A New Approach to Laser Capsulotomy

Creation of consistently sized, centrally located, circular capsulotomies has long been the goal of the cataract surgeon. It has been believed that such capsular openings minimize changes in effective lens position after cataract surgery. Manual techniques, even in the best hands and utilizing mechanical or optical devices, are unable to guarantee this. The advent of the femtosecond laser, for the first time, made the consistent achievement of central, appropriately sized, circular capsulotomies a possibility, but this capability came at considerable initial and ongoing costs. Development of the CapsuLaser technology (CapsuLaser) was inspired by the challenge of creating a cost-effective laser capsulotomy device. Lasers have the ability to deliver energy to selected, pigmented target tissue in certain ophthalmic applications. The main challenge of using a laser for capsulotomy is that the anterior capsule is transparent, so there is no naturally occurring chromophore that the laser can selectively target. Historically, two methods have been used to create capsulotomies with a laser, and both rely upon plasma formation. First, Nd:YAG lasers have been used for decades to create posterior capsulotomies to address posterior capsular opacification. This is accomplished by focusing nanosecond bursts of laser energy in the vitreous humor, causing a plasma-induced vapor bubble that collapses to form a mechanical-acoustic wave. This wave applies shear stress to the posterior capsule, creating an opening. Second, more recently, in femtosecond laser-assisted capsulotomy, a high-peak–powered laser pulse is focused on a small volume to cause direct plasma-induced ablation of capsular tissue.1 A sequence of several hundred thousand ablation pulses creates two to five circles at different depths, essentially micromachining the capsulotomy. To focus the femtosecond laser in the region of the capsule, a diagnostic tool is needed to locate the capsule; therefore, femtosecond laser cataract systems are a combination of a diagnostic component and a scanning laser device. This is what leads to the relatively high cost of acquisition and operation of these systems.