| Abstract |
Purpose
New optical technologies can detect ocular aberrations beyond defocus and
astigmatism. Ocular aberrations can be measured in several ways, including the use of
aberrometer. In theory, correction of HOAs beyond simple sphere and cylinder
increases retinal image resolution and contrast which in turn allows patients to see the
world with finer and higher contrast. HOAs are usually of much smaller magnitude
than low order aberrations. Successful HOA correction through customized lazer
refractive surgery, contact lenses or intraocular lenses relies on an accurate
measurement of HOA. However, a comparison of the HOA measurements among
different aberrometers and the knowledge of the measurement agreements with the
use of aberrometers has always been an important field of research offering the
opportunity for better and more useful ophthalmological information. Purposes of this
study are a) the evaluation of agreement of low and high order aberrations using the
aberrometers Wasca Coas, Wave Analyzer and iTrace and b) the assessment of the
agreement of the sphere measurements with the three aberrometers and with the
cycloplegic refraction with phoropter.
Methods
In the study took part 62 participants. The average age of the 62 participants was 28
years old (from 18 to 58 years old). All the participants were examined by the same
person. Initially, cyclogyl collyrium was placed upon the eye in order to create
mydriasis and cycloplegia. Twenty minutes after the infusion of the cyclogyl in order
to dilate the pupil 7mm, an examination of the sphere and the cylinder was conducted
with the use of a phoropter. The average value of the sphere and the cylinder were 5D
(from -10,25 to +2,5 D) and -0,5D (from 0 to -2,25) respectively. Promptly after that
the operator was ready to evaluate the low and high order aberrations in the central
optical zone of 6mm. The evaluation of the low and high order aberrations was
conducted with the use of Wasca Coas(1), Wave Analyzer(2) and iTrace(3)
aberrometers. The RMS for the 2nd to 6th order of aberrations, of the total aberrations
and the high order aberrations was measured as well. For the comparison of the
aberrations measured with the three devices as named above the statistical methods of
Bland and Altman were employed per two devices. Finally, the repeatability of the
measurement results for each of the three devices was checked in a specimen of 10
people. Five measurements took place for each eye with each of the three devices.
Results
From the comparisons of the devices 1-2 and 2-3 it was concluded that they present
adequate agreement not only on the 2nd order aberrations but for the total aberrations
as well. Regarding the 2nd order aberrations an agreement of larger scale is noticed in
the devices 2-3 with a 40,5% of disagreement, then comes the agreement of 1-2
devices with 43,3% of disagreement and last comes the agreement of 1-3 devices with
61,3% of disagreement. Similar results were noticed in the field of total aberrations.
Generally the comparison of the devices measurements for the high order aberrations
demonstrates a very bad percentage of agreement, with percentages of disagreement
above 100%. For the comparison of spheres we noticed that the sphere comparison
among the devices 2-4 and 1-4 demonstrate the smallest percentage of agreement,
44% and 49% respectively. The largest scale disagreement can be found in the
comparison of 1-3 devices with 108% percentage of disagreement. Finally, Wasca
demonstrates more accurate repeatability than the Wave Analyzer and the iTrace.
Conclusions
Important disagreements in the measurements with the three devices are highlighted
regarding the high order aberrations. On the contrary, regarding the 2nd order
aberrations and the total aberrations we noticed a large scale agreement among the
three devices. Wave Analyzer and Wasca Coas demonstrate the largest scale sphere
agreement with the cyclo sphere refraction. In the end, the repeatability regarding the
2nd order aberrations and the total aberrations is good, while in general the
repeatability of the 3rd to the 6th order of aberrations is considered to be bad.
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Σύγκριση μεταξύ τριών εκτροπόμετρων ανάλυσης μετώπου κύματος με διαφορετικές αρχές λειτουργίας
