Abstract
Purpose: :
To evaluate recovery process of retinal function and ultrastructure especially in the thickness in the layer of inner and outer segments (IS/OS) of the photoreceptors in a patient with acute zonal occult outer retinopathy (AZOOR).
Methods: :
Five cases diagnosed as AZOOR, 1 male and 4 females, raging in age from 22 to 46 years old (mean age 30.2±5.3 years old), were evaluated in their natural course. All the cases were affected by one eye and diagnosed as AZOOR. The retinal function and microstructure were monitored in the course of recovery by means of multifocal electroretinogram (mfERG) and fourier domain optical coherence tomography (FD-OCT), respectively. Three phases (acute phase, early recovery phase, and late recovery phase) were studied.
Results: :
Visual acuity was decreased in all cases at the acute phase, and the mfERG showed reduced responses density in the central area. The FD-OCT showed that both IS/OS line and cone outer segment tip (COST) line in the macula were extinguished. The mean distance between bottom of the external limiting membrane and the surface of retinal pigment epithelium (thickness in the layer of IS/OS of the photoreceptors; IS/OS thickness) was 48.8±8.7um, and that of healthy fellow eyes was 74.0±6.3um (IS:31.6±5.4um, OS:42.4±2.8um). Spontaneously the visual acuity improved and mfERG demonstrated improvement of the retinal response in the central area. However, the FD-OCT revealed recovery of only the IS/OS line in the macula and the COST line was indiscernible, though the mean IS/OS thickness increased to 61.7±6.7um (IS:33.0±4.6um, OS:28.7±4.7um) at early recovery phase, and 73.3±5.7um (IS:32.7±7.1um, OS:40.7±1.4um) at late recovery phase, whereas those of fellow eyes were almost stable.
Conclusions: :
The reason for the discrepancy between the mfERG and microstructure of COST line after visual recovery was unknown, although the focal retinal response seemed to be associated with the recovery of the IS/OS thickness. IS thickness was proved to recover earlier than OS thickness. Further follow up for these cases and investigation on other cases will be helpful to determine the meaning of the IS/OS thickness and integrity of the COST line.
Keywords: macula/fovea • retina: distal (photoreceptors, horizontal cells, bipolar cells) • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)