This document provides information about artificial cornea or keratoprosthesis surgery. It discusses the history and indications for the procedure, describes common designs for artificial corneas including biointegrated and non-biointegrated options, and outlines some of the major keratoprosthesis designs including the Boston KPro, AlphaCor KPro, and modified osteo-odonto keratoprosthesis. It also covers the preoperative evaluation, surgical procedure, postoperative management, prognosis, and complications for keratoprosthesis surgery.

1. Artificial cornea
or
Keratoprosthesis
Dr Nikhil R P

2.  Keratoprosthesis is asurgical procedure where a
severely damaged ordiseased cornea is replaced with
an artificial cornea to restore useful vision
 It is usually the last option for the surgeon and the
patient who has visual potential in an eye with
severely compromised cornea

3. History

4.  Bilateral Blindness with Visual acuity of hand movements
or less with normal Bscan
 Severe Debilitating but inactive anterior segment disease
such asSteven Johnson Syndrome, Chemical Burns or
Trachoma
 Multipleprevious failed corneal grafts
 Ocular cicatricial phemphigoid
 Vascularized corneas with complete stem cell loss and
dryness
Indications

5. Designs
• Consists of Optical cylinder and Supporting flange
Non Biointegrated(Optical cylinder materials)
• Polymethyl methacrylate (PMMA) – most commonly used material
• Glass, Ceramic, Quartz , Silicon
Non Biointegrated(Supporting flange)
• Methacrylate
• Teflon
• Dacron mesh
• Polycarbon

6. Biointegrated Supporting Flange (Autologous tissue)
• Tooth and bone (osteo-odonto-keratoprosthesis)
• Cartilage (chondro-keratoprosthesis)
• Nail (onycho-keratoprosthesis)

7. Keratoprosthesis designs have primarily been variations of 3 main
types.
• First Type PMMA stem with skirt embedded within the cornea
• Second Type Transparent membrane with porous edges inserted
• into the cornea
• Third Type PMMA ‘collar button’ with cornea between the plates

8. First type: It is most commonly used. The optical core is stabilized
by a permanently attached supporting plate or skirt implanted in
a pocket created in the collagen lamellae of the corneal stroma.
Consists of
• Central Optical Cylinder
• Supporting Flange
• PMMA stem
• Skirt placed intralamellarly in the stroma(made of
perforated grids of PMMA, nylon, Dacron, proplast/
covered by transplanted autologous tissue/ lid skin

9. Second Type: Consists of transparent plate with a porous periphery,
allowing tissue ingrowth into the pores. Such designs have been
made of polytetraflouroethylene, polyurethane, or modified gels.
By using suitable pore size, these devices have been well colonized
with tissue elements which might help to anchor the device and
prevent future extrusion.

10. Third Type: has a collar button shaped device consisting of two plates
joined by a stem, which constitutes the optical portion. This is inserted
into the patient’s cornea or a donor cornea so that the plates sandwich
the corneal tissue between them. The optical stem is short, allowing a
generous field and wide plates stabilize the stem so that it cannot
easily deviate from the axis to the macula.

11.  BOSTON KPRO(TYPE 1 AND 2) :-
 The Boston Type I Kpro is the most widely used device.
 The Boston Type II Kpro
 AlphaCor Kpro
 Modified OSTEO-ODONTO KPRO(MOOKP)
CommonlyUsedProcedures

12.  In development since1960
 Made of PMMA
 Also called Dohlman-DoaneProcedure
 2Types – Type 1 and Type2
BostonKeratoprosthesis

13.  2Types
 Type 1:-More commonly
used. Used in eyes that have
sufficient wetting function
to maintain the corneal
tissue in which the Kpro is
placed.
 Type 2:-Used in very dryeye
with minimal or no tear
production.
Boston KeratoprosthesisTypes

14. TYPE 1
• Front plate -6-7 mm dia
• Stem- 3.35mm
• Back plate – 7-8.5mm-16 holes
• Locked with titanium plate
• Length – AP -3.7mm – visual
field of 60 deg
TYPE 2
• 2mm long anterior nub off the
front plate
• Front plate -6 mm dia
• Back plate of 8.5mm dia -8 holes
• Length – AP-4.7mm
• 40 deg field of vision

15.  Indication
 Two failed grafts, with poor prognosis for further grafting
 Vision less than 20/400 in the affected eye
 Minimum vision of Light Perception
 Lower than optimal vision in the opposite eye
 Advantages
 Long-term (many years) stability and safety
 Excellent optics
 Canprovide excellent vision if the rest of the eye is undamaged
 Contraindications
 Unilateral visionloss
 End-stage glaucoma or uncontrolledglaucoma
 Posterior segmentpathology
 Presence of afunctioning KPro in the fellow eye

16. Partsof aBostonProsthesis
 Collar Button Design
 Front Plate and Back Plate
Sandwiching a fresh donor
graft
 Titanium locking ring is
used tosecure front and
back plates.
 Back plate holes are
important to improve
corneal nutrition.

17.  Electroretinography (ERG) and Visually Evoked
Response (VER) helpful in predicting the visual
potential.
 Pre operative Ultrasound examination to rule out
presence of Retinal Detachment and other posterior
segment abnormalities.
 IOPshould be maximally controlled before surgery
PreoperativeEvaluation

18. Procedure
 7.5-8.5mm donor corneal buttonis prepared
 3mm dermal punch used to punch central
donor corneal button
• Front plate placed face down on
adhesive to stabilize during
assembly
• Corneal donor button placedover
KPro stem

19. • Back plate carefully pressed into
position with
• Titanium locking ring is
snapped into position
• A snap sound signifies , it is in
proper position
• Graft and Type I BostonKPro
fully assembled

20.  The recipient cornea is then trephined (9mm)
similar to conventional PKP
 Natural lens or pseudophakia( anterior or iris supported
lens) are removed and total iridectomy and anterior
vitrectomy are done to reduce retro prosthetic membranes
andglaucoma.
 The donor graft with the KPro is then sutured in place with
interrupted 10–0nylon, using the same technique asa
standard PKP.
 Intravitreal injection of 0.4 mg dexamethasone.
 Bandage contact lens is applied

21.  Topical Antibiotics daily for3-4 weeks.
 Oral antibiotics for 1 week
 Steroid eye drops – 4-6 weeks and then tapered.
 Sub-Tenons injection of 20-40mg Triamcinalone if
eye shows an inflammatory reaction.
 Initially weekly followup, after 6 months once every 2
months.
PostoperativeManagement

22. Best:
•Multiple Graft failure in a relatively non-inflamed eye
with intact tear and blink mechanisms (following
dystrophies, infections, etc)
• Aniridia and other limbal stem cell failure cases
Intermediate:
•Chemical burns, HSV
Worst:
•Autoimmune diseases
•Mucous membrane pemphigoid
•Stevens-Johnson syndrome
• Chronic uveitis
Prognosis

23.  This design has a 2mm long anterior nub off the front
plate which requires apermanent tarsorrhaphy to be
performed through which a small anterior nub of the
type II modelprotrudes.
Type2

24.  Developed by Traian Chirila research group from Australia.
 Biocompatible, flexible, one-piece 7mm artificial cornea
designed to replace a scarred or diseased native cornea.
 Refractive Power close to that of human cornea .
AlphaCor

25.  Consists of
 the outer opaque porous skirt made from high water content
poly 2-hydroxyethyl methacrylatePHEMA.
 Atransparent central optic made from low-water content
PHEMA.
 Interpenetrating polymer network (IPN) – junction between
the skirt and central optic and is apermanentbond
 Principle :- The ability of the outer skirt to be colonized by
invading keratocytes resulting in integration of the device
with surroundingtissues

26.  VAfrom <6/60 to light perception
 Previous failed grafts with a poor chance with further PKP
 Functioning retina
 Absence of evidence of advanced glaucomatous optic
neuropathy or well-controlled glaucoma on medication
INDICATIONS

27.  Stage 1:-
 360 deg conjunctival peritomy is done
 Superficial keratectmoy
 Acorneal limbal incision is made for 5 clock hours and a
corneal stromal dissection throughout the areaan intra
lamellarpocket.
 AnAlphaCor is inserted into the interlamellar pocket followed
by removal of the posterior disc using an intra stromal
trephine.
 The surfacce is then covered with an conjunctival flap.
 Stage 2:-
 2months after Stage 1,tissues superficial tothe AlphaCor
optic are removed (trephination of central 4mm)
Procedure

28.  Trephination of Cornea
 AlphaCor KPro after stage 1
 Insertion ofAlphaCor
 AlphaCor KPro after stage
2

29.  The OOKPwas first described by Strampelli in 1963.
 Later modifiedby Falcinelli and Coll.
 It uses the patient’s own tooth root and surrounding
alveolar bone to support acentrally cemented optical
cylinder.
 Multi staged procedure, surgery in mouth and eye.
 Use of a wide single rooted tooth with surrounding alveolar
bone acts ascarrier for aPMMA optical cylinder, which is
covered by buccal mucousmembrane,
Modified Osteo-Odento
Keratoprosthesis

31. Indications

32.  Full thickness Mucous MembraneGraft
harvested from thebuccal mucosa.
 Graft is sutured over damaged cornea at
insertion of 4 recti muscles and sclera In
four quadrnts with 6-0 vicryl. The extent of
Graft should be extend from upper to
lower fornix and measures around 3-4 cm
in diameter.
 Ithas stem cells,high proliferating Capacity
and adapted tohigh Bacterial load
Stage1

33. to promote the growth
 Followed by Preparation of the Osteodentalacrylic Lamina
(ODAL)
 Asingle rooted tooth, preferably the upper canine is chosen
for preparation of the lamina.
 The tooth with the surrounding alveolar bone is extracted.
 Then sliced sagitally and Central hole is drilled
 customized PMMA optical cylinderis cemented
 ODALis then placed deep to orbicularis oculi of lower lid
in the fellow eye for next 3months to develop
vascularization and of connective
tissue.

34.  This is performed 3months after stage 1
 The Graft is dissected off from the
muscle area and examined for its
integrity.
 The central cornea is trephinedaccording
to the posterior diameter of the cylinder.
 The Graft is placed with the cylinder
centered over the corneal trephination and
sutured.
 Iris is removed with forceps and lens
extraction by ICCE or ECCE. Anterior
vitrectomy is then done
 The Mucous Membrane Graft is finally
reflected back on the lamina with acentral
trephination through which the anterior
cylinder protrudes out.
STAGE 2

35. Corneal Diseases
causing
Blindness
Low Risk for
Penetrating
Keratoplasty
One or more
Multiple Failures
Type 1Boston
Keratoprosthesis
HighPenetrating
Keratoplasty
Dry Surface
GoodLid
MOOKPor Type
2Boston
Keratoprosthesis
Insufficient lid
for ccomplete
tarsorrhapy
Type 2Boston
Keratoprosthesis
WetSurface
Type 1Boston
Keratoprosthesis

36.  MELTSAND EXTRUSION
 INFECTIOUSENDOPHTHALMITIS
 GLAUCOMA
 RETROPROSTHETIC MEMBRANES
 RETINALDETACHMENT
 OTHERS
Complications

37.  Most commonlyreported
 Occurs in 25-64%of pts in 1yr follow up
 These fibrous membranes originate from activated host stromal
cornea cells that migrate through gaps in the posterior graft–host
junction
 More prevalent in individual with chronic inflammation such as
autoimmune diseases anduveitis
 Treatment:-
 Majority may notrequire treatment
 Nd yag capsultomy following by steroids in 90%cases
 Ifmembrane thick, leathery and vascularised -Sxmanagement
 For Boston kpro membranectomy can be performed
 Removal of prosthesis and replacement with new one is preferred
RETRO PROSTHETIC MEMBRANES

38.  Occur at the base of Boston Kpro
 Slit lamp examination and anterior segment OCTare
helpful in detection of corneal thinning aroundKPro
 If melts are seen then replace the whole thing with fresh
graft and put new KPro
 In MOOKP,resorption of buccal mucosa can occur,new
graft can beplaced
 Resoprtion of osteo odonto lamina can occur
 If resorption of dentine has occurred it should be replaced
MELTSANDEXTRUSION

39.  Dreadful complication following kpro surgery
 Treatment:- includes leak repair,injectionof
antibiotics and topicalantibiotics
 Fungal infection suspected -change contactlens and
give topical amphotericin and systemic anti fungals
required
INFECTIOUS ENDOPHTHALMITIS

40.  Single most serious complication following surgery leading
to irreversible loss of vision due to chronic low grade
inflammation, progressive angle closure, anterior
displacement ofiris have been implicated.
 Topical Treatment is effective in Boston type 1Kpro.
 Systemic Treatments can be used with Boston type 2and
MOOKP.
 Tube shunts and endoscopic cyclophotocoagulation have
been successfully used.
GLAUCOMA

41.  Most common posterior segment complication, an
incidence of 16.9%
 Surgical Rx with buckle orvitrectomy
 Choroidal detachments can also develop in eyes with
KPro, in asmany as17%ofpatients
RETINALDETACHMENT

42.  Stanford Keratoprosthesis :-
 Kpro is based onamechanically enhanced Hydrogel
called Duoptix
 It supports the growth of epithelial cells.
 Surrounding the optic is a microperforated rim designed
to promote peripheral tissue integration
 Collagen BasedKeratoprosthesis
 Designed to mimic the extra cellular Matrix of corneal
stroma
RecentAdvances

43. ThankYou