Original article
The Competency of Pars Plana Vitrectomy Incisions: A Comparative Histologic and Spectrophotometric Analysis

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Purpose

To compare the relative competency of pars plana vitrectomy (PPV) sclerotomies.

Design

Laboratory investigation.

Methods

PPV was performed in human cadaveric eyes using 20-gauge (20 G), 23-gauge (23 G), and 25-gauge (25 G) instrumentation. India ink was applied over a sclerotomy site while the intraocular pressure was varied. The presence of India ink particles (IIPs) along incisions was evaluated by histologic analysis. Spectrophotometric absorbance levels of vitreous aspirates were measured.

Results

PPV was performed in a control eye and two eyes, each using standard 20 G, standard 23 G, perpendicular 25 G, and beveled 25 G instrumentation incisions. IIPs were not detected in the 20 G incisions either on histology or by spectrophotometry. IIPs were detected along the entire incision length in one of two eyes with 23 G sclerotomies and confirmed by spectrophotometry. IIPs were detected along the entire incision length in one of two eyes with 25 G perpendicular sclerotomies and confirmed by spectrophotometry in both eyes. IIPs were noted partially along the length in one of the two beveled 25 G eyes, but not detected in either eye by spectrophotometry.

Conclusions

During the early postoperative period, sutureless vitrectomy incisions may allow entry of ocular surface fluid. These findings may provide a pathophysiologic mechanism for the reported increased risk of endophthalmitis in small-gauge vitrectomy surgery.

Section snippets

Tissue Preparation

Two- to four-day-postmortem human cadaveric eyes were obtained from the Florida Lions Eye Bank (Miami, Florida, USA). All globes were transported and stored in a moist chamber at 4 C prior to use. Only globes with adequate conjunctiva and the Tenon capsule without scleral thinning were included in the study. Each globe was injected near the optic nerve with balanced salt solution [BSS] (Akorn Inc, Buffalo Grove, Illinois, USA) in order to achieve an intraocular pressure (IOP) between 10 and 20

Results

A total of nine eyes were studied. PPV was performed in a control eye and two eyes each using standard 20 G, standard 23 G, perpendicular 25 G, and beveled 25 G incisions.

The sclerotomy incision was identified grossly in all eyes (Figure 3). The external lip of the 20 G incision was identified by the location of the suture. After dissection through conjunctiva and Tenon capsule, the 23 G and 25 G incisions were identified. Grossly, the external lip of the 23 G incision was a very thin scleral

Discussion

Postoperative endophthalmitis is a devastating complication of intraocular surgery. Historically, the endophthalmitis risk following 20 G PPV has been lower than cataract surgery, with recent reported rates between 0.018 and 0.04%.9, 17, 18 Recent case reports, and two cohort studies, have highlighted a possible increased endophthalmitis risk following sutureless 25 G PPV.6, 7, 8, 9, 15, 19 A similar trend has been noted with the transition to CCI in cataract surgery. Studies have suggested an

Omesh P. Gupta, MD, MBA, is currently a Heed vitreoretinal fellow at Wills Eye Institute, Philadelphia, Pennsylvania. He graduated AOA from a 5-year program with a MD with Distinction in Research and a MBA with a concentration in Health Sciences Management from the University of Rochester School of Medicine and the William E. Simon Graduate School of Business Administration. Dr Gupta was then a resident and Co-chief Resident at Wills Eye Institute. He has contributed in over 35 articles, book

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  • Cited by (0)

    Omesh P. Gupta, MD, MBA, is currently a Heed vitreoretinal fellow at Wills Eye Institute, Philadelphia, Pennsylvania. He graduated AOA from a 5-year program with a MD with Distinction in Research and a MBA with a concentration in Health Sciences Management from the University of Rochester School of Medicine and the William E. Simon Graduate School of Business Administration. Dr Gupta was then a resident and Co-chief Resident at Wills Eye Institute. He has contributed in over 35 articles, book chapters, and presentations. Dr Gupta serves on the Editorial Board of Retina Today and Evidence-Based Ophthalmology.

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