Low Corneal Hysteresis Values a Marker for Capillary Density Loss in Glaucoma

Lowered corneal hysteresis (CH) values may be a marker for more rapid whole image capillary density (wiCD) loss, a study published in Ophthalmology Glaucoma shows.

Patients (N=134) with preperimetric glaucoma (n=43; n=52 eyes) and primary open-angle glaucoma (POAG; n=91; n=122 eyes) were recruited for the Diagnostic Innovation in Glaucoma Study (ClinicalTrials.gov Identifier: NCT00221897) at the University of California, San Diego. Eyes were evaluated using optical coherence tomography (OCT) angiography and spectral-domain OCT at 4 or more occasions for 2 years or longer. Clinicians assessed baseline CH, intraocular pressure (IOP), and mean deviation (MD) for their potential utility as markers for wiCD loss or circumpapillary retinal nerve fiber layer (cpRNFL) thinning at follow-up. 

The study included glaucoma suspects (mean age 68.6, 23 women, 20 men) and POAG diagnosed patients (69.9 years, 64 women, 27 men). At baseline, the glaucoma suspect cohort had a mean CH value of 9.6 mm Hg, mean IOP of 16.6 mm Hg, and 24-2 mean deviation of -0.20 and the POAG cohort had a mean CH value of 9.5 mm Hg, mean IOP of  14.6 mm Hg, and 24-2 mean deviation of -4.68 dB.

In the multivariate analysis, predictors for the percentage of wiCD loss per year included ethnicity (estimate, -2.70; P <.001) and baseline MD (estimate, -0.60; P <.001) and the interactions between ethnicity and time (estimate, -0.27; P =.025); average IOP during follow-up and time (estimate, -0.19; P =.007); CH and time (estimate, -0.24; P =.050); number of IOP-lowering medications and time (estimate, -0.09; P =.043); and average IOP during follow-up, CH, and time (estimate, 0.02; P =.006).

The predictors for cpRNFL thinning include ethnicity (estimate, -9.33; P =.005), baseline MD (estimate, -1.96; P <.001), and the age-by-time interaction (estimate, 0.20; P =.036).

Overall, the investigators observed a nonsignificant, but clinically meaningful, effect of baseline MD and time on CH (P =.103), indicating that severity of glaucoma affected the rate wiCD decline.

The major limitation of this study was that approximately 30% of OCT angiography images were of poor quality or contained artifacts and were removed from this analysis.

“Lower CH values were associated with faster rates of wiCD loss. The association between lower CH and rates of wiCD loss was more pronounced in patients with more severe glaucoma damage at baseline,” the researchers explain. “The synergistic effect of lower baseline CH values and higher average IOP during follow-up was associated with faster rates of wiCD loss. Evaluation of ORA parameters add clinically useful information for monitoring glaucoma.”

Disclosure: Multiple study authors declared affiliations with the biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.