Specific treatment goals:
- Stop progression and maintain quality-of-life
- Lower IOP to desired pressure; if causing damage
- Identify and treat underlying causes
OPEN ANGLE GLAUCOMA
Indication for treatment:
- Patients with high IOPs may or may not require treatment; the latter is based on evidence of ongoing damage, rather than a specific IOP
- Some patients with normal IOP may require treatment, if there is evidence of ongoing injury and visual field loss
- Target pressures should be set and achieved, but treatment is generally escalated until there is no more evidence of progression
- Choice of therapeutic agents depends on patients disease status, target ocular pressure, medical history, pharmacoeconomics, and psychological factors
Alpha-agonists: Suppress aqueous inflow and include
Red eye and ocular irritation are often associated with the use; caution required in pregnancy, contraindicated if the patient is taking monoamine oxidase inhibitors (MAO).
Beta-blockers: Suppress aqueous inflow and include
- Carteolol (only available in the US)
- Metipranolol (only available in the US)
May cause some dry eyes, nonselective agents require caution in patients with obstructive airway diseases. Mask symptoms of hypoglycemia in individuals with diabetes.
Carbonic anhydrase inhibitors: Suppress aqueous inflow and include
- Dorzolamide (topical)
- Brinzolamide (topical)
- Acetazolamide (oral)
- Methazolamide (oral)
Prescribed when topical treatment is not effective.
May cause hypokalemia if sodium and potassium levels are depressed as in kidney or liver disease caution is advised.
Prostaglandin analogs: Increase outflow and include
- Latanoprostene bunod
Discoloration of iris and foreign body sensation is a common complaint; caution advised on use during pregnancy.
Rho kinase inhibitor: suppressing the rho kinase enzymes responsible for fluid increase
Conjunctival hyperemia is a common complaint.
Cholinergic agents: facilitate aqueous outflow
Headaches and dim vision is a common complaint.
- Laser trabeculoplasty
- Increases aqueous outflow
- The effect typically is not permanent
- Laser can be repeated (especially Selective Laser Trabeculoplasty-SLT)
- Diode laser applied directly through sclera targeting the ciliary body
- Decreases aqueous production
- Usually reserved for eyes with poor visual potential
- Trabeculectomy: Creation of a filtration bleb to allow egress of aqueous humor from the eye. An artificial fistula is made between the anterior chamber and a formed space underneath the conjunctiva
- Aqueous shunt: Small silicone tube implanted in the anterior chamber that leads to a baseplate placed underneath the conjunctiva. Shunts are typically used in patients who have failed conventional surgery or have an underlying diagnosis that increases the risk of surgical failure
- Endocyclophotocoagulation: Endoscopic visualization and application of laser to the ciliary processes (where aqueous humour is produced.) Often done at the time of cataract surgery. Moderate IOP lowering
MICRO invasive glaucoma surgeries (minimally invasive glaucoma surgeries):
Newer surgical procedures, which may carry less risk and morbidity than traditional procedures. In general, these interventions do not lower IOP when compared with others, and often used for less advanced cases.
- Schlemm’s canal procedures
- iStent trabecular micro-bypass – smallest implant in the human body. L-shaped stent placed through the trabecular meshwork into Schlemm’s canal. Usually done in conjunction with cataract surgery
- Trabectome – Electrocautery used to ablate trabecular meshwork, opening up Schlemm’s canal. Often done in conjunction with cataract surgery
- Canaloplasty – Schlemm’s canal is approached externally with meticulous dissection. A fiber optic is used to canulate the canal 360 degrees, then a suture is left in the canal and tied with tension to expand it. The anterior chamber is not entered with this technique
- Suprachoroidal procedures – Various procedures shunting aqueous humour from the anterior chamber into the suprachoroidal space. This space is found between the choroid and the sclera. These procedures have not yet achieved widespread use
ANGLE CLOSURE GLAUCOMA
Goal of treatment:
- Prevention and reversal of angle closure
- Control of intraocular pressure
Indications for treatment:
- Patients with signs or symptoms suggesting possible acute angle closure should be referred for emergent assessment and treatment to prevent permanent damage
In acute emergencies, treatment usually involves, combination of both topical and oral agents.
- All classes of pressure lowering drops should be used
- Topical steroid
- Oral acetazolamide- 250 mg two tablets stat. The eye pressure should be checked 30 to 60 minutes after giving oral acetazolamide. Used mainly to temporize until definitive treatment (surgery) can be arranged or underlying cause removed (e.g. steroid effect)
- IV mannitol
- Oral glycerol or isosorbide
Laser peripheral iridotomy
- Once the episode is controlled the treatment of choice is a laser peripheral iridotomy
- This procedure creates a tiny hole in the peripheral iris allowing drainage of aqueous humor and equalizing the pressure between the anterior and posterior chambers, thus relieving pupil block
- Reassess the IOP 30 to 120 minutes after the iridotomy
- If it is not possible to perform laser iridotomies, surgical peripheral iridectomy may be necessary
- Laser peripheral iridotomy is also indicated in the fellow eye as prophylaxis. It is recommended that all patients with narrow angles, symptomatic or not, should have prophylactic iridotomies performed
Complications of laser peripheral iridotomy
- Increased IOP
- Laser burns to the cornea, lens, or retina
- Glare or “white line” in vision
- Development of cataract
- Need for repeat treatment if spontaneous closure occurs
Other surgical procedures
- Goniosynechialysis: Mechanical lysis of peripheral anterior synechiae to restore drainage function
- Phacoemulsification: Removing the lens that is crowding the angle and replacing it with a flat intraocular lens implant