Fagj. Eggink et al., ENLARGEMENT OF THE PHOTOREFRACTIVE KERATECTOMY OPTICAL ZONE, Journal of cataract and refractive surgery, 22(9), 1996, pp. 1159-1164
Purpose: To evaluate the safety and efficacy of a photorefractive kera
tectomy (PRK) re-treatment procedure that enlarges the optical zone an
d treats undercorrection. Setting: Rotterdam Eye Hospital and Medisch
Centrum Alkmaar, The Netherlands. Methods: This study evaluated 16 eye
s that had PRK for myopia with the Summit excimer laser that resulted
in a mean undercorrection of -2.82 diopters (D). Patients also reporte
d impaired night vision including difficulty in driving, halos, and st
ray light and ghost images. These phenomena persisted after spectacle
correction of residual refractive error, necessitating further treatme
nt with a larger ablation zone. With a VISX 20/20 excimer laser, the o
ptical zone was enlarged to 6.0 mm and undercorrection treated with a
6.0 mm ablation. Results: At 13.5 months after re-treatment, mean redu
ction in myopia was 1.70 D, resulting in a residual undercorrection of
-1.08 D. In seven eyes, final refraction was within 1.00 D of emmetro
pia. Only two patients continued to report night-driving problems. Con
clusions: Re-treating undercorrections combined with enlarging the abl
ation zone resulted in a reduction in myopia from a mean of 2.82 to 1.
08 D. Subjective reports of halos and stray light images were decrease
d in all cases.