Diurnal Variation of Central Corneal Thickness (CCT) and Intraocular Pressure (IOP) in Subjects with Pseudoexfoliation Glaucoma, Pseudoexfoliation Syndrome and in Normal Subjects

Author(s): Prasanta Kumar Nanda1 , Bishnupriya Khuntia2 , Shradha Pattnaik3

BACKGROUND Pseudoexfoliation syndrome (PXF) is an age-related systemic disease characterized by synthesis and accumulation of abnormal fibrillar material throughout anterior segment of eyes. PXF along with raised IOP and optic nerve head changes leads to pseudoexfoliation glaucoma (PXFG). PXF and PXFG are characterized by thinner corneas with large 24-h IOP fluctuations. We wanted to evaluate if any variation occurs in diurnal central corneal thickness (CCT) and intraocular pressure (IOP) between eyes with pseudoexfoliation syndrome (PXF), pseudoexfoliation glaucoma (PXFG) and in normal subjects. METHODS This is a prospective study conducted among 104 subjects (M=54, F=50). Amongst those, 30 patients had PXF in one eye, 3 patients in both the eyes and 24 patients had PXFG in one eye. Remaining 47 were taken as controls for the study. Testing included CCT and IOP measurement at four different times of the day (8.00 am; 11 am; 2 pm; 5 pm). RESULTS PXFG eyes showed a significantly thinner overall mean CCT (497 µm) followed by PXF eyes (518 µm) as compared to controls with a mean CCT of 527 µm. The mean overall IOP in PXFG (23.6 mmHg) was significantly higher as compared to PXF (14.6 mmHg) and the control group (14.2 mmHg). Furthermore, a significant reduction in CCT and IOP occurred in PXFG group from 8.00 am to 5.00 pm. A significant association between IOP and CCT was found in PXFG eyes. CONCLUSIONS A significantly thinner mean CCT shows the importance of measuring CCT on a regular basis having such clinical setup in order to avoid falsely low IOP measurement in a high-risk glaucoma population. Moreover, a significant correlation between IOP and CCT in PXFG eyes suggests that the decrease in mean CCT that occurred from 8 am to 5 pm may partly be responsible for the similar pattern of decrease in IOP from 8 am to 5 pm with mean CCT and IOP being highest in the morning within three hours of waking up and thereafter decreasing during the day.