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May 23, 2005
Workup Guidelines for Managing Normal- Tension Glaucoma
Review of OphthalmologyTo help determine whether a patient has normal-tension glaucoma or a different physical or neurological problem, I recommend the following:
• Check the visual field. Normal-tension glaucoma often has a characteristic dense paracentral loss impinging on fixation (superiorly more than inferiorly).
• Examine stereo disc photos, and/or HRT/GDx scans. Eyes with the same amount of total visual field loss as a POAG patient will have a thinner neuroretinal rim, especially superiorly and inferiorly. They are also more likely to have peripapillary atrophy.
• Check corneal pachymetry. Rule out an IOP error caused by a thin cornea.
• Perform gonioscopy. This can rule out subacute angle closure.
• Review the big picture. Go over the history of any present illnesses and conduct a Review of Systems. Consider having an autoimmune workup done if the Review of Systems is positive.
• Have an internist perform a comprehensive physical examination. The focus should be on neurological and circulatory concerns.
• Consider other tests. These could include an electrocardiogram, a complete blood count, and a serologic test for syphilis.
• If appropriate, order 24-hour blood-pressure monitoring. This may reveal blood-pressure related problems.
• If appropriate, perform neuroimaging. This is useful if the Review of Systems is positive, or the disc and/or visual field are not characteristic of glaucoma. Cupping occurs with neurologic disease at the following rates: arteritic ischemic optic neuropathy—50 percent; non-arteritic ischemic optic neuropathy—10 percent; compressive lesions—5 percent; and optic neuritis—less than 5 percent.
Some general guidelines: 1) With early loss of color vision or central vision, or if a visual field defect obeys the midline, odds are good that the problem is neurologic. 2) Remember that glaucoma is a chronic disease—be suspicious of rapid visual acuity loss. 3) When the problem is neurologic, both vision and pallor tend to be worse than the cupping. Conversely, when the problem is glaucoma, the cupping tends to be worse than the vision problems or pallor. 4) Generally, if the problem is glaucoma, you should be able to predict the visual field results by looking at the disc.
Finally, if it’s clear that your patient really does have NTG, aim to reduce pressure by 40 percent, with surgery as a viable option.
Posted by mehdi khanlari at May 23, 2005 11:32 PM