High Definition Video Exploration of Epi-LASIK Surgery and Bowman’s Membrane Using the Moria System

June 29, 2008 By d p

High Definition Video Exploration of Epi-LASIK Surgery and Bowman’s Membrane Using the Moria System

James S. Lewis, MD | Elkins Park, PA 19027 USA

Purpose:

To investigate the Moria Epi-LASIK microkeratome and the nature of the surface it leaves behind.

Method:

High Definition surgical video was gathered during a number of Epi-LASIK procedures. The Ikegami 20-DI 2-chip HD camera mounted on a standard Zeiss Operating Microscope collected uncompressed video directly to a 6 terrabyte RAID. Video was captured in 12-bit color using a PCIe card from BlackMagicDesign. Final Cut Pro Studio 2 was used to edit the video. Enhanced video imaging (EVI) was achieved through the construction of a custom filter (video transform) written by the author.

Results:

The Moria system elegantly cleaves a continuous flap of epithelium from Bowman’s membrane. The surface left behind by the Moria Epi-LASIK microkeratome is pristine. EVI effectively grades the corneal stromal texture in Epi-LASIK, SBK, and LASIK.

Conclusion:

The surface quality of Bowman’s membrane is much smoother than the stromal surface produced by mechanical or femtosecond laser microkeratomes.

This may explain why the image quality following Epi-LASIK is superior.

Moria Epi-LASIK Microkeratome (row 1)

Moria Epi-LASIK Microkeratome (row 2)

Bowman’s membrane after Epi-LASIK pass (row 3)

Bowman’s membrane after Epi-LASIK pass (row 4)

Bowman’s membrane after Epi-LASIK pass (row 5)

Bowman’s membrane after Epi-LASIK pass (row 6)

Bowman’s membrane after Epi-LASIK pass (row 7)

Abstract number:005834
Title: Very thin flap LASIK using the Moria One Use Plus 90 Microkeratome
Presenting / First Author: Lewis
Poster Code: RS-D2-278
Panel No.: 278
Presentation Day: Jun 29, 2008
Attendance Schedule: 1600-1730

Abstract number:005837
Title: High Definition Video Exploration of Epi-LASIK Surgery and Bowman’s Membrane using the Moria System
Presenting / First Author: Lewis
Poster Code: RS-D2-279
Panel No.: 279
Presentation Day: Jun 29, 2008
Attendance Schedule: 1600-1730

Very Thin Flap LASIK using the Moria One Use Plus (OUP) 90 Microkeratome

June 29, 2008 By d p

Very Thin Flap LASIK using the Moria One Use Plus (OUP) 90 Microkeratome

James S. Lewis, MD | Elkins Park, PA 19027 USA

Purpose:

To determine the average central flap thickness created by the Moria OUP SBK microkeratome.

Method:

Independent masked physician operators captured multiple Visante™ images (Zeiss: Anterior Segment Ocular Coherence Tomography) at several intervals after surgery to accurately measure the central flap thickness of a large sample of consecutive patients.

Results:

The Moria OUP SBK reliably fashioned flaps of 99 microns OD and 97 OS with less than 10 µicrons of standard deviation.

Conclusion:

Femtosecond lasers have been promoted as the only device capable of achieving SBK (Sub-Bowman’s Keratomileusis). This assertion has been shown to be false. Moria’s OUP SBK microkeratome has created true SBK flaps in a reliable and consistent manner. Free caps, stria, buttonholes, and epithelial injury have not occurred. Furthermore, the complications and costs associated with femtosecond flap creation are avoided.

Central corneal flap thickness measured at least one week after surgery using a Zeiss Anterior Segment OCT (Visante™) and confirmed by two independent masked eye physicians demonstrated a mean of 99.22 microns [standard deviation = 8.87] in the right eye. Using the same blade for the second eye a slightly thinner mean left flap thickness of 97.15 micron [standard deviation = 10.39] was found.

When patients with longer followup were segregated a different range of values was found. Presumeably, by this time the cornea was completely deturgessed and more closely represented the true and final central flap thickness. The right eyes averaged 97.35 microns [standard deviation = 7.8] and the left eyes averaged 97.07 microns [standard deviation = 11.08].

True to the nature of a mechanical microkeratome, the Moria OUP SBK microkeratome exhibits a semi-planar flap profile. Flap thickness measurements at 3 mm temporal to the corneal apex and 3 mm nasal to the apex along the horizontal meridian demonstrated a 15% increase in flap thickness regardless of the location of the hinge. This contour is most accurately described as semi-planar. The non-planar profile may actually enhance flap stability while minimzing the all important central corneal flap thickness.

Over 500 Visante images were measured and re-measured to insure accuracy. The Visante™ flap tool determined the corneal surfaces. The placement of the flap indicator was manually adjusted only if the pattern recognition software failed. In this example the peripheral flap thickness was 107 µicrons when measured 3 mm nasal to the corneal apex. The flap thickness was 106 µicrons when measured 3 mm temporal to the corneal apex. The central corneal flap thickness was 96 µicrons.

OD using Moria OUP SBK Microkeratome

The automated Moria OUP SBK has an analog hinge setting to correct for flat and steep corneas. Unlike femtosecond lasers the flap is easily lifted with a single motion.

Following laser application the uniform nature of the underlying stromal bed is evident. The thin but resilient sub-100 µicron flap assumes a perfectly smooth appearance upon re-apposition.

OS using Moria OUP SBK Microkeratome

You can visually appreciate the uniformity and svelt nature of these flaps in the high resolution images above. This is the appearance of a sub-100 µicron corneal flap. The residual stromal bed and underside of the flap manifest an identical texture.

This SBK flap dehydrates and stiffens during the brief time required for excimer laser
photoablation. Simple rehydration returns the tissue to its pliable state. The flap assumes its final position.

WOC June 29 2008 Presentation Supporting Video by James S. Lewis, MD

June 29, 2000 By d p

Supporting Video

for Dr. Lewis’s WOC presentation

SBK using a Femtosecond Laser (EVI)

EVI or Enhanced Video Imaging brings out the corneal stromal texture using a specialized digital video filter.

Epi-LASIK using the Moria Microkeratome (EVI)

EVI shows the smooth texture of Bowman’s membrane. Compare this with SBK above.

Texture of Bowman’s Membrane in Moria Epi-LASIK

A fiber optic light source emphasis the smooth, mirror like surface of Bowman’s immediately after the microkeratome pass.

Moria’s Epi-LASIK Microkeratome Pass

Although we discard the epithelial flap, it is harvested undamaged in this technique.

Amoil’s Brush Exposes Bowman’s Membrane in an RK Patient

The texture of Bowman’s membrane appears less smooth in this case than it appears in the Epi-LASIK surgery above.

SBK

Standard LASIK cases from 1999 to 2002 (EVI)

EVI demonstrates a very roughened corneal stromal surface in these older surgical procedures.

Poster Code: RS-D2-278, Panel No.:278, Presentation Day: June 29,2008