Open-Angle Glaucoma

  • Slowly progressive cupping of optic disc leading to vision loss
  • Often first detected by finding pathologic optic disc cupping on screening exams
  • Causes still undefined but elevated ocular pressure contributes
  • Intraocular pressure often elevated because aqueous fluid does not flow out normally through trabecular meshwork
  • Treated by lowering intraocular pressure with topical medications or with eye surgery that diverts aqueous through hole in sclera
  • Accounts for over 95% of glaucoma cases
  • Affects about 1% of adults aged over 40 years
  • Family history of open-angle glaucoma in 20%
  • Most afflicted patients are asymptomatic until vision loss is far advanced
  • Pathologic cupping of optic disc is earliest sign; compare to normal disc which has cup-to-disc ratio of 0.5 or less
  • Visual field defect if condition advanced
  • Elevated intraocular pressure in many-but not all!
  • Other optic neuropathies and retinopathies, but pathologic cupping of optic disc almost unique to glaucoma
  • "Secondary glaucoma," caused by elevated intraocular pressure in patients with iritis, hyphema, or other eye trauma
  • Coloboma of optic disc
  • Tilted disc of myopia
  • Non-glaucomatous (arteritic ischemic and compressive) optic neuropathies (but pathologic cupping rare)
  • Screen for this condition by looking for pathologic optic disc cupping in adults, especially those with family history of glaucoma, noting that...
  • Normal ratio of physiologic cup diameter to optic disc diameter should not exceed 0.5
  • If you think optic disc is pathologically cupped, refer non-urgently for confirmation and management
  • Ophthalmoscopic screening for optic disc cupping is critical, especially in those with family history of open-angle glaucoma
  • Screening by measuring intraocular pressure (tonometry) not effective because intraocular pressure often not elevated in open-angle glaucoma AND...
  • Measuring intraocular pressure takes practice and skill
  • Eyedrops used to lower intraocular pressure
  • If eyedrops fail to lower pressure, or optic disc cupping and vision loss progress, surgical treatment may be used, consisting of....
  • Making a hole in sclera to allow aqueous to bypass trabecular meshwork
  • Medical and surgical treatment not always successful in halting progression of glaucoma, so that....
  • Some patients become visually disabled, but...
  • Early treatment considered beneficial