Almendral D, Waller S G, Talamo J H
Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA.
J Refract Surg. 1996 May-Jun;12(4):483-91. doi: 10.3928/1081-597X-19960501-12.
Adequate centration of keratorefractive surgical procedures is essential for a successful outcome. An accurate technique to mathematically describe the centration and topography of the ablation zone after photorefractive keratectomy (PRK) would be valuable in assessing the effects of these variables on subsequent visual results.
A vector center of mass formula and computerized videokeratography were used to study the postoperative treatment zone centration and topography of 17 consecutive highly myopic patients (-6.00 to 12.00 diopters [D]). Each had undergone PRK using either a single 6.0 mm (n = 11) or three-stepped ablation zone (n = 6), with good visual results.
Calculations disclosed mean ablation zone decentration relative to the pupil center for all patients to be 0.20 +/- 0.16 mm using the vector center of mass formula. Areas of uniform central corneal dioptric power (mean diameter 3.4 +/- 0.8 mm) and surrounding transition zones of declining dioptric power (mean slope 1.61 +/- 0.44 D/mm) were also determined.
A new vector center of dioptric power distribution that analyzes centration and transition zone topography offers a rigorous but straightforward means to assess the effects of refractive corneal surgery procedures on central corneal topography.
角膜屈光手术的适当对中对于取得成功的手术效果至关重要。一种能以数学方式准确描述准分子激光原位角膜磨镶术（PRK）后消融区对中和地形的技术，对于评估这些变量对后续视觉效果的影响将具有重要价值。
采用矢量质心公式和计算机化角膜地形图仪，对17例连续的高度近视患者（-6.00至12.00屈光度[D]）术后治疗区的对中和地形进行研究。每位患者均接受了PRK手术，其中11例采用单一6.0毫米的消融区，6例采用三步消融区，术后视力良好。
使用矢量质心公式计算得出，所有患者的消融区相对于瞳孔中心的平均偏心为0.20±0.16毫米。还确定了中央角膜屈光力均匀的区域（平均直径3.4±0.8毫米）以及屈光力逐渐下降的周围过渡区（平均斜率1.61±0.44 D/毫米）。
一种新的屈光力分布矢量质心方法，可分析对中和过渡区地形，为评估屈光性角膜手术操作对中央角膜地形的影响提供了一种严谨但直接的手段。
