Scientists are studying different populations and relationships to try to learn more about the disease. They have found associations with different groups but it is not yet clear what the underlying factors are and how they affect different peoples around the world.

- Glaucoma patients. While PEX and glaucoma are believed to be related, there are cases of persons with PEX without glaucoma, and persons with glaucoma without PEX. Generally, a person with PEX is considered as having a risk of developing glaucoma, and vice versa. One study suggested that the PEX was present in 12% of glaucoma patients. Another found that PEX was present in 6% of an "open-angle glaucoma" group. Pseudoexfoliation syndrome is considered to be the most common of identifiable causes of glaucoma. If PEX is diagnosed without glaucoma, there is a high risk of a patient subsequently developing glaucoma.

- Country and region. Prevalence of PEX varies by geography. In Europe, differing levels of PEX were found; 5% in England, 6% in Norway, 4% in Germany, 1% in Greece, and 6% in France. One contrary report suggested that levels of PEX were higher among Greek people. One study of a county in Minnesota found that the prevalence of PEX was 25.9 cases per 100,000 people. It is reportedly high in northern European countries such as Norway, Sweden and Finland, as well as among the Sami people of northern Europe, and high among Arabic populations, but relatively rare among African Americans and Eskimos. In southern Africa, prevalence was found to be 19% of patients in a glaucoma clinic attending to persons of the Bantu tribes.

- Race. It varies considerably according to race.

- Gender. It affects women more than men. One report was that women were three times more likely than men to develop PEX.

- Age. Older persons are more likely to develop PEX. And persons younger than 50 are highly unlikely to have PEX. A study in Norway found that the prevalence of PEX of persons aged 50–59 was 0.4% while it was 7.9% for persons aged 80–89 years. If a person is going to develop PEX, the average age in which this will happen is between 69 and 75 years, according to the Norwegian study. A second corroborating report suggested that it happens primarily to people 70 and older. While older people are more likely to develop PEX, it is not seen as a "normal" part of aging.

- Other diseases. Sometimes PEX is associated with the development of medical problems other than merely glaucoma. There are conflicting reports about whether PEX is associated with problems of the heart or brain; one study suggested no correlations while other studies found statistical links with Alzheimer's disease, senile dementia, cerebral atrophy, chronic cerebral ischemia, stroke, transient ischemic attacks, heart disease, and hearing loss.

The cause of pseudoexfoliation glaucoma is generally unknown.

PEX is generally believed to be a systemic disorder, possibly of the basement membrane of the eye. Researchers have noticed deposits of PEX material in various parts of the body, including in the skin, heart, lungs, liver, kidneys, and elsewhere. Nevertheless, what is puzzling is that PEX tends to happen in only one eye first, which scientists call "unilaterality", and in some cases, gradually afflicts the other eye, which is termed "bilaterality". According to this reasoning, if PEX were a systemic disorder, then both eyes should be affected at the same time, but they are not. There are contrasting reports about the extent and speed with which PEX moves from one eye to both eyes. According to one report, PEX develops in the second eye in 40% of cases. A contrasting report was that PEX can be found in both eyes in almost all situations if an electron microscope is used to examine the second eye, or if a biopsy of the conjunctiva was done, but that the extent of PEX is the second eye was much less than the first one. A different report suggested that two thirds of PEX patients had flakes in only one eye. In one long term study, patients with PEX in only one eye were studied, and it was found that over time, 13% progressed to having both eyes afflicted by PEX. Scientists believe that elevated levels of plasma homocysteine are a risk factor for cardiovascular disease, and two studies have found higher levels of plasma homocysteine in PEX patients, or elevated homocysteine concentrations in tear fluids produced by the eye.

There is speculation that PEX may be caused by oxidative damage and the presence of "free radicals", although the exact nature of how this might happen is still under study. Studies of PEX patients have found a decrease in the concentrations of ascorbic acid, increase in concentrations of malondialdehyde, and an increase in concentrations of 8-iso-prostaglandinF2a.

There is speculation that genetics may play a role in PEX. A predisposition to develop PEX later in life may be an inherited characteristic, according to one account. One report suggested the genetic component was "strong". One study performed in Iceland and Sweden has associated PEX with polymorphisms in gene LOXL1. A report suggested that a specific gene named LOXL1 which was a member of the family of enzymes which play a role in the linking of collagen and elastin inside cells. LOXL1 was responsible for "all the heritability" of PEX, according to one source. Two distinct mutations in which a single nucleotide was changed, or called a "single nucleotide polymorphism" or SNP, was discovered in Scandinavian populations and confirmed in other populations, and may be involved with the onset of PEX.

Researchers are investigating whether factors such as exposure to ultraviolet light, living in northern latitudes, or altitude influence the onset of PEX. One report suggested that climate was not a factor related to PEX. Another report suggested a possible link to sunlight as well as a possible autoimmune response, or possibly a virus.

Many people of East Asian descent are prone to developing angle closure glaucoma due to shallower anterior chamber depths, with the majority of cases of glaucoma in this population consisting of some form of angle closure. Higher rates of glaucoma have also been reported for Inuit populations, compared to white populations, in Canada and Greenland.

No clear evidence indicates vitamin deficiencies cause glaucoma in humans. It follows, then, that oral vitamin supplementation is not a recommended treatment for glaucoma. Caffeine increases intraocular pressure in those with glaucoma, but does not appear to affect normal individuals.

Of these, cataract is responsible for >65%, or more than 22 million cases of blindness, and glaucoma is responsible for 6 million cases.

Cataracts: is the congenital and pediatric pathology that describes the greying or opacity of the crystalline lens, which is most commonly caused by intrauterine infections, metabolic disorders, and genetically transmitted syndromes. Cataracts are the leading cause of child and adult blindness that doubles in prevalence with every ten years after the age of 40. Consequently, today cataracts are more common among adults than in children. That is, people face higher chances of developing cataracts as they age. Nonetheless, cataracts tend to have a greater financial and emotional toll upon children as they must undergo expensive diagnosis, long term rehabilitation, and visual assistance. Also, according to the Saudi Journal for Health Sciences, sometimes patients experience irreversible amblyopia after pediatric cataract surgery because the cataracts prevented the normal maturation of vision prior to operation. Despite the great progress in treatment, cataracts remain a global problem in both economically developed and developing countries. At present, with the variant outcomes as well as the unequal access to cataract surgery, the best way to reduce the risk of developing cataracts is to avoid smoking and extensive exposure to sun light (i.e. UV-B rays).

Blindness can occur in combination with such conditions as intellectual disability, autism spectrum disorders, cerebral palsy, hearing impairments, and epilepsy. Blindness in combination with hearing loss is known as deafblindness.

It has been estimated that over half of completely blind people have non-24-hour sleep–wake disorder, a condition in which a person's circadian rhythm, normally slightly longer than 24 hours, is not entrained (synchronized) to the light/dark cycle.

Vitamin A supplementation plays an important role, specifically vitamin A deficiency is a top causes of preventable childhood blindness. Though in measles cases, the administration of the vitamin to offset visual impairment has not been proven effective, as of yet.

is a program launched by the International Agency for the Prevention of Blindness (IAPB) and is supported by the WHO in 1999 that has made controlling blindness in children a high priority.

According to recent research not a single theory is able to explain the cause fully. However current plausible theories include infection with "Toxoplasma gondii", Herpes simplex virus, Rubella, neurogenic causes, and autoimmune pathology.

In the United States, the incidence of primary congenital glaucoma is about one in 10,000 live births. Worldwide, the incidence ranges from a low of 1:22,000 in Northern Ireland to a high of 1:2,500 in Saudi Arabia and 1:1,250 in Romania. In about two-thirds of cases, it is bilateral. The distribution between males and females varies with geography. In North America and Europe it is more common in boys, whereas in Japan it is more common in girls.

- Congenital glaucoma

- Incidence: one in every 10000-15000 live births.

- Bilateral in up to 80% of cases.

- Most cases are sporadic (90%). However, in the remaining 10% there appears to be a strong familial component.

Fuchs heterochromic iridocyclitis (FHI) is a chronic unilateral uveitis appearing with the triad of heterochromia, predisposition to cataract and glaucoma, and keratitic precipitates on the posterior corneal surface. Patients are often asymptomatic and the disease is often discovered through investigation of the cause of the heterochromia or cataract. Neovascularisation (growth of new abnormal vessels) is possible and any eye surgery, such as cataract surgery, can cause bleeding from the fragile vessels in the atrophic iris causing accumulation of blood in anterior chamber of the eye, also known as hyphema.

Pigment dispersion syndrome (PDS) is an affliction of the eye that can lead to a form of glaucoma known as pigmentary glaucoma. It takes place when pigment cells slough off from the back of the iris and float around in the aqueous humor. Over time, these pigment cells can accumulate in the anterior chamber in such a way that it can begin to clog the trabecular meshwork (the major site of aqueous humour drainage), which can in turn prevent the aqueous humour from draining and therefore increases the pressure inside the eye. With PDS, the intraocular pressure tends to spike at times and then can return to normal. Exercise has been shown to contribute to spikes in pressure as well. When the pressure is great enough to cause damage to the optic nerve, this is called pigmentary glaucoma. As with all types of glaucoma, when damage happens to the optic nerve fibers, the vision loss that occurs is irreversible and painless.

This condition is rare, but occurs most often in Caucasians, particularly men, and the age of onset is relatively low: mid 20s to 40s. As the crystalline lens hardens with age, the lens zonules pull away from the iris and the syndrome lessens and stops. Most sufferers are nearsighted.

There is no cure yet, but pigmentary glaucoma can be managed with eye drops or treated with simple surgeries. One of the surgeries is the YAG laser procedure in which a laser is used to break up the pigment clogs, and reduce pressure. If caught early and treated, chances of glaucoma are greatly reduced. Sufferers are often advised not to engage in high-impact sports such as long-distance running or martial arts, as strong impacts can cause more pigment cells to slough off.

A 2016 Cochrane Review sought to determine the effectiveness of YAG laser iridotomy versus no laser iridotomy for pigment dispersion syndrome and pigmentary glaucoma, in 195 participants, across five studies. No clear benefits in preventing loss of visual field were found for eyes treated with peripheral laser iridotomy. There was weak evidence suggesting that laser iridotomy could be more effective in lowering intraocular pressure in eyes versus no treatment.

Keratopathy is common in older people. Keratopathy occurs after cataract surgery, its incidence has decreased since the advent of intraoperative viscoelastic agents that protect the endothelium.

In the early stages, there are a few treatment options. Laser surgery or cryotherapy (freezing) can be used to destroy the abnormal blood vessels, thus halting progression of the disease. However, if the leaking blood vessels are clustered around the optic nerve, this treatment is not recommended as accidental damage to the nerve itself can result in permanent blindness. Although Coats' disease tends to progress to visual loss, it may stop progressing on its own, either temporarily or permanently. Cases have been documented in which the condition even reverses itself. However, once total retinal detachment occurs, sight loss is permanent in most cases. Removal of the eye (enucleation) is an option if pain or further complications arise.

Coats' disease, (also known as exudative retinitis or retinal telangiectasis, sometimes spelled Coates' disease), is a rare congenital, nonhereditary eye disorder, causing full or partial blindness, characterized by abnormal development of blood vessels behind the retina. Coats' disease can also fall under glaucoma.

It can have a similar presentation to that of retinoblastoma.

Causes of photophobia relating directly to the eye itself include:

- Achromatopsia

- Aniridia

- Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.

- Aphakia (absence of the lens of the eye)

- Blepharitis

- Buphthalmos (abnormally narrow angle between the cornea and iris)

- Cataracts

- Coloboma

- Cone dystrophy

- Congenital abnormalities of the eye

- Viral conjunctivitis ("pink eye")

- Corneal abrasion

- Corneal dystrophy

- Corneal ulcer

- Disruption of the corneal epithelium, such as that caused by a corneal foreign body or keratitis

- Ectopia lentis

- Endophthalmitis

- Eye trauma caused by disease, injury, or infection such as chalazion, episcleritis, glaucoma, keratoconus, or optic nerve hypoplasia

- Hydrophthalmos, or congenital glaucoma

- Iritis

- The drug isotretinoin (Accutane/Roaccutane) has been associated with photophobia

- Optic neuritis

- Pigment dispersion syndrome

- Pupillary dilation (naturally or chemically induced)

- Retinal detachment

- Scarring of the cornea or sclera

- Uveitis

There are many causes of blurred vision:

- Use of atropine or other anticholinergics

- Presbyopia—Difficulty focusing on objects that are close. Common in the elderly. (Accommodation tends to decrease with age.)

- Cataracts—Cloudiness over the eye's lens, causing poor night-time vision, halos around lights, and sensitivity to glare. Daytime vision is eventually affected. Common in the elderly.

- Glaucoma—Increased pressure in the eye, causing poor night vision, blind spots, and loss of vision to either side. A major cause of blindness. Glaucoma can happen gradually or suddenly—if sudden, it is a medical emergency.

- Diabetes—Poorly controlled blood sugar can lead to temporary swelling of the lens of the eye, resulting in blurred vision. While it resolves if blood sugar control is reestablished, it is believed repeated occurrences promote the formation of cataracts (which are not temporary).

- Diabetic retinopathy—This complication of diabetes can lead to bleeding into the retina. Another common cause of blindness.

- Hypervitaminosis A—Excess consumption of vitamin A can cause blurred vision.

- Macular degeneration—Loss of central vision, blurred vision (especially while reading), distorted vision (like seeing wavy lines), and colors appearing faded. The most common cause of blindness in people over age 60.

- Eye infection, inflammation, or injury.

- Sjögren's syndrome, a chronic autoimmune inflammatory disease that destroys moisture producing glands, including lacrimal (tear)

- Floaters—Tiny particles drifting across the eye. Although often brief and harmless, they may be a sign of retinal detachment.

- Retinal detachment—Symptoms include floaters, flashes of light across your visual field, or a sensation of a shade or curtain hanging on one side of your visual field.

- Optic neuritis—Inflammation of the optic nerve from infection or multiple sclerosis. You may have pain when you move your eye or touch it through the eyelid.

- Stroke or transient ischemic attack

- Brain tumor

- Toxocara—A parasitic roundworm that can cause blurred vision

- Bleeding into the eye

- Temporal arteritis—Inflammation of an artery in the brain that supplies blood to the optic nerve.

- Migraine headaches—Spots of light, halos, or zigzag patterns are common symptoms prior to the start of the headache. A retinal migraine is when you have only visual symptoms without a headache.

- Myopia—Blurred vision may be a systemic sign of local anaesthetic toxicity

- Reduced blinking—Lid closure that occurs too infrequently often leads to irregularities of the tear film due to prolonged evaporation, thus resulting in disruptions in visual perception.

- Carbon monoxide poisoning—Reduced oxygen delivery can effect many areas of the body including vision. Other symptoms caused by CO include vertigo, hallucination and sensitivity to light.

Some pedigrees suggest inherited primary congenital is autosomal dominant but three major autosomal recessive loci have been identified:

- GLC3A – on chromosome 2 (2p21)

- GLC3B – on chromosome 1 (1p36)

- GLC3C – on chromosome 14 (14q24.3)

It is the name given to the localised bulge in limbal area, lined by the root of the iris. It results due to ectasia of weak scar tissue formed at the limbus, following healing of a perforating injury or a peripheral corneal ulcer. There may be associated secondary angle closure glaucoma, may cause progression of the bulge if not treated. Defective vision occurs due to marked corneal astigmatism. Treatment consists of localised staphylectomy under heavy doses of oral steroids.

Neurological causes for photophobia include:

- Autism spectrum disorders

- Chiari malformation

- Occipital Neuralgia

- Dyslexia

- Encephalitis including Myalgic encephalomyelitis aka Chronic fatigue syndrome

- Meningitis

- Trigeminal disturbance causes central sensitization (hence, multiple other associated hypersensitivities. Causes can be bad bite, infected tooth, etc.

- Subarachnoid haemorrhage

- Tumor of the posterior cranial fossa

As the name implies, it is the bulge of weak sclera lined by ciliary body, which occurs about 2–3 mm away from the limbus. Its common causes are thinning of sclera following perforating injury, scleritis & absolute glaucoma.

it is part of anterior staphyloma

The disease is chronic and often progresses slowly. Prognosis is generally poor when associated with glaucoma [1,2].

Aphakia is the absence of the lens of the eye, due to surgical removal, a perforating wound or ulcer, or congenital anomaly. It causes a loss of accommodation, far sightedness (hyperopia), and a deep anterior chamber. Complications include detachment of the vitreous or retina, and glaucoma.

Babies are rarely born with aphakia. Occurrence most often results from surgery to remove congenital cataract (clouding of the eye's lens, which can block light from entering the eye and focusing clearly). Congenital cataracts usually develop as a result of infection of the fetus or genetic reasons. It is often difficult to identify the exact cause of these cataracts, especially if only one eye is affected.

People with aphakia have relatively small pupils and their pupils dilate to a lesser degree.

Iridocorneal Endothelial (ICE) syndromes are a spectrum of diseases characteriezed by slowly progressive abnormalities of the corneal endothelium and features including corneal edema, iris distortion, and secondary angle-closure glaucoma. [1,2,4] ICE syndromes are predominantly unilateral and nonhereditary [1,2,4]. The condition occurs in predominantly middle-aged women [1,3,4].

Untreated glaucoma leads to total blindness. Surgical treatment is required. Presently-utilized surgical procedures include goniotomy, trabeculotomy, or trabeculectomy.