HS200 Unit 3 Open-Angle Glaucoma Disorder Profile Example

Sight Lost From the Edges Inward: A Unit 3 System Disorder Profile of Primary Open-Angle Glaucoma, Cause First

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Purdue University Global

HS200: Diseases of the Human Body

Unit 3 System Disorder Profile

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[Date]

The illustrative patient is composite; the review, screening statement and textbook cited are real.

Normal Structure and Function

The front of the eye is filled with a clear fluid called aqueous humor, made continuously by a structure behind the iris. The fluid flows forward through the pupil and drains out of the eye through a spongy tissue called the trabecular meshwork, which sits in the narrow corner formed by the colored iris and the clear front window of the eye. The balance between production and drainage sets the pressure inside the eye. At the back of the eye, about a million nerve fibers from the retina gather at the optic nerve head, where they leave the eye and carry visual signals to the brain.

What Glaucoma Is

Glaucoma is a group of diseases in which the optic nerve is progressively damaged, producing a characteristic pattern of vision loss. In the open-angle form, which accounts for most cases in the United States, the drainage angle looks open on examination, yet the nerve fibers die over years. Raised eye pressure is the main known risk factor and the only one that treatment can change, but some people develop damage at normal pressures and others tolerate high pressures without damage (Weinreb et al., 2014).

Causes and Risk Factors

The exact cause is not fully known. Contributing factors include increased resistance to outflow in the trabecular meshwork, which raises eye pressure; susceptibility of the optic nerve head to mechanical stress; and possibly reduced blood flow to the nerve. Risk rises with age, with a family history of glaucoma and with African or Hispanic ancestry. Thinner corneas and nearsightedness are also associated with higher risk.

Mechanism of Damage

Higher pressure inside the eye pushes on the optic nerve head, where the nerve fibers bend as they exit through a sieve-like plate. Over time, this stress, together with other factors, damages the fibers and their cell bodies in the retina, which die through a process of programmed cell death. As fibers are lost, the optic nerve head develops a deepened, hollowed appearance called cupping, visible to an examiner.

Presentation: Why It Is Silent

The fibers lost first usually carry signals from the edges of the visual field, not from the center. The brain fills in small gaps, and the other eye covers for the affected one, so a person notices nothing. Central vision, used for reading and recognizing faces, is often preserved until late. By the time someone notices bumping into objects or missing things to the side, a large share of the nerve may be gone, and that loss cannot be recovered.

Glaucoma takes vision from the edges inward, and the brain hides the gaps so well that the person is often the last to know.

Diagnosis

Diagnosis rests on three kinds of evidence gathered by an eye care professional: the appearance of the optic nerve head, often imaged with optical coherence tomography, which measures the thickness of the nerve fiber layer; visual field testing, which maps blind spots; and measurement of eye pressure. Pressure alone does not diagnose glaucoma, since some people with damage have normal pressures.

Treatment

All current treatment lowers eye pressure, the one modifiable factor. Eye drops either reduce fluid production or increase drainage. Laser treatment of the trabecular meshwork can improve outflow and is sometimes used first. Surgery creates a new drainage path when other measures fail. Treatment slows or stops further loss but does not restore lost vision (Weinreb et al., 2014).

Prevention and Screening

Because the disease is silent and the damage permanent, early detection is the main protection. The U.S. Preventive Services Task Force concluded in 2022 that evidence was insufficient to recommend for or against screening adults without symptoms in primary care (US Preventive Services Task Force, 2022). In practice, people at higher risk, such as older adults, those with a family history and people of African ancestry, are commonly advised to have regular comprehensive eye examinations.

Illustrative Patient

A composite 63-year-old man whose mother went blind from glaucoma has never had a dilated eye examination. At a vision screening for a new driver's license, he misses targets in his left visual field. An eye examination shows cupping of both optic nerves, raised pressure and early field loss in both eyes, worse on the left. He begins pressure-lowering drops and will be followed with regular field tests and imaging. His children are advised to start regular eye examinations earlier than usual because of the family history, and he is taught that skipping drops, which cause no change he can feel, allows the silent loss to continue.

Summary

Open-angle glaucoma links a drainage problem and a vulnerable optic nerve to slow, painless loss of side vision. Its silence explains its danger, and its single modifiable factor explains its treatment (Rogers, 2023).

References

Rogers, J. L. (Ed.). (2023). McCance & Huether's pathophysiology: The biologic basis for disease in adults and children (9th ed.). Elsevier.

US Preventive Services Task Force, Mangione, C. M., Barry, M. J., Nicholson, W. K., Cabana, M., Chelmow, D., Coker, T. R., Davis, E. M., Donahue, K. E., Epling, J. W., Jaén, C. R., Krist, A. H., Kubik, M., Li, L., Ogedegbe, G., Pbert, L., Ruiz, J. M., Simon, M. A., Stevermer, J., & Wong, J. B. (2022). Screening for primary open-angle glaucoma: US Preventive Services Task Force recommendation statement. JAMA, 327(20), 1992-1997. https://doi.org/10.1001/jama.2022.7013

Weinreb, R. N., Aung, T., & Medeiros, F. A. (2014). The pathophysiology and treatment of glaucoma: A review. JAMA, 311(18), 1901-1911. https://doi.org/10.1001/jama.2014.3192