Presumed ocular histoplasmosis syndrome
Encyclopedia
Presumed ocular histoplasmosis syndrome (POHS) is a disease syndrome
affecting the eye
that is characterized by peripheral atrophic chorioretinal scars, atrophy or scarring adjacent to the optic disc
and maculopathy
.
The loss of vision in POHS is caused by choroidal neovascularization
.
The word "presumed" is also emphasized because the condition has also been found in locations where histoplasmosis
is rare.
is required for diagnosis and follow-up of patients with POHS.
. A vitreo-retinal specialist should be consulted for proper management of the case.
Presumed ocular histoplasmosis syndrome and age-related macular degeneration (AMD) have been successfully treated by the drug Bevacizumab
(trade name Avastin, Genentech
/Roche). Ophthalmologists are using Avastin "off-label" to treat AMD and similar conditions since research indicates that vascular endothelial growth factor (VEGF) is one of the causes for the growth of the abnormal vessels that cause these conditions. Some patients treated with Avastin had less fluid and more normal-appearing maculas, and their vision improved. Avastin injections into the affected eye have been used by retina specialists since early 2005. Thus there is no long term 10 to 15 year follow up data for possible late complications. Early treatment is critical to maintaining vision.
Other treatments include Ranibizumab
(trade name Lucentis) which is approved by the FDA for intraocular use. Lucentis uses a smaller molecule compared to Avastin and according to GenenTech, the smaller molecule helps lower the systemic toxicity of the drug, thereby lowering the overall risks compared to Avastin. However, Lucentis costs approximately $1,600 per injection compared to less than $100 per injection for Avastin. Research has shown that Avastin and Lucentis to be equally effective in the treatment of POHS and AMD.
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
affecting the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
that is characterized by peripheral atrophic chorioretinal scars, atrophy or scarring adjacent to the optic disc
Optic disc
The optic disc or optic nerve head is the location where ganglion cell axons exit the eye to form the optic nerve. There are no light sensitive rods or cones to respond to a light stimulus at this point. This causes a break in the visual field called "the blind spot" or the "physiological blind spot"...
and maculopathy
Maculopathy
A maculopathy is any pathological condition of the macula, an area at the centre of the retina that is associated with highly sensitive, accurate vision.-Examples Of Maculopathies:...
.
The loss of vision in POHS is caused by choroidal neovascularization
Choroidal neovascularization
Choroidal neovascularization is the creation of new blood vessels in the choroid layer of the eye. This is a common symptom of the degenerative maculopathy wet AMD .-Causes:...
.
Causes
It is thought to be caused by Histoplasma capsulatum, but the fungus has rarely been isolated from cases with POHS.The word "presumed" is also emphasized because the condition has also been found in locations where histoplasmosis
Histoplasmosis
Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum. Symptoms of this infection vary greatly, but the disease primarily affects the lungs...
is rare.
Diagnosis
Fluorescein angiographyFluorescein angiography
Intravenous Fluorescein angiography or fluorescent angiography is a technique for examining the circulation of the retina using the dye tracing method...
is required for diagnosis and follow-up of patients with POHS.
Treatment
Treatment requires careful consideration of FA findings and few cases may respond to corticosteroids and laser photocoagulationLaser photocoagulation
Laser coagulation or laser photocoagulation surgery is used to treat a number of eye diseases and has become widely used in recent decades...
. A vitreo-retinal specialist should be consulted for proper management of the case.
Presumed ocular histoplasmosis syndrome and age-related macular degeneration (AMD) have been successfully treated by the drug Bevacizumab
Bevacizumab
Bevacizumab is a drug that blocks angiogenesis, the growth of new blood vessels. It is commonly used to treat various cancers, including colorectal, lung, breast, kidney, and glioblastomas....
(trade name Avastin, Genentech
Genentech
Genentech Inc., or Genetic Engineering Technology, Inc., is a biotechnology corporation, founded in 1976 by venture capitalist Robert A. Swanson and biochemist Dr. Herbert Boyer. Trailing the founding of Cetus by five years, it was an important step in the evolution of the biotechnology industry...
/Roche). Ophthalmologists are using Avastin "off-label" to treat AMD and similar conditions since research indicates that vascular endothelial growth factor (VEGF) is one of the causes for the growth of the abnormal vessels that cause these conditions. Some patients treated with Avastin had less fluid and more normal-appearing maculas, and their vision improved. Avastin injections into the affected eye have been used by retina specialists since early 2005. Thus there is no long term 10 to 15 year follow up data for possible late complications. Early treatment is critical to maintaining vision.
Other treatments include Ranibizumab
Ranibizumab
Ranibizumab is a monoclonal antibody fragment derived from the same parent mouse antibody as bevacizumab . It is much smaller than the parent molecule and has been affinity matured to provide stronger binding to VEGF-A...
(trade name Lucentis) which is approved by the FDA for intraocular use. Lucentis uses a smaller molecule compared to Avastin and according to GenenTech, the smaller molecule helps lower the systemic toxicity of the drug, thereby lowering the overall risks compared to Avastin. However, Lucentis costs approximately $1,600 per injection compared to less than $100 per injection for Avastin. Research has shown that Avastin and Lucentis to be equally effective in the treatment of POHS and AMD.