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  1. Visual loss may be due to silicone oil tamponade effect rather than silicone oil removal

    Dear Editor,

    We read with great interest the article by S Cazabon et al. "Visual loss following removal of intraocular silicone oil".[1]

    In all the three patients it would have been better to compare the visual acuity just before the silicone oil removal than immediate visual acuity after initial vitrectomy. Because the silicone oil contact with eye also could be responsible for visual loss as it was known to cause optic nerve damage as described in earlier reports.[2]

    Earlier Newsom RS et al also[3] reported unexplained sudden visual loss following silicone oil removal in seven patients. They also observed only electrophysiological abnormalities.

    May be the unexplained visual loss could be due to optic nerve damage and diffuse gangilion cell dysfuntion due to silicone oil tamponade effect on eye rather than procedure of silicone oil removal itself.

    References

    1. S Cazabon, C Groenewald, I A Pearce, and D Wong. Visual loss following removal of intraocular silicone oil.Br J Ophthalmol 2005; 89: 799-802

    2. Budde M, Cursiefen C, Holbach LM, Naumann GO. Silicone oil-associated optic nerve degeneration. Am J Ophthalmol. 2001 Mar;131(3):392-4.

    3. Newsom RS, Johnston R, Sullivan PM, Aylward GB, Holder GE, Gregor ZJ. Sudden visual loss after removal of silicone oil.Retina. 2004 Dec;24(6):871-7.

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  2. Visual loss after silicone oil

    Dear Editor,

    We read with interest the paper by Cazabon et al.[1] on the important emerging problem of sudden visual loss after removal of silicone oil. We have seen a similar pattern of visual loss in our own patients typically seen in macula on detachments associated with giant retinal tears. We have identified 12 cases between 2 units (St Thomas’, London and Sunderland Eye Infirmary), but 5 of these clearly describe onset of visual loss before oil removal (onset between 1 month and 5 months after oil insertion).[2] Results of investigations were very similar to those reported by Cazabon et al. In 4 of 5 pattern ERG was suggestive of macular dysfunction. The timing of onset of visual loss obviously alters the potential aetiology, which as stated is unknown.

    In their paper, information on acuity for cases 2 and 3, between 1 week after oil insertion and oil removal is not provided. Did these cases have visual loss preceding oil removal? Developing cataract can obviously hinder interpretation of acuity measurements. In our cases the symptoms described did not fit with cataract (scotoma, red desaturation) and persisted if any cataract was removed.

    We have seen a further case since this report, a 46 year old female with a giant retinal tear and macula-on retinal detachment affecting the right eye. Acuity reduced during period of tamponade from 6/6 2 weeks after oil insertion to 6/36+1, which did not recover after oil removal. She reported a central negative scotoma. Electrophysiology suggested macular dysfunction.

    We have speculated that photo-toxicity may play a role, as oil transmits light more in the blue spectrum than aqueous.[3] The fat soluble macula pigments, lutein and zeaxanthin, are thought to protect the macula from photo-oxidative damage. Silicone oil has previously been reported to dissolve fat soluble elements from the retina.[4]

    We measured the macular pigment optical density (MPOD) in this case using a modified confocal scanning laser ophthalmoscope and 2-wavelength autofluorescence technique 3 weeks after oil removal. The results showed a substantially reduced MPOD in the eye which had silicone oil compared to the fellow eye. Although the peak MPOD, at the foveal centre, of both eyes was similar (0.47 Right vs. 0.52 Left), the MPOD at half-degree, one-degree and 2-degrees eccentricity from the foveal centre was markedly lower in the eye which had silicone oil (0.12, 0.06, 0.02 respectively vs. 0.40, 0.22, 0.07).

    Although MPOD varies greatly between individuals, there is usually high inter-ocular symmetry in normal eyes.[5] Further work is required to determine whether or not this relates to the visual loss and whether therapeutic supplementation, may reduce the risk of visual loss.

    References

    1. Cazabon S, Groenewald C, Pearce IA, Wong D. Visual loss following removal of intraocular silicone oil. Br J Ophthalmol 2005;89:799-802.

    2. Herbert EN, Habib M, Steel D, Williamson TH. Central scotoma associated with intraocular silicone oil tamponade develops before oil removal. Graefe’s Arch Clin Exp Ophthalmol. DOI 10.1007/s00417-005-0076-6.

    3. Azzolini C, Docchio F, Brancato R Trabucchi G. Interactions between light and vitreous fluid substitutes. Arch Ophthalmol. 1992;110:1468-1471.

    4. Refojo MF, Leong FL, Chung H et al. Extraction of retinol and cholesterol by intraocular silicone oils. Ophthalmology 1998;95:614-8.

    5. Bone RA, Sparrock JM.. Comparison of macular pigment densities in human eyes. Vision Res. 1971;11:1057-1064.

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  3. Visual loss following silicone oil removal

    Dear Editor,

    We congratulate the Cazabon et al. on their recent, well illustrated, report of 'Visual loss following removal of silicone oil.'[1] Their cases reflect a similar group of seven patients we recently observed at Moorfields Eye Hospital.[2] They were relatively young 19-57yrs, had macula- on, or 'just off' retinal detachments, 5/7 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 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 one week. Visual loss could be severe, some lost vision to counting fingers with a relative afferent papillary defect, and all lost vision with without macular signs, optical coherence tomographic or angiographic changes.

    The interpretation of electrophysiological changes are different to 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 30Hz 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 VEP can be "normal" in case 1, with a visual acuity of 6/36 and an abnormal PERG; even in macular disease with this level of VA 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 mean time we advocate a cautious approach to silicone oil, in patients with macular on detachments.

    Richard Newsom, Rob Johnston, Paul Sullivan, Bill Aylward, Graham Holder, Zdenek Gregor.

    References:

    1. Visual loss following removal of intraocular silicone oil, S Cazabon, C Groenewald, I A Pearce, D Wong Br J Ophthalmol 2005;89:799–802.

    2. Newsom RS, Johnston R, Sullivan PM, Aylward GB, Holder GE, Gregor ZJ. Sudden visual loss after removal of silicone oil. Retina. 2004 Dec;24(6):871-7.

    3. Fishman GA, Birch DG, Holder GE, Brigell MG: Electrophysiologic Testing in Disorders of the Retina, Optic Nerve, and Visual Pathway, Second Edition. Ophthalmology Monograph 2. San Francisco: The Foundation of the American Academy of Ophthalmology; 2001.

    4. Marmor MF, Hood DC, Keating D, Kondo M, Seeliger MW & Miyake Y. Guidelines for basic multifocal electroretinography (mfERG). Doc Ophthalmol 2003;106:105–115.

    5. D Eckle, A Kampik, C Hintschich, C Haritoglou, J-C Tonn, E Uhl and A Lienemann.Visual field defect in association with chiasmal migration of intraocular silicone oil British Journal of Ophthalmology 2005;89:918-920

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