Corneal transplantation has been practiced for more than 100 years to
restore vision to individuals all over the world. However, such transplantation
is dependent on the continued availability of donor corneas.
Globally, there is a significant mismatch between the number of
individuals with corneal blindness and the number of available donor corneas.
Corneal blindness ranks as the fourth leading cause of blindness globally,
following cataract, glaucoma and macular degeneration, according to the World
Health Organization. In order to solve this problem of supply and demand, we
have to consider new avenues, entailing a paradigm shift from tissue-dependent
to tissue-independent corneal transplantation.
Such a paradigm shift will require a greater dependency on artificial
corneas. This poses the challenge of solving problems associated with
biointegration of artificial corneas and their secondary effects, including
glaucoma, corneal melt, infectious keratitis, retroprosthetic membranes and
endophthalmitis. Solving these issues requires an amalgamation of basic
biomaterial research and clinical evaluations. The doors to tissue-independent
corneal transplantation will be fully open only once these issues are solved or
In the arena of artificial corneas, various devices have been developed,
and the current models include the Boston K-Pro and the AlphaCor artificial
cornea (Addition Technology). The Boston K-Pro has shown significant clinical
acceptance among corneal surgeons worldwide.
In this column, Drs. Vargas and Shiuey describe their initial results
with the new KeraKlear (KeraMed) artificial cornea, which is the first foldable
artificial cornea. The KeraKlear is not approved by the U.S. Food and Drug
Administration. Close clinical monitoring of the KeraKlear over an extended
period of time is mandatory to evaluate the overall safety and efficacy of this
Thomas John, MD
OSN Surgical Maneuvers Editor
The KeraKlear from KeraMed is a new type of foldable artificial cornea
that is designed for synthetic anterior lamellar keratoplasty through small
incisions. The KeraKlear is able to restore vision by replacing the anterior
portion of the cornea, in which the majority of the focusing of light rays
occurs. This device is implanted into a femtosecond laser-created lamellar
corneal pocket with an 8-mm diameter after the removal of the central anterior
cornea. Posterior cornea with the patients endothelium is retained, and
it is thought to avoid a number of common complications of other artificial
corneas, including endophthalmitis and retroprosthetic membranes. The KeraKlear
is made of a proprietary biocompatible material that is sufficiently flexible
(Figure 1) to be implanted through a 3-mm incision using forceps. The optic
diameter is 4 mm, which provides a large enough optical zone to afford a full
visual field and a good view of the fundus.
|Figure 1. Foldable artificial
Images: John T, Vargas JM, Shiuey Y
Dr. Shiuey, the inventor of KeraKlear, recognized the need for an
artificial cornea that would be simple to use in the absence of donor tissue.
This artificial cornea merges the principles of small-incision cataract surgery
and femtosecond laser refractive surgery. The result is an artificial cornea
procedure that can be learned easily and provides rapid recovery for the
Dr. Vargas, of Valencia, Venezuela, has used the KeraKlear in 10
patients with corneal graft rejection, corneal scars and keratoconus. He and
his patients have been very pleased with the results of the KeraKlear. The
improvement in vision has been immediate, and he also likes that in the event
of a complication, he could still perform penetrating keratoplasty because only
5% of the patients corneal tissue is removed as part of the KeraKlear
A patient with a history of two failed cornea transplants secondary to
endothelial rejection and hand motion vision underwent the KeraKlear procedure.
On day 1 after surgery, his uncorrected vision was 20/100 and he could read
large print (Figure 2). Additionally, on postop day 1, the iris details were
visible through the artificial cornea (Figure 3) and the fundus could be
visualized (Figure 4). At 1 month, uncorrected vision improved to 20/60.
Results have remained stable over 6 months.
Figure 2. Preoperative and postoperative
photographs after KeraKlear procedure.
|Figure 3. On day 1 after KeraKlear procedure, the iris details
are visible. |
|Figure 4. Fundus visualization is possible on day 1 after
A patient had keratoconus, apical scarring and preoperative vision of
20/400. After the KeraKlear procedure, uncorrected vision improved to 20/30 on
postoperative day 1 (Figure 5).
Preoperative and postoperative day 1 appearance of a keratoconus cornea after
Advantages of procedure
A key factor in the success of this procedure has been the use of the
femtosecond laser to create the corneal pocket. When a surgeon manually
dissects a corneal pocket, it is not possible to accurately create a pocket of
consistent depth, which may lead to complications. Moreover, for cases in which
the cornea is thin, such as with keratoconus, the accuracy of the femtosecond
laser is even more critical. Dr. Vargas has used the Ziemer LDV Crystal Line
laser for implantation of the KeraKlear in cases of keratoconus and has found
that using the femtosecond laser makes the procedure fast and predictable.
Traditionally, artificial corneas have been considered the last-line
option because of difficult surgery and the risks of serious complications.
Because the KeraKlear can be implanted with removal of only 5% of corneal
tissue and does not penetrate into the anterior chamber, it may be suitable as
a first-line procedure, especially in many places worldwide where corneal
tissue is difficult to obtain. Additionally, implantation of the KeraKlear does
not appear to affect IOP, and measurement of IOP is possible with a Tono-Pen
(Reichert) applied to the peripheral cornea. The Table shows a list of
potential advantages of the KeraKlear compared with traditional PK.
As is the case with other artificial corneas, the KeraKlear requires
daily use of antibiotic drops such as moxifloxacin 0.5% and vancomycin 14 mg/mL
twice daily for the prevention of infection. Other commercially available
antibiotics may also be used. However, daily steroids for the prevention of
rejection are not necessary as is usually the case with PK. The lack of chronic
steroid use helps to avoid the complications of glaucoma and cataract
formation. A bandage contact lens such as the Kontur Precision Sphere is also
suggested to help protect the interface between the KeraKlear and the recipient
The KeraKlear has received European CE mark approval but is not cleared
for use in the United States.
- Colby KA, Koo EB. Expanding indications for the Boston
keratoprosthesis [published online ahead of print May 2, 2011]. Curr Opin
Ophthalmol. doi: 10.1097/ICU.0b013e3283477d0d.
- Gomaa A, Comyn O, Liu C. Keratoprostheses in clinical practice
a review. Clin Experiment Ophthalmol. 2010;38(2):211-224.
- Hartmann L, Watanabe K, Zheng LL, et al. Toward the development of
an artificial cornea: Improved stability of interpenetrating polymer networks
[published online ahead of print April 18, 2011]. J Biomed Mater Res B
Appl Biomater. doi:10.1002/jbm.b.31806.
- Pineda R II, Shiuey Y. The KeraKlear artificial cornea: A novel
keratoprosthesis. Tech Ophthalmology. 2009;7(3):101-104.
- Thomas John, MD, is a clinical associate professor at Loyola
University at Chicago and is in private practice in Oak Brook, Tinley Park and
Oak Lawn, Ill. He can be reached at 708-429-2223; fax: 708-429-2226; email:
- Yichieh Shiuey, MD, can be reached at 408-752-0850; email:
- Jose M. Vargas, MD, can be reached at 58-241-8246064; email:
- Disclosures: Dr. John has no financial interest in any aspect of
this article. Dr. Shiuey is the inventor of the KeraKlear and has a financial
interest in this device. Dr. Vargas is a paid consultant for KeraMed.