Retinal Detachment
How the Eye Works
Light is focused onto the retina by the clear dome over the eye (the cornea) and the lens, which lies behind the iris (the colored part of our eye). The retina lines the back of the eye like wallpaper. It senses the light by converting the light signals into electric/chemical signals that are understood by the brain. The central part of the retina is called the macula. The macula is responsible for most of our ability to read and see fine detail. If the retina is pulled off, or “falls away” from the back of the eye, it begins to lose its function and eventually “dies” from scarring. The purpose of any surgery is to put it back where it belongs so it will function.
Posterior Vitreous Detachment (PVD)
A clear, jelly-like substance called the vitreous fills the space behind the iris and lens and is typically attached to the retina. As we age, the vitreous liquifies and separates from the retina near the back of the eye, over the macula. This separation is called a Posterior Vitreous Detachment, or PVD. A PVD naturally occurs in 40% of people by age 40 and nearly 70% by age 70; however, it can occur in younger patients who are nearsighted or who have had an eye injury or surgery. As the vitreous separates from the retina one will often see floaters. These floaters appear as dots, circles or curly lines, which move in front of your vision and move as your eye moves.
Retinal Tears and Detachment
The vitreous can pull on the retina as it separates, stimulating the retina, which is perceived as flashes of light. Very rarely, the vitreous may tear a retinal blood vessel and cause a small bleed or hemorrhage, which is perceived as a shower of spots or floaters or haze. If the vitreous rips the retina, this retinal tear will allow liquid vitreous to fall behind the retina. As the fluid falls behind the retina, the retina separates from the back of the eye. The retina begins to lose its function and this is perceived as a curtain or veil over the vision. This is called a retinal detachment. Your doctor will try to find the retinal tear that caused the retinal detachment develops. The examination involves dilating the pupil and looking at the vitreous and retina. This involves pressing on the peripheral retina, and thus the eye, called scleral depression.
Rhegmatogenous Retinal Detachments
The most common type of retinal detachment occurs when a PVD causes a retinal tear. The pulling from the vitreous gel on the tear is thought to allow fluid to fall behind the retina and pull it away from the back wall of the eye. This type of retinal detachment is called a “rhegmatogenous” retinal detachment. Tears caught early can be fixed by sealing them with laser burns, or causing scarring in the area with a freezing method, called cryotherapy or cryopexy. Small detachments can sometimes be “walled off” with laser. If there is too much fluid around the hole, these methods will not work.
Surgeries for Rhegmatogenous Retinal Detachments
Three procedures can be used to repair a retinal detachment: pneumatic retinopexy, scleral buckle procedure, and vitrectomy. The primary goal is to find the retinal tear, treat the tear so a scar will eventually seal around it and close the hole off so no more fluid will flow through it. The success rate is approximately 90% with one procedure and 95% with two. Five percent fail from the development of scar tissue inside the eye that pulls the retina off, a disease process called proliferative vitreoretinopathy, or PVR. In all surgeries, a gas bubble is usually required to repair any retinal tear or detachment. Gas in the eye pushes the retina in place during the healing phase. The doctor may require you to position your head for as much as possible for 1 to 2 weeks to allow this healing to be successful. The body absorbs this gas bubble over several weeks to months. Vision is poor for the first 6 to 8 weeks after surgery until at least 50% of the gas is absorbed.
A pneumatic retinopexy involves the injection of a gas bubble under local anesthesia. The bubble expands and closes off the hole from inside the eye. Cryotherapy is added before or laser after the injection of gas to “scar off” the tear. A patient must be able to keep the bubble over the hole for at least a week, so only certain types of retinal detachments in cooperative patients are treatable. Patients may not air or mountain travel while the bubble is in the eye as this causes high eye pressure. If this procedure fails, another type of procedure may be used.
A scleral buckle procedure is performed under local anesthesia. The surgeon treats the tear with cryotherapy or laser. A small piece of silicone is sutured (sewn) to the outside eye wall, that pushes or “buckles” the eye wall in and therefore closes the tear from “outside-in.” Scleral buckling surgery’s side effects include astigmatism, increased nearsightedness, double vision and postoperative pain.
A pars plana vitrectomy is performed under local anesthesia. The vitreous gel is removed with a special cutting/sucking device and injects air into the eye to push the retina back in place while sucking out the fluid from under the retina. After the retina is flat, a scleral buckle may be added for extra support. Laser is applied to seal the tear. The air is replaced with a special inert gas that will help keep the retina in place during the healing process. Vitrectomy surgery has side effects, which include cataract formation, glaucoma and diminished vision until the gas bubble “dissolves.”
Surgical results
Most retinal detachments are repaired with one procedure; however if one fails, an additional surgery can be performed to reattach the retina. If the retinal detachment does not involve the center of the macula, there is a good chance that the vision will remain at the level it had prior to the retinal detachment. If the macula is detached, (the retinal detachment involves the central retina), the chance of recovering vision drops substantially, especially with time. Patients can develop PVR, as mentioned above, and this will require pars plana vitrectomy surgery to remove this exuberant scar tissue. Patients can also develop scar tissue on the macula, which wrinkles or “puckers” the central vision as a late complication of retinal detachment. If the “macular pucker” is severe and causes visual loss and distortion, the pars plana vitrectomy surgery can be performed to remove the “pucker.”