Keratoprosthesis is a surgical procedure where a severely damaged or diseased cornea is replaced with an artificial cornea to restore vision. The most commonly used procedure is the Boston Keratoprosthesis, which uses a donor corneal graft sandwiched between a front and back plate. Complications include melts and extrusion of the graft, infectious endophthalmitis, glaucoma, and retroprosthetic membranes. Close follow up is required after surgery to monitor for and manage any complications.

1. Keratoprosthesis
Presented by Peter C Roy
HS Ophthal
2009 Batch

2.  Keratoprosthesis 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
Definition

3.  1789- first ocular prosthesis Guillaume Pellier de
Quengsy
 1853- quartz crystal implant by Nussbaum
 Real progress in past 40 years- KPro design, material,
prevention and management of complications
 Widespread use limited by early and late
complications
 The Dohlman or Boston Keratoprosthesis is the most
popular now
History

4.  Bilateral Blindness with Visual acuity of hand movements
or less with normal optic nerve and retinal function
 Severe Debilitating but inactive anterior segment disease
such as Steven Johnson Syndrome, Chemical Burns or
Trachoma
 Multiple previous failed corneal grafts
 Normal intraocular pressure with or without medication
 Good Patient motivation
 Absence of active occular surface inflammation
Indications

5.  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(OOKP)
Commonly Used Procedures

6.  In development since 1960
 Made of PMMA
 Also called Dohlman-Doane Procedure
 2 Types – Type 1 and Type 2
Boston Keratoprosthesis

7.  2 Types
 Type 1:- More commonly
used. Used in eyes that have
sufficientwetting function to
maintain the corneal tissue in
which the Kpro is placed.
 Type 2:- Used in very dry eye
with minimal or no tear
production.
Boston Keratoprosthesis Types

8.  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
 Can provide excellent vision if the rest of the eye is undamaged
 Contraindications
 Unilateral vision loss
 End-stage glaucoma or uncontrolled glaucoma
 Posterior segment pathology
 Presence of a functioning KPro in the fellow eye

9. Parts of a Boston Prosthesis
 Collar Button Design
 Front Plate and Back Plate
Sandwiching a fresh donor
graft
 Titanium locking ring is
used to secure front and
back plates.
 Back plate holes are
important to improve
corneal nutrition.

10.  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.
 IOP should be maximally controlled before surgery
Pre operative Evaluation

11. Procedure
 7.5-8.5mm donor corneal button is 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 placed over
KPro stem

12. • Back plate carefully pressed into
position with Spanner wrench or
Wekcels
• Titanium locking ring is snapped
into position with Spanner
wrench
• Graft and Type I Boston KPro
fully assembled

13.  The recipient cornea is then trephined Similar to
conventional PKP
 Natural lens or pseudophakia are removed and total
iridectomy and anterior vitrectomy are done to reduce retro
prosthetic membranes and glaucoma.
 The donor graft with the KPro is then sutured in place with
interrupted 10–0 nylon, using the same technique as a
standard PKP.
 Surgery usually concludes with the intracameral injection of
0.4 mg dexamethasone.
 Conclusion with the application of a soft contact lens

14.  Topical Antibiotics daily for 3-4 weeks.
 Medroxy Progesterone (1%) 4 times a day in 1st month
then 2 times a day to reduce tissue necrosis.
 Sub-Tenons injection of 20-40mg Triamcinalon if eye
shows an inflammatory reaction.
 Initially weekly followup, after 6 months once every 2
months.
Post operative Management

15. 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

16.  This design has a 2 mm long anterior nub off the front
plate which requires a permanent tarsorrhaphy to be
performed through which a small anterior nub of the
type II model protrudes.
Type 2

17.  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 .
Alpha Cor

18.  Consists of
 the outer opaque porous skirt made from high water content
poly 2-hydroxyethyl methacrylate PHEMA.
 A transparent central optic made from low-water content
PHEMA.
 Interpenetrating polymer network (IPN) – junction between
the skirt and central optic and is a permanent bond
 Principle :- The ability of the outer skirt to be colonized by
invading keratocytes resulting in integration of the device
with surrounding tissues

19.  Patients should have adequate tear production
 VA from <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

20.  Stage 1 :-
 A Corneal incision is made and a corneal dissection
throughout the circumference of the corneal graft creating an
intra lamellar pocket.
 An AlphaCor 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 :-
 2 months after Stage 1, tissues superficial to the AlphaCor
optic are removed (trephination of central 4mm)
Procedure

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

22.  The OOKP was first described by Strampelli in 1963.
 Later modified by Falcinelli and Coll.
 It uses the patient’s own tooth root and surrounding
alveolar bone to support a centrally cemented optical
cylinder.
 Multi staged procedure, surgery in mouth and eye.
 Use 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,
Modified Osteo-Odento
Keratoprosthesis

23. Indications

24.  Full thickness Mucous Membrane Graft
harvested from the buccal 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.
 It has stem cells,high proliferating Capacity
and adapted to high Bacterial load
Stage 1

25.  Followed by Preparation of the Osteodentalacrylic Lamina
(ODAL)
 A single 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 cylinder is cemented
 ODAL is then placed in the subcutaneous pouch in the
orbitozygomatic area for next 3 months to develop
vascularization and to promote the growth of connective
tissue.

26.  This is performed 3 months after stage 1
 The Graft is dissected off from the
subcutaneous pouch and examined for its
integrity.
 The central cornea is trephined according
to the posterior diameter of the cylinder.
 The Graft is placed with the cylinder
centered over the corneal trephination and
sutured.
 The Mucous Membrane Graft is finally
reflected back on the lamina with a central
trephination through which the anterior
cylinder protrudes out.
STAGE 2

27. Corneal Diseases
causing
Blindness
Low Risk for
Penetrating
Keratoplasty
One or more
Multiple Failures
Type 1 Boston
Keratoprosthesis
High Penetrating
Keratoplasty
Dry Surface
Good Lid
MOOKP or Type
2 Boston
Keratoprosthesis
Insufficient lid
for ccomplete
tarsorrhapy
Type 2 Boston
Keratoprosthesis
Wet Surface
Type 1 Boston
Keratoprosthesis

28.  MELTS AND EXTRUSION
 INFECTIOUS ENDOPHTHALMITIS
 GLAUCOMA
 RETRO PROSTHETIC MEMBRANES
 RETINAL DETACHMENT
 OTHERS
Complications

29.  Occur at the base of Boston Kpro
 SLE and anterior segment OCT are helpful in detection of
corneal thinning around KPro
 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 be placed
 Resoprtion of osteo odonto lamina can occur,serial CT scan
yearly
 If resorption of dentine has occurred it should be replaced
MELTS AND EXTRUSION

30.  Dreadful complication following kpro surgery
 Treatment:- includes leak repair,injection of
antibiotics and topical antibiotics
 Fungal infection suspected change contact lens and
give topical amphotericin and systemic anti fungals
required
INFECTIOUS ENDOPHTHALMITIS

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

32.  Most commonly reported
 Occurs in 25-64% of pts in 1 yr 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 and uveitis
 Treatment:-
 Majority may not require treatment
 Nd yag capsultomy following by steroids in 90% cases
 If membrane thick, leathery and vascularised - Sx management
 For Boston kpro membranectomy can be performed
 Removal of prosthesis and replacement with new one is preferred
RETRO PROSTHETIC MEMBRANES

33.  Most common posterior segment complication, an
incidence of 16.9 %
 Surgical Rx with buckle or vitrectomy
 Choroidal detachments can also develop in eyes with
KPro, in as many as 17 % of patients
RETINAL DETACHMENT

34.  Stanford Keratoprosthesis :-
 Kpro is based on a mechanically 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 Based Keratoprosthesis
 Designed to mimic the extra cellular Matrix of corneal
stroma
 Modified Keratoprosthesis Biomaterials with bio
active factors
Recent Advances

35.  Keratoprosthesis review by Kareem Waleed Hamimy
 Clinical Ophthalmology A Systemic approach ny
Kanski and Bowling 7th Edition
 Stallards Eye Surgery M J Roper-Hall 7th Edition
 UP Journal of Ophthalmology 2011
Referances

36. Thank You