AlphaCor TM : 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

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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

Case #

1 2 3 4 5

Gender

F F M M F

Age

32 49 33 53 39

Surgery Date

2/2005 5/2005 10/2006 12/2006 12/2006

# Graft Failures Pre Op

2 5 3 2 4

Ocular History

Aphakia Nystagmus PPV/Lensectomy RD Retinopathy of Prematurity Trabeculectomy Multiple glaucoma surgeries Keratitis (possibly herpetic) PC IOL Sclerocornea Baerveldt Tube Globe Rupture Repair Iris Implant PC IOL Trabeculectomy Vitrectomy Aniridia Aphakia Glaucoma RD ECCE IOL Glaucoma Nystagmus Peters’ Anomaly

Pre Op VA

HM 6in HM1ft LP 20/400 LP

BCVA Post Op

HM 1ft HM4ft CF10" 20/300 HM3ft

Complications in Postoperative Course

Elevated IOP RD RPM Band Keratopathy Calcium Deposits Elevated IOP Microcystic Edema Elevated IOP Elevated IOP Epithelial Defect Hyphema s/p Tube SPK RPM 6 M 73 12/2006 2 Aniridia (traumatic) Globe rupture repair IOL Explantation Phaco IOL PPV 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