Response to Fajgenbaum

Sir,

We thank Dr Fajgenbaum¹ for his interest in our recent case series of maculopathy in poppers users² and for debate on this matter with respect to photic maculopathy.

The similarity of clinical signs in ‘poppers maculopathy' patients with those described in some patients with photic maculopathy is intriguing and as was also demonstrated in Dr Fajgenbaum's case report. We doubt the suggestion that poppers inhalation could lead to hallucinations or drastically altered consciousness, resulting in entrancement with bright lights or the sun. The psychogenic effects of poppers are well documented, but do not, in our opinion, lead to this sort of behaviour. It is also recognised that poppers use can be linked to abuse of other compounds, which may have more potent hallucinogenic effects. We also agree that as poppers are sometimes used in raves where exposure to unsafe use of laser lights is a potential risk, these matters need to be considered in the differential diagnosis of individuals with acquired foveal defects. To answer the question about substance abuse and exposure to light in our cases, a detailed drug and social history was taken. Cases were questioned about prolonged solar or other lights gazing and which was denied in all cases.

As we stated there were several features of our cases that support on the balance of probabilities evidence of causality of poppers maculopathy as based on the Bradford-Hill criteria. Mainster et al³ has provided helpful advice on assessment of alleged retinal laser injury patients and which can also in our opinion be extrapolated to alleged photic retinal injury. Furthermore, it is now increasingly recognised that the signs of alleged solar maculopathy on SD-OCT imaging are varied. As discussed in our paper, it is not possible to prove causality of poppers maculopathy and we agree that differential diagnosis of outer lamellar defects can be challenging⁴ and that a detailed history should be taken.

The authors declare no conflict of interest.