Assessment of Anterior Segment Changes in Pseudophakic Eyes, Using Ultrasonic Biomicroscopic Imaging, after Pars Plana Vitrectomy with Silicone Oil or Gas Tamponade

Comparison of postoperative anterior segment changes associated with pars plana vitrectomy with and without vitreous base shaving

AIM

To compare changes in anterior segment topography and axial length (AL) evaluated with Pentacam and IOL Master after pars plana vitrectomy (PPV) performed with and without vitreous base shaving.

METHODS

This prospective study included patients who underwent PPV or phacoemulsification+PPV (Phaco+PPV) for various indications. Patients who underwent total posterior hyaloid detachment and excessive vitreous base shaving with scleral indentation were referred to as complete PPV (c-PPV). The patients whom posterior hyaloid was separated as far as the posterior arcades and vitreous base shaving with scleral depression was not performed were classified as the partial PPV (p-PPV) group. All patients underwent detailed ophthalmologic examinations preoperatively and 1wk, 1, and 3mo postoperatively. Changes in the anterior chamber depth (ACD), anterior chamber volume (ACV), iridocorneal angle (ICA), central corneal thickness (CCT), and keratometric measurements (K₁ and K₂) were evaluated with Pentacam HR. Changes in the AL measurements were analyzed with IOL Master.

RESULTS

A significant increase in ACD was observed in c-PPV cases (P=0.02), but this increase was not significant in the p-PPV group (P=0.053). In contrast, ICA increased significantly in the c-PPV group (P=0.02) but decreased in the p-PPV group (P=0.09). BCVA was significantly improved in the c-PPV group from week 1 (P<0.001) while the increase in the p-PPV group reached significance at 3mo (P=0.035). CCT increased in the first week and later returned to baseline in both groups. No significant differences in the other parameters were observed between the groups, and there were no significant changes in intraocular pressure, ACV, AL, K₁ or K₂ values (P>0.05 for all).

CONCLUSION

Incomplete posterior hyaloid excision and not removing the vitreous base in PPV surgeries may create a more stable anterior chamber, thus preventing the downward movement of the lens-iris diaphragm, and may cause ciliary body retraction, thereby reducing ICA. Awareness of these effects can provide some amount of guidance to physicians in selecting the appropriate PPV procedure and preempting surgical complications.

Changes in the anterior segment of the eye following uncomplicated pars plana vitrectomy. A review

Pars plana vitrectomy is currently the most common technique used in retinal surgery. Although primarily involving the posterior segment of the eye it also affects the anterior segment. As this is a less published topic, the aim of this paper was to review the literature on changes in the anterior segment after uncomplicated pars plana vitrectomy using data based literature search. The conclusions are that even in otherwise ophthalmologically healthy patients, complications may occur in the anterior segment. Surgeons need to pay utmost attention in glaucoma patients and in those with endothelial insufficiency who are at highest risk of complications. He/she must also correctly plan a potential cataract surgery if not already done earlier. From the literature, most of the changes in the anterior segment after uncomplicated PPV are found to be temporary.

Myopic shift in a pseudophakic eye with an accommodating IOL following vitrectomy with gas tamponade

Purpose

To report the case of a patient with Crystalens, an accommodating posterior-chamber intraocular lens (IOL), who experienced a myopic shift following subsequent vitrectomy with gas tamponade. We propose a hypothesis as to why this myopic shift occurred and analyze its validity based on current literature.

Observations

A patient had cataract surgery with implantation of a Crystalens AT-50AO +21D. Preoperative A-scan measured anterior chamber depth (ACD) to be 3.69 mm. The refraction was emmetropic following cataract surgery. Nine months later, the patient required pars plana vitrectomy with gas tamponade for a rhegmatogenous retinal detachment, followed by vitrectomy, membrane peel, and air/fluid exchange for epiretinal membrane. The retinal repair was anatomically successful, however, the patient experienced a −1.0 D myopic shift. ACD measurement following vitrectomy was 5.08 mm.

Conclusions and importance

Myopic shift following vitrectomy with gas tamponade in pseudophakic eyes is widely reported. This patient's myopic shift was assumed due to anterior movement of the Crystalens caused by a gas bubble placed during retinal detachment repair as this is the prevailing theory in the literature [1]. However, a comparison of the patient's ACD measurements does not support the above hypothesis. Further study is needed to determine the mechanism of myopic shift seen in pseudophakic patients following vitrectomy, specifically those with gas.