Glaucoma classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Rohan Bir Singh, M.B.B.S.[2]
The glaucoma is typically classified is as open angle or closed angle and as primary or secondary. There have been multiple schemes proposed for the classification for glaucoma. However the classification of the glaucomas based on initial events and classification based on mechanisms of outflow obstruction are commonly used.
Classification based on angle
Open-angle Glaucoma
- Primary open-angle glaucoma (POAG)
- not associated with known ocular or systemic disorders that cause increased resistance to aqueous outflow or damage to optic nerve
- usually associated with elevated IOP
- Normal-tension glaucoma
- considered in continuum of POAG; often used when IOP is not elevated
- Juvenile open-angle glaucoma
- used when open-angle glaucoma diagnosed at young age (typically 10-30 years of age)
- Glaucoma suspect
- normal optic disc and visual field associated with elevated IOP
- suspicious optic disc and/or visual field with normal IOP
- Secondary open-angle glaucoma
- increased resistance to trabecular meshwork outflow associated with other conditions (e.g. pigmentary-, phacolytic-, steroid-induced-)
- increased posttrabecular resistance to outflow secondary to elevated episcleral venous pressure (e.g. carotid cavernous sinus fistula)
Angle-Closure Glaucoma
- Primary ACG with relative pupillary block
- movement of aqueous humor from posterior chamber to anterior chamber restricted
- peripheral iris in contact with trabecular meshwork
- Acute angle closure
- occurs when IOP rises rapidly as a result of relatively sudden blockage of the trabecular meshwork
- Subacute angle closure (intermittent angle closure)
- repeated, brief episodes of angle closure with mild symptoms and elevated IOP, often a prelude to acute angle closure
- Chronic angle closure
- IOP elevation caused by variable portions of anterior chamber angle being permanently closed by PAS
- Secondary ACG with pupillary block
- e.g. swollen lens, secluded pupil
- Secondary ACG without pupillary block
- posterior pushing mechanism: lens-iris diaphragm pushed forward (e.g. posterior segment tumor, scleral buckling procedure, uveal effusion)
- anterior pulling mechanism: anterior segment process pulling iris forward to form PAS (e.g. iridocorneal endothelial syndrome, neovascular glaucoma, inflammation)
- Plateau iris syndrome
- primary angle closure with or without component of pupillary block, but pupillary block is not predominant mechanism of angle closure
Childhood Glaucoma
- Primary congenital/infantile glaucoma
- primary glaucoma present from birth to first few years of life
- Glaucoma associated with congenital anomalies
- associated with ocular disorders (e.g. anterior segment dysgenesis, aniridia)
- associated with systemic disorders (e.g. rubella, Lowe syndrome)
- Secondary glaucoma in infants and children
- e.g. glaucoma secondary to retinoblastoma or trauma
Classification on based on initial event
Congenital and Developmental Glaucoma (Q15.0)
- Developmental glaucoma
- Primary congenital glaucoma
- Infantile glaucoma
- Glaucoma associated with hereditary of familial diseases
Primary Glaucoma and its Variants (H40.1-H40.2)
- Primary glaucoma
- Variants of primary glaucoma
- Pigmentary glaucoma
- Exfoliation glaucoma, also known as pseudoexfoliative glaucoma or glaucoma capsulare
Secondary Glaucoma (H40.3-H40.6)
- Secondary glaucoma
- Inflammatory glaucoma
- Uveitis of all types
- Fuchs heterochromic iridocyclitis
- Phacogenic glaucoma
- Angle-closure glaucoma with mature cataract
- Phacoanaphylactic glaucoma secondary to rupture of lens capsule
- Phacolytic glaucoma due to phacotoxic meshwork blockage
- Subluxation of lens
- Glaucoma secondary to intraocular hemorrhage
- Traumatic glaucoma
- Angle recession glaucoma: Traumatic recession on anterior chamber angle
- Postsurgical glaucoma
- Neovascular glaucoma
- Drug-induced glaucoma
- Corticosteroid induced glaucoma
- Alpha- chymotrypsin glaucoma. Postoperative ocular hypertension from use of alpha chymotrypsin.
- Glaucoma of miscellaneous origin
- Associated with intraocular tumors
- Associated with retinal detachments
- Secondary to severe chemical burns of the eye
- Associated with essential iris atrophy
Absolute Glaucoma (H44.5)
- Absolute glaucoma
Classification based on mechanism of outflow obstruction
Open Angle Glaucoma Mechanisms
- Pre-trabecular (membrane overgrowth)
- fibrovascular membrane (neovascular glaucoma)
- endothelial layer, often with Descemet-like membrane (iridocorneal endothelial syndrome, posterior polymorphous dystrophy, penetrating and non-penetrating trauma)
- epithelial downgrowth
- fibrous ingrowth
- inflammatory membrane (Fuchs heterochromic iridocyclitis,luetic interstitial keratitis)
- Trabecular
- idiopathic (chronic open-angle glaucoma, juvenile open-angle glaucoma)
- “clogging” of trabecular meshwork
- red blood cells (hemorrhagic-, ghost cell-, sickled red blood cells)
- macrophages (hemolytic-, phacolytic-, melanomalytic-)
- neoplastic cells (primary ocular tumors, neoplastic tumors, juvenile xanthogranuloma)
- pigment particles (pigmentary-, exfoliation syndrome / glaucoma capsulare, malignant melanoma)
- protein (uveitis, lens-induced glaucoma)
- viscoelastic agents
- α-chymotrypsin-induced glaucoma
- vitreous
- alterations of the trabecular meshwork
- steroid-induced glaucoma
- edema (uveitis, scleritis, episcleritis, alkali burns)
- trauma (angle recession)
- intraocular foreign bodies (hemosiderin, chalcosis)
- Post-trabecular
- obstruction of Schlemm’s canal (e.g. collapse at canal)
- elevated episcleral venous pressure
- carotid cavernous fistula
- cavernous sinus thrombosis
- retrobulbar tumors
- thyroid ophthalmopathy
- superior vena cava obstruction
- mediastinal tumors
- Sturge-Weber syndrome
- familial episcleral venous pressure elevation