Changes in the thickness of the inner retina at the macula after optic neuritis

In optic neuritis, retinal ganglion cells are lost as a result of axonal degeneration, but it is difficult to quantify this loss with magnetic resonance imaging. To quantitatively determine the number of retinal ganglion cells at the macula in eyes with optic neuritis, the thickness of the inner retina at the macula was examined in 10 eyes of 9 patients diagnosed with optic neuritis before and after corticosteroid pulse treatment and 10 eyes of 8 randomly chosen normal control subjects. The average visual acuity before treatment was 0.05, and all patients recovered to more than 1.0 visual acuity after the treatment. The mean thickness of the inner retina was measured using optical coherence tomography in the macular area at diameters of 3mm and 6mm; the regions measured were divided into nasal, temporal, superior, and inferior quadrants. The mean thickness of the inner retina in each quadrant after successful treatment was significantly less than those of the same patients before treatment, of their healthy contralateral eyes with optic neuritis. Especially, the nasal quadrant at 6mm and the temporal and inferior quadrants at 3mm showed large decreases. Even though the visual acuity and the visual field recovered after corticosteroid pulse treatment, the mean thickness of the inner retina was decreased by 8 to 18μm in all quadrants of the macula, thus quantitatively supporting the hypothesis that retinal ganglion cells at the macula are lost with optic neuritis. OCT is useful in evaluating the loss of retinal ganglion cells in optic neuritis.