Limiting IOP rise in laser cataract procedures

As cataract surgery patients are typically much older than those undergoing LASIK, they face a higher risk of an intraoperative or postoperative IOP spike. A number of cataract patients will also have comorbid vascular disease, ocular hypertension or glaucoma (in some populations, 25% of patients have pre-existing glaucoma),¹ and cataract surgery must be performed in a way that lessens the likelihood of a further damaging pressure increase.

Reports suggest that traditional laser system patient interfaces may increase the risk for several serious complications, including retinal detachment, optic neuropathy, macular holes and foveal haemorrhage.

A femtosecond laser system with a novel fluid-filled interface (Catalys Precision Laser System, OptiMedica, Sunnyvale, California, USA) has been designed to prevent corneal deformation and the corresponding increase in IOP. The configuration of this system, in which no pressure is applied directly to the cornea, should keep any IOP increase to a minimal level. The suction ring contacts only the sclera and, unlike hard-curved interfaces, the liquid interface does not create folds in the posterior of the cornea.

We recently conducted an in vivo study² at Center for Vision Science, Ruhr University Eye Clinic, Bochum, Germany, which confirmed that Catalys system's fluid-filled Liquid Optics interface produced only a slight increase in intraoperative IOP. The result of this prospective clinical trial of 100 eyes of patients with a mean age of 70 ± 12 years showed that mean IOP increased during laser cataract surgery with the use of the suction ring and again during the actual femtosecond laser treatment but returned to pretreatment levels 1 hour postoperatively.

The study, which we believe was the first to analyse IOP variations in vivo during femtosecond laser-assisted cataract surgery, measured pretreatment and post-treatment IOP levels with a Goldmann tonometer, while all others (before suction, with suction, after femto with suction, and after femto without suction) were performed using a modified Schiotz tonometer. The preoperative measurements taken with the two devices agreed well.