All “macular degeneration” is not macular degeneration. There are other “macular” diseases, macular dystrophies and diseases that mimic macular degeneration.
Most of the “fakes” are confused with macular degeneration due to the presence of choroidal neovascularization, aka the “wet” form of macular degeneration. Remember that in wet macular degeneration, the sine qua non of the diagnosis is the presence of abnormal, neovascular tissue underneath the macula. Symptoms of these other macular diseases all include either fixed grey spots in the vision and/or distortion.
Myopic Degeneration is a condition seen in severely near-sighted individuals. Scarring, similar to that of dry macular degeneration, may develop in the macula and cause some loss of vision. The scarring usually is not too progressive, that is, it moves very, very slowly. At times, choroidal neovascularization may develop in the same way as wet macular degeneration. Treatment options are similar. Patients typically are very near-sighted and younger than the average patient with macular degeneration.
Idiopathic Choroidal Neovascularization. Another condition that occurs in patients younger than 50 years old. The choroidal just develops in an otherwise “normal” looking eye, that is, the macula looks completely normal. There is no scarring, drusen or fluid. There may be associated signs of retinal inflammation.
In this condition, there is sudden, but persistent change of vision developing in a younger patient. Fluorescein angiography demonstrates the presence of choroidal neovascularization. Treatment options include Avastin® (bevacizumab) or other anti-VEGF treatments. Long term follow-up is recommended.
Ocular Histoplasmosis (OHS) is a disease that is transmitted by a fungus (histoplasma capsulatum) found in bird (usually chickens) and bat droppings. The fungus becomes air-borne and gains entry through the lungs. At this point, it may cause cold or flu-like symptoms. A small percentage of patients may go on to develop retinal involvement.
Retinal involvement includes peripheral scarring, also known as “histo spots,” and, guess what, choroidal neovascularization underneath the macula.
Ocular histoplamosis is a leading cause of blindness in the 20-40 year old age group. It is very common in areas such as the Mississippi River Valley. It is not uncommon that a patient has had exposure to chicken farming.
Other, more uncommon causes included choroidal neovascularization due to trauma (choroidal rupture), angioid streaks (seen in pseudoxanthoma elasticum and Ehler’s Danlos Syndrome).
What does this mean? There are several diseases that behave and are treated similar to wet macular degeneration. It is important to note the others develop much younger than typical macular degeneration and have slightly different histories or physical findings. All do have choroidal neovasculization as a common denominator and all probably can be treated with anti-VEGF.
They are; however, not macular degeneration.
Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist