This article is more than 5 years old. Information may no longer be current.
Luminance trumps color in gauging stimuli in multifocal pupillographic perimetry
J Glaucoma. 2011;20(6):336-343.
Click Here to Manage Email Alerts
Response saturation was identified at higher luminances in all visual field locations in eyes that underwent multifocal pupillographic perimetry, a study found.
"Stimuli with reduced blue light content produced the same signal-to-noise ratios as white stimuli," the study authors said. "Given that these stimuli would not be affected by variable lens brunescence, they might be preferable for perimetry."
The study comprised two arms. The first arm included 16 subjects (mean age: 27.4 years) who underwent yellow multifocal stimuli of varied luminances and presentation rates. The blue channel was turned off on LCD displays used to present stimuli.
The second arm included 18 patients (mean age: 22.3 years) who underwent white, yellow and red stimuli. The second arm was designed to corroborate results of the first arm.
A prototype of the Truefield Analyzer (Seeing Machines) was used to present independent multifocal stimuli to 44 regions of both eyes. Pupil responses were recorded under infrared illumination.
Results of the first and second arms of the study showed reduced response gain, or saturation, at higher luminance in all visual fields. Mean exponents (spherical equivalent) ranged from 0.57 to 0.74, or up to 30 exponents removed from 1, or no saturation.
"The stimulus-response functions appeared to be determined by luminance rather than color," the authors said. "Signal-to-noise ratios and regional visual field sensitivities were similar for all stimulus colors."
Objective perimetry is attractive for many reasons. Patients find the process of having subjective retinal threshold sensitivity measurement to be frustrating, and as a result many patients would prefer not to take standard automated perimetric examinations. In the recent Preferred Practice Pattern for Plaquenil screening, the AAO favored objective tests for retinopathy because they may be more sensitive. The work by Maddess and colleagues demonstrates in normal subjects that when using multifocal pupillographic objective perimetry (mfPOP) reducing the amount of blue light does not change the pupillary response.
This information can possibly be exploited to reduce variability in mfPOP by reducing the amount of blue light in the stimulus, thereby decreasing the variable amounts of blue light absorbed by cataract. Along with the previous work by Maddess and colleagues demonstrating good ability of mfPOP in discriminating glaucoma, this current work suggests that mfPOP may have a significant future role in glaucoma management, particularly for patients who are unreliable subjective test takers.
– Nathan Radcliffe, MD
Assistant
Professor of Ophthalmology, Weill Cornell Medical College
New
York-Presbyterian Hospital, New York
Disclosure: Dr. Radcliffe is a
consultant for Carl Zeiss Meditec.
References:
- Maddess T, Bedford SM, Goh XL, James AC. Multifocal pupillographic visual field testing in glaucoma. Clin Exp Ophthalmol. 2009;37(7):678-686.
- Marmor MF, Kellner U, Lai TY, Lyons JS, Mieler WF. American Academy of Ophthalmology. Revised recommendations on screening for chloroquine and hydroxychloroquine retinopathy. Ophthalmology. 2011;118(2):415-422.