Sir,

Desferrioxamine (DFO) is a chelating agent for the treatment of iron overload with well recognised ocular and ototoxicity. This case report illustrates an optic neuropathy in DFO ocular toxicity undetected on slitlamp biomicroscopy examination but illustrated by optical coherence tomography (OCT).

A 74-year-old female myelofibrosis patient weighing 10.5 stones on 1.5 g of subcutaneous DFO presented with deteriorating vision associated with moderate neurosensory deafness. DFO toxicity was diagnosed and treatment ceased.

At presentation, visual acuity had reduced from 6/6 to 6/12 in the right and 6/9 in the left. Ishihara was reduced with 2/13 plates identified. Humphrey 24-2 visual field assessments showed bilateral peripheral losses. Slitlamp biomicroscopy was normal. A relative afferent papillary defect was absent.

OCT imaging of the macula and retinal nerve fibre layers (RNFLs; Figure 1) were obtained with a Stratus OCT machine (Carl Zeiss Meditec Inc., Dublin, CA, USA). Macula OCT scan had a normal foveal dip with no signs of fluid or retinal thickening. OCT RNFL scans were obtained with reference planes at 150 μm above the level of RPE revealing a thickened OCT RNFL.

Figure 1
figure 1

OCT RNFL of patient at presentation.

Full size image

Over 10 months, visual acuity (6/7.5 bilateral) and colour vision (13/13 bilateral) improved with a reduction in OCT RNFL thickness.

Peripapillary atrophy and fine pigmentary changes in both posterior poles were now visible.

Discussion

DFO ocular and ototoxicity in our patient was in keeping with descriptions from previous reports.1, 2, 3

In 1984, Lakhanpal et al2 reported retinal pigmentary degeneration and a presumed optic neuropathy with DFO. Interestingly, he presented patients with presumed retrobulbar optic neuropathy based on the central scotomas and colour vision abnormalities experienced.2 Our case report supports the suggestion that previously undetected optic neuropathy may be part of the DFO ocular toxicity spectrum.

Often DFO ocular toxicity is diagnosed by a clinical history and a reduction in visual function. Subtle early signs makes detecting and screening for DFO toxicity difficult. Monitoring disease progression is hindered by late pigmentary changes emerging after visual function recovery. Hence, non-invasive OCT imaging; a well-tolerated scan; may prove useful in early detection and monitoring recovery. To the best of our knowledge, this is the only case to illustrate DFO optic neuropathy on OCT.