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Jorge L Alió,
David P Piñero,
Alicia Alesón,
Miguel A Teus,
Rafael I Barraquer,
Joaquim Murta,
Miguel J Maldonado,
Gracia Castro de Luna, Ramón Gutiérrez,
César Villa,
Antonio Uceda-Montanes
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ABSTRACT: To evaluate the clinical features of keratoconus taking into consideration anterior corneal aberrations, internal astigmatism, and corneal biomechanical properties and to define a new grading system based on visual limitation.
Vissum Corporation, Alicante, Spain.
Retrospective case series.
This multicenter study comprised consecutive keratoconic eyes with no previous ocular surgery or active ocular disease. Visual, refractive, corneal topography, and pachymetry outcomes were analyzed. Internal astigmatism was calculated by vectorial analysis. Corneal aberrations and corneal biomechanics characterized by the Ocular Response Analyzer were evaluated in some eyes. Correlations between clinical data and a linear multiple regression analysis for characterizing the relationship between visual limitation and objective clinical data were performed.
This study comprised 776 eyes of 507 patients (age range 11 to 79 years) The mean keratometry (K) correlated significantly with logMAR corrected distance visual acuity (CDVA) (r = 0.591, P<.01), internal astigmatism (r = 0.497, P<.01), corneal asphericity (r = -0.647, P<.01), and several corneal higher-order aberrometric coefficients (r≥0.603, P<.01). Significant correlations were found between some corneal aberrometric parameters and CDVA (r≥0.444, P<.01). Multiple regression analysis showed that CDVA was significantly correlated with the mean K, intraocular pressure, corneal resistance factor, and spherical equivalent (r(2) = 0.69, P<.01). There were significant differences in mean K, internal astigmatism, and corneal higher-order aberrations between 4 groups differentiated by visual limitation (P<.01).
The visual limitation in keratoconus could be explained by different alterations that occur in these corneas and allowed development of a new grading system for this condition.
Journal of cataract and refractive surgery 03/2011; 37(3):552-68. · 2.75 Impact Factor
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ABSTRACT: We test visual performance after LASIK (laser in situ keratomileusis) for a Q-optimized ablation algorithm and one based on the Munnerlyn formula. The visual functions tested include aberrometry, monocular and binocular contrast sensitivity function (CSF), and a discrimination test under low-illumination conditions. This test is useful to quantify night-vision disturbances. A total of 102 patients took part in the experiments, and visual data were taken before (with best correction) and after LASIK. Results show a deterioration in aberrometry, CSF, binocular summation, and discrimination index for the two algorithms tested, although this deterioration is significantly lower for the Q-optimized algorithm.
Applied Optics 10/2009; 48(30):5741-7. · 1.41 Impact Factor
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ABSTRACT: To evaluate the changes in correlations of higher order aberrations of the first corneal surface with halo phenomena, a form of image degradation, under night vision conditions measured objectively after successful LASIK (laser in situ keratomileusis) surgery.
A prospective, observational, analytical study of 110 eyes that had undergone successful LASIK surgery for myopia and astigmatism. Preoperative sphere was (mean (SD)) -3.48 (1.70) D (0 to -8.00 D) and preoperative cylinder was -0.86 (0.87) D (0 to -4.00 D). Visual disturbance caused by halo phenomena was measured with the Starlights v1.0, and pupil size was measured with Colvard pupilometry after adaptation to a dark environment (0.17 lux). Corneal aberrations were computed for a corneal diameter representative of the eye's entrance pupil under night vision conditions.
The halo disturbance index increased in this study by a factor of 2.15 after successful LASIK surgery. Total root mean square for monochromatic higher order aberration displayed a significant correlation with halo disturbance index (r = 0.42; p<0.01). However, only secondary astigmatism (r = 0.36; p<0.01), coma (r = 0.25; p = 0.02) and spherical aberration (r = 0.40; p<0.01) were responsible for such behaviour, with the remaining corneal aberrations up to the sixth order not displaying any significant correlation when considered individually.
Patients undergoing LASIK procedures display an increase of halo phenomena around lights in night vision conditions, even when the results of the surgery are considered entirely satisfactory according to current international standards of predictability, efficacy and safety. Secondary astigmatism, coma and spherical aberration are the higher order aberrations up to the sixth order that significantly correlated with halo disturbance index.
British Journal of Ophthalmology 08/2007; 91(8):1031-7. · 2.90 Impact Factor
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ABSTRACT: To investigate if pre-surgical anisometropia influences the post-LASIK binocular mesopic contrast sensitivity function (CSF).
Pre- and post-surgical binocular CSF was measured for 54 patients under mesopic conditions. Data on visual acuity and corneal topography were also obtained.
The binocular contrast sensitivity declined significantly (r = 0.86; p < 0.001) with increasing pre-surgical anisometropia. Post-surgical interocular differences in corneal asphericity were also associated with increasing pre-surgical anisometropia.
Pre-surgical anisometropia may be indicative of a possible significant deterioration of post-surgical mesopic binocular CSF, and therefore should be taken into account before surgery in analysing the possible disadvantages and limitations of refractive surgery.
Ophthalmic and Physiological Optics 03/2007; 27(2):210-2. · 1.58 Impact Factor
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ABSTRACT: To analyze binocular visual function after LASIK.
Eye aberrometry and corneal topography was obtained for both eyes in 68 patients (136 eyes). To evaluate visual performance, monocular and binocular contrast sensitivity function and disturbance index for quantifying halos were measured. Tests were performed under mesopic conditions.
Binocular summation and disturbance index diminished significantly (P<.0001) after LASIK with increasing interocular differences in corneal and eye aberrations. Binocular visual deterioration was greater than monocular deterioration for contrast sensitivity function and disturbance index.
Binocular function deteriorates more than monocular function after LASIK. This deterioration increases as the interocular differences in aberrations and corneal shape increase. Improvements in ablation algorithms should minimize these interocular differences.
Journal of refractive surgery (Thorofare, N.J.: 1995) 10/2006; 22(7):679-88. · 2.54 Impact Factor
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ABSTRACT: We study the differences between real and expected corneal shapes, using an aspherical ablation algorithm with a known equation and avoiding the limitation imposed by most studies of refractive surgery in which the ablation equations are not known. We have calculated the theoretical corneal shape predicted by this algorithm, comparing this shape with the real corneal topography. The results indicate that the deviations that appear in the corneal shape are significant for visual performance and for the correction of eye aberrations. If we include in this analysis the effect of reflection losses and nonnormal incidence on the cornea, we can reduce corneal differences, but they will remain significant. These results confirm that it is essential to minimize corneal differences to achieve effective correction in refractive surgery.
Applied Optics 08/2005; 44(21):4528-32. · 1.41 Impact Factor
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ABSTRACT: We present a simple device (called a halometer) to detect and quantify the phenomenon of halos after certain surgical procedures, such as refractive surgery. The task of the subject consists basically of discriminating, after dark adaptation, a small light source around a central high-luminance stimulus. The device, which is connected to a computer, provides a disturbance index to measure the effect of halos on the observer's vision. Tested with normal subjects and patients after LASIK (laser in situ keratomileusis) surgery, this apparatus proved sufficiently sensitive to quantify the halos in subjects who had undergone surgery.
Journal of Biomedical Optics 11/2003; 8(4):663-7. · 3.16 Impact Factor
