Rs. Kalski et al., COMPARISON OF 5-MM AND 6-MM ABLATION ZONES IN PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA, Journal of refractive surgery, 12(1), 1996, pp. 61-67
BACKGROUND: Variation in ablation zone diameter may alter visual acuit
y and/or refractive effect in photorefractive keratectomy. Despite the
oretical benefits of using a smaller diameter ablation zone, clinical
studies suggest that a larger ablation zone may decrease problems asso
ciated with photorefractive keratectomy. METHODS: The results of our i
nitial 34 consecutive eyes treated with a 5-mm diameter ablation zone
using a Summit Technology ExciMed UV200LA excimer laser were compared
retrospectively to our initial 34 consecutive eyes treated with a 6-mm
diameter ablation zone using a Summit OmniMed excimer laser. Eyes had
a spherical equivalent refraction between -1.00 and -6.00 diopters (D
) and astigmatism less than 1.00 D. Patients were followed for a minim
um of 6 months. RESULTS: Eyes treated with a 6-mm ablation zone had le
ss hyperopia and a spherical equivalent refraction closer to emmetropi
a at 1, 2, and 3 months (P=0.001). Eyes treated with a 6-mm ablation z
one had better uncorrected visual acuity at 1 and 2 months (P=0.001).
Less subepithelial haze was noted at 2 months (P=0.01) and 3 months (P
=0.002) in the 6-mm group. At 6 months postoperatively, 30 of 32 eyes
(94%) treated with a 6-mm ablation zone had a spherical equivalent ref
raction within 0.50 D of emmetropia, and all 32 eyes (100%) were withi
n 1.00 D of emmetropia; in the 5-mm ablation zone group, 28 of 34 eyes
(80%) were within 0.50 D and 29 (85%) were within 1.00 D of emmetropi
a. Patients treated with a 6-mm ablation zone complained less of night
halos and had fewer differences between night and day vision. CONCLUS
IONS: In this study of myopia of -1.00 D to -6.00 D, eyes treated with
a 6-mm ablation zone achieve a more rapid visual recovery with less v
ariation in refractive outcome and less adverse effects than those tre
ated with a 5-mm ablation zone.