Learn why vitrectomy may impact eye pressure, so that you can talk with your eye doctor about the risks and benefits of this surgery.
What is Vitrectomy?
Vitrectomy is a commonly performed surgery by retinal specialists in which the vitreous humor (or vitreous jelly), is removed from the eye. The vitreous humor is the substance that fills in the region from the lens to the back of the eye.
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Why is Vitrectomy Performed?
Vitrectomy is often combined with other retinal surgeries. The eye conditions for which vitrectomy might be performed include retinal detachment repair, complications from diabetic retinopathy, removal of membranes (epiretinal membrane stripping for the treatment of macular pucker), macular holes, and removal of vitreous blood.
Vitrectomy: Short-Term Eye Pressure Changes
Because of the wide variety of reasons vitrectomy is performed, and the fact that it involves different steps, it is challenging to say for sure whether a given patient will develop glaucoma or elevated eye pressure after vitrectomy. However, short-term elevated eye pressure is a common occurrence and known risk after vitrectomy surgery, ranging from 20 percent to 60 percent of cases. The elevated eye pressure is usually temporary and can be treated with eye pressure-lowering eye drops. If your optic nerve is healthy, there is often no long-term consequence of this short period of eye pressure elevation. Of course, if you already have preexisting glaucoma, the concern for eye pressure elevation is higher. Your retina surgeon can take your preexisting glaucoma into account when considering the surgical approach, although it will not be possible to absolutely eliminate the risk of elevated eye pressure after vitrectomy.
Vitrectomy: Long-Term Eye Pressure Changes
Whether vitrectomy causes long-term eye pressure elevation and/or glaucoma is more debatable. There have been both older and more recent studies examining this question of elevated eye pressure and/or glaucoma after vitrectomy surgery.
In a study in which patients with vitrectomy were followed for an average of almost five years, Dr. Stanley Chang found that there was an increased risk of open-angle glaucoma after vitrectomy. Patients who also had prior cataract surgery were potentially at higher risk. In those patients who already had known glaucoma at the time of vitrectomy surgery, the number of eye pressure-lowering drops increased after vitrectomy.
A more recent study by Dr. Arthur Sit and colleagues examined the risk of open-angle glaucoma after vitrectomy and found that the risk of primary open-angle glaucoma after vitrectomy is increased. The 10-year probability of developing glaucoma after vitrectomy was approximately 10 percent. In a study called PROVE (Prospective Retinal and Optic Nerve Vitrectomy Evaluation), it was found that one year after vitrectomy the inferior retinal nerve-fiber layer-thickness decreased, which is a sign of damage to the optic nerve. In addition, patients who had prior cataract surgery had increased eye pressure in the eye that underwent vitrectomy.
Why Might Vitrectomy Increase Eye Pressure?
What are the mechanisms by which vitrectomy could be causing elevated eye pressure or glaucoma? First of all, it is important to recognize that the likelihood of developing elevated eye pressure may depend on the complexity of the surgery, underlying health of the eye, and the reasons for vitrectomy.
Gas and silicone oil are often injected into the eye to help repair retinal tears, for example. The gas expands in order to fill the eye and keep the retinal break closed, and this can temporarily cause elevated eye pressure. Silicone oil is another agent that is often injected to help repair retinal tears, and in this case, the silicone oil can come forward into the front of the eye and cause blockages of the drainage system, resulting in elevated eye pressure. Silicone oil can be removed, and the gas eventually dissolves, so both of these situations are in some way considered temporary.
Additional risk factors for elevated eye pressure after vitrectomy include the use of laser (also used to treat retinal breaks), which can sometimes cause a part of the eye called the ciliary body to swell. If there is a lot of inflammation after the surgery, this can sometimes cause temporarily elevated eye pressure. Ironically, abundant steroids are used to treat inflammation, and the steroids themselves can cause the eye pressure to rise.
Finally, it is important to note that sometimes glaucoma surgeons call upon their retina colleagues to do a vitrectomy when a glaucoma drainage device (or tube shunt) is implanted. For example, in some patients with corneal transplants, we might prefer not to have the tube in the front of the eye, where it can affect the cornea. Instead, we might choose to place the tube in the back of the eye, in which case the vitreous humor must be removed so that it does not clog the tube.
As with all surgeries, it is important to discuss with your ophthalmic surgeon the risks, benefits, and alternatives to the surgery, and have all of your questions answered before you proceed.