Ophthalmic Lasers: Settings and Videos

These settings are general recommendations. Your technique, laser devices, practice patterns or patient population may require different settings.

YAG Capsulotomy (Nd:YAG laser)

The posterior capsule is left in place during cataract surgery to hold the lens. However, this capsule can beginto opacify in the weeks to months after surgery, leading to a progressive decrease in vision. Fortunately, the removal of the posterior capsule is safe and painless.

Posterior capsulotomy is performed with a frequency doubled pulsed (Q-switched) Nd:YAG laser. At the focal point of the Nd:YAG beams, plasma is created which creates an opening in the posterior capsule via photodisruption. A posterior offset for the laser focus is often used to prevent nicking the IOL as the plasma jet tends to travel anteriorly.

A contact capsulotomy lens can help keep the eye more stable, give a small amount of magnification, improve convergence of the beams and defocus the light more at the level of the retina. The two most common techniques are cruciate and can opener.

The cruciate opening is faster, uses less energy and may create a better optical result, however the laser pulses cross the visual axis and have the chance of nicking the lens in that location. The can opener technique avoids the center in case an accidental lens pit happens, but takes more energy and time to perform.

Laser peripheral iridotomy (LPI) (Nd:YAG laser)

Laser peripheral iridotomy (LPI) has many indications, including treatment of acute angle closure glaucoma, chronic angle closure, prophylaxis in narrow angles, phacomorphic glaucoma, pigment dispersion syndrome, plateau iris, and others.

Pre-treatment with apraclonidine and pilocarpine decreases the post-procedure IOP spike and mioses the pupil. Patients can also be started on a topical steroid like prednisolone acetate to decrease inflammation.

LPI can be done with the same pulsed Nd:YAG laser as used for capsulotomy. Different opinions exist for where to place the PI including superior, temporal or inferior and there are benefits of each location. Target an iris crypt if possible. Dark and thick irises may need pre-treatment with argon or other lasers to coagulate and thin the iris. The post-procedure IOP can be checked in 30 minutes.

Selective laser trabeculoplasty (SLT)

Selective laser trabeculoplasty (SLT) can be performed for primary open angle glaucoma, pigmentary glaucoma, or pseudoexfoliative glaucoma to reduce IOP by about 2-4 points. It can be repeated, added on top of existing drop regimens, and done for patients that have received trabeculectomy.

Apraclonidine can be used to prevent a post-procedure IOP spike and pilocarpine to miose the pupil. The treatment goal is classically to see “champagne bubbles” appear. The effect usually takes 6-8 weeks for full effect and usually decreases IOP by 20-35%. The post-procedure IOP can be checked in 30 minutes.

Panretinal Photocoagulation (PRP)

Panretinal or targeted retinal photocoagulation (PRP) is an important tool for treating proliferative diabetic retinopathy, retinal vein or artery occlusions, and other diseases which cause macular ischemia. The ultimate goal of PRP in all these cases is to decrease the production of VEGF by destroying ischemic retinal tissue.

PRP can be performed with a laser indirect ophthalmoscope or more often with a pattern scanning laser (which can place a grid of 3 x 3 spots in less than 0.2 seconds!) using a contact panfunduscopic lens. Complete treatment usually means 1200-2000 shots achieving white to medium-white retinal burns up to 1-2 disc diameters from the arcades and optic nerve. Treatment can be done in one or multiple sessions. The regression of neovascularization usually takes 3-4 months for full effect.