Posterior capsule opacification (PCO) is common after cataract surgery. Even a perfect surgery by a master surgeon still leads to PCO in many cases. Fortunately, we have the ability to use the YAG laser to perform a posterior capsulotomy which is safe, highly effective, and takes just a minute or so. Every cataract surgeon needs to know how to perform YAG laser capsulotomy as well.
The two primary techniques are:
- Cruciate Pattern
- this involves using the YAG laser to create a cross pattern which then allows the resultant capsule flaps to retract out of the visual axis.
- Because they are still attached, this method tends to avoid the creation of free-floating capsular fragments in the vitreous.
- If needed, additional laser spots can be placed along the mid-position of these flaps to further expand the size of the central opening.
- Care must be taken to properly aim the laser to avoid pitting the optic in the central visual axis
- Circular Pattern
- this involves using the YAG laser to create a circular pattern which then allows for a round posterior capsular opening
- the circular capsular cut-out can end up free-floating in the vitreous and can create a disturbing, large floater in the patient’s vision
- if the circular opening is left intact at the bottom then the capsular flap will still be attached and will be less likely to cause a floater
- lasers shots do not need to be placed in the central optical zone using this method so the chance of central optic pitting is low
The laser settings depend on the density of the fibrous growth and vary from about 2 to 6 mJ per spot. The total number of spots also varies and it typically between 10 and 30. Acrylic IOLs tend to be a bit more resistant to pitting from the YAG shots compared to silicone IOLs. The laser off-set can be dialed in to minimize the risk of pitting.
The ideal YAG capsulotomy size is just enough to account for the pupil size, including in dark lighting situations. The posterior capsulotomy in any dimension, should never be bigger than the optic size of the IOL which is typically 6mm. This is to prevent vitreous from prolapsing around the optic and into the posterior chamber and even anterior chamber. Sometimes the capsule is elastic and a small clear zone can expand larger right as you are watching through the oculars of the laser. Always start small and then it is easy to enlarge it later in the same session or even in the future.
Side effects of YAG laser capsulotomy include a transient rise in the intra-ocular pressure (IOP) and persistent floaters in the vision. Historically there has been a correlation between YAG laser capsulotomy and retinal break/detachment in a tiny percent of patients, however this is far less common now with the lower energy levels and higher precision of modern lasers.