Glaucoma

Make the Diagnosis: Glaucoma

Prior Probability of Glaucoma

Primary open-angle glaucoma (POAG) occurs in 2.6% of the population (95% CI, 2.1%-3.1%). This type of glaucoma often occurs with high intraocular pressure, but can also occur with normal intraocular pressure (≤ 21 mm Hg).

Patients in Whom Glaucoma Should Be Considered

Increasing age is the most common risk factor for POAG, with patients older than 80 years at the highest risk (prevalence, 7.8%; 95% CI, 5.2%-12%). Among all risk factors, high myopia (> 6 diopters) is the strongest risk factor (prevalence, 11%; 95% CI, 8.3-18). Other important risk factors are family history and black race (see Table 91-1).

Assessing the Likelihood of Glaucoma

Ophthalmologists have an advantage compared with other physicians in detecting glaucoma because they use indirect ophthalmoscopy, which provides a 3-dimensional view of the optic disc, as opposed to the 2-dimensional view with direct ophthalmoscopy. No studies of the ocular examination for glaucoma have assessed the performance of generalist physicians. Nonetheless, a generalist physician may notice the findings of an abnormal cup-to-disc ratio, a disc hemorrhage, or asymmetry between the discs (see Table 91-2). An intraocular pressure ≥ 22 mm Hg increases the likelihood of POAG (LR, 13; 95% CI, 8.2-17). While a lower intraocular pressure makes glaucoma less likely (LR, 0.65; 95% CI, 0.55-0.76), patients may still have normal tension glaucoma (see Table 91-1).

Reference Standard Tests

Glaucoma is an optic neuropathy characterized by irreversible loss of retinal ganglion cells. It is often associated with higher intraocular pressure and is broadly classified as either open-angle (the most common) or closed-angle. The reference standard examination must be determined by an ophthalmologic examination by a trained specialist, viewing the optic disc in stereo, with corroborative retinal nerve fiber loss and corresponding visual field loss.¹

Reference