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Scanning electron microscopic evaluation of the surface characteristics of 4 microkeratome systems in human corneas
M Bowes Hamill1, Thomas Kohnen
1Cullen Eye Institute, Baylor College of Medicine, Department of Ophthalmology, Houston, Texas 77030, USA. mhamill@bcm.tmc.edu
Purpose:
To evaluate the surface characteristics of keratectomy specimens created with 4 microkeratomes by scanning electron microscopy (SEM).
Setting:
Two university institutions.
Methods:
Keratectomies were performed in 10 fresh, unfrozen human eyes with 1 of 4 microkeratomes: the Draeger rotary microkeratome (Storz Instruments), the Universalkeratome (Phoenix), the Automated Corneal Shaper (Bausch & Lomb), or the Hansatome (Bausch & Lomb). The beds and edges of the keratectomy specimens were then examined by SEM. Standardized photographs were taken, and the surface and cut-edge characteristics of the keratectomies were compared.
Results:
Irregularities were noted in the cut edges of Bowman's membrane and the surface of the keratectomy beds with all instruments. The irregularities were most prominent in corneas cut with the Draeger instrument and least prominent in those cut with the Universalkeratome. The serrations in Bowman's membrane and the irregularities in the keratectomy bed appeared to be related to the blade movement in oscillating blade instruments.
Conclusions:
All 4 microkeratomes caused some degree of surface irregularity. The Draeger microkeratome, which uses a continuously rotating blade, resulted in the greatest number of Bowman's membrane serrations and irregularities in the keratectomy bed. The tissue irregularities may be related to the development of pressure ridges ahead of the blade. In instruments that use an oscillating blade, chatter marks appear to be related to the reciprocating movement of the blade as it travels across the corneal stroma.