Contrast sensitivity deficits in patients with mutation-proven inherited retinal degenerations

Abstract

BackgroundPatients with retinal diseases frequently complain of poor visual function even when visual acuity is relatively unaffected. This clinical finding has been attributed to deficits in contrast sensitivity (CS). The purpose of our study was to evaluate the CS in patients with clinical and genetic diagnosis of inherited retinal degeneration (IRD) and relatively preserved visual acuity.MethodsSeventeen patients (30 eyes) with IRD and visual acuity of 20/40 or better, and 18 controls (18 eyes) without any ocular condition underwent slit lamp examination, visual acuity testing via standard Snellen chart testing, CS testing via the Quick Contrast Sensitivity Function (QCSF), and Spectral Domain Optical Coherence Tomography (SD-OCT). CS were measured at 1.0, 1.5, 3.0, 6.0, 12.0, and 18.0 cycles per degree (cpd). T tests with general estimated equations were used to compare CS between groups. Wald chi square followed by pairwise comparisons was used to compare CS between multiple groups.ResultsWe included 12 patients with rod-cone dystrophy (RCD), 3 patients with Stargardt disease (STGD) and 2 patients with Best disease. Patients with IRD had significantly worse CS than controls (p < 0.001) in all spatial frequencies. Patients with STGD had more marked deficits in CS than patients with Best disease (p < 0.001) and RCD (p < 0.001) despite having similar visual acuities.ConclusionPatients with IRD, especially patients with STGD with relatively preserved visual acuity have marked deficits in CS when measured across a range of spatial frequencies. We recommend that clinical trials for STGD incorporate CS measured over a range of spatial frequencies as a secondary clinical endpoint for monitoring visual function. CS may provide an explanation for complaints of visual dysfunction when visual acuity is not significantly altered.

Evaluation of photoreceptor function in inherited retinal diseases using rod‐ and cone‐enhanced flicker stimuli

“…46,47 The larger cone FMTs relative to rods (Figure 2) measured in this study and cone/rod FMT ratios above unity in cone-dominated disease (Figure 3a) are consistent with previously reported studies, which also show greater cone losses relative to rods in patients with cone dystrophy. 17,19,23 Larger rod FMTs relative to cones (Figure 2) and below unity cone/rod FMT ratios in rod-dominated diseases (Figure 3) are also in line with reports from previous studies. 18,49 Smaller response amplitudes in rodspecific electroretinogram signals and accelerated loss in rod function when compared to cone responses have been reported in patients with the rod-dominated disease such as retinitis pigmentosa.…”

Monitoring progression of retinitis pigmentosa: current recommendations and recent advances

“…There is no pattern of contrast sensitivity function that is unique to any particular disorder, although it could be a useful tool in monitor progression in Stargardt disease. [27] 2.1.3 Visual Field-Visual acuity tends to be an insensitive measure of disease severity, and other tests of visual function are required to diagnose and monitor RP. In static perimetry (i.e., automated perimetry), a stationary target is changed in size and brightness until seen, while in kinetic perimetry (i.e., Goldmann visual field) a target of predefined size and luminance is moved from a non-seeing to a potentially seeing area.…”

Advancing Clinical Trials for Inherited Retinal Diseases: Recommendations from the Second Monaciano Symposium

“… 73 – 75 Patients with IRDs can experience deterioration of visual function and significant deficits in contrast sensitivity, even with relative preservation of visual acuity. 76 Strategies for evaluating rod function specifically, for example using two-color perimetry, are needed to develop sensitive measures that enable earlier detection of disease progression. Strategies for distinguishing rod from cone function, and quantitating cone function, are needed to assess outcomes in primary cone IRDs, including achromatopsia and blue-cone monochromacy.…”