Unique emulsion eye drop restores lipid layer

New lubricant eye drops (Soothe XP Emollient Eye Drops, Bausch & Lomb) were specifically formulated to address lipid deficiency in the tear film, which is a critical factor in most patients with dry eye disease.

Key Points

Boston-Lubricant eye drops (Soothe XP Emollient Eye Drops, Bausch & Lomb) replenish the tear film with both moisture and lipids and can provide long-lasting symptomatic relief to patients with dry eye disease, said Donald R. Korb, OD.

Dr. Korb, one of the inventors of the lubricant emulsion formulation found in the eye drops (formerly Soothe by Alimera Sciences), explained that it was created based on the recognition that lipid deficiency is a primary underlying factor for dry eye disease in most patients.

"The advent of interferometry allowed measurement of lipid layer thickness in the precorneal tear film and led to the appreciation that lipid abnormalities associated with meibomian gland dysfunction, and not aqueous deficiency, is the key culprit in the development of dry eye disease," said Dr. Korb, an optometrist in private practice in Boston and director of research, Ocular Research of Boston. "Lipids in the tear film provide lubricity and a barrier against moisture loss. In fact, multiple studies in peer-reviewed journals report a 4- to 16-fold increase in aqueous evaporative loss in the presence of a lipid-deficient tear film."

"The dual surfactant system incorporated in [the eye drops] allows the neutral oil to spread quickly into a planar, protective film and adhere to the aqueous layer," said Dr. Korb, who also is clinical professor, School of Optometry, University of California, Berkeley, and a trustee at the Schepens Eye Research Institute, Boston. "A drop of [the emollient] distributes evenly over the ocular surface, and quickly. Therefore, within 10 to 20 seconds after instillation, patients are not bothered by any significant blur."

Interferometry studies show that as soon as the eye drops are instilled, the lipid and aqueous components of the tear film increase, resulting in a dramatic rise in lubricity.

"Lubrication is one of the key functions of the tear film, and when it is inadequate, friction between the 'wiper' region of the upper lid and the ocular surface during a blink can cause mechanical damage to those tissues," Dr. Korb said.

"The ocular surface damage is associated with complaints of ocular burning, but 'lid wiper epitheliopathy,' a term I coined to describe the damaged upper lid tissue, is the source of symptoms of scratchiness and grittiness," he said. "[The eye drops do] a remarkable job in relieving the latter complaints and should be considered the artificial tear of choice in any patient with prominent foreign body-type symptoms."

By restoring the tear film with both moisture and lipid, and preventing evaporative loss, the eye drops can have a long-lasting effect. Although the duration of benefit is variable, patients often achieve 4 to 8 hours of relief.

Clinical study results demonstrate the activity of the eye drops for increasing tear film lipid layer thickness in patients with dry eye symptoms and thin lipid layers. In head-to-head studies, the eye drops were shown superior to competitor products, including a drop with 1% glycerin and 1% polysorbate 80 (Refresh Dry Eye Therapy [formerly Refresh Endura], Allergan) and a drop with polyethylene glycol 400, propylene glycol, and hydroxypropyl guar (Systane, Alcon Laboratories). In patients whose dry eye responded to loteprednol etabonate (Lotemax, Bausch & Lomb) but who could not be tapered off, the addition of the new eye drops enabled discontinuation of the corticosteroid after 1 to 2 months.