8
establish whether or not there is a statistically significant difference between the mean
keratometric values. A p value of less than 0.05 is considered to be statistically
significant.
Results
Of the 200 patients, 90 (45%) were males and 110 (55%) were females. The age
ranged from 21 to 56 years with an average of 34 years ± 8.2 years. Table 2 shows the
average values, standard deviation and the range of the pre- and post-Lasik data from the
two groups used in the study. Each group had 50 right eyes and 50 left eyes.
Figure 2 compares the Kc.rd values to the ones obtained by the history-derived
method (Kc.hd) in Group II. The correlation coefficient is 0.97 (P<0.001). The average
value of Kc.rd is 40.23 D +/-2.11 while the average value of Kc.hd is 40.23 D +/-2.17.
The difference between the two mean keratometric values is 0.001 D +/- 0.50 and is not
statistically significant (P>0.5). The 95% confidence interval around the mean difference
is (-0.10, +0.10).
Figure 3 compares Kc.cd to the ones obtained by the Kc.hd also in Group II. The
correlation coefficient is 0.96 (P<0.001). The average value of Kc.cd is 40.21 D +/-2.10
while the average value of Kc.hd is 40.23 D +/-2.17. The difference between the two
mean keratometric values is 0.02 D +/- 0.58 and is not statistically significant (P>0.5).
The 95% confidence interval around the mean difference is (-0.14, +0.10).
