Charting new directions in glaucoma treatment
Ben Gaddie, OD, FAAO, Optometry Times Editorial Advisory Board member, noted several specific areas that were advancing to give ODs better data and better control over patient health outcomes, including: • Corneal mechanics • 24-hour IOP monitoring • New glaucoma drugs and drug delivery systems • Advancements in OCT imaging
Las Vegas-Despite the efficacy of traditional glaucoma monitoring tools, the optometric profession is expanding to encompass a broader range of treatment options for patients with glaucoma, according to one expert at a recent lecture at Vision Expo West 2016.
Related: ECPs don't treat glaucoma aggressively enough
Ben Gaddie, OD, FAAO, Optometry Times Editorial Advisory Board member, noted several specific areas that were advancing to give ODs better data and better control over patient health outcomes, including:
• Corneal mechanics
• 24-hour IOP monitoring
• New glaucoma drugs and drug delivery systems
• Advancements in OCT imaging
Related: Affording OCT in your practice
Corneal mechanics and hysteresis
Traditional glaucoma monitoring involves intraocular assessments through serial tonometry, optical tomography, and visual field testing. Although effective, these methods have several drawbacks that are currently being addressed.
Related: The importance of pachymetry and CCT
Dr. Gaddie suggests that ODs rethink the validity of the Goldmann IOP test due to the corneal thickness effect.
“Different corneas need different amounts of force, independent of pressure inside the globe of the eye, in order to get the measurement,” he says. “Therefore, a lot of the measurements we take are artifact, and we really can’t draw good clinical decisions from them.”
As practitioners know, the time latency between the inbound measurement peak and the outbound measurement peak of the non-contact tonometer (NCT) is known as corneal hysteresis.
Dr. Gaddie says that corneal hysteresis is not significant when measured on its own, but becomes important when assessed alongside other factors.
“Low hysteresis is very predictive of patients who will have progressive glaucoma,” he says, “and by a factor of three, more predictive than corneal thickness by itself. The combination of hysteresis and corneal pachymetry gives me a lot of information about a patient’s risk for glaucoma.”
Gaining more data through these research methods can help ODs draw the line between glaucoma diagnoses and glaucoma suspects.
Nocturnal and 24-hour IOP measurement
A continuing challenge is managing patients’ IOP at night. Even when glaucoma therapies show success during the day, the lack of pressure control overnight can worsen patient health outcomes. IOP raises by as much as 20 percent overnight when compared to daytime measurements. Most common glaucoma drops are less efficacious while patients are asleep.
Related: New technology helps IOP measurement
New technologies are being developed to give practitioners the most comprehensive health data yet. Dr. Gaddie described one of these strategies, an FDA-approved contact lens called Triggerfish (Sensimed). This silicone hydrogel lens continuously measures a patient’s IOP each hour, checking pressures around 288 times per day. Such tools would give practitioners around-the-clock monitoring of IOP fluctuations and would be a valuable tool in decision making.
“This is an area that I think is one of the missing pieces to our puzzle, and I think we’re finally starting to get some information on it,” Dr. Gaddie says.
Glaucoma drugs and delivery
Drug classes for glaucoma therapy have remained fairly consistent over time:
• PGAs
• Docasnoids
• Beta blockers
• Alpha agonists
• Topical CAIs
• Combos
Related: New glaucoma drugs aim to shake up market
The biggest concern in glaucoma medication therapy is the divide between generic and brand name prescriptions.
Dr. Gaddie notes that the rates of optometrist-prescribed medications in general are on the rise, while ophthalmologists’ prescription rates are remaining stable.
“The market isn’t growing,” he says, “but there is a shift in the numbers of who is providing that care.”
However, while Dr. Gaddie notes that this increase is a welcome testament to the optometric professionals currently working to improve the industry, this rise in medication dispensing creates more challenges for ODs to overcome.
“They’re up to 13 or 14 different manufacturers of the generic,” says Dr. Gaddie. “I’m finding a lot of variability-meaning a patient will get this brand the first time, and I’ll check his pressure, it looks great, and three months later, he gest a refill and it will be a second brand. Then maybe a different brand a third time, and not all of them seem to be very consistent. Watch out for this,” he says.
Despite the challenging variability of generic prescriptions, their cost effectiveness makes them a necessary option, particularly for Medicare-insured and budget-conscious patients.
Combination drugs
Combination medication therapies are another trend currently making headway. These medications can be very practical, especially with glaucoma.
“If I know I need another IOP medication, the chances that I’ll need another one on top of that in short order is pretty high,” Dr. Gaddie says. “So why not get the pressure down in the most efficacious and efficient manner right out of the gate?”
Dr. Gaddie listed two new drugs currently awaiting FDA approval: Latanprostene bunod and Rho-associated protein kinase inhibitors.
“With that combined molecule, you’re hitting every mechanism of action of IOP control that you can have,” he says. “It’s going to be a blockbuster.”
Drug delivery
On the new frontier of new drug delivery systems, the methods getting the most attention are currently injectable and surgically implanted options.
In particular, Dr. Gaddie says that intravitreal injections and ocular insert rings have advantages of increased compliance and adherence so that patients don’t need to worry about putting in drops.
“Getting the patient away from having to put drops in on his own, and being compliant and adherent is the number one goal of future drug delivery,” he says.
Related: New technology could replace eye drops
OCT imaging
In OCT imaging, the retinal nerve fiber layer is a key structure observed; instruments today parse out the ganglion cell layer rather than the full retinal thickness. This provides more accurate readings of possible nerve defects or damages that may have occurred from glaucoma.
OCT can work as a congruency verification tool. Defects in certain macular areas lend themselves to central visual field defects, and that new imaging tools offer more complete imaging that may allow practitioners to get ahead of emerging problems.
“If I see a questionable RNFL defect that Im not 100 percent sure is glaucomatous, I look at the macula,” says Dr. Gaddie. “If both of those show damage and are congruent with each other, that gives me a lot of confidence that the damage is there.”
Related: Affording OCT in your practice
