Checking pupils for RAPDs is an important part of the comprehensive eye exam, and is recommended in the AAO’s Preferred Practice Patterns® for POAG suspects and patients, however the swinging flashlight method is difficult for humans to do well, and even more difficult and time consuming to accurately quantify.
Importantly, there is evidence that subtle RAPDs may be clinically significant.
Historical Methods: The “Swinging Flashlight Method”
With origins stemming from the 19th century, this manual and subjective method of detecting an RAPD is commonly known to be difficult to perform well, under the best of circumstances. Although known to be an important physical sign, many well intention-ed doctors report little incidence – not because the sign is not present, but because it is difficult or impossible to detect and it is rarely quantified.
A Perfect Storm
Confounding issues such as minimum contrast (dark iris + black pupil + dark room), anisocoria, misshapen pupils and the lack of standardized light intensity conspire to make the swinging flashlight test even more challenging.
Routine physician assessment of an RAPD has been clinically difficult with any measure of precision. Now with RAPDx, our techs can simply and objectively provide an entirely new level of detail in detection of an APD. Every doc will want one to enhance detection of neuro-affected diseases. This can be very interesting in looking at disease progression at a very early stage.Theodore Krupin, MD
EyeKinetix utilizes a high-definition, machine-vision system under controlled infrared conditions to present monocular visual stimuli while recording bilateral pupil reflexes. Unlike human observers that only see one eye reflex at a time, EyeKinetix simultaneously images both direct and consensual pupillary light reflexes. The power of the system is to collect a series of these reflexes and average them into a consolidated curve.
Pupil testing is notoriously non-standardized, variable, and noisy – averaging significantly helps filter the noise inherent in the biological reflexes.
Easy, objective, quantitative, delegated, detailed… an order of magnitude more detailed than the finest human observer.
The “RAPDx” Signature
EyeKinetix pupillography provides 6 key measurements that make up the fundamentals of the pupil response “Signature”.
- Resting pupil diameter
- Latency, onset of constriction
- Velocity of constriction
- Amplitude of constriction
- Latency, maximum constriction
- Velocity of recovery
This is important new information that clinicians rarely collect reliably or at all.
A differential assessment of the mean of the right eye stimulated responses versus the mean of the left eye stimulated responses are compiled as the “RAPDx Score”.
- The RAPDx score illustrated here indicates that the left eye sees less light (i.e. has the weaker response) and the averaged score is recorded as 0.53 (constriction amplitude differential) in this example.
- Assessed independently as being comparable to the swinging flashlight test when quantified using neutral density filters.
Objective Pupil Assessment
Digital imaging of differential pupil function. Simple for technicians to acquire relevant clinical data.
Dark iris, dark pupil, dark room
The Marcus Gunn sign is a difficult test to perform well. EyeKinetix easily measures asymmetry in the some of the most challenging conditions.
A mathematic assessment of direct and consensual pupil responses between right and left eyes. Humans cannot simultaneously visualize and compare right versus left or consensual vs direct responses.
Beautiful reporting drills down to remarkable detail that humans simply cannot observationally divine.