Evaluation of Corneal Graft Profile Following Deep Anterior and Posterior Lamellar Keratoplasty Procedures by Fourier-Domain Optical Coherence Tomography

1
Evaluation of Corneal Graft Profile Following
Deep Anterior and Posterior Lamellar Keratoplasty
Procedures by Fourier-Domain Optical Coherence
Tomography

• Miss Tarang Gupta MB BS MRCOphth
• Mr Dipak Parmar BSc (Hons),
• MB BS(london) FRCOphth (UK)

There are no financial disclosures for this study
2
Introduction

• Recent emergence of lamellar graft techniques
  allows selective removal of only diseased tissue
• Deep anterior lamellar keratoplasty (DALK)1
• Retains host Descemets membrane and endothelium
• Eliminates endothelial rejection
• Enhances long term graft survival
• Descemets stripping endothelial keratoplasty
  (DSEK) targets only abnormal endothelium 2
• Benefits include
• Intra operative closed globe surgery
• Preserved corneal integrity and tensile strength
• Rapid visual recovery
• Fourier domain OCT allows for faster A scan
  acquisition rate
• 65 times faster than time domain systems
• Less variability with patient movement
• Depth resolution of 5µm
• Useful for allowing measurement of separate
  lamellar components

1. BA Noble et al Deep Anterior Lamellar
Keratoplasty (DALK) Visual Outcome and
Complications for a Heterogeneous Group of
Corneal Pathologies Cornea 2007265964
2. Price FW, Price MO. Descemets stripping with
endothelial keratoplasty in 200 eyes early
challenges and techniques to enhance donor
adherence. J CataractRefract Surg.
200632(3)411-418
3
Method

• Purpose
• To quantify changes in host and donor corneal
  profile after lamellar procedures using Fourier
  domain OCT
• Method
• Prospective case series of patients undergoing
  lamellar graft procedures between Jan 09 to Dec
  09
• All patients underwent complete biomicroscopy and
  fundus examination.
• DALK was performed with big bubble of Anwar
  technique1, utilizing manual dissection of host
  and donor tissue (on an artificial anterior
  chamber)
• DSEK donor graft was prepared manually with 3
  DORC blades (Zuidland, The Netherlands) on an
  artificial anterior chamber employing Melles
  technique2.
• Measured variables included best spectacle VA
  (logMAR), refractive spherical equivalent,
  anterior corneal keratometric values and OCT
  findings
• OCT scans were taken at week 1, 1 month, 3 months
  and 6 months
• All patients received post operative topical
  steroids and antibiotics QDS for 1 month.
• Statistics
• Student paired T-test and regression analysis was
  used.
• P value lt0.05 considered significant

1.Anwar M, Teichmann KD. Big-bubble technique to
bare Descemets membrane in anterior lamellar
keratoplasty. J Cataract Refract Surg
200228398403
2.Melles GRJ, Lander F, Rietveld FJR, et al. A
new surgical technique for deep stromal anterior
lamellar keratoplasty. Br J Ophthalmol. 199983
327333.
4
OCT measurements

• The interface between host stroma and graft
  tissue was identified by direct visualisation
• Corneal lamellar thickness was measured using the
  callipers provided by OCT software.
• All OCT images were of sufficient quality to be
  analysed.
• All measurements were made by one investigator
• Corneal thickness measurements were taken at the
  vertex (centrally) and peripheral scans 2mm
  nasal and temporal to the vertex

5
DALK RESULTS
Characteristic Number ()
Age years (mean SD) 52.2 21.7
Follow up months (mean SD) 12.3 7.8
Male/female 3/6 (33/66)
Right/left eye 6/3 (66/33)
Diagnosis
Keratoconus 3 (33)
HSK keratitis 3 (33)
Macular dystrophy 2 (22)
Central clouding dystrophy of Francois 1 (12)
Graft size
8.25mm 2 (22)
8.5mm 7 (78)
Suturing
Continuous 1 (12)
Interrupted 8 (88)

• 9 patients included
• BCVA better than 6/12 (logMAR 0.30) in 67 (2/3)
• Mean BCVA 0.42 (6/15)
• Mean keratometric value changed from 2.56 pre op
  to 3.02D post operatively (P 0.58
• Mean anterior lamellar thickness changed from
  641µm (48) to 546 µm (21)(Pgt 0.05)
• Mean posterior lamellar thickness
  (DM/endothelium) changed from 46.7 µm(12) to 27
  µm (5) (Pgt0.05)
• Average final post op total central corneal
  thickness was 548.62 µm (range 515.50 591.50)

Table 1 illustrates DALK patient characteristics
6
DALK RESULTS
No of Patients
Graph 1 illustrates the change in best spectacle
correct visual acuity (BSCVA) between pre
operative and last post operative evaluation
Graph 2 shows the change in corneal lamellar
thickness over time
7
Serial OCTs of a patient with a central herpetic
scar undergoing DALK
Table 2 illustrating complications and management
complication Rate Action
Descemets micro-perforation 2 (22) Conservative
Graft rejection (suture vascularisation only) 1 (11) Topical steroids resolved
Graft detachment 2 (22) Air reinjection. 1 failed 1 resolved
Double AC 1 (11) Air reinjection corneal massage resolved
Epithelial defect 1 (11) BCL
Loose suture 3 (33) Suture removal
Gaping corneal cataract wound following suture removal 1 (11) Wound re-sutured
Steroid response (raised IOP) 1 (11) Switch to alternative topical steroid

• Pre op OCT
• Increased stromal
• reflectivity in the herpetic
• scar

• 1 week post op OCT
• Integrated graft.
• Small change in optical
• density identifying
• host/donor junction

• 3 month post op OCT
• Reduced junctional
• reflectivity
• Homogenous
• stroma

8
DSEK Results

• 4 patients
• All women right eyes
• Mean age at surgery 75.2 (SD 6.7)
• Underlying aetiology
• Pseudophakic Bullous Keratopathy n 3
• Fuchs Endothelial Dystrophy n1
• Mean BCSVA (logMAR) 1.23 ( 0.33) pre op improved
  to mean of 0.83 ( 0.36) at last post operative
  visit (P0.06)
• Mean difference between pre and post op BSCVA was
  gain of 2 lines Snellen acuity

9
DSEK Results

• Peripheral graft thickness
• appears to decrease faster than
• central measurements (p0.09)
• Peripheral graft rates changed
• most during 1st month
• Peripheral graft thinning rate
• was 104.8µm/month compared
• to 24.1µm/month centrally
• (plt0.01)

Table 3 comparing mean change in lamellar
thickness with time
Graph 3 illustrates change in various corneal
lamellae with time
Central graft thickness (µm SD) Central total thickness (µm SD) Peripheral graft thickness (µm SD) Peripheral total thickness (µm SD) Epithelial thickness (µm SD)
Week 1 175 ( 64.7) 763.5 ( 93.4) 495.5 (279) 1249.75 (344.4) 53.75 (30.9)
Month 1 153 ( 76) 230.7 (56.5) 715.25 (84) 962.5 (141.4) 67.0 (28.0)
Month 3 103 (28.8) 642.75 (78.1) 181 (29.9) 819.75 (90.3) 55.25 (23.3)
P value 0.03 0.18 0.04 0.03 0.47
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DSEK Results
Serial change in DSEK lamella with time
Correlation between a) central corneal thickness
and best spectacle corrected visual acuity
(BSCVA) 6 months after DSEK and b) between
peripheral thickness and BSCVA
Day 1
Pearson correlation coefficient r 0.54
Pearson correlation coefficient r 0.39
Week 1
Month 1
Month 3
11
Benefits of OCT Imaging

• High IOP 2 days post uncomplicated DSEK
• Thought to be due to migrating air bubble behind
  iris causing pupil block
• OCT showed material occluding angle
• ?sequestered viscoelastic
• Patient underwent synechiolysis
• Post procedure OCT confirms clear angle IOP
  normal
• Patient undergoing re-do DALK. Day 1 post op
  graft looks attached clinically
• OCT shows showed residual interface material
  (retained viscoelastic)
• Washout in theatre
• Adherent graft post op

12
Discussion

• We have demonstrated the benefits of Fourier
  domain OCT in imaging corneal layers following
  lamellar graft procedures.
• In particular they allowed
• Day 1 post operative non contact assessment of
  graft apposition and serial measurements during
  follow up
• Epithelial layer measurements,
• Assessment of graft host interface with greater
  clarity
• Assessment of anterior chamber angle crowding
• Assessment of graft dislocation and donor
  apposition (especially when corneal oedema
  precludes direct visualisation)
• In our study we have demonstrated similar
  findings of preferential peripheral graft
  thinning as other authors
• Pascuale et al showed peripheral graft may
  continue to thin and remodel beyond 6 months post
  operatively.
• Changes in peripheral graft thickness have been
  correlated with the induced hyperopic shift.2
• Thickened peripheral graft may increase risk of
  anterior chamber angle crowding
• LIMITATIONS
• Measurements are taken by visually assessing the
  transition of lamellae
• Optical density and reflectivity are qualitative
  measures it remains to be seen whether these
  methods are reproducible and accurate

1. Pascuale et al Corneal Deturgescence after
Descemet Stripping Automated Endothelial
Keratoplasty Evaluated by Visante Anterior
Segment Optical Coherence Tomography Am J
Ophthalmol 20091483237.
2. Yoo et al One-Year Results and Anterior
Segment Optical Coherence Tomography Findings of
Descemet Stripping Automated Endothelial
Keratoplasty Combined With Phacoemulsification
Arch Ophthalmol. 2008126(8)1052-1055