Rapid macular thinning predicts hydroxychloroquine retinal toxicity

In many patients receiving long-term hydroxychloroquine therapy, retinal thickness remains stable for years but may start to thin quickly after a critical point, according to a recent study.

Furthermore, evidence of this early structural change is made available by sequential plots of inner and outer Early Treatment Diabetic Retinopathy Study (ETDRS) ring macular thickness years before conventional signs appear.

“This approach can alert patients and prescribing physicians to potential retinal damage and uses readily available optical coherence tomography (OCT) measurements that could be automated by manufacturers for use in comprehensive eye care settings,” the authors said.

This retrospective case cohort study included 301 patients receiving long-term hydroxychloroquine therapy at Kaiser Permanente Northern California who underwent a minimum of four OCT studies that included ETDRS retinal thickness values over a minimum of 4 years.

The authors created sequential retinal thickness plots to present the rate of change in macular thickness within ETDRS regions.

In 219 stable patients treated with long-term hydroxychloroquine therapy, retina thinning was 0.62 μm/year on average. On the other hand, 82 patients demonstrated a period of relatively linear rapid thinning at 3.75 μm/year.

Among patients with rapid thinning, 38 eventually showed conventional OCT or 10-2 visual field signs of hydroxychloroquine retinal toxicity. Their cumulative retinal thinning was 25.1 μm compared with 15.7 μm in those without conventional toxicity (p<0.01).