Post-graduate theses
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| Title |
H επίδραση των Οφθαλμικών Εκτροπών Υψηλής Τάξης στην Κλινική Διάθλαση |
| Alternative Title |
The impact of Ocular High Order Aberrations on Clinical Refraction |
| Creator |
Tsiklis, Nikolaos
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| Abstract |
Purpose:To study the impact of high order ocular aberrations, pupil size and accommodation state on accuracy and precision of the refractive error. Methods: Forty-five healthy myopic patients (81 eyes) with Sphere up to 10.00 D and Cylinder up to 2.50 D participated in this prospective study. After the evaluation of Uncorrected Visual Acuity (UVA), manifest refraction, Best Spectacle Corrected Visual Acuity (BSCVA) and pupil size, one drop of phenylephrine 2,5% was instilled. A series of thirty measurements at a steady-state accommodation was carried out using a Wavefront aberrometer COAS (Complete Ophthalmic Analysis System), which served as basis for objective phenylephrine refraction. Immediately afterwards, two drops of cyclopentolate 0.5% with 5 minutes interval were applied, and 30 later measurements of UVA, subjective cycloplegic refraction, BSCVA and pupil size took place. Moreover, 30 more measurements were acquired using the wavefront aberrometer, which were used for calculation of objective cyclopentolate wavefront refraction. Aberrations measurements up to 4th order were calculated for pupil size of 6 mm. Wavefront aberrations were expressed in 15 Zernike coefficients (OSA Notation) and paraxial curvature matching method (Taylor series) was used in order to calculate objective wavefront spherical equivalent taking in account the 2nd and 2nd+4th ocular aberrations. Results: Cycloplegia resulted in a hyperopic shift. Subjective cycloplegic spherical equivalent and sphere changed by a mean of +0.24 D (less myopic) compared with subjective manifest measurements. Moreover BSCVA decreased from 1.03 +/- 0.10 to 0.97 +/- 0.09 [(p<0.001) paired t-test]. The mean objective phenylephrine spherical equivalent was -0.245 D (2nd order) and -0.045 D (2nd+4th order) less myopic than the subjective measurements. After cycloplegia, the corresponding differences were -0.39 D (2nd order) and -0.18 D (2nd+4th order). The mean differences in all cases were statistical significant (vector analysis). The objective phenylephrine refractive error (2nd+4th order) was more accurate and more precise than the other objective measurements (mean 0.05 +/- 0.47 D, median 0.10 D, skewness 0.69, kurtosis 0.43). Cycloplegia did not increase the precision of the aberrometer measurements. Conclusions: Cycloplegia induces a hyperopic shift (about 0.25 D) in refractive error (objective and subjective measurements) and a statistical significant decrease in BSCVA. This is mainly due to small level of accommodation and not to the magnitude of spherical aberration. The inclusion of the 4th order aberrations increases the accuracy and the precision of the aberrometer measurements. The objective phenylephrine refraction (2nd+4th order) is more accurate and more precise than other objective measurements.
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| Language |
Greek |
| Issue date |
2006-03-0 |
| Date available |
2006-11-23 |
| Collection
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School/Department--School of Medicine--Department of Medicine--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/d/f/c/metadata-dlib-2006tsiklis.tkl
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| Views |
210 |
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