Technology:

Pachymetric Topography of LASIK

"C12" display of the cornea of a patient before and six months after LASIK OS. The "C12" display is set out to be read by temporal grouping (columns) or anatomical grouping (rows). All 12 maps are pachymetric representations of particular corneal layers depicted on a color scale in µm.
The pre-operative epithelial
(1) stromal
(2) and full corneal
(3) thickness maps appear in the first column. To the right of each of these maps (column two) are the pachymetric maps after LASIK of epithelium
(4), stroma
(5) and full cornea
(6) on identical color scales for direct
C 12 - Pachymetric Topography
Click for larger image >>

comparison to the pre-operative state.The third column depicts calculated maps only. The calculated epithelial change map
(7) is derived by point-by-point subtraction of the pre-operative from the post-operative epithelial pachymetric map. Thus the epithelial change map shows on a color scale the number of µm increase in epithelial thickness due to surgery. The area of epithelial thickening is confined to the ablation zone or the zone of surgical corneal flattening. The calculated stromal change map
(8) is derived in point-by-point subtraction of the post-operative from the pre-operative stromal pachymetric map. Thus the stromal thickness change map shows on a color scale the number of stromal µm decrease due to surgery in a topographic fashion and hence represents the ablation volume of tissue. The calculated map of the "original flap"
(9) is derived by addition of the pre-operative epithelial thickness profile (1) to the post-operative "stromal component of the flap" (12). The post-operative thickness map of the flap
(10) includes epithelial changes. Thickness mapping of the residual stromal layer comprising all stroma beneath and peripheral to the flap is shown in map 11. This map can be critically important in the determination of adequacy of the thickness of the stromal bed for further LASIK enhancement surgery under the flap, because the thinnest point is not always located centrally and may be missed by any form of intra-operative single-point measurement of the bed

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	"C12" display of the cornea of a patient before and six months after LASIK OS. The "C12" display is set out to be read by temporal grouping (columns) or anatomical grouping (rows). All 12 maps are pachymetric representations of particular corneal layers depicted on a color scale in µm. The pre-operative epithelial (1) stromal (2) and full corneal (3) thickness maps appear in the first column. To the right of each of these maps (column two) are the pachymetric maps after LASIK of epithelium (4), stroma (5) and full cornea (6) on identical color scales for direct	Click for larger image >>
	comparison to the pre-operative state.The third column depicts calculated maps only. The calculated epithelial change map (7) is derived by point-by-point subtraction of the pre-operative from the post-operative epithelial pachymetric map. Thus the epithelial change map shows on a color scale the number of µm increase in epithelial thickness due to surgery. The area of epithelial thickening is confined to the ablation zone or the zone of surgical corneal flattening. The calculated stromal change map (8) is derived in point-by-point subtraction of the post-operative from the pre-operative stromal pachymetric map. Thus the stromal thickness change map shows on a color scale the number of stromal µm decrease due to surgery in a topographic fashion and hence represents the ablation volume of tissue. The calculated map of the "original flap" (9) is derived by addition of the pre-operative epithelial thickness profile (1) to the post-operative "stromal component of the flap" (12). The post-operative thickness map of the flap (10) includes epithelial changes. Thickness mapping of the residual stromal layer comprising all stroma beneath and peripheral to the flap is shown in map 11. This map can be critically important in the determination of adequacy of the thickness of the stromal bed for further LASIK enhancement surgery under the flap, because the thinnest point is not always located centrally and may be missed by any form of intra-operative single-point measurement of the bed
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