Acute retinal pigment epitheliitis using adaptive optics imaging: a case report

Acute Retinal Pigment Epitheliitis (ARPE, Krill's disease) is a rare inflammatory retinal disorder commonly affecting young adults. It often presents unilaterally with central vision disruption, and typically resolves with vision restoration within 6 to 12 weeks. The pathogenesis of ARPE remains a subject of ongoing debate. Adaptive Optics Flood Illumination Ophthalmoscopy (AO-FIO) imaging has emerged as a valuable tool capable of detecting early cone photoreceptor changes and recovery. This case study presents two patients with ARPE, with longitudinal follow-up using multimodal imaging, including optical coherence tomography (OCT) and AO-FIO. A 30-year-old male presented with sudden vision loss in both eyes. The best corrected visual acuity (BCVA) was 20/33 and 20/40 Snellen in the right and left eye, respectively. OCT showed interruption of the ellipsoid zone (EZ) band and outer nuclear layer (ONL) in both eyes; AO-FIO imaging revealed a foveal lesion and diminished parafoveal cone density in both eyes compared to two age-matched controls. After 6 months, BCVA was restored to 20/20, and OCT showed recovery of the ONL and EZ. On AO-FIO, the foveal lesion was still present and the parafoveal cone density increased but remained reduced even up to 15 months after onset when compared to the controls. The second patient, a 30-year-old woman, presented with a unilateral drop in vision to 20/63 Snellen. OCT showed discontinuation of the EZ and hyperreflectivity within the ONL and retinal pigment epithelium in the affected eye. The unaffected eye showed no abnormalities. After 3 months, the BCVA improved to 20/16 Snellen and OCT showed recovery of the EZ. AO-FIO was conducted 9 months after onset and revealed reduced parafoveal cone density in the affected and non-affected eye compared to the controls while OCT still showed recovery of all retinal layers. ARPE is a self-limiting disease with recovery of BCVA and OCT retinal layers within 6 months. However, our 2 cases showed that parafoveal cone density recovered during follow-up but did not reach levels observed in controls. AO-FIO is an imaging modality that enhances sensitivity in measurements and can therefore be used as a complementary tool for follow-up.