Human color vision deficits induced by accidental laser exposure and potential for long-term recovery

Abstract

Purpose: To evaluate long term deficits in human color discrimination induced by accidental laser macular damage and assess potential for recovery of color vision deficits. Methods: Nine laser accident cases (Q-switched Neodymium) presenting initially with confined or vitreous macular hemorrhage were evaluated with the Farnsworth-Munsell 100 Hue test within 2 days to 3 months post exposure. Both total as well as partial errors in the blue/yellow (B/Y) and red/green (R/G) regions were assessed. Independent assessment of axis orientation and complexity were obtained via a Fourier series expansion of error scores. Comparisons of both total and partial B/Y and R/G errors were made with age matched normal subjects, idiopathic and juvenile onset macular holes. Confocal Scanning Laser Ophthalmoscopy and Optical Coherence Tomography characterized the presence of retinal traction, intraretinal scar, macular thickness and macular hole formation. Results: Comparison of exposed and non-exposed age matched individuals was significant (P< .001) for both total and partial errors. In four cases where macular injury ranged from mild scar to macular hole, color discrimination errors achieved normal levels in 1 to 12 months post exposure. A mild tritan axis, dominant B/Y (blue/yellow) errors, and retinal traction were observed in a macular hole case. At 12 months post exposure, traction about the hole disappeared, and total and partial errors were normal. Where damage involved a greater degree of scarring, retinal traction and multiple injury sites, long-term recovery of total and partial error recovery was retarded with complex axis makeup. Single exposures in the paramacula produced tritan axes, while multiple exposures within and external to the macula increased total and partial R/G (red/green) error scores. Total errors increased when paramacular hole enlargement induced macular traction. Such hole formation produced significant increases in total errors, complex axis formation and increased amplitude in higher Fourier error expansion components. Conclusion: Color discrimination losses reflect the distribution of different cone systems in and about the macula and their selective loss. When secondary damage is minimal, color discrimination deficits recover within 12 months post exposure. When macular scarring and retinal traction are severe, recovery is significantly retarded. Laser induced macular holes may affect color discrimination less when retinal scar and traction are small but may become equivalent with that of idiopathic and juvenile species when scar and traction are severe. Key words: laser, fovea, injury, color discrimination, visual acuity, case histories