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УДК 617.726 (048.8)
Киевская городская клиническая офтальмологическая больница "Центр микрохирургии глаза"
Kyiv City Clinical Eye Hospital "Eye Microsurgery Center"
One of the most important factor in successful correction of visual disorders is information about eye aberration status. Discovering eye optical system requires analysis of many units, and components affecting the aberration of the optical system [1, 2, 3]. These include, in particular, the deviation of the optical beam axis. Often, incoming rays do not cross the reference axis. This fact is not new, but it has not established yet which of the errors of the optical system is responsible for it.  For measurements of such deviations serves ray tracing aberrometer, but the math and the relationship calculating of radial deflection of the beam to the tangential so far not been investigated by anyone. For this purpose, a new soft “Vector Aberration” was developed by professor V.V.Molebny and G.A.Pavlovich in National Technical University of Ukraine "Kiev Polytechnic Institute" . The main advantage of this program is a new approach to the calculation of the standard deviation (SD) of the wave front produced by scanning. This software splits RMS of wave front into radial and tangential components. Then calculate their ratio, thereby calculating how many moves the beam in three dimensions from the plane of its entry into the optical system and on its "settlement" of intersection with the reference axis. Additional features of the program includes the ability to display data in a 3D format and transfer them to the program of statistical processing.
Aim. Comparison of the results of aberrometry assessment of the human eye optical system of volunteers and patients after cataract surgery with different types IOLs implantations.
Materials and methods. To meet the goal in the study we analyzed the aberrometry charts of healthy volunteers and patients after phacoemulsification performed with intraocular lens implantation. All participants are divided into four groups. First - healthy volunteers - 98 people (196 eyes). Second - patients after phacoemulsification with implantation of spherical IOL (SN60AT, SA60AT, MA60AT) – 65 people (65 eyes). The third - patients after phacoemulsification with implantation of aspherical IOL (SN60WF) - 55 people (55 eyes). Fourth - patients with multifocal IOL (SN6AD1, SN60D3, SN60D4) - 30 people (30 eyes). All surgeries and follow up were carried out in Kiev State Ophthalmology Hospital "Eye Microsurgery Center". All eyes met the following criteria: transparent refracting surfaces, visual acuity of 0.9 or higher, the lack of concomitant ocular pathology, adequate function of the pupil. For patients in 2nd, 3rd, and 4th groups, we use the data obtained in 3 month after surgery. Furthermore in these patients there were no surgical protocol violations, errors in calculating the IOL. There were no clinically significant events during postoperative period. Aberrometry performed on ray tracing aberrometer TRACEY VFA. Scan area was 5mm. Medical mydriasis was not used. Wave front RMS data was processed by “Vector Aberrations” program. It must be emphasized that we analyzed only the third and fourth order aberrations. On (Fig.1) it is shown the aberration "mask" where the correspondent boxes are ticked.
Fig.1 Aberration "mask" in “Vector Aberrations” soft
This approach is designed to eliminate the effect of the lower-order aberrations on the final result of analysis. As to the influence of other higher-order aberrations, the quadrupeds, that the higher degree of the polynomial, the smaller contribution to the quality of the optical system makes aberration 
Results. Figure 2 shows a map of the RMS wave front splitting in the 1st patients group.
Figure 2. The ratio of the radial component of wave front RMS to the tangential (skew) - the 1st group.
These histograms illustrates a slight deflection of a ray tracing optical system, which ultimately causes high visual acuity. The ratio of the radial component to tangential (both calculated in microns) is equal to 2.11.
The following diagram (Figure 3) shows a map of the RMS wave front splitting in the 2nd patients group.
Figure 3 The ratio of the radial component of wave front RMS to the tangential (skew) - the 2nd group.
These data suggests a significant rays deviation during passing modified (spherical IOL implanted) optical system of the eye, which proves the deterioration of the optical system under the influence of aberration in comparison with optical systems of the first group of volunteers. The ratio of the radial component to tangential (both calculated in microns) is equal to 2.27.
Figure 4 shows a histogram of the 3rd patients group.
Fig. 4. The ratio of the radial component of wave front RMS to the tangential (skew) - the 3rd group.
Numerical equivalent ratio of radial component to tangential is 2.21. This value is slightly smaller, and consequently, the optical system is better in comparison with that of the second group of patients, but significantly worse intact optical system of the first group of volunteers. This fact, in our opinion, is linked with a reduction of spherical aberration of the system due to the implantation of aspheric IOLs.
Figure 5 is describing the results of the wave front RMS transformation into radial and tangential components in 4th patients group, using “Vector Aberrations” soft. It is proved that the ReSTOR IOL implantation does not change the value of higher-order aberrations wherther patient looks to far or near distans . Therefore, for the 4th patients group we used the far distance data of aberrometry, a distance of not less than 5m.
Figure 5. The ratio of the radial component of wave front RMS to the tangential (skew) - the 4th group.
The ratio of the radial component to tangential (both calculated in microns) is equal to 2.56. The worst result is probably related to the structure of the ReSTOR IOL. Large scanning area - 5mm - causes significant ray deviations in the human eye optical system.
Conclusions. Analysis of the human eye optical system in volunteers without ophthalmic diseases, as well as patients undergoing phacoemulsification with implantation of different types of IOLs, using the “Vector Aberrations” software showed that:
1. Introduction of artificial optical component (IOL) in human eye do greatly reduces the quality of eye optical system.
2. In case of implantation of aspheric IOL, there is some decrease of fourth-order aberrations, which positively affects the quality of the optical system (in this study).
3. “Vector Aberrations” is a new approach to understanding the genesis of higher-order aberrations. Developed program gives an opportunity to understand the influence of higher-order aberrations to visual acuity.
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