The retina is the light-sensitive tissue that lines the inside wall of the eye and enables sight. The macula is the central part of the retina that is responsible for seeing straight ahead. A macular hole is a break or hole in the center of the macula. This can be a significant problem because a healthy macula is needed to see the fine detail required for reading and driving. A macular hole is not related to macular degeneration; these are two different problems.
Causes and Associations
We know that macular holes are often related to age. They are most common in patients over 60. The most common reason for a macular hole is traction from the vitreous. The vitreous gel is normally clear and is mildly adherent to the retina lining the back of the eye. As we age, the vitreous gradually shrinks and pulls away from the back of the eye wall. This is a normal process and the eye produces natural, clear fluid that fills the areas where the vitreous has contracted. Sometimes patients see floaters when the vitreous begins to pull away from the retina.
A macular hole usually occurs when the vitreous is firmly adherent to the macula, such that it tears a hole as it pulls away. In addition, vitreous fibers that are left behind on the retinal surface can proliferate and contract, serving to stretch a hole and make it larger. Sometimes fluid in the eye can go through the hole and under the retina, creating a small retinal detachment.
Macular holes can also result from other problems such as trauma, high myopia, macular pucker, or retinal detachment.
Visual problems from a macular hole usually occur gradually. The first symptoms are often blurry and distorted central vision. Straight lines might look wavy, distorted or have missing segments. There may be a gray area or blind spot in the central vision. Sometimes a patient does not notice a problem for some time because they do not cover their good eye and realize that they have a problem looking with the eye containing the macular hole. Reading often becomes difficult.
Examination & Testing
It is important to be examined by an ophthalmologist, who can diagnose a macular hole by examining the eye. Testing visual acuity is one way to measure the functional severity of a hole. An Amsler grid is similar to a piece of graph paper that patients can use to detect subtle changes in their central vision. Patients look at the grid with each eye individually and report to their doctor if there are any missing areas or if the lines look distorted or wavy.
In addition, an ophthalmologist can obtain a scan using optical coherence tomography (OCT). OCT uses light to produce images of the retina. The resolution of the images is very fine, and doctors can see problems that exist above, below, and within the retina. During an OCT, a patient will sit and place their head in a chin rest while looking into a machine. The patient will see lights moving around. Nothing touches the patient and there is no pain. A doctor can use the OCT images to determine the size of the hole, whether it is getting smaller or larger, if there is fluid under the retina, and if there is still traction from the vitreous pulling the hole open.
What the Doctor Sees
When a doctor examines the patient, he or she will use a slit lamp that projects a bright light into the eye, and a lens to focus the light on the macula. Usually the doctor can see the macular hole. The doctor may note the size of the hole, appearance any subretinal fluid, and whether the vitreous has completely detached from the back of the eye or not. If the vitreous has not yet completely detached, the hole may improve once the vitreous does detach and traction is relieved.
In general, the only treatment for a macular hole is surgical. The size of the hole and the duration of the hole are the main factors in determining the likelihood of visual improvement after surgery. Larger and more longstanding holes are less likely to close than small holes that have recently developed. Sometimes, a hole can spontaneously close. This has been seen in holes resulting from trauma. Occasionally, while the vitreous pulls and creates a hole, the hole will close after the vitreous pulls away completely and traction is relieved. In general, the longer a hole has existed, the less likely it will close.
Macular holes are divided into four stages:
- A stage 1 hole is an impending hole. Such a hole may not involve the full- thickness of the retina
- A stage 2 hole is a full-thickness retinal hole that is small (less than 400 microns wide)
- A stage 3 hole is full-thickness and larger than 400 microns
- A stage 4 hole is the same as a stage 3 hole with complete detachment of the vitreous
The chances for successful surgery improve if the hole is smaller and has been present for less than six months. If left untreated, a hole may remain stable, or it may lead to a detached retina with worsening vision.
Because peripheral vision remains intact, patients will not go completely blind from a macular hole alone. If one eye has had a macular hole, there is a 10 to 15 percent chance that a hole will develop in the other eye. Some patients wonder if the “strain” placed on the good eye can contribute to poor vision in that eye, but this is not the case.
Aside from avoiding trauma, there is nothing that can be done to avoid a macular hole. Diet and exercise do not contribute to the formation of a hole. Occasionally covering each eye to test the fellow eye alone is the best way of detecting a change in central vision. In addition, having a regular, annual eye exam is the best way to catch a hole in its early stages.
The treatment is surgical. Surgeons will perform a vitrectomy, a procedure in which the vitreous gel is removed from the center of the eye. During a vitrectomy the surgeon makes three small ports in the eye wall: one for an infusion of fluid to maintain the eye’s shape, one for a small fiber-optic light, and one for an instrument such as forceps, a laser probe, or a vitrector which removes the vitreous gel. The surgeon uses an operating microscope and lenses to look through the patient’s pupil to the retina. After the vitreous is removed the surgeon will usually peel away any membranes on the surface of the retina or the most superficial layer of the retina, called the internal limiting membrane. Peeling these layers away has been shown to promote closure of the hole. Finally the surgeon will instill a gas bubble in the eye and instruct the patient to remain face down for up to a week. The procedure is normally performed under local anesthesia and as an outpatient. There is usually very little postoperative pain. Many surgeons employ 23 or 25 gauge instrumentation which does not require any sutures.
Positioning face down as much as possible is critical to the success of the surgery. A gas bubble rises, and if the patient positions face down, the bubble will rise to exert pressure in the back of the eye where the hole is located. This tamponade promotes closure of the hole and prevents any more intraocular fluid from going through the hole and under the retina. The gas that is injected is gradually reabsorbed by the eye. As the gas reabsorbs the eye’s natural fluids take its place.
There are special chairs and bed attachments that can be rented to assist in face-down positioning. It is not possible to be face down 100% of the time and it is ok to take brief moments of respite to eat, bathe and tend to other needs. Patients often strive to remain face down for 50 minutes out of every hour.
It is important to note that patients should not fly in an airplane while there is a gas bubble in their eye. The gas will expand at higher altitudes, which can cause pain, high eye pressure, and permanent visual loss. A gas bubble can also promote the formation of a cataract. Depending on the type of gas instilled, the bubble usually lasts from two to eight weeks.
After surgery a patient’s vision can be expected to be blurry because of the gas bubble. Successful closure of the hole can occur in up to 90% of cases, but the improvement in vision is more variable. Visual recovery usually occurs slowly and can continue for up to three to six months after surgery. Most patients experience some degree of noticeable visual improvement, but the vision is rarely restored to “normal.” Because a cataract will usually develop after vitrectomy surgery, it is often not until after a patient has had their cataract removed months after surgery that the patient realizes his or her best visual acuity.
Risks of any eye surgery include infection, retinal detachment, and worse vision than before the surgery. It is possible that the hole will not close after surgery. Because surgery to close a macular hole can be challenging and highly dependent on difficult postoperative positioning, many doctors will wait until visual acuity is 20/50 or worse before suggesting surgical treatment.
Author: Allen C. Ho, M.D.