New treatments, diagnostic methods and more.
No matter how much you think you know about glaucoma, there's always more to learn. Research is yielding new methods of detecting the disease as well as new products to help patients cope.
This month, we'll help keep you current with these new
developments that can benefit both your patients and your practice.
Low Blood Flow in Glaucoma
A look at measurability.
MURRAY FINGERET, O.D., F.A.A.O., Hewlett, N.Y.
Perhaps you've seen him -- the glaucoma patient who's doing poorly despite treatment. You can't find a reason for his worsening condition. His intraocular pressure (IOP) is low with drops, but his vision is still deteriorating.
|Because of all the uncertainty, some controversy exists over whether the perceived blood flow problem is real and, if it is, over how common it is as a cause of worsening glaucoma. But some pharmaceutical companies indicate that drugs such as unoprostone isopropyl ophthalmic solution 0.15%
(Rescula), dorzolamide HCl 2% (Trusopt) and betaxolol
(Betoptic) not only lower intraocular pressure, but also improve blood
Measuring optic blood flow
Some doctors think the cause of this patient's problem may be insufficient blood flow to the optic nerve. But if you've ever tried to measure this blood flow, you know that here's where practice hasn't yet caught up to theory.
The optic nerve has many sources of circulation, such as the choroidal circulation, large ophthalmic vessels such as the central retinal artery or retinal circulation. Right now, there's a controversy about how to measure the blood flow in any of these systems. The instruments are evolving, but are still a while away from common use in our practices. No one knows how to identify which of these systems is implicated in low blood flow. And no one knows which instrument to use, either.
What we have now
Of the instruments available to us today, not one of them measures all portions of the ocular blood flow system. Furthermore, no instruments exist to measure blood flow as opposed to blood velocity. And the data that our instruments yield are variable and difficult for us to repeat. The following is a list of some of the instruments that are available to us now.
- Paradigm Medical Industries' Blood Flow
Analyzer. This easy-to-use tool analyzes the pulse of intraocular blood pressure, rather than giving true blood flow measurements.
- Canon Medical System's CLBF-100 Laser Blood Flowmeter. This instrument claims to offer three types of data for each specified point on a retinal vessel: blood flow velocity; vessel diameter; and blood flow rate, but these claims, like others, aren't yet validated in the literature.
- The Heidelberg Retinal Flowometry System. Heidelberg's system measures retinal circulation, but is a research tool not for private practices.
- Color Doppler imaging. This technique measures ophthalmic artery blood velocity in vessels supplying the optic nerve. But no test validates a blood flow problem in the optic nerve.
- The metabolic mapper. Zeiss-Humphrey says that it will initiate multi-center clinical trials to explore the efficacy of a "metabolic mapper" that monitors the spatial distribution of oxygen concentration within retinal tissue.
This instrument represents the first noninvasive technology capable of determining the meta-bolic health of retinal tissue, therefore providing information that's diagnostically more valuable to doctors than measurements of retinal blood flow.
The metabolic mapper was developed and patented by Dr. Ralph Zuckerman, president of Biometric Imaging of Philadelphia. According to Dr. Zuckerman, the technology will produce color maps of the spatial distribution of oxygen concentration, allowing identification of regions of hypoxic tissue which may be caused by reduced blood flow. For glaucoma, the device should allow identification of the dying nerve fibers at early stages.
- Memantine. Allergan's memantine is under development as a potential neuroprotective drug. Currently in Phase III clinical trials, it's an n-methylD-aspartate blocker that prevents the re-uptake of glutamate (a neurotransmitter in the retina). Although it won't replace existing glaucoma drug regimens, it will augment them. Study of this drug will continue for several more years.
Puzzled about how to bill for nerve fiber analyzers?
See John McGreal's "Coding
Q & A" column in our April issue for answers.
Hope for the future
A scientific measure and validation of low blood flow is still a dream for the future. For now, if I suspect a blood flow problem in my glaucoma patient, I take a thorough history geared toward discovering systemic blood flow problems such as cold hands, tingling fingers, migraine head-aches, peripheral vascular disease and diabetes.
One day, however, I hope I'll be better equipped to quantify the problem.
Dr. Fingeret is chief of the Optometry Section at Brooklyn/St. Albans Campus, Department of Veterans Administration New York Harbor Health Care System. He's a member of the board of directors of the Glaucoma Foundation and is chair of the glaucoma diplomate committee for the American Academy of Optometry.
Treating glaucoma enhances your image.
BY DEEPAK GUPTA, O.D., Stamford, Conn.
Just recently, four new drugs have joined our
armamentarium against glaucoma. They are bimatoprost ophthalmic solution 0.03%
(Lumigan), travoprost ophthalmic solution 0.004% (Travatan), unoprostone isopropyl ophthalmic solution 0.15%
(Rescula) and brimonidine tartrate 0.15% (Alphagan P)
Managing glaucoma can help your practice in many ways. Not only will you gain respect from your patients for treating this complex, devastating disease, but you'll boost your practice income, as well. For each glaucoma patient you treat, you should yield a net revenue per year of $350 to $400 by performing the following necessary evaluations:
- visual fields
- 3- or 4-month intraocular pressure checks
- annual comprehensive eye examination
- annual retinal photos
- annual gonioscopy.
Many O.D.s are also adding nerve fiber analysis to the list of routine procedures performed for glaucoma and suspect patients. The reimbursement alone runs around $100.
As important as increasing your net is increasing the level of respect you'll earn from your patients as a doctor of optometry. When your patients view you this way, it will yield not only referrals for routine eye care but referrals for treating ocular diseases.
Dr. Gupta practices full-scope optometry at Stamford Ophthalmology.
Some tips on how to get your patients to take their meds.
BY DEEPAK GUPTA, O.D.
It's often been said that one of the most difficult aspects of treating glaucoma is patient noncompliance. Here are some ways I've found to increase compliance:
- Routinely prescribe beta-blockers b.i.d. If you prescribe them for q.d. and the patient isn't good about taking her drops, she'll get less than the therapeutic dose. But this same patient will get a reasonable dose if she takes it at least once. If you're concerned about possibly overdosing a patient, wait until she establishes a compliance pattern and take it from there.
- Tailor the drug regimen to the patient's schedule. With the newer medications on the market, you ought to be able to keep most patients at b.i.d. dosing. In my experience, most compliance issues arise when you try to do t.i.d. or q.d. dosing.
Patients find it difficult to instill drops during the day. Once your patient is on that q.d. or b.i.d. dosing, I've found it effective to suggest that he keep the bottle on his alarm clock. That way, when the alarm goes off in the morning, he can instill a drop before hitting the snooze button. At night, he'll remember to instill a drop when he resets the alarm.
- Assess therapy monocularly to determine the effects of a
drug. Intraocular pressure (IOP)
demonstrates diurnal variation. For instance, if a patient has IOPs of 28 mm Hg in each eye, you might start a beta-blocker. If the IOPs were 20 mm Hg in each eye at the IOP check in 2 weeks, you might think the medication had caused an 8 mm Hg drop.
Had you performed a monocular trial, however, you'd see that the day of the IOP check, the untreated eye had an IOP of 25 mm Hg due to normal diurnal fluctuations. So the medication alone wasn't responsible for the entire 8 mm Hg drop.
- Realize that recirculation of beta-blockers often causes a 10% to 20% drop in IOP in the untreated eye. Doctors hesitate to rely on this effect because they fear damaging the untreated eye by not starting drops. But glaucoma is a chronic, progressive disease. Waiting a couple of weeks to start treatment on an eye won't change the final clinical outcome.
- Give the patient a sample bottle when dispensing drops. Patients usually waste most of a trial bottle learning how to instill the drops, so it's a good practice builder to supply the drops while the learning curve takes place.
The other big advantage is that you can see them for a quick IOP check before the sample runs out. This will allow you to reassure the patient that the drops are working before he has to spend any of his own money filling the prescription.
- Have your patients manually occlude the nasolacrimal puncta. It doesn't directly boost compliance, but it does increase the effectiveness of the drops and decrease systemic side effects. If the patient can't do this because of lack of manual dexterity or for scheduling reasons, consider occluding his puncta with collagen punctal plugs.
The New Treatments
Experts discuss the changing therapeutics.
BY TERRI B. GOSHKO, Senior Associate Editor
New glaucoma treatments are poised to change the lives of doctors and patients alike. We wondered what doctors thought about the changes, so we asked these four experts:
||Randall Thomas, O.D., M.P.H., F.A.A.O.,in full-time clinical practice in Concord, N.C.
||J. James Thimons, O.D.,
Ophthalmic Consultants, a multi-specialty surgical practice, and TLC Laser
Center in Fairfield, Conn. He's also Optometric Management's clinical director.
||Chris Quinn, O.D., F.A.A.O., of Iselin, N.J., center director of Omni Eye Services of New Jersey, a multi-specialty ophthalmology/optometry referral-based practice.
||Bruce E. Onofrey, O.D. R.Ph., F.A.A.O., responsible for primary care eye services at Lovelace Medical Center, Montgomery Eye Clinic in Albuquerque.
Here are their insights.
QUESTION: Are beta-blockers still a useful treatment for glaucoma?
Dr. Thomas: For me, beta-blockers reign supreme as initial therapy for three reasons:
- We have the most experience with them of all the drug classes.
- They're the least expensive of the current medications.
- Using them once-a-day in the morning is enough.
About 40% to 50% of patients reach their target intraocular pressures (IOPs) with one drop. I use timolol hemihydrate (Betimol) because it's not generically substitutable, and it's less costly than other, branded beta- blockers.
Patients who have light irides need only one drop of 0.25% in the morning; those with dark irides may need one drop of 0.5%. Once-daily use reduces the potential for side effects. Beta-blockers can cause harm if taken at night because they can diminish diastolic blood pressure and starve the optic nerve.
Beta-blockers have been the mainstay of glaucoma treatment for 20 years, but they have side effects.
While they're still a cost-effective option for treating glaucoma, their use as first-line therapy is questionable now that latanoprost 0.005% (Xalatan), bimatoprost ophthalmic solution 0.03% (Lumigan), travoprost (Travatan) and unoprostone isopropyl ophthalmic solution (Rescula) are available to us.
I believe beta-blockers will continue to play a major role in treating glaucoma. Aqueous suppression is still necessary to reduce IOP to levels that prevent visual field loss.
Dr. Onofrey: Beta-blockers are still a cost-effective option if you pick patients carefully and monitor them for adverse reactions. About 12% of patients will tell you that they have a condition that
contra-indicates beta-blockers; another 12% will develop an adverse reaction and need to be switched. But beta-blockers are still excellent.
New guidelines are important: Start with 0.25% once a day (morning only), monocularly. Cross-over effect may eliminate the need to treat the second eye.
Studies suggest reduced beta-blocker efficacy and increased risk of nocturnal ischemic events when beta-blockers are administered at night.
QUESTION: Have the new drugs changed your treatment approach?
Dr. Thomas: The new drugs are excellent. If they were price-competitive with beta-blockers, I'd likely use them as first-line for all patients. If my patient doesn't respond to a beta-blocker, I'll switch him to latanoprost, bimatoprost or travoprost. They've enhanced safety profiles and reduce IOP 2 mm Hg to 4 mm Hg more than a beta-blocker. All are approved as second-line therapy, but many doctors will use them first because they're such good products.
Dr. Thimons: I favor the new drugs as first-line therapy. Latanoprost has a proven track record for primary initial treatment.
In clinical trials, travoprost appeared to have a slightly better effect on African-American glaucoma patients, giving us new flexibility in treating them.
In trials against timolol, bimatoprost was twice as likely to significantly lower IOP, so this drug may be more useful for recalcitrant glaucoma.
The beauty of the new drug picture is that we can paint it with a broadened palette of colors and a more subtle stroke.
Dr. Quinn: With the expanded options, patients will benefit.
Prostaglandin analogs will especially help patients who didn't respond well to latanoprost. I also see an increasing trend toward medication substitution rather than the addition of more medications.
Dr. Onofrey: I favor latanoprost as first-line therapy for patients with moderate-to-advanced disease. It's convenient and effective, with minimal side effects. Because unoprostone, travoprost and bimatoprost are so new, they aren't on my formulary yet. But I look forward to trying them.
Optometric Management, Issue: May 2001