Contact Lens may Predict Glaucoma Progression

• Glaucoma is the leading cause of blindness around the world.
• It is associated with raised intraocular pressure and optic nerve damage.
• A smart contact lens may be able to track the changes in intraocular pressure.
• The lens can help determine response to treatment and progression of the disease.

Glaucoma is a condition of the eyes in which there is a build-up of pressure inside the eye. The increased intraocular pressure (IOP) eventually damages the optic nerve, causing loss of vision and complete blindness if not treated. IOP is the only controllable risk factor for the condition. Now, with the creation of a smart contact lens, it may be possible to keep a continuous track of the change in intraocular pressure in these patients, as revealed by a study titled ‘Visual Field Change and 24-Hour IOP-Related Profile with a Contact Lens Sensor in Treated Glaucoma Patients’ published in the journal Ophthalmology .

Researchers from Columbia University Medical Center have shown that the use of a smart contact lens can help in predicting the progression of the disease by interpreting electronic signals from the device.

Forty patients with open angle glaucoma (most common type of glaucoma) between the age of 40 to 89 years were selected. Eight standard visual field tests were conducted on the patients over the course of two years and accordingly, patients were categorized into slow progression (20) and fast progression (20) categories. Thereafter, all the patients were made to wear Sensimed Triggerfish Sensor lenses all through the day and night. Electronic signals from the lenses were measured and it was observed that patients who recorded steep spikes overnight and a higher number of peaks overall, were the ones who belonged to fast disease progression group. This revealed that intraocular pressure-related parameters obtained over 24 hours with a contact lens sensor (CLS) were associated with the rate of visual field changes in glaucoma patients.

Intraocular Pressure (IOP) and Glaucoma

A fluid known as aqueous humor is continuously produced and circulated in the human eye. This fluid is responsible for maintaining the shape of the eye and providing nutrition to the lens and cornea as they do not have their own blood supply. This fluid drains out of the anterior chamber of the eye through a meshwork. In the case of a disruption of this outflow, pressure builds up within the eye.

The normal IOP is between 10 and 21 mm Hg. In most cases of glaucoma, the pressure is greater than 21 mm Hg.

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The rising pressure damages the optic nerve and causes loss of peripheral vision, known as ‘’tunnel vision’’ and eventually total blindness. Glaucoma cannot be cured but treatment stops the progression of the disease. Since IOP is the only controllable risk factor, it is measured regularly by the treating ophthalmologist. It is however seen that IOP greatly fluctuates with time and shows diurnal variations as well.

How the Smart Lens Works?

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The smart contact lens is a soft contact lens made up of hydrophilic plastic (material which absorbs water) and is worn by the patient throughout the day and night for 24 hours. Using biosensors, it detects changes in the curvature of the cornea which are proportional to the fluctuations in intraocular pressure. An electrical signal is sent through an antenna to a recorder worn around the patient’s neck. This data can be transferred wirelessly to the doctor’s computer using Bluetooth. This gives the medical professional a record of changes in the IOP over time, much like an ECG for the heart. The device does not measure the intraocular pressure but tracks the changes in IOP over a course of time.

As it was observed in the study, the patients with fast progressive disease showed greater spikes at night and overall higher number of peaks, the smart lens may help in quick identification of patients who are at higher risk of disease progression by mapping the fluctuations.

It can also help in evaluating whether the current treatment modality being used in a patient is showing the desired improvement or not and decision may be taken to continue or alter the regime.

C. Gustavo De Moraes, MD,MPH, the study author and professor at the Columbia University said, “This could be very useful if you want to know whether a new medication is working for a patient. You can see how their eye is reacting to the therapy in a much more meaningful way.’’

FDA Approval

FDA (Food and Drug Administration) has approved the marketing of the Triggerfish Sensor, as a device to be used for sensing the optimal time to check a patient’s intraocular pressure. It was allowed, as FDA found an effective correlation between the device’s output and fluctuations in intraocular pressure.

The approval is through the regulator’s de novo premarket review pathway, a pathway for certain low to moderate risk medical devices which are not equivalent to an already legally marketed device.

It has been emphasized that the device does not measure IOP and is not diagnostic in nature.

The device has only been approved for use in patients over 22 years of age under the supervision of a certified healthcare professional.

Certain side effects such as pressure marks from the lens, ocular hyperemia (redness of the eyes) and punctate keratitis (corneal irritation) were noted. These side effects are temporary in nature.

This is a major landmark in the treatment of glaucoma and promises hope that soon, the lens will be able to effectively monitor glaucoma patients and guide healthcare professionals in choosing treatment modalities according to the individual patient.

References

http://www.aao.org/eye-health/news/smart-contact-lens-glaucoma-patients

http://www.visionaware.org/blog/visionaware-blog/the-fda-approves-marketing-of-the-triggerfish-smart-contact-lens-sensor-to-monitor-glaucoma-eye-pressure-2338/12

Source-Medindia