X. MACULAR HOLES AND OTHER CHANGES

A hole may form selectively in the macula (central part of the retina), thereby decreasing the ability to read or write with the affected eye. This results from a peculiar attachment of the vitreous to the macula. When a patient advances in age, the vitreous, which is normally attached to the retina, tends to become detached from it, but it often remains attached to the macula (Figure 17). The formation of a macular hole creates a small round piece of vitreous and retinal tissue, called operculum. It is located in front of the macula. The development of a macular hole is divided in 4 stages. In stage I, no macular hole is visible, because the operculum remains at the level of the retina. Stage II may follow after weeks or months. An incomplete macular hole forms, which is often crescent-shaped. At this time the operculum is slightly in front of the macula. In stage III, the hole has its full diameter and the operculum is not only detached and in front of the macula but also moves up or down with eye movements. In stage IV, the vitreous detaches completely from the retina, dragging the operculum into the vitreous cavity. The development of a full macular hole may take months. Its progress is accompanied by a gradual loss of vision for small objects. However it also happens that the patient does not notice a decrease of vision, because he/she never closed the unaffected eye.

Fig. 17 Cross-section of a human eye. The cornea and the lens are at the left. The retina is  the thin layer of tissue that lines the back of the eye. the vitreous is the clear jelly that normally fills the inside of the eye. In this case, the vitreous is grossly detached from the retina above, and flatly detached below. It remains attached at the back, causing a macular hole.

Over 50% of the stage I macular holes will develop into further stages and reach stage IV. Less than 50% undergo regression because the vitreous separates completely and spontaneously from the macula. It is essential for the patient to examine the vitreous of the unaffected eye because a macular hole may also develop in the other eye. Usually, ophthalmologists decide that the vitreous is completely detached from the retina if they see a doughnut-shaped opacity in the vitreous (called a Weiss ring). This opacity does not come from the macula but from the optic nerve, which is an area that is normally blind. In order to determine positively whether or not the vitreous is still attached to the macula, the doctors at the SRA Foundation have an expert in the field use an exceptionally strong slit lamp with a special lens placed in front of the cornea (Figure 18). Another method is to examine the suspected macula with an Optical Coherence Tomograph (OCT). The vitreous may be detached from the retina everywhere, but still attached to the macula. If it is, a macular hole may develop when the vitreous remains attached to the macula. A macular hole may develop in about 20% of the cases. If the vitreous detaches from the macula, a macular hole  will not develop in this eye.

Fig. 18 Slit-lamp microscope to which is attached a special lens placed in front of the patient's cornea.

Operation for macular hole. Not all macular holes need to be operated upon. Stages III and IV generally need surgery. The operation requires complete removal of the vitreous with a vitrectomy instrument. Special care is taken to remove the vitreous that is still attached around the macular area. The retina itself is normally covered with a very thin glassy membrane, called the internal limiting membrane. If this membrane appears boggy around the macula, it is removed. Then, expansile gas is injected to replace the vitreous, and the patient must lie in a face-down position for about two weeks. The patient’s ordeal can be relieved by using a special device (Figure 19).

Fig. 19 Device used to relieve the discomfort of the patient lying on his face. Left, it consists of a board that slides . The board is covered with U-shaped foam rubber. Inside the U, there is an oval hole in the board. Right, the patient's head rests, face-down, on the U-shaped foam rubber.

Results from the operation vary according to the size and shape of the macular hole. More than 75% of the cases get a definite improvement in their vision, with some improving to 20/40 vision. A recovery to 20/20 is unusual but may occur.

Other Macular Changes

A somewhat frequent change is the case of a macula that has lost the power of seeing and yet shows no visible changes.  Such a case is particularly challenging because it may be the indication of serious eye disease, or may result from malingering.