Abstract
Purpose :
The role of the ocular pulse amplitude (OPA), which is the difference in measured IOP during the diastolic and systolic cardiac cycle, in glaucoma pathogenesis is under-studied due to the limited methods for measuring OPA. We present a novel method for measuring OPA using standard ophthalmic equipment and fixed-force Goldmann Applanation Tonometry (GAT).
Methods :
The methods for automated fixed-force GAT have been previously described.1 Briefly, an iPod Touch clamped to the ocular of a standard slit lamp microscope (Fig A) recorded the applanation mires (Fig B) created with the GAT set at a fixed force. IOP values from each frame of the video were calculated from the mire diameters (Fig C) and plotted over time (Fig D). In this post hoc analysis, we analyzed previously collected videos used for validation of the automated GAT method. The right eyes of subjects diagnosed as POAG or glaucoma suspect (GS) were included. The OPA was calculated by measuring the difference in IOP between the upper and lower IOP measurements in each cycle and taking the mean of these differences. The OPA of POAG eyes were compared to GS eyes.
Results :
41 POAG eyes and 20 GS eyes were included. Mean age (67.5±8.2 vs 66.5±13.5 years), IOP (14.5±4.8 vs 16.9±4.6 mmHg) and CCT (535±39 vs 550±32 µm) for POAG vs GS eyes did not differ significantly (p=0.71, 0.08, 0.13, respectively). OPA was found to be decreased in POAG eyes (1.18±0.7 mmHg) compared with GS eyes (1.62±0.94 mmHg) (p=0.05, t-test). A significant correlation between OPA and IOP was found (r=0.62, p<0.0001) while no significant correlation was found between OPA and CCT (r=0.14, p=0.30) and OPA and age (r=-0.01, p=0.91).
Conclusions :
Preliminary measurements of OPA using automated fixed force GAT are promising. This method is easily incorporated into standard ophthalmic equipment and may become a tool to improve our understanding of the role of OPA in ocular disease.
This is a 2021 ARVO Annual Meeting abstract.