Lower corneal hysteresis increases risk for visual field impairment in glaucoma
Corneal hysteresis was a significant risk factor for glaucomatous central and peripheral visual field progression, according to a study published in the American Journal of Ophthalmology.
“Prior studies have found lower CH [corneal hysteresis] to be associated with an increased rate of functional and structural deterioration in glaucoma patients,” Alireza Kamalipour, MD, MPH, of the Shiley Eye Institute at the University of California, San Diego, and colleagues wrote. “In this study, the event-based multivariable analysis showed that 1 mm Hg lower CH corresponds to a 35% increase in the odds of central VF [visual field] progression after adjusting for other covariates.”
In an observational cohort study, Kamalipour and colleagues analyzed 143 participants from two prospective longitudinal studies to evaluate optic nerve structure and visual function in glaucoma. More than 75% of participants were already on ocular hypotensive eye drops at study onset.
Investigators monitored participants for an average of 4.8 years, during which time they conducted annual comprehensive ophthalmologic examinations, as well as semiannual assessments of automated perimetry (a minimum of five 10-2 and 24-2 VF tests) and IOP.
Of 103 patients with glaucoma and 40 patients with suspected glaucoma (mean age, 68.4 years; 50.3% women), eyes with glaucoma had lower baseline IOP, lower mean IOP during follow-up, worse baseline 24-2 and 10-2 mean deviations (MDs) and higher baseline 24-2 and 10-2 pattern standard deviations (PSDs) than glaucoma suspect eyes (all P < .05).
In the univariable trend-based analysis, lower baseline CH was associated with 10-2 and 24-2 VF progression, while in the multivariable trend-based analyses, lower CH was associated with a faster rate of decline in 10-2 MD but not with 24-2 MD.
“Given the substantial influence of central VF impairment on the quality of life, clinicians should consider using CH to assess the risk of progression in primary open-angle glaucoma patients, including those with early disease,” Kamalipour and colleagues concluded.
Perspective
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Glaucoma patients can and do have central defects early in the disease process. This type of damage has a greater impact on quality of life and should therefore be vigilantly guarded against. How do we identify those patients at risk for early central vision loss before structural or functional damage is evident? Structurally, inferior temporal retinal nerve fiber layer/ganglion cell complex loss is the clearest indicator corresponding functionally to superior central visual field loss. Research from UC San Diego suggests that corneal hysteresis (CH) may be an “early warning” biomechanical marker for central vision loss risk much like pachymetry is employed to highlight glaucoma risk.
Previous studies found that low CH was a predictor of faster retinal nerve fiber layer decline and global VF progression. The cornea’s ability to dampen pressure (CH) may also be a reflection of the optic nerve’s capacity to do the same. Such inherent risk assessment could be a further qualifier to true measurement of transcorneal pressure. This study by Kamalipour and colleagues showing low CH was modestly associated with earlier and more profound central loss provides further justification for biomechanical measurements to enter the mainstream. Individualized risk assessment for disease progression unlocked by CH may be the next big thing in glaucoma diagnosis.
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