Department of Cataract Surgery, Shenyang Aier Eye Optometry Hospital, Shenyang, China.
Indian J Ophthalmol. 2023 Aug;71(8):2967-2971. doi: 10.4103/IJO.IJO_3385_22.
To evaluate whether the toric intra-ocular lens (IOL) power calculation based on total corneal astigmatism (TCA) in eyes with high posterior corneal astigmatism (PCA) could result in a systematic over-correction or under-correction after operation.
The present study included a mono-centric retrospective study design. The data were collected from 62 consecutive eyes during uncomplicated cataract surgery by a single surgeon with a measured PCA of 0.50 diopters (D) or higher. Toric IOL calculations were made using TCA measurements. The eyes were grouped as either "with-the-rule" (WTR) or "against-the-rule" (ATR) on the basis of the steep anterior corneal meridian. The post-operative refractive astigmatic prediction error was analyzed 1 month post-operatively using the vector analysis by the Alpins method and double-angle plots method.
The correction indexes were 1.14 ± 0.29 in the ATR eyes and 1.25 ± 0.18 for the WTR eyes, indicating a tendency toward over-correction. The mean over-correction was 0.22 ± 0.52D in the ATR group and 0.65 ± 0.60D in the WTR group. The magnitude of error (ME) values were significantly different from the ideal value of zero in both groups (ATR: P = 0.03; WTR: P = 0.00). No significant difference in mean absolute error (MAE) in predicted residual astigmatism was found between ATR and WTR groups (0.61 ± 0.42 D versus 0.64 ± 0.39 D; P = 0.54). The ATR group yielded better results, with 48% <0.50D prediction error in the main analysis.
The results suggested that in cases of high PCA, the toric IOL calculation, which was performed using TCA, may cause a potential over-correction in the ATR and WTR eyes. For ATR eyes, over-correction led to slight disruption of post-operative visual quality because of the "with-the-rule" residual astigmatism after operation. Therefore, we suggested using TCA for toric IOL calculation in ATR eyes.
评估在高后角膜散光（PCA）的眼中，基于总角膜散光（TCA）的散光人工晶状体（IOL）的计算是否会导致术后的系统过矫或欠矫。
本研究包括一项单中心回顾性研究设计。研究数据来自于 62 例由同一位医生进行的单纯白内障手术的连续眼，这些眼的测量 PCA 为 0.50 屈光度（D）或更高。使用 TCA 测量值计算散光 IOL。根据陡峭的前角膜子午线，将眼分为“顺规性”（WTR）或“逆规性”（ATR）。术后 1 个月，采用 Alpins 方法的矢量分析和双角图法分析术后屈光性散光预测误差。
ATR 眼的矫正指数为 1.14 ± 0.29，WTR 眼为 1.25 ± 0.18，表明存在过矫趋势。ATR 组的平均过矫量为 0.22 ± 0.52D，WTR 组为 0.65 ± 0.60D。两组的误差（ME）值均显著偏离零的理想值（ATR：P = 0.03；WTR：P = 0.00）。ATR 组与 WTR 组之间预测残余散光的平均绝对误差（MAE）无显著差异（0.61 ± 0.42D 与 0.64 ± 0.39D；P = 0.54）。ATR 组的结果更好，主要分析中 48%的眼<0.50D 预测误差。
结果表明，在高 PCA 的情况下，使用 TCA 进行的散光 IOL 计算可能会导致 ATR 和 WTR 眼中潜在的过矫。对于 ATR 眼，过矫导致术后“顺规性”残余散光，轻微破坏术后视觉质量。因此，我们建议在 ATR 眼中使用 TCA 进行散光 IOL 计算。
