ARMD is the leading cause of legal blindness in persons over the age of 55. Early symptoms include a reduction in reading speed, inability to read fine print, and skipping letters or lines when reading. Later symptoms can include distortion of straight lines or dark or missing areas in the central vision.
The macula is the central part of the retina and allows us to read fine print clearly and see colors vividly. It is this area of the retina that deteriorates in ARMD. There are 2 forms of ARMD. Everyone who has macular degeneration starts out with the dry type and 20% progress to the wet type over the course of a lifetime. Macular degeneration in its most severe forms almost never causes total blindness. Usually only central vision is lost. It is a disease that leaves older persons unable to read and drive. However, nearly all patients will still have enough vision to care for themselves.
20% of patients with dry degeneration will eventually develop abnormal blood vessels under the retina that can bleed and leak fluid. Patients often have abrupt vision loss with distortion of straight lines, or a stationary, dark or blurry spot in the central vision of one eye. The vision can worsen rapidly in a few days or weeks. Treatment can include traditional laser, injection of certain pharmaceutical agents such as Lucentis™, Avastin™, or corticosteroids into the eye, and/or ocular photodynamic therapy (cold laser). Each treatment has its risks and benefits and is individualized for the patient by the retina specialist. Multiple treatments may be necessary to control the disease. The treatments usually only slow down the disease and neither cure the disease nor commonly make the vision better.
Patients who develop macular holes, may initially just experience distortion of vision and ultimately may end up with a loss of central vision with a dark blind spot in the central vision. When someone with a macular hole tries to read, letters may be missing in the center of a word. Fortunately, macular holes can be repaired with surgery. Surgery can be done as an outpatient, but will require face-down positioning for a period of eight or more days. Usually, surgery is successful in repairing 80% or more of macular holes, resulting in visual improvement. Alternatives to face down positioning are available in certain cases. Vision will improve after surgery but almost never recovers to normal levels.
Your doctor will discuss with you all of the surgical options available for the treatment of these relatively common conditions. It is important to remember that patients who have macular hole in one eye may develop and have a 5-15% chance of developing macular hole in the fellow eye.
Other forms of abnormalities between the vitreous and retina include macular pucker, which can be repaired with improvement in vision in 75% of patients who have symptoms such as distortion or decreased vision.
Histoplasmosis is an infectious disease caused by Histoplasma capsulatum, a yeast like fungal organism that lives in the gastrointestinal tract of birds and is spread to humans by inhalation of dried and airborne dust containing spores. Almost everyone who lives or spends time in the Ohio and Mississippi River valleys has had systemic Histoplasmosis (almost 80 million people).
Most of us get exposed to histoplasmosis and develop a flu-like illness and heal from it without problems. About 10% of persons who get this flu-like illness can develop scars in the back of the eye affecting the retina and a vascular layer under the retina called the choroid (Ocular Histoplasmosis). Sometimes these scars can occur around the optic nerve or near the macula. The scars themselves do not cause any visual problems. Many years later and generally in the prime of life (ages 20 to 55) these scars can be sites for the development of new blood vessels under the retina called choroidal neovascularization. Depending on where these blood vessels grow, they may or may not cause vision loss. The closer they are to the macula the more likely they are to cause vision loss. These new vessels are most often treated with laser, which can produce a blind spot at the site of treatment but will prevent further vision loss. Even with successful laser treatment, choroidal neovascularization may come back 25% of the time in the first five years in the treated eye. In some cases the abnormal blood vessels grow directly under the very center of the macula (fovea) and cannot be treated with laser because the resulting blind spot would be in the center of vision. In these cases, medical therapy with intravitreal injection of Avastin™ and/or steroids, cold laser treatment (ocular photodynamic therapy), or simply conservative observation may be recommended. In some very severe cases, surgical removal of blood vessels may be performed.
It is very important to monitor central vision in both eyes using an Amsler grid daily if you have ocular histoplasmosis and especially if the vision has been affected in one eye. Patients who develop choroidal neovascularization in one eye have a 25% chance of developing the same in the fellow eye within 3 years if they have histo scars close to the macula.
Since the retina is an extension of the brain, just as the brain can have small strokes develop within it, the retina can also develop either strokes that occur from obstruction of the arterial or the venous circulation. If the veins and the retina become obstructed, the area that the vein drains in the retina, cannot be drained properly so as blood flows into the retina through the normal arteries, blood cannot leave the retina. As a result, fluid and blood leak in to the retina causing the retina to swell causing reduced vision.
Vein occlusions can be treated with the use of intraocular injections of special medications such as corticosteroids or Avastin (an antibody that inhibits a chemical called vascular endothelial growth factor). In addition, laser treatment as well as a possible surgery may be indicated in some cases. These disease processes start relatively rapidly over the course of a few weeks or months, but may persist and heal over the course of 24-48 months. When the vein occlusions become so severe that they actually start interfering with the blood flow into the eye, these vein occlusions become ischemic (loss of blood flow to the retina), resulting in severe vision loss and much greater rates of complications such as neovascular glaucoma, a kind of glaucoma that can result in blindness very rapidly. Fortunately, with modern treatment, even these very late stages of disease can be treated to prevent loss of the eye and limit the amount of vision loss. Visual prognosis for these conditions is variable and very guarded. Your doctor will discuss with you the treatment options available for the specific vein occlusion seen in your eye.