Postoperative Refractive Error by Using A-scan in Cataract Surgery After Vitrectomy

Seungbum Kang; Sung Kun Chung

doi:10.3341/jkos.2009.50.7.1022

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Kang and Chung: Postoperative Refractive Error by Using A-scan in Cataract Surgery After Vitrectomy

Original Article

J Korean Ophthalmol Soc 2009;50(7):1022-1026.

Published online: 7 September 2009

DOI: https://doi.org/10.3341/jkos.2009.50.7.1022

Postoperative Refractive Error by Using A-scan in Cataract Surgery After Vitrectomy

Seungbum Kang, MD, Sung Kun Chung, MD

Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea

Address reprint requests to Sung Kun Chung, MD Department of Ophthalmology, St. Mary's Hospital, College of Medicine, The Catholic University of Korea #62 Yeouido-dong, Yeongdeungpo-gu, Seoul 150-713, Korea Tel: 82-2-3779-1243, Fax: 82-2-761-6869, E-mail: eyedoc@catholic.ac.kr

Received 23 April 2008 Accepted 28 April 2009

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To investigate the difference between target refraction and actual refraction of intraocular lens implantation when cataract surgery was performed after vitrectomy.

Methods

This study evaluated 28 eyes of 28 patients who had undergone vitrectomy without gas tamponade and 25 eyes of 25 patients who had undergone vitrectomy with gas tamponade. A-scans were performed before the respective cataract and vitrectomy surgeries. Three months after cataract surgery, the actual refraction was measured. To compare the difference between the actual and the target refraction calculated by each A-scan, the refractive prediction error was calculated. It is determined by subtracting the target refraction from the actual refraction.

Results

In 28 eyes, the mean refractive prediction error calculated by the A-scan performed before vitrectomy was −0.146± 0.901D (diopter, D), and the mean refractive prediction error calculated by an A-scan performed just prior to cataract surgery was −0.228±1.011D. The two values were not statistically significant (p=0.653). In 25 eyes, the mean refractive prediction errors calculated by A-scans performed before vitrectomy and cataract surgery were −0.171±1.079D, and −0.227±0.798D, respectively. There was no statistically significant difference between the two values (p=0.563).

Conclusions

When a cataract surgery was performed after vitrectomy, a precise target refraction could be obtained.

Keywords: A-scan, Cataract surgery, Refraction, Refractive prediction error, Vitrectomy

References

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Table 1.

The demographic data

Type of surgery	No. of eyes	Mean age (years)	Interval between vitrectomy and cataract surgery (months)
Vitrectomy	28	58.1±10.9	13.1±11.7
Vitrectomy and intraocular gas injection	25	55.8±9.7	10.7±8.9

Table 2.

Preoperative target diopters and postoperative refractive diopters at 3 months in both groups

Type of surgery	Mean target diopters A^*	Mean target diopters B^†	Postoperative refractive diopters (S.E.^‡)
Vitrectomy	−0.165±0.942	−0.084±0.941	−0.312±1.058
Vitrectomy and intraocular gas injection	−0.164±0.938	−0.108±0.772	−0.336±0.836

^* A=mean target diopters calculated by A-scan obtained before vitrectomy

^† B=mean target diopters calculated by A-scan obtained before cataract surgery

^‡ S.E.=spherical equivalent.

Table 3.

Mean refractive prediction errors in both groups

Type of surgery	Mean refractive prediction error A^* (diopter)	Mean refractive prediction error B^† (diopter)	p-value^‡
Vitrectomy	−0.146±0.901	−0.228±1.011	0.653
Vitrectomy and intraocular gas injection	−0.171±1.079	−0.227±0.798	0.563

^* A=postoperative refractive diopter at 3 months-target diopter calculated by A-scan obtained before vitrectomy

^† B= postoperative refractive diopter at 3 months-target diopter calculated by A-scan obtained before cataract surgery

^‡ p-value=the significance of the difference was assessed by paired t-test.

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