorical variables. ANOVA was used to compare mean IOP with myopia grade. Post-hoc Tukey test was used for pairwise comparison. A P value <0.05 was considered statistically significant. Statistical software STATA 14.2 was used for data analysis. P-value of individual cell was based on Holm-Bonferroni correction.
Results: Different grades of myopia were compared with IOP, disc evaluation, visual field analysis, OCT parameters: ganglion cell complex (GCC) volume and retinal nerve fiber layer (RNFL) thickness of eyes in patients. When each subgroup of myopia was separately compared with these parameters, all the parameters showed significant association with P-value being <0.001. However, the IOP did not show statistical significance in different grades of myopia, with P-value being 0.1.
Conclusion: From this study, we conclude that glaucomatous changes on optic nerve head (ONH) evaluation, Visual Field (VF) analysis, OCT scans of RNFL and GCC were highest in high myopia but were also present in low and moderate grades of myopic patients. IOP value in different grades of myopia did not show statistical significance, however, the values were higher in high myopia, followed by moderate and then mild myopia. The evaluation of glaucoma in myopic eyes requires collaborative approach, where measuring IOP still holds major importance and is a guiding factor to start treatment, when other factors put us in dilemma.