الفهرس 
Primary open angle glaucomaOnly 14 pages are availabe for public view
 |  | from | 118 |  |  |
| | | from | 118 | | |
Abstract
Glaucoma is a disorder characterized by progressive loss of visual fields due to optic nerve damage due to , in most cases , elevation of intraocular pressure ( IOP ) . It’s classified into primary glaucoma which is unrelated to other ocular diseases , and secondary glaucoma which occurs as a consequence of other ocular abnormalities or pathology . It’s also identified by anterior chamber tissue alterations , accumulation of abnormal substances in the anterior chamber angle , and anatomical configuration of the anterior chamber angle (open- or closed-angle glaucoma) . According to Shaffer system , if greater than 20 degrees , the anterior chamber angle is considered , by definition , open .
Open angle glaucoma is primary or secondry . In the primary type the process is poorly understood . According to the mechanical theory , chronically elevated IOP kills retinal ganglion cells through apoptosis by compromising their axons while traversing the lamina cribrosa . The vascular theory suggests reduced blood flow to the retinal ganglion cells with elevated IOP . New studies show that elevated levels of glutamate within the vitreous activates protein receptors within ganglion cells increasing intracellular calcium to toxic levels , killing the cells . The secondary type occurs due to aqeous outflow obstruction pre-trabecularly ( as in neovascular glaucoma ) , trabecularly ( as in pigmentary glaucoma and glaucoma induced by hypertensive iridocyclitis ) or post-trabecularly ( as in carotid-cavernous fistula ).
Primary open angle glaucoma ( POAG ) is the most common type between all types of glaucomas . Diagnosis is done by retinal nerve fiber layer and optic nerve studies including imaging techniques ( like optical coherence tomography “ OCT ” and Heidelberg retinal tomography “ HRT ” ) , perimetry ( showing early loss of peripheral vision ) and tonometry ( showing raised IOP and exaggerated its diurnal flactuations ) . Gonioscopy shows normal open angle in POAG and any fibrovascular membrane obstructing the trabeculum in the secondry open angle glaucoma.
Medical therapy is the first and even the only line of treatment in most patients with open angle glaucoma . It falls into the following groups : drugs enhancing aqeous outflow ( which are prostaglandin analogues , alpha-adrenergic agonists and miotics ) , drugs decreasing aqeous secretion ( which are beta blockers , alpha-adrenergic agonists and carbonic anhydrase inhibitors ) . Other lines of treatment includes laser therapy and surgical treatment.
Prostaglandin analogues ( as latanoprost , travoprost , bimatoprost and unoprostone) increase both uveoscleral and trabecular aqeous outflow . They are now favoured as they are more efficient than other medications especially latanoprost which lower IOP by up to 50% . They have the advantage of requiring only once a day administration . Their side effects are few including conjunctival hyperaemia , hypertrichosis , hyperchromic heterochromia and rarely anterior uveitis . They must be used with caution with uveitic glaucoma . Systemic side effects include occasional headache . They are contraindicated in pregnancy and breast feeding .
Alpha-adrenergic agonists ( as bromidine ) act both by increasing uveoscleral outflow and by decreasing aqeous secretion . Bromidine decreases IOP up to 27% . It also has a neuroprotective effect through preventing retinal cells degeneration . It has serious systemic side efffects in infants including severe hypotension , so it is contraindicated in infants and children under 5 years of age . Also , it may cause allergy and conjunctival hyperemia.
Miotics ( pilocarpine ) increase trabecular aqeous outflow . It’s used only in the treatment of the primary type of open angle glaucoma . It’s less effective than prostaglandin analogues.
Drugs enhancing aqeous outflow can be combined with other antiglaucomatous drugs to improve both drug effectivity and patient compliance , also to be more cost effective.