Glaucoma

Glaucoma is a disorder of increased intraocular pressure (IOP)-induced optic neuropathy. There are a few different forms of glaucoma, different causes of increased ocular pressure, namely, open-angle and closed-angle (both have primary and secondary forms), as well as developmental. The “angle” refers to the iridocorneal angle of the anterior chamber of the eye. In open-angle glaucoma, there is either excess aqueous production or insufficient outflow. Either way, pressure builds, which ultimately compresses the optic nerve head.

• In angle-closure glaucoma, there is narrowing (or complete closure) at the iridocorneal angle.
• Developmental glaucoma is a disorder of infancy and childhood.

• The most common causes of blindness are cataracts, glaucoma, age-related macular degeneration (especially in Whites), and diabetic retinopathy.

• The anterior eye cavity divides into:
• The anterior chamber, which lies anterior to the iris.
• The posterior chamber, which lies posterior to the iris.
• The Canal of Schlemm, which lies within the sclera at the corneoscleral junction.

• The ciliary epithelia from the ciliary process actively secrete aqueous humor into the posterior chamber (the space between the lens and iris).
• The aqueous humor then flows through the pupil into the anterior chamber (the space between the iris and cornea).
• The aqueous humor is then reabsorbed at the iridocorneal filtration angle through the trabecular meshwork into the canal of Schlemm.

• In angle-closure glaucoma, there is apposition of key anterior structures, which trap the flow of aqueous humor.
• For instance, there can be abutment of the lens and iris or the iris and the cornea, with resultant fluid obstruction.
• In open angle glaucoma, fluid flows freely in between the iris and lens but its reabsorption is blocked via poor uptake at the trabecular meshwork or canal of Schlemm, such as from uveitis.

• In open-angle glaucoma, patients are typically asymptomatic. It is not painful, does not cause eye redness, and it does not impact central vision until late-stage. So it is easily missed without routine assessment of intraocular pressure.

• The eye, itself, appears normal in open-angle glaucoma.

Intraocular Pressure

• Intraocular pressure is typically elevated (> 21 mmHg) but may be normal (8 – 21 mmHg).

Fundoscopic Exam

• Glaucoma produces the following findings on fundoscopic exam (but exam may be normal): optic disc thinning, hollowing-out of the optic nerve, called “cupping”, alteration of the optic cup shape, or disc rim notching. Note that cupping is considered the most reliable finding, and a useful value to suggest glaucoma is when the cup is > 50% of the diameter of the vertical disc.

• If the intraocular pressure rises slowly, patients may be asymptomatic but if there is rapid development of angle-closure glaucoma, patients can have any of the following symptoms:
• Intense eye pain (pain in V1 distribution).
• Nausea and vomiting.
• Vision impairment/obscuration with halos around lights, rainbows, blurring and even transient loss of vision.

• Typically, only one eye is affected (it is unilateral). Sudden increase in intraocular pressure can produce:
• Conjunctival injection ("bloodshot eye" -- redness/conjunctival vessel engorgement).
• Corneal cloudiness/haziness can be seen.
• The pupil can be mid-dilated (4 – 6 mm diameter pupil) and react poorly to light.
• Forward bowing of the iris with a resultant shallow anterior chamber.

Intraocular Pressure

• Patients may or may not demonstrate increased intraocular pressure (IOP > 21 mmHg) at the time of evaluation.

Fundoscopic Exam

• Do not dilate the eye.
• Cupping (see above), may or may not be present.

Gonioscopy

• Gonioscopy is a slit-lamp exam using a special lens and is the gold standard diagnostic method for diagnosing glaucoma.

• “Global Prevalence of Glaucoma and Projections of Glaucoma Burden through 2040: A Systematic Review and Meta-Analysis - PubMed.” Accessed July 9, 2024. https://pubmed.ncbi.nlm.nih.gov/24974815/.

• Jayaram, Hari, Miriam Kolko, David S. Friedman, and Gus Gazzard. “Glaucoma: Now and Beyond.” The Lancet 402, no. 10414 (November 11, 2023): 1788–1801. https://doi.org/10.1016/S0140-6736(23)01289-8.

• “Primary vs. Secondary Angle Closure Glaucoma - EyeWiki.” Accessed July 9, 2024. https://eyewiki.org/Primary_vs._Secondary_Angle_Closure_Glaucoma.

• Prum, Bruce E., Lisa F. Rosenberg, Steven J. Gedde, Steven L. Mansberger, Joshua D. Stein, Sayoko E. Moroi, Leon W. Herndon, Michele C. Lim, and Ruth D. Williams. “Primary Open-Angle Glaucoma Preferred Practice Pattern(®) Guidelines.” Ophthalmology 123, no. 1 (January 2016): P41–111. https://doi.org/10.1016/j.ophtha.2015.10.053.

The Eye Diseases Prevalence Research Group. “Causes and Prevalence of Visual Impairment Among Adults in the United States.” Archives of Ophthalmology 122, no. 4 (April 1, 2004): 477–85. https://doi.org/10.1001/archopht.122.4.477.

• Weinreb, Robert N., Tin Aung, and Felipe A. Medeiros. “The Pathophysiology and Treatment of Glaucoma: A Review.” JAMA 311, no. 18 (May 14, 2014): 1901–11. https://doi.org/10.1001/jama.2014.3192.

Eye with Angle-Closure Glaucoma Glaucoma fundus Normal fundus