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Plasma Knife versus Conventional Scissors for In-situ Excision of Donor Corneoscleral buttonfor the purpose of Penetrating Keratoplasty

Ashutosh Agarwal1, Radhika Tandon1, Namrata Sharma1, Jeewan S. Titiyal1, Rasik B. Vajpayee1,2

1Department of Ophthalmology, All India Institute Medical Sciences, New Delhi, India; 2Centre for Eye Research, University of Melbourne, Melbourne, Australia

The authors have no financial interest in the subject matter of this poster.

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Introduction In India

Prevalence of corneal blindness is approximately 6.8 million of which about 1 million are bilaterally blind and 40,000 fresh cases are added every year.Nearly 3.5 million good quality cornea donors are required, quite challenging with an annual meagre collection of 20,000 eyes. Rajesh Sinha, Namrata Sharma et al .Corneal Blindness—Present Status I CATARACT & REFRACTIVE SURGERY TODAY ,OCTOBER 2005: 59-64

Major obstacles include ineffective procurement of donated corneas as also failure to successfully convince the potential donors.Tandon et al.. Factors Affecting Eye Donation From Postmortem Cases in tertiary Care Hospital (Cornea 2004;23:597–601)

In situ excision of donor cornea (compared to conventional Whole Globe Enucleation) ) is a

1. newer technique (last one decade)

2. swift and precise extraction with least damage to endothelium

3. prolific in enhancing the quality and utilization of donor corneas by reducing death preservation time

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Author/Group Study Design Infection Tissue Quality Comments

Rootman et al , Cornea 2007

468 corneas-300 by in-situ & 168

enucleated over 4 yrs

Lower incidence mod. to severe

haze & folds in DM

No difference inmean ECD

No difference intissue trauma level

mean ECDPlaced in storage medium

earlier -- improve the overall initial quality.

Everts RJ et al –Retrospective studyCultures of post- PK CorneoScleral rim

PPV and sensitivity for

predicting subsequent

endopthalmitis were both zero

Post-op endopthalmitis optimum specimens

collected treatment based on known

eye pathogens

Vishal Jhanji et al, Cornea 2008

Prospective RCT100eyes—50 in-situ &

50 enucleated

Risk of contamination is

equally low in skilled hands

Initial cell loss and corneal thickness

higher

3 mths Post op comparable

ECDGC

Median VAMore Acceptable

Review of Literature: In-situ versus Enucleation

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Review of Literature (contd…)Plasma Knife

Cutting 1. Safe, quick, atraumatic

2. By tissue ablation

3. Resistance free (minimum tissue traction)

4. No tactile sensation of making incision

5. Tip does not adhere to tissue

6. Lower frequency and power compared to laser

7. Application in a wide range of ocular surgeries Plasma Knife can produce sharp cuts in the cornea while minimal tissue damage seen beyond edges of the incisionPeponis et al ,Fugo Blade in Corneal Surgery ;Cornea 2006;25;206-208

Aims and Objectives

Systematic comparative prospective evaluation of two techniques of harvesting donor cornea by in-situ method with respect to:

Donor tissue microbiological contaminationCorneal endothelium in the donor and also the recipient following transplantationGraft infectionGraft outcome in the recipient at three months

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MethodologyDonor selection

YES• Age <60 years• DPT < 6 hours

NO• Aphakia / Pseudophakia• Putting on ventilator for long time (>72hrs)• Hypotension

Recipient Selection Non-vascularized corneal opacity

Written consent from legal next of kin

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MethodologyEyes were systematically randomized (Right/Left) for both type

(Plasma Knife or Corneoscleral Scissors) and sequence of extraction.

The eye cleaned externally with povidone iodine 10% for 3 mins

Irrigation of conjunctival sac with saline

Povidone 10% instilled in conjunctival sac and washed off with saline

The eye cleaned and draped

1st limbal swab for culture

Gatifloxacin 0.3% eye drops instilled

Cont………

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MethodologyAfter doing 360° peritomy, a scleral incision made (in conventional method)

with surgical blade 3mm from limbus taking care not to enter the choroid

Corneoscleral rim excised using curved corneal scissors/ or Plasma Knife

Careful separation of cornea from underlying tissue care not to damage endothelium

Second swab taken(S2)

Eyes put in McKarey Kauffman (MK) medium (transferred to eye bank)

A transparent plastic cap put over the eye

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MethodologyComparative evaluation done for 2 techniques of in-situ excision i.e. Plasma Knife assisted versus conventional scissors

Preoperative EvaluationDonor tissue microbiological contamination (before and after excision)Evaluation and grading of donor cornea on Slit Lamp

Post operative follow up of graft recipientsPost-op. corneal endothelial statusGraft status at 3 months in terms of Central Corneal Thickness, Graft Clarity and Spectacle Corrected Visual Acuity Any associated complications like graft infection/ graft failure etc.

RESULTS: Donor EvaluationComparative Evaluation Plasma Knife Scissors Statistical

Coefficient

No. of Donors 15(13+2 single eyed donors) 13

p= 0.597(FET)

Median Age (years) 50 50 p=0.889(MWT)

Endothelial Cell Density (cells /mm2) 2181.27±286.30 2103.15±186.75p=0.409(MWT)

Death Preservation Time (hrs) 4.70± 1.39 4.75 ±1.48p=0.924(MWT)

Baseline Microbial Contamination (before extraction) 11/15 10/13

p= 0.843(CST)

Microbial Contamination after extraction 9/15 7/13

p= 1.00 (FET)

FET=Fischer Exact Test, MWT=Mann Witney Test, CST=Chi Square Test

RESULTS: Recipient EvaluationComparative Evaluation

Plasma Knife Day 7 Day 90

Scissors Day 7 Day 90

Statistical Coefficient

Endothelial Cell Density 1821±226 1633±245 1800±193 1639±175

p7=0.982p90=0.612

(MWT)

Central Corneal Thickness 583.5±26.3 560.7±30.1 577.0± 21.9 586.62± 54.2

p7=0.519p90=0.240

(MWT)

Median Graft Clarity 3+ 4+ 4+ 4+p7=0.082p90=0.686

(FET)

Mean Spectacle Corrected Visual Acuity

0.101±0.07 0.305±0.12 0.091±0.09 0.315±0.23p7=0.500p90=0.667

(MWT)

Graft Complications Nil Nil Graft Infection (Pseudomonas) Nil p=0.464

(FET)

FET=Fischer Exact Test, MWT=Mann Witney Test, CST=Chi Square Test

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Conclusion

Plasma knife is a safe and effective equipment for in-situ extraction of donor corneoscleral rim.