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 and risks may arise, including cataract and permanent loss of vision

Penetrating Glaucoma Surgery

Trabeculectomy

  • Provides an alternative path for aqueous humor flow with success rates ranging from 31-88%
  • 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 and bleb complications
  • Subconjunctival scarring may occur; use of antimetabolites (Mitomycin-C, 5-fluorouracil) during and 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)
  • Intraoperative and postoperative complications are similar to trabeculectomy; however, the risk of infection is less with 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 and bleb-related problems including other intraoperative complications eg iris prolapse, expulsive hemorrhage, are reduced
  • Less efficient in lowering IOP compared with trabeculectomy
  • Eg viscocanalostomy, nonpenetrating deep sclerectomy, canaloplasty

Minimally Invasive Glaucoma Surgery (MIGS)

  • Also referred to as micro-invasive glaucoma surgery
  • Performed using an ab interno approach and causes minimal trauma to ocular tissues
  • Long-term data is limited but have a better safety profile although less effective in lowering IOP than trabeculectomy and aqueous shunt surgery
  • Usually combined with phacoemulsification
  • Eg Ab interno trabeculectomy, trabecular microbypass stent

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 and with reduced postoperative care as compared with trabeculectomy
  • Possible complications include intraocular pressure (IOP) spikes, postoperative inflammation and pain, with likelihood of frequent retreatments, phthisis bulbi
  • Postoperative management includes checking IOP 24-48 hours after the procedure

Glaucoma Drainage Device

  • Implantable devices for refractory glaucoma
  • Higher chance of success in refractory glaucoma (eg in patients with previous multiple glaucoma surgeries)
  • Postop complications include hypotony, ocular motility disorder, infection, implant extrusion, pain and cataract
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