A Medical Device Daily

ATLANTA – At the annual meeting of the American Academy of Ophthalmology (AAO; San Francisco), which ended yesterday, a group of researchers at Vanderbilt Eye Institute (Nashville, Tennessee) reported on a potential biomarker for age-related macular degeneration (AMD) that may also imply common biological signaling mechanisms for general aging and AMD.

Another presentation during the meeting, which is the world's largest gathering of eye physicians and surgeons, reported positive results in keratoconus patients treated with a promising new technique known as corneal collagen crosslinking.

Janice Law, MD, and her colleagues at Vanderbilt Eye Institute looked for plasma biochemical markers that would indicate systemic oxidative stress and an inflammatory response in 57 patients with AMD and in an age-matched control group.

In its advanced stages, AMD destroys the detailed, central vision needed to read, drive, recognize faces and enjoy daily life, and is a major cause of vision loss in the U.S.

Law's study group found that an inflammation-promoting biochemical, interleukin 6 (IL-6), was found to be significantly higher in the AMD patients, and IL-6 levels also correlated with oxidative stress measurements in these patients.

They said this suggests that IL-6 is a good candidate for further study as a potential AMD biomarker. It also indicates that common biological signaling mechanisms may be involved in both oxidative stress and inflammation and may contribute to AMD development as well as general aging.

Other recent research has established that AMD is closely associated with certain genetic variations that control aspects of the immune system, especially the inflammatory response. Numerous studies also have confirmed the role of oxidative stress in AMD development and progression.

Law's study focused on plasma-based biomarkers because blood sample screening is a relatively simple yet accurate diagnostic tool. This preliminary cohort study did not attempt to determine whether IL-6 levels varied with AMD types — "wet" AMD, characterized by rapid growth of abnormal blood vessels and heightened risk of vision loss, or the more common "dry" type — or with disease severity.

In another study, co-investigators Mohan Rajan, MD, and Sujatha Mohan, MD, of the Rajan Eye Care Hospital in India, studied collagen crosslinking in 48 patients (60 eyes), aged 12 to 48 years, who had progressive keratoconus.

The collagen crosslinking technique, developed in recent years, is under study for the treatment of several eye disorders. When the technique is used to treat keratoconus patients, drops containing riboflavin, a B-complex vitamin, are applied to the cornea and then the cornea is exposed to UVA light, which stimulates collagen fibers to connect to one another, or crosslink.

The procedure helps restore appropriate curvature and structure to the cornea, and makes it possible for most patients who need them to wear rigid contact lenses again. AAO said collagen crosslinking may prove to be a viable alternative to cornea transplant, and three FDA-approved trials are now under way in the U.S.

Keratoconus is an eye disorder that causes corneal tissue to become abnormally thin and the central area to protrude in a cone shape, distorting vision. In the U.S., keratoconus occurs in 50 to 200 per 100,000 people. The AAO said unofficial reports indicate this disorder may be more prevalent in the Indian subcontinent, Arabia and New Zealand.

In the Rajan-Mohan study, the epithelium (top layer of tissue) was debrided in 40 eyes (group A), while in 20 eyes (group B) the epithelium was left intact prior to treatment. Patients received follow-up exams at one, three, six and 12 months.

Vision corrected with eyeglasses or contact lenses improved in 45% of patients by six months, but no change was noted in any patients' vision when measured without eyeglasses or contact lenses. The corneal curve flattened appropriately in 51 of 60 eyes (85%), with more significant flattening in group A patients. Based on subjective reports, 46.6% of participants were better able to tolerate wearing contact lenses. No significant side effects were noted.

"In our study, collagen crosslinking showed promising results," said Mohan. "The positive corneal changes observed in these patients, together with improved vision and contact lens tolerance, indicates that it was a safe and effective procedure for these keratoconus patients."

AAO said that as a less-expensive, technically simpler procedure, collagen crosslinking could be particularly useful in developing countries where corneal transplant and other procedures may be difficult to access.

Also at AAO, a study that correlates optic nerve damage in glaucoma patients with carotid artery narrowing and potentially elevated risk for stroke was reported by Mostafa Elgohary, MD, of Essex County and Broomfield Hospitals in the UK.

Glaucoma often is associated with elevated pressure inside the eye (intraocular pressure, or IOP), which can damage the optic nerve, leading to vision loss and even blindness.

Elgohary and his colleagues were concerned when several patients who had been under their care for several years continued to lose their vision in one or both eyes even though their IOP had been kept within normal limits either through medicine or surgery.

The authors reviewed 16 retrospective case reports to determine if there was a possible association of internal carotid artery stenosis, with the development of glaucoma or glaucoma-like damage to the optic nerve.

On further investigation, the researchers found that six of those patients had significant carotid artery narrowing (greater than 60% of the artery lumen) and some even had total blockage of the artery on the same side as the eye with the glaucoma, or on both sides. One patient showed improvement in the visual field after undergoing surgery to remove the blockage.

The group then extended the investigation by prospectively collecting data for 58 patients who were referred with similar optic nerve or visual field changes and carotid artery stenosis as part of the hospital audit system and found that 17% of these patients had significant carotid artery narrowing.

The AAO said the UK study results "add to the evidence for the role of reduced blood flow to the optic nerve as a possible cause or predisposing factor for glaucoma or glaucoma-like optic nerve damage." Moreover, the results indicate a possible association with significant carotid artery narrowing which is a potentially serious condition as it carries the risk of stroke.

"The study is of a small scale and will obviously need further research to confirm the findings," the researchers said. "However, in the meantime it may be prudent to consider referring patients with progressive or asymmetric glaucoma despite normal eye pressure — especially in the presence of cardiovascular risk factors such as hypertension, hypercholesterolemia or ischemia heart disease — for carotid artery Doppler scan to pick up those who could be at high risk for stroke and may benefit from carotid artery treatment."