Several recent eye research projects have addressed the potential of contact lenses as a way to (a) deliver ocular drugs directly to the eye, (b) measure blood glucose levels, and (c) monitor intraocular (within the eye) pressure. Two prominent examples are the FDA-approved Triggerfish contact lens, which monitors intraocular pressure related to glaucoma, and Google’s prototype “smart contact lens”, proposed as a way to monitor blood glucose levels for people with diabetes.
Now, researchers from Harvard Medical School and the School of Medicine at Mount Sinai, New York have developed a contact lens – using animal models – to deliver eye pressure-lowering glaucoma medication, with the goal of preventing vision loss. Currently, most glaucoma medications are administered as eye drops, which can cause stinging and burning, be difficult to self-administer, and thus are associated with low compliance.
Please note: Although this glaucoma research has produced interesting results in laboratory animals thus far, it must be subjected to additional, longer-term, rigorous study and human clinical trials, encompassing many more years of research.
From the Journal Ophthalmology
This latest glaucoma contact lens research, entitled Latanoprost-Eluting [i.e., extracting or dissolving the drug latanoprost] Contact Lenses in Glaucomatous Monkeys, has been published online ahead of print in the August 29, 2016 edition of Ophthalmology, the official journal of the American Academy of Ophthalmology. Ophthalmology publishes original, peer-reviewed research in ophthalmology, including new diagnostic and surgical techniques, the latest drug findings, and results of clinical trials.
The authors are Joseph B. Ciolino, MD; Amy E. Ross, MSc; Rehka Tulsan, MSc; Amy C. Watts, OD; Rong-Fang Wang, MD; David Zurakowski, PhD; Janet B. Serle, MD; and Daniel S. Kohane, MD, PhD, who represent the following institutions: Massachusetts Eye and Ear Infirmary and Boston Children’s Hospital, Harvard Medical School, Boston, MA; and the Icahn School of Medicine at Mount Sinai, New York, NY.
Latanoprost and Prostaglandin Analogs: Eye Drops for Glaucoma
Prostaglandin analogs are the most widely prescribed eye drops. Prostaglandin is a naturally-occurring blood protein that can lower intraocular [i.e., within the eye] pressure (IOP), in addition to having many other therapeutic effects.
Analogue, or “analogous,” means that the drug is comparable, or similar, to prostaglandin, but has a slightly different chemical composition.
Thus, prostaglandin analogues (PGAs) are drugs that are used in the treatment of open-angle glaucoma or ocular hypertension. At specific dosages, they lower intraocular pressure (IOP) by increasing the outflow of aqueous humor from the eye.
Some of the more common PGAs include
- Xalatan (generic name: latanoprost)
- Travatan (generic name: travoprost)
- Lumigan (generic name: bimatoprost)
- Zioptan (generic name: tafluprost)
About the Glaucoma Contact Lens Research
Edited and excerpted from Drug-dispensing contact lens effectively lowers eye pressure in pre-clinical glaucoma model, via the Massachusetts Eye and Ear Newsroom:
A contact lens designed to deliver medication gradually to the eye could improve outcomes for patients with conditions requiring treatment with eye drops, which are often imprecise and difficult to self-administer. A team of researchers has shown that a novel contact lens-based system, which uses a strategically placed drug polymer film to deliver medication gradually to the eye, is at least as effective, and possibly more so, as daily latanoprost eye drops in a pre-clinical model for glaucoma.
“We found that a lower-dose contact lens delivered the same amount of pressure reduction as the latanoprost drops, and a higher-dose lens, interestingly enough, had better pressure reduction than the drops in our small study,” said [study co-author] Joseph B. Ciolino, M.D. “Based on our preliminary data, the lenses have not only the potential to improve compliance for patients, but also the potential of providing better pressure reduction than the drops.”
Contact lenses have been studied as a means of ocular drug delivery for nearly 50 years, yet many such lenses are ineffective because they dispense the drug too quickly. The authors of the Ophthalmology study designed the contact lens to allow for a more controlled drug release. The researchers had shown in a previous study that the lens is capable of delivering medication continuously for one month.
The researchers designed a contact lens that contains a thin film of drug-encapsulated polymers in the periphery [i.e., the outer edges]. The drug-polymer film slows the drug coming out of the lens. Because the drug film is on the periphery, the center of the lens is clear, allowing for normal visual acuity, breathability, and hydration. The lenses can be made with no refractive power or with the ability to correct the refractive error in nearsighted or farsighted eyes.
… the effect of this drug-eluting contact lens was assessed in four monkeys with glaucoma. The researchers showed that the contact lens with lower doses of latanoprost delivers the same amount of eye pressure reduction as the eye drop version of the medication. The lenses delivering higher doses of latanoprost had better pressure reduction than the drops.
Further study is needed to confirm the finding in the higher-dose lenses. The researchers are currently designing clinical trials to determine safety and efficacy of the lenses in humans.
More About Glaucoma
The term “glaucoma” describes a group of eye diseases that can lead to blindness by damaging the optic nerve. It is one of the leading causes of vision loss and blindness. The human eye continuously produces a fluid, called the aqueous, that must drain from the eye to maintain healthy eye pressure.
Types of Glaucoma
In primary open-angle glaucoma, the most common type of glaucoma, the eye’s drainage canals become blocked, and the fluid accumulation causes pressure to build within the eye. This increasing pressure can cause damage to the optic nerve, which transmits information from the eye to the brain. Vision loss is usually gradual and often there are no early warning signs.
In angle-closure glaucoma, also called “acute” glaucoma, the aqueous cannot drain properly because the entrance to the drainage canal is either too narrow or is closed completely. In this case, eye pressure can rise very quickly and cause an acute glaucoma attack. Symptoms can include sudden eye pain, nausea, headaches, and blurred vision. Acute glaucoma is a true ocular emergency and requires immediate treatment.
In normal-tension glaucoma, also called low-tension/low pressure glaucoma, individuals with the disease experience optic nerve damage and subsequent vision loss, despite having normal intraocular [i.e., within the eye] pressure (IOP).
Most eye care professionals define the range of normal IOP as between 10 and 21 mm Hg [i.e., millimeters of mercury, which is a pressure measurement]. Most persons with glaucoma have an IOP measurement of greater than 21 mm Hg; persons with normal-tension glaucoma, however, have an IOP measurement within the normal range.
Visual Field Loss
Glaucoma results in peripheral (or side) vision loss initially, and the effect as this field loss progresses is like looking through a tube or into a narrow tunnel. This constricted “tunnel vision” effect makes it difficult to walk without bumping into objects that are off to the side, near the head, or at foot level.
A living room viewed through a constricted visual field.
Source: Making Life More Livable. Used with permission.
Glaucoma is an especially dangerous eye condition because most people do not experience any symptoms or early warning signs at the onset. Glaucoma can be treated, but it is not curable. At present, the damage to the optic nerve from glaucoma cannot be reversed.
You can learn more about the different treatments for glaucoma, including laser peripheral iridotomy (LPI), selective laser trabeculoplasty (SLT), and eye drops to lower eye pressure, on the VisionAware website.
Complying with Your Eye Medication Regimen
If you have been diagnosed with glaucoma, it is critical that you maintain the eye medication regimen prescribed by your ophthalmologist. In order for the medication to lower your intraocular pressure effectively, consistent daily adherence to your prescribed eye drop regimen is essential.
At times, compliance can be difficult because there can be some discomfort when administering your eye drops. If you have ongoing problems, such as pain, blurred vision, or headaches after taking your drops, talk to your doctor about using another type of eye drop.
Here is a set of helpful steps for administering drops, developed by The National Eye Institute:
- Wash your hands.
- Tilt your head back.
- Hold the bottle upside down.
- Hold the bottle in one hand and place it as close as possible to your eye.
- With the other hand, pull down your lower eyelid. This forms a “pocket.”
- Place the prescribed number of drops into the lower eyelid pocket. If you are using more than one eye drop, be sure to wait at least five minutes before applying the next eye drop.
- Close your eye or press the lower lid lightly with your finger for at least one minute. Either of these steps keeps the drops in the eye and helps prevent the drops from draining into the tear duct, which can increase your risk of side effects.
For additional tips, adaptations, and assistive devices to help you take your glaucoma medications, see Tips for Taking Glaucoma (and Other) Eye Drops by Ira Marc Price, O.D.
More About the Study from Ophthalmology
From the study summary and abstract:
Purpose: To assess the ability of latanoprost-eluting contact lenses to lower the intraocular pressure (IOP) of glaucomatous eyes of cynomolgus monkeys [i.e., macaques].
Participants: Female cynomolgus monkeys with glaucoma induced in 1 eye.
Methods: Latanoprost-eluting low-dose contact lenses and high-dose contact lenses were produced by encapsulating a thin latanoprost-polymer film within the periphery of a methafilcon hydrogel, which was lathed into a contact lens. We assessed the IOP-lowering effect of low-dose contact lenses, high-dose contact lenses, or daily latanoprost ophthalmic solution in the same monkeys.
Each monkey consecutively received 1 week of continuous-wear low-dose contact lenses, 3 weeks without treatment, 5 days of latanoprost drops, 3 weeks without treatment, and 1 week of continuous-wear high-dose contact lenses. On 2 consecutive days before initiation of each study arm, the IOP was measured hourly over 7 consecutive hours to establish the baseline IOP.
Results: Latanoprost ophthalmic solution resulted in IOP reduction of 5.4±1.0 mmHg [i.e., millimeters of mercury, which is a pressure measurement] on day 3 and peak IOP reduction of 6.6±1.3 mmHg on day 5. The low-dose contact lenses reduced IOP by 6.3±1.0, 6.7±0.3, and 6.7±0.3 mmHg on days 3, 5, and 8, respectively. The high-dose contact lenses lowered IOP by 10.5±1.4, 11.1±4.0, and 10.0±2.5 mmHg on days 3, 5, and 8, respectively.
For the low-dose contact lenses and the high-dose contact lenses, the IOP was statistically significantly reduced compared with the untreated baseline at most time points measured. The high-dose contact lenses demonstrated greater IOP reduction than latanoprost ophthalmic solution on day 3 (P = 0.001) and day 5 (P = 0.015), and at several time points on day 8 (P < 0.05).
Conclusions: Sustained delivery of latanoprost by contact lenses is at least as effective as delivery with daily latanoprost ophthalmic solution. More research is needed to determine the optimal continuous-release dose that would be well tolerated and maximally effective. Contact lens drug delivery may become an option for the treatment of glaucoma and a platform for ocular drug delivery.
More About Glaucoma at VisionAware
- For more detailed and patient-centered information about glaucoma detection, treatment, and everyday management, see VisionAware’s Patient’s Guide to Living with Glaucoma and Guía del Paciente: Vivir con Glaucoma.
- How Can We Improve Compliance with Glaucoma Medication Regimens? New Research Advocates Team-Based Care, Similar to Diabetes on the VisionAware blog
- Maintaining a Glaucoma Medication Regimen: What Factors Do – or Don’t – Promote Adherence? on the VisionAware blog