1. The results of PTK using Fourier-Domain Optical Coherence Tomography for Granular Corneal Dystrophy Type 2 Eung Kweon Kim, MD, Ph.D 1 ; Tae-im Kim, MD, Ph.D 1 ; Jung Won Park, MD 2 ; Woosuk Chung, MD 3 1 Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea 2 Daegu Yonsei Eye Clinic, Daegu, Korea 3 Siloam Eye Hospital, Seoul, Korea The authors have no financial interest

2. Page  2 Introduction  Measuring the exact depth of deposits in granular corneal dystrophy type 2 (GCD2) may allow us not only improve vision by removing most vision threatening deposits, but also save corneal tissue as much as possible during the procedure.

3. Page  3 The depth of corneal deposit determines treatment strategy and depth of ablation Endothelium ~ lower margin of deposits : 269µm  DLKP Long lattice deposits reaches almost to D’s membrane and pushed the endothelium back  PKP 28 y-o female 8 years after LASIK Upper margin of deposit ~ Bowman’s layer: 31µm Endothelium ~ lower margin of deposits: 363µm  amputating the LASIK flap

4. Page  4 Purpose  We compared the depths of corneal deposits in GCD2 patient using a RTVue-100 FD-OCT and the actually ablated depths of deposits.  From October 2008 to October 2009  21 eyes of GCD2 patients who undertaken phototherapeutic keratectomy (PTK ) RTVue (Optovue Inc, Fremont, CA) Fourier domain OCT High speed and high resolution OCT Layer by layer assessment 3-D scanning

5. Page  5 Methods  Pre-operative measurements of deposits by FD-OCT Bowman’s layer ~ granular deposits or diffuse haze (without lattice deposits)  Step ladder ablation assisted by intra-operative slit lamp examination Intra-operative slit lamp examination was undertaken every 10 ㎛ of ablation. PTK was stopped when the diffuse haze and granular deposits removed.

6. Page  6 Intra-operative step ladder ablation assisted by slit-lamp examination Before ablation After 21 microns ablation After 31 microns ablation After 41 microns ablation

7. Page  7 (㎛)(㎛) (Patient) The minimal thickness of deposits, estimated depths of deposits by FD-OCT and the actually ablated thickness Results

8. Page  8 PatientFollow upBaselinePostoperative Deposit thickness by FD-OCT( ㎛ ) Actually ablated thickness( ㎛ ) No. MonthsBCVAUCVABCVAUCVA Min Max 190.4 0.80.5 5355 28 0.410.6535645 33 0.6 0.2 4140 46 0.20.3 106122105 58 0.40.9 10310972 680.80.61 4744 76 0.50.60.5 42 39 87 0.30.9 444752 930.30.20.4 317843 103 0.10.9 9788 113 0.50.9 75100 1230.050.10.6 316358 1330.2 0.7 5957 143 0.31 567259 153 0.50.8 5351 1610.8 0.3288850 1710.3 0.7 347250 1810.20.05 0.1 7271 1910.40.30.9 284730 200 0.4 0.5 7851 210 0.3 0.2314460 Follow up period, visual acuity, deposit thickness by FD-OCT and actually ablated thickness of all included patients. BCVA; best-corrected visual acuity, UCVA; uncorrected visual acuity,

9. Page  9 (㎛)(㎛) (Patient) Patient 1 Even deposits : 53 ~ 55 ㎛ by FD-OCT → Ablated thickness: 55 ㎛

10. Page  10 (㎛)(㎛) (Patient) Patient 9 Uneven deposits : 31 ~ 78 ㎛ by FD-OCT → Ablated thickness: 43 ㎛

11. Page  11  Deposit thickness by FD-OCT ≥ actually ablated depth It may be due to -Superficial part of opacity and corneal stroma was excised together when the epithelium removed. -We measured the maximal depth of corneal deposits when measuring FD-OCT  The depth of corneal deposits measured with FD-OCT before PTK corresponded well to the actually ablated depth with intra-operative slit lamp assisted method. Conclusion