Purpose: To examine the direct relationship between the extent of treatment with krypton red laser photocoagulation and visual acuity loss in eyes with choroidal neovascularization secondary to ocular histoplasmosis or age-related macular degeneration.
Patients and methods: Photographic and visual acuity records from 129 eyes treated in the Ocular Histoplasmosis Study--Krypton Laser and 224 eyes treated in the Age-Related Macular Degeneration Study--Krypton Laser were reviewed. The proportion of eyes with severe visual acuity loss (6 or more lines of loss) was examined for subgroups of eyes based on the distance of the neovascular lesion from the center of the foveal avascular zone and on the extent of laser treatment to the lesion. Differences in the proportions with severe visual acuity loss were evaluated by longitudinal data analysis methods.
Results: Among eyes in the Ocular Histoplasmosis Study--Krypton Laser with lesions less than 200 microns from the center of the foveal avascular zone, only 5% of eyes with laser treatment that covered the foveal side and had a narrow (< or = 100 microns) border of treatment to adjacent uninvolved retina experienced severe visual acuity loss compared with approximately 25% of eyes with either some of the foveal side of the lesion left untreated or a wide border of treatment on the foveal side. Treatment extent had little influence on severe visual acuity loss in eyes in the Ocular Histoplasmosis Study--Krypton Laser with neovascular lesions 200 to 500 microns from the center of the foveal avascular zone or in eyes in the Age-Related Macular Degeneration Study--Krypton Laser with lesions in either distance category.
Conclusions: Accurate, complete treatment of choroidal neovascularization close to the foveal center is required to provide the patient with the best chance of avoiding further severe visual acuity loss, especially in patients with ocular histoplasmosis. Even among experienced retinal specialists, the required accuracy of treatment is difficult to achieve.