Refractive Change Study Following Pars Plana Vitrectomy

1. Po-Chen Tseng¹
2. Hsin-Kai Chou²
3. Ching-Yao Tsai¹
4. Lin-Chung Woung¹

¹Taipei City Hospital, Taipei, Taiwan
²National Chung Cheng University, Chiayi, Taiwan

Purpose: The objectives of this study is to assess the occurrence and magnitude of refractive change in both phakic and pseudophakic eyes undergoing pars plana vitrectomy surgery and to investigate possible etiological factors.

Methods: Retrospective case note review of 172 eyes undergoing pars plana vitrectomy surgery for a variety of vitreo-retinal conditions. Spherical Equivalence was measured before and after vitrectomy surgery in 80 eyes. Then, the independent t-test and ANOVA was conducted to analyze the significant difference of the refractive change under variety of etiological factors.

Results: 48 Phakic eyes, whose mean change of Spherical Equivalent is -1.70 D (standard deviation of refractive change 3.14) (p < 0.05), experienced a myopic shift. This difference may result from the natural tendency by post-operative cataract formation itself. In addition, 28 Pseudophakic eyes, whose mean change of Spherical Equivalent is -0.62 D (standard deviation of refractive change 4.60) (p < 0.05) , also experienced a light myopic shift. This difference may result from the pre-operative vitreo-retinal conditions and the tamponade use in vitrectomy surgery.

Conclusions: Significant refractive changes were observed in patients underwent pars plana vitrectomy. The mean refractive change was a myopic shift in both phakic and pseudophkic patients but the range was large. The result is consistent with other reference and the etiology of the refractive change is still uncertain.