primary open-angle glaucoma

Primary open-angle glaucoma is caused by trabecular blockage which is where the Aqueous humor in the eye drains out. Because the microscopic passage ways are blocked, the pressure builds up in the eye and causes imperceptable very gradual vision loss. Peripheral vision is affected first but eventually the entire vision will be lost if not treated.

Diagnosis is made by looking for cupping of the optic nerve.

The treatment’s goal is to release the fluid by opening uveoscleral passageways, which are acted upon by prostoglandin agonists. Beta blockers such as timolol, alpha 2 agonist, work by decreasing aqueous formation.

Carbonic anhydrase inhibitors decrease bicarbonate formation from ciliary processes in the eye, thus decreasing formation of Aqueous humor. Parasympathetic analogs are drugs that work on the trabecular outflow by opening up the passageway and constricting the pupil.

Etiology

Primary open angle glaucoma (POAG) has been found to be caused by mutation in genes at several loci.

Three genes have been identified:

 GLC1A (MIM.137750) is caused by mutation in the MYOC gene (610652) on chromosome 1q.

 GLC1G (MIM.609887) may be caused by mutation in the WDR36 gene (MIM.609669) on chromosome 5q22.

 GLC1E (Primary open angle glaucoma-1E)is caused by mutation in the OPTN gene (MIM.602432) on chromosome 10p.

Morbid loci:

 GLC1B (MIM.606689) on chromosome 2
 GLC1C on chromosome 3
 GLC1D (MIM.602429) on chromosome 8q
 GLC1F (MIM.603383) on chromosome 7q
 GLC1I (MIM.609745) on chromosome 15q
 GLC1J (MIM.608695) on chromosome 9q22
 GLC1K (MIM.608696) on chromosome 20p
 GLC1L (MIM.137750) on chromosome 3p
 GLC1M (MIM.610535) on chromosome 5q22
 GLC1N on chromosome 15q22-q24.

Miscellaneous

 Nail-patella syndrome (NPS) (MIM.161200), which is caused by mutation in the LMX1B gene (MIM.602575), has open angle glaucoma as a pleiotropic feature.

References

 Gong G, Kosoko-Lasaki O, Haynatzki GR, Wilson MR. Genetic dissection of myocilin glaucoma. Hum Mol Genet. 2004 Apr 1;13 Spec No 1:R91-102. PMID: #14764620