Abstract
Purpose: :
To compare the relative sensitivity of fundus exam, automated 10-2 fields, spectral density ocular coherence tomography (SD-OCT), mfERG and fundus autofluorescence (FAF) among patients with hydroxychloroquine (HCQ) toxicity.
Methods: :
A consecutive series of 10 patients diagnosed with HCQ toxicity was studied, based on chronic drug usage and evidence of bull’s eye maculopathy. Severity ranged from early maculopathy to widespread retinal dysfunction. Examinations included fundus exam, Humphrey 10-2 fields, OCT (Zeiss Cirrus), mfERG (Veris), FAF (Heidelberg), and in some cases full field ERG (Diagnosys).
Results: :
The diagnosis was most reliably made from SD-OCT and mfERG, which in all cases showed evidence of bull’s eye damage to the photoreceptors. The relative sensitivity depended in part on the quality of the recordings and sophistication of the reader (e.g. to recognize subtle thinning or IS/OS line damage, or ring-ratio change in the mfERG). FAF usually correlated but was more dependent on photographic quality or extent of disease. Diagnosis was paradoxically difficult in very severe toxicity where damage extended to peripheral retina and macular signs were partly obscured. 10-2 fields showed early scotomas, but rarely covering the extent of mfERG or SD-OCT change. Fundus changes were late, and unreliable.
Conclusions: :
Objective tests such as SD-OCT, mfERG and to a lesser extent FAF seem the most accurate and sensitive procedures for early detection of HCQ toxicity. Fields may be done where objective tests are unavailable, but require care and critical reading. Even the objective tests require good images and skilled interpretation. Fundus change is a very poor screening sign. With careful screening HCQ, toxicity can be detected before serious visual loss.
Keywords: drug toxicity/drug effects • imaging/image analysis: clinical • electroretinography: clinical