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An improved understanding of dry eye is leading to the development of several new technologies for diagnosing
and treating the condition, said Beatrice Cochener MD, PhD, University of Brest, France.
“Today we have a better understanding of the underlying mechanisms of ocular surface disease. We also have
greater consideration of the ocular surface as a key factor in visual performance and quality of life. Moreover, we
have new diagnostic tools for quantification of the ocular surface properties and we have innovative options for
the treatment of dry eye,” she told the 18th ESCRS Winter Meeting in Ljubljana.
Modern definitions of dry eye stress the multifactorial nature of the condition. Contributing factors include
increased osmolarity of the tear film and inflammation of the ocular surface, she said.
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Post-LASIK dry eye
Dry eye and ocular surface disease have gained renewed attention over recent years because of their high
incidence among patients who undergo corneal refractive surgery, Prof Cochener noted.
“The ocular surface is a key factor in vision and comfort. With modern refractive surgery we are close to
achieving real emmetropia in most patients and therefore the most common source of dissatisfaction nowadays
is related to the ocular surface,” she said.
Mild dry eye that is responsive to treatment with lubricants occurs in up to 50 per cent of LASIK patients. More
severe dry eye occurs in only 10 per cent of these patients. The condition results primarily from a combination of
neurogenic and inflammatory factors.
Flap creation and photoablation sever a large amount of corneal nerve fibres. The reduced sensitivity of the
ocular surface reduces blinking and the amount of tears produced. The decrease in the tear production in turn
increases the osmolarity of the tear film. That in turn causes an increased secretion of pro-inflammatory
cytokines and matrix-degrading enzymes into the tear film.
“All these factors lead to a level of inflammation that can directly damage the ocular surface epithelial cells and
prolong injury to the corneal nerves and thereby alter the lachrymal gland function leading to damage of the
ocular surface,” Prof Cochener said.
Meanwhile, the alteration of corneal shape alters tear film distribution and changes the relationship between the
ocular surface and the upper lid, increasing evaporative tear loss,
she added.
Prevention through diagnosis
Research has shown that preclinical signs of dry eye are often present in eyes that later develop post-LASIK dry
eye. It therefore behoves refractive surgeons to carry out an assessment of the health of the ocular surface prior
to carrying out the refractive procedure. Treatment and resolution of pre-existing ocular surface dryness may
reduce the risk of postoperative dry eye, Prof Cochener said.
There are a number of tests available to measure the various physiological aspects of dry eye. They include the
Schirmer’s test, the tear break-up time and lissamine green staining. However, those tests lack specificity with
regard to specific subsets of dry eye disease. They are also difficult to perform and are prone
to error.
She noted that a new test for tear film osmolarity (Tear Lab) may provide a more objective approach. It is
designed to detect the aqueous defect or evaporation from the ocular surface. The test can be performed by a
technician and requires less than 50nl of a tear sample for a valid measurement
Research has established a link between tear instability and hyperosmolarity. The test provides physicians with
the ability to quantify and grade the severity of dry eye and base their treatment accordingly.
“Osmolarity testing can detect at-risk patients among the refractive surgery population. Early detection can
enable pre-op and post-op management of dry eye. Tear osmolarity can also
be used to monitor patients’ response to treatment,” Prof Cochener said.
However, she added that even though the Tear Lab test is an interesting tool, it is more dedicated to university
and clinical research trials [at the time of this presentation] because of the cost of the tips.
Another instrument which shows potential in the assessment of tear osmolarity is The Optical Quality Analysis
System (OQAS, Visiometrics). The device uses a double-pass technique to measure scattering of the point
spread function, which in turn can serve as a surrogate for tear film osmolarity in eyes where the cornea is clear.
Another new instrument is the LipiView® interferometer (TearScience). It operates on the principle of broadspectrum white light interferometry, and quantifies the lipid content of the tear film in terms of interferometric
colour units (ICU). It is designed to work in conjunction with the new LipiFlow® technology designed to restore
normal function to the meibomian gland in eyes where it is impaired.
The LipiFlow® device is designed to remove obstructions in the meibomian gland through the application of heat
and gentle pulsatile pressure, and thereby increase the lipid content of the tear film, she explained.
Prof Cochener presented results of a prospective randomised trial she and her associates conducted involving 30
dry eye patients. It showed that those receiving a single 12-minute treatment with the LipiFlow device had
better response to treatment in terms of tear film quality and dry eye symptoms at one month than patients who
underwent daily treatment with an eye-lid warming eye patch, the Meibopatch. By three months there was no
significant difference between the groups.
Beatrice Cochener: [email protected]