Purpose

To determine whether differences between eyes in axial length (AL) and corneal power (K) on optical biometry are predictive of refractive outcomes.

Design

Retrospective cohort study.

Participants

A total of 729 patients (1458 eyes) who underwent bilateral phacoemulsification at TLC (Mississauga, Ontario, Canada) from September 2013 to August 2015.

Methods

We compared the proportion of patients having >0.5 diopters (D) of refractive error from target stratified by interocular axial length differences (IALDs) and interocular K differences (IKDs) between eyes as measured by optical biometry (IOL-Master, Carl Zeiss Meditec, Oberkochen, Germany). Analysis was repeated for 0.25 D or 1.0 D targets and for patients with uncorrected visual acuity (UCVA) >0.3 logarithm of the minimum angle of resolution (logMAR) postoperatively.

Main Outcome Measures

Proportions, odds ratios (ORs), and corresponding 95% confidence intervals (CIs) were computed using generalized estimating equations to account for within-patient correlation.

Results

Some 79.1% of eyes were ≤0.5 D of refractive target, 47.0% were ≤0.25 D, and 97.2% were ≤1.0 D. The OR of having a refractive outcome >0.5 D from target for IALD cutoff of 0.2 mm was 1.4 (1.1–1.8), of 0.3 mm was 1.6 (1.2–2.1), and of 0.4 mm was 1.8 (1.3–2.5). This translates to 70.0% (63.5–75.7) within target for IALD of ≥0.4 mm versus 80.7% (78.4–82.9) for <0.4 mm. For a given patient with IALD, the chance of being off target was similar for the shorter and longer eye. Eyes outside of target were twice as likely to be <−0.5 D than >0.5 D. Interocular K difference was largely not associated with prediction error, yet larger IKD-flat, steep, and average were associated with increased odds of UCVA >0.3 logMAR postoperatively.

Conclusions

Interocular axial length difference of as little as ≥0.2 mm is associated with a higher chance of >0.5 D of refractive error from target and worse UCVA. Interocular K difference was not associated with worse refractive error from target, although a difference of ≥0.4 D was associated with worse UCVA. These cutoffs should be considered in preoperative planning and discussion with patients. Future study is required to assess whether repeating measurements, using adjunctive measurement devices, or attempting to separate true differences from artifact based on preoperative refractive characteristics reduces residual refractive error.

中文翻译：

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眼轴长度和角膜屈光力差异作为白内障手术后术后屈光结果的预测指标

目的

为了确定光学生物测定法上眼睛的眼轴长度（AL）和角膜屈光力（K）之间的差异是否可预测屈光结果。

设计

回顾性队列研究。

参加者

2013年9月至2015年8月，共有729例患者（1458眼）在TLC（密西沙加，安大略省，加拿大）接受了双侧超声乳化手术。

方法

我们比较了通过光学生物测定法（IOL-Master，Carl Zeiss Meditec，德国Oberkochen）。重复分析0.25 D或1.0 D靶标，并对术后未矫正视敏度（UCVA）>最小分辨角（logMAR）的0.3对数的患者进行重复分析。

主要观察指标

使用广义估计方程计算比例，比值比（OR）和相应的95％置信区间（CI），以说明患者内的相关性。

结果

约有79.1％的眼睛的屈光目标≤0.5 D，有47.0％的眼≤0.25D，有97.2％的眼≤1.0D。对于0.2 mm IALD截止，从目标屈光结果> 0.5 D的OR为1.4（1.1 –1.8），0.3毫米为1.6（1.2-2.1），而0.4毫米为1.8（1.3-2.5）。对于≥0.4mm的IALD，这相当于目标范围内70.0％（63.5–75.7），而对于<0.4 mm的IALD，目标值为80.7％（78.4–82.9）。对于给定的IALD患者，较短和较长的眼睛脱靶的可能性相似。目标外的眼睛<-0.5 D的可能性是> 0.5 D的两倍。眼间K差异在很大程度上与预测误差无关，但更大的IKD平坦度，陡峭度和平均值与UCVA> 0.3 logMAR的几率增加相关术后。

结论

眼内轴长差小于或等于0.2 mm，与目标屈光不正> 0.5 D的机会较高，而UCVA较差有关。眼内K差异与目标屈光不正无关，尽管差异≥0.4D与UCVA较差有关。在进行术前计划和与患者讨论时，应考虑这些临界值。需要进行进一步的研究，以评估重复测量，使用辅助测量设备还是尝试根据术前屈光特性将真实差异与伪影分开，是否可以减少残留屈光误差。