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M. S. Borchert, P. Garcia-Filion, C. Fink, M. M. Austin, A. C. Fisher, D. L. McCulloch; Ganglion Cell Deficits in optic Nerve Hypoplasia (ONH) Are Associated With a Selective Deficit in the N95 Component of the Pattern Electroretinogram (PERG). Invest. Ophthalmol. Vis. Sci. 2010;51(13):3269.
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© ARVO (1962-2015); The Authors (2016-present)
Pattern electroretinograms (PERGs) are affected in acquired inner retinal and optic nerve disease. In congenital optic nerve hypoplasia (ONH), functional assessment with PERGs has been limited by low signal-to-noise ratios associated with small signals, nystagmus, noise artifacts and the limited attention of young patients. We present a clinical study measuring PERGs with sedation and blind source signal detection to evaluate function in ONH.
In a cohort of 35 young children (age 3.5 - 36 months) with ONH, PERGs and ocular fundus photographs were obtained with cycloplegia and chloral hydrate sedation. Disk diameter to disc to macula ratio (DD:DM) defined ONH severity. Raw data for 150 checkerboard reversals in each eye were recorded from DTL thread electrodes for five check sizes (4-0.25 degrees) with an optical system incorporating the cycloplegic refraction. Cardinal positions in PERG records were identified automatically as turning points in local 3rd-order polynomials fitted in the -3dB bandwidth [0.5 … 45]Hz using the webpage tool at http://clinengnhs.liv.ac.uk/esp_perg_1.htm. Confidence limits were estimated from bootstrap resampling. PERG detection and cursor positions for P50 and N95 were compared with the DD:DM and other clinical signs.
ONH was severe in 36 eyes (DD:DM 0.06-0.15), moderate in 26(DD:DM >0.15-0.30), mild in 4(DD:DM >0.30-0.35) and 4 eyes were classed as fellow eyes of unilateral cases. Significant PERG signals were measured in 74.8% of the recordings. The PERG P50 component was larger and earlier for larger checks (p<0.001) and smaller in those with tortuous retinal vessels (p=0.02), but did not correlate with ONH severity (p>0.4). The N95 amplitude (to P50), which increased with check size (p<0.0001) and age at test (p=0.0006), was markedly reduced in more severe ONH (p<0.0001) and in those eyes with clinically apparent disk pallor (p=0.003).
Automated blind source signal detection techniques can be applied to reliably and objectively detect PERG changes associated with ONH. These data demonstrate that congenital deficits of retinal ganglion cells are associated with PERG changes, specifically normal positive P50 components with a selective loss of the later negativity, the N95.
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