Tools ODs can utilize to diagnose, treat glaucoma
ODs must have the right tools in their toolboxes when treating glaucoma correctly, says Optometry Times board member Michael Chaglasian, OD, FAAO, at Vision Expo East in New York.
New York-ODs must have the right tools in their toolboxes when treating glaucoma correctly, says Optometry Times board member Michael Chaglasian, OD, FAAO, at Vision Expo East in New York.
“You always want to have the right tool to do your job correctly,” he says. “With new tools and treatments available, ODs are in a great position moving forward.”
Dr. Chaglasian says ODs should be utilizing five tools in their treatment of glaucoma:
• Risk Calculator for Ocular hypertension- Free
• Risk factor considerations for Corneal hysteresis- New
• Optical coherence tomography (OCT) imaging for retinal nerve fiber layer (RNFL) and macular scans- Improved
• Central 10-2 testing-Sometimes
• Progression analysis-Essential
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Treating ocular hypertension
Intraocular pressure (IOP) greater than 21 mm Hg in one or both eyes, as measured by applanation tonometry on two or more occasions, is the main risk when treating ocular hypertension in glaucoma patients, says Dr. Chaglasian.
“You must review the patient’s overall risk before treating ocular hypertension,” he says. “The Humphrey Matrix Visual Field (VF) is a great screening device and a great place to start screening glaucoma patients.”
The Humphrey Matrix VF isn’t very consistent, he says, and following patients over time is the best method.
“Personally, I use the HFA 24-2 VF,” he says. “I choose the best strategy based on the patient and his needs.”
Dr. Chaglasian says a great free tool ODs should use is the Ocular Hypertension Treatment Study (OHTS) risk calculator, which is available online.
“You can use the OHTS risk calculator online to input your patients’ information to get the their estimated chance of developing glaucoma in the next five years,” he says. “But if cornea is thin due to LASIK, you can’t use this tool. This is to be used only when evaluating untreated corneas.”
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To use the OHTS risk calculator, you need the following information for each eye:
• Untreated IOP
• Central cornea thickness (CCT)
• Vertical cup-to-disc ratio by contour
• Pattern standard deviation
• Age
By importing this data into the OHTS risk calculator, you can determine a patient’s risk level, range, and recommended treatment.
Though the OHTS risk calculator is a great asset, Dr. Chaglasian warns against using it as a clinical replacement.
“The predictions derived using this method are designed to aid, not replace, clinical judgement,” he says.
Related: Standards of care in treating glaucoma
Risk factor consideration
Dr. Chaglasian identifies corneal hysteresis (CH) as another risk factor for consideration in glaucoma patients-average hysteresis value is around 10 mm.
“Higher hysteresis [>10] is good and lowers the risk for glaucoma,” he says. “Lower hysteresis [<10] is bad and elevates the risk for glaucoma.”
CH is a measure of:
• Corneal damping capacity
• Viscoelasticity
• Energy absorption capability of cornea
Dr. Chaglasian says the Ocular Response Analyzer (ORA) by Reichert is a good tool to assist with measuring hysteresis.
“You can use device to measure IOP on all patients and to assist with hysteresis,” he says.
ORA measures:
• Corneal compensated IOP-this value is closest to “true pressure”
• Corneal hysteresis
• IOP
• Waveform score
OCT imaging
OCT imaging for retinal nerve fiber layer (RNFL) and macular scans has always been a reliable tool in ODs’ toolboxes, but Dr. Chaglasian says the market is beginning to change.
“Things are changing as competition is heating up in the industry, and new manufacturers continue to enter the market,” he says. “Now, there are many OCT options available.”
When using OCT for RNFL and macular scans, Dr. Chaglasian says the signal strength should be seven out of 10 or higher in order to assure a high-quality scan.
“Don’t hamper yourself by trying to interpret bad information,” he says. “Movement throws off all the measurements and can lead to misreading scans.”
If you see pink or red, you think it’s a disease-but it may be just a poor quality scan, says Dr. Chaglasian.
ODs should also take the time to analyze the optic disc.
“Optic disc analysis is important, and time should be spent evaluating the deviation map,” he says. “Red and yellow coloring indicate thinning.”
On top of optic disc analysis, measuring the thickness of the ganglion cell layer can also be helpful.
“When the RNFL correlates with the ganglion cell analysis, I am most confident that the scan is true,” says Dr. Chaglasian. “This helps me be sure of the defect the patient has.”
But ganglion cell analysis shouldn’t be used alone in diagnosing glaucoma; it also doesn’t work if the patient has diabetes.
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Visual field testing
Central 10-2 testing remains an essential exam component says Dr. Chaglasian.
“Indications are we need to perform VF testing more frequently on patients than we currently do,” he says.
Central field testing is important because patients who experience central field loss experience:
• Decreased reading speed and errors
• Altered driving ability due to trouble reading signs
• Increased risk of falls
Progression analysis is observing the patient over time and monitoring the changes in the eye.
“Mapping things out on a trend analysis plot is the best way to track a patient’s progression,” says Dr. Chaglasian. “This is why the more VF, despite your patients’ resistance, can be more helpful.”
In the end, Dr. Chaglasian says ODs must exhaust all options in their toolboxes when it comes to treating each patient individually.
“We need to individualize the care for our patients,” he says. “We must find out which patients are going to do worse and treat them aggressively.”
