THE HIDDEN BURDEN: VISUAL QUALITY OF LIFE AND CONTRAST SENSITIVITY DEFICITS IN "CLINICALLY RECOVERED" OPTIC NEURITIS PATIENTS

Abstract

Background: Standard visual recovery in optic neuritis (ON) is traditionally defined by a return to normal high contrast visual acuity (HCVA). This study evaluates hidden contrast sensitivity (CS) deficits in "clinically recovered" ON patients and their resulting impact on vision-related quality of life (VRQoL). Methods: A prospective, cross-sectional study compared 50 clinically recovered ON patients demonstrating normal HCVA (≥ 20/20) against 50 matched healthy controls. Visual and structural assessments included Pelli-Robson CS, Sloan low-contrast letter acuity (LCLA), optical coherence tomography (OCT), visual evoked potentials (VEP), and the NEI VFQ-25 questionnaire to assess VRQoL. Results: Despite their normal HCVA, the ON cohort demonstrated significantly reduced CS and severe LCLA drop-offs at the 2.5% and 1.25% contrast levels compared to controls. Additionally, OCT revealed significant global retinal nerve fiber layer (RNFL) thinning and VEP testing showed prolonged P100 latencies indicating delayed neural conduction. These hidden structural and functional deficits strongly correlated with significantly lower VRQoL composite scores, specifically impairing the driving and mental health domains. RNFL thinning and CS deficits were tightly correlated with quality of life declines, whereas standard HCVA was not.  Conclusion: Relying exclusively on HCVA fails to capture persistent, debilitating visual disabilities in clinically recovered ON patients. Incorporating CS testing and OCT structural imaging into standard clinical evaluations is crucial for measuring true functional recovery.