DEFINITION
Floaters are deposits of various size, shape, consistency, refractive index , and motility within the eye's vitreous humour, which is normally transparent. The perception of floaters is known as myodesopsia, or less commonly as myiodeopsia, myiodesopsia, or myodeopsia. Floaters are visible because of the shadows they cast on the retina or their refraction of the light that passes through them, and can appear alone or together with several others in one's field of vision.
EPIDEMIOLOGY
Floaters have been reported in patients as young as 9.They may be of embryonic origin or acquired due to degenerative changes of the vitreous humour or retina. However, floaters in teenage patients and young adults are usually harder to treat. For people in this age group, the floater that is seen usually looks like a kind of crystal (translucent) worm/web/cell. However floaters are extremely common in adults with almost everyone over the age of 70 being affected by it. The period between 50 and 75 years is the period whick this occurs varies.
SYNTOMS
• Floaters cause little ‘’cobwebs’’ or specks that float about in field of vision. These stains are small, dark, shadowy shapes that can look like spots, threated-like strands or squiggly lines. They moves as the eyes move and seem to dart away when you try to look directly. They do not follow the eye movements precisely, and usually drift when the eye stops moving.
• These mobile bodies appear in a particularly clear way when the affected turns to look towards light and bright surfaces (such as white walls and the blue sky).
• The patient has the feeling of seeing them on the eye surface, in reality these objects are floating inside the vitreous and their perception is due to the projection on the retina (the ‘’protosensitive film’’ on the eye).
• The vitreal gel that fills the eyeball sometimes exercises a traction on the retina. This causes the appearance of flashes in absence of a true luminous stimulus. An often reported symptom is indeed the appearance of brief luminous flashes when moving the eyes quickly on the horizontal axis in condition of darkness. The same feeling is experienced when a person compresses the eye and sees ‘’stars’’.
• In connection with floaters the patient sometimes could show other pathologies like Tinnitus. Tinnitus is an auditory pathology . it is the perception of sound within the human ear in the absence of corresponding external sound. Tinnitus is generally connected with the presence of flashes in floaters.
CAUSES and RISK FACTOR
Primary Causes
• VITREOUS SYNERESIS
The most common cause of floaters is shrinkage of the vitreous humour: this gel-like substance consists of 99% water and 1% solid elements. The solid portion consists of a network of collagen fibrils and hyaluronic acid, with the latter retaining water molecules. There are also present peripheral cells (hyalocytes), inorganic salts, sugar and ascorbic acid. The collagen breaks down into fibrils, which ultimately are the floaters that plague the patient. Floaters caused in this way tend to be few in number and of a linear form;
• Posterior vitreous detachments and retinal detachments
In time, the liquefied vitreous body loses support and its framework contracts. During this detachment, the shrinking vitreous can stimulate the retina mechanically, causing the patient to see random flashes across the visual field, sometimes referred to as "flashers", a symptom more formally referred to as photopsia. As a complication, part of the retina might be torn off by the departing vitreous body, in a process known as retinal detachment: retinal detachment requires immediate medical attention, as it can easily cause blindness;
• Regression of the hyaloids artery during pregnancy
The hyaloid artery , an artery running through the vitreous humor during the fetal stage of development, regresses in the third trimester of pregnancy. Its disintegration can sometimes leave cell metter.
Secondary causes
• Cystoid macular edema and asteroid hyalosis. The latter is an anomaly of the vitreous humour, whereby calcium clumps attach themselves to the collagen network. The bodies that are formed in this way move slightly with eye movement, but then return to their fixed position;
• Sometimes the appearance of floaters has to be attributed to dark specks in the tear film of the eye. Technically, these are not floaters, but they do look the same from the viewpoint of the patient.
• Patients with retinal tears may experience floaters if red blood cells are released from leaky blod vassels, and those with a posterior uveitis or vitritis, as in toxoplasmosis, may experience multiple floaters and decreased vision due to the accumulation of white blood cells in the vitreous humour.
DIAGNOSIS
Standard vision tests like the Snellen visual visual acuity measurement, which measures your vision as 20/20, etc, are unable to qualify floaters and how the disability interferes with day-to-day functioning and overall quality of life.
Floaters are often readily observed by an ophthalmologist or an optometrist with the use of an ophthalmoscope or slit lamp. To dilate the pupils , the physician first makes sure to record papillary size and light responses, then instills drops, usually 1 drop each of a short-acting α-adrenergic agonist (eg 2,5%phenylephrine) and a cyclopegic (eg, 1% tropicamide or 1% cyclopentolate). The pupils are fully dilated about 20 minutes after these drops are instilled. However, if the floater is near the retina, it may not be visible to the observer even if it appears large to the sufferer.
Increasing background illumination or using a pinhole to effectively decrease pupil diameter may allow a person to obtain a better view of his or her own floaters. The head may be tilted in such a way that one of the floaters drifts towards the central axis of the eye. In the sharpened image the fibrous elements are more conspicuous.
The presence of retinal tears with new onset of floaters was surprisingly high (14%; 95% confidence interval, 12%-16%) as reported in a metaanalysis published as part of the Rational Clinical Examination Series in the Journal of the American Medical Association. Patients with new onset flashes and/or floaters, especially when associated with visual loss or restriction in the visual field, should seek more urgent ophthalmologic evaluation.
TREATMENT
Most commonly, there is no treatment recommended but there are 2 important mechanic treatments:
• Vitrectomy may be successful in treating more severe cases; however, the procedure is typically not warranted in those with lesser symptoms due to the potential for complications to include cataracts, retinal detachment, and severe infection. The technique usually involves making three openings through the part of the sclera known as the pars plana. Of these small gauge instruments, one is an infusion port to resupply a saline solution and maintain the pressure of the eye, the second is a fiber optic light source, and the third is a vitrector. The vitrector has a reciprocating cutting tip attached to a suction device. This design reduces traction on the retina via the vitreous material. A variant sutureless, self-sealing technique is sometimes used.
• Laser vitreolysis: In this procedure an ophthalmic laser: (usually an Yttrium aluminium garnet "YAG" laser) is focused onto the floater and in a series of brief bursts, the laser vaporizes and lyses (cuts) the collagen strands of the floater. Laser treatment is not widely practiced and is only performed by very few specialists in the world. It is an outpatient process, which is much less invasive to the eye than a vitrectomy, with potentially fewer side effects.
