Glaucoma
- Is a condition marked by high intraocular pressure (IOP) that damages the optic nerve.
Two major forms:
Acute Glaucoma
Results when the angle between the iris and the cornea becomes narrowed, restricting or blocking the drainage of aqueous humor through the trabecular network and the canal of Schlemn. This causes IOP to increase suddenly.- It may result from trauma, stress, or any process that pushes the iris forward against the inside of the cornea when there is already an anatomically shallow anterior or chamber.
- It is an acute, painful condition that can cause permanent eye damage within several hours.
Chronic (open-angle)
- Results from the gradual deterioration of the trabecular network that, as in the acute form, blocks drainage of aqueous humor and causes IOP to increase.
- If untreated, may result in degeneration of the optic nerve and visual field loss.
- It is the most common form of glaucoma, and its incidence increases with age.
- Genetics and conditions, such as diabetes and hypertension, also play a role.
Assessment:
1. Acute Glaucoma:
- Severe pain, occurring in and around the eyes due to increased IOP; may transitory attacks.
- Cloudy, blurred vision; rainbow color around lights.
- Hazy cornea due to edema; may be profuse lacrimation and ciliary injection.
- Nausea and vomiting may occur.
- Pupil is mild-dilated and fixed.
2. Chronic Glaucoma
- Mild, bilateral discomfort (tired feeling in the eyes).
- Slow loss of peripheral vision – central vision remains unimpaired; in later stages, progressive loss of visual field.
- Increased IOP causes halos to appear around lights.
Diagnostic Evaluation:
- Tonometry shows elevated IOP in acute and chronic disease.
- Gonioscopy studies the angle of the anterior chamber of the eye in acute disease.
- Ophthalmoscopy may show pale optic disk (acute disease) or signs of clipping and atrophy of the disk (chronic disease). Dilation of the pupil is avoided if the anterior of chamber is shallow.
Pharmacologic Interventions:
1. In acute glaucoma, emergency drug management is initiated to decrease eye pressure.
- Parasympathomimetics (carbachol, pilocarpine) may be used as miotics to cause the pupil to contract and draw the iris away from the cornea, thus enlarging the angle and allowing aqueous humor to drain.
- Carbonic anhydrase inhibitors (acetazolamide, methazolamide), given orally to depress aqueous humor production.
- Beta-adrenergic blockers (betaxolol, timolol), given topically, may reduce aqueous humor or facilitate its drainage.
- Hyperosmotics (mannitol, glycerol) increase blood osmolarity and diurese the aqueous humor given I.V.
2. In chronic glaucoma, a combination of miotic agent and carbonic anhydrase inhibitor is usually given.
Surgical Interventions:
1. Surgery is indicated for acute glaucoma if IOP is not maintained within normal limits by pharmacotherapy and if there is progressive visual field loss with optic nerve damage.
2. Types of surgery for acute glaucoma include:
a. Peripheral iridectomy – Small portion of the iris excised so aqueous humor can bypass pupil.
b. Trabeculectomy – part of trabecular meshwork and iris removed.
c. Laser iridectomy – creates multiple incisions in the iris to create openings for aqueous to flow.
3. Types of surgery for chronic glaucoma include:
a. Laser trabeculoplasty – creates multiple surface burns to increase outflow of aqueous humor; treatment of choice if IOP unresponsive to medical regimen.
b. Iridencleisis – opening between anterior chamber and conjunctiva to bypass blocked meshwork and allow aqueous humor to be absorbed into conjunctival tissues.
c. Cyclodiathermy or cyclocryotherapy – super-cooled probe or electrical current used to interfere with ability to secrete aqueous humor by ciliary body.
d. Corneoscleral trephine (rarely done) – a permanent drainage opening is made at the junction of the cornea and sclera through the anterior chamber.
Nursing Interventions:
- Monitor for any pain or visual changes.
- Monitor the patient’s compliance with medications and follow-up care.
- Administer antiemetics as directed to prevent vomiting, which will increase IOP.
- Administer medications I.V., orally or topically, as directed, and explain the importance of medications, the proper procedure for administration of drops, and possible adverse reactions.
- After surgery, elevate head of the bed 30 degrees to promote drainage of aqueous humor after a trabeculectomy.
- Administer medications (steroids and cycloplegics) as directed after peripheral iridectomy to decrease inflammation and to dilate the pupil.
- Use an eye patch or shield in children for several days to protect the eye; in adults, patch is usually removed within several hours.
- Alert the patient to avoid prolonged coughing or vomiting, emotional upsets such as worry, fear, anger; exertion such as pushing and heavy lifting.
