Three vision tests are contained in this battery designed for assessment of Multiple Sclerosis patients:
High Contrast Visual Acuity
Low Contrast Visual Acuity (2.5% and 1.25%)
Letter Contrast Sensitivity
All tests validated. See:Sattarnezhad N, Farrow S, Kimbrough D, et al. Agreement analysis comparing iPad LCVA and Sloan testing in multiple sclerosis patients. Mult Scler 2018;24:1126-30.
Unlike printed tests, these charts require no external lighting and runs on the iPad without need for special software or calibration. The tests utilize the high quality iPad screen to produce letters small enough to measure visual acuity at test distances as short as 6 feet or 2 meters.
Disturbances in visual function are common in patients with multiple sclerosis (MS). These impairments are often not readily apparent on commonly used high-contrast acuity tests so low-contrast charts have been leveraged in the assessment of visual dysfunction in patients with MS. Low contrast visual acuity and contrast sensitivity best distinguished MS patients from disease-free control subjects in the Multiple Sclerosis Vision Prospective cohort. Decrements in low contrast visual acuity are associated with MS and correlate with increasing disability, MRI abnormalities, and reduced retinal nerve fiber layer (RNFL) thickness as measured by optical coherence tomography (OCT). Low-contrast letter acuity testing is a potentially useful addition to disability scales such as the Multiple Sclerosis Functional Composite. Two phase 3 studies of natalizumab showed that low-contrast letter acuity testing demonstrated treatment effects. The use of low-contrast letter acuity tests may improve assessment of treatment efficacy in patients with MS.
The letters are calibrated for the Retina Display.
The contrast of the visual acuity charts are defined by Michelson contrast. The Weber contrast values are 2X higher.