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November 2002
IN THIS ISSUE

Wavefront seeks a higher order of vision correction
New laser system for intraoperative measurement of LASIK flap thickness
Visual prostheses use neurotransmitter retinal chips to stimulate retinal function
Wavefront emerges as powerful tool for night vision
Allegretto promising for hyperopia and hyperopic astigmatism
Topography's role in wavefront systems
IOP measurement after LASIK may be unreliable
LASEK may only play support on refractive stage
Solid-state laser PRK yields favourable results for myopia
GTS-assisted DLK useful alternative to PK for keratoconus
Glaucoma common after PK bodes poorly for visual outcome
Classic drawbacks of PRK succumb to new strategies
New insight into LASIK dry eye pathogenesis
Use of anti-inflammatories after capsulotomy questioned
Good quality training leads to good quality cataract surgery
One line of regained visual acuity is a snip at just €120
Mitomycin-C provides effective haze prophylaxis
Long-term concerns linger on safety of Mitomycin-C
German politicos promise health reforms
Honey forms biblical basis for corneal oedema
Routine two-step LASIK after PK unnecessary
Plasma knife provides clean and accurate cut for capsulorhexis
Glaucoma therapy targets apoptosis and trabecular meshwork
Viscocanalostomy viable choice for cataract-glaucoma
Device allows needle-free injections into smallest vessels
New river blindness therapy may provide panacea for 18m people
Daytime running lights may soon be compulsory in all EU states
Intracorneal lamellar implants still a questionable option
Aqualase system viable for small incision cataract removal
Unilateral von-Hippel disease with optic nerve head
FEATURES
From The Editor
Reflections on Refractive Surgery
In Your Good Books
An Eye On Travel
Bio-ophthalmology
Outlook on Industry
Regulatory Matters



New insight into LASIK dry eye pathogenesis

By Stefanie Petrou-Binder MD

NICE - Altered tear composition plays a decisive role in the pathogenesis of post-LASIK dry-eye, according to researchers at the Mainz University Eye Clinic, Germany.
Franz Grus MD reported at this year's annual Congress of the ESCRS that following LASIK, patients have lower levels of some main tear proteins including albumin, while a number of other protein tear levels peak.

He presented the results of his electrophoretic analysis of tear protein patterns from a study that analysed and compared the electrophoretic patterns of tears in LASIK patients, both before the procedure and during the follow-up period. He also contrasted these values with changes in non-LASIK dry eyes.

Dr Grus's study comprised 80 patients. He divided them into a before-LASIK group (control); three post-LASIK groups at four days (group B), two weeks (group C), and four weeks (group D) after LASIK; and a non-LASIK dry-eye group.
Patients were asked to report their subjective symptoms, like burning, itching and foreign-body sensation.

Dr Grus separated the tear proteins by implementing SDS-PAGE (sodium-dodeyl-sulfate poly-acrylamide gel electrophoresis). He performed digital image analysis with BioDocAnalyze® (Biometra, Germany).

That technique creates densitometric data files for each electrophoretic lane. He used multivariate statistical techniques to analyse the data.
The basal secretory test revealed decreased values four days following LASIK, but these recovered within the next week back to normal values. All of the main protein peaks were significantly decreased four days after LASIK (P<0.01).

Excepting albumin which remained at a lowered level, the main protein peaks returned to their normal values within the ensuing four weeks.
The number of additional protein peaks increased significantly (P<0.01) within two weeks following LASIK surgery. Furthermore, there was an additional increase in these values within the four-week period.

Dr Grus noted that the changes he observed in the tears of the LASIK groups contrasted significantly with the tear protein values assessed in the non-LASIK dry eye study group.

<Dry eye disease is not an uncommon complication in patients who have undergone LASIK>. Although researchers have not yet been able to firmly establish the pathogenesis of dry eye following LASIK, they have proposed a number of theories.
One theory proposes that dry eye may result from the transection of corneal nerves, which induces a neurotrophic cornea. This disjunction engenders the loss of an important feedback mechanism for the stabilisation of the ocular surface.

A past study performed by Dr Grus introduced high-performance liquid chromatography (HPLC) analysis of tear proteins as a reliable diagnostic tool to differentiate healthy eyes from those with Sicca-Syndrome.

He found reproducible evidence that certain tear protein patterns consistently corresponded to the disease, while other patterns indicated healthy eyes.
His investigations of protein level changes in Sicca-Syndrome do not correlate with the changes observed in the post-LASIK patient groups. No significant change in the main tear proteins could be found in patients with Sicca-Syndrome.

Although several factors are likely to influence hydration of the cornea, the current study verifies the existence of biochemical changes in the composition of tears due to LASIK. It underscores the relevance of tear film quality for the maintenance of the ocular surface.

Dr Grus notes the current investigation gives more insight into the pathogenesis of dry eye following LASIK and offers a new perspective on the development of novel therapeutic approaches.
 

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