Impaired contrast sensitivity among leprosy patients with normal visual acuity

Contrast sensitivity is a person's ability to identify an object from its background. Patients with normal visual acuity can have reduced contrast sensitivity and may experience trouble in identifying objects at night or moving around in dimly lit places. Contrast sensitivity has never been studied in leprosy patients having normal visual acuity. This study aimed to determine if contrast sensitivity is impaired in leprosy patients who have normal visual acuity and to identify possible associations with demographic, leprosy and ocular characteristics. A hospital based study measuring and comparing contrast sensitivity using the VCT 6500 chart in 127 consecutive leprosy patients without clinically apparent ocular complications and 123 non-leprosy controls was done. Contrast sensitivity was impaired in leprosy patients in all five spatial frequencies (1.5, 3.0, 6.0, 12 and 18 cycles/degree) investigated. Among leprosy patients, contrast sensitivity falling outside the normative range was associated with increasing age (adjusted OR 1.28, 95% CI: 1.14-1.42), being female (adjusted OR 11.05, 95% CI: 2.93-41.69) and having a grade 2 deformity (adjusted OR 6.43, 95% CI:1.68-24.61). Contrast sensitivity is impaired in leprosy patients having normal visual acuity. Elderly, deformed, female patients are particularly burdened with this vision loss.