A 54-year-old man presented with blurred central vision in the right eye of two weeks' duration. On presentation, visual acuity was 40 / 50 in the right eye and 20 / 20 in the left eye. Anterior and posterior segment examination of the left eye was unremarkable. On exam, the right eye exhibited mild inflammation in the anterior chamber and the vitreous. Fundus examination showed a whitish-yellow inflammatory lesion near an atrophic, pigmented retinochoroidal scar located in the superotemporal quadrant (Fig. 1A). Hyperfluorescence on early-phase FAG was observed at the margin of the old pigmented lesion and in the new lesion (Fig. 2A). The new lesion also showed hyperfluorescence in the late phase (Fig. 2B). SD-OCT showed increased reflectivity from the inner retinal layer, retinal thickening, and choroidal shadowing. Focal posterior hyaloid thickening and detachment were observed in the new lesion (Fig. 1B). In the old lesion, SD-OCT showed hyperreflectivity, thinning of the neurosensory retina and a disorganized retinal pigment epithelium (RPE) layer (Fig. 2C). Serum IgM was negative but an elevated serum level of IgG (75 IU/mL; reference value, <4 IU/mL) to toxoplasma was observed. A syphilis evaluation and other tests which were toxocariasis and rheumatologic tests were negative. A presumptive diagnosis of toxoplasmic retinochoroiditis was made and a regimen of trimethoprim/sulfamethoxazole 960 mg po bid and clindamycin 150 mg po qid was started. Prednisone (30 mg/day) was added and tapered over a period of four weeks. Six weeks later, the lesion had resolved (Fig. 3A) and the patient's right-eye visual acuity had improved to 20 / 20. SD-OCT performed after treatment showed thinning of the retina, a disorganized RPE layer and posterior hyaloid detachment (Fig. 3B).

The diagnosis of ocular toxoplasmosis is most often based on the presence of characteristic clinical findings, which include focal retinochoroiditis, an adjacent or nearby retinochoroidal scar, and moderate to severe vitreous inflammation [3]. OCT is a noninvasive imaging modality that provides high-resolution, cross-sectional images of the retina. The recent introduction of SD-OCT has enabled imaging with greater resolution, higher scan speed, wider sampling area, and improved image registration [4]. Typical OCT findings of ocular toxoplasmosis include increased intraretinal reflectivity corresponding to the area of retinitis with shadowing of the underlying choroidal tissue. Posterior hyaloid thickening and detachment over the lesion and contained irregular hyperreflective formation are also typical [5].

Here we reported a case of ocular toxoplasmosis with abnormal thinning of the neurosensory retina, disrupted RPE and posterior hyaloid detachment in the lesion on SD-OCT. The posterior hyaloid was markedly thickened and exhibited irregular hyperreflectivity. SD-OCT also showed the loss of normal intraretinal striations in the areas of retinitis and the epiretinal membrane in detail. These features were detected SD-OCT than time domain OCT. Moreover, SD-OCT allowed ireal-time imaging of these manifestations in three dimensions (3D). Specifically, 3D imaging allows for unique perspectives of the retina, including qualitative assessments, such as membrane traction, to be performed and incorporated into clinical decision-making. The use of SD-OCT is helpful for definitively differentiating ocular toxoplasmosis from other retinal diseases and may provide insight for understanding the pathophysiologic mechanisms of ocular toxoplasmosis. Furthermore, SD-OCT allows for the detection of detailed pathologic changes that occur during treatment and precludes the need to perform biopsies.