Repeatability of contrast testing and the comparison of contrast sensitivity between normal and glaucomatous eyes

Abstract

Purpose : The full contrast sensitivity function (CSF) describes different aspects of visual performance including: peak contrast sensitivity (CS) – 1/contrast threshold assessed at medium-to-large optotype sizes – and contrast acuity (CA) – optotype size thresholds assessed at high-contrast. CS testing has had limited use as a visual outcome, due to imprecision in the clinical setting. The purpose of this study was to (i) evaluate CS differences in normal and impaired vision, as assessed with the novel qCSF tester (Adaptive Sensory Technology), (ii) to evaluate and compare repeatability of CS testing in normal and impaired vision.

Methods : qCSF data was obtained in 40 eyes (20 normal subjects) and 60 eyes (30 glaucoma subjects) with an average visual field (VF) loss of -9.5 (SD=8.6) dB assessed by Humphrey 24-2. CS data was collected in monocular conditions, with worse-seeing eye retested for glaucoma subjects and both eyes retested for normal subjects. Re-test measurements were obtained to assess repeatability and precision. CS metrics were derived from the qCSF, including area under the log CSF (AULCSF) curve and CA, the high spatial frequency at which sensitivity=0.

Results : In normal subjects AULCSF (mean=1.58;SD=.15), and CA (mean=1.40;SD=.09) values were consistently higher and less variable than those observed in glaucoma: AULCSF (mean=.88;SD=.47), and CA (mean=1.02;SD=.33). The coefficients of repeatability for AULCSF and CA were .15 and .13 decimal log units for normal vision and .11 and .12 log units for glaucoma, respectively. The area under the Receiver Operating Characteristic (ROC) for discriminating eyes with normal and impaired vision was 93% for AULCSF and 91% for CA.

Conclusions : This study demonstrates that qCSF yields better contrast sensitivity in normal eyes, compared to glaucomatous eyes. Of note, repeatability is comparable in both groups, for both AULCSF and CS metrics. The qCSF exhibits potential as a clinical trial endpoint, as contrast sensitivity has been previously shown to affect visual quality of life.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

The CSF, which defines visual performance over stimulus dimensions, summarized by AULCSF and CA.

 

Bland-Altman plots presenting AULCSF and CA test-retest scores, and coefficients of repeatability (COR) for normal (blue) and glaucomatous (red) eyes.