Glaucoma: Too Much Aqueous Humor Is Nothing To Laugh At

The eye is a fragile and carefully balanced organ. At the very front of the eye is a fluid-filled chamber called the anterior chamber. This is located between the clear cornea at the front and the pupil, where light enters the rest of the eye. The fluid that fills this area is called the aqueous humor. The aqueous humor is critically important for cleaning and bringing nutrients to the lens. It is like a clear version of blood. Another key job the aqueous humor performs is maintaining eye pressure.

The pressure in the eye needs to be maintained within a very specific range (12-22 mm Hg). Aqueous humor continuously flows through the front of the eye at a very slow rate (like blood, but slower). When the flow rate out of the eye gets disrupted, eye pressure increases.

Doctors call high eye pressure ocular hypertension. The major characteristic is increased eye pressure without other symptoms. When eye pressure causes damage to the optic nerve, we call it glaucoma. Glaucoma can occur in two ways, closed-angle or open-angle. Closed angle is sudden and a medical emergency. Open-angle makes up almost all cases of glaucoma and is gradual in onset. Typical symptoms of open-angle glaucoma are vision problems in the middle of sight. These can include trouble with reading, seeing faces, walking, and driving. Both types will cause permanent blindness if untreated.

Open-angle glaucoma can happen to anyone but is much more common in adults over 60 years old. Most cases are females, and black and Asian populations experience higher rates of the condition. There are several underlying reasons for open-angle glaucoma: vascular, anatomical, genetic, or immune. Because of this wide spread of causes, there are several risk factors:

• Genetics / Family history
• Diabetes
• Extreme nearsightedness
• Hypertension
• Eye injury
• Eye abnormalities
• Steroid use
• Smoking

Several treatments are available for glaucoma. These include surgical and medication-based treatments, and surgically implanted medications. The goal of all treatments is to increase the flow of fluid out, decrease the amount of fluid coming in, or to decrease the volume of the anterior chamber. Medications are quite effective when taken properly. Unfortunately, fewer than one third of patients adhere to doctor recommendations for glaucoma eye drops after a year. This is in spite of the condition being progressive in nature and leading to blindness. Effective implanted medication delivery systems may provide better outcomes for patients.

References:

Allison, K., Patel, D., & Alabi, O. (2020). Epidemiology of glaucoma: the past, present, and predictions for the future. Cureus, 12(11).

Li, F., Huang, W., & Zhang, X. (2018). Efficacy and safety of different regimens for primary open‐angle glaucoma or ocular hypertension: A systematic review and network meta‐analysis. Acta ophthalmologica, 96(3), e277-e284.

Robin, A. L., & Muir, K. W. (2019). Medication adherence in patients with ocular hypertension or glaucoma. Expert Review of Ophthalmology, 14(4-5), 199-210.