eye disorders
Primary Open Angle Glaucoma
Treatment of Primary Open Angle Glaucoma
Decreasing intraocular pressure (IOP) 20 to 40% Initially, medications (eg, prostaglandin analogs such aslatanoprostortafluprost, beta-blockers such astimolol) Sometimes surgery, such as laser trabeculoplasty or guarded filtration procedure Vision lost by glaucoma cannot be recovered. The goal is to prevent further optic nerve and visual field damage by lowering IOP. The target level is 20 to 40% below pretreatment readings or the IOP at which damage is known to have occurred. In general, the greater the damage caused by glaucoma, the lower the IOP must be to prevent further damage. If damage progresses, the IOP goal is lowered further and additional therapy is initiated. Initial treatment used to be medical therapy, proceeding to laser therapy and then incisional surgery if the target IOP is not met; however, subsequent evidence suggests that initial treatment with laser trabeculoplasty preserves visual fields and results in less frequent subsequent incisional glaucoma surgeries than treatment with medications ( Treatment reference ). Surgery may be the initial treatment if IOP is extremely high, the patient does not wish to use or has trouble adhering to medical therapy, or if there is significant visual field damage at presentation. Multiple medications are available (see table). Topical agents are preferred. The most popular are prostaglandin analogs, followed by beta-blockers (particularlytimolol). Other medications include alpha-2-selective adrenergic agonists, carbonic anhydrase inhibitors, rho kinase inhibitors, and cholinergic agonists. Oral carbonic anhydrase inhibitors are effective, but adverse effects limit their use. Patients taking topical glaucoma medications should be taught passive eyelid closure with punctal occlusion to help reduce systemic absorption and associated adverse effects, although the effectiveness of these maneuvers is controversial. Patients who have difficulty instilling drops directly onto the conjunctiva may place the drop on the nose just medial to the medial canthus, then roll the head slightly toward the eye so that the liquid flows into the eye. Typically, to gauge effectiveness, clinicians start medications in one (one-eye trial) or both eyes. Surgery for primary open-angle glaucoma and normal-pressure glaucoma includes laser trabeculoplasty, a guarded filtration procedure, and procedures that enhance only a portion of the drainage pathway. Selective laser trabeculoplasty(SLT) uses a pulsed double-frequency neodymium:yttrium-aluminum-garnet laser. SLT and argon laser trabeculoplasty (ALT) are equally effective initially, but SLT may have greater effectiveness in subsequent treatments. SLT is emerging as the standard of care for the initial treatment for newly diagnosed patients. Argon laser trabeculoplasty(ALT) may also be considered but is rarely used in lieu of SLT. Laser energy is applied to either 180º or 360º of the trabecular meshwork to improve the drainage of aqueous humor. Within 2 to 5 years, about 50% of patients require additional drug therapy or surgery because of insufficient IOP control. is the most commonly used filtration procedure. A hole is made in the limbal sclera (trabeculectomy), which is covered by a partial-thickness scleral flap that controls egress of aqueous from the eye to the subconjunctival space, forming a filtration bleb. Adverse effects of glaucoma filtration surgery include acceleration of Cataract growth, pressures that are too low, and transient accumulation of fluid in the choroidal space (ie, choroidal effusion) during the perioperative period. Patients with trabeculectomies are at increased risk of bacterial endophthalmitis and should be instructed to report any symptoms or signs of bleb infection (blebitis) or Endophthalmitis (eg, worsening vision, conjunctival hyperemia, pain) immediately. Partial-thickness proceduresbypass portions of the outflow pathways, unlike full-thickness procedures, even if guarded, that create a direct conduit between the anterior chamber and subconjunctival space. In general, trabecular meshwork bypass procedures appear to be safer but less effective than trabeculectomy: The ab externo approach (an approach from outside the eye), including viscocanalostomy, deep sclerectomy, and canaloplasty, involves a deep dissection of greater than>98% thickness of the scleral passage, leaving a window of Descemet membrane and/or the inner wall of the Schlemm canal and trabecular meshwork. The canal is dilated by using a viscoelastic solution (in viscocanalostomy) or a microcatheter (in canaloplasty). Deep sclerectomy generally relies on the formation of a conjunctival bleb. In the ab interno approach (an approach from inside the eye), a device is used to remove (eg, with ab interno goniotomy or trabeculectomy) or bypass (eg, with some stent procedures) the trabecular meshwork, creating direct communication between the anterior chamber and collecting channels. No bleb is formed. 1.Gazzard G, Konstantakopoulou E, Garway-Heath D, et al: Laser in glaucoma and ocular hypertension (LiGHT) trial: Six-year results of primary selective laser trabeculoplasty versus eye drops for the treatment of glaucoma and ocular hypertension.Ophthalmology130(2):139-151. doi: 10.1016/j.ophtha.2022.09.009 