Description of a Macular Hole
A macular hole is a condition in which there is partial or full thickness area of retinal tissue missing in the macular area. The macula is the part of the retina responsible for central vision so anything affecting the macula will likely affect visual acuity and quality of vision.
The macular hole may be described as lamellar (partial thickness) which is the result of cystic edema (swelling) which has progressed and caused the inner retinal layer to rupture. The hole could also be full thickness which consists of loss of the inner retinal layer as well as excavation of the retinal tissue. The vision will typically be better in the case of a lamellar (partial thickness) hole.
Macular holes are described in stages based on how advanced the hole is. Stage 1 is a macular cyst. At this stage the vitreous is pulling on the macula but has not detached yet. There may be slight reduction in visual acuity (20/25-20/70) or distorted vision (metamorphopsia). Half of all cases do not progress past this stage because the vitreous detaches, traction resolves and vision returns to normal. Stage 2 is a tear at one side of the fovea (the center of the macula) and over time the tear may spread. Visual acuity at this stage is typically between 20/25 and 20/100 and 22% will spontaneously resolve while 55-70% will progress without treatment. Stage 3 is when the tear has progressed into a complete hole without a vitreal detachment. Stage 4 is a full thickness macular hole with a posterior vitreal detachment. The vision in this case ranges between 20/100 and 20/400 and up to 45% will degrade without treatment. Only 10-20% of cases progress to this stage.
Causes of a Macular Hole
Macular hole formation could be caused by anything that causes cystoid macular edema such as ocular surgery, inflammation, injury, certain systemic and topical medications, diabetes and most commonly traction or pulling at the macula.
If the macular hole is due to something pulling on the macula it is known as an idiopathic macular hole. This type of hole is more common in someone over the age of 60, is bilateral in 6-22% of cases and is more frequent in women than men.
Vitreomacular traction is a common cause of macular holes. The vitreous is a gel-like material inside the eye which naturally degenerates over time. It is attached to the retina in several places and as it degenerates it must detach from the retina. There are instances when the vitreous begins this process of pulling off the retina but remains attached at the macula. The macular surface becomes pulled with the vitreous and a macular hole may occur. An epiretinal membrane is an abnormal layer of cells which grows across the macula and begins to distort the tissue. It has the potential to create a macular hole and may start growing as a result of the hole.
If one eye has a macular hole then there is a 28-44% chance the other eye will develop one if it has not already had a vitreous detachment. Once the vitreous has detached, the condition is stable and there is little to no chance of a macular hole forming. If one macula has a hole and the fellow macula has signs of pigment degeneration the chances of that eye developing a hole increase to 80%.
Symptoms of a Macular Hole
The severity of symptoms depends on the stage of the hole. It will be noticed commonly by decreased visual acuity and metamorphopsia (distortion).
Treatment/prognosis of a Macular Hole
It is very important to determine what stage the macular hole is in order to intervene with proper treatment when necessary. A thorough microscopic exam of the macula is necessary though it is sometimes difficult to determine the stage without special equipment. There are two special tests that are typically used for diagnosis. The first technique is a fluorescein angiography (IVFA) which is the old standard of care. An IVFA is a test which requires dye be injected into a vein in the arm and as the dye passes through the retinal blood vessels pictures are taken with UV light. The problem with this test is that some people are sensitive to this dye and the injection could be fatal for them. The second diagnostic test which is becoming much more popular is called optical coherence tomography (OCT). The OCT takes a quick cross sectional picture of the retina by a technique known as interferometry. Light beams are directed into the eye at certain angles and the amount of interference is measured creating a very detailed image of the entire depth of the retina. The new OCT machines are spectral domain. They give a much more detailed image (5-10 microns) than the older time domain OCT machines. The advantage to an OCT picture is that it is much less invasive, completely safe and much faster than a fluorescein angiography. It takes a couple seconds to get an image just like taking a picture with a regular camera.
There is also something known as a pseudohole which is caused by the traction of an epiretinal membrane giving the appearance of an impending hole. A regular biomicroscope may make the differentiation difficult but special testing with an OCT will give an obvious diagnosis.
Below is an OCT image of a normal macula taken with the iVue OCT machine
This is an OCT image taken with the RTVue OCT which shows vitreomacular traction. You can see the impending vitreal detachment labeled as “EVOLVING PVD.” The arrow to the left shows the vitreous pulling at the macula.
This RTVue OCT image shows a full thickness macular hole. You can see that the tissue below the macula is completely missing.
A vitrectomy (surgery to remove the vitreous) is a possible treatment in order to stabilize the condition. If done in stage 1 it has been shown to prevent the progression to a full thickness hole. If done in stage 2 there may not be an improvement in visual acuity but there is stability of visual acuity. Visual success is also much better in acute holes versus longstanding holes. If there is an epiretinal membrane present then success is contingent upon removal of the membrane during surgery.
The treatment for a macular hole is determined on a case by case basis. The risks and benefits must always be weighed. The other eye should be considered and whether it is likely or not likely at all to also develop a macular hole. The length of time the hole has been present must be considered as well as any associated epiretinal membranes. The cause of the macular hole must also be looked at. If it was caused by trauma and there is surrounding damage then the procedure may not be beneficial.