# Contrast Sensitivity and Colour Vision Tests for Early Detection and Monitoring of Hydroxychloroquine Retinal Toxicity: A Preliminary Study

## TL;DR

This study explores how contrast sensitivity and color vision tests can detect early signs of retinal damage caused by hydroxychloroquine, a drug used in autoimmune diseases.

## Contribution

The study introduces contrast sensitivity and Konan ColourDX HD tests as potential early indicators of retinal toxicity in hydroxychloroquine users.

## Key findings

- Contrast threshold of L and M-cone photoreceptors was significantly reduced in patients compared to controls.
- Contrast sensitivity tests showed significant reduction at all spatial frequencies in patients.
- OCT measurements did not reveal significant differences in retinal thickness between patients and controls.

## Abstract

Background/Objectives: Hydroxychloroquine (HCQ) is used to manage various autoimmune diseases, including systemic lupus erythematosus. The prolonged use of HCQ is associated with retinopathy and irreversible visual loss due to retinal toxicity. Despite adherence to dosage regimens, patients may develop functional rather than structural changes, without detectable abnormalities on routine examination using visual acuity and optical coherence tomography (OCT). The study aimed to detect early signs of retinopathy in patients with autoimmune diseases treated with HCQ. Methods: This cross-sectional study included patients (n = 36) with autoimmune diseases who were treated with HCQ. The control group (n = 35) comprised healthy volunteers matched for age and sex. All participants were screened using colour vision tests (Ishihara, Konan ColourDX high definition [HD]), and retinal thickness was evaluated using OCT. Results: Our findings suggest a significant reduction in the contrast threshold of the L and M-cone photoreceptors compared with that of the control using Konan ColourDX HD. The OCT measurements revealed no statistically significant difference in retinal thickness between patients and controls; however, the contrast sensitivity test showed a significant reduction at all spatial frequencies (p < 0.0001). Conclusions: The current study suggests that the Konan ColourDX cone contrast test HD and contrast sensitivity testing may be valuable for periodic monitoring of patients receiving HCQ, potentially enabling earlier detection of toxicity. However, longitudinal studies with larger cohorts are needed to confirm these findings and to further establish the clinical value of these functional visual tests.