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).
Table 91-1.Common Risk Factors for Primary Open-Angle Glaucoma |Favorite Table|Download (.pdf) Table 91-1. Common Risk Factors for Primary Open-Angle Glaucoma
|Risk Factor ||Prevalence of Primary Open Angle Glaucoma, 95% CI ||Odds Ratio, 95% CI |
|Myopia, diopters || || |
| >6 ||11 (8.3-18) ||5.7 (3.1-11) |
| >3 ||6.0 (4.5-7.8) ||2.1 (1.3-3.4) |
|Family history ||7.7 (5.5-11) ||3.2 (2.0-5.2) |
|Black race ||7.5 (6.8-8.4) ||2.9 (1.4-5.9) |
|Age, years || || |
| ≥80 ||7.8 (5.2-12) ||2.9 (1.9-4.3) |
| 70-79 ||5.1 (3.6-7.2) ||2.5 (1.9-3.1) |
| 60-69 ||3.7 (2.7-5.0) ||1.5 (1.3-1.7) |
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).
Table 91-2.Common Ocular Findings Used for Diagnosing Primary Open-Angle Glaucoma |Favorite Table|Download (.pdf) Table 91-2. Common Ocular Findings Used for Diagnosing Primary Open-Angle Glaucoma
| ||LR+ (95% CI) ||LR- (95% CI) |
| ||Clinical Examination |
|Cup-to-disc ratio, ≥ 0.7 ||14 (5.3-39) ||0.62 (0.53-0.71) |
|Disc hemorrhage ||12 (2.9-48) ||0.94 (0.83-0.98) |
|Cup-to-disc asymmetry, ≥ 0.3 mm ||7.3 (3.3-16) ||0.89 (0.83-0.94) |
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
American Academy of Ophthalmology Glaucoma Panel. Preferred Practice ...