Validation of a novel multi-luminance shape discrimination test for assessment of functional vision

In low-vision patients, traditional measures often fall short of capturing functional vision improvements. The study aims to assess the reliability and validity of a novel functional low-vision outcome assessment, the Multi-luminance Shape Discrimination Test (MLSDT).

This is a prospective, observational study in 25 participants with severe vision loss due to retinitis pigmentosa (RP) with visual acuity worse than or equal to LogMAR 1.6, and in 10 normal vision participants. The MLSDT utilizes three differently shaped objects, randomly positioned on pressure sensors, to enable an automated, quantifiable response in a controlled multi-luminance environment. The assessment accuracy (recognizing the correct object and picking it up) was measured using the MLSDT. Convergent validity of MLSDT was evaluated with measures of visual acuity and visual field, as well as patient-reported outcomes.

The 35 study participants (60% male and 40% female) had a mean age of 46.5 years old (range: 19-78 years), with 24 Hispanic individuals. Estimates of test-retest reliability for MLSDT exceeded 0.50. The correlations between MLSDT test scores and LogMAR visual acuity were strong (> -0.7). For a difference of 0.3 LogMAR between the groups of RP participants, a decrease of ~ 2-level MLSDT score was observed. Moderate to strong correlations were also observed between MLSDT test scores and the measures of visual field and patient-reported outcome measures.

Psychometric evaluation demonstrates the reliability and validity of the novel functional vision endpoint, MLSDT. The MLSDT test performance in participants with different visual acuities showed improved object recognition when the luminance level was enhanced.