Reply

I thank Lyons for his comments and for alluding to Marmor's editorial, providing an opportunity to respond to both. His first concern is that the use of hydroxychloroquine not be halted without good cause. One can understand this concern based on the statistics from his practice, in which 89 (14.8%) of 600 screened patients had retinal toxicity confirmed by the combination of visual fields and multifocal electroretinography. If all these patients were asked to stop hydroxychloroquine, the rate would be 13-fold that in our sample (2 of 183 cases screened, or 1.1%) and 10-fold that of Elder and Rahman (4 of 262 cases screened, or 1.5%). One wonders if we define hydroxychloroquine toxicity the same way. Moreover, an ophthalmologist's potential response to concern about toxicity is more varied than simply recommending cessation of hydroxychloroquine, as Lyons' comment might be taken to imply. Table 2 in my paper showed that ophthalmologists recommended dosage reductions approximately 6 times as often as they recommended cessation of drug when toxic dosing without manifest toxicity was discovered.