Central Corneal Thickness Variation Across Glaucoma Subtypes And Its Association With Disease Severity

Our study investigates the relationship between central corneal thickness (CCT) and different glaucoma types, along with its association with glaucoma severity. Glaucoma, the second leading cause of irreversible blindness worldwide, prompts the need for early detection and risk factor identification. CCT serves as a crucial parameter influencing intraocular pressure measurement. Thinner CCT has been previously linked to a higher risk of primary open-angle glaucoma. Our objectives include determining the correlation between CCT and glaucoma subtypes as well as glaucoma severity using clinical examination, perimetry, and OCT. Our study findings aim to enhance understanding of glaucoma pathophysiology and inform clinical management strategies.

This study has been conducted in the glaucoma clinic in the outpatient department of a hospital with a dedicated Ophthalmology department. Clearance from the institutional Ethics Committee as well as informed consent has been taken from all study participants prior to enrolment. 

Patients were screened and enrolled in the study as per the inclusion criteria. The sixty participants included were classified into four main groups: Primary open-angle glaucoma (POAG), Normal tension glaucoma (NTG), Primary angle closure glaucoma (PACG), and Pseudoexfoliative glaucoma (PXF). Demographics (age and sex), best corrected visual acuity (BCVA), intraocular pressure, central corneal thickness (CCT), vertical cup to disc ratio (CDR), visual field mean deviation (MD) pattern standard deviation (PSD), and retinal nerve fibre layer (RNFL) thickness were recorded. Glaucoma control via single/double drop therapy and systemic status of patients was noted. Results were recorded in a spreadsheet and analysed as the data was collected.

In our study population, CCT was found to be the thinnest in patients with Normal Tension Glaucoma. Mean measurements of CCT for our groups were 523.5 ± 30.7 μm (POAG), 520.5 ± 45.7 μm (NTG) 528.6 ± 37.3 μm (PACG), and 534.4 ± 30.5 μm (PXF )and showed no significant difference among glaucoma subtypes. As regards IOP and RNFL thinning, the difference between study groups observed was statistically significant (p < 0.001 and p =0.004 respectively). Using Pearson’s correlation coefficient and linear regression,decrease in CCT is seen with an increase in age, associated with decrease in IOP, BCVA, RNFL thickness and associated with an increased vertical CDR. An increase in CCT is associated with an improvement in the visual field mean deviation

Central corneal thickness measurement plays an important role in diagnosis and management of glaucoma. In our study, although the CCT measurements did not show a significant difference in different glaucoma subtypes, we successfully established a relationship between CCT and severity of glaucoma. Through our study, the correlation of various parameters with central corneal thickness measurements allows the ophthalmologist to better understand the prognosis and progression of the disease and make informed decisions regarding treatment options. Using the study parameters, clinicians can also be made aware of possible visual outcomes and anticipate potential complications, especially in glaucoma patients undergoing cataract/ocular surgery.