Differences Between Simulated Keratometry and Total Corneal Power in Eyes With Keratoconus and a Formula to Improve IOL Power Calculation Results

IF 2.9 3区医学 Q1 OPHTHALMOLOGY Journal of refractive surgery Pub Date : 2024-04-01 DOI:10.3928/1081597x-20240311-06

Catarina P. Coutinho, MSc, Domenico Schiano-Lomoriello, MD, Cosimo Mazzotta, MD, PhD, Marco Ferrise, MD, Kenneth J. Hoffer, MD, Filomena J. Ribeiro, MD, PhD, João Mendanha Dias, PhD, Giacomo Savini, MD

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Abstract

Purpose:

To compare simulated keratometry (SimK) and total corneal power (TCP) in keratoconic eyes, to determine whether the differences are systematic and predictable and to evaluate an adjusted TCP-based formula for intraocular lens (IOL) power calculation.

Methods:

In a consecutive series of keratoconic eyes, measurements of SimK, TCP, posterior keratometry, and anterior and posterior corneal asphericities (Q-values) were retrospectively collected. The difference between SimK and TCP was linearly correlated to the biometric parameters. In a separate sample of keratoconic eyes that had undergone cataract surgery, IOL power was calculated with the Barrett Universal II, Hoffer QST, Holladay 1, Kane, and SRK/T formulas using the SimK and an adjusted TCP power. The respective prediction errors were calculated.

Results:

A total of 382 keratoconic eyes (271 patients) were enrolled. An increasing overestimation of SimK by TCP was detected from stage I to III, with a significant correlation between the SimK and TCP difference and SimK in the whole sample (P < .0001, r² = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas.

Conclusions:

Overall, SimK overestimated TCP. Such a difference could not be predicted by any variable. The proposed TCP-adjustment formula (TCP_adj = TCP + 0.56 diopters) in keratoconic eyes for IOL power calculation might be valuable for improving refractive outcomes.

[J Refract Surg. 2024;40(4):e253–e259.]

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角膜炎患者的模拟角膜测量和总角膜力之间的差异以及改进人工晶体力计算结果的公式

目的：比较模拟角膜屈光度（SimK）和角膜总功率（TCP）在角膜炎眼中的差异，确定差异是否系统且可预测，并评估基于TCP的调整后的眼内人工晶体（IOL）功率计算公式。方法：在一系列连续的角膜炎眼中，回顾性地收集了SimK、TCP、后角膜屈光度以及前后角膜非球面度（Q值）的测量值。SimK 和 TCP 之间的差异与生物计量参数呈线性相关。在接受过白内障手术的角膜病变眼的单独样本中，采用巴雷特通用 II、霍弗 QST、霍拉迪 1、凯恩和 SRK/T 公式，使用 SimK 和调整后的 TCP 功率计算人工晶体的功率。结果：共有 382 只角膜病变眼（271 名患者）入组。在整个样本中，SimK 和 TCP 差值与 SimK 之间存在显著相关性（P < .0001，r2 = 0.1322）。约有 7% 的病例显示 TCP 低估了 SimK。使用调整后的 TCP 计算人工晶体力量改善了结果，使用 Hoffer QST、Holladay 1 和 Kane 公式预测误差在±0.50 屈光度以内的眼最多达到 80%。结论：总的来说，SimK 高估了 TCP，这种差异是任何变量都无法预测的。在计算角膜病变眼的 IOL 功率时，所提出的 TCP 调整公式（TCPadj = TCP + 0.56 斜度）可能对改善屈光结果很有价值。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

$Journal of refractive surgery$

Journal of refractive surgery 医学-外科

CiteScore

5.10

自引率

12.50%

发文量

160

审稿时长

4-8 weeks

期刊介绍： The Journal of Refractive Surgery, the official journal of the International Society of Refractive Surgery, a partner of the American Academy of Ophthalmology, has been a monthly peer-reviewed forum for original research, review, and evaluation of refractive and lens-based surgical procedures for more than 30 years. Practical, clinically valuable articles provide readers with the most up-to-date information regarding advances in the field of refractive surgery. Begin to explore the Journal and all of its great benefits such as: • Columns including “Translational Science,” “Surgical Techniques,” and “Biomechanics” • Supplemental videos and materials available for many articles • Access to current articles, as well as several years of archived content • Articles posted online just 2 months after acceptance.