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M. Neudorfer, N. Oren, L. Berkner, M. Goldstein, A. Barak; High Frequency Ultrasound for Comparing Anterior Segment Morphometric Values Before and After Pars Plana Vitrectomy. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5998.
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Pars plana vitrectomy is the second most common intraocular operation. In the end of many vitrectomies gas or silicone oil are injected into the vitreous cavity for internal tamponade. It is presumed that the use of vitreous substitute at the end of surgery can cause changes in the anterior chamber depth (ACD). Ultrasound biomicroscopy (UBM) has demonstrated anterior segment changes that can be associated with postoperative complications. Quantitative assessments of changes in the (ACD) and lens width (LW) following vitrectomy have not been reported before. The aim of our study was to evaluate post-vitrectomy changes in the ACD and LW by means of high-frequency ultrasonography (HFU) in gas-filled eyes and non gas-filled eyes.
Phakic and pseudophakic eyes of patients who underwent vitrectomy were prospectively studied. No eyes had undergone any previous surgical procedure involving the posterior segment. An HFU (20 MHz transducer, I3 - Innovative Imaging Inc.) study of the anterior segment, including ACD and LW measurements, was performed on each eye. The preoperative examination took place 1-3 days before the surgical procedure and the postoperative one took place 1-3 days after it. The paired Wilcoxon non-parametric test was used for statistical analysis.
In the tamponaded eyes group (n=18) the mean preoperative ACD was 3.15±0.97mm and the postoperative ACD was 2.53±0.83mm. In the non-tamponaded eyes group (n=12) the mean preoperative ACD was 3.28±0.81mm and the postoperative ACD was 3.22±0.86mm. The mean decline in ACD was 0.62±0.44mm (19.51%±9.81%) in the tamponaded eyes group and 0.06±0.16mm (2.13%±5.63%) in the non-tamponaded eyes group. There was a statistically significant difference (p<0.001) between the tamponaded eyes group and the non-tamponaded eyes group. The mean decline in ACD was 13.1%±10.2% in the phakic eyes group (n=19) and 11%±14.8% in the pseudophakic eyes group (n=11). The decline was statistically significant in both the phakic and the pseudophakic groups (p<0.0001 and p=0.022, respectively). The difference between the preoperative and postoperative LW values in the phakic group was not significant.
Vitrectomy with gas injection reduced ACD values as measured by HFU shortly after the procedure in both the phakic and pseudophakic groups. No significant changes were seen in vitrectomized eyes in which no gas was injected. These results may be important in understanding the mechanism which causes early intraocular pressure elevations after vitrectomy in gas-filled eyes.
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