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LETTERS

Importance of corneal topography in surgical planning for toric intraocular lenses

Aghaei, Hossein MD; Es'haghi, Acieh MD

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Journal of Cataract & Refractive Surgery: October 2020 - Volume 46 - Issue 10 - p 1450
doi: 10.1097/j.jcrs.0000000000000387
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The study by Sheen Ophir et al. investigated the outcomes of toric intraocular lens implantation (IOL) in eyes with preexisting oblique anterior corneal astigmatism.1 The authors stated that repeated measurements were continued by both automated keratometry and IOLMaster (Carl Zeiss Meditec AG) to achieve differences less than 0.50 diopter in power and 10 degrees in axis of astigmatism. However, it would be more appropriate to consider the effect of possible corneal irregularities in astigmatic outcome in such patients because this discrepancy might have resulted from irregular corneal surface. Furthermore, the authors did not provide enough data about their eligibility criteria regarding corneal topographic measurements in this case series. Extreme caution must be exercised when there is any mismatch between keratometric values to rule out mild ectatic disorders and irregular corneal astigmatism.2,3

Although obtaining keratometric measurements by different techniques including automated keratometry and IOLMaster are comparable in most cases, it might not be reasonable to perform toric IOL implantation without assessing corneal topography because of the inconsistency in different refractive indices and areas used by different devices. It has been demonstrated that automated keratometry performs poorly when applied to measure the location of the axis and magnitude of corneal astigmatism in suboptimal ocular surfaces.3,4

Corneal topography is a prerequisite to obtain reliable measurements of astigmatism and axial position in candidates for toric IOL. That would especially be of importance in the presence of any disagreements between measurements using optical biometer and automated keratometry to achieve postoperative optimal refractive outcome because the 2 methods would have led to error in astigmatic measurements in eyes with oblique astigmatism.4

REFERENCES

1. Sheen Ophir S, LaHood B, Goggin M. Refractive outcome of toric intraocular lens calculation in cases of oblique anterior corneal astigmatism. J Cataract Refract Surg 2020;46:688–693
2. Galindo-Ferreiro A, De Miguel-Gutierrez J, González-Sagrado M, Galvez-Ruiz A, Khandekar R, Schellini S, Galindo-Alonso J. Validity of autorefractor based screening method for irregular astigmatism compared to the corneal topography- a cross sectional study. Int J Ophthalmol 2017;10:1412–1418
3. Cua IY, Qazi MA, Lee SF, Pepose JS. Intraocular lens calculations in patients with corneal scarring and irregular astigmatism. J Cataract Refract Surg 2003;29:1352–1357
4. Lee H, Chung JL, Kim EK, Sgrignoli B, Kim TI. Univariate and bivariate polar value analysis of corneal astigmatism measurements obtained with 6 instruments. J Cataract Refract Surg 2012;38:1608–1615
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