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Optic neuritis describes any condition that causes inflammation of the optic nerve; it may be associated with demyelinating diseases, or infectious or inflammatory processes.
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision. As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon. Onset of symptoms is generally gradual and often begins in childhood.
The National Eye Institute (NEI) is part of the U.S. National Institutes of Health (NIH), an agency of the U.S. Department of Health and Human Services. The mission of NEI is "to eliminate vision loss and improve quality of life through vision research." NEI consists of two major branches for research: an extramural branch that funds studies outside NIH and an intramural branch that funds research on the NIH campus in Bethesda, Maryland. Most of the NEI budget funds extramural research.
Orthoptics is a profession allied to the eye care profession. Orthoptists are the experts in diagnosing and treating defects in eye movements and problems with how the eyes work together, called binocular vision. These can be caused by issues with the muscles around the eyes or defects in the nerves enabling the brain to communicate with the eyes. Orthoptists are responsible for the diagnosis and non-surgical management of strabismus (cross-eyed), amblyopia and eye movement disorders. The word orthoptics comes from the Greek words ὀρθός orthos, "straight" and ὀπτικός optikοs, "relating to sight" and much of the practice of orthoptists concerns disorders of binocular vision and defects of eye movement. Orthoptists are trained professionals who specialize in orthoptic treatment, such as eye patches, eye exercises, prisms or glasses. They commonly work with paediatric patients and also adult patients with neurological conditions such as stroke, brain tumours or multiple sclerosis. With specific training, in some countries orthoptists may be involved in monitoring of some forms of eye disease, such as glaucoma, cataract screening and diabetic retinopathy.
Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom, photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical sensitivity of the eyes, though the term is sometimes additionally applied to abnormal or irrational fear of light, such as heliophobia. The term photophobia comes from the Greek φῶς (phōs), meaning "light", and φόβος (phóbos), meaning "fear".
Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye. It results in decreased vision in an eye that typically appears normal in other aspects. Amblyopia is the most common cause of decreased vision in a single eye among children and younger adults.
This is a partial list of human eye diseases and disorders.
The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”.
Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often voluntary. However, when occurring involuntarily, it results from impaired function of the extraocular muscles, where both eyes are still functional, but they cannot turn to target the desired object. Problems with these muscles may be due to mechanical problems, disorders of the neuromuscular junction, disorders of the cranial nerves that innervate the muscles, and occasionally disorders involving the supranuclear oculomotor pathways or ingestion of toxins.
Amaurosis is vision loss or weakness that occurs without an apparent lesion affecting the eye. It may result from either a medical condition or excess acceleration, as in flight. The term is the same as the Latin gutta serena, which means, in Latin, clear drop. Gutta serena is a condition of partial or complete blindness with a transparent, clear pupil. This term contrasts with suffusio nigra which means, in Latin, dark suffusion, indicating partial or complete blindness with a dark pupil, e.g., a cataract. Milton, already totally blind for twelve years by the time he published Paradise Lost, refers to these terms in Book 3, lines 25–26.
Vision therapy (VT), or behavioral optometry, is an umbrella term for alternative medicine treatments using eye exercises, based around the pseudoscientific claim that vision problems are the true underlying cause of learning difficulties, particularly in children. Vision therapy has not been shown to be effective using scientific studies, except for helping with convergence insufficiency. Most claims—for example that the therapy can address neurological, educational, and spatial difficulties—lack supporting evidence. Neither the American Academy of Pediatrics nor the American Academy of Ophthalmology support the use of vision therapy.
A relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil, is a medical sign observed during the swinging-flashlight test whereupon the patient's pupils dilate when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.
Dilated fundus examination (DFE) is a diagnostic procedure that uses mydriatic eye drops to dilate or enlarge the pupil in order to obtain a better view of the fundus of the eye. Once the pupil is dilated, examiners use ophthalmoscopy to view the eye's interior, which makes it easier to assess the retina, optic nerve head, blood vessels, and other important features. DFE has been found to be a more effective method for evaluating eye health when compared to non-dilated examination, and is the best method of evaluating structures behind the iris. It is frequently performed by ophthalmologists and optometrists as part of an eye examination.
Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain.
Blurred vision is an ocular symptom where vision becomes less precise and there is added difficulty to resolve fine details.
Optic papillitis is a specific type of optic neuritis. Inflammation of the optic nerve head is called "papillitis" or "intraocular optic neuritis"; inflammation of the orbital portion of the nerve is called "retrobulbar optic neuritis" or "orbital optic neuritis". It is often associated with substantial losses in visual fields, pain on moving the globe, and sensitivity to light pressure on the globe. It is often an early sign of multiple sclerosis.
Occult macular dystrophy (OMD) is a rare inherited degradation of the retina, characterized by progressive loss of function in the most sensitive part of the central retina (macula), the location of the highest concentration of light-sensitive cells (photoreceptors) but presenting no visible abnormality. "Occult" refers to the degradation in the fundus being difficult to discern. The disorder is called "dystrophy" instead of "degradation" to distinguish its genetic origin from other causes, such as age. OMD was first reported by Y. Miyake et al. in 1989.
Corneal opacification is a term used when the human cornea loses its transparency. The term corneal opacity is used particularly for the loss of transparency of cornea due to scarring. Transparency of the cornea is dependent on the uniform diameter and the regular spacing and arrangement of the collagen fibrils within the stroma. Alterations in the spacing of collagen fibrils in a variety of conditions including corneal edema, scars, and macular corneal dystrophy is clinically manifested as corneal opacity. The term corneal blindness is commonly used to describe blindness due to corneal opacity.
The visual pathway consists of structures that carry visual information from the retina to the brain. Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way:
Retina→Optic nerve→Optic chiasma →Optic tract→Lateral geniculate body→Optic radiation→Primary visual cortex
References
- 1 2 Dhanji, Shanil; Lawlor, Mitchell (April 2017). "Functional visual loss". Current Opinion in Neurology. 30 (2): 200–205. doi:10.1097/WCO.0000000000000423. ISSN 1350-7540. PMID 28141741. S2CID 40337683. Archived from the original on 2023-04-20. Retrieved 2023-04-20.
- 1 2 3 4 "Functional Visual Loss - EyeWiki". eyewiki.aao.org. Archived from the original on 2023-04-20. Retrieved 2023-04-20.
- 1 2 "Functional Visual Loss". webeye.ophth.uiowa.edu. Archived from the original on 2023-07-04. Retrieved 2023-04-20.
- 1 2 Chen, Celia S.; Lee, Andrew W.; Karagiannis, Arthur; Crompton, John L.; Selva, Dinesh (1 January 2007). "Practical clinical approaches to functional visual loss". Journal of Clinical Neuroscience. 14 (1): 1–7. doi:10.1016/j.jocn.2006.03.002. ISSN 0967-5868. PMID 16730991. S2CID 6607292. Archived from the original on 20 April 2023. Retrieved 20 April 2023.
- ↑ Themes, U. F. O. (26 December 2019). "Functional (Nonorganic) Visual Loss". Ento Key. Archived from the original on 20 April 2023. Retrieved 20 April 2023.
- ↑ "Facts About Amblyopia". National Eye Institute. September 2013. Archived from the original on 27 July 2016. Retrieved 27 July 2016.
- ↑ "Dictionary of Eye Terminology". Archived from the original on 2017-08-03. Retrieved 2005-10-13.
{{cite web}}: More than one of|archivedate=and|archive-date=specified (help); More than one of|archiveurl=and|archive-url=specified (help) - 1 2 Khurana, A. K. (2019). Comprehensive ophthalmology (Seventh ed.). New Delhi. p. 344. ISBN 9789352706860.
{{cite book}}: CS1 maint: location missing publisher (link) - ↑ "Cone Dystrophy - Symptoms, Causes, Treatment | NORD". rarediseases.org. Archived from the original on 2023-04-20. Retrieved 2023-04-20.