Repeatability of ocular wavefront measurement.

PURPOSE: To assess the repeatability of measurements of ocular aberrations using wavefront sensing in a small group of observers and to assess the potential effect of measurement error on custom corneal correction due to this variability. METHOD: A Shack-Hartmann wavefront sensor was used to measure the ocular wavefront in nine eyes. Head position was stabilized using a dental bite bar, and the pupil was centred using a cathode ray tube monitor and circular grating. Twenty Shack-Hartmann images were collected for each measurement. Each observer had three sets of measurements taken; the first and the second after careful alignment and the final after regrasping the bite bar in the same position as for the second measurement, but without pupil realignment. The modulation transfer functions for each set were calculated, and the effect of best-aligned custom treatments on the modulation transfer function was estimated. RESULTS: There were highly statistically significant differences in a large number of Zernike modes between the three sets of measurements. The modulation transfer functions calculated for the residual wavefronts after aligned custom treatment were below the diffraction limit. The root mean square wavefront errors were consistently better for the residual wavefronts obtained using the realigned data than using data taken without pupil realignment. CONCLUSIONS: Sequential measurement of ocular aberrations shows statistically significant differences in a large number of Zernike modes. If aberrations determined by a single measurement are to be used in a custom correction, the resulting modulation transfer function is likely to remain below the diffraction limit. Pupil realignment is critical in reduction of the residual root mean square wavefront values to a minimum.

Aberrations of the human eye in visible and near infrared illumination.

PURPOSE: In most current aberrometers, near infrared light is used to measure ocular aberrations, whereas in some applications, optical aberration data in the visible range are required. We compared optical aberration measurements using infrared (787 nm) and visible light (543 nm) in a heterogeneous group of subjects to assess whether aberrations are similar in both wavelengths and to estimate experimentally the ocular chromatic focus shift. METHODS: Ocular aberrations were measured in near infrared and visible light using two different laboratory-developed systems: laser ray tracing (LRT) and Shack-Hartmann. Measurements were conducted on 36 eyes (25 and 11 eyes, respectively), within a wide range of ages (20 to 71 years), refractive errors (-6.00 to +16.50), and optical quality (root mean square wavefront error, excluding defocus, from 0.40 to 9.89 microm). In both systems, wave aberrations were computed from the ray aberrations by modal fitting to a Zernike polynomial base (up to seventh order in laser ray tracing and sixth order in Shack-Hartmann). We compared the Zernike coefficients and the root mean square wavefront error corresponding to different terms between infrared and green illumination. RESULTS: A Student's t-test performed on the Zernike coefficients indicates that defocus was significantly different in all of the subjects but one. Average focus shift found between 787 nm and 543 nm was 0.72 D. A very small percentage of the remaining coefficients was found to be significantly different: 4.7% of the 825 coefficients (25 eyes with 33 terms) for laser ray tracing and 18.2% of the 275 coefficients (11 eyes with 25 terms) for Shack-Hartmann. Astigmatism was statistically different in 8.3% of the eyes, root mean square wavefront error for third-order aberrations in 16.6%, and spherical aberration (Z4(0)) in 11.1%. CONCLUSIONS: Aerial images captured using infrared and green light showed noticeable differences. Apart from defocus, this did not affect centroid computations because within the variability of the techniques, estimates of aberrations with infrared were equivalent to those measured with green. In normal eyes, the Longitudinal Chromatic Aberration of the Indiana Chromatic Eye Model can predict the defocus term changes measured experimentally, although the intersubject variability could not be neglected. The largest deviations from the prediction were found on an aphakic eye and on the oldest subject.

[Comorbidity of obesity and eating behavior disorders]. / Comorbilidad de la obesidad con los trastornos de la conducta alimentaria.

UNLABELLED: In the few years various factors that influence obesity have been studied, including genetic, sociocultural, metabolic and endocrine factors. Research advances in this area will help enhance our knowledge, prevention and treatment of this syndrome. OBJECTIVE: Our first aim is to establish comorbidity between obesity and eating disorders (i.e., binge eating disorder, compulsive overeating disorder and bulimia). Our second aim is to establish the relation between psychiatric diagnoses and sociodemographic, anthropometric, endocrine and psychological variables. METHOD: We interviewed 97 outpatients that attended a specialized clinic for obesity control in Mexico City, 67 females and 30 males. These patients were interviewed by a nutrition specialist, an endocrinologist and a psychiatrist, all working in the obesity clinic. For the psychiatric diagnoses, DSM-IV criteria were applied to analyze the clinical information on the charts. RESULTS: Of all patients in the group 13.4% presented no psychiatric disorder, 53.6% met criteria for binge eating disorder, 12.4% for type six NOS-ED (Not Otherwise Specified Eating Disorder) (compulsive overeating) and 20.6% for bulimia. Endocrine disorders were found as follows: 80.4% presented no endocrine disorder, 11.3% diabetes mellitus, and 8.2% other diagnoses. Obesity degree: 8.2% normal weight, 28.9% overweight, 37.1% type 1 obesity, 18.6% type II obesity and 7.2% extreme obesity; binge eating disorder was related to all obesity types. Bulimic patients had a greater energetic expenditure. Patients with psychiatric disorders generally did not present endocrine comorbidity, only 13.4% comorbidity. The number of treatments to reduce weight was in direct relationship to patients with psychiatric disorders. Patients with a largest calorie intake presented binge eating disorder with more eating periods per hay. In sum, by measuring anthropometric variables and some nutritional variables, such as the way of eating and calorie intake, it was easier to predict eating disorders in obese patients. The medical variables themselves were not associated to the mental health of obese patients. CONCLUSIONS: We found there is an important relation between obesity and psychiatric disorders and we consider it necessary to undertake further multidisciplinary, longitudinal and prospective studies in other groups of patients or non patients.