Floaters are deposits of various size, shape, consistency, refractive index, and motility within the eye's vitreous humour, which is normally transparent. At a young age, the vitreous is transparent, but as one ages, imperfections gradually develop. The common type of floater, which is present in most persons' eyes, is due to degenerative changes of the vitreous humour. The perception of floaters is known as myodesopsia, or less commonly as myodaeopsia, myiodeopsia, or myiodesopsia. They are also called Muscae volitantes, or mouches volantes.
The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates. It is often referred to as the vitreous humor or simply "the vitreous".
Vitrectomy is surgery to remove some or all of the vitreous humor from the eye.
Bruch's membrane is the innermost layer of the choroid. It is also called the vitreous lamina, because of its glassy microscopic appearance. It is 2–4 μm thick.
A posterior vitreous detachment (PVD) is a condition of the eye in which the vitreous membrane separates from the retina. It refers to the separation of the posterior hyaloid membrane from the retina anywhere posterior to the vitreous base.
The posterior segment or posterior cavity is the back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve. The portion of the posterior segment visible during ophthalmoscopy is sometimes referred to as the posterior pole, or fundus. Some ophthalmologists specialize in the treatment and management of posterior segment disorders and diseases.
The inner limiting membrane is the boundary between the retina and the vitreous body, formed by astrocytes and the end feet of Müller cells. It is separated from the vitreous humor by a basal lamina.
Epiretinal membrane is a disease of the eye in response to changes in the vitreous humor or more rarely, diabetes. It is also called macular pucker. Sometimes, as a result of immune system response to protect the retina, cells converge in the macular area as the vitreous ages and pulls away in posterior vitreous detachment (PVD). PVD can create minor damage to the retina, stimulating exudate, inflammation, and leucocyte response. These cells can form a transparent layer gradually and, like all scar tissue, tighten to create tension on the retina which may bulge and pucker, or even cause swelling or macular edema. Often this results in distortions of vision that are clearly visible as bowing ←→ when looking at lines on chart paper within the macular area, or central 1.0 degree of visual arc. Usually it occurs in one eye first, and may cause binocular diplopia or double vision if the image from one eye is too different from the image of the other eye. The distortions can make objects look different in size, especially in the central portion of the visual field, creating a localized or field dependent aniseikonia that cannot be fully corrected optically with glasses. Partial correction often improves the binocular vision considerably though. In the young, these cells occasionally pull free and disintegrate on their own; but in the majority of sufferers the condition is permanent. The underlying photoreceptor cells, rod cells and cone cells, are usually not damaged unless the membrane becomes quite thick and hard; so usually there is no macular degeneration.
Hyaloid canal is a small transparent canal running through the vitreous body from the optic nerve disc to the lens. It is formed by an invagination of the hyaloid membrane, which encloses the vitreous body.
A macular hole is a small break in the macula, located in the center of the eye's light-sensitive tissue called the retina.
Intraocular hemorrhage is bleeding (hemorrhage) into the eyeball (oculus in Latin. It may be the result of physical trauma or medical illness. Severe hemorrhage, particularly when leading to rising pressure inside the eye, may lead to blindness.
Proliferative vitreoretinopathy (PVR) is a disease that develops as a complication of rhegmatogenous retinal detachment. PVR occurs in about 8–10% of patients undergoing primary retinal detachment surgery and prevents the successful surgical repair of rhegmatogenous retinal detachment. PVR can be treated with surgery to reattach the detached retina but the visual outcome of the surgery is very poor.
Distorted vision is a symptom with several different possible causes.
Diktyoma, or ciliary body medulloepithelioma, or teratoneuroma, is a rare tumor arising from primitive medullary epithelium in the ciliary body of the eye. Almost all diktyomas arise in the ciliary body, although, rarely, they may arise from the optic nerve head or retina.
Vitreous hemorrhage is the extravasation, or leakage, of blood into the areas in and around the vitreous humor of the eye. The vitreous humor is the clear gel that fills the space between the lens and the retina of the eye. A variety of conditions can result in blood leaking into the vitreous humor, which can cause impaired vision, floaters, and photopsia.
Vitreomacular adhesion (VMA) is a human medical condition where the vitreous gel of the human eye adheres to the retina in an abnormally strong manner. As the eye ages, it is common for the vitreous to separate from the retina. But if this separation is not complete, i.e. there is still an adhesion, this can create pulling forces on the retina that may result in subsequent loss or distortion of vision. The adhesion in of itself is not dangerous, but the resulting pathological vitreomacular traction (VMT) can cause severe ocular damage.
Taraprasad Das is an Indian ophthalmologist, who specializes in diseases of the retina and vitreous membrane. He is currently the Vice-Chairman of the L.V.Prasad Eye Institute. He is professor of ophthalmology at the Sun Yet-sen University of Medical Sciences in Guangzhou, China.
Globe rupture is an ophthalmologic condition when the integrity of the outer membranes of the eye are disrupted by blunt or penetrating trauma, usually resulting from a full-thickness injury to the cornea or sclera. It may also result from damage caused by chemicals such as strong acids or industrial chemicals such as Lewisite.
