Ultra-High-Resolution Optical Coherence Tomography Imaging in LASIK

1. Ultra-High-Resolution Optical Coherence Tomography Imaging in LASIK Volkan Hurmeric MD Jianhua Wang PhD, MD Sonia H. Yoo MD ASCRS San Diego 2011 Financial DisclosureSonia H. Yoo is a consultant for AMO/Intralase Volkan Hurmeric, Jianhua Wang have no financial interest in the subject matter of this e-poster

2. Purpose: is to investigate clinical applications of spectral domain ultra-high-resolution optical coherence tomography (UHR-OCT) imaging in femtosecond laser assisted LASIK (FS-LASIK) patients. • Anterior segment scanning • Center wavelength: 840nm • Bandwidth: 100nm • Scan depth: 3mm • Scan width: up to 15mm • Scan speed: 24 frames per second • Axial resolution: ~3 µm Advantage of UHR-OCT Noninvasive histological analysis: Image quality is similar to living biopsy Reliable thickness measurement

3. Methods: 28 patients who underwent FS-LASIK surgery were enrolled in the study. Study group: 15 patients • 9 patients (9 eyes) were scanned immediately after femtosecond flap preparation • 6 patients with opaque bubble layers (OBL), • 2 patients with epithelial defects • 1 patient with suction loss. • 6 patients (9 eyes) were scanned at postoperative period • 3 patients with epithelial ingrowth, • 2 patients with epithelial breakthrough, • 1 patient with post-LASIK haze Control group: • 13 patients, 22 eyes with uncomplicated FS-LASIK were scanned at postoperative day 1 • 6 ♂, 7♀ • Preoperative SE +3.00 / -8.00 dpt

4. Results Case 1 In 2 patients, OBL was located above the flap interface in UHR-OCT images. In these patients flap lift was unsuccessful due to incomplete lamellar dissection over the area of OBL Case 5 In 4 patients OBL was located under the flap interface. In these patients flaps were lifted without any complications Our experience suggests that OBLs located above the flap interface may be a sign of an undissected flap zone and a contraindication to flap lifting Green arrows: flap interface, White arrows: Bowman layer

5. Case 7 Epithelium Flap • Preop refraction • OD -11.00 +2.00x85 • OS -10.00 +1.25x90 • Pachymetry 498/507 μm • Surgical Plan • Flap creation with 30 kHz FL (without flap lift) • Implantable Collamer Lens (ICL) implantation • Flap lift + Excimer laser ablation (1 month after ICL) • Post-LASIK examination revealed epithelial irregularities OS • Epithelial irregularities were repositioned under the slit lamp with a forceps before UHR-OCT imaging • UHR-OCT images demonstrated residual epithelium penetrating into the side-cut (white arrow) White line corresponds to the UHR-OCT image

6. Case 7 Epithelium * Flap • 2 months post-LASIK exam revealed peripheral flap irregularity at the area with previous epi-defect (white arrow) • Patient had no complaints & UCDVA was 20/15 OU • UHR-OCT imaging demonstrated localized loss of flap tissue (asterix) Residual epithelium at the side cut may be responsible for the development of epithelial ingrowth and flap melt in FS-LASIK patients White line corresponds to the UHR-OCT image

7. 29 y/o ♂ patient operated with Intralase 30 kHz FL. • Patient had suction loss during flap preparation Case 9 • UHR-OCT was performed before the flap was lifted • UHR-OCT images confirmed that the structure and integrity of the flap was normal • Flap lift and excimer laser was completed without any complication Red arrows: Flap irregularity due to suction loss

8. Case 11 • 27 y/o ♀ • Epithelial ingrowth after LASIK enhancement • UHR-OCT images demonstrate histological structure of the ingrowth in detail (white arrow)

9. Case 14 * OD OS * BCL • 25 y/o ♀underwent FS-LASIK for -8.25 / -9.00 D. • Flap thickness was 110 μm (OD) • Patient had bilateral corneal scars due to previous adenoviral infection • Patient had epithelial breakthrough (red arrow) during FS flap preparation in the right eye • UHR-OCT imaging was performed in the left eye. At some points corneal scars were found to be deeper than expected (white arrow). • Flap thickness was adjusted to 130 microns and FS-LASIK was competed without any problem in the left eye

10. 42 y/o ♂ uncomplicated FS-LASIK for OD -9.00+1.00 X 95, OS -4.75+0.75X65 D • Intended flap thickness was 110 μm Case 15 • 4 month post-LASIK refraction was OD -2.25 +1.00x90, OS -1.0 D sphere • BSCVA was 20/25 OU • Slit lamp showed interface haze with a granular appearance. • Time domain OCT revealed flap thickness of 73 μm & 81 μm OU. UHR-OCT demonstrated focal breaks (white arrows) in Bowman layer and localized thickening of epithelial basement membrane. These areas were corresponded to the areas where the haze was most severe. The association of corneal haze with areas of disruption of Bowman`s membrane has not been observed earlier. This could potentially be a factor in determining the severity and extent of corneal haze in FS-LASIK

11. Control group • 22 eyes with uncomplicated FS-LASIK were scanned at postoperative day 1 with UHR-OCT • All patients were operated with Intralase 30 kHz / Visx S4 • Flap thickness: 110 μm • Flap diameter: 9 mm • Raster energy: 1.9 μm • In all patients flap structure was normal • None of the patients had residual epithelium in the side cut. • None of the patients had focal breaks at Bowman layer. • None of the patients developed epithelial ingrowth or flap melt at postoperative 1 month

12. Conclusions • UHR-OCT helps us to document in-vivo morphology of the cornea after refractive surgery similar to a living biopsy • UHR-OCT can be used to prevent flap related complications in FS-LASIK • UHR-OCT is gives us new information about the development of complications in refractive surgery • UHR-OCT will help us to better understand wound structure and wound healing after refractive surgery • Future studies are needed to confirm new clinical applications of high-resolution imaging in refractive surgery