I. What every physician needs to know.
Glaucomas are a group of eye disorders characterized by progressive optic nerve damage at least partly due to increased intraocular pressure (IOP). This causes the characteristic visual field defect associated with progressive loss of visual acuity. When classified simply, it is primarily of 2 types:
- Open angle glaucoma – addressed in this chapter
- Narrow angle/angle closure glaucoma
II. Diagnostic Confirmation: Are you sure your patient has open angle glaucoma?
- Clinical suspicion – based on typical signs/symptoms
- Diagnostic confirmation – by ophthalmoscopy, gonioscopy, visual field examination, and measurement of IOP
A. History Part I: Pattern Recognition:
Early diagnosis is difficult. The typically asymmetric deficits contribute to delay in recognition. However, some patients have complaints such as missing stairs if their inferior visual field has been lost, noticing portions of words missing when reading or having difficulty with driving. Usually, the patient becomes aware of visual field loss only when optic nerve atrophy is marked.
- Open/unobstructed angle on gonioscopy
- Characteristic optic nerve changes
- Visual field defects
B. History Part 2: Prevalence:
Glaucoma is a leading cause of irreversible blindness, second only to macular degeneration. Glaucoma can occur at any age but is 6 times more common among people over 60 years. Prevalence of primary open angle glaucoma (POAG) is 3-4 times higher in blacks than in Caucasians; in addition, blacks are up to 6 times more susceptible to optic disc nerve damage than Caucasians.
In a white population at risk for glaucoma, visual field loss can be expected to develop in about 3% of subjects over 10 years of follow-up without treatment. Risk increases with age and IOP. Patients over 40 years and those who have risk factors for open-angle or angle-closure glaucoma should receive a comprehensive eye examination every 1 to 2 years.
IOP can be elevated or within the average range.
Axons of retinal ganglion cells travel through the optic nerve carrying images from the eye to the brain. Damage to these axons causes ganglion cell death with resultant optic nerve atrophy and patchy vision loss. Elevated IOP (in unaffected eyes, the average range is 11 to 21mm Hg) plays a role in axonal damage, either by direct nerve compression or diminution of blood flow. However, the relationship between pressure and nerve damage is variable.
Of people with IOP over 21mm Hg (i.e., ocular hypertension), only about 1 to 2% per year (about 10% over 5 years) develop glaucoma. Additionally, about one third of patients with glaucoma do not have IOPs over 21mm Hg (known as low-tension glaucoma or normal-tension glaucoma).
IOP is determined by the balance of aqueous secretion and drainage. Elevated IOP is caused by inhibited or obstructed outflow, not oversecretion. In open-angle glaucoma, IOP is elevated because outflow is inadequate despite an angle that appears unobstructed. In angle-closure glaucoma, IOP is elevated when a physical distortion of the peripheral iris mechanically blocks outflow.
C. History Part 3: Competing diagnoses that can mimic open angle glaucoma.
Personal or family history of glaucoma. Past ocular history includes the following:
History of eye pain or redness or multicolored halos
Previous ocular disease
Previous ocular surgery
Past medical history
Other optic neuropathies
D. Physical Examination Findings.
The defining characteristic is optic nerve damage as evidenced by an abnormal optic disk. Glaucoma should be suspected in a patient with any of the following:
- Typical visual field defects
- Abnormal optic nerve on ophthalmoscopy
- Elevated or normal IOP
E. What diagnostic tests should be performed?
- Visual field testing
- Measurement of IOP
- Exclusion of other optic neuropathies
1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
Patients suspected of having open angle glaucoma may need work-up to rule out other causes for optic neuropathy, including, but not limited to, complete blood count, erythrocyte sedimentation rate (ESR), serology for syphilis and if suggested by the pattern of visual field loss, neuroimaging.
2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
- Fundus photography provides a permanent record of the appearance of the optic disc also useful for future references.
III. Default Management.
Three methods are available: The type of glaucoma determines the appropriate method:
- Laser surgery
- Incisional surgery
A. Immediate management.
Vision lost by glaucoma cannot be recovered because the axonal damage caused by the prolonged elevated IOP is irreversible. Decreasing IOP 20-40% to prevent further optic nerve and visual field damage is the primary goal. All patients should get a formal ophthalmology consultation prior to initiation of treatment
Initially treatment of choice (drugs)
- prostaglandin analogs
- β-blockers such as timolol
- α2-selective adrenergic agonists
- cholinergic agonists
- carbonic anhydrase inhibitors
B. Physical Examination Tips to Guide Management.
Initial treatment is usually drug therapy, proceeding to laser therapy and then incisional surgery if the target IOP is not met. Surgery may be the initial treatment of choice if IOP is extremely high. Surgical options include:
A guarded filtration procedure
Possibly tube shunts
C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.
No consensus exists on what the appropriate medical treatment is for preventing or delaying the damage due to POAG when a patient has only elevated IOP and no other signs of POAG. To date, no one has been able to define conclusively which subgroups will develop damage if left untreated.
Typically, to gauge effectiveness, clinicians start drugs in only one eye (one-eye trial), once improvement in the treated eye has been confirmed at a subsequent visit (typically 1 to 4 weeks later), both eyes are treated. This is mailny useful in helping to decide whether or not to treat (i.e., if the medication is effective in achieving good pressure reduction without adverse effects).
D. Long-term management.
Refer to ophthalmologist for further evaluation, management and follow-up.
Neuro-ophthalmology consultation may have a role in those patients who are experiencing progressive visual loss that does not appear to follow a typical glaucomatous pattern or if there are systemic symptoms or complaints.
Depending on the amount of optic nerve damage and level of IOP control, POAG patients may need to be seen from every 2 months to yearly, even sooner if a marked lack of IOP control is present
E. Common Pitfalls and Side-Effects of Management
Indications of treatment
- Patient factors
- Poor reliability on visual field examination or patient whose optic nerve is difficult to visualize
- History of vascular occlusion
- Signs of damage consistent with glaucomatous optic neuropathy are observed
- Progressive cupping, even in the absence of visual field loss
- If pressures are consistently above 28-30mm Hg
- Beta-blockers: adverse effects are due to systemic absorption of the drug :decreased cardiac output, and bronchoconstriction (bronchospasm), bradycardia, heart block, hypotension, depression or anxiety, and sexual dysfunction may be initiated or exacerbated. Ocular adverse effects may include blurred vision, eye ache, and corneal anesthesia.
- Alpha2-adrenergic agonists: systemic adverse effects include dry mouth, fatigue, and drowsiness. Ocular adverse effects include allergic (follicular) conjunctivitis and contact dermatitis.
- Carbonic anhydrase inhibitors: adverse effects are relatively rare but include superficial punctate keratitis, acidosis, paresthesias, anorexia, nausea, depression, dysgeusia, and lassitude
- Prostaglandin analogs: adverse effects include conjunctival hyperemia, iris pigmentation, CME, and uveitis.
- Timolol maleate/hemihydrate (Timoptic 0.25%, 0.5%; Timoptic XE, Betimol 0.25%, Istalol) – non-selective.
- Levobunolol 0.25%, 0.5%, (Betagan) – non-selective
- Carteolol ophthalmic (Cartrol, Ocupress) – blocks beta1 and beta2-receptors, and has mild intrinsic sympathomimetic activity (ISA), with possibly fewer cardiac and lipid profile adverse effects.
- Betaxolol ophthalmic (Betoptic-S) – beta1-selective adrenergic antagonist, with possibly less pulmonary effects than non-selective agents. IOP-lowering effect is slightly less than non-selective beta-blockers.
- Metipranolol hydrochloride (OptiPranolol) – beta-adrenergic blocker that has little or no intrinsic sympathomimetic effects and membrane stabilizing activity. Has little local anesthetic activity.
- Levobetaxolol (Betaxon) – selectively blocks beta1-adrenergic receptors.
- Apraclonidine 0.5%, 1% (Iopidine) – selective alpha-adrenergic agonist without significant local anesthetic activity. Has minimal cardiovascular effect.
- Brimonidine (Alphagan-P 0.2%, 0.15%, 0.1%)
Carbonic Anhydrase inhibitors (topical)
- Dorzolamide (Trusopt) – more commonly used concomitantly with other topical medicines.
- Brinzolamide (Azopt) – may cause less ocular discomfort on instillation, secondary to a buffered pH, but can still cause foreign body sensation.
- Acetazolamide (Diamox) – used for adjunctive treatment of chronic simple (open-angle) glaucoma and secondary glaucoma and preoperatively in acute angle-closure glaucoma when delay of surgery desired to lower IOP.
- Methazolamide (Neptazane)
Various combinations of above drugs are also available.
- Latanoprost 0.005% (Xalatan), Bimatoprost (Lumigan), Travoprost ophthamic solution (Travatan), Unoprostone (Rescula).
IV. Management with Co-Morbidities
H. Primary Lung Disease (COPD, Asthma, ILD)
Careful monitoring needed in patients on beta-blockers.
V. Transitions of Care
D. Arranging for Clinic Follow-up
Ophthalmology referral and follow-up.
2. What tests should be conducted prior to discharge to enable best clinic first visit.
3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit.
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- I. What every physician needs to know.
- II. Diagnostic Confirmation: Are you sure your patient has open angle glaucoma?
- A. History Part I: Pattern Recognition:
- B. History Part 2: Prevalence:
- C. History Part 3: Competing diagnoses that can mimic open angle glaucoma.
- D. Physical Examination Findings.
- E. What diagnostic tests should be performed?
- 1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
- 2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
- III. Default Management.
- A. Immediate management.
- B. Physical Examination Tips to Guide Management.
- C. Laboratory Tests to Monitor Response To, and Adjustments in, Management.
- D. Long-term management.
- E. Common Pitfalls and Side-Effects of Management
- IV. Management with Co-Morbidities
- H. Primary Lung Disease (COPD, Asthma, ILD)
- V. Transitions of Care
- D. Arranging for Clinic Follow-up
- 2. What tests should be conducted prior to discharge to enable best clinic first visit.
- 3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit.