J Korean Ophthalmol Soc.  2014 Nov;55(11):1613-1617. 10.3341/jkos.2014.55.11.1613.

The Prediction of Changes in Mean Corneal Refractive Power by Pterygium Size after Pterygium Surgery

• Nam KT
• Eom YS
• Rhim JW
• Kang SY
• Kim HM
• Song JS

• KMID: 2216608
• DOI: http://doi.org/10.3341/jkos.2014.55.11.1613

Abstract

PURPOSE
To assess the changes in mean corneal refractive power (DeltaK) following pterygium surgery and to predict DeltaK in cases of combined cataract and pterygium surgery.
METHODS
Thirty-seven eyes of unilateral pterygium patients who underwent pterygium surgery were analyzed retrospectively with at least more than 1 month of follow-up. Preoperative and postoperative 1 month corneal refractive power was measured using auto-keratometer (RK-F1, Canon, Tokyo, Japan). Pterygium horizontal extension, width, and area were measured and correlation with DeltaK before and after surgery analyzed. We also compared DeltaK of the contralateral normal eye.
RESULTS
The mean corneal refractive (Km) power measured before and 1 month after surgery was 43.30 +/- 1.66 D and 44.07 +/- 1.42 D, respectively. The Km significantly increased at 4 weeks after surgery (p < 0.001). However, postoperative Km was not significantly different when compared with the contralateral normal eye (43.86 +/- 1.34 D; p = 0.59). All parameters of pterygium size including horizontal extension, width, and area were positively correlated with the mean DeltaK. Among parameters, horizontal extension was best correlated with mean DeltaK (p < 0.001). The mean DeltaK with horizontal extension was predicted using linear regression (2.5 mm to 1 D, 4.0 mm to 1.8 D).
CONCLUSIONS
We recommend contralateral corneal refractive power or prediction of corneal refractive power using linear regression with pterygium horizontal extension for determining intraocular lens power in cases of combined cataract and pterygium surgery.

Keyword

Intraocular lens power calculation; Mean corneal power; Pterygium

MeSH Terms

Cataract
Follow-Up Studies
Humans
Lenses, Intraocular
Linear Models
Pterygium*
Retrospective Studies

Figure

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  Figure 1. The parameter of pterygium size by graphic program. The horizontal extension of pterygium on cornea (A) was measured between the nasal limbus and the point farthest away from the limbus and the width (B) was the base arc between 2 limbal points where the pterygium intersected with the limbus. Each area of entire cornea (C) and pterygium on cornea (D) was measured and then the area ratio of pterygium (D/C × 100) was calculated with proportion of pterygium invaded onto the cornea.

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  Figure 2. Scatterplot of mean ΔK and pterygium extension. Mean ΔK: postoperative mean corneal refractive power minus preoperative mean corneal refractive power. Pterygium extension: distance between the nasal limbus and the point of pterygium farthest away from the limbus.

Reference

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