Prostaglandin-Induced Iris Color Darkening
An Experimental Model
Related URL: http://archopht.ama-assn.org/cgi/content/abstract/116/8/1065
Gui-Lin Zhan, MD; Carol B. Toris, PhD; Carl B. Camras, MD; Yun-Liang Wang, MD; Laszlo Z. Bito, PhD
Arch Ophthalmol. 1998;116:1065-1068.
Objectives To determine the role of sympathetic innervation and the effect of topical prostaglandin therapy on iris color in pigmented rabbits.
Methods Twelve Dutch-belted rabbits underwent unilateral superior cervical ganglionectomy (SCGx) at age 1 to 3 months. A second group of 11 rabbits underwent bilateral SCGx at age 1 month and were treated once or twice daily for 6 to 9 months with 1 drop (about 20 µL) of latanoprost, 0.005%, to one eye and its vehicle to the contralateral eye. Standardized color photographs of the iris of each eye were taken at 1- to 2-month intervals for 6 to 10 months and evaluated by 4 to 6 observers in a masked fashion.
Results At 8 to 10 months after unilateral SCGx, 11 of 12 rabbits showed definite heterochromia, with the lighter-colored iris on the SCGx side. Of the 11 rabbits that underwent bilateral SCGx and unilateral latanoprost treatment, 9 showed heterochromia at 6 to 9 months, with the darker-colored iris on the latanoprost-treated side.
Conclusions These results demonstrate that sympathetic innervation is required for age-related, physiologic darkening of iris color in rabbits, that prostaglandins may compensate for sympathetic denervation to produce darkening in SCGx eyes, and that this model may be useful to study prostaglandin-induced iris color change.
From the Department of Ophthalmology, University of Nebraska Medical Center, Omaha (Drs Zhan, Toris, Camras, and Wang); and the Department of Ophthalmology, Columbia University, New York, NY (Dr Bito). Drs Bito and Camras are consultants to Pharmacia and Upjohn, the company that developed latanoprost. Dr Bito has a proprietary interest in the use of prostaglandins for the medical management of glaucoma through patents he has assigned to Columbia University, New York, NY, according to the policies of the US Public Health Service, National Institutes of Health, Bethesda, Md, which supported the research program of his laboratory in this field between 1970 and 1989.