Pseudoexfoliation syndrome

Signs and symptoms

Patients may have no specific symptoms. In some cases, patients may complain of lessened visual acuity or changes in their perceived visual field, and such changes may be secondary to or different from symptoms normally associated with cataracts or glaucoma.

PEX is characterized by tiny microscopic white or grey The abnormal The flakes are widespread. One report suggested that the granular flakes were from abnormalities of the basement membrane in epithelial cells, and that they were distributed widely throughout the body and not just within structures of the eye. There is some research suggesting that the material may be produced in the iris pigment epithelium, ciliary epithelium, or the peripheral anterior lens epithelium. Histological staining with hematoxylin-eosin highlighted the material's fibrillar texture and glycoprotein content, indicating its complex biochemical composition at the level of lens capsule, conjunctiva and eyelid.

PEX can become problematic when the flakes become enmeshed in a "spongy area" known as the trabecular meshwork and block its normal functioning, and may interact with degenerative changes in the Schlemm's canal and the juxtacanalicular area. The blockage leads to greater-than-normal elevated intraocular pressure which, in turn, can damage the optic nerve. The eye produces a clear fluid called the aqueous humor which subsequently drains such that there is a constant level of safe pressure within the eye, but glaucoma can result if this normal outflow of fluid is blocked. Glaucoma is an umbrella term indicating ailments which damage the neural cable from the eye to the brain called the optic nerve, and which can lead to a loss of vision. In most cases of glaucoma, typically called primary open-angle glaucoma, the outflow does not happen normally but doctors can not see what is causing the blockage; with PEX, however, the flakes are believed to be a cause of the blockage. PEX flakes by themselves do not directly cause glaucoma, but can cause glaucoma indirectly by blocking the outflow of aqueous humor, which leads to higher intraocular pressure, and this can cause glaucoma. PEX has been known to cause a weakening of structures within the eye which help hold the eye's lens in place, called lens zonules.

The literature recognizes pseudoexfoliation syndrome as a risk factor in cataract surgery. A review based on 999 eyes with pseudoexfoliation reported 156 intra- or postoperative incidents. The identified predictive factors were a shallow anterior chamber, cataract grade, neutrophil-to-lymphocyte ratio, preoperative intraocular pressure, and symmetry of the exfoliation material.

Causes

The cause of pseudoexfoliation glaucoma is generally unknown.

PEX is generally believed to be a systemic disorder, 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 affected by PEX. 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. 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.

Diagnosis

PEX is usually diagnosed by an eye doctor who examines the eye using a microscope. The method is termed slit lamp examination and it is done with an "85% sensitivity rate and a 100% specificity rate." Since the symptom of increased pressure within the eye is generally painless until the condition becomes rather advanced, it is possible for people affected by glaucoma to be in danger yet not be aware of it. As a result, it is recommended that persons have regular eye examinations to have their levels of intraocular pressure measured, so that treatments can be prescribed before there is any serious damage to the optic nerve and subsequent loss of vision.

Treatment

While PEX itself is untreatable , it is possible for doctors to minimize the damage to vision and to the optic nerves by the same medical techniques used to prevent glaucoma.

• Eyedrops. This is usually the first treatment method. Eyedrops can help reduce intraocular pressure within the eye. The medications within the eyedrops can include beta blockers (such as levobunolol or timolol) which slow the production of the aqueous humor. And other medications can increase its outflow, such as prostaglandin analogues (e.g. latanoprost). And these medicines can be used in various combinations. In most cases of glaucoma, eyedrops alone will suffice to solve the problem.
• Laser surgery. A further treatment is a type of laser therapy known as trabeculoplasty in which a high-energy laser beam is pointed at the trabecular meshwork to cause it to "remodel and open" and improve the outflows of the aqueous humor. These can be done as an outpatient procedure and take less than twenty minutes. One report suggests this procedure is usually effective.

• Eye surgery. Surgery is the treatment method of last resort if the other methods have not worked. It is usually effective at preventing glaucoma. A surgeon cuts an opening in the white portion of the eye known as the sclera, and removes a tiny area of the trabecular meshwork which enables the aqueous humor to discharge. This lowers the internal pressure within the eye and lessens the chance of future damage to the optic nerve. Cases with pseudophacodonesis and dislocated IOL have been increasing in number, according to one report. In cataract surgery, complications resulting from PEX include capsular rupture and vitreous loss.
• Drug therapy. There are speculations that if genetics plays a role in PEX, and if the specific genes involved can be identified, that possibly drugs can be developed to counteract these mutations or their effects. But such drugs have not been developed .

Patients should continue to have regular eye examinations so that physicians can monitor pressure levels and check whether medicines are working.

Epidemiology

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. 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 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, 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. 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.

History

Pseudoexfoliation syndrome (PEX) was first described by an ophthalmologist from Finland named John G. Lindberg in 1917. He built his own slit lamp to study the condition and reported "grey flakes on the lens capsule", as well as glaucoma in 50% of the eyes, and an "increasing prevalence of the condition with age." The latter ailment is caused by heat or "infrared-related changes in the anterior lens capsule" and is characterized by "lamellar delamination of the lens capsule." Sometimes the two terms "pseudoexfoliation" and "true exfoliation" are used interchangeably but the more precise usage is to treat each case separately.

Research

Scientists and doctors are actively exploring how PEX happens, its causes, and how it might be prevented or mitigated. Research activity to explore what causes glaucoma has been characterized as "intense".

References

References

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