Continued exploration of multiple
corneal and ocular surface surgical approaches bodes well for good
in tissue engineering, synthetic polymers, mechanical and laser
devices, pharmacological agents and diagnostic equipment are bringing
us closer to
breakthroughs in the treatment of corneal and ocular surface disorders.
Presentations at the XX ESCRS Congress demonstrated how these improvements
are facilitating current re-exploration of decades-old techniques,
such as lamellar keratoplasty, amniotic membrane transplantation
and artificial replacements of
Innovations in microkeratome technology in refractive surgery and
small-incision techniques in cataract surgery have influenced anterior
and posterior procedures and provided more options in the treatment
of corneal disease.
Recent technical progress has led to improved optical results and
decreased complications with these procedures. However, although
indications for these procedures are increasing, the procedures
themselves have not improved sufficiently to supersede penetrating
keratoplasty (PK) in many cases.
Deep anterior lamellar keratoplasty (DALK) requires dissection at
the level of Descemet's membrane to obtain optimal optical results.
Multiple studies have documented poorer optical results when DALK
is not performed at this level.
Endothelial damage precludes the use of lasers for DALK at the level
of Descemet's. Cleavage at this level has been facilitated with
different techniques of fluid, air and viscoelastic dissection,
but perforation of Descemet's membrane still occurs even with experienced
This complication can lead to secondary anterior chamber formation
and increased risk of graft failure in the early postoperative period,
as documented in published studies and again at the Nice Congress.
Khandwala and associates reported on Descemet's perforation resulting
in a graft failure rate of 6.25% during the first six months after
DALK with fluid and air dissection in keratoconus patients.
We need to develop safer and more reliable dissection methods before
DALK can be considered the procedure of choice in patients, without
increased risks of wound dehiscence or rejection.
Although the risk of a rejection episode is about 10 times lower
after lamellar keratoplasty than after PK, we must remember that
rejection does occur after lamellar procedures.
It should also be emphasised that most rejection episodes after
both lamellar and penetrating keratoplasties are mild and easily
treated with topical therapy in patients with pathologies such as
Multiple studies have documented five-year full-thickness graft
survival rates of up to 90% to 100% in keratoconus patients.
Posterior lamellar keratoplasty is evolving quickly through the
innovative work of Melles and others. Most recent approaches include
increasing the posterior lamellar disc diameter to maximise the
number of endothelial cells implanted. Techniques that allow insertion
through small limbal incisions created mechanically or with lasers
are being developed. Techniques should minimise endothelial damage
from folding or touch.
Ideal donor and recipient diameter disparities need to be determined
to best balance tight-sealing wounds with minimal inducement of
unwanted sphere or cylinder.
PK is still the primary procedure for treating corneal blindness.
Additions to our diagnostic armamentaria are enabling more complete
assessment of visual function after PK and correlation with surgical
New developments in mechanical and laser trephine designs have been
very limited for many years because of the surge of interest in
refractive surgery. Improvements in trephination systems are needed
to further improve refractive results after corneal transplantation.
Re-exploring laser trephination
Several surgeons noted at the Nice Congress that there has been
more interest in the ophthalmic industry over the past year in re-exploring
After my first use and development of the excimer laser for PK,
only the German groups of Lang, Naumann and Seitz pursued clinical
use for many years. Hopefully, recent advances in both laser and
mechanical device technologies will be applied to
The quest for artificial replacements for human corneas continues.
Despite the availability of more synthetic polymers and chemical
modifications to enhance biocompatibility and biocolonisation, long-term
stability remains problematic.
Although we have not yet achieved much better long-term clinical
results than with some keratoprostheses developed decades ago, experimental
work with newer approaches to support epithelialisation are promising.
Ultimately, it is hoped
tissue-engineered corneal substitutes will provide better results.
Increasing experimental success in culturing and transplanting corneal
cells, as well as in combining polymeric scaffolds with cells derived
from stem cells or from corneal epithelial, stromal and endothelial
cell lines, offer exciting prospects for treatment.