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

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 Descemet’s membrane and endothelium • Eliminates endothelial rejection • Enhances long term graft survival • Descemet’s 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 2007;26:59–64 2. Price FW, Price MO. Descemet’s stripping with endothelial keratoplasty in 200 eyes: early challenges and techniques to enhance donor adherence. J CataractRefract Surg. 2006;32(3):411-418

3. Method • Purpose • To quantify changes in host and donor corneal profile after lamellar proceduresusing 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 <0.05 considered significant 1.Anwar M, Teichmann KD. Big-bubble technique to bare Descemet’s membrane in anterior lamellar keratoplasty. J Cataract Refract Surg 2002;28:398–403 2.Melles GRJ, Lander F, Rietveld FJR, et al. A new surgical technique for deep stromal anterior lamellar keratoplasty. Br J Ophthalmol. 1999;83: 327–333.

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 0.0mm -2.0mm +2.0mm

5. DALK RESULTS • 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)(P> 0.05) • Mean posterior lamellar thickness (DM/endothelium) changed from 46.7 µm(±12) to 27 µm (±5) (P>0.05) • 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 P=0.07 No of Patients P=0.08 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 • 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 n=1 • Mean BCSVA (logMAR) 1.23 (± 0.33) pre op improved to mean of 0.83 (± 0.36) at last post operative visit (P=0.06) • 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 (p=0.09) • Peripheral graft rates changed • most during 1st month • Peripheral graft thinning rate • was 104.8µm/month compared • to 24.1µm/month centrally • (p<0.01) Table 3 comparing mean change in lamellar thickness with time Graph 3 illustrates change in various corneal lamellae with time

10. 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 Viscoelastic in angle Clear angle post washout/synechiolysis

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 2009;148:32–37. 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. 2008;126(8):1052-1055