Definition
The term glaucoma refers to a group of progressive optic neuropathies characterized by an excavated appearance of the optic disc, often described as cupped (Fig 1-1), together with loss of ret i nal ganglion cells and their axons and corresponding vision loss. The primary site of injury is thought to be the lamina cribrosa, which has been shown to be structurally damaged in eyes with glaucomatous optic neuropathy, leading to the appearance of optic disc excavation. The causes of glaucoma are multifactorial and include ge ne tic and environmental factors.
IOP is a continuous risk factor for the development of glaucoma over its entire range; however, it is not elevated above the statistically normal range in a substantial proportion of patients with primary open- angle glaucoma (POAG) and is not a defining characteristic of the disease. Ocular hypertension (OHT) is defined as the presence of statistically elevated IOP in the absence of glaucomatous visual field or optic disc damage. A large proportion of patients with OHT do not go on to develop glaucoma.
Figure 1-1 Optic disc photo graph demonstrating optic disc excavation, or “cupping.” Note the focal neural rim loss (arrow) and exposed laminar pores superiorly. (Courtesy of Angelo P. Tanna, MD.)
In patients with glaucoma, the IOP at baseline— regardless of its actual level—is too high for ret i nal ganglion cell function and survival. It has been shown that in most patients with glaucoma, lowering the IOP will stop or slow visual field loss. In some eyes, however, optic nerve damage may pro gress despite treatment to lower the IOP. Clinicians often imprecisely use the word glaucoma in describing conditions in which the IOP is elevated in the absence of known glaucomatous neuropathy. Although this is common parlance, it should be avoided.
Quigley HA. Glaucoma. Lancet. 2011;377(9774):1367–1377.
Classification
Open- Angle, Angle- Closure, Primary, and Secondary Glaucomas
Adult forms of glaucoma are classified as open angle or angle closure and as primary or secondary ( Table 1-1). Pediatric forms of glaucoma are described in Chapter 11. Distinguishing open- angle glaucoma from angle- closure disease is essential from a therapeutic standpoint.
Open angle
In open- angle glaucoma (OAG), no obstruction of the trabecular meshwork is vis i ble on gonioscopic examination of the anterior chamber angle. The condition is further classified as primary open- angle glaucoma (POAG) when no under lying abnormality known to cause
Table 1-1 Classification of Glaucoma and Related Conditionsa
I. Open Angle
A. Primary open- angle glaucoma
Normal- tension glaucoma
Juvenile open- angle glaucoma
B. Secondary open- angle glaucoma
Pseudoexfoliation syndrome
Pigmentary glaucoma
Traumatic glaucoma (in patients with angle recession, traumatic hyphema, or other evidence of trauma)
Steroid- induced glaucoma
Glaucoma associated with intraocular inflammation
Hemolytic glaucoma (hemoglobin- laden macrophages obstruct TM)
Ghost cell glaucoma (degenerated RBCs obstruct TM)
Glaucoma associated with intraocular tumors (neoplastic cells, cellular material, debris, or RBCs obstruct outflow)
Glaucomatocyclitic crisis (Posner- Schlossman syndrome)
Fuchs uveitis syndrome
Uveitis- glaucoma- hyphema syndrome
Lens associated
a. Phacolytic glaucoma (leaked lens proteins obstruct TM) b. Lens particle glaucoma (retained lens material after surgery or trauma) c. Phacoantigenic glaucoma (inflammatory response after surgical or accidental lens trauma)
Glaucoma associated with elevated episcleral venous pressure
Glaucoma associated with siderosis
Schwartz syndrome (IOP elevation caused by photoreceptor outer segment release in association with rhegmatogenous ret i nal detachment)
IOP elevation associated with anti- VEGF therapy iii. Pseudophakic pupillary block (especially with ACIOL)
II. Angle Closure
A. Primary angle closureb
Primary angle- closure suspect (≥180° iridotrabecular contact without IOP elevation, PAS, or glaucomatous optic neuropathy)
Primary angle closure (≥180° iridotrabecular contact with IOP elevation and/or PAS in the absence of glaucomatous optic neuropathy)
Primary angle- closure glaucoma (≥180° iridotrabecular contact with IOP elevation and/or PAS and evidence of glaucomatous optic neuropathy)
Acute angle- closure crisis (closed angle with symptomatic IOP elevation)
Plateau iris configuration (per sis tent iridotrabecular contact after a patent laser peripheral iridotomy without IOP elevation after pupil dilation)
Plateau iris syndrome (per sis tent iridotrabecular contact after a patent laser peripheral iridotomy with IOP elevation after pupil dilation)
B. Secondary angle- closure glaucoma
With pupillary block
a. Lens- induced i. Phacomorphicc
ii. Ectopia lentis
Table 1-1 (continued) b. Aphakic pupillary block c. Posterior synechiae
Without pupillary block
a. Anterior pulling mechanism i. Neovascular glaucoma
ii. Iridocorneal endothelial syndrome
iii. Posterior polymorphous dystrophy
iv. Consolidation of inflammatory material v. Anterior synechiae due to trauma b. Posterior pushing mechanism i. Malignant glaucoma
ii. Uveal effusion
iii. Anterior rotation of ciliary body (eg, due to CRVO, scleral buckle, PRP)
iv. Phacomorphicc v. Cysts of iris or ciliary body
vi. Per sis tent fetal vasculature
vii. Retinopathy of prematurity