Accuracy of Alcon WaveLight^® EX500 optical pachymetry during LASIK

Figures & data

Figure 1 High-definition optical coherence tomography at center of cornea.

Note: Top caliper measures flap thickness at 132 μm and bottom caliper measures residual stromal bed thickness at 346 μm.
Abbreviations: T, temporal; N, nasal.

Figure 2 High-definition optical coherence tomography measurements.

Notes: Example of measurements across the cornea. Five measurements are spaced approximately 1.5 mm apart from each another, with the center measurement at the center of the cornea. Top calipers measure flap thickness. Bottom calipers measure residual stromal bed thickness.
Abbreviations: T, temporal; N, nasal.

Table 1 Timing of OCT measurements

Months after surgery	Eyes, n	Percentage
1	24	53%
2–3	7	16%
4–6	6	13%
14–17	8	18%
Total	45	100%

Abbreviation: OCT, optical coherence tomography.

Table 2 Flap- and RSB-thickness comparison

Measure	Mean (mm)	95% CI	P-value
FT difference: FS200 – EX500	9	6–12	<0.001
FT difference: FS200 – OCT	−0.2	−2 to 2	0.87
RSB difference: EX500 (programmed) – EX500	15	8–22	<0.001
RSB difference: EX500 (programmed) – OCT	−0.3	−5 to 4	0.89

Note: Comparison of difference in flap and RSB measurements between FS200 and EX500 using OCT.

Abbreviations: FT, flap thickness; OCT, optical coherence tomography; RSB, residual stromal bed.

Table 3 Summary of overall clinical outcome of LASIK patients

Measure	n*	Mean	SD	Minimum	Maximum
UCVA: logMAR (Snellen)	88	−0.024 (20/19)	0.17	−0.165 (20/15 +2)	0.66 (20/80 −1)
BCVA: logMAR (Snellen)	71	−0.08 (20/17)	0.07	−0.125 (20/15)	0.14 (20/25 −2)
Spherical equivalent	79	−0.18	0.44	−2	0.5
Sphere	77	−0.26	0.24	0	1
Cylinder	77	0.15	0.45	−2	0.25

Note:

* Number of individual eyes measured.

Abbreviations: LASIK, laser-assisted in situ keratomileusis; UCVA, uncorrected visual acuity; BCVA, best-corrected visual acuity; logMAR, logarithm of minimum angle of resolution.