OBJECTIVE: To present a new method of dynamic Purkinje-metry and to verify it by comparison with a commercially available anterior segment optical coherence tomography CASIA2.
METHODS: A dynamic Purkinje-meter with a movable fixation target was assembled. A coaxial circular pattern formed by infrared LEDs was projected onto the eye and evoked Purkinje images (1st, 3rd, 4th = P1, P3, P4). The measurement was performed on 29 eyes with an implanted toric IOL (intraocular lens), under mydriatic conditions, with reference to the visual axis. The IOL tilt was calculated from the position of a fixation target at the moment of P3 and P4 superposition. The IOL decentration was determined based on the relative position of P1 during on-axis fixation and of P3 and P4 superposition during off-axis fixation. A custom-developed software was used for distance measurements. Using CASIA2, the IOL position was fully calculated by the device.
RESULTS: The mean absolute difference between CASIA2 and Purkinje-meter values was 0.6° ± 0.4° for the tilt magnitude and 10° ± 10° for the tilt direction, and 0.11 mm ± 0.08 mm for the decentration magnitude and 16° ± 14° for the decentration direction. There was no statistically significant difference between the values determined by the two methods for the tilt and decentration direction. The differences were statistically significant for the tilt and decentration magnitude.
CONCLUSIONS: The values of IOL tilt and decentration direction are similar for both devices. The values of IOL tilt and decentration magnitude measured by Purkinje-meter are higher than those from CASIA2, but overall, they correspond to the values presented in other published studies.

Research has shown that longitudinal chromatic aberration (LCA) of the human eye is generated across all of the eye\'s optical surfaces. However, it may not be necessary to measure the LCA from the first surface of the cornea to the retina, as it is known that most of the changes that can modify the path of light occur from the first surface of the cornea to the last surface of the crystalline lens. This investigation presents the study of an objective technique that allows the measurement of longitudinal chromatic aberration (LCA) on the last crystalline lens surface by developing a pulse width wavefront system using a Hartmann test, Purkinje image, and Zernike polynomial. A blue pulse (440-480 nm) and a red pulse (580-640 nm) were used to generate a pattern of spots in the human eye. This pattern generated on the posterior surface of the crystalline lens of the human eye allows the reconstruction of the wavefront via a modal method with Zernike polynomials. Once the wavefront is reconstructed, Zernike coefficients can be used to quantify the LCA. The methodology and objective measurements of the magnitude of the longitudinal chromatic aberration of five test subjects are explained in this article.

OBJECTIVE: Quality of vision in patients who have undergone corneal refractive surgery depends upon the optimal centration of the procedures used. The center of the pupil is used as a reference point in some corneal ablation procedures. The achromatic axis would be a more sensible option from an optical point of view, but it is not as readily detectable. As an alternative, other refractive techniques, like the small aperture corneal inlay for presbyopia correction, use the corneal reflex (first Purkinje image). To assess the relative position of these two marks, we developed a new instrument to simultaneously measure both the first Purkinje image (PI) and the intersection of the achromatic axis with the pupil plane.
METHODS: The apparatus records images of the pupil and the PI when illuminated with a circle of infrared light-emitting diodes. A second optical path allows determination of the achromatic axis by using a subjective method. Both the positions of the PI and the achromatic axis intersection are determined simultaneously.
RESULTS: A series of data were obtained in 48 eyes. The mean location of the achromatic point relative to the PI was [x = -0.05 ± 0.15 mm; y = 0.09 ± 0.18 mm]. Considered individually, in 55% of eyes, the distance between locations is less than 0.2 mm, and in 95% of eyes, distances are less than 0.4 mm.
CONCLUSIONS: On average, achromatic axis crossing of the pupil and PI locations coincides within measurement errors. Although there was some intersubject variability, differences in location were less than 0.6 mm in all measured eyes.