Abstract
Purpose: :
Corneal hysteresis (CH) has been associated with visual field damage in glaucoma and is related to the velocity of perimetric glaucoma progression. We undertook this investigation to determine whether CH is related to structural markers of glaucoma damage using high-definition optical coherence tomography (HD-OCT).
Methods: :
Patients under evaluation for glaucoma were considered for inclusion in this retrospective study. We included eyes that had been tested with HD-OCT (Cirrus, Carl Zeiss Meditec, Dublin, CA) and had bilateral baseline corneal hysteresis measurement with the ocular response analyzer (ORA; Reichert, Inc., Buffalo, NY). Included HD-OCT optic nerve head cube scans had good alignment and image acquisition and signal strength ≥ 6. Each patient had digital stereophotos of the optic nerve (Topcon Co., Tokyo, Japan), a full ophthalmic examination and >1 reliable and repeatable visual field test (24-2 SITA standard automatic perimetry with the Humphrey Field Analyzer II). Pearson and partial correlation adjusting for age were preformed to examine the strength of association between CH and variables of interest using data from one eye per patient. Generalized estimating equations were then used to construct simple and multiple linear models adjusting for intereye correlation among patients and using semi-robust variance estimation.
Results: :
We identified 287 eyes of 161 patients meeting our inclusion criteria. Our sample consisted of 145 (50.5%) open angle glaucoma patients and 116 (40.4%) glaucoma suspects. While Pearson correlations were modest overall, CH best correlated with average retinal nerve fiber layer (RNFL) thickness in µm (r=0.20) followed by mean deviation (MD) in dB (r=0.19) and vertical cup to disc ratio (r=-0.15). Simple linear models showed that CH varied as a function of MD (ß=0.06, 95% CI 0.02, 0.09; p=0.001) as well as of average RNFL thickness (ß=0.02, 95% CI 0.00, 0.03; p=0.006). In a multivariable analysis including MD, age and average RNFL thickness, MD (p=0.01) and age (p<0.001) retained significant associations with CH.
Conclusions: :
In patients under evaluation and treatment for glaucoma, CH is more closely related to visual field MD than to structural markers of glaucoma damage as measured by HD-OCT.
Keywords: imaging/image analysis: clinical • nerve fiber layer • optic disc