Red Desaturation Prevalence and Severity in Healthy Patients

Abstract

Objective:To determine the percentage of the healthy population that responds asymmetrically to the red desaturation test, and to approximate the degree of red desaturation in those individuals. We also sought to elucidate any correlation between demographic variables and red desaturation prevalence and severity.Methods:Adults aged 18 and older with a normal eye exam, including confrontation fields and best-corrected visual acuity of ≥ 20/25 OU, were eligible for this prevalence study. Those with objective or subjective afferent visual dysfunction were excluded. A total of 101 eligible participants (31.7% male; 77.2% white race; mean (SD) age: 41.5 (15.3) years) were queried whether monocular perception of redness of a standardized tropicamide bottle cap was the same and to estimate the interocular percentage difference, with one eye perceiving the bottle cap at “100% redness.”Results:Twenty-four participants (23.8%) experienced some degree of red desaturation. For these individuals with red desaturation, the average interocular difference was 9.0% (range 2-25%, 95% CI: 6.0-12.0%). There was no statistical evidence for a relationship between red desaturation and race, sex, or age.Conclusion:This study shows that nearly a quarter of healthy patients without apparent optic nerve or macular dysfunction may recognize red desaturation. This deserves consideration when interpreting red desaturation testing in patients suspected to have unilateral optic neuropathy. Further research with larger sample sizes may identify predictors of red desaturation in healthy patients, establish the red desaturation threshold separating pathologic from physiologic phenomena, and assess the repeatability of red desaturation over time in affected individuals.

Evaluation of the Reddesa Chart, a New Red Desaturation Testing Method, for Optic Neuritis Screening and Grading in Clinical Routine

“…In addition, a low specifity of the red cap test has been reported (up to 25% wrong answers). This might lead to erroneously diagnose an optic neuritis in patients with no optic neuritis ( 10 , 11 ). In our study, there were no wrong answers in the control group, both in the red cap test and in the Reddesa test.…”

“…Red objects presented to such patients are perceived as grayish due to the reduced red saturation compared to the other healthy eye. Often, the red cap of topical ocular medications is presented to the patient, hence the name “red cap test.” However, up to 25% of patients without apparent optic neuritis are false positive in the red cap test ( 10 ). The quantification of color defects, e.g., with neutral density filters, is not commonly done by practitioners.…”