Kam Ka Wai, Li Anita, Kwok Rachel Pui Wai, Belin Michael W, Young Alvin L
Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong.
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong.
Int Ophthalmol. 2019 Apr;39(4):911-916. doi: 10.1007/s10792-018-0897-z. Epub 2018 Jun 19.
We aim to design two sampling methods, the grid and sectoral methods, to provide more precise detection of focal corneal scar changes with time following pterygium excision with the Pentacam imaging system.
This is a retrospective study of our previous prospective observational case series. Thirty patients underwent primary pterygium excision with adjuvant topical mitomycin-C application were followed up and imaged with Pentacam system at postoperative weeks 1, 4, 12 and month 18. Grid and sectoral methods were used to sample density changes (in grayscale units, GSU) over the scarred areas as well as the clear pole of the same cornea.
Using the grid method, the average corneal densities were 39.4, 37.1, 36.7 and 34.7 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. On the other hand, using the sectoral method, the average corneal densities were 35.3, 33.3, 32.5 and 31.9 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. Paired t tests achieved statistical significance when comparing all follow-up time points to first postoperative visit. A statistically significant effect of time on the average density was shown on ANOVA (p < 0.001) using both analyses over the scarred areas, but not over the clear pole of the same cornea (p > 0.05).
Our novel approach to monitor corneal density changes using the grid or sectoral sampling methods seemingly enhances the power in monitoring density changes in corneal scars when compared to conventional total-diameter average densitometry.
我们旨在设计两种采样方法，即网格法和扇形法，以便使用Pentacam成像系统更精确地检测翼状胬肉切除术后角膜瘢痕随时间的变化。
这是一项对我们之前前瞻性观察病例系列的回顾性研究。30例接受原发性翼状胬肉切除并辅助局部应用丝裂霉素C的患者在术后第1周、第4周、第12周和第18个月进行随访，并用Pentacam系统进行成像。使用网格法和扇形法对瘢痕区域以及同一角膜的透明区进行密度变化（以灰度单位，GSU表示）采样。
使用网格法时，术后1周、4周、12周和18个月时角膜平均密度分别为39.4、37.1、36.7和34.7 GSU。另一方面，使用扇形法时，术后1周、4周、12周和18个月时角膜平均密度分别为35.3、33.3、32.5和31.9 GSU。将所有随访时间点与术后首次就诊进行比较时，配对t检验具有统计学意义。在瘢痕区域进行的两种分析中，方差分析（ANOVA）显示时间对平均密度有统计学显著影响（p < 0.001），但在同一角膜的透明区则无此影响（p > 0.05）。
与传统的全直径平均密度测量法相比，我们使用网格或扇形采样方法监测角膜密度变化的新方法似乎增强了监测角膜瘢痕密度变化的能力。
