TABLE 2.
COMPARISON OF NORMAL AND KERATOCONIC GROUP RESPONSES TO SIMULATED MYOPIC REFRACTIVE SURGERY (DEVIATION FROM PROGRAMMED CURVATURE CHANGE AND STRAIN VARIABLES)*
| GROUP | PREOP | PRK 4D | PRK 8D |
100 µM FLAP LASIK 4D |
100 µM FLAP LASIK 8D |
160 µM FLAP LASIK 4D |
160 µM FLAP LASIK 8D |
|
|---|---|---|---|---|---|---|---|---|
| Postop Refractive Error (D) | Norm (Group 0, n=10) | -- | 0.03 ± 0.03‡ | 0.06 ± 0.05‡ | −0.03 ± 0.03‡ | −0.12 ± 0.05‡ | −0.13 ± 0.04‡ | −0.33 ± 0.08‡ |
| KC (Group 3, n=12) | -- | 0.02 ± 0.09‡ | 0.08 ± 0.15‡ | −0.07 ± 0.09‡ | −0.17 ± 0.13‡ | −0.17 ± 0.10‡ | −0.44 ± 0.20‡ | |
| P‡ | -- | .7‡ | .6‡ | .2‡ | .2‡ | .2‡ | .09 | |
| Mean MPS† Anterior | Norm | 2.07 ± 0.10 | 2.31 ± 011 | 2.60 ± 0.13 | 2.50 ± 012 | 2.79 ± 0.14 | 2.66 ± 0.14 | 2.94 ± 0.16 |
| KC | 2.30 ± 0.20 | 2.56 ± 0.21 | 2.88 ± 0.24 | 2.77 ± 0.27 | 3.09 ± 0.30 | 2.99 ± 0.33 | 3.33 ± 0.40 | |
| P | .003 | .003 | .003 | .007 | .007 | .006 | .008 | |
| Highest MPS Anterior | Norm | 2.38 ± 0.23 | 2.53 ± 0.18 | 2.91 ± 0.15 | 2.71 ± 0.16 | 3.09 ± 0.16 | 2.85 ± 0.15 | 3.26 ± 0.18 |
| KC | 2.73 ± 0.37 | 2.83 ± 0.31 | 3.21 ± 0.32 | 3.00 ± 0.31 | 3.44 ± 0.37 | 3.22 ± 0.38 | 3.80 ± 0.70 | |
| P | .01 | .01 | .009 | .01 | .01 | .009 | .02 | |
| Mean MPS Posterior | Norm | 2.78 ± 0.18 | 2.83 ± 0.18 | 2.93 ± 0.18 | 2.90 ± 0.18 | 3.01 ± 0.18 | 3.01 ± 0.20 | 3.14 ± 0.19 |
| KC | 3.14 ± 0.38 | 3.21 ± 0.39 | 3.31 ± 0.40 | 3.29 ± 0.39 | 3.41 ± 0.40 | 3.44 ± 0.44 | 3.60 ± 0.51 | |
| P | .008 | .008 | .008 | .008 | .008 | .008 | .01 | |
| Highest MPS Posterior | Norm | 3.03 ± 0.37 | 3.05 ± 0.38 | 3.14 ± 0.38 | 3.09 ± 0.35 | 3.22 ± 0.33 | 3.20 ± 0.37 | 3.34 ± 0.35‡ |
| KC | 3.53 ± 0.55 | 3.55 ± 0.55 | 3.66 ± 0.61 | 3.59 ± 0.54 | 3.72 ± 0.66 | 3.75 ± 0.60 | 4.22 ± 1.48‡ | |
| P | .02 | .02 | .03 | .01 | .02 | .02 | .07‡ | |
| Overall Mean MPS | Norm | 2.25 ± 0.10 | 2.43 ± 0.11 | 2.66 ± 0.12 | 2.42 ± 0.11 | 2.59 ± 0.12 | 2.54 ± 0.12 | 2.72 ± 0.13 |
| KC | 2.48 ± 0.24 | 2.69 ± 0.25 | 2.94 ± 0.27 | 2.69 ± 0.25 | 2.88 ± 0.27 | 2.85 ± 0.29 | 3.06 ± 0.33 | |
| P | .008 | .006 | .004 | .004 | .004 | .005 | .006 | |
| Overall Highest MPS | Norm | 2.77 ± 0.23 | 2.84 ± 0.23 | 3.02 ± 0.22 | 4.21 ± 0.69‡ | 4.20 ± 0.69‡ | 4.47 ±0.65 | 4.47 ± 0.61 |
| KC | 3.16 ± 0.47 | 3.23 ± 0.47 | 3.43 ± 0.45 | 5.01 ± 1.30‡ | 5.05 ± 1.31‡ | 5.87 ± 1.61 | 5.81 ± 1.62 | |
| P | .02 | .02 | .02 | .08‡ | .07‡ | .02 | .02 |
µm = micrometers, D = Diopters, Norm = normal group, KC = keratoconus group, MPS = maximum principal strain, Mean = average value over analyzed region, Highest = highest value over analyzed region, Anterior = anterior surface of residual stromal bed with a 9mm analysis diameter, Posterior = posterior surface of corneal stroma with a 9mm analysis diameter, Overall = a 3-dimensional analysis zone with a depth encompassing the full thickness of the cornea and spanning the central 5mm diameter.
Strain values are dimensionless and are given as strain ×102 to provide a % strain. All values reported as mean ± standard deviation.
Indicate comparisons of normal and KC groups for which independent samples 2-sided heteroscedastic Student’s t tests yielded P values > 0.05 (not significant).