Evaluating the safety profile of femtosecond LCS

September 1, 2014

In this article, Dr Conrad-Hengerer discusses a recent study investigating the impact of femtosecond laser-assisted surgery on anterior chamber flare values and macular thickness compared with standard phaco.

Phacoemulsification alone has been shown to increase flare values in the anterior chamber as a sign of an increased permeability of the blood–aqueous barrier. With the introduction of femtosecond laser-assisted surgery (LCS) for capsulotomy and nuclear fragmentation prior to phacoemulsification there was the need to evaluate the safety profile of this technology with respect to its potential to alter blood–aqueous barrier and the development of subclinical or clinically significant macular oedema.

We, therefore, conducted a prospective randomized intraindividual comparative clinical study at the University Eye Hospital, Ruhr-University Bochum, Germany, to investigate the impact of LCS on anterior chamber flare values and macular thickness compared with standard phacoemulsification settings during an interval of six months.1

In this study, we treated 104 eyes of 104 patients by LCS and we performed phacoemulsification of the fellow 104 eyes, using pulsed ultrasound energy, which were followed by intraocular lens implantation. Laser flare photometry was taken preoperatively, and then at 2 hours, 3–4 days, 1 month, 3 months and 6 months postoperatively. Retinal thickness was measured by means of spectral domain optical coherence tomography (SD-OCT) and laser flare photometry.

Prior to the surgery, all patients were treated with topical ofloxacine 4 times daily for 3 days. According to our standard protocol, no non-steroidal anti-inflammatory drugs were applied. Baseline anterior chamber flare values were taken preoperatively with the KOWA laser flare meter (KOWA FM 600, Kowa, Tokyo, Japan) prior to dilating the pupil with topical medication. Laser flare values less than 10 photon counts per millisecond were considered normal.

Macular SD-OCT was conducted with the Topcon 3D OCT-2000 (Topcon Corporation, Tokyo, Japan). The values used for statistical analysis were central macular thickness as well as central foveal thickness, total macular volume and total foveal volume, according to the ETDRS study. The centre thickness represented the minimal centre value of the fovea, whereas the centre foveal thickness measurement was the average thickness of the foveal zone (1.0 mm diameter central circle). The total volume was determined as the volume scanned in the 6.0 mm diameter zone and the total foveal volume as the volume in the 1.0 mm diameter central circle, respectively.

LCS group

For eyes randomized into the femto LCS group, the patients' bed was unlocked and the position was turned towards the laser system (Catalys Precision Laser System, AMO, Santa Ana, California, USA). This was then followed by the positioning of the Liquid Optics Interface (LOI) on the patient's eye.

The two piece LOI, consists of a suction ring and a non-applanating immersion lens. The LOI was engaged by the surgeon and the procedure of a 5.0 mm capsulotomy and a standardized lens softening pattern (quadrant grid size) with 350 μm grid spacing were used.

This procedure was followed by phacoemulsification using the stop and chop technique with the Stellaris (Bausch + Lomb, North Bridgewater, New Jersey, USA) phacoemulsification machine.

Both groups

In both groups the phacoemulsification and aspiration was followed by polishing of the posterior capsule. Without enlarging the corneal tunnel, a heparin coated pre-loaded hydrophobic IOL (Polylens H10, Polytech, Roßdorf, Germany) was injected into the capsular bag.

After carefully removing the ophthalmic viscosurgical device all eyes were patched. Topical ofloxacin and dexamethasone (concentration 1 mg/mL), eye drops were administered 4 times daily for the first week, then the dosage gradually decreased over a period of 6 weeks.