Retinopathy Following the Use of Chloroquine and Allied Substances

Selective thinning of the perifoveal inner retina as an early sign of hydroxychloroquine retinal toxicity

PURPOSE

To evaluate macular thickness profiles using spectral-domain optical coherence tomography (SDOCT) and image segmentation in patients with chronic exposure to hydroxychloroquine.

METHODS

This study included eight patients with chronic exposure to hydroxychloroquine (group 1) and eight controls (group 2). Group 1 patients had no clinically evident retinal toxicity. All subjects underwent SDOCT imaging of the macula. An image segmentation technique was used to measure thickness of six retinal layers at 200 microm intervals. A mixed-effects model was used for multivariate analysis.

RESULTS

By measuring total retinal thickness either at the central macular (2800 microm in diameter), the perifoveal region 1200-microm-width ring surrounding the central macula), or the overall macular area (5200 microm in diameter), there were no significant differences in the thickness between groups 1 and 2. On an image segmentation analysis, selective thinning of the inner plexiform+ganglion cell layers (P=0.021) was observed only in the perifoveal area of the patients in group 1 compared with that of group 2 by using the mixed-effects model analysis.

CONCLUSION

Our study results suggest that chronic exposure to hydroxychloroquine is associated with thinning of the perifoveal inner retinal layers, especially in the ganglion cell and inner plexiform layers, even in the absence of functional or structural clinical changes involving the photoreceptor or retinal pigment epithelial cell layers. This may be a contributing factor as the reason most patients who have early detectable signs of drug toxicity present with paracentral or pericentral scotomas.

Chloroquine retinopathy and secondary trauma

This report describes a patient who initially presented with established chloroquine retinopathy resulting in reduced distance visual acuity, color vision anomalies and maculopathy in each eye. Subsequent trauma to the left side of the head produced a further decline in vision, accompanied by iritis and macula edema. A differential diagnosis, classification and treatment plan for patients with chloroquine retinopathy is presented.

Dose refinements in long-term therapy of rheumatoid arthritis with antimalarials

No eye disease was detected in over 900 rheumatoid arthritis patients treated with less than 4.0 mg/kg per day of chloroquine or less than 6.5 mg/kg per day of hydroxychloroquine for a mean of about seven years. I therefore consider these dosage rates safe, since they are below the threshold of retinal toxicity. This is based on more than 6,000 patient-years of drug exposure. That dosage threshold for retinopathy appears to be 5.1 mg/kg per day for chloroquine and 7.8 mg/kg per day for hydroxychloroquine according to my studies with these compounds. The daily dosage rate, rather than total drug accumulation, seems to determine the development of eye disease. To prevent overdosage, dosing should be calculated not on the actual weight of the patient but on ideal (lean) body weight. Furthermore, the patient's renal and liver function should also be taken into account to avoid overdosage. Since exposure to light amplifies the risk of retinopathy in patients treated with antimalarials, dark sunglasses are recommended for patients spending much time in sunlight.

Ophthalmologic safety of long-term hydroxychloroquine treatment

Ocular toxicity of long-term hydroxychloroquine treatment was assessed by regular ophthalmologic examinations in 99 patients. No patient developed significant loss of vision or visual field constriction to a white test object. Three patients had evidence of toxicity, but the medication had to be permanently discontinued in only one who subsequently had regression of all abnormalities except visual field constriction to a red test object. Neither duration of treatment nor the diagnosis of systemic lupus erythematosus predisposed patients to toxicity.