Case example of huge outer retinal cystoid space (CS) as seen on optical coherence tomography (OCT) in a patient with ocular toxoplasmosis.
Two days after initial presentation [A–N] and at subsequent follow-ups [P–Q] (note: [d–f] is the magnified view of [D–F]). The OCT scans were taken within a 20°×15° (5.8×4.4 mm) area. Distance between adjacent B-scans (B-scans B, C, D, E, G are adjacent; H, I, J are adjacent) was 243 µm. Two days after initial presentation, a membranous structure is seen on OCT. One part of this structure is seen lying over the retinal pigment epithelium (RPE) and forming the floor of the huge outer retinal CS (HORC) [B–E, G], while another part is separated from the RPE by an accumulation of subretinal fluid (SRF) [H–J]. The line representing the external limiting membrane (ELM) is distinct in the area unaffected by HORC; however, it is continuous with the upper border of the highly reflective membranous structure in the area affected by HORC [D–F, d–f]. The photoreceptor inner segment/outer segment junction (IS/OS junction) is distinct in the area unaffected by HORC, becoming less distinct in the area with overlying HORC. Photoreceptor IS/OS disruption and outer segment (OS) irregularity is also observed [E, G–J, e–f]. The retinal thickness map [L], mean HORC height map [M], and the mean maximum SRF height map [N], are shown for the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. The presumed interpretation of the structural changes are also shown (the outer retina is the area between the black arrows) [K]. OCT images obtained 15 days later demonstrate that the HORC is no longer present [O]. Punctate hyperreflective foci are seen in the posterior vitreous overlying this area. The ELM is almost completely distinct in all B-scans. In contrast, the photoreceptor IS/OS junction is still not fully distinct. Irregularity of the PR and outer nuclear layer (ONL) presenting as local hyperreflective foci is seen at the previous junction of the HORCs with the normal retina. This feature persists at subsequent visits [P–Q]. A hyporeflective space between the ELM or presumed IS/OS and inner boundary of the RPE is observed subfoveally, with possible hyperreflective material above RPE. Subsequent OCT images were obtained approximately one month [P] and two months [Q] following initial presentation. No HORC or SRF is seen at these points. The photoreceptor IS/OS junction is more clearly seen, with a thickness value of 68 µm [Q].