OCULUS Pentacam Interpretation Manual page 133

17 Holladay Report & Holladay EKR65 Detail Report
The EKR65 values at the top center (Figure 159) are approximately 3.0 D flatter than average with
1.31 D of astigmatism. In the axial power map corneal power is steeper above than it is below by
around 1.0 D, which is not unusual. The broken semi-meridian lines show mild irregular astigmatism
which have been orthogonalized to the best least squares fit of 161.4° for the flat meridian and 71.4°
for the steep meridian axes for both the front and back surface. Since the irregular astigmatism
is mild and the magnitude of 1.31 D relatively low, this orientation is desired for a toric IOL. It
should be noted, however, that repeated measures and using the average magnitude and axis would
improve results even more. The tangential curvature map also illustrates the irregular astigmatism
component due to the broken semi meridian lines.
The Q-value over the 6.0 mm zone is 0.12, which is more positive than normal (-0.26), so more SA
is expected. Table 10 shows the normal values for the Q-value, eccentricity, total Zernike SA (μm)
at the corneal vertex and Seidel SA (D) at the retina plane. The total SA confirms the increased SA
with a value of 0.398 μm, which is much higher than the average of 0.27 μm. The total SA is the
value that should be used for the selection of an aspheric IOL for a specific patient [38]. The radii
ratio (back/front) is 80.3%, which is lower than the normal ratio. Although this cornea has not
had myopic refractive surgery (LASIK or PRK), the percentage gets lower the greater the amount
of the treatment. In this case the estimated K pre-refractive surgery is 42.1 D, and a refractive
change is -1.1 D. These are the values that would be used for the historical method from traditional
keratometry for comparison with the EKR65, when no historical information is available regarding
the refractive surgery. The pupil diameter is 5.48 mm and taken with low light levels, but depending
on the location of the device (illuminated room), the value is usually smaller than the scotopic pupil
size one obtains with infrared pupillometers that would in complete darkness. In this case, the value
is larger than 4.5 mm, so this zone would be appropriate for the EKR65 values for this patient. When
the patient's pupil is 3.0 or 4.0 mm, then going to the appropriate columns for the EKR65 valueis
recommended. The pachymetry min is 567 μm, which is thicker than average (555 μm). Note that
the QS shows "blinking" and should be repeated. The Scheimpflug images may be reviewed to see
how many were corrupted by the blink.
In the corneal thickness map the TP of the cornea (small black circle and optical center) is at the
centroid of the elliptical colour zones, as it should be. The pupillary center (black and white cross
hair) and apex (small white spot with black dot) are located temporally. Angle alpha is the angle
or distance between optical center and apex (visual axis), which has both a significant vertical and
horizontal component. Diffractive and refractive multifocal IOL perform best when located at the
pupillary center and visual axis. If these IOLs are to be used, the surgeon should note these locations
because the IOL will normally center in the bag at the optical center, rather than the pupil center
and visual axis. The IOL haptics will need to be "nudged" to achieve the optimal lens performance.
The RP is normal with a distribution that parallels the steep and flat meridians. The flatter meridian
usually has negative values (thinner) that are similar to the positive values (thicker) in the steeper
meridian. The elevation maps are normal, even with the lobulated pattern on the elevation (back),
since these values would result in thicker corneal pachymetry in these areas. Positive elevations on
the back surface are the most important values indicating the possibility of a thinning disorder.
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