KERATOPROSTHESIS

SIVA TEJA CHALLAKERATOPROSTHESIS

DEFINTIONKeratoprosthesis is a surgical procedure where a severely damaged or diseased cornea is replaced with an artificial cornea to restore useful vision or to make the eye comfortable in painful keratopathy

HISTORY1789-Pellier de quengsyglass lens in silver ring for leukomatous cornea

1853-Nussbaumcollar-stud glass device consisting of two plates sandwiching the cornea and connected by an optical cylinder, 2 with trials in rabbit eyes.

1859-Heusserrst to implant a keratoprosthesis in a human eye;this was retained for 3 months.

Other attempts made in Later half of 19th century (Von Hippel 1877, Dimmer 1889, Baker1889, van Millingen 1895, Salzer 1895) but almost all the implants failed and were extruded.

The interest in keratoprostheses declined following the development of successful penetrating keratoplasty (PKP) in the rst decade of the 20th century

the realization that transplanting a human cornea would not be successful in all cases of corneal blindness

During the Second World War, the incidental discovery of corneal tissue tolerance to plexi-glass fragments from aeroplane canopies suggested a new direction for future research

The commonly used ones areBOSTON KPRO(TYPE 1 AND 2)The Boston Type I Kpro is the most widely used device.The Boston Type II Kpro may be indicated in patients with severe ocular surface disease, poor ability to maintain a moist ocular surface, and forniceal foreshortening with inability to wear a contact lens

ALPHA-COR KPROAlphaCor Kpro is indicated in patients with failed grafts due to corneal allograft rejection

OSTEO-ODONTO KPRO(OOKP)OOKP like theBoston Type II Kpro, is reserved for end-stage ocular surfacedisease as a last resort

INDICATIONS1.AUTOIMMUNE DISORDERSSteven johnsons syndromeDry eye and uveitis2.ANIRIDIA3.CHEMICAL OR THERMAL INJURY4.BULLOUS KERATOPATHY advanced cases with stromal scarring, lamellar or full-thickness procedures may be required, while Kpros may be considered after serial graft failures.5.HERPETIC DISEASE Kpro after graft failure from herpeticdisease has been shown to be successful in achieving better visual outcomes6.GRAFT FAILURE7.PAEDIATRIC CORNEAL OPACITIES PK is primary procedure

BOSTON KERATOPROSTHESISBoston Keratoprosthesis is the innovation and design of Professor Claes H. DohlmanFDA approval 1992types 1 and 2made from poly methyl methacrylate (PMMA).Most commonly used type 1

IndicationTwo failed grafts, with poor prognosis for further graftingVision less than 20/400 in the affected eyeMinimum vision of Light PerceptionLower than optimal vision in the opposite eye

AdvantagesLong-term (many years) stability and safety.It is also known for having excellent optics.Its optical system can provide excellent vision if the rest of the eye is undamaged

ContraindicationsUnilateral vision lossEnd-stage glaucoma or uncontrolled glaucomaPosterior segment pathologyPresence of a functioning KPro in the fellow eye

Parts

collar button design

There is a front plate and back plate sandwiching a fresh donor corneal graft

Titanium locking ring is used to secure the front And back plates and corneal complex to prevent Any Inadvertent Unscrewing of the complex.

Type 1

The typical anterior surface power of this device is 4344 dioptres.

Aphakic eyes require a variety of powers depending on the axial length

Type 2The type 2 device is of a similar design, with an added anterior cylinder that protrudes through a permanently closed upper eyelid, and is used in end-stage dry eye

Back plates holes are important to allow the nutrients to reach the graft keratocytes from the aqueous

surgerySuperficial keratectomy of 8.5 mm of donor cornea then a 3mm central punch doneThe donor button is then placed over the stem of the front plate and the back plate is slid into place on top of this without screwing or turning. A titanium locking ring is then pushed onto the remaining exposed stem until an audible snap is heard

The recipient cornea is then trephined as for conventional PKP (trephine diameter 0.5 mm less than donor trephine size). The donor graft with the KPro is then sutured in place with interrupted 100 nylon, using the same technique as a standard PKP.Surgery usually concludes with the intracameral injection of 0.4 mg dexamethasoneConclusion with the application of a soft contact lensPost op steroid E/D ,antibiotic E/D usedPost op F/U at 1,2.4 wks,then monthlyEach visit IOP and VA noted and soft contact lens changed

MODIFIED OSTEO ODONTO KPRO(MOOKP)The OOKP was rst described by Strampelli in 1963Later modified (MOOKP) by falcinelli and collIt uses the patients own tooth root and surrounding alveolar bone to support a centrally cemented optical cylinder.Multi staged procedure, sx in mouth and eye

PRINCIPLEuse of a wide single rooted tooth with surrounding alveolar bone acts as carrier for a PMMA optical cylinder, which is covered by buccal mucous membrane,

INDICATIONS

CONTRAINDICATIONSAbsent light perceptionEdentulous pt.Age