primary%20open-angle%20glaucoma
PRIMARY OPEN-ANGLE GLAUCOMA
Primary open-angle glaucoma (POAG) is a chronic, progressive, usually bilateral disease of the eye with an insidious onset.
It is most often characterized by optic nerve damage, defects in the retinal fiber layer and subsequent visual field loss in the absence of underlying ocular disease or congenital abnormalities.
It is generally asymptomatic until it has caused a significant loss of visual field.
Occasionally, patients with very high intraocular pressure may complain of nonspecific headache, discomfort, intermittent blurring of vision or even halos caused by corneal edema.

Surgical Intervention

  • Option for patients who have failed to respond to medications or laser therapy
  • Involves the creation of a filtration bleb that would permit the flow of aqueous humor from the eyes
  • Complications & risks may arise, including cataract & permanent loss of vision

Penetrating Glaucoma Surgery

  • Trabeculectomy
    • Provides an alternative path for aqueous humor flow w/ success rates ranging from 31-56%
    • Success rate may be reduced in patients who have previously undergone cataract surgery involving the conjunctiva
    • Long-term intraocular pressure (IOP) control is achieved but in some cases, repeat surgery or further therapy may be required
    • Disadvantages include higher risk of postoperative hypotony, cataract formation & bleb complications
    • Subconjunctival scarring may occur; use of antimetabolites (Mitomycin-C, 5-fluorouracil) during & after surgery may help reduce this
    • Long-term control may be achieved; further therapy or reoperation, however, is still possible
  • Aqueous shunts
    • Also known as glaucoma drainage devices, setons, or tube shunts
    • Have been used to manage medically uncontrolled glaucoma when trabeculectomy or laser therapy has been unsuccessful in controlling IOP or is deemed likely to fail
      • May also be used in patients who have had prior incisions to the conjunctiva (eg cataract extraction)
    • Intra-operative & post-operative complications are similar to trabeculectomy; however, the risk of infection is less w/ aqueous shunts
    • Complications unique to this surgery include diplopia, erosion of the tube through the conjunctiva

Nonpenetrating Glaucoma Surgery

  • Incidence of complications such as hypotony & bleb-related problems including other intraoperative complications (eg iris prolapse, expulsive hemorrhage, are reduced)
  • Less efficient in lowering IOP compared w/ trabeculectomy
  • Eg viscocanalostomy, nonpenetrating deep sclerectomy, canaloplasty

Management of Refractory Primary Open-Angle Glaucoma

If condition is refractory to treatment, consider:

Cyclodestructive Surgery

  • Has been traditionally used in managing refractory glaucomas
    • Reported success rates of 34-94% 
  • Acts by reducing the rate of aqueous production
  • Easier to perform & w/ reduced post-operative care as compared w/ trabeculectomy
  • Possible complications include  intraocular pressure (IOP) spikes, post-operative inflammation, w/ likelihood of frequent retreatments, phthisis bulbi

Glaucoma Drainage Device

  • Implantable devices for refractory glaucoma
  • Higher chance of success in refractory glaucoma (eg in patients w/ previous multiple glaucoma surgeries)
  • Post-op complications include hypotony, ocular motility disorder, infection, implant extrusion, pain & cataract
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