The retina is a Saran Wrap thin membrane that is suctioned up against the inside back two-thirds of the eyeball. It acts like the film in a camera, capturing the "picture" that will be sent to the brain. The macula is the central portion of the retina that lies in the back part of the eye near the optic nerve, the cable that sends messages back to the brain. The macula is responsible for sharp central vision. It is used for reading, watching television, and driving, among other visual tasks.
In some eyes the vitreous, the jelly filling the back part of the eye, pulls in an abnormal fashion on the macula and eventually makes a defect in it called a "macular hole". A macular hole often develops over several months. The patient often first notices only distortion of what should be straight lines in the center of the vision of that eye. (This can also be a symptom of other macular diseases.) After a period of distortion a small blank spot appears in the absolute center of vision and enlarges over the next month or so. Ultimately the defect in the retina is approximately one-half millimeter (about 1/50 of an inch) and is sufficient to blot out a word in newsprint at which the patient looks directly with that eye. Vision around the central absolute blank spot is also disturbed because fluid from the vitreous cavity goes through the hole and collects under the retina at its edges. At this point the vision is typically 20/200, the level required for "legal blindness" to be declared for an eye. Once a macular hole has reached this stage the vision typically remains at this level with no further worsening.
Until a short time ago when a patient developed a macular hole he or she was told that nothing could be done and the vision most likely would remain at a level of 20/200 for life. In the late 1980's, two doctors working in Sacramento, California developed a surgery based on existing techniques to seal off a macular hole and improve vision. They reasoned that if the fluid that had accumulated under the edges of the hole could be removed and that portion of the retina flattened that they might regain some visual function even if the central defect remained. They discovered when they were successful in flattening the macular hole, not only did the vision from the surrounding retina improve, but the central defect itself greatly diminished in size. Once the fluid in the hole is removed and the rim of the hole is allowed to pull back toward its center, the central visual defect become much smaller. With current techniques, we are able to close about 90 percent of macular holes. Most of these experience a substantial improvement in vision. Many eyes achieve vision of 20/60 to 20/80 from the original 20/200. A few have a visual return to nearly 20/20. Usually patients describe a persistent but much smaller central defect and relief of distortion. The closure rates and visual results are best if the operation is performed within about six months of the onset of symptoms. At the other extreme, macular holes that have been present for over two years close at a much reduced rate and visual improvement, if obtained at all, is much more modest.
Sometimes an 'impending' macular hole is diagnosed before a full thickness retinal defect develops. Since about 50 of these eyes will spontaneously heal the problem without developing a macular hole, observation rather than surgery is recommended in those cases.
The procedure is done under local anesthetic as an outpatient in much the same way modern cataract surgery is performed. After the placement of the local anesthetic the patient is positioned under a large microscope. Three tiny wounds are made in the front, white part of the eye. Instruments are introduced with which the vitreous jelly is removed. Often there is a very subtle, but important layer of vitreous material still lying on the macula which is removed by special techniques. The fluid in the vitreous cavity is then replaced with air and the fluid in the macular hole and underneath its edges is removed with careful suction. The air is then replaced with a longer acting gas, the tiny wounds are sewn closed, and the patient is transferred to a stretcher and asked to lie face down.
The most difficult part of the surgery for the patient is not the surgery itself but the week following surgery. So far, it appears essential that care is taken to spend that whole week looking at the floor below the eye. This causes the bubble of gas in the eye to rise to the area of the macular hole and hold down the edges of the hole against the tissue where one wants it.
to stick. Of course, this looking down' can be accomplished just as well while sitting or standing as it can while lying on one's stomach. To help pass the time, many patients find they can read with the other eye or watch a small TV placed on the floor. A few have even watched a larger television upside down with a mirror placed between their legs.
Sleeping is usually accomplished by wedging the body in with pillows to reduce the likelihood of turning over in one's sleep and sleeping alternately with one eye and then the other buried into the mattress or the pillow. Most find that the week is quite tedious but not nearly as bad as imagined.
The bubble lasts for between eight and twelve days. We believe that the first seven days are most important and after that time the positioning requirements can be relaxed, although it is still forbidden to spend much time lying flat on ones back looking up at the ceiling. The bubble is gradually and naturally absorbed by the blood stream. It does not need to be removed mechanically. The patient is seen in the office the first day after surgery and instruction given on the use of some eye drops over the next week or so. There is a return visit on the seventh or eighth day. For the first time, at that appointment, the head can be legitimately raised and the eye checked to see if the macular hole has closed.
Whatever visual return is going to be obtained comes over a fairly long period. Much improvement is usually noted over the first two to three months, but improvement had been noted in some eyes for up to three years after the surgery.
Depending on the age of the hole there is about a one in ten chance that it will not close with surgery. If this occurs it is, of course, very disappointing but unless other problems ensue (which is not likely) the vision will be at least as good as it was before surgery. A second surgery is usually successful, but usually requires a longer period of positioning. The most common complication is the formation of a cataract in the operated eye. This often occurs within the first two years following surgery and eventually requires conventional cataract extraction and intraocular lens placement. This surgery is highly successful in restoring vision and is also performed as an outpatient under a local anesthetic. Since many patients with macular holes are in an age group where early cataracts are common, progression of a cataract after surgery is an extremely common event, quoted between 50 and 100. There is a quoted risk in vitrectomy surgery of approximately 1 to 2 of subsequent retinal detachment. Most retinal detachments can be repaired at a subsequent surgery, but can involve a decrease in central vision.
There is a three or four out of a hundred recurrence rate of macular holes, often occurring up to two years later. Re-operation is often successful in re-repairing such recurrences. This is definitely an eye surgery and carries with it the usually very small, but important statistical risks of infection, bleeding, even loss of the eye. I have not yet had any of these occur among my patients, but such problems certainly must remain a possibility.
Surgery for "Impending" Macular Holes
Sometimes an eye is seen that appears to be in the process of developing a macular hole. A few years ago patients with such eyes were offered a surgery to remove the vitreous traction and thereby reduce the risk of going on to develop a completed macular hole. However, a small but randomized study published in 1993 supported what many of us suspected anyway. Roughly four out of ten eyes both in the group operated on and among control (unoperated) eyes went on to complete macular holes. Furthermore, the operated eyes suffered the complications discussed above (especially cataract development) at the usual rates.
The study not only demonstrated that little if any benefit to surgery for "impending" macular holes, but also demonstrated that "impending" macular holes often resolve without any intervention (as often as six out of ten times.) I do not currently offer surgery until a definite macular hole can be demonstrated.