Throughout your residency, you will frequently encounter patients who show up for a comprehensive eye exam but quickly need to be transitioned into a glaucoma workup. The high incidence of glaucoma and its asymptomatic presentation often means that an ophthalmologist needs to be able to access the following framework quickly and smoothly.
History
Symptoms: While open-angle glaucoma is typically asymptomatic, patients can present with late-stage symptoms. Subtle symptoms may vary from blurred vision and difficulty driving to difficulty adjusting to the dark. When glaucoma has been diagnosed and visual acuity drops below 20/20, a subjective decrease in vision should always warrant more testing.
Angle-closure glaucoma, on the other hand, presents acutely with severe pain, significantly decreased vision and even nausea and vomiting from the pain.
Duration of disease and prior treatment: I like to start with, “How long have you been diagnosed with glaucoma?” Ask about adverse events in the past, such as bradycardia or bronchospasm with beta blockers or contact dermatitis with brimonidine.
Medical history and systemic medications: If a patient discloses highly uncontrolled diabetes and an acute rise in intraocular pressure (IOP), think neovascular glaucoma. History of facial trauma or orbital contusion? Think angle recession glaucoma. If there are signs of acute angle closure, ask about sulfa drugs, topiramate and anticholinergics.
Family history: A strong family history of glaucoma in immediate family members raises the risk of developing glaucoma and is an independent risk factor. Ask about the severity of glaucoma in family members (including use of eye drops, any surgeries and any vision loss).
Exam
The basic 8-point eye exam always needs to be completed for a new patient. Here are some specific pointers for a glaucoma patient.
Visual acuity: Even patients with 20/20 central visual acuity can have a severely constricted visual field. Don’t let the patient’s central vision fool you into a sense of false security.
Intraocular pressure: Normal IOP ranges from 12 to 21 mmHg. Goldmann applanation is the gold standard for IOP measurement.
Central corneal thickness (CCT): This averages 530 to 540 μm. A thicker CCT tends to confer a “protective” factor, and the patient’s nerve is able to tolerate a higher pressure. Conversely, a thin CCT tends to increase the risk of glaucoma development or progression.
Slit lamp exam:
Cornea: Look for Krukenberg spindles (i.e., endothelial pigment deposits indicative of pigment dispersion glaucoma).
Iris: Transillumination defects (TIDs) help guide toward glaucoma subtypes:
- Peripupillary TIDs: pseudoexfoliation glaucoma
- Midperipheral TIDs: pigment dispersion
- Other TIDs: prior history of herpetic disease or a haptic in the sulcus space uveitis-glaucoma-hyphema
Optic nerve: Be aware of significant cupping, disc hemorrhages and changes to the nerve (compare exam to previous pictures).
Retina and macula: Look for other diseases such as macular edema that could cause visual field defects.
Visual fields:
Reliability: First look at reliability. High fixation losses are typically a result of when the patient is looking around. False positives may happen if the patient is “trigger happy” and clicks when there is no stimulus. False negative can happen when a patient does not click even though they previously saw the light in the same position.
Pattern of loss: Look for typical patterns of nasal defects, plus arcuates, and be very cautious in patients with central vision threatening fields. Recognize common artifacts such as cloverleaf defects and lid and rim artifacts.
Mean deviation and pattern standard deviation: These measurements help you track progression over time. Mean deviation is how much the defect deviates from an age-matched patient. Pattern standard deviation is a difficult concept to understand but basically it reveals the significance of a defect in an individual test point, relative to the rest of the patient’s mean deviation.
Progression of defects: The more fields, the more powerful your testing is. Always compare your current fields to all the patient’s older fields (not just those from last year).
OCTs: The OCT reflects the status of the nerve structure. After assessing for reliability, evaluate the nerve for thinning in a vertical fashion. The retinal nerve fiber layer clock diagram will help you determine focal thinning in the superotemporal and inferotemporal sectors, which is typical of glaucoma. The most important use is in comparison year after year to determine if there is progressive thinning.
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Jenny Chen, MD, MS, is an assistant professor of ophthalmology and a glaucoma specialist at UC Davis. She also serves as the chief of ophthalmology at the VA hospital in Mather, CA.
Roma Patel, MD, MBA, is an associate professor of glaucoma at Baylor College of Medicine in Houston, where she also serves as the chief of ophthalmology for Ben Taub Hospital.