Contrast Sensitivity Loss in Glaucoma Using the Reaction Time Paradigm

Glaucoma is a progressive optic neuropathy characterized by retinal ganglion cell loss, often leading to visual impairment before measurable deficits in visual acuity occur. Contrast sensitivity (CS) provides critical insight into visual function, particularly under low-contrast conditions. This study investigates the pattern of contrast sensitivity loss in glaucoma using a reaction time (RT) paradigm, which reflects the interval between stimulus presentation and response initiation. Forty subjects (20 glaucoma patients, 20 healthy controls) aged 16 to 40 were tested using the Contrast Sensitivity Test Suite software with three stimuli (number, blinking square, jumping square). Reaction time increased as contrast decreased, with glaucoma patients showing significantly longer RTs across all stimuli compared to controls (p < 0.01). Regression analyses indicated that dysfunction in slow sustained (magnocellular) channels primarily accounts for low-contrast sensitivity deficits in glaucoma. These findings support the use of contrast sensitivity and reaction time measurements as sensitive functional markers for early glaucomatous changes, even in individuals with normal visual acuity.