Assessment of Zonular Integrity in Phakic Eyes Following Pars Plana Vitrectomy Using Ultrasound Biomicroscopy (UBM): A Prospective Paired Eye Comparative Study.

Purpose To assess zonular integrity in phakic patients post vitrectomy using ultrasound biomicroscopy (UBM). Study Design Prospective, comparative, non-randomized, double masked, paired eye study. Methods We used ultrasound biomicroscopy (UBM) to evaluate phakic patients with history of unilateral pars-plana vitrectomy.Inclusion criteria: 1.Phakic patients with history of pars plana vitrectomy in one eye as the only procedure. 2.Normal unoperated fellow eye. 3.Complete gas or air resolution from the vitreous cavity at the time of UBM assessment.Exclusion criteria: 1. Monocular patients. 2. History of intraoperative lenticular trauma. 3. The use of silicone oil tamponade. 4. History of trauma or pseudo-exfoliation in either eye.5. History of other ocular conditions that can affect the integrity of zonules, such as uveitis or ectopia lentis. 6. Eyes with extreme myopia/long axial length (> -8.00 D / > 30.0 mm). 7.History of intravitreal injection in either eye. 8. Age less than 18 years.Technique: A high frequency (50 MHz) UBM device was used by a masked technician to obtain radial section images from zonular bundles at 8 different clock positions. Image quality was assessed in real time, captured and saved. Two experienced masked observers (HC and CB) then assessed the quality of the images and graded the zonular findings. Only patients with adequate studies have been included. A unique grading system that was specifically devised for this study was used as the following: (0) clear, well-defined zonule(s); (1) uneven, disrupted zonules or stretched zonules; (2) extensive loss of zonules. Each clock hour was graded according to this system and the total score was then calculated for each eye. In the primary outcome, two main groups were analyzed: the vitrectomized, and healthy contralateral non-vitrectomized eyes. The mean total UBM score (TUS) from each group was compared and analyzed. Results Thirty five patients were recruited into this study. Eleven patients were males and twenty four were females. The mean age was 66.3 years. Thirty patients had vitrectomy for vitreomacular interface disorders (either macular hole or epiretinal membrane), one patient had vitreous hemorrhage and the remaining four patients had rhegmatogenous retinal detachments. With regards to tamponade agents, SF6 was used in 21 (60%) patients, air in 9 (26%) patients, and C3F8 in 5 (14%) patients. The mean UBM total score (TUS) in the vitrectomized eyes was 2.28 (SD: 1.83) versus 2.24 (SD: 1.77) in the non-vitrectomized eyes (p=0.9531. Overall, in the comparative analysis of mean scores based on two-graders’ assessments for each clock position in vitrectomized and non-vitrectomized eyes, there were no significant differences noted between the groups. Conclusion This study found no evidence for a difference in the mean total UBM score (TUS) in eyes following vitrectomy when compared to their contralateral healthy, non-vitrectomized eyes. This likely indicates that vitrectomy may not affect the integrity of zonules in phakic patients, at least for patients with vitreomacular interface disorders undergoing uncomplicated surgery.