AlphaCorTM: A Novel Approach to Minimize Late Post-operative Complications

V. Ngakeng MD, M. Price PhD. MBA, F. Price MD.

The AlphaCor artificial cornea (Addition Technology, Des Plaines, IL)

• The Chirila Kpro• Used for high risk grafts • Hydrophilic polymer, poly (2-hydroxyethyl methacrylate)

(PHEMA)

AlphaCor Implantation

• First implanted in a patient in October 1998 in Australia

• Surgical technique is a two-stage procedure– Stage 1

• corneal lamellar dissection• 3 to 3.5 mm central disc of corneal tissue is removed from the posterior

stromal bed• device is implanted into the lamellar pocket.

– Stage 2 • removal of a central 3 mm diameter disc of corneal tissue from the anterior flap

• The best possible visual acuity is usually only achieved after completion of stage 2

AlphaCor Implantation

Stage 1

AlphaCor Stage 2

After Stage 2:

• Complications– Deposits and

spoliation– stromal melting– Poor biointegration– Device extrusion

• Hicks et al: – melts occurred in 26% – resulted in device

explantation in 65%

• Restrictions– Avoid smoking – Topical medications

restrictions

•Optic deposition

Betagan - dark brown

Tobacco smoke – hazy brown

• Purpose

– To describe clinical outcomes of patients who underwent implantation of the AlphaCor keratoprosthesis without the second stage of the procedure

• Methods– 6 consecutive AlphaCor implantations

without second stage performed at a single tertiary referral center between February 2005 and December 2006

Table 1: Patient Demographics and Treated Eye Characteristics

Case #

Gender Age Surgery Date

# Graft Failures Pre Op

Ocular History Pre Op VA

BCVA Post Op

Complications in Postoperative Course

1 F 32 2/2005 2 AphakiaNystagmus PPV/Lensectomy RDRetinopathy of PrematurityTrabeculectomy

HM 6in HM 1ft Elevated IOPRDRPM

2 F 49 5/2005 5 Multiple glaucoma surgeriesKeratitis (possibly herpetic)PC IOLSclerocornea

HM1ft HM4ft Band Keratopathy Calcium DepositsElevated IOP Microcystic Edema

3 M 33 10/2006 3 Baerveldt Tube Globe Rupture RepairIris ImplantPC IOL Trabeculectomy Vitrectomy

LP CF10" Elevated IOP

4 M 53 12/2006 2 AniridiaAphakia GlaucomaRD

20/400 20/300 Elevated IOPEpithelial DefectHyphema s/p Tube SPK

5 F 39 12/2006 4 ECCE IOL Glaucoma NystagmusPeters’ Anomaly

LP HM3ft RPM

6 M 73 12/2006 2 Aniridia (traumatic)Globe rupture repair IOL Explantation Phaco IOLPPV

CF at 1 feet

CF at 4 feet

Elevated IOP

CF, Counting Fingers; HM, Hand Movements; LP, Light Perception; IOP, Intraocular Pressure; IOL, Intraocular Lens; SPK, Superficial Punctate Keratopathy; RPM, Retroprosthetic Membrane; ECCE IOL, extracapsular cataract extraction with introcular lens; BCVA, Best Corrected Visual Acuity; RD, Retinal Detachment

Complications

• No intra-operative complications• 5 patients developed elevated IOP• 2 developed retroprosthetic membranes • None developed

– stromal melting– aqueous leakage– Infection– extrusion

• All in situ and stable with follow-up of 9 to 32 months

Conclusions

• By not exposing the keratoprosthesis to the outside of the eye, it may be possible to minimize, and potentially nearly eliminate, the most significant risks of keratoprosthesis surgery, which are melting of the tissue surrounding the implant, with secondary extrusion of the implant or endophthalmitis

• In our small series without the second stage of the procedure, no stromal melts have occurred, and all devices remain in situ with a mean follow up of 17 months

• By maintaining the same corneal surface, degree of visual recovery is limited, so this is not advisable for patients that need or desire to regain better visual recovery than potentially in the range of 20/200