Effect of femtosecond laser-assisted cataract surgery on the corneal endothelium: long-term corneal outcomes in a prospective comparative cohort study

Session Details

Session Title: Interactive Poster Session 01: Refractive

Session Date/Time: Saturday 13/09/2014 | 14:00-15:00

Paper Time: 14:00

Venue: Interactive Poster Terminal (Poster Village)

First Author: : B.Vote AUSTRALIA

Co Author(s): :    S. Ewe   N. Kerr   A. Howie   M. Mustaffa Kamal   P. Allen   R. Abell

Abstract Details

Purpose:

To investigate the effect of Catalys Precision Laser (Optimedica, CA) femtosecond laser-assisted cataract surgery (LCS) on corneal edema and endothelial cell loss compared to conventional phacoemulsification cataract surgery (PCS). Corneal edema is one of the most common early post-operative complications following phacoemulsification and may delay rapid visual rehabilitation. One of the major risk factors for the development of post-operative corneal edema is total ultrasound time. Recent studies have shown that femtosecond laser-assisted cataract surgery significantly reduces, and in many cases eliminates, the need for phacoemulsification energy. Reducing the amount of ultrasound energy delivered into the anterior chamber may minimize bio-mechanical damage to the cornea and result in lower rates of corneal edema and endothelial cell loss. However, few studies have examined the effect of femtosecond laser-assisted cataract surgery on the cornea, in particular comparative cohort studies with at least 6 months follow-up, as most published studies reflect short-term follow-up only.

Setting:

Ambulatory Day Surgery Operating Theatre

Methods:

Prospective, single centre, interventional, masked investigator, non-randomized comparative cohort study performed between June 2012 and December 2013. Patients with visually significant cataract were eligible for inclusion. Exclusion criteria for LCS included age < 22 years, pupil diameter less than 5 mm, and significant corneal scarring. General exclusion criteria for this corneal outcomes study included patients with pre-existing low endothelial cell counts (<1800) or clinically detectable endothelial decompensation, Fuch’s endothelial dystrophy, uncontrolled glaucoma, previous intraocular inflammation or trauma, previous viral or syphilitic keratitis and previous ocular surgery, including corneal and refractive surgery. 620 eyes from 490 patients underwent either phacoemulsification after LCS (n=405) or conventional manual phacoemulsification alone (n=215). LCS cases between May and December 2012 were performed without corneal incisions (capsulotomy and lens fragmentation only). From December 2012, LCS cases comprised of corneal incisions (2.7mm main wound and two 1.5mm sideport incisions) as well as capsulotomy and lens fragmentation. Power and energy settings were consistent throughout. Central corneal thickness (CCT), central 3-mm corneal volume, volume stress index (VSI), and central endothelial cell density were measured pre- and post-operatively at day 1, 3 weeks and 6 months using Scheimpflug imaging and non-contact specular microscopy.

Results:

620 eyes from 490 patients were included, with no statistically significant difference in both baseline corneal or surgical parameters. Post-operative corneal edema (increased central corneal volume) was significantly less after LCS compared to PCS at day 1 (4.8 ± 3.2 mm3 versus 6.9 ± 3.5 mm3; P = 0.01) and week 3 (4.6 ± 3.4 mm3 versus 6.1 ± 2.9 mm3; P = 0.001). However, this difference was not appreciable at 6 months (0.58 ± 2.5 mm3 vs. 0.34 ± 2.1 mm3). Volume stress index was no different between the groups. LCS demonstrated a significant reduction in endothelial cell loss compared to PCS at week 3 (-103 ± 208 cells/mm2 versus -138 ± 189 cells/mm2; P = 0.04), but this difference was not present at 6 months (-149 ± 233 cells/mm2 versus -150 ± 244 cells/mm2). In the LCS group, eyes treated with automated corneal incisions had greater endothelial cell loss at 6 months than both PCS and LCS performed with manual corneal incisions (P < 0.0001). Eyes in the LCS group with zero effective phacoemulsification time and manually created corneal incisions had statistically significant reduced endothelial cell loss at 6 months compared to all groups (P < 0.0001).

Conclusions:

In this prospective comparative cohort study, we investigated the effect of femtosecond laser pretreatment (LCS) on postoperative corneal edema and endothelial cell loss. LCS was associated with a significant reduction in early post-operative corneal edema and endothelial cell loss when compared to PCS. However, these differences were absent by 6 months follow-up. The rate of endothelial cell loss in our phacoemulsification (PCS) group is consistent with previous studies. The most significant factor for endothelial cell damage is phacoemulsification time, which in this study was an 81% reduction in effective phacoemulsification time after femtosecond laser pretreatment. It is probable that the reduction in early postoperative corneal edema and endothelial cell loss with LCS in the present study relates to a reduction in effective phacoemulsification time. We found endothelial cell loss was least in those patients where zero EPT was achieved after LCS without automated incisions. Laser performed automated corneal incisions however seem to adversely affect corneal endothelial cells, such that any potential benefits of femtosecond laser from reduced effective phacoemulsification time are diminished unless manual incisions are performed. Our study showed no significant difference in VSI between LCS and PCS groups. It remains to be established whether LCS provides any clinically significant benefit over current PCS techniques (given corneal decompensation after standard PCS is already uncommon ~1/2000). The implications of this study are that LCS cases may result in more rapid visual recovery in the short term for patients with limited endothelial reserve, but overall cell counts (and presumably therefore safety) remain similar with long term follow-up when compared with PCS. Randomized controlled trials comparing PCS with LCS (with and without automated corneal incisions) are required to better determine whether high-risk cases will benefit from LCS. A proven benefit for femtosecond laser pretreatment in high-risk cases remains to be established.

Financial Interest:

NONE