Contrast sensitivity assessment for early detection of hydroxychloroquine toxicity

Hydroxychloroquine (HCQ), is known to cause visual dysfunction during its prolonged course of administration. Optical Coherence Tomography (OCT) and field tests are the commonly used screening tests. Not much is known about the role of contrast sensitivity (CS) as method for early detection of HCQ toxicity. This pilot study was designed to study the change in central and peripheral contrast sensitivity for detecting early signs of HCQ toxicity.

Prospective study conducted at Government Medical College & Hospital, Chandigarh, India.

Twenty eyes of 10 treatment naïve, autoimmune patients.

All patients underwent functional tests, contrast sensitivity tests: Pelli Robson and Spaeth Richman Contrast Sensitivity (SPARCS). Average and quadrant wise SPARCS score; Pelli Robson score and structural parameters viz., macular OCT parameters were compared at baseline, 3- and 6-month post treatment with HCQ.

Change in CS using SPARCS and Pelli Robson were recorded at each visit and compared with the baseline. Structural and functional parameters were correlated.

The average SPARCS scores at baseline, 3-month post HCQ and at 6-month post HCQ were 82.37 ± 8.40, 73.17 ± 9.63 and 70.37 ± 10.08, respectively. Quadrant wise change from first visit to third visit was statistically significant only in superotemporal (p = 0.002), inferotemporal (p = 0.02) and central (p = 0.01) quadrants. There was no correlation between SPARCS and Pelli Robson (S = 0.1454, p = 0.466). Similarly, there was no significant correlation between the structural and functional parameters.

HCQ affect the CS by virtue of its action on bipolar and ganglion cells. Decrease in central and peripheral CS as measured by SPARCS can be a sign of early visual dysfunction, hence must be considered as an early indicator of HCQ toxicity.