Retinitis pathophysiology
|
Retinitis Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Retinitis pathophysiology On the Web |
|
American Roentgen Ray Society Images of Retinitis pathophysiology |
|
Risk calculators and risk factors for Retinitis pathophysiology |
Overview
Pathophysiology
Genetic Disorders
Retinitis Pigmentosa
- Retinitis pigmentosa is an umbrella term for multiple genetic, retinal disorders.
- Retinal genetic disorders include; night blindness, visual acuity, a fundus appearance, posterior subscapular cataracts, vitreous particle formation, sector retinitis, and pregnancy based retinitis. [1]
- The disease is a result of genetic defects in one of 50 genes required for the proper creation of photoreceptor proteins. [2]
- Generally the genetic disorder is linked to the inheritance of a recessive gene contributed by both parents. [3]
- Other cases have been linked to the inheritance of a dominant gene, defects of the X chromosome, and newly formed mutations caused by diseases.
- Progression of RP causes photoreceptor, cellular breakdown, both rods and cones.
- Ultimately, the progressive breakdown of photoreceptors leads to restricted vision or permanent loss of vision. [3]
Night blindness, Visual acuity, and Fundus appearance
- Night blindness results from the loss of rod function in the early portion of the clinical course.
- Visual acuity refers to the loss of central acuity correlating to severity of the disease's progression.
- Central acuity has been connected to the macular lesions present in the early clinical course of the disease.
- A fundus appearance often refers to the clinical stage.
- Fundus appearance in earlier stages include defective rod responses.
- Progression of retinitis will result in the narrowing of arteriolar portion of the fundus, accompanied by intraretinal pigmentation, and disturbances, often degradation pigments in the pigment epithelium.
- Pigment degradation in the pigment epithelium is an indicator of further degeneration of photoreceptors. This interruption will often manifest in clumping of melanin in odd, coarse configurations.
- Further degradation will result in retinal vessel attenuation and dysfunction of the optic nerve. [1]
Posterior subscapular cataracts, Vitreous particle formation, Sector retinitis, and Pregnancy based retinitis
- Progression of retinitis pigmentosa induces changes in the visual axis of the posterior lens cortex.
- These changes are often described as a yellowish crystalline change, accompanied by colorless, dust-like manifestations.
- Macrophage cells, pigment epithelium, uveal melanocytes, and free melanin pigment granules will mass in the area of dysfunction.
- Other manifestations include pigment epithelial degradation in the form of retinitis punctata albescens and the dysfunction of the optic nerve.
- Severe progression is commonly described as Coats-like disease; a severe case of degradation within the telangiectactic vessels. Much of which is attributed to an abnormal amount of lipid deposition in the retina.
- The progression of degradation may be attributed to pathogenic types of CRB1.
- Sector retinitis pigmentosa is often linked to pathogenic variants in the p.Pro 23His of RHO as well as X-linked, heterozygous females.
- These issues will manifest in specific quadrants of the fundus.
- Pregnant women who suffer from retinitis pigmentosa may experience worsened symptoms as physiological changes may occur within the lens and the cornea. [1]
Infectious Agents
Cytomegalovirus
- Retinitis, caused by cytomegalovirus (CMV), involves the infection of all layers of the retinal tissue.
- Spread of the the infection will occur at approximately 24 nanometers per day.
- Primarily infected areas include the RPE and the subjacent choroid.
- Infection will consist of a vast amount of cellular necrosis across the retina; with the enlargement of infected cells, evidently hosting viral inclusions.
- CMV retinitis, post-treatment, will commonly persist on the previously scarred, retinal tissue.
- Progression of infection may result in the development of small holes across previously scarred and healed tissue.
- Formation of these tiny holes may result in rhegmatogenous retinal detachments. [4]
Syphilis
- Retinitis resulting from a syphilitic infection is commonly referred to as a ocular syphilis.
- The infection persists as syphilitic spirochetes, Treponema pallidum, invade or cause allergic reactions within the surrounding tissue.
Endogenous Fungal Infections
- Two types of retina infections may occur depending on a mode of fungal infection. These two types our outlined as endogenous or exogenous.
- Endogenous fungal retinitis is primarily a result of a disseminated fungal infection.
- Exogenous fungal infections primarily occur as a result of a recent event such as physical injury or surgery.
- Exogenous fungal infections are usually a result of Candidal retinitis. An infection commonly associated with candida chorioretinitis.
- Candidas chorioretinitis is typically caused by the species Candida albicans.
Tuberculosis
- Extrapulmonary clinical manifestations of tuberculosis include intraocular caseating granulomas.
- Infection of the retina is associated with the spread of the tuberculosis causing bacterial agents.
- Common presentation of tuberculosis in the retina appears as multiple choroidal tubercles.
- These tubercles are best defined as minor nodules with a grayish appearance.
Toxoplasmosis
- Toxoplasma gondii is a parasitic agent found in contaminated meat and egg products.
- Persistence occurs within the vacuoles of cells found within tissues throughout the host.
- Rupturing of tissue cysts with host cells may lead disease resulting in retinitis. This occurrence is mostly common within individuals who were previously immuno-compromised.
References
- ↑ 1.0 1.1 1.2 GeneReviews. Retinitis Pigmentosa Overview. 2013; Abigail T Fahim, MD, PhD, Stephen P Daiger, PhD, and Richard G Weleber, MD, DABMG, FACMG. http://www.ncbi.nlm.nih.gov/books/NBK1417/ Accessed April 12, 2016.
- ↑ Retinitis Pigmentosa. U.S. National Library of Medicine. https://www.genome.gov/13514348
- ↑ 3.0 3.1 Retinitis Pigmentosa. U.S. National Library of Medicine. https://www.nlm.nih.gov/medlineplus/ency/article/001029.htm
- ↑ American Academy of Ophthalmology. Pathophysiology of CMV Retinitis. http://www.aao.org/focalpointssnippetdetail.aspx?id=bc891841-b847-4210-a66b-2bb28d1ef1bf. Accessed April 12, 2016.