Spatio-chromatic vision with multifocal diffractive intraocular lens.

BACKGROUND: This study aims to detect alterations in the spatio-chromatic pseudophakic vision produced by multifocal diffractive intraocular lenses (IOLs) and provides a physical interpretation. METHODS: In vitro characterization of the imaging performance of two diffractive IOLs: AT LISA Tri (Zeiss) and FineVision (PhysIOL) in on-bench model eye illuminated with red (R, 625 nm), green (G, 530 nm) and blue (B, 455 nm) lights. We used the metrics: energy efficiency (EE), area under the modulation transfer function, longitudinal chromatic aberration (LCA), and halo intensity. Through-focus (TF) analysis and calculation of the expected defocus curve under white (W) daylight were included. In vivo visual acuity (VA) of 50 pseudophakics (60 eyes) was assessed under W, R, G, B lights at far and near. Two clinical experiments evaluated LCA and R, G, B TF-EE effects on pseudophakic vision and their relative importance. RESULTS: Clinical mean VA values under W light agreed with the predicted values at far and near for both IOLs. LCA measurements and R, G, B TF-EE curves were consistent with their lens design based on the 0th and 1st diffraction orders operative for far and near vision, respectively. LCA effects were compensated at near but noticed at far (- 0.75 D under B light). We detected strong asymmetry in visual resolution depending on the object distance and the illuminating wavelength-red predominance at far, blue predominance at near-in consistency with the TF-EE measurements. CONCLUSIONS: Diffractive multifocal IOL designs produce asymmetries in the spatio-chromatic vision of pseudophakics beyond the alterations strictly due to LCA. VA asymmetry for far/near object distance under R and B illumination is clinically detectable in subjects implanted with IOLs with 0th and 1st diffraction orders for far and near vision, respectively. Such VA asymmetry cannot be explained solely from the influence of defocus, as would be derived from a chromatic difference of power, but mainly from the wavelength dependence of the EE.

Novel approach to continuous adventitious respiratory sound analysis for the assessment of bronchodilator response.

BACKGROUND: A thorough analysis of continuous adventitious sounds (CAS) can provide distinct and complementary information about bronchodilator response (BDR), beyond that provided by spirometry. Nevertheless, previous approaches to CAS analysis were limited by certain methodology issues. The aim of this study is to propose a new integrated approach to CAS analysis that contributes to improving the assessment of BDR in clinical practice for asthma patients. METHODS: Respiratory sounds and flow were recorded in 25 subjects, including 7 asthma patients with positive BDR (BDR+), assessed by spirometry, 13 asthma patients with negative BDR (BDR-), and 5 controls. A total of 5149 acoustic components were characterized using the Hilbert spectrum, and used to train and validate a support vector machine classifier, which distinguished acoustic components corresponding to CAS from those corresponding to other sounds. Once the method was validated, BDR was assessed in all participants by CAS analysis, and compared to BDR assessed by spirometry. RESULTS: BDR+ patients had a homogenous high change in the number of CAS after bronchodilation, which agreed with the positive BDR by spirometry, indicating high reversibility of airway obstruction. Nevertheless, we also found an appreciable change in the number of CAS in many BDR- patients, revealing alterations in airway obstruction that were not detected by spirometry. We propose a categorization for the change in the number of CAS, which allowed us to stratify BDR- patients into three consistent groups. From the 13 BDR- patients, 6 had a high response, similar to BDR+ patients, 4 had a noteworthy medium response, and 1 had a low response. CONCLUSIONS: In this study, a new non-invasive and integrated approach to CAS analysis is proposed as a high-sensitive tool for assessing BDR in terms of acoustic parameters which, together with spirometry parameters, contribute to improving the stratification of BDR levels in patients with obstructive pulmonary diseases.

The role of vertical disparities in the oblique effect

A great deal of studies using different visual tasks (e.g., Vernier acuity tasks, tilt illusion, crowding, etc) have revealed that our perception is strongly influenced by the orientation of the stimulus. Most studies have investigated visual acuity in two-dimensional visual spaces (2D) but little is known about the effect of line orientation in depth perception (3D). In one experiment, Vernier Acuity (VA) in frontoparallel (2D) and medial (3D) planes was investigated. We used a virtual reality setup inducing inter-ocular disparities to simulate a 3D visual space, and a common computer screen to present stimuli in the frontal plane. In the experiment, by using the method of constant stimuli, the observer compared VA in the 2D and 3D visual spaces as a function of the stimulus orientation. Results showed that only judgments in the 3D condition were affected by the well-known 'oblique effect', and some impairment in stereoacuity (lines in depth plane) in comparison to 2D acuity (lines in frontal plane) was observed. We attributed the cause for such deterioration in stereoacuity to changes in vertical disparities.(AU)

The role of vertical disparities in the oblique effect

A great deal of studies using different visual tasks (e.g., Vernier acuity tasks, tilt illusion, crowding, etc) have revealed that our perception is strongly influenced by the orientation of the stimulus. Most studies have investigated visual acuity in two-dimensional visual spaces (2D) but little is known about the effect of line orientation in depth perception (3D). In one experiment, Vernier Acuity (VA) in frontoparallel (2D) and medial (3D) planes was investigated. We used a virtual reality setup inducing inter-ocular disparities to simulate a 3D visual space, and a common computer screen to present stimuli in the frontal plane. In the experiment, by using the method of constant stimuli, the observer compared VA in the 2D and 3D visual spaces as a function of the stimulus orientation. Results showed that only judgments in the 3D condition were affected by the well-known 'oblique effect', and some impairment in stereoacuity (lines in depth plane) in comparison to 2D acuity (lines in frontal plane) was observed. We attributed the cause for such deterioration in stereoacuity to changes in vertical disparities.