Visual Field Loss Due to Glaucoma
Fortunately, glaucoma is usually manageable, and the key to preventing serious vision loss and blindness lies in early detection. Early glaucoma can be challenging to detect. If a significant risk of glaucoma is identified, then specific testing should be performed to get baseline information about how the eye behaves. Such testing might include photos, nerve scans, corneal thickness measurements, and formal visual field testing.
Not everyone needs the same level of eye pressure control. Some patients can safely have a higher than normal eye pressure and never develop glaucoma; such patients with a “high normal” eye pressure might be monitored as “glaucoma suspects” and may not ever need treatment.
If the eye pressure needs to be lowered, the treatment depends on the type of glaucoma present, the stage of the glaucoma and the cause of the eye pressure problem. Treatment may involve eye drop medications, laser procedures, and/or surgery to lower the eye pressure. Unfortunately, we do not yet have a way of recovering or improving the vision that glaucoma has taken away, so preventing vision loss is the real goal.
Medicated eye drops may be prescribed to lower the eye pressure. Many different types of eye drop medications are available, and they work in different ways. In some cases, more than one eye drop type may be needed. They generally need to be used on a regular and long term basis to control eye pressure, much as a pill may be used long term to lower blood pressure.
For open angle glaucoma, a laser procedure called “trabeculoplasty” may be performed to enhance the activity of the natural inner drain channels and thus lower eye pressure. Such treatments are of low risk and are quite effective in the many patients. There are several types of lasers that are approved to perform this treatment.
Laser Peripheral Iridotomy (LPI)
The treatment for angle-closure glaucoma (and narrow-angle glaucoma), is generally initiated with laser iridotomy (an opening in the colored iris) in order to move the iris away from covering and blocking the drainage channels of the eye. In some cases, short or long term eye pressure medications may also be needed. Not uncommonly, patients may have a combination of narrow and open angle glaucoma, and each patient needs a specific treatment plan.
Minimally Invasive Glaucoma Surgery (MIGS)
There are very small devices now available that can be used to help open the natural drain canal of the eye. These are surgically placed at the time of cataract surgery. The FDA has not yet approved these small devices for surgery other than when cataract surgery is done, so their use remains limited to the time of cataract surgery. The iSTENT is such a device that is FDA approved, and lowers the IOP more than cataract surgery alone. Future devices such as the Cypass and Hydrus, and others may be available in the near future.
Canaloplasty is a good procedure for patients whose medication isn’t working, but who aren’t yet ready for a more advanced procedure. This procedure lowers pressure inside the eye by widening the eye’s drainage canal, and can also help reduce dependence on long term medications. In most cases, a small encircling stent helps keep the canal open and the pressure down.
In some cases, the best way to lower the eye pressure is to create a small channel in the coating of the front of the eye so that some of the internal fluid the eye makes can escape, thus bypassing the natural drainage canal. One such procedure that has been a mainstay of glaucoma surgery is called “Trabeculectomy” or “Filtering Surgery”. Many patients who have this procedure enjoy a lower pressure with fewer medications. The post-operative care is very important to prevent the small opening from sealing closed with scar tissue, and the healing time can be a few weeks to a few months.
Tube Shunt Surgery
For certain glaucomas, and in cases where a filtering surgery has not worked, a tube shunt may be considered. There are a variety of these devices, but the general idea is that a small hollow plastic tube is inserted into the front part of the eye, and this tube leads to a reservoir that is placed outside the eye, to which the tube connects. Such devices are used in glaucoma associated with inflammation, growth of new blood vessels (neo-vascular glaucoma), and when a previous glaucoma surgery such as a filtering surgery has failed.
Other types of glaucoma surgery might include Trabectome (a device that surgically removes the internal wall of the drainage canal from an internal approach), the ExPRESS shunt (a small metal tube that can be placed through the wall of the eye at the time a filtration surgery is done), ECP “ Endo-Ciliary-Photocoagulation” (which uses a low power laser to selectively treat the tissue in the eye that makes fluid), and Cilio-Destructive processes, using cryotherapy (freezing) or laser to destroy ciliary body tissue (which manufactures internal eye fluid) from an external approach.