Dolores de Fez

Computation and visualization of the MacAdam limits for any lightness, hue angle, and light source

We present a systematic algorithm capable of searching for optimal colors for any lightness L* (between 0 and 100), any illuminant (D65, F2, F7, F11, etc.), and any light source reported by CIE. Color solids are graphed in some color spaces (CIELAB, SVF, DIN99d, and CIECAM02) by horizontal (constant lightness) and transversal (constant hue angle) sections. Color solids plotted in DIN99d and CIECAM02 color spaces look more spherical or homogeneous than the ones plotted in CIELAB and SVF color spaces. Depending on the spectrum of the light source or illuminant, the shape of its color solid and its content (variety of distinguishable colors, with or without color correspondence) change drastically, particularly with sources whose spectrum is discontinuous and/or very peaked, with correlated color temperature lower than 5500 K. This could be used to propose an absolute colorimetric quality index for light sources comparing the volumes of their gamuts, in a uniform color space.

Reliability in perimetric multichannel contrast sensitivity measurements.

In this study, the reliability of perimetric contrast sensitivity measurements favouring the achromatic, the red‐green and the blue‐yellow post‐receptorial mechanisms was analysed.The ATD multichannel perimeter was built thanks to the support of the Spanish Ministerio de Ciencia y Tecnologia Grants DPI2000-0116-P4-02 and PTR 1995-0909-OP, in collaboration with INDUSTRIAS DE OPTICA SA (San Cugat del Valles, Spain).

Visual function alterations in essential tremor: A case report

Our purpose is to report alterations in contrast sensitivity function (CSF) and in the magno, parvo and koniocellular visual pathways by means of a multichannel perimeter in case of an essential tremor (ET). A complete evaluation of the visual function was performed in a 69-year old patient, including the analysis of the chromatic discrimination by the Fansworth–Munsell 100 hue test, the measurement of the CSF by the CSV-1000E test, and the detection of potential alteration patterns in the magno, parvo and koniocellular visual pathways by means of a multichannel perimeter. Visual acuity and intraocular pressure (IOP) were within the ranges of normality in both eyes. No abnormalities were detected in the fundoscopic examination and in the optical coherence tomography (OCT) exam. The results of the color vision examination were also within the ranges of normality. A significant decrease in the achromatic CSFs for right eye (RE) and left eye (LE) was detected for all spatial frequencies. The statistical global values provided by the multichannel perimeter confirms that there were significant absolute sensitivity losses compared to the normal pattern in RE. In the LE, only a statistically significant decrease in sensitivity was detected for the blue-yellow (BY) channel. The pattern standard deviation (PSD) values obtained in our patient indicated that there were significant localized losses compared to the normality pattern in the achromatic channel of the RE and in the red-green (RG) channel of the LE. Some color vision alterations may be present in ET that cannot be detected with conventional color vision tests, such as the FM 100 Hue.

Corneal Topographic and Aberrometric Measurements Obtained with a Multidiagnostic Device in Healthy Eyes: Intrasession Repeatability

Purpose. To evaluate the intrasession repeatability of corneal curvature, eccentricity, and aberrometric measurements obtained with a multidiagnostic device in healthy eyes. Methods. This study enrolled 107 eyes of 107 patients ranging in age from 23 to 65 years. All of them underwent a complete anterior segment examination with the VX120 system (Visionix-Luneau Technologies, Chartres, France). Three consecutive measurements were obtained. The within-subject standard deviation (Sw), intrasubject precision (1.96 × Sw), and intraclass correlation coefficient (ICC) were calculated. Results. All Sw for corneal power measurements were below 0.26 D, with ICC above 0.982. The Sw for corneal astigmatism at different areas (3, 5, and 7 mm) was below 0.21 D, with ICC above 0.913. Concerning the axis of astigmatism, its Sw was below 11.27°, with ICC above 0.975. The Sw and ICC for corneal eccentricity were 0.067 and 0.957, respectively. The Sw and ICC for high-order aberration root mean square (RMS) were 0.048 µm and 0.901, respectively. For 3rd- and 4th-order aberrometric parameters, all Sw were below 0.037 µm and all ICC were higher than 0.84, except for quadrafoil RMS (ICC: 0.689). Conclusions. The multidiagnostic device evaluated is able to provide consistent measurements of corneal power, eccentricity, and third- and fourth-order aberrations in healthy eyes.

In Vitro Aberrometric Assessment of a Multifocal Intraocular Lens and Two Extended Depth of Focus IOLs

Purpose To analyze the “in vitro” aberrometric pattern of a refractive IOL and two extended depth of focus IOLs. Methods A special optical bench with a Shack-Hartmann wavefront sensor (SH) was designed for the measurement. Three presbyopia correction IOLs were analyzed: Mini WELL (MW), TECNIS Symfony ZXR00 (SYM), and Lentis Mplus X LS-313 MF30 (MP). Three different pupil sizes were used for the comparison: 3, 4, and 4.7 mm. Results MW generated negative primary and positive secondary spherical aberrations (SA) for the apertures of 3 mm (−0.13 and +0.12 μm), 4 mm (−0.12 and +0.08 μm), and 4.7 mm (−0.11 and +0.08 μm), while the SYM only generated negative primary SA for 4 and 4.7 mm apertures (−0.12 μm and −0.20 μm, resp.). The MP induced coma and trefoil for all pupils and showed significant HOAs for apertures of 4 and 4.7 mm. Conclusions In an optical bench, the MW induces negative primary and positive secondary SA for all pupils. The SYM aberrations seem to be pupil dependent; it does not produce negative primary SA for 3 mm but increases for higher pupils. Meanwhile, the HOAs for the MW and SYM were not significant. The MP showed in all cases the highest HOAs.

A New Approach for the Calculation of Total Corneal Astigmatism Considering the Magnitude and Orientation of Posterior Corneal Astigmatism and Thickness

Purpose: To evaluate a new method of calculation of total corneal astigmatism based on Gaussian optics and the power design of a spherocylindrical lens (C) in the healthy eye and to compare it with keratometric (K) and power vector (PV) methods. Methods: A total of 92 healthy eyes of 92 patients (age, 17–65 years) were enrolled. Corneal astigmatism was calculated in all cases using K, PV, and our new approach C that considers the contribution of corneal thickness. An evaluation of the interchangeability of our new approach with the other 2 methods was performed using Bland–Altman analysis. Results: Statistically significant differences between methods were found in the magnitude of astigmatism (P < 0.001), with the highest values provided by K. These differences in the magnitude of astigmatism were clinically relevant when K and C were compared [limits of agreement (LoA), −0.40 to 0.62 D), but not for the comparison between PV and C (LoA, −0.03 to 0.01 D). Differences in the axis of astigmatism between methods did not reach statistical significance (P = 0.408). However, they were clinically relevant when comparing K and C (LoA, −5.48 to 15.68 degrees) but not for the comparison between PV and C (LoA, −1.68 to 1.42 degrees). Conclusions: The use of our new approach for the calculation of total corneal astigmatism provides astigmatic results comparable to the PV method, which suggests that the effect of pachymetry on total corneal astigmatism is minimal in healthy eyes.

Multichannel perimetric alterations in systemic lupus erythematosus treated with hydroxychloroquine

Systemic lupus erythematosus (SLE) is a multiorgan autoimmune disease of unknown etiology with many clinical manifestations. We report the first case of SLE in which visual alterations were evaluated with multichannel perimetry. Some achromatic and color vision alterations may be present in SLE, especially when treated with hydroxychloroquine. The sensitivity losses detected in the chromatic channels in the central zone of the visual field were consistent with the results of the FM 100 Hue color test. Likewise, the multichannel perimetry detected sensitivity losses in the parafoveal area for both chromatic channels, especially for the blue-yellow.

Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Keratoconus Eyes after Accelerated Corneal Collagen Crosslinking

Purpose To analyze the errors associated to corneal power calculation using the keratometric approach in keratoconus eyes after accelerated corneal collagen crosslinking (CXL) surgery and to obtain a model for the estimation of an adjusted corneal refractive index (nkadj) minimizing such errors. Methods Potential differences (ΔPc) among keratometric (Pk) and Gaussian corneal power (PcGauss) were simulated. Three algorithms based on the use of nkadj for the estimation of an adjusted keratometric corneal power (Pkadj) were developed. The agreement between Pk(1.3375) (keratometric power using the keratometric index of 1.3375), PcGauss, and Pkadj was evaluated. The validity of the algorithm developed was investigated in 21 keratoconus eyes undergoing accelerated CXL. Results P k(1.3375) overestimated corneal power between 0.3 and 3.2 D in theoretical simulations and between 0.8 and 2.9 D in the clinical study (ΔPc). Three linear equations were defined for nkadj to be used for different ranges of r1c. In the clinical study, differences between Pkadj and PcGauss did not exceed ±0.8 D nk = 1.3375. No statistically significant differences were found between Pkadj and PcGauss (p > 0.05) and Pk(1.3375) and Pkadj (p < 0.001). Conclusions The use of the keratometric approach in keratoconus eyes after accelerated CXL can lead to significant clinical errors. These errors can be minimized with an adjusted keratometric approach.

Preliminary validation of an optimized algorithm for intraocular lens power calculation in keratoconus

Purpose: This study aimed to evaluate the theoretical influence on intraocular lens power (PIOL) calculation of the use of keratometric approach for corneal power (Pc) calculation in keratoconus and to develop and validate an algorithm preliminarily to minimize this influence. Methods: Pcwas calculated theoretically with the classical keratometric approach, the Gaussian equation, and the keratometric approach using a variable keratometric index (nkadj) dependent on r1c(Pkadj). Differences in PIOLcalculations (ΔPIOL) using keratometric and Gaussian Pcvalues were evaluated. Preliminary clinical validation of a PIOLalgorithm using Pkadjwas performed in 13 keratoconus eyes. Results: PIOLunderestimation was present if Pcwas overestimated, and vice versa. Theoretical PIOLoverestimation up to −5.6 D and −6.2 D using Le Grand and Gullstrand eye models was found for a keratometric index of 1.3375. If nkadjwas used, maximal Δ PIOLwas ±1.1 D, with most of the values ≤±0.6 D. Clinically, PIOLunder- and over-estimations ranged from −1.1 to − 0.4 D. No statistically significant differences were found between PIOLobtained with Pkadjand Gaussian equation (P > 0.05). Conclusion: The use of the keratometric Pcfor PIOLcalculations in keratoconus can lead to significant errors that may be minimized using a Pkadjapproach.

Intrasession repeatability of refractive and ocular aberrometric measurements obtained using a multidiagnostic device in healthy eyes

Purpose To evaluate the intrasession repeatability of refractive and ocular aberrometric measurements obtained using a new multidiagnostic device in healthy eyes. Patients and methods A total of 107 eyes of 107 patients, age ranging from 23 to 65 years, were enrolled in this study. A complete eye examination was performed in all eyes, including an ocular examination using the VX120 system. Three consecutive measurements were obtained using this device to assess the intrasession repeatability of different refractive and ocular aber-rometric parameters. The within-subject standard deviation (Sw), intrasubject precision (1.96×Sw), and intraclass correlation coefficient (ICC) were calculated. Results Sw and intrasubject precision for refractive data were below 0.12 and 0.20 D, respectively, in all cases. The ICC ranged from 0.947 for the J45 power vector component to 0.997 for the sphere. Concerning aberrometric measurements Sw and intrasubject precision values were below 0.05 µm and 0.10 µm, respectively. Likewise, the ICC ranged from 0.805 for the quadrafoil root mean square to 0.954 for the primary spherical aberration. Poor correlations were found between most of the refractive parameters and their Sw (–0.033≤r≤0.053, p≥0.064). Moderate and significant positive correlations were found between the magnitude of the aberrometric parameters evaluated and their Sw (r≥0.446, p<0.001). Conclusion The new multidiagnostic device evaluated is able to provide consistent measurements of refraction and ocular aberrations in healthy eyes. Future studies should confirm if this consistency is also observed in highly aberrated eyes.