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KEY POINTS: COMMON VISUAL-FIELD DEFECTS FOUND IN GLAUCOMA

1.Superior/inferior nasal step.

2.Superior/inferior arcuate defect.

3.Generalized depression.

4.Paracentral loss.

5.Temporal or central island with advanced disease.

10.What is a glaucoma suspect?

A glaucoma suspect is an adult who has an open angle on gonioscopy and one of the following findings in at least one eye:

&Optic nerve suspicious for glaucoma

&Visual-field defect consistent with glaucoma

&Elevated intraocular pressure consistently greater than 22 mmHg

If a patient has two or more of the above findings, then a diagnosis of glaucoma is more likely.

The decision to treat a glaucoma suspect takes into account the above findings as well as additional risk factors and the general health of the patient.

American Academy of Ophthalmology Basic and Clinical Science Course, Section 10. San Francisco, American Academy of Ophthalmology, 2004.

11.In examination of the optic nerve, what findings could be consistent with a diagnosis of glaucoma or suspicion of glaucoma?

Diffuse narrowing of the optic nerve rim, focal narrowing or notching of the optic nerve rim, vertical elongation of the optic cup, nerve fiber layer defects, nerve fiber layer hemorrhages, and asymmetric cupping of the optic nerves are all signs of glaucoma or suspicion of glaucoma. An acquired pit of the optic nerve is a pathognomonic sign of glaucoma.

Coleman AL, Morrison JC, Callender O: Evaluation of the optic nerve head. In Higginbotham E, Lee D (eds): Clinical Guide to Glaucoma Management. Boston, Elsevier, 2004, pp 183–191.

KEY POINTS: COMMON OPTIC NERVE FINDINGS IN GLAUCOMA

1.Diffuse narrowing of the neuroretinal rim.

2.Focal narrowing or notching of the neuroretinal rim.

3.Nerve fiber layer defects.

4.Disc hemorrhages.

5.Asymmetry of optic nerve cupping.

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factors in glaucomatous visual field loss. Arch Ophthalmol 94:1274–1276, 1976.

13.A 74-year-old African American female presents for a routine eye examination. She has not been to an ophthalmologist in 10 years. Her intraocular pressures are 26 mmHg in the right eye (OD) and 24 mmHg in the left eye (OS). Her optic nerves are as pictured in Fig. 15-2. What information is important to obtain from the patient?

The optic nerves in Fig. 15-2 show significant asymmetry with a narrower rim supertemporally in the right eye in comparison to the left eye. She has not been seen by an ophthalmologist for years. The history is a crucial part of the evaluation; it identifies possible secondary causes for glaucoma (e.g., trauma, steroid use) as well as risk factors such as family history, helps determine the visual demands and support system of the patient, and can give an idea of the patient’s general health and life expectancy. All of these components combine to help formulate a treatment plan most likely to be agreeable to the patient, least likely to be damaging, and of an appropriate level of aggressiveness for each individual patient.

Figure 15-2. Asymmetry of the cup-to-disc ratio can be an early sign of glaucoma.

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14. If the patient in question 13 had been to another ophthalmologist several year and was presenting for the first time in your office, what information

would be important to obtain?

Old records are valuable. Knowing about previous surgeries, lasers, and medicines (both those that worked and those that did not) helps formulate a current treatment plan. Previous intraocular pressure readings, former visual-field tests, and optic nerve evaluations can establish the rate of progression of the disease, a key piece of information in determining the level of aggressiveness needed in treatment.

15.True or false: If the patient in question 13 had a normal visual field, she would be unlikely to have glaucoma.

False. Visual-field defects may not be apparent until as much as 50% of the optic nerve fiber layer has been lost.

16.True or false: If the patient in question 13 had intraocular pressures of 19 mmHg OD and 18 mmHg OS, then she would be unlikely to have glaucoma.

False. A single intraocular pressure measurement in the normal range is not enough to eliminate the possibility of glaucoma. Several studies suggest that as many as 30–50% of individuals in the general population having glaucomatous optic nerve damage and visual-field defects have an initial IOP measurement of less than 22 mmHg. Diurnal IOP fluctuation and artificially low measurements due to decreased central corneal thickness or other factors may contribute to the normal IOP. In addition, patients with average pressure glaucoma have glaucomatous optic neuropathies without ever demonstrating elevated intraocular pressures.

Mitchell P, Smith W, Attebo K, et al: Prevalence of open-angle glaucoma in Australia. The Blue Mountains Study. Ophthalmology 103:1661–1669, 1996.

Sommer A, Tielsch JM, Katz J, et al: Relationship between intraocular pressure and primary open angle glaucoma among white and black Americans. The Baltimore Eye Survey. Arch Ophthalmol 109:1090–1095, 1991.

17.How does intraocular pressure (IOP) fluctuate in glaucoma patients?

Individuals without glaucoma may have an IOP fluctuation of 2–6 mmHg over a 24-hour period. IOP in glaucoma patients may vary widely. Untreated glaucoma patients may vary by 15 mmHg or more. The majority of patients demonstrate the highest pressures in the morning with decrease throughout the day. Other patterns with peak pressures at night or midday as well as flat patterns without variation have been reported.

Zeimer RC: Circadian variations in intraocular pressure. In Ritch R, Shields MB, Krupin T (eds): The Glaucomas, 2nd ed. St. Louis, Mosby, 1996, pp 429–445.

18.What role does central corneal thickness play in the evaluation of glaucoma?

Corneal thickness is important to consider for two reasons. First, corneal thickness affects the measurement of IOP so that the measured IOP may be inaccurate if the corneal thickness is not average. The actual average central corneal thickness is approximately 544 m. IOP is about 5 mmHg lower than measured for each 100 m that the cornea is thicker than normal. The IOP is actually higher than measured when the cornea is thinner than average. Second, a

thin central cornea, in itself, is associated with more severe glaucoma. The Ocular Hypertension Treatment Study identified reduced central corneal thickness as a risk factor for glaucoma in patients with IOP between 24 mmHg and 32 mmHg.

Brandt JD, Beiser JA, Kass MA, et al: Central corneal thickness in the Ocular Hypertension Treatment Study. Ophthalmology 108:1779–1788, 2001.

Ehlers N, Bramsen T, Sperling S: Applanation tonometry and central corneal thickness. Acta Ophthalmol 53:34–43, 1975.