Retinitis overview

# Overview
Retinitis is inflammation of the retina in the eye. The disease may be classified according to the underlying cause for the disease. There are two major categories of underlying causes of retinitis, they are genetic disorders and infectious agents. The underlying cause for the disease may be established based on clinical presentation and manifestation of symptoms.Progression of the disease may be defined by the rate of cellular breakdown of cone and rod cells. Further progression is defined by the degradation of pigment epithelium as well as retinal vessel attenuation and dysfunction of the optic nerve. Infectious diseases may also be responsible as bacterial and viral infections may result in scarring and lesions across the retinal tissue.

# Historical Perspective
From a historical perspective, there is not much information available for retinitis. Although, biotechnology companies have begun to advance development and research on the topic, as ocular technology further develops.

# Classification
Retinitis may be classified according to the underlying cause for the disease. There are two major categories of underlying causes of retinitis, they are genetic disorders and infectious agents. The underlying cause for the disease may be established based on clinical presentation and manifestation of symptoms.

# Pathophysiology
Retinitis refers to the inflammation of the retina as a result of either genetic disorders or infectious diseases. Genetic disorders are often a due to an underlying defect in one of the 50 genes that are necessary for the proper creation of photoreceptor proteins.  Progression may therefore be defined by the rate of the cellular breakdown of cone and rod cells. Further progression is defined by the degradation of pigment epithelium as well as retinal vessel attenuation and dysfunction of the optic nerve. Infectious diseases may also be responsible as bacterial and viral infections may result in scarring and lesions across the retinal tissue.

# Causes
Retinitis may be caused by multiple infectious agents including cytomegalovirus, taxoplasmosis, tuberculosis, syphilis, and candida. Retinitis Pigmentosa is classified as a genetic eye disease which occurs as a result of an inherited defect. 

# Differentiating Retinitis from other Diseases
As retinitis manifests in a variety of clinical forms, differentiation must be established in accordance with the particular subtype. Retinitis caused by genetic defects such as retinitis pigmentosa must be differentiated from other diseases that cause visual acuity, cone-rod dystrophy, night blindness, and vision loss. Infectious agents that cause retinitis must be differentiated from other ocular diseases that may cause lesions and retinal scarring.

# Epidemiology and Demographics
The prevalence of retinitis pigmentosa is approximately one case per every 2500 to 7000 people.  Incidence has not drastically changed over the course of the past decade. However, the risk of contracting cytomegalovirus based retinitis within HIV patients has drastically been reduced with the introduction of HAART treatment. There is no specific race or ethnicity associated with infection, nor is it gender based. Diagnosis usually occurs during a patients childhood or early adulthood.

# Risk Factors
Multiple risk factors are associated with the potential manifestation of retinitis. The most common risk factor responsible for the manifestation of retinitis is linked to a variety of unmitigated, rare genetic disorders that are vertically inherited from parents to offspring.  Other mitigated risk factors include infectious agents such as cytomegalovirus, taxoplasmosis, tuberculosis, and candida. Cytomegalovirus remains the number one risk factor for developing a progressive form of retinitis within HIV infected patients.

# Natural History, Complications, and Prognosis
If left untreated, patients with retinitis may progress to develop limited vision, night blindness, and blindness. Common complications may vary according to the underlying cause of the disease. Retinal genetic disorders, such as retinitis pigmentosa, will often lead to highly restricted tunnel-like vision. Retinitis as a result of an infectious agent may imply far more serious complications including respiratory or central nervous system infections. The prognosis is usually good for individuals with retinitis resulting form an infectious agent. Most often the symptoms and complications will subside with proper treatment. Certain infections, such as tuberculosis and cytomegalovirus, require closer attention during and after treatment. Retinal genetic disorders, unfortunately, lack treatment. Thus individuals suffering from retinal genetic disorders, such as retinitis pigmentosa, will most likely experience mild to severe vision loss.

# History and Symptoms
The hallmark of retinitis is overall vision loss. A positive history of disturbances in color perception and night blindness is suggestive of retinitis.  Other symptoms of retinitis include the loss of peripheral vision and cone-rod dystrophy.  Infectious diseases may cause retinal hemorrhaging or retinal tissue lesions.

# Physical Examination
Physical signs associated with retinitis will vary according to the underlying condition responsible for the disease. Genetic defects will result in a genetic disorder known as Retinitis pigmentosa. The presentation of this disorder is primarily visible in the degradation of cone and rod cells. Infectious agents will present physical manifestations according to the underlying cause of infection. These clinical manifestations will range for yellowish infiltrates to inflammation and lesions localized to specific areas of the eye.

# Laboratory Findings
Due to the variability of causes associated with retinitis, there are a variety of tests available to diagnose the underlying cause. Genetic defects such as retinitis pigmentosa is primarily diagnosed with an electroretinogram.
Other underlying causes may be distinguished using a variety of testing procedures. These procedures are usually directly associated with the hypothesized condition causing retinitis. Many of the underlying conditions may range from fungal to bacterial and thus are tested accordingly.

# Imaging Findings
The optical coherence tomography (OCT) and the fundus autofluorescence (FAF) techniques are most often used when diagnosing a genetic variation of retinitis.  OCT may be used to acquire in situ retinal imaging for diagnosis of ocular diseases. FAF imaging is a non-invasive technique, dependent on the presence of lipofuscin pigments (lipofuscin is a by-product of lysosomes during the normal process of photoreceptor degradation.)

# Other Diagnostics
Other diagnostic studies include intraocular fluid analysis, blood tests, and cerebrospinal fluid testing.

# Medical Therapy
There is no single medical therapy to treat all types of retinitis. Due to the many underlying causes of retinitis, treatment is administered directly according to the underlying cause. These treatments will vary from vitamin therapy and preventative strategies to a long list of potential antimicrobial therapies.

# Surgery
Surgical intervention is not recommended for the management of retinitis. Cataract surgery has been hypothesized to produce positive results within populations suffering from retinitis pigmentosa. However no studies have proven this method to be significantly effective.

# Primary Prevention
There are no primary preventive measures available for retinitis that results from the genetic disorder, retinitis pigmentosa.
However, retinitis that results from cytomegalovirus may be prevented through upholding specific preventive strategies for cytomegalovirus. These strategies include avoiding the bodily fluids and items that might come in contact with infected individuals. Furthermore, similar strategies and precautions may be taken in order to prevent fungal, bacterial, and parasitic infections that could potentially result in retinitis.  

# Secondary Prevention
Secondary prevention strategies following retinitis depend on the underlying cause of the infection. Severity of genetic disorders may be lessened through vitamin therapy and reduced sunlight exposure. Meanwhile, prophylactic treatment may be prescribed to stunt the progression of viral, bacterial, fungal, and parasitic variations of retinitis.  

# Future or Investigational Therapies
Future and investigational therapies for retinitis include retinal prosthesis, bionic eyes, artificial vision, and retinal chips. A recently released apparatus, called Argus II, consists of a camera placed along a patients glasses' frame. The camera then sends information to a processing unit which is transferred to a microchip implanted in a patient's eye. Other therapies are focused on photoreceptor transplantation or activation of the induction of light sensitivity to retinal cells.