Diagnosis → Ophthalmology

Glaucoma

Etiology

Causes [wpc]

1. Primary open-angle glaucoma (POAG): most common

   • Increased resistance to aqueous outflow --> Ineffective drainage system

   • Rise in IOP --> Reduced blood flow to the optic nerve

   • Slow and painless damage to the optic nerve

   • Characteristic damage patterns in the visual field and the optic nerve:

     • Loss of peripheral vision in one or typically both eyes

     • Eventually loss of central vision (permanent and irreversible)

2. Primary angle-closure glaucoma (PACG): 10% of glaucoma cases

   • Darkness/drugs --> pupillary dilatation --> thick iris

   • Age-related lens thickening --> pushes the iris anteriorly

   • Closure of the angle formed between the cornea and the iris

   • Blockage of the outflow tract --> IOP rapidly increases

     • Blurry vision

     • Corneal edema

     • Eye pain

     • Headache

     • Nausea

     • Emesis

3. Secondary glaucoma arises due to obstruction/damage to trabecular meshwork

   • Lens subluxation in Marfan syndrome

   • Irregular corneal endothelium migration onto the trabecular meshwork

   • Neovascularization (retinal artery/vein occlusion, proliferative diabetic retinopathy)

   • Peripheral anterior synechiae

   • Eye injury

   • Post-ophthalmic surgery (ciliary body edema)

   • Sulfa drugs --> ciliochoroidal effusion

   • Pseudoexfoliation (flaky material within the anterior chamber that clog the trabecular meshwork)

   • Pigment dispersion syndrome (pigment granules from the posterior iris surface)

   • Steroid-induced glaucoma

   • Carotid-cavernous fistula

   • Ellingson syndrome (uveitis-glaucoma-hyphema syndrome)

   • Glaucomatocyclitic crisis (Posner-Schlossman syndrome)

   • Inflammatory glaucoma: Uveitis/iridocyclitis

4. Normal-tension glaucoma

   • Optic nerve damage due to normal pressure, atherosclerosis or vascular insufficiency

   • Associated with migraines, Raynaud phenomenon, autoimmune diseases, ischemic vascular diseases, and coagulopathies

5. Congenital/infantile glaucoma

   • Affects individuals between the ages of 1 and 36 months

   • Trabeculodysgenesis

   • Anterior segment dysgenesis

Pathophysiology [wpc]

• Aqueous humor is produced by the non-pigmented epithelial cells and is crucial in maintaining intraocular pressure and nourishing ocular tissues

• Continuous drainage: the trabecular meshwork --> Schlemm canal --> episcleral veins

• A decline in aqueous humor drainage --> elevated IntraOcular Pressure (IOP)

• Glaucoma has strong correlation with IOP ≥ 21 mmHg

Risk factors [wpc]

• IOP ≥ 21mmHg

• Older age

• Hypermetropia (shallow anterior chamber)

• An angle between the iris and the cornea ≤ 20° during gonioscopy

• Anterior chamber depth of less than 2.5 mm

Complications

• Visual field loss

• Blindness

Epidemiology

Incidence per 100.000 [bie][pon]

Default

Approach

• Blood tests: CBC count, ESR

• Serelogy for syphilis

• Serum protein electrophoresis (autoimmune etiology)

• Clinical exxamination:

  • Slit lamp examination of the anterior segment

  • Fundoscopic examination

  • Visual field testing

  • Tonometry (Goldmann applanation tonometry)

  • Gonioscopy

  • Pachymetry

• Optical coherence tomography (OCT)

• Confocal scanning laser ophthalmoscopy

• Scanning laser polarimetry

• Neuroimaging

Diagnostic criteria

• Optic neuropathy: Loss of retinal ganglion cells/axons within the optic nerve

• Characteristic optic nerve head appearance

• Progressive loss of vision

• Usually in conjunction with elevated intraocular pressure ≥ 21 mmHg

Treatment

1. Goal: impossible to reverse vision loss. Treatment aims to lower IOP [wpc]

2. Medications: [wpc][ihy]

   • Prostaglandin analogs

   • β-blockers

   • Carbonic anhydrase inhibitors

   • α-2 agonists

   • Miotic agents

   • Rho-kinase inhibitors

   • Nitric oxide-donating medications

   • Hyperosmotic agents (isosorbide dinitrate, mannitol, glycerin)

3. Laser:

   • Laser trabeculoplasty: benefits last months, and retreatments are necessary

   • Laser ablation of the ciliary body to reduce aqueous production

   • Laser peripheral iridotomy (acute angle-closure glaucoma)

4. Surgery:

   • Trabeculectomy

   • Deep sclerectomy

   • Canaloplasty

   • Insertion of a drainage valve/tube shunt

   • Minimally invasive glaucoma surgery (MIGS) [ihy]

     • Deep sclerectomy/viscocanalostomy

     • 360-degree suture canaloplasty

     • Trabectome

     • Endoscopic cyclophotocoagulation (ECP)

     • iStent implant

     • Gonioscopy-assisted transluminal trabeculotomy (GAAT)

     • Kahook dual blade

     • Xen Gel Implant

Differential diagnoses

Cluster headache, Conjunctivitis, Corneal abrasion, Corneal ulcer, Endophthalmitis, Episcleritis, Hyphema, Iridocyclitis, Keratitis, Migraine, Optic neuritis, Periorbital cellulitis, Subconjunctival hemorrhage