Retinal Detachment Repair
The retina is a "Saran Wrap" thin membrane which is held to the inside back portion of the eyeball by a kind of suction force. In the front part of the eye the retina is firmly attached at a ring just behind the lens called the pars plana. In the back part of the eye, the retina is continuous with-the optic nerve-which carries 3 million nerve fibers back to the brain. In between the pars plana and the optic nerve the retina is attached by suction.
The interior portion of the eye is filled with a material called vitreous, which is like a thin bag of jelly. As one gets older, the vitreous tends to shrink, a process which is accelerated by prior cataract extraction or being greatly nearsighted. The bag of vitreous is also attached firmly in the front part of the eye at the pars plana. However, as the vitreous shrinks, it ultimately strips itself free from the surface of the retina in the back of the eye and begins to bobble around in the fluid. If it happens that the vitreous was glued on too tightly at a single point or several points just behind its firm attachment in the front part of the eye, the hobbling of the vitreous jelly bag can tear the retina at these points. Such a tear potentially breaks the suction holding the retina on. Depending upon the strength of the suction force that holds the retina on, the size of the tear, and the continued traction of the vitreous jelly bag on the tip of the tear, the retina may detach.
In principle retinal detachments are fixed by finding all of the tears and adequately closing them. It is both that simple and that complex!
There are two commonly used initial methods for repairing a detached retina. One, pneumatic retinopexy, we will call the "bubble procedure". The other, scleral buckling, we will call the "buckle".
Both procedures almost always are done as an outpatient under a local anesthetic. The eye is made numb by injecting an anesthetic material not into the eyeball, but rather in the orbit near the eye using a long, thin needle. Often, a medication is given in a vein beforehand so that the patient doesn't care what happens next.
The bubble and the buckle both involve irritating the tissue around each of the retinal tears. This is typically done by looking into the eye using the indirect-ophthalmoscope (that bright light on the surgeon's forehead), while pushing gently on the outside of the eye using a freezing (cryopexy) probe. When a foot pedal is depressed, the tip of the probe becomes very cold, producing a small area of freezing that involves the retina and the tissues immediately underneath it. Using multiple small freezes like this, each of the tears is surrounded. Irritated tissue forms a scar once the retina is brought back into contact with the tissue underneath it. This scars forms over the next 2 weeks or so. The process is therefore a bit more like gluing furniture than welding. Both the "bubble" and "buckle" are the same up to this point. After this, they differ.
In the "bubble procedure" an injection of an expanding gas is made into the back of the eye with a short;- very-skinny-needle: You the patient are then asked to position yourself over the next 7-10 days in such a manner that the bubble, rising in the fluid in the back of the eye, plugs the tear(s). This reestablishes the suction, the fluid underneath the retina reabsorbs, and the retina reattaches. After that, the bubble is used like a splint, or, in the furniture gluing analogy mentioned above, like a furniture clamp. You can readily see that if the tear that needs to be closed is in the lower portion of the eye or if there are several tears widely spaced apart, this procedure cannot be effective and is therefore not offered.
When the eye wakes up, the bubble is seen as a shimmering surface which is distinguishable from the retinal detachment by the fact that it is always seen as being on the floor no matter which way the head is moved. The bubble is reabsorbed by the blood stream and expelled through the lungs as a natural process over the next 7-10 days.
The "bubble procedure" has the advantage that it produces only minimal discomfort and the vision that will return tends to return quickly over a matter of days to weeks. It has basically two disadvantages: one is the need for positioning, which is mentioned above. Depending on the location of the tear, this can be anything from a minor nuisance to a major problem. Physical inability to maintain the position is one contraindication to doing this procedure. Its other problem is that if one takes all eyes to which the "bubble procedure" is applicable, the procedure works only 7 or 8 out of 10 times. This does not mean that the other 2 or 3 out of 10 eyes go blind. It usually means that these eyes go on to scleral buckling, the other, more extensive procedure. Usually, the need for scleral buckling is obvious within the first few days.
The "buckle" is performed in one of the operating theaters at the outpatient Surgery Center. It begins with the anesthetic and freezing treatment mentioned above. The tissues around the eye are then opened using scissors so that access can be gained to the side of the eyeball. On a spot or spots on the outside of the eye corresponding to where the tears are on the inside, a piece a silicone rubber is sewn in such a way that when the sutures are tightened up, the silicone indents the eye wall, making a hill on the inside of the eye for the tear to rest on. Often, some of the fluid under the retina is drained out of the eye using a fine needle while the process is carefully monitored using the indirect ophthalmoscope. The drainage and the indentation from the buckle (usually close the breaks. This procedure has the advantage that it works 9 or 9 1/2 times out of 10 as a first procedure. It has the disadvantage that it typically hurts considerably more, at least for the following day or two, than does the "bubble procedure". The vision that will return, returns more slowly, typically over time measured in weeks or months. The major advantage is that the "buckle" typically does not require any special positioning. Furthermore, this procedure can be used to repair retinal detachments to which the "bubble procedure" cannot be usefully applied.
The most common trouble with each of these procedures, the possibility that in one operation the retina may not be attached, has already been covered above. A subsequent attempt at repair can be entertained using a combination of the procedures already mentioned or other techniques that are available, but not covered here (e.g., vitrectomy). About 7 in a 100 eyes develop some generalized scarring referred to as PVR (proliferative vitreoretinopathy) which shortens the retina, makes it less elastic, and sometimes holds the breaks open despite efforts to close them. Usually, some combination of techniques can be used to repair retinas that develop this problem but sometimes, even with the best efforts, PVR results in blindness.
Other risks include infection (either in the inside of the eye or of the buckling element placed on the surface of the eye ball), perforation of the eye with the anesthetic needle, bleeding, double vision, glaucoma, and acceleration of cataract formation. All of these are quite uncommon, but deserve mention.
All of this has been directed at reattaching the retina. Once the retina is reattached, the process of visual improvement begins. In the case where the center of the retina has not detached, the visual results are usually quite good. When the center of the retina has been detached, the visual results are less impressive, only rarely as good as the vision prior to the detachment, but sometimes close to it.