Outer retinal microstructure in a case of acute idiopathic blind spot enlargement syndrome

Abstract

Purpose: To present a patient with acute idiopathic blind spot enlargement syndrome who had abnormal changes in the outer retinal microstructure limited to areas with reduced responses on multifocal electroretinograms as well as to the area involving a scotoma.

Methods and results: We report the case of a 44-year-old man who developed an arcuate scotoma which was associated with a physiological blind spot in the left eye. The ophthalmoscopic, fluorescein angiographic, and full-field electroretinogram findings were normal. The amplitudes of the multifocal electroretinograms were reduced in the area of the scotoma. Optical coherence tomography showed that both the external limiting membrane and the inner and outer segment (IS/OS) line were intact, but that the middle cone outer segment tip line between the IS/OS line and the retinal pigment epithelium was absent in the nasal macular area of the left eye.

Conclusions: These findings indicate that the integrity of not only the external limiting membrane and IS/OS line but also the cone outer segment tip line is important for the function of the retina.

Keywords: Acute idiopathic blind spot enlargement syndrome; Cone outer segment tips; External limiting membrane; Inner and outer segment line; Optical coherence tomography.

Fig. 1

Fundus photographs, fluorescein angiogram, and full-field and multifocal ERGs from the left eye of the patient with AIBSE syndrome. Top: fundus photographs and fluorescein angiogram showing no abnormal findings. Second row: Goldmann visual field of the affected eye demonstrates an arcuate scotoma connected to the physiological blind spot. Third row: full-field ERGs revealing normal mixed rod-cone ERG and photopic cone ERG results in both eyes. Bottom: mfERGs showing a reduced response density in the area of the scotoma in the left eye. The response density in the central area is reduced in both eyes.

Fig. 2

SD-OCT images in our AIBSE patient. Upper left: image from a 9-mm horizontal scan of the right eye shows both an intact photoreceptor IS/OS line and an intact ELM. Upper right: image from a 9-mm horizontal scan of the left eye demonstrates an intact photoreceptor IS/OS line, an intact ELM and the absence of the COST line between the IS/OS line and the RPE in the nasal area of the macula (between arrowheads). Note that the COST line is intact on the temporal site with an intact visual field. Bottom: volume scans of the SD-OCT showing that the mean retinal thickness of the 9 areas of the Early Treatment Diabetic Retinopathy Study (ETDRS) decreased. The retinal thickness in the left eye is thinner than that of the right eye in the volume scan analyses.