Lin D T
Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Ophthalmology. 1994 Aug;101(8):1432-9. doi: 10.1016/s0161-6420(94)31154-7.
A 2-year experience with corneal topography after photorefractive keratectomy (PRK) is reported, specifically reviewing the correlation of surface regularity index versus best spectacle-corrected visual acuity as a function of various ablation patterns. Centration and stability issues also are discussed.
Excimer laser PRK for myopia was performed on 502 consecutive eyes. Corneal topographic analysis was performed at the 1-, 3-, 6-, and 12-month postoperative follow-up visits. In all patients, PRK was performed with an argon fluoride laser, and a topographic analysis was done.
Topographic analysis at the first postoperative month was useful for determining decentration of the optical zone. The mean decentration from the pupillary center for all eyes was 0.34 mm. Four main patterns of ablation were noted by subtraction analysis. At the 1-month postoperative examination, a "uniform" ablation was present in 44% of eyes, "keyhole" ablations were present in 12% of eyes, "semicircular" ablations were present in 18% of eyes, and an unusual "central island" was present in the remaining 26% of eyes. However, on subsequent follow-up the central islands tended to resolve with time. At 3 months postoperatively, 18% of eyes in that group showed a central island, 8% showed a central island at 6 months, and only 2% of eyes showed a central island at the 12-month postoperative visit. Correlation of central island topography with visual acuity and progressive hyperopia are discussed.
Corneal topography is essential for evaluating surface changes after excimer PRK. The surface regularity index is a good indicator of best spectacle-corrected visual acuity and is used to evaluate irregular astigmatism after PRK. Central island topographies are correlated with poor initial visual rehabilitation. Long-term stability issues are answered with continued topographic follow-up. Understanding corneal hydration changes between the central and peripheral cornea may help us understand the etiology of central islands.
报告了准分子激光原位角膜磨镶术（PRK）后两年的角膜地形图研究经验，特别回顾了表面规则性指数与最佳矫正视力之间的相关性，以及不同消融模式的作用。还讨论了中心定位和稳定性问题。
对502只连续的眼睛进行准分子激光PRK治疗近视。在术后1个月、3个月、6个月和12个月的随访中进行角膜地形图分析。所有患者均使用氟化氩激光进行PRK，并进行地形图分析。
术后第一个月的地形图分析有助于确定光学区的偏心情况。所有眼睛离瞳孔中心的平均偏心距离为0.34毫米。通过减法分析发现了四种主要的消融模式。在术后1个月的检查中，44%的眼睛呈现“均匀”消融，12%的眼睛呈现“钥匙孔”消融，18%的眼睛呈现“半圆形”消融，其余26%的眼睛呈现不寻常的“中央岛”。然而，在随后的随访中，中央岛往往会随着时间的推移而消退。术后3个月，该组中18%的眼睛出现中央岛，6个月时8%的眼睛出现中央岛，术后12个月时只有2%的眼睛出现中央岛。讨论了中央岛地形图与视力和渐进性远视的相关性。
角膜地形图对于评估准分子激光PRK术后的表面变化至关重要。表面规则性指数是最佳矫正视力的良好指标，用于评估PRK术后的不规则散光。中央岛地形图与初期视力恢复不佳相关。通过持续的地形图随访可以解决长期稳定性问题。了解中央角膜和周边角膜之间的水化变化可能有助于我们理解中央岛的病因。
