Psuedoexfoliation syndrome is an age related systemic disorder characterized by the deposition of grayish-white amyloid like protein fibres in the anterior segment of the eye. The deposits often produce a characteristic pattern on the anterior lens surface and are found in the iris, ciliary epithelium, corneal endothelium and trabecular meshwork. The accumulation of this protein prevents the efficient drainage of eye fluid (aqueous humour) resulting in an increase in intraocular pressure (IOP). This can eventually lead to unilateral pseudoexfoliation glaucoma in about 40-50% of XFS patients. XFS mainly affects patients over the age of 70. It has also been found to have a higher prevalence in women than men. Certain ethnic groups also show higher rates of XFS, primarily Scandinavians and Northern Europeans.
Regular eye exams are important in diagnosing this disorder as XFS patients may have no specific symptoms. Treatment involves IOP lowering medications, trabeculoplasty to open the trabecular meshwork or eventually eye surgery to enable filtration. Patients that progress to pseudoexfoliation glaucoma show higher IOP and a more aggressive clinical course than patients with primary open angle glaucoma eventually resulting in rapid optic neuropathy and vision loss.
XFS appears to be inherited as an autosomal dominant trait with incomplete penetrance. Association studies have found the gene LOXL1 to be linked with XFS. LOXL1 encodes a lysyl oxidase enzyme that is involved in the formation of crosslinks in elastin and collagen.
Abu-Amero et al. (2010) analyzed LOXL1 mutations in Saudi Arabian pseudoexfoliation glaucoma (PEG) patients. Ninety three patients with confirmed PEG were recruited for this study. PEG was diagnosed based on the presence of exfoliation material on the pupil margin or anterior lens surface, glaucomatous optic neuropathy with associated visual field loss in one or both eyes and intraocular pressure ≥22 mmHg in either eye. One hundred and one healthy ethnically-matched control subjects were recruited based on the absence of any signs of exfoliation and an intraocular pressure ≤18 mmHg. DNA of patients and controls were isolated, LOXL1 sequence was analyzed and allele frequencies were compared. The G allele frequencies of the SNPs rs1048661 and rs3825942 were found to differ significantly between patients and controls (p=0.0056 and p=0.000005). This is in accordance with previous studies on other non-African populations. Two novel SNPs, found in patients but not in controls, were also reported: g.25722 C>G in exon 4 resulting in D484E was detected in 2 patients and predicted to be benign; and g.28084 T>G in exon 6 resulting in Y559D was detected in 1 patient and predicted to be probably damaging.