Dry Eye Dx and Tx
Liposome Technology is Changing Dry Eye Therapy
BY KATHERINE M. MASTROTA, MS, OD, FAAO
The “Father of Liposomes,” hematologist Alec Bangham, died in March of this year. He is best known for research on what he called “multilamellar smectic mesophases.” He found that pure phospholipids dispersed in water consist of sets of closed membranes, structurally and functionally like real cell membranes. “Liposomes” now defines the microscopic vesicles composed of one or more lipid bilayers that mimic cell membranes.
Liposomes are self-closed colloidal (a type of mixture in which one substance is dispersed evenly throughout another) particles in which membranes composed of one or more lipid bilayer(s) encapsulate a fraction of the aqueous solution in which they are suspended. Liposomes usually contain a core of aqueous solution. The surfaces of bilayers are hydrophilic while the interior of bilayers are hydrophobic.
Because of the different microenvironments in their structure, liposomes can encapsulate hydrophilic molecules, bind molecules on the bilayer surfaces, or dissolve hydrophobic molecules into the middle of the bilayer. Their ability to incorporate many types of molecules lends liposomes to numerous uses as biochemical and biophysical tools.
Liposomes, as vehicles for delivery of both water- and of oil-soluble materials to cells, have been applied in drug delivery, diagnostics, cosmetics, cosmeceuticals, and nutraceuticals. To deliver the molecules, the lipid bilayer fuses with other bilayers such as cell membranes, allowing delivery of the liposome contents.
Figure 1. A liposome for drug delivery.
Liposomes and Dry Eye
It is commonly accepted that the integrity of the tear film's lipid layer must be maintained for clear vision and ocular surface maintenance. Therapies for patients who have a reduced or abnormal tear film are targeted at improving meibomian gland health. Another strategy is to add lipid to the tear layer via artificial tear lipid emulsion drops such as Soothe XP (Bausch + Lomb) and Refresh Dry Eye Therapy (formerly Endura, Allergan).
Liposome technology can also add lipid to the tear film via spray delivery. Sprayed onto a clean, closed eyelid, lipid-containing liposomes migrate from eyelashes and lid margins onto the tear film. Such migration occurs with virtually any product designated for eyelids. Studies demonstrate that liposome delivery of lipid to the tear film is comfortable and effective in increasing lipid layer thickness and tear film stability.
Tears Again Advanced liposome spray (Ocusoft) is available in the United States. Others include Eyelogic Eye Spray (Savant, United Kingdon), Optrex Actimist (Reckitt Benckiser, UK), and Tears Again (Optima Pharmaczeutische, Germany, not the same as Tears Again Advanced).
Another Treatment Option
Liposome technology offers another option for evaporative dry eye surface therapy. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #177.
Dr. Mastrota is secretary of the newly formed Ocular Surface Society of Optometry (OSSO). She is center director at the New York Office of Omni Eye Services and is a consultant to Allergan, AMO, B+L, Inspire, Noble Vision, and Cynacon Ocusoft. You can reach her at email@example.com.