Adaptive Optics for Ophthalmic Technologies

Adaptive optics (AO) is an optical technique that corrects the natural aberrations (optical imperfections) of the eye. Since it was first described in 1997, it has been used successfully to enhance the visualization of retinal tissue, in particular, the human photoreceptor mosaic. Previous studies using AO in the human eye have contributed to considerable advancements in our understanding of vision and ocular pathologies.

An AO system sends a pattern of light into the eye that balances the eye's inherent imperfections. This leads to better imaging by providing better light focusing by the natural lens of the eye. The AO system measures the light returning from the eye as is typical in clinically accepted optical coherence tomography and scanning laser ophthalmoscope systems.

A schematic AO system consists of a light input, a deformable/adaptive mirror that modifies the shape of the light entering and exiting the eye, and a detector system that captures and analyzes the returning light from the eye.

The device used in this feasibility study has been tested to ensure that its light output is within ANSI limits for safe ocular exposure and is capable of obtaining useful images of the peripheral retina in normal subjects.

Diabetic retinopathy represents the most common cause of vision loss in working aged adults. Vision loss is related to two manifestations of advanced diabetic retinopathy: proliferative diabetic retinopathy (PDR) and diabetic macular edema (DME). PDR occurs when the vascular perfusion of the retina is compromised and compensatory signals including expression of vascular endothelial growth factor causes neovascularization on the surface of the retina. These abnormal vessels cause vision loss by either bleeding into the vitreous or by contracting leading to retinal detachment. DME occurs when vascular leakage results in swelling of the macular tissue causing central vision loss. While DME affects the macula (the area typically imaged using OCT), PDR is much more frequently found in the peripheral retina which is not typically imaged by traditional OCT devices. In recently years, wide field fluorescein angiography has allowed insights into the relationship between DME, PDR and the status of retinal blood vessels within the macula and the retinal periphery. WF-AO-OCT has the potential to provide similar or complementary structural detail of the retinal tissue and vasculature within the macula and retinal periphery. The advantage of WF-AO-OCT is that it is a non-contact, non-invasive imaging technology which is easier to use, faster and less invasive compared to fluorescein angiography which entails intravenous injection of fluorescein, requires a skilled ophthalmic photographer and takes 10-20 minutes to perform. By imaging participants who have previously undergone wide field fluorescein angiography as standard of care, the investigators will be able to compare the information obtained using WF-AO-OCT and to determine its sensitivity in identifying specific vascular and morphological findings associated with PDR and DME.