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Christiana Dinah, David Steel, Haifa Madi; Multifocal electroretinogram (MFERG) in eyes demonstrating dissociated optic nerve fibre layer (DOFNL) appearance after internal limiting membrane (ILM) peeling. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2204.
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A potential adverse consequence of ILM peeling is the appearance of DONFL. Here, we describe the changes in local retinal electrical responses in eyes with DONFL appearance after ILM peeling.
Retrospective review of medical records, photography and MFERG data of 11 consecutive patients who underwent macular hole repair with ILM peeling using Brilliant Blue dye. The amplitude (nv/deg2) and implicit times (ms) of the peak MFERG response (P1 wave) were obtained from both operated eyes and fellow, unaffected eyes and grouped into five rings (Ring 1: Central 2° centred on the fovea, Ring 2: 2-5°, Ring 3: 5-10°, Ring 4: 10-15°, Ring 5: >15°). DONFL was identified on blue reflectance photographs post-operatively and OCT images used to identify the total number of focal depressions, characteristic of DONFL, which were scored. Area of peel was measured from intra-operative video images and minimum linear diameter of the macular hole was measured from pre-operative OCT images.
A higher DONFL score strongly correlated with larger area of peel, r=0.7. The P1 amplitude was reduced by 14.6% in zone 1 (p=0.03) and 7.7% in zone 2 (p=0.02) in eyes that underwent ILM peeling compared to unaffected fellow eyes. However, the implicit time was only significantly different in zone 5, with a 1.4% elongation compared to fellow eyes (p=0.03). In operated eyes, larger area of peel was associated with lower P1 amplitude in zone 1 (r2= 0.83, p=0.01) and zone 3 (r2=0.67, p=0.03) and associated with elongation of implicit time in zone 4 (r2=0.88, p=0.02) and 5 (r2= 0.75, p=0.03). A negative correlation between DONFL score and implicit time in zone 4 (r2= 0.88, p=0.02) and 5 (r2=0.75, p=0.01) was observed. No statistically significant correlations were observed between any factors assessed and implicit time in zone 1-3 or amplitude in zone 4 and 5.
Eyes with larger peel areas demonstrate lower P1 amplitude centrally and elongation of implicit time peripherally. DONFL is thought to be due to focal thinning of the ganglion cell layer. However, the MFERG waveform largely consists of responses from the outer retina. Our findings suggest that ILM peeling may cause changes deeper in the retina and larger peel areas may be associated with more retinal dysfunction. Prospective, longitudinal studies are required to confirm these findings.
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