# Case Report: Progressive visual decline after optic neuritis associated with microcystic macular oedema

## TL;DR

A man with multiple sclerosis experienced worsening vision over five years despite stable MRI results, linked to a rare condition called microcystic macular oedema.

## Contribution

This case report documents the progression of microcystic macular oedema and its association with visual decline in a patient with MS.

## Key findings

- Microcystic macular oedema was detected and progressively worsened over five years.
- Visual acuity declined progressively despite no MS relapses or MRI activity.
- Longitudinal OCT monitoring revealed retinal neuroaxonal thinning alongside MMO progression.

## Abstract

A 39-year-old man was diagnosed with multiple sclerosis (MS) following unilateral optic neuritis (ON). His vision improved with corticosteroid treatment, but residual deficits remained (visual acuity at initial discharge: 0.7). Ocrelizumab was started, without any confirmed relapses or activity on magnetic resonance imaging (MRI) ever since. Nevertheless, his vision gradually deteriorated (0.3). Optical coherence tomography (OCT) detected microcystic macular oedema (MMO) at month 6, which showed clear progression over 5 years. MMO is rare, and longitudinal data on its evolution are scarce. In our case, a progressive MMO course was accompanied by retinal neuroaxonal thinning and gradual visual decline, despite clinical and MRI stability under ocrelizumab. This case highlights that late or progressive visual deterioration after severe ON may be associated with evolving MMO, which can be monitored by longitudinal OCT.