Ángel Ramón Gutiérrez

Peripheral refraction in myopic patients after Orthokeratology

Purpose. The purpose of this study was to characterize the central and peripheral refraction across the horizontal meridian of the visual field before and after myopic corneal refractive therapy (CRT) with contact lenses. Methods. Twenty-eight right eyes from 28 subjects (mean age ± SD = 24.6 ± 6.3 years) were fitted with Paragon CRT contact lenses to treat myopia between −0.88 and −5.25 D of spherical equivalent. Along with a complete set of examination procedures to assess suitability for treatment, the central and peripheral refractions were measured along the horizontal meridian up to 35° of eccentricity in the nasal and temporal retinal area in 5° steps. Results. Baseline central average spherical equivalent (M) measured by subjective refraction changed from −1.95 ± 1.27 D to −0.38 ± 0.67 D. Changes in M component ranged between 1.42 ± 0.89 D at center and 0.43 ± 0.88 D at 20° in the temporal retina (p < 0.002). At 25° to both sides of the central refraction measurement, peripheral refraction after treatment was not statistically different from baseline values (p > 0.351). Beyond the 25° limit, M component changed in the myopic direction up to −1.11 ± 0.88 D at 35° in temporal retina (p < 0.001). Treatment induced was symmetric between nasal and temporal visual field along the horizontal meridian (p > 0.05 for all eccentricities). Furthermore, the degree of myopic increase in spherical equivalent for 30° (r2 = 0.573, p < 0.001) and 35° (r2 = 0.645, p < 0.001) eccentric refraction was highly correlated with axial spherical equivalent at baseline. Conclusions. CRT inverts the pattern of peripheral refraction in spherical equivalent refraction, creating a treatment area of myopic reduction within the central 25° of visual field, and a myopic shift beyond the 25°. In peripheral refraction for 30° and 35°, the amount of myopia induced in terms of spherical equivalent has an almost 1:1 relationship with the amount of baseline spherical equivalent refraction to be corrected.

Effect of Pupil Size on Corneal Aberrations Before and After Standard Laser In Situ Keratomileusis, Custom Laser In Situ Keratomileusis, and Corneal Refractive Therapy

PURPOSE To evaluate the effect of changing the pupil size on the corneal first-surface higher-order aberrations induced by different refractive treatments: standard laser in situ keratomileusis (LASIK), custom LASIK, and corneal refractive therapy. DESIGN Observational study. METHODS Eighty-one right eyes from patients with a mean age of 29.94 +/- 7.5 years, of which 50 were female (61.7%), were analyzed retrospectively at the Clínica Oftalmológica NovoVision, Madrid, Spain. Corneal videokeratographic data were used to obtain corneal first-surface higher-order aberrations for aperture diameters from 3 to 8 mm using the Vol-CT software (Sarver & Associates, Inc). Total root mean square (RMS) and RMS for third- to sixth-order Zernike polynomials as well as spherical-like, coma-like, secondary astigmatism, and spherical plus coma-like variables were calculated. RESULTS We verified an increase in the higher-order aberration total RMS after treatments of 0.014 +/- 0.025 microm, 0.019 +/- 0.027 microm, and 0.018 +/- 0.031 microm for standard LASIK, custom LASIK, and corneal refractive therapy, respectively, for 3-mm pupil diameter. For the 8-mm aperture diameter, changes in total RMS increased by a factor of 50 compared with the variation for the 3-mm diameter up to 0.744 +/- 0.731 microm, 0.493 +/- 0.794 microm, and 0.973 +/- 1.055 microm for standard LASIK, custom LASIK, and corneal refractive therapy, respectively. CONCLUSIONS The 3 techniques increase the wavefront aberrations of the cornea and change the relative contribution of coma-like and spherical-like aberrations. For a large aperture (> 5 mm), corneal refractive therapy induces more spherical-like aberrations than standard and custom LASIK. However, no clinically or statistically significant differences existed for narrower apertures. Standard and custom LASIK did not display statistically significant differences regarding higher-order aberrations.

Local steepening in peripheral corneal curvature after corneal refractive therapy and LASIK.

Purpose. The purpose of this study was to assess the changes in curvature along the horizontal meridian of the anterior cornea occurring after refractive surgery and corneal refractive therapy (CRT). Methods. One hundred twenty-two eyes of 122 patients (70 female) with a mean (SD) age of 30.6 ± 7.5 years were retrospectively analyzed in this study. Forty-three of those underwent standard laser in situ keratomileusis (LASIK) ablation, 40 had customized LASIK and 39 had CRT with orthokeratology lenses. Patients in different groups were matched to be comparable in terms of pretreatment refractive error and corneal topographic profiles. Topographical data along the horizontal meridian were collected over a 10 mm corneal diameter in 1 mm steps using the tangential power map from the computer display. Results. A statistically significant increase in corneal power (p < 0.05) was observed at the nasal and temporal locations between 2 and 3 mm for CRT and 3 and 4 mm for LASIK procedures, from corneal keratometric center. This steepening was more pronounced after CRT treatment (p < 0.05 for all comparisons against LASIK groups) but not significantly different between LASIK groups (p > 0.124, Mann-Whitney Test). Conclusions. Both, surgical and non-surgical interventions show a mid-peripheral local corneal steepening. However, the narrower optic zone and higher midperipheral steepening with CRT seems to provide the potential to create a more relative peripheralmyopic increase in corneal power than LASIK, which may have implications in slowing down myopia progression.

Quality of life of myopic subjects with different methods of visual correction using the NEI RQL-42 questionnaire

Purpose To evaluate different aspects of the visual-related quality of life using the National Eye Institute Refractive Error Quality of Life (NEI RQL)-42 questionnaire in low and moderate myopic subjects corrected with different refractive treatments including laser-assisted in situ keratomileusis (LASIK), orthokeratology (OK), soft contact lenses (SCLs), and spectacles. Methods The NEI RQL-42 questionnaire was administered to 217 subjects at one single clinic. All the questions consisted of 13 different subscales that were analyzed separately. The results from subjects with −1.00 to −3.00 diopter myopia corrected with LASIK (n=41), OK (n=37), SCLs (n=44), or spectacles (n=45) were compared with each other and with emmetropic subjects (n=50). Results Statistically significant differences among all groups were found in all subscales, except for satisfaction with correction (P=0.135). The average decrease in quality of life compared with emmetropes were −7.1% (P=0.021) for LASIK, −13.0% (P<0.001) for OK, −15.8% (P<0.001) for spectacles, and −17.3% (P<0.001) for SCLs. Conclusions Although all patients in each group were considered to be successfully visually corrected, quality of life related to vision was markedly different in certain NEI RQL-42 categories. LASIK showed the lowest average decrease in quality of vision compared with emmetropes. OK was comparable with LASIK in independence of visual correction, and SCL wear was superior to LASIK and OK lens wear in glare. Except for glare and diurnal fluctuations, contact lenses (SCL and OK) were comparable with or superior to spectacle correction.

Anterior and posterior corneal elevation after orthokeratology and standard and customized LASIK surgery

Purpose: To quantify the changes in the elevation topography of the front and back corneal surfaces after three different refractive treatments for correcting myopia with standard and custom laser in situ keratomileusis (LASIK) and orthokeratology using corneal refractive therapy. Methods: We evaluated 20 eyes undergoing orthokeratology for correction of myopia spherical equivalent (mean±SD=−3.41±0.76 D), 18 eyes undergoing custom LASIK surgery (mean±SD=−4.14±0.89 D), and 23 eyes undergoing standard LASIK (mean±SD=−3.61±0.67 D). The values of front and back corneal surfaces were derived by using Pentacam (Oculus, Inc. GmbH, Wetzlar, Germany) before and at least 3 months after each treatment, in the center of the cornea and 4 points to each side of the horizontal meridian at intervals of 1 mm. Results: Corneal elevation data before treatment were not statistically different between patients in either group (P>0.070, for back and front elevation). After treatment, both surgical procedures significantly increased the positive value of the front elevation beyond an area of 6 mm. The opposite trend was found within the central 5 mm of the cornea, presenting a statistically significant decrease in elevation (P<0.001). In the case of orthokeratology, the elevation experienced a minor but a statistically significant reduction in the central region (P<0.001). On the back surface, the elevation did not undergo statistically significant alterations in any of the procedures and none of the items discussed (P>0.285). Conclusions: Differences in front corneal elevation changes between LASIK and orthokeratology reveal a much different mechanism for producing corneal power subtraction. The back corneal surface does not suffer significant changes after surgical and nonsurgical treatments for the correction of myopia.

Repeatability of the Modified Thorington Card Used to Measure Far Heterophoria

Purpose To determine the interexaminer and intraexaminer repeatability of the modified Thorington test (TH) for distance vision in young adults and to compare these results with those observed for the heterophoria tests most commonly used in clinical practice. Agreement among tests was also assessed. Methods Distance heterophoria was quantified on two separate occasions by two examiners in 110 subjects aged 18 to 32 years (mean, 19.74 years; SD, 2.5 years) using four different tests: cover test (CT) Von Graefe, Maddox rod, and modified TH. The repeatability of the tests and agreement between them was estimated by the Bland and Altman method whereby the mean difference and the 95% limits of agreement were determined as the coefficient of repeatability (COR) and coefficient of agreement. Results The Thorington test showed best interexaminer repeatability (COR = ±1.43&Dgr;), followed closely by CT (COR = ±1.65&Dgr;), whereas best intraexaminer repeatability was observed for CT (COR = ±1.28&Dgr;) followed by TH (COR = ±1.51&Dgr;). Among the different combinations of tests, TH and CT showed best agreement indicated by the lowest coefficient of agreement (±2.23&Dgr;) and a low mean difference (−0.63&Dgr;) between measurements. Conclusions Good interexaminer and intraexaminer repeatability was observed for both TH and CT, and agreement between the two tests was also good. Given the simple administration of the TH, we recommend its clinical use to quantify distance horizontal heterophoria.

Peripheral Refraction in Myopic Eyes After LASIK Surgery

Purpose. To characterize the axial and off-axis refraction across the horizontal meridian of the visual field before and after myopic laser-assisted in situ keratomileusis (LASIK) surgery. This research took place at the Clinical Ophthalmologic-NovoVisión, Madrid, Spain. Methods. Twenty-six ODs (mean age ± SD = 30.4 ± 4.8 years) of 26 patients who underwent LASIK surgery to treat myopia between −0.75/−3.88 D of spherical equivalent (M) were included in the study. Peripheral refraction was evaluated by an open field auto-refractor before and after LASIK surgery at 3 months. Along with a complete set of examination procedures to assess suitability for treatment, the central and peripheral refractions were measured along the horizontal meridian up to 35° of eccentricity in the nasal and temporal retinal areas in 5° visual field steps. Results. Changes in M ranged between 1.85 ± 0.93 D at center to 0.33 ± 0.73 D at 35° in the nasal retina (p < 0.029 for all eccentricities). Treatment induced was symmetric between nasal and temporal visual fields along the horizontal meridian. The degree of myopic increase in relative peripheral refractive error as represented by the spherical equivalent for 30° (r2 = 0.462, p < 0.001) and 35° (r2 = 0.717, p < 0.001) eccentric refraction was correlated with axial spherical equivalent at baseline. Conclusions. Peripheral refraction is affected by myopic LASIK surgery. Unlike orthokeratology, which increases the peripheral myopia, LASIK reduces myopia across the horizontal visual field out to at least 35° from fixation.

Relative peripheral refraction across 4 meridians after orthokeratology and LASIK surgery

BackgroundTo characterize the axial and off-axis refraction across four meridians of the retina in myopic eyes before and after Orthokeratology (OK) and LASIK surgery.MethodsSixty right eyes with a spherical equivalent (M) between − 0.75 to − 5.25 D (cylinder <− 1.00 D) underwent LASIK (n = 26) or OK (n = 34) to treat myopia. Axial and off-axis refraction were measured with an open-field autorefractometer before and after stabilized treatments. Off-axis measurements were obtained for the horizontal (35° nasal and temporal retina) and vertical (15° superior and inferior retina) meridians, and for two oblique directions (45–225° and 135–315°) up to 20° of eccentricity. The refractive profile was addressed as relative peripheral refractive error (RPRE).ResultsOK and LASIK post-treatment results showed an increase of myopic relative refraction at several eccentric locations. At the four meridians evaluated, the M component of the pre-treatment RPRE values was not statistically different (p > 0.05) from the post-treatment RPRE within 30° and 20° of the central visual field after LASIK and OK, respectively. These results demonstrated that the treatment zone warrants an optimal central field of vision.ConclusionsThe present study gives an overview of RPRE after refractive corneal reshaping treatments (OK and LASIK) across vertical, horizontal and two oblique meridians together. This allows a 3D representation of RPRE at the retina and shows that the myopic shift induced by both treatments is more relevant in horizontal directions.