By Jeffrey Henderer, MD
Ken Parker, PhD

Cataract is a clouding of the eye's lens that typically occurs as part of the normal aging process. Since modern cataract surgery, in which the lens is removed and replaced with a clear plastic one, is usually quite safe and effective, deciding if and when to do so in otherwise normal eyes is usually fairly straightforward. If blurred images and glare caused by a cataract prevent a person from doing what he or she needs or likes to do, surgery is usually recommended. This could mean that a person can no longer read, drive a car, play golf or do fine needlework as well as they would like to. Other patients complain that glare from sunlight drastically reduces their activities outside. The message is that, quite often, the decision for cataract surgery is driven by the patient's symptoms as well as the doctor's interpretation of the likely success of the procedure to result in improved vision.

The choice facing a glaucoma patient in this situation is not so straightforward, depending on a particular patient's actual ocular situation:

• The amount of visual field damage and optic nerve damage
• The number of glaucoma medications a patient is taking before surgery
• Whether glaucoma surgery has already been performed in the eye
• The eye pressure before surgery
• The desired eye pressure after surgery
• Tolerance for specific glaucoma medications
  

Basically, one wants to perform the cataract surgery at a time and in a manner that is most likely to improve overall vision, taking into consideration the nature and stage of the glaucoma and the way in which it is being treated.

The decision is then influenced by the following more general considerations:

First, sometimes cataract surgery is more difficult to perform in patients with glaucoma.

• Many have small pupils that do not dilate well, making it difficult for the cataract surgeon to see inside the eye.  These small pupils may be the result of having used eye drops such as pilocarpine for a long time, laser procedures, or some type of inflammation.
• Some glaucomas may be associated with what is known as the exfoliation syndrome.  This means their glaucoma has been caused by deposits of flaky material in the front of the eye that clog up the drain of the eyes, causing the pressure inside the eye to rise and damage the optic nerve cells.  These same flakes can weaken the "strings" that hold the lens in place, making the lens "wobbly" during surgery.
• Just because cataract extraction can be more difficult in the glaucoma patient, both patient and doctor may wait as long as possible before removing the lens, and such lenses with far-advanced cataract maybe more difficult to remove.

Second, cataract surgery can cause problems in some glaucoma patients.

For example, continuing some glaucoma medications, mainly pilocarpine, Propine and Xalatan after cataract surgery, may cause problems.

Third, in patients who have undergone glaucoma surgery, subsequent cataract surgery may induce inflammation that causes the glaucoma surgery to lose its effectiveness or even fail. 

Fourth, glaucoma surgery can make a cataract worse.

Fifth, cataract surgery may decrease eye pressure.

Understanding the patient's individual ocular situation together with these general principles can help the patient and doctor decide what is most likely to produce the best visual result: (1) performing cataract surgery alone, (2) performing glaucoma surgery alone, (3) performing a combined cataract extraction and glaucoma surgery.

If a cataract is causing a person more problems than glaucoma, cataract surgery alone may be recommended in the hopes that the pressure can be well controlled with the same medications that were being used before surgery.  Or, as noted above, the cataract surgery itself may lower the pressure.  But if, again as noted above, pilocarpine, Propine or Xalatan are being used, they may cause problems if they are continued after surgery, and glaucoma surgery may need to be performed following cataract extraction.

If glaucoma is causing the person more problems than cataract, glaucoma surgery alone may be recommended.  But as noted above, in some patients glaucoma surgery may make the cataract worse, hastening the need for cataract surgery.  And, as also noted above, cataract extraction is more difficult to perform in patients who have undergone glaucoma surgery and may reduce the effectiveness of that surgery, requiring a return to medications to lower the eye pressure. 

In some patients, performing a cataract extraction at the same time as glaucoma surgery may be best.

Possible Benefits:

• One surgery may succeed in both clearing up central vision loss from cataract and in controlling peripheral vision loss from glaucoma by lowering the eye pressure.
• The problem of possibly worsening cataract following glaucoma surgery alone is eliminated.
• Eye pressure control is usually better after a combined procedure than after cataract surgery alone.  In fact patients can often reduce or even eliminate the need for glaucoma medications after combined surgery just as after standard glaucoma surgery.
• A combined procedure can be especially beneficial for patients with glaucoma uncontrolled on medications who have a significant cataract.
• Also, for those with glaucoma well controlled on medications, it may offer the chance to reduce the need for medications or prevent anticipated pressure problems after the surgery.

Risks

• Usual risks of glaucoma surgery: leaking or infected blebs
• Low eye pressure
• Bleeding
• Swelling of the retina and choroid
• Somewhat longer and more complicated surgery

Summary

The management of cataract in the glaucoma patient can be very tricky.  Cataract surgery performed alone, or in combination with glaucoma surgery, can offer substantial benefits to patients, but it also carries substantial risks.  The choice very much depends on the individual patient's situation.