Filtration Surgery (Trabeculectomy)

Filtration surgery, also called trabeculectomy, is a treatment for several types of glaucoma including open-angle and narrow-angle glaucoma. It is often performed on patients who have not responded well to medication or laser treatment such as ALT or SLT. Filtration surgery usually provides a dramatic reduction in pressure within the eye.

In recent years, landmark studies on glaucoma patients are slowly changing our knowledge about preventing visual damage from glaucoma.  One concept emerging from such studies is assigning each individual eye a "target pressure" based upon the severity of the current glaucoma, in terms of the current pressure readings and the current amount of optic nerve and/or peripheral vision damage.  We have recognized that while some mild glaucomatous eyes can tolerate long term pressures of "18", eyes with more advanced glaucoma damage may need constant long term pressures at or below 12 in order to prevent further vision loss or blindness.

Another concept is that we have to be more aggressive in treating glaucoma, and that earlier intervention with laser and/or surgical procedures not only appears to be more protective against vision loss, but that these procedures may also actually work better when performed earlier rather than later.

An additional but unspoken concept that we all really know, but no one ever talks about is that many glaucoma patients just do not take their medications faithfully, day in and day out, for their entire lives, which is exactly what would be required in order to prevent visual damage from glaucoma.  Much like high blood pressure, Glaucoma is a silent disease that typically doesn't have even the first symptom--you and your eye feel the same, and your eyes "apparently" see the same whether the drops are used or not.  And when a lack of taking medications "seems" to be met with no ill effects, patients often just cheat, a little or a lot.  The eye pressure must be maintained at or below the target level 24 hours a day in order to prevent gradual, progressive glaucoma damage.  So deleting even one drop from a 3 times a day regimen allows the pressure to increase above the target level for that 8 hour period.   Over months and years, this will gradually and progressively cause permanent death of optic nerve fibers.  That damage is translated into gradual loss of peripheral vision, little by little, until in advanced stages there is only tunnel vision left.  Then, the next step is loss of straight ahead vision or even blindness.  But since this vision is the LAST to go, patients fool themselves into believing that they are getting away with cheating. 

For these reasons, filtration surgery is being performed both more frequently as well as earlier in the course of glaucoma, rather than only as a last ditch effort in patients who have already suffered severe damage to their vision.  Since surgery is virtually the only method that will lower pressures to targets of 12 or below, it is obviously indicated in patients who have been assigned such a low target.  In addition, since filtration surgery frequently eliminates some or even all glaucoma medications, some patients elect to have surgery because they can no longer tolerate their medications, whether due to side effects, budgetary constraints, or physical or mental disabilities such as crippling arthritis or Alzheimers that prevent them from administering eyedrops properly. 

A small channel, or 'bleb' is created to allow fluid to drain from the eye. (See animation below.)

Filtration surgery is for those:

• who have been diagnosed with glaucoma
• whose doctor has determined that filtration surgery is an appropriate treatment for their condition
• who have advanced optic nerve damage and/or significant peripheral vision loss
• who can no longer tolerate their medications due to side effects
• who will not or cannot be absolutely faithful in taking their medications, whether due to medication costs, forgetfulness, phsical disabilities, or mental disabilities
• whose pressures are not controlled at or below target on maximal tolerated medication
• whose pressures remain uncontrolled after ALT

What to expect on surgery day:

You will arrive at the surgery center 30-60 minutes prior to your procedure. Once you have been checked-in and settled comfortably, you will be prepared for surgery. The area around your eyes will be cleaned and a sterile drape will be applied.  You wil be given a sedative to allow you to drift off into a "twilight sleep" and your eye will be numbed with topical or a local anesthesia. When your eye is completely numb, an eyelid holder will be placed between your eyelids to keep you from blinking.

Using advanced microsurgical techniques and equipment, your doctor will create a tiny new channel between the inside of your eye and the outside of your eye. In the standard filtration procedure known as "trabeculectomy" a small section of tissue will be removed, creating a channel, to allow fluid to pass through the blocked drainage network and through the white (sclera) of the eye. The incision will be closed with small stitches and covered with the thin transparent outer tissue of the eye, called the conjunctiva. Blood vessels in the conjunctiva then carry the draining fluid away.

To keep the drainage channel open, your doctor may apply an extremely small dose of a chemotherapeutic (anti-scarring) agent to the new filter. Your eye will be patched and shielded after your procedure and drops will be prescribed to alleviate any soreness or swelling inside the eye. You should go home and relax for the rest of the day. Most patients resume normal activities within a few days.

Follow-up visits are necessary to monitor your eye pressure. It may take a few weeks to see the full pressure-lowering effect of this procedure, and adjustments may need to be made to the filter during this period. These adjustments may include:

• injection of additional small amounts of chemotherapeutic agents
• loosening or removal of one or more stitches
• finger pressure to the eye to force fluid through the filter
• numbing the eye and opening the channel slightly with a fine instrument
• placing a contact lens over the eye

Realistic expectations:

The success rate for this type of surgery is approximately 80 percent in cases where no surgery has been done on the eye before. Success means that the pressure is being controlled at or below target, with or without the use of medications, while lack of success typically means only that the body's natural healing tendency has sealed  the created channel, and that pressure is not well controlled.  If this occurs, it is possible to repeat filtration surgery.  However, everyone's eyes are unique and some people do require further treatments. In more difficult cases where even filtration surgery doesn't prevent damage to the ocular nerve, it may be necessary to perform other types of procedures.

Serious complications with filtration surgery are extremely rare, but like any surgical procedure, it does have some risks. Since going to a specialist who is experienced in filtration surgery can significantly minimize the risks, it is important for you to know that both doctors Monnett and Steinwand have together performed hundreds of successful filtration surgeries, and that during Dr Monnett's 20 years of practice he has continually stayed at the cutting edge regarding the changes and major advances in technique and technology concerning filtration surgery.

If you and your doctor decide that filtration surgery is an option for you, you will be given additional information about the procedure that will allow you to make an informed decision about whether to proceed. Be sure you have all your questions answered to your satisfaction.

If you would like more information about this procedure you can make an appointment or contact the office for additional information.