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Tiffany L Huang, Matthew P Ohr, Ashraf Mahmoud, Cynthia J Roberts; Comparison of Pressure-Volume Ratios in Diabetic vs. Normal Eyes. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1075.
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To date, little is known regarding the biomechanical response of the eye to diabetes or the relationship of such changes to clinical retinopathy. In this study, we use static pressure-volume (PV) ratios as a surrogate for ocular rigidity and compare it among subjects with diabetic retinopathy (DR), diabetes without retinopathy (DIA), and controls (NL).
A total of 240 subjects (475 eyes) were analyzed; 150 NL (n=297 eyes), 45 DIA (n=90 eyes), and 45 DR (n=88 eyes). Intraocular pressure (IOP) was obtained using corneal compensated IOP from Ocular Response Analyzer, Goldmann applanation tonometry, PASCAL dynamic contour tonometer, and Corvis ST. Anterior chamber volume (ACV) was measured using the Pentacam. Four PV ratios were calculated using the IOP obtained from the different methodologies over ACV. PV was correlated to two stiffness parameters (SP) calculated as load over displacement, from undeformed state to first applanation for cornea (SP-A1), and from applanation to highest concavity for sclera (SP-HC) using regression analysis. ANCOVA was performed to compare PV between groups with pachymetry and age as covariates. Significance threshold was p<0.05.
PV ratios were significantly greater in DR compared to DIA and NL using all 4 methods of measuring IOP, with no difference between DIA and NL. For SP-HC, DR was significantly stiffer compared to DIA (<0.0001) and NL (<0.0001), with no difference between DIA and NL (p=0.19). No relationship was observed for SP-A1 among the 3 groups. PV ratio had stronger correlation to SP-HC (R2=0.39, p<0.0001) than SP-A1 (R2=0.15, p=0.0002), with the strongest relationship noted in DR group.
In this report, we used PV ratios as a surrogate for ocular rigidity. Our results showed greater PV ratios in DR than both DIA and NL. Furthermore, there is high correlation between PV ratio and the scleral stiffness parameter. Clinically, the scleral stiffness parameter can be thought of as the entire posterior ocular shell, encompassing structures beyond the sclera including the retina, choroid, and supporting vasculature and connective tissue. Our results suggest eyes with DR have stiffer posterior ocular shell and we are currently investigating potential mechanisms.
This is a 2021 ARVO Annual Meeting abstract.
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