Visual loss following silicone oil removal

Southampton Eye Unit, UK

Keywords: visual loss; silicone oil

We congratulate Cazabon et al on their recent, well illustrated, report.1 Their cases reflect a similar group of seven patients we recently observed at Moorfields Eye Hospital.2 They were relatively young, 19–57 years old, had macula-on, or "just off" retinal detachments. Five of seven had giant retinal tears and the others multiple posterior tears with retinal detachment. Following vitrectomy and oil insertion, vision was good and then fell when the silicone oil was removed. The oil was in place for between 105–220 days; three patients had combined cataract surgery with oil removal.

One difference between the reports is that vision in our group fell immediately following oil removal, whereas in Liverpool patients reported visual loss at 1 week. Visual loss could be severe, some lost vision to counting fingers with a relative afferent papillary defect, and all lost vision without macular signs, optical coherence tomographic, or angiographic changes.

The interpretation of electrophysiological changes is different from that in our paper, where macular dysfunction was associated with generalised retinal dysfunction in some patients and with an optic neuropathy in one. In this paper only the macular function is commented on, the 30 Hz cone flicker being presented, and it is therefore difficult to compare data without the full ISCEV data.3,4 It is not clear how the pattern visually evoked potential (VEP) can be "normal" in case 1, with a visual acuity of 6/36 and an abnormal pattern electroretinogram (PERG); even in macular disease with this level of visual acuity and an abnormal PERG, the pattern VEP is invariably abnormal.3

A recent report of optic neuropathy induced by silicone oil may perhaps explain our findings in one case.5 However, all the other cases reported so far seem to point to a new as yet unexplained phenomenon of sudden visual loss following silicone oil removal. Photoreceptor apoptosis, triggered by rapid change in vitreous potassium concentrations, is an attractive theory, but more work is required to elucidate this phenomenon further. In the meantime we advocate a cautious approach to silicone oil in patients with macular-on detachments.

References

Cazabon S, Groenewald C, Pearce IA, et al. Visual loss following removal of intraocular silicone oil. Br J Ophthalmol 2005;89:799–802.

Newsom RS, Johnston R, Sullivan PM, et al. Sudden visual loss after removal of silicone oil. Retina 2004;24:871–7.

Fishman GA, Birch DG, Holder GE, et al. Electrophysiologic testing in disorders of the retina, optic nerve, and visual pathway. 2nd ed. Ophthalmology monograph 2. San Francisco: The Foundation of the American Academy of Ophthalmology, 2001.

Marmor MF, Hood DC, Keating D, et al. Guidelines for basic multifocal electroretinography (mfERG). Doc Ophthalmol 2003;106:105–15.

Eckle D, Kampik A, Hintschich C, et al. Visual field defect in association with chiasmal migration of intraocular silicone oil. Br J Ophthalmol 2005;89:918–20.