The corneal maps displayed on commercially available corneal topography instruments are really one-dimensional, defining quantities only along a meridian, and ignoring shape information along any other direction. Both axial and instantaneous power have the drawbacks that there is a singularity at the center data point on the videokeratograph axis, and the computed powers and appearance of the c...

PURPOSE To quantify the error introduced by videokeratographic corneal topography devices in using a paraxial formula to calculate power over the entire corneal surface, including areas removed from the central paraxial region where the formula is known to be invalid. METHODS Corneal refractive power and two paraxial power approximations were computed as a function of distance from the apex f...

In this paper, we numerically simulated a glass-based all-optical 1×N power splitter with eleven different configurations using soliton breakup in a nonlinear medium. It is shown that in addition to reconfigurability of the proposed splitter, its power splitting ratio is tunable up to some extent values too. Nonlinear semivectorial iterative finite difference beam propagation method (IFD-...

In 100 eyes of 50 patients central corneal thickness was measured comparing optical to ultrasound pachymetry. With optical pachymetry the values were 1 to 40 micrometer (microns) lower in 64 eyes compared to ultrasound pachymetry. With ultrasound pachymetry the values were 1 to 18 microns lower in 26 eyes compared to optical pachymetry. In 10 cases no difference in pachymetry readings was seen ...

PURPOSE To compare the relative advantages and disadvantages of four different representations of corneal power--identified as instantaneous, axial, position, and refractive--based on curvature, slope, coordinate position, and focal properties, respectively. METHOD The four types of corneal power were evaluated by examining their interrelationship for 12 hypothetical corneal shapes chosen to ...

BACKGROUND In our clinical experience we discovered that EEG band power may be correlated with corneal nerve injury in retinoblastoma patients. This study aimed to investigate biomarkers obtained from electroencephalography (EEG) recordings to reflect corneal nerve injury in retinoblastoma patients. MATERIAL AND METHODS Our study included 20 retinoblastoma patients treated at the Department of ...

Purpose. To assess the repeatability and reproducibility of ocular biometry and intraocular lens (IOL) power measurements obtained by ophthalmology residents using an AL-Scan device, a novel optical biometer. Methods. Two ophthalmology residents were instructed regarding the AL-Scan device. Both performed ocular biometry and IOL power measurements using AL-Scan, three times on each of 128 eyes,...

PURPOSE To obtain an accurate algorithm for calculating the keratometric index that minimizes the errors in the calculation of corneal power assuming only a single corneal surface in the range of corneal curvatures of the normal population. METHODS Corneal power was calculated by using the classical keratometric index and also by using the Gaussian equation. Differences between types of calcu...

PURPOSE To investigate the effect of hinge position on corneal topography after laser in situ keratomileusis (LASIK) for myopia. SETTING Academic center and refractive surgery practice. METHODS Topography data obtained from 89 eyes of 46 patients after LASIK were analyzed. Using a system of Cartesian coordinates, data along the horizontal and vertical axes were analyzed, measuring sagittal ...