Measurement of retinal nerve fiber layer and macular ganglion cell-inner plexiform layer with spectral-domain optical coherence tomography in patients with optic nerve head drusen.

Purpose: To evaluate the effect of optic nerve head drusen (ONHD) on the retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) using Cirrus optical coherence tomography (OCT).
Methods: Fifty-seven eyes of thirty patients with ONHD and thirty-eight eyes of twenty age-matched and sex-matched control subjects underwent circumpapillary and macular scanning using Cirrus OCT. The percentages of eyes with abnormal GCIPL and RNFL values according to the Cirrus normative data were analysed and compared.
Results: Overall, eyes with ONHD showed abnormally reduced values for average and minimum GCIPL thicknesses in 35 % and 45 % of cases compared to 2 % for both values in control eyes (P < 0.001). Average RNFL thickness comparison between eyes with ONHD and normal eyes revealed abnormal thinning in 33 % vs. 0 %, respectively (p = 0.002). The percentage of abnormal thinning increased with higher grades of ONHD for all the parameters evaluated, so that in grade III drusen, values were abnormally reduced in 80 % of eyes in all three analyses. Regarding buried ONHD, 30 % and 4 % of eyes had an abnormally reduced minimum GCIPL and average RNFL thickness, respectively. Furthermore, 26 % of these eyes had abnormal GCIPL exams with a normal or increased RNFL thickness.
Conclusions: Both RNFL and GCIPL analysis reveal significant thinning in eyes with ONHD directly correlated with drusen severity. In buried ONHD, the abnormality rate was significantly higher with GCIPL compared to RNFL evaluation, suggesting that GCIPL analysis might be an early structural indicator of neuronal loss in the setting of thickened RNFL.