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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-OCT1.Noninvasive histological analysis: Image quality is similar to living biopsy2.Reliable thickness measurement

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

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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

4Green arrows: flap interface, White arrows: Bowman layer

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

Results Case 1

Case 5

• 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)

Epithelium

Flap

• 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)

• Preop refraction• OD -11.00 +2.00x85• OS -10.00 +1.25x90

• Pachymetry 498/507 μm

White line corresponds to the UHR-OCT image

Case 7

• 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)

White line corresponds to the UHR-OCT image

*Epithelium

Flap

Residual epithelium at the side cut may be responsible for the

development of epithelial ingrowth and flap melt in FS-LASIK patients

Case 7

• 29 y/o ♂ patient operated with Intralase 30 kHz FL.

• Patient had suction loss during flap preparation

Red arrows: Flap irregularity due to suction loss

oUHR-OCT was performed before the flap was lifted

oUHR-OCT images confirmed that the structure and integrity of the flap was normal

oFlap lift and excimer laser was completed without any complication

Case 9

Case 11• 27 y/o ♀• Epithelial ingrowth after LASIK

enhancement

• UHR-OCT images demonstrate histological structure of the ingrowth in detail (white arrow)

• 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

OD OS

Case 14*

* BCL

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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.

o 4 month post-LASIK refraction was OD -2.25 +1.00x90, OS -1.0 D sphere

oBSCVA was 20/25 OUoSlit lamp showed interface haze with a

granular appearance.o Time domain OCT revealed flap

thickness of 73 μm & 81 μm OU.

• 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

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

Case 15

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

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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

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