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Eye (Lond). 2010 Feb;24(2):315-7. doi: 10.1038/eye.2009.81. Epub 2009 Apr 24.

A comparison of induced astigmatism in 20- vs 25-gauge vitrectomy procedures.

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Department of Vitreoretinal Surgery, Vision Retinal Institute, Queensland, Australia.



Surgically induced astigmatism is an unwanted variable that can lead to poorer visual and refractive outcomes in patients undergoing vitrectomy even when a technically precise procedure has been performed. This study assesses the difference in surgically induced astigmatism (SIA) between the traditional 20-gauge vitrectomy and the newer 25-gauge sutureless technique by comparing pre- and post-procedure keratometry readings.


The study is a retrospective consecutive case series of vitrectomies performed by a single surgeon. There were a total of 47 patients, eight with bilateral procedures, 24 who underwent the 20 gauge, and 31 who had the 25-gauge procedure. Patients were excluded for corneal altering pathology or scleral buckling procedures. Vector analysis of pre- and post-vitrectomy readings was performed using Alpin's method, facilitated by the ASSORT program version 4.1.


Mean time at which post-operative keratometry readings were taken was 3.9 months (1-36). Mean astigmatism at presentation was 0.63 D and 0.92 D and at post-surgically follow-up 1.14 D and 0.91 D (20 and 25 gauge, respectively). Mean SIA was 0.66 D (SD=0.8 D) for the 20-gauge group and 0.27 D (SD=0.23 D) for the 25 gauge (P=0.037). The calculated figure of SIA variability representing the 95% CI for the maximum amount of SIA for each procedure was 2.26 D and 0.73 D for the 20- and 25-gauge procedure, respectively.


The study shows that the 25-gauge technique involves a statistically significant reduction in the amount of SIA. This can ultimately lead to a better visual and refractive outcome for the patient.

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