New look at putting the lid on those dry eyes

Image courtesy of m_bartosch / FreeDigitalPhotos.net

Australian scientists have developed a simple test of eyelid sensitivity to help vision specialists to evaluate the extent of dry eyes, and give appropriate treatment.

Their study appears in a recent issue of the journal, Optometry and Vision Science.

Measuring Sensitivity

Dr Isabelle Jabert and colleagues at The University of New South Wales, in Sydney, used a test called esthesiometry to measure the sensitivity of the eyelid margins - the very edge of the upper and lower eyelids, in a pilot study that included 27 healthy adults, with an average age of 31.

The test, easily performed in an optometrist or ophthalmologist's rooms, is able to provide an accurate measure of the lid margin's sensitivity to touch, say the researchers.

They looked at how eyelid sensitivity was related to the function of specialised structures of the eyelid margin. A special dye was used to stain the innermost layer of the eyelid margin to assess the function of the meibomian glands, which secrete a specialised oil-like substance into the tear fluid.

Surprising results

The results showed some surprising differences between the upper and lower eyelids - including greater sensitivity of the lowerlid margin, compared to the upper lids, Jabert says.

It was this increased lower lid sensitivity that was found to be related to hyperosmolarity of the tear film - that is, more concentrated tears, she says.

The finding suggests the potential for a new approach to effective treatment that lies in assessing tear osmolarity (concentration of tear fluid) via lower lid sensitivity measures clinically.

Whereas past studies have shown a relationship between corneal sensitivity and osmolarity, none has addressed the possible lid sensitivity relationship.

"The ease with which the nontransparent lids can be accessed to measure sensitivity provides a potential clinical advantage over measuring sensitivity to touch on the cornea," Jabert says.

Ambiguous relationship

By comparison, the relationship between tear osmolarity and staining appears much more ambiguous, she says.

The authors' results emphasise clear differences in staining and sensitivity between the upper and lower lids; for example the upper lids appear to be less sensitive and they stain less.

Such findings may turn out to be important for interpretation of future studies of the dry eye condition.

Increased osmolarity and decreased meibomian gland function have both been linked to symptoms related to dry eye. The meibomian gland is one of the long sebaceous glands of the eyelids that discharge a fatty secretion which lubricates the eyelids.

Recent research has led to increased understanding of the delicate structure and function of lid margin, and their contribution to common eye-related symptoms, say specialists.

Renewed interest

Dr Anthony Adams, editor-in-chief of Optometry and Vision Science, says this has renewed interest in the role of the eyelids in dry eye and meibomian gland dysfunction.

The new results suggest that esthesiometry could provide optometrists with a simple test of lid margin sensitivity, providing evidence of tear osmolarity, Adams says.

"This suggests a promising tool for evaluating ocular health and effectiveness of treatment in dry eye disease and meibomian gland dysfunction."

The findings may provide "an expanded set of tools" for identifying problems leading to dry eye, and possibly for evaluating the effectiveness of new treatments, Adams says.

Prosthetic treatment

For severe cases of dry eye, that can result from cancer or complex corneal disease, a new treatment is prosthetic replacement of the eye's surface "ecosystem".

US ophthalmologist Dr Karen DeLoss, of the University of Michigan Eye Centre, works with cornea specialists to identify patients who can benefit.

Typically patients have been told nothing more can be done for them, DeLoss says. Prosthetic replacement of the ocular surface ecosystem is a "welcome option".

During treatment, she creates a custom-made removable prosthetic device that continuously bathes the eye in artificial tears.

It rests on the sclera - the white of the eye - and is composed of material that allows oxygen to reach the cornea. It creates a smooth surface over the damaged cornea; the artificial tears provide lubrication, and support transfer of a healthy supply of oxygen to the cornea; the device supports healing, and reduces disabling pain and light sensitivity, says DeLoss.

Source: Business Day / Newswise