question: How come when people or animals lose their eyesight or die, their eyes turn that milky grey color?
comment: The cornea works really hard at keeping water out and stopping it from swelling. The cells on the inside of the cornea, the endothelial cells, do that. They pump water that seeps into the cornea out of the cornea, and into the eyeball. When we die, the pumps shut down and the water swells up the cornea creating the milky look.
passages: There are a variety of characteristics which indicate that an individual may have phacolytic glaucoma. Within older people, the lens of the eye may appear to be yellow and lose its transparency (becomes cloudy). Once the protein begins to seep into the lens, permanent damage to the lens may be caused as the precipitate in lens impairs vision.
   Section::::Work.:Recent studies.
  
  Provencio's research team has found that in albino mice, the amount of melanopsin protein in various retinal cells varies based on the environmental light conditions. In constant light conditions, melanopsin cell number did not increase. However, when these constant-light mice were exposed to light-dark schedules, there was regain of melanopsin cell number. This study shows that bouts of darkness or the order of light and dark periods may control the normal development of the melanopsin system.
   It is known to occur in Scotch Collies (smooth and rough collies), Shetland Sheepdogs, Australian Shepherds, Border Collies, Lancashire Heelers, and Nova Scotia Duck Tolling Retrievers. Frequency is high in Collies and Shetland Sheepdogs, and low in Border Collies and NSDTRs. In the United States, incidence in the genotype of collies has been estimated to be as high as 95 percent, with a phenotypic incidence of 80 to 85 percent.
  
  Section::::Pathogenesis.
   Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months, dilated pupils. Pupillary light reflexes are usually reduced but present; the slow phase mediated by melanopsin in retinal ganglion cells is retained. Other symptoms commonly seen are similar to those seen with Cushing's disease and include increased water consumption and urination, weight gain, confusion, restlessness, behavioral changes and lethargy. These symptoms may develop over a few months preceding the onset of SARDS. Clinical signs and disease progression vary markedly among individual animals, depending on the number and type of hormones that are increased, the degree of hormone elevation, and the age of the dog.
   Transparency is achieved through a lack of blood vessels, pigmentation, and keratin, and through the organization of the collagen fibers. The collagen fibers cross the full diameter of the cornea in a strictly parallel fashion and allow 99 percent of the light to pass through without scattering.
   More common than a complete absence of pigment cells is localized or incomplete hypopigmentation, resulting in irregular patches of white on an animal that otherwise has normal colouring and patterning. This partial leucism is known as a "pied" or "piebald" effect; and the ratio of white to normal-coloured skin can vary considerably not only between generations, but between different offspring from the same parents, and even between members of the same litter. This is notable in horses, cows, cats, dogs, the urban crow and the ball python but is also found in many other species.
   Ocular melanosis (OM) is a congenital disease of the eye which affects about 1 in every 5000 people and is a risk factor for uveal melanoma. In dogs is found almost exclusively in the Cairn Terrier, where until recently it was known as pigmentary glaucoma. The disease is caused by an increase of melanocytes in the iris, choroid, and surrounding structures. Overproduction of pigment by these cells can block the trabecular meshwork through which fluid drains from the eye. The increased fluid in the eye leads to increased pressure, which can lead to glaucoma. In humans, this is sometimes known as pigment dispersion syndrome.
   Phacolysis is evident, more commonly, within elderly people as a result of cataracts that have developed over time. There are other factors which contribute to the development of phacolysis in seniors. This is clearly indicated through the increase of intraocular pressure, which usually occurs when anterior flow faces obstruction of the anterior flow to the aqueous humor. Essentially, the eye requires a photosynthetic pigment which allows for light to become chemical energy. Within seniors this pigment overtime splits with the oxygen to thereby generate phacolysis.
  
  Section::::Treatment.
   BULLET::::- Hemoglobin-AGE levels are elevated in diabetic individuals and other AGE proteins have been shown in experimental models to accumulate with time, increasing from 5-50 fold over periods of 5–20 weeks in the retina, lens and renal cortex of diabetic rats. The inhibition of AGE formation reduced the extent of nephropathy in diabetic rats. Therefore, substances that inhibit AGE formation may limit the progression of disease and may offer new tools for therapeutic interventions in the therapy of AGE-mediated disease.
   Eye conditions which affect the Parson Russell Terrier include primary lens luxation, a heritable condition. This disease causes the zonular fibres to be abnormal and begin to disintegrate in affected dogs. The fibres support the lens of the eye, and their destruction can cause the lens to fall into the wrong location within the eye. If the lens falls into the anterior chamber of eyeball then a secondary glaucoma can occur, causing loss of vision. National kennel associations such as the Kennel Club (UK) publish DNA screening results on Parson Russell Terriers, broken down into three groups; clears, carriers, and affecteds.
   Sectoral heterochromia, usually sectoral hypochromia, is often seen in dogs, specifically in breeds with merle coats. These breeds include the Australian Shepherd, Border Collie, Collie, Shetland Sheepdog, Welsh Corgi, Pyrenean Shepherd, Mudi, Beauceron, Catahoula Cur, Dunker, Great Dane, Dachshund and Chihuahua. It also occurs in certain breeds that do not carry the merle trait, such as the Siberian Husky and rarely, Shih Tzu. There are example of cat breeds that have the condition such as Van cat.
  
  Section::::External links.
  
  BULLET::::- "Photograph of Radial Reddish Sunburst Pattern in Right Eye of Bluish Hazel Eyed Woman"
   BULLET::::- Pigmentary changes in the retina – In addition to the pigmented cells in the iris (the colored part of the eye), there are pigmented cells beneath the retina. As these cells break down and release their pigment, dark clumps of released pigment and later, areas that are less pigmented may appear
  
  BULLET::::- Exudative changes: hemorrhages in the eye, hard exudates, subretinal/sub-RPE/intraretinal fluid
   Controversies exist around eliminating this disorder from breeding Collies. Some veterinarians advocate only breeding dogs with no evidence of disease, but this would eliminate a large portion of potential breeding stock. Because of this, others recommend only breeding mildly affected dogs, but this would never completely eradicate the condition. Also, mild cases of choroidal hypoplasia may become pigmented and therefore undiagnosable by the age of three to seven months. If puppies are not checked for CEA before this happens, they may be mistaken for normal and bred as such. Checking for CEA by seven weeks of age can eliminate this possibility. Diagnosis is also difficult in dogs with coats of dilute color because lack of pigment in the choroid of these animals can be confused with choroidal hypoplasia. Also, because of the lack of choroidal pigment, mild choroidal hypoplasia is difficult to see, and therefore cases of CEA may be missed.
   White eyeshine occurs in many fish, especially walleye; blue eyeshine occurs in many mammals such as horses; green eyeshine occurs in mammals such as cats, dogs, and raccoons; and red eyeshine occurs in coyote, rodents, opossums and birds.
  
  Although human eyes lack a tapetum lucidum, they still exhibit a weak reflection from the fundus, as can be seen in photography with the red-eye effect and with near-infrared eyeshine. Another effect in humans and other animals that may resemble eyeshine is "leukocoria", which is a white shine indicative of abnormalities such as cataracts and cancers.
  
  Section::::Eyeshine.:In blue-eyed cats and dogs.
   Eye diseases are common in dogs. Cataracts, canine glaucoma, and entropion are seen in dogs. Canine-specific eye diseases include progressive retinal atrophy, Collie eye anomaly, sudden acquired retinal degeneration, and cherry eye. Injury to the eye can result in corneal ulcers.
  
  The frequency of bilateral glaucoma with a genetic base in purebred dogs is higher than in any species except humans. Cataracts in dogs either have a genetic base or can also be caused by diabetes. Nuclear sclerosis resembles a cataract but is actually a normal age-related change.
  
  Section::::Diseases.:Vestibular disease.
   Glaucoma often goes unnoticed in dogs until it is in a more severe state. There are rarely any symptoms in the early stages of the disease so regular eye checks by qualified veterinary professionals are important. Dogs will sometimes rub the eye if it is painful. An eye affected with glaucoma may be red, swollen, sore, or become clouded in appearance.
  
  Section::::Causes.
  
  There are three broad categories of causes of glaucoma: congenital, primary and secondary.
   Dr. David M. Maurice (1922-2002), an eye specialist and semi-retired adjunct professor at Columbia University, proposed that REM sleep was associated with oxygen supply to the cornea, and that aqueous humor, the liquid between cornea and iris, was stagnant if not stirred. Among the supportive evidences, he calculated that if aqueous humor was stagnant, oxygen from iris had to reach cornea by diffusion through aqueous humor, which was not sufficient. According to the theory, when the animal is awake, eye movement (or cool environmental temperature) enables the aqueous humor to circulate. When the animal is sleeping, REM provides the much-needed stir to aqueous humor. This theory is consistent with the observation that fetuses, as well as eye-sealed newborn animals, spend much time in REM sleep, and that during a normal sleep, a person's REM sleep episodes become progressively longer deeper into the night. However, owls have REM sleep, but do not move their head more than in non-REM sleep and is well known that owls' eyes are nearly immobile.
   A living person can look deathly pale. This can happen when circumstances make the blood escape from the surface of the skin, as in deep shock. Also heart failure ("insufficientia cordis") can make the face look grey; the person then also has blue lips. Skin can also look deathly pale as a result of vasoconstriction as part of the body's homeostatic systems in cold conditions, or if the skin is deficient in vitamin D, as seen in people who spend most of the time indoors, away from sunlight.
   The sclera, also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some elastic fiber. In humans, the whole sclera is white, contrasting with the coloured iris, but in other mammals the visible part of the sclera matches the colour of the iris, so the white part does not normally show. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. Many people with dark skin have naturally darkened sclerae, the result of melanin pigmentation.
   If left untreated, patients ultimately develop late sequel, which may include optic atrophy, retinal arterial narrowing, diffuse retinal pigment epithelial changes, and an abnormal electroretinogram. The late findings of this condition are often misinterpreted as unilateral retinitis pigmentosa.
  
  Section::::Cause.
   BULLET::::- The vascular tunic, also known as the "tunica vasculosa oculi" or the "uvea", is the middle vascularized layer which includes the iris, ciliary body, and choroid. The choroid contains blood vessels that supply the retinal cells with necessary oxygen and remove the waste products of respiration. The choroid gives the inner eye a dark color, which prevents disruptive reflections within the eye. The iris is seen rather than the cornea when looking straight in one's eye due to the latter's transparency, the pupil (central aperture of iris) is black because there is no light reflected out of the interior eye. If an ophthalmoscope is used, one can see the fundus, as well as vessels (which supply additional blood flow to the retina) especially those crossing the optic disk—the point where the optic nerve fibers depart from the eyeball—among others
   Dogs who are homozygous for the merle pattern gene often have visual and auditory deficits. These dogs are sometimes referred to as 'double merle' and sometimes incorrectly referred to as 'lethal white'. Ocular defects include microphthalmia, conditions causing increased ocular pressure, and colobomas, among others. Double merle dogs may be deaf or blind or both, and can carry ocular defects in blue or colored eyes. Currently no studies have been done to prove whether or not the merle gene affects the eyes, causing blindness.
  
  Section::::Health issues.:Auditory defects.
   Patients with retinitis pigmentosa have abnormal thinning of the RNFL which correlates with the severity of the disease. However the thickness of the RNFL also decreases with age and not visual acuity. The sparing of this layer is important in the treatment of the disease as it is the basis for connecting retinal prostheses to the optic nerve, or implanting stem cells that could regenerate the lost photoreceptors.
   The color of the fundus varies both between and within species. In one study of primates the retina is blue, green, yellow, orange, and red; only the human fundus (from a lightly pigmented blond person) is red. The major differences noted among the "higher" primate species were size and regularity of the border of macular area, size and shape of the optic disc, apparent 'texturing' of retina, and pigmentation of retina.
  
  Section::::Clinical significance.
   Within the retina, the accumulation of AGEs in the drusen and Bruch's membrane has been associated with age, and has also been observed at a higher level among patients with age-related macular degeneration. This is manifested by the thickening of the Bruch's membrane. Furthermore, it has been observed that AGE levels increase with age within the lamina cribrosa, and the products of the Maillard reaction have been observed there, as well.
  