A Prospective Single-Site Non-Interventional Study to Evaluate the Diagnostic Accuracy and Repeatability of Pupil Measurements Using a Prototype Binocular Optical Coherence Tomography System.

Binocular OCT has the potential to allow for objective, quantitative measurement of pupillary reflexes, that can be performed in a fast, safe, and automated manner. Importantly, binocular OCT pupillometry can be performed alongside binocular retinal OCT imaging in a single testing session, in an automated manner (imaging of the retina using OCT is the commonest ophthalmic imaging procedure worldwide - in 2011, it is estimated that more than 20 million retinal OCT images were obtained, more than the sum of all other ophthalmic imaging procedures combined).

Assessment of pupillary reflexes is an essential component of a comprehensive ocular examination. In patients with visual loss, for example, detection of an RAPD often indicates the presence of serious ophthalmic diseases, such as optic neuropathies or severe retinal disease. As such, RAPD testing is essential as a screening test in the assessment of patients with less serious conditions such as cataract.

RAPD testing is commonly performed using the swinging flashlight method (SFM). A positive SFM test suggests the presence of asymmetric damage involving the afferent limb of the pupillary light reflex pathway. The SFM is a qualitative test, and relies upon visualising no pupillary constriction or immediate or delayed pupillary dilation; if either of these responses is observed, an RAPD is believed to be present. The SFM requires a trained examiner and many potential sources of error may confound the results, including anisocoria, off-axis pupil illumination, and unequal retinal bleaching. Pupil abnormalities may be subtle and easily missed using the SFM.

Automated pupilometers allow examiners to precisely and objectively quantify the pupillary response to light by measuring parameters such as minimum and maximum pupil diameter, the amplitude of constriction, latency of constriction, velocity of constriction, and duration of maximum constriction. Dedicated pupillometry devices are commercially available and have been shown to be highly sensitive and specific for RAPD detection e.g. RAPDx; Konan Medical USA, Inc., Irvine, CA. These devices are also capable of detecting the presence of more subtle RAPD, typically not found using the SFM, in diseases such as glaucoma.

Unfortunately, automated pupilometers such as the Konan RAPDx system are not widely used in clinical practice. This is largely because they are expensive devices, limited to a single purpose. A binocular OCT system that could perform both automated pupillometry and retinal OCT imaging would thus have great clinical utility.