The technique for implanting AlphaCor was originally recommended to be completed by a Gunderson flap in all cases. However,
a review of past procedures revealed no evidence of a beneficial effect, in terms of reducing the risk of stromal melting
around the device. In most cases, it is thought that the additional surgery and trauma to limbus and superficial nerves may
actually be detrimental and that other methods may be more effective in protecting the ocular surface. It may still have a
place in the minority of cases with severely disordered limbal function and ocular surface.
As a consequence of replacing much of the central ocular surface with plastic, there was a subsequent reduction in tear film
quantity and quality. However, methods have been identified which can help optimise the ocular surface, postoperatively. These
include the use of tetracyclines and Omega-3 oils systemically, Restasis (Allergan) and tear supplements topically, and by
measures such as bandage lenses, punctal occlusion or lateral tarsorrhaphy as required. Topical antibiotics and anti-collagenases
are also routinely used postoperatively although opinions differ in terms of the optimal long-term topical antibiotic regimen.
Topical preserved chloramphenicol 1% appears to be the drug of choice, outside of the US, reserving other medications for
specific indications and most feel it beneficial to maintain topical antibiotics and to clean off any biofilm to minimise
the risk of infection.
During recovery it can be difficult to take accurate intraocular pressure (IOP) measurements. The options that are available
for IOP estimation postoperatively include Tonopen (Medtronic) near the limbus, an innovative but unproven through-the-lid
device and digital assessment. Accurate IOP readings cannot be taken through the device optic, but disc view, field tests
can be performed after stage II of the procedure.
Outcomes and complications
Current outcome data are available for the 322 AlphaCor devices implanted before the end of February 2006, with a mean follow-up
in situ of 15.5 months. Data are reported voluntarily by user surgeons into an anonymous database, for review by users and the device's
Scientific Advisory Board. Overall, all types of complication showed significantly falling rates, felt to be attributable
to improved patient selection, surgery and management with experience.
In particular, the risk of the 'classic' feared complications of keratoprosthesis surgery was found to be low, with rhegmatogenous
retinal detachment and endophthalmitis resulting in loss of an eye, each affecting just 0.6% cases. The probability of successful
retention in situ to one year was over 80% with most unsuccessful cases being restored to their pre-AlphaCor condition with a PK.
Just two device powers are available currently, one for aphakes and one for all other patients, so some refractive correction
is to be expected in the majority of cases. Experience with refraction and lens fitting in these patients may be accounting
for the trend to improving acuity outcomes, with the trend away from Gunderson flaps accounting for greater ease in lens fit.
A combination of a flexible soft lens in low minus power, piggy-backed with a small diameter rigid gas permeable (RGP) lens,
ensuring good fit and movement of both (Figure 4), was recommended by Michael Taravella, MD, during a course on AlphaCor management
during the 2006 meeting of the American Society of Cataract and Refractive Surgeons in San Francisco. Restasis may also assist
with lens tolerance.
Figure 4: Patient fitted with piggy-back contact lenses. (Image provided by M Taravella)
As always there is a steep learning curve when dealing with new technologies but it is clear that outcomes with AlphaCor are
continuing to improve, both in terms of reduced complications and improved visual acuities. For perhaps the first time there
is a viable alternative for those patients considered a high risk for PK.
Celia Hicks, FRCOphth is Director, Biomaterials & Polymer Research at Lions Eye Institute and Centre for Ophthalmology and Visual Sciences, University
of Western Australia, Australia. She may be contacted by E-mail: email@example.com
, Tel: +61 893 810 877.
She is the Medical Director of CooperVision Surgical and has a financial relationship with the company through departmental