Effect of an irregular anterior surface on a lamellar femtosecond

laser cut

Robert E. Fintelmann, MDMichele M. Bloomer, MD

Bennie H. Jeng, MD

Authors have no financial interest

Department of Ophthalmology University of California San Francisco

Jengb@vision.ucsf.edu

First femtosecond laser approved in 2000 to create lamellar cuts for LASIK

Now being used for Anterior and posterior lamellar keratoplastyCustomized trephination for penetrating

keratoplastyTunnel creation for intracorneal ring

segmentsAstigmatic 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 createdRectangle at 210µmManual 2.5 mm punchManual 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

ResultsFemtosecond 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

DiscussionFemtosecond 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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