Browse the corpus

Adaptive optics (AO) is a technique for imaging the retina at the cellular level by correcting optical aberrations inherent to the eye. In vivo examination of the individual photoreceptors and retinal vasculature may help understand retinal pathologies better. All available investigative modalities for retinal diseases detect them only after visible fundus changes occur. Adaptive optics may aid in recognizing them before significant damage sets in and may help develop newer treatment modalities. However, its use is currently limited to research as various challenges like cost and availability must be overcome before being implemented in day-to-day practice. This activity summarizes the basic principles and advantages of adaptive optics and its potential in diagnosing and treating retinal disorders. Objectives: Describe the principle of adaptive optics. Summarize the clinical applications of adaptive optics in ophthalmology. Outline the photoreceptor imaging characteristics briefly in healthy eyes and disease conditions. Summarize the challenges involved in implementing adaptive optics in clinical practice. Access free multiple choice questions on this topic.

Light traveling through any media other than vacuum undergoes aberrations due to changes in the refractive index and interface of the medium.[1] Similarly, rays exiting the eye also have wavefront aberrations contributed by the differences in the refractive index of ocular tissues. The wavefront aberrations are classified as chromatic and monochromatic aberrations.[2] The monochromatic aberrations are further classified as lower order (contribute to about 90% of total aberrations) and higher order aberrations (10% of total aberrations). Spherical and cylindrical lenses correct the lower-order aberrations. The higher-order aberrations responsible for limiting the lateral resolution of devices are unique to each patient's eye and were deemed un-rectifiable until recently.[3] In 1971, the Shack-Hartmann wavefront sensor (SHWS) measured the eye's possible optical aberrations.[4] In 1953, Horace Babcock from the Carnegie laboratories proposed Adaptive optics (AO) for the clear visualization of astronomical bodies, the images distorted by the aberrations in the incident rays due to the turbulence in the earth's atmosphere.[5] In 1997 Liang et al. employed this same principle in retinal imaging to overcome higher-order aberrations.[6] They used the SHWS and deformable mirrors to demonstrate cone photoreceptors in vivo. They concluded AO might help image the live retina at the microscopic level by improving the lateral resolution immensely. Roorda was the first to use AO clinically in a patient with inherited rod-cone dystrophy in 2000.[7] Though AO technology has evolved in the last two decades, no Food and Drug Administration, USA (FDA) approved devices for clinical use exist. Recently, an AO flood illumination device has been approved for marketing in the European Union, China, and Japan.[8]

There are no complications associated with Adaptive optics imaging as it is a non-invasive procedure. However, patients with cervical spine pathologies, anxious patients, debilitated individuals, and patients with low vision and ocular motility disorders may find it challenging to maintain fixation for longer.

Adaptive optics helps in non-invasive cellular imaging of the retina. Image acquisition and interpretation require trained personnel to capture good-quality images and interpret them. Image acquisition is time-consuming but has been reduced to 2 seconds in newer machines. Nurses and ophthalmic photographers play a pivotal role in helping the patient maintain fixation and remain comfortable throughout the procedure. Training of allied ophthalmic personnel may also reduce the burden on treating physicians. It is necessary that all professionals involved in the process of image acquisition are educated and aware of the clinical significance of adaptive optics.