Description, Causes and Risk Factors:
The retina is a thin film of nerve tissue lining the back of the eye. The tiny central area used for all sensitive visual tasks such as reading and recognising faces is referred to as the macula. A macular hole is a small break in the macula, located in the center of the eye's light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail.
A macular hole can cause blurred and distorted central vision. Macular holes are related to aging and usually occur in people over age 60.
There are three stages to a macular hole:
Partial-thickness holes (Stage II). Without treatment, about 70 percent of Stage II macular holes will progress.
Full-thickness holes (Stage III).
Foveal detachments (Stage I). Without treatment, about half of Stage I macular holes will progress.
The size of the hole and its location on the retina determine how much it will affect a person's vision. When a Stage III macular hole develops, most central and detailed vision can be lost. If left untreated, a macular hole can lead to a detached retina, a sight-threatening condition that should receive immediate medical attention.
Most of the eye's interior is filled with vitreous, a gel-like substance that fills about 80 percent of the eye and helps it maintain a round shape. The vitreous contains millions of fine fibers that are attached to the surface of the retina. As we age, the vitreous slowly shrinks and pulls away from the retinal surface. Natural fluids fill the area where the vitreous has contracted. This is normal. In most cases, there are no adverse effects. Some patients may experience a small increase in floaters, which are little "cobwebs" or specks that seem to float about in your field of vision.
However, if the vitreous is firmly attached to the retina when it pulls away, it can tear the retina and create a macular hole. Also, once the vitreous has pulled away from the surface of the retina, some of the fibers can remain on the retinal surface and can contract. This increases tension on the retina and can lead to a macular hole. In either case, the fluid that has replaced the shrunken vitreous can then seep through the hole onto the macula, blurring and distorting central vision.
Macular holes can also occur in other eye disorders, such as high myopia (nearsightedness), injury to the eye, retinal detachment, and, rarely, macular pucker.
Macular holes often begin gradually. In the early stage of a macular hole, people may notice a slight distortion or blurriness in their straight-ahead vision. Straight lines or objects can begin to look bent or wavy. Reading and performing other routine tasks with the affected eye become difficult.
Although clinical examination remains the gold standard for diagnosis. These tests assist in making a diagnosis of macular hole and in differentiation from other pseudo hole conditions.
Watzke-Allen Test: This is perfonned by placing a thin vertical slit lamp beam directly on hole during contact lens biomicroscopic examination. Patient with positive Watzke-Allen sign will perceive an interruption in the light beam. A normal appearing or only narrowed beam is a negative result. This is a highly sensitive and specific clinical test distinguishing full thickness macular holes from pseudo-holes. If negative with vertical beam, a horizontal beam can be tried. Another useful maneuver is moving the slit lamp beam slowly across the macula and asking the patient whether at any time the beam is clotted or broken.
Laser Microperimerry: The aiming beam on a laser delivery system is also a good test for assessing the presence or absence of a full thickness macular hole. The patient is seated at the laser with contact lens in place. A 50 Painting beam is used to test central areas of retina focally for sensitivity. The inability of the patient to perceive the spot in the area of presumed macular hole (absolute scotoma) confirms the lack of retinal tissue in that locaton (full thickness hole).
Optical Coherence Tomography (OCT): This is a new diagnostic imaging technique for high resolution imaging ofthe retina. Cross sectional images of retina can be obtained with 10 longitudinal resolution. OCT is performed with patient sitting at slit lamp into which a 78D lens has been mounted. A superluminescent diode laser produces a probe beam of wavelength 840 units (infrared) that is focussed in the retina. A pair of galvanometrically driven orthogonal scanning mirror scans the beam within the eye and area of retina scanned can be visualised with an infra red camera. Cross sectional images of retina are displaced in colours corresponding to regions of high relative optical reflectivity (red and while) or low reflectivity (blue to black). High resolution tomographic images provided by OCT can help differentiate true macular holes from pseudo holes and lamellar holes.
Retinal thickness analyzer also have been used to differentiate between macular holes and mimicking conditions.
Fluorescein Angiography: This may be a useful adjunct to biomicroscopy. In stage I faint hyper nuorescence or more typically no abnomlality at all is seen on fluorescein angiography. In stage 2 holes, nuorescein angiography may reveal a round area of window defect or may remain normal. Stage 3 and 4 holes typicall produce a window dcfect with early transmission of fluorescence in phase with choroidal filling through the central retinal defect. No late leakage or accwnulation of dye is seen. In some cases particularly those involving very small holes or holes accompanied by RPE (retinal pigment epithelium) abnormalities. Distinguishing the characteristic hallmark window defect may be difficult.
Although some macular holes can seal themselves and require no treatment, surgery is necessary in many cases to help improve vision. In this surgical procedure--called a vitrectomy--the vitreous gel is removed to prevent it from pulling on the retina and replaced with a bubble containing a mixture of air and gas. The bubble acts as an internal, temporary bandage that holds the edge of the macular hole in place as it heals. Surgery is performed under local anesthesia and often on an outpatient basis.
Following surgery, patients must remain in a face-down position, normally for a day or two but sometimes for as long as two-to-three weeks. This position allows the bubble to press against the macula and be gradually reabsorbed by the eye, sealing the hole. As the bubble is reabsorbed, the vitreous cavity refills with natural eye fluids.
Maintaining a face-down position is crucial to the success of the surgery. Because this position can be difficult for many people, it is important to discuss this with your doctor before surgery.
The most common risk following macular hole surgery is an increase in the rate of cataract development. In most patients, a cataract can progress rapidly, and often becomes severe enough to require removal. Other less common complications include infection and retinal detachment either during surgery or afterward, both of which can be immediately treated.
For a few months after surgery, patients are not permitted to travel by air. Changes in air pressure may cause the bubble in the eye to expand, increasing pressure inside the eye.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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