Comparison of the corneal biomechanical properties with the Ocular Response Analyzer^® (ORA) in African and Caucasian normal subjects and patients with glaucoma

Abstract

ABSTRACT.Purpose: To compare corneal hysteresis (CH) and corneal resistance factor (CRF) measured with the Ocular Response Analyzer Ò tonometer (ORA) between (i) African normals and treated primary open-angle glaucoma (POAG) patients and (ii) between normals and treated POAG Caucasians. To analyse the correlation of CH and CRF with visual field (VF) defects in the two groups.Methods: This comparative study included 59 African (29 (POAG), 30 normals) and 55 Caucasians (30 POAG and 25 normals) subjects. Goldmann applanation tonometry (GAT) and ORA measurements were performed in a randomized sequence. Visual field was tested with the Swedish interactive threshold algorithms standard strategy of the Humphrey perimeter. Hoddap classification was used to estimate the severity of VF defects.Results: Primary open-angle glaucoma Africans were younger than POAG Caucasians (p < 0.001). Goldmann applanation tonometry and central corneal thickness (CCT) did not differ significantly between the four subgroups. African normals had lower CH than Caucasian controls (p < 0.001). CH was 9.2 ± 1.1 and 8.3 ± 1.7 mmHg respectively in POAG Caucasians and Africans (p < 0.001). African controls had higher ORA corneal-compensated intraocular pressure (IOPcc) than Caucasian controls (p < 0.001). Primary open-angle glaucoma Africans had higher IOPcc values than Caucasian POAGs (p < 0.001). CH and IOPcc were associated with race (p < 0.001) but not with CCT. Based on mean deviation values (MD), POAG Africans had more severe VF defects. CH was correlated with MD (r = 0.442; p = 0.031) and severity of VF defects only in POAG Africans (r = )0.464; p = 0.013).Conclusions: African normal subjects and POAG patients had an altered CH, which is associated with a significant underestimation of GAT IOP. This may potentially contribute to the earlier development and greater severity of glaucoma damage in Africans compared with Caucasians at diagnosis.

Variation in corneal hysteresis and central corneal thickness among black, hispanic and white subjects

“…With greater statistical power in the present study, it was not surprising that we observed a significant difference in CH between blacks and whites that was independent of CCT. This result is similar to that of Detry‐Morel and colleagues who observed lower average CH values in Africans compared with Caucasians and found this relationship to exist independent of CCT in both healthy and glaucomatous eyes (Detry‐Morel et al. 2011).…”

“…2011). However, their sample size was relatively small, and given that 75% of their African subjects were natives of Congo, the external validity of the results is limited for many clinicians (Detry‐Morel et al. 2011).…”

“…Much of the past research has looked at differences in CH among normal subjects and those diagnosed with glaucoma (Leite et al. 2010; Detry‐Morel et al. 2011).…”

Corneal thickness after overnight wear of an intraocular pressure fluctuation contact lens sensor

“…This study did not assess biomechanical properties such as corneal hysteresis as a complement to CCT measurements. These may affect CLS readings, and therefore, further research including assessment of corneal hysteresis may be of interest (Alhamad & Meek 2011), (Detry‐Morel et al. 2011).…”

Corneal Biomechanical Properties in Different Ocular Conditions and New Measurement Techniques

“…In contrast, some studies reported the lack of association between CH and both GAT and IOPg [30, 64, 65], suggesting that CH is independent of IOP, while other studies suggest a relationship between CH and IOP. CH has been shown to decrease as the IOPcc increases [30, 46, 66, 67]. Kamiya et al [66] found IOP as a significant explanatory variable relevant to CH, while González-Meijome et al [68] found a significant correlation between changes in IOP and changes in CH during the day in healthy eyes.…”