• 8 Pearls for Evaluation of the Glaucoma Suspect

    Glaucoma is the most common cause of irreversible vision loss. Early detection is essential to preserving vision in these patients who are often asymptomatic and rely on a thorough approach by their ophthalmologists to determine if and when treatment should begin. Here are eight steps to help formulate a methodical approach to these glaucoma suspects:

    1. Obtain a thorough patient history and assess risk factors. It is important to review well-known glaucoma risk factors for primary open-angle glaucoma, including age (60 years and older), African-American heritage, medical conditions such as diabetes and hypothyroidism, and a positive family history, particularly a first-degree relative. Additional history of ocular trauma and surgery, as well as prior use of steroids (inhaled, oral and topical) and current medications are also relevant to the glaucoma suspect workup. 

    Lastly, when evaluating for normal tension glaucoma, review specific risk factors such as migraine headache, hypotension, sleep apnea and Raynaud’s phenomenon.

    2. Evaluate intraocular pressure (IOP). Accurate IOP measurement remains central to the evaluation of a glaucoma suspect, as maximum untreated IOP and IOP fluctuation have been correlated to glaucoma progression. However, not all measurements are created equal. Goldmann applanation tonometry, rather than handhelds and other tonometers, remains the gold standard and should be utilized when possible. Additionally, be aware that patient factors such as posture, breath holding and eyelid squeezing, as well as physician technique in IOP measurement, can all significantly affect readings.

    3. Evaluate the angle and other pertinent anterior segment findings. A careful slit-lamp examination can be useful in identifying diseases such as pigment dispersion syndrome and exfoliative syndrome that may lead to secondary glaucoma. Pupillary ruff loss, iris transillumination defects, exfoliative material, presence of pigment in the angle, phacodonesis and corneal endothelial pigment are all significant findings that may increase suspicion of glaucoma. The gold standard of angle examination remains gonioscopy, especially the use of a four-mirror lens (Posner or Sussman) that allows for dynamic indentation gonioscopy. Additional diagnostic tools such as anterior segment optical coherence tomography (OCT) and ultrasound biomicroscopy can be supplementary, but are not necessary in routine evaluation of glaucoma suspects

    4. Optic nerve head assessment. A dilated and detailed slit-lamp optic nerve head examination remains a key element in the evaluation of a glaucoma suspect and monitoring for progression. Determining the cup-to-disc (C/D) ratio, particularly vertical C/D ratio, is a good first step. Also document rim notching, parapapillary atrophy, disc hemorrhage and associated retinal nerve fiber layer defects, which are crucial to monitoring glaucoma suspects. Stereoscopic color photography of the optic nerve head on a yearly basis is also recommended.

    5. Corneal thickness and biomechanical properties. Central corneal thickness (CCT) measurement has become a routine part of glaucoma evaluation due to the multitude of studies associating thin corneas with glaucoma and glaucomatous progression. Although available formulae to correct IOP based on CCT do not improve prediction of glaucoma development, it is important to account for a thin cornea

    Additionally, corneal biomechanical properties such as corneal hysteresis and corneal resistance factor can be useful adjunctive data in the consideration of future progression, as these properties can be significantly different in glaucoma patients compared with healthy patients.

    6. Visual field evaluation. One of the key elements in evaluating glaucoma suspects is visual field testing. The reference standard for determining the presence of glaucoma remains standard automated white-on-white perimetry (SAP), preferably a Swedish Interactive Testing Algorithm (SITA) standard program rather than SITA Fast. There has been evidence suggesting that frequency-doubling technology (FDT) and short-wavelength automated perimetry detect visual field loss earlier than SAP. However, recent data have shown that FDT has a comparatively higher sensitivity in detecting early glaucoma.

    Additionally, it is imperative to obtain several visual fields to assess for reproducibility before making a final diagnosis, as there is often a learning curve associated with testing.

    7. Ancillary imaging in glaucoma. There are many readily available imaging devices to help aid in the diagnosis and management of the glaucoma suspect. These include confocal scanning laser ophthalmoscopy, scanning laser polarimetry and OCT. Structural changes such as nerve fiber layer loss and rim notches often precede perimetric loss and can be measured in glaucoma suspects to determine initial risk and appropriate follow up. While objective, quantitative and highly reproducible, these technologies should not replace careful and serial examination of the optic nerve head and visual field testing.

    8. Putting it all together. Determining whether a glaucoma suspect requires treatment and how often he or she should be monitored requires synthesizing historical information, physical examination and test interpretation. Although risk calculators such as the Ocular Hypertension Treatment Study Risk Calculator (http://ohts.wustl.edu/risk/calculator.html) can help determine in which patient to initiate treatment, this decision is based ultimately on a well synthesized clinical judgment.

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    About the authors: Sandra Fernando Sieminski, MD, is a clinical assistant professor and director of the glaucoma service at the Ross Eye Institute, affiliated with the University at Buffalo. She completed her ophthalmology residency at Georgetown University and her glaucoma fellowship at the New York Eye and Ear Infirmary. Dr. Sieminski is also the ophthalmology clerkship director for the University at Buffalo School of Medicine, and has an interest in international education. James G. Chelnis, MD, is a PGY-3 resident at the University at Buffalo.