Abstract
Purpose::
Outer retinal layers have been imaged extensively using various adaptive optics (AO) imaging systems. Less attention has been paid to imaging inner retinal layers largely because better axial resolution and higher sensitivity are required to visualize these layers. Adaptive optics - optical coherence tomography (AO-OCT) was used to image and quantify the changes of inner retinal layers that are observed in patients with retinal and optic nerve diseases.
Methods::
Forty patients with various retinal and optic nerve diseases were tested. The focus plane of the AO-OCT was set on the inner retinal layers so that lateral resolution and system sensitivity was maximized at that plane. Custom software was used to reconstruct and visualize 3- dimensional retinal volumes of AO-OCT images as well as to create thickness map of inner retinal layers. Intensity profiles of AO-OCT images were also created to detect subtle changes in the inner retinal layers. Retinal function tests that include mfERG, visual field analysis, contrast sensitivity and color vision test were also measured on each patient to correlate the changes in retinal function with the changes in retinal structure.
Results::
AO-OCT images revealed discrete structures in the ganglion cell layer corresponding to the size of ganglion cells in histological sections. Patients with optic nerve disease showed most changes in the nerve fiber and ganglion cell layers whereas patients with retinal disease showed no significant changes in the inner retinal layers compared to age-matched normal subjects. There were also changes in the intensity profile of the inner retinal layers in optic nerve disease that were not observed in retinal disease.
Conclusions::
It is possible to detect and quantify microscopic changes in the inner retinal layers from AO-OCT images. The retinas with optic nerve disease showed marked changes in the inner retinal layers which correlated with the severity of the disease as well as the functional loss, while retinal disease did not show significant changes in the inner retinal layers.
Keywords: retina • imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)