Effect of an irregular anterior surface on a lamellar femtosecond laser cut Robert E. Fintelmann, MD Michele M. Bloomer, MD Bennie H. Jeng, MD Authors have no financial interest Department of Ophthalmology University of California San Francisco
First femtosecond laser approved in 2000 to create lamellar cuts for LASIK Now being used for Anterior and posterior lamellar keratoplasty Customized trephination for penetrating keratoplasty Tunnel creation for intracorneal ring segments Astigmatic keratotomy Introduction
Purpose To determine if the femtosecond laser be used to create reliable cuts under an irregular corneal surface.
Methods Three types of defects created Rectangle at 210µm Manual 2.5 mm punch Manual triangular defect Three corneas masked with hydroxypropylmethylcellulose Three corneas without masking agent
Lamellar cuts created with femtosecond laser (300µm depth, 9mm Diameter, power 3mJ, IntraLase, Model FS60, software v 1.12 Abbott Medical optics, Abbott Park, IL) Corneas examined with ocular coherence tomography (RTVue SD-OCT with CAM-L lens) (Figure 1) All corneas were then fixed in formaldehyde, cut through the created defect and examined under the microscope
Figure 1: OCT of Defects En face OCT of rectangle Transverse OCT of rectangle
Results Femtosecond laser creates a smooth cut under irregular surfaces (Figure 2) Irregularities on the surface can lead to differences in thickness in the bed (Figure 3) No difference in bed appearance between masked and unmasked corneas
Figure 2: OCT of bed Thinning of bed under defect Bed under punch Bed under rectangle
Figure 3: Histopathology of cornea under defect Thicker bed outside area of defect Thinner bed in area under defect
Discussion Femtosecond lasers can help changing an irregular surface into a smooth bed for a corneal transplant Small study size insufficient to quantify the variability in the beds Masking agent does not appear to be necessary for producing regular beds
A corneal graft with a regular surface placed into the now smoother bed may give a good clinical outcome
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