Photoreceptor inner and outer segment layer thickness in multiple evanescent white dot syndrome

To evaluate the photoreceptor inner and outer segment layer thickness in eyes with MEWDS.

Prospective, non-comparative, observational case series. The follow-up duration was 4 months.

Four women were diagnosed with unilateral MEWDS. The ages of the patients were 25, 24, 35, and 40 years. The retinal microstructure was assessed by spectral-domain optical coherence tomography (SD-OCT). The thickness of the photoreceptor inner (IS) and outer (OS) segments and sum of them (IS + OS) at the fovea were analyzed.

The visual acuity was reduced in three of four eyes at the acute phase. SD-OCT showed that the border of IS and OS (IS/OS) line and the cone outer segment tips (COST) line in the macula area were not detected in all four eyes. The IS + OS thickness was 50.3 ± 5.6 μm and that of the healthy fellow eyes was 73.5 ± 7.0 μm (n = 4 eyes). The thickness of the IS was 27.8 ± 2.6 μm and that of the OS was 45.8 ± 7.3 μm. In all eyes, there was a spontaneous improvement of the visual acuity. SD-OCT showed a recovery of only the IS/OS line in the macular area, but the COST line was not visible in three cases. The mean IS + OS thickness increased to 56.0 ± 7.9 μm (n = 4), IS = 26.0 ± 2.0 μm (n = 3), and OS = 30.1 ± 8.7 μm (n = 3) in the early recovery phase, and to 64.8 ± 9.3 μm (n = 4), IS = 28.5 ± 1.7 μm (n = 4), and OS = 36.3 ± 7.9 μm (n = 4) in the late recovery phase. The mean inner and outer segment thickness remained unchanged in the fellow eyes.

Eyes with MEWDS have changes in the photoreceptor microstructures. The change in the IS + OS thickness during the natural recovery course might be due to an increase in the OS length.