Multi-toric optical element to compensate ocular astigmatism with increased tolerance under rotation.

A new, to the best of our knowledge, optical element designed to compensate regular astigmatism while exhibiting increased tolerance to rotational misalignment is introduced. The element incorporates an optical design based on concentric annular regions with slightly different cylindrical axis angular positions. To assess visual quality performance as a function of rotation, retinal image simulation and clinical assessments with an adaptive optics visual simulator were carried out. The results demonstrate the superior performance of the newly proposed element in the presence of rotational errors when compared to traditional solutions.

Subjective Straylight Index: A Visual Test for Retinal Contrast Assessment as a Function of Veiling Glare.

Spatial aspects of visual performance are usually evaluated through visual acuity charts and contrast sensitivity (CS) tests. CS tests are generated by vanishing the contrast level of the visual charts. However, the quality of retinal images can be affected by both ocular aberrations and scattering effects and none of those factors are incorporated as parameters in visual tests in clinical practice. We propose a new computational methodology to generate visual acuity charts affected by ocular scattering effects. The generation of glare effects on the visual tests is reached by combining an ocular straylight meter methodology with the Commission Internationale de l'Eclairage's (CIE) general disability glare formula. A new function for retinal contrast assessment is proposed, the subjective straylight function (SSF), which provides the maximum tolerance to the perception of straylight in an observed visual acuity test. Once the SSF is obtained, the subjective straylight index (SSI) is defined as the area under the SSF curve. Results report the normal values of the SSI in a population of 30 young healthy subjects (19 ± 1 years old), a peak centered at SSI = 0.46 of a normal distribution was found. SSI was also evaluated as a function of both spatial and temporal aspects of vision. Ocular wavefront measures revealed a statistical correlation of the SSI with defocus and trefoil terms. In addition, the time recovery (TR) after induced total disability glare and the SSI were related; in particular, the higher the RT, the greater the SSI value for high- and mid-contrast levels of the visual test. No relationships were found for low contrast visual targets. To conclude, a new computational method for retinal contrast assessment as a function of ocular straylight was proposed as a complementary subjective test for visual function performance.

A study on disability glare vision in young adult subjects.

The full assessment of the visual system must include the evaluation of the optical quality of the eye and neural visual functions. The objective evaluation of the retinal image quality is often carried out by computing the point spread function (PSF) of the eye. The central part of the PSF is associated with optical aberrations and the peripheral areas with scattering contributions. In that sense, visual acuity and contrast sensitivity function tests can be considered the perceptual neural response to those contributions characterizing the eye's PSF. However, in natural viewing conditions, visual acuity tests may provide good vision while contrast sensitivity tests can reveal visual impairment in glare vision conditions, such as exposure to bright light sources or night driving conditions. Here we present an optical instrument for the study of disability glare vision under extended Maxwellian illumination to assess the contrast sensitivity function under glare conditions. The limit of the Total Disability Glare threshold, tolerance, and glare adaptation will be investigated as a function of the angular size of the glare source (GA) and the contrast sensitivity function in young adult subjects.

Peripheral Refraction of Two Myopia Control Contact Lens Models in a Young Myopic Population.

Peripheral refraction can lead to the development of myopia. The aim of this study was to compare relative peripheral refraction (RPR) in the same cohort of uncorrected (WCL) and corrected eyes with two different soft contact lenses (CL) designed for myopia control, and to analyze RPR depending on the patient's refraction. A total of 228 myopic eyes (114 healthy adult subjects) (−0.25 D to −10.00 D) were included. Open-field autorefraction was used to measure on- and off- axis refractions when uncorrected and corrected with the two CLs (dual focus (DF) and extended depth of focus (EDOF)). The RPR was measured every 10° out to 30° in a temporal-nasal orientation and analyzed as a component of the power vector (M). The average RPR for all subjects was hyperopic when WCL and when corrected with EDOF CL design, but changed to a myopic RPR when corrected with DF design. Significant differences were found between RPR curves with both CLs in all the eccentricities (Bonferroni correction p < 0.008, except 10°N). An incremental relationship between relative peripheral refraction at 30 degrees and myopia level was found. It is concluded that the two CLs work differently at the periphery in order to achieve myopia control.

Optical Quality Variation of Different Intraocular Lens Designs in a Model Eye: Lens Placed Correctly and in an Upside-Down Position.

INTRODUCTION: Intraocular lenses (IOLs) may lose their optical quality if they are not correctly placed inside the capsular bag once implanted. One possible malpositioning of the IOL could be the implantation in an upside-down position. In this work, three aspheric IOLs with different spherical aberration (SA) have been designed and numerically tested to analyse the optical quality variation with the IOL flip, and misalignments, using a theoretical model eye. METHODS: Using the commercial optical design software OSLO, the effect of decentration and tilt was evaluated by numerical ray tracing in two conditions: in their designed position and flipped with respect to the planned position (IOL is implanted upside down). The theoretical model eye used was the Atchison model eye. Seven IOL designs of +27.00 diopters were used: a lens with negative SA to correct the corneal SA, a lens to partially correct the corneal SA, and a lens to not add any SA to the cornea (aberration-free IOL). These lenses were designed with the aspherical surface located on the anterior and posterior IOL surface. A lens with no aspherical surfaces was also included. For the optical quality analysis, the modulation transfer function (MTF) was used, together with the Zernike wavefront aberration coefficients of defocus, astigmatism, and primary coma. RESULTS: Off-centring and tilting the IOL reduced overall MTF values and increased wavefront aberration errors. With the IOL correctly positioned within the capsular bag, an aberration-free IOL is the best choice for maintaining optical quality. When the IOL is flipped inside the capsular bag, the optical quality changes, with the aberration-free IOL and the IOL without aspheric surfaces providing the worst results. With the lens in an upside-down position, an IOL design to partially correct corneal SA shows the best optical quality results in decentration and tilt, in terms of MTF and wavefront aberrations. CONCLUSION: The aberration-free IOL is the best choice when minimal postoperative errors of decentration or tilt are predicted. With IOL flip, the negative SA lens design is the best choice, regarding the root mean square wavefront aberrations. However, in a proper IOL implantation, the IOL designed to partially compensate the corneal SA including asphericity on its posterior surface is the better possible option, even in the presence of decentration or tilt.

Rare Alkali Elements as Markers of Local Glass Working in Medieval Tolmo de Minateda (Spain).

Analytical data of Roman and early Islamic glass established several primary glass production groups linked to glassmaking centres in the Levant and in Egypt. In contrast, the activities of secondary glass workshops are largely invisible in the compositional fingerprint of first millennium glass. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of 261 glass finds from the Visigothic settlement of Tolmo de Minateda (Spain) revealed a site-specific contamination pattern due to secondary glass processing and recycling, namely the enrichment of the glass batch by a unique combination of rare alkali elements (Li, K, Rb, Cs). With a median of 21 ppm, Li is particularly distinctive. Elevated lithium contents (Li>30 ppm) are also one of the characteristic features of Iberian plant ash glass from the Islamic period. The earliest known examples of this type of glass were found among the ninth-century remains from Tolmo.

Effect of decentration, tilt and rotation on the optical quality of various toric intraocular lens designs: a numerical and experimental study.

Toric intraocular lenses (T-IOLs) may lose their optical quality if they are not correctly positioned inside the capsular bag once implanted. In this work, T-IOLs with cylinder powers of +1.50, +4.50 and +7.50 D and differing degrees of spherical aberration have been designed, manufactured and tested in vitro using a commercial optical bench that complies with the requirements of standard ISO 11979-2. Moreover, the effect of tilt and rotation on optical quality was assessed by means of numerical ray tracing on an astigmatic eye model, while the effect of decentration was evaluated numerically and experimentally.

Iterative-Trained Semi-Blind Deconvolution Algorithm to Compensate Straylight in Retinal Images.

The optical quality of an image depends on both the optical properties of the imaging system and the physical properties of the medium in which the light travels from the object to the final imaging sensor. The analysis of the point spread function of the optical system is an objective way to quantify the image degradation. In retinal imaging, the presence of corneal or cristalline lens opacifications spread the light at wide angular distributions. If the mathematical operator that degrades the image is known, the image can be restored through deconvolution methods. In the particular case of retinal imaging, this operator may be unknown (or partially) due to the presence of cataracts, corneal edema, or vitreous opacification. In those cases, blind deconvolution theory provides useful results to restore important spatial information of the image. In this work, a new semi-blind deconvolution method has been developed by training an iterative process with the Glare Spread Function kernel based on the Richardson-Lucy deconvolution algorithm to compensate a veiling glare effect in retinal images due to intraocular straylight. The method was first tested with simulated retinal images generated from a straylight eye model and applied to a real retinal image dataset composed of healthy subjects and patients with glaucoma and diabetic retinopathy. Results showed the capacity of the algorithm to detect and compensate the veiling glare degradation and improving the image sharpness up to 1000% in the case of healthy subjects and up to 700% in the pathological retinal images. This image quality improvement allows performing image segmentation processing with restored hidden spatial information after deconvolution.

Composition and origins of decorated glass from Umayyad Cordoba (Spain).

Recent archaeological excavations carried out in the western suburbs of Cordoba (Spain) brought to light numerous fragments of archaeological glass from the caliphal period (929-1031 CE). The typological and compositional analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of 66 fragments enabled the identification of different types of base glass and glass working techniques, identifying local productions, imports and decorative imitations of eastern models. The studied fragments include Mesopotamian, Levantine, Egyptian and possibly Sicilian soda-rich plant ash glass categories, and various glass-decorating techniques such as mould-blowing, pressing, cutting, staining or gilding. The systematic comparison of the trace element patterns of several relief-cut objects identified both imported ware and a locally manufactured sample, whereas all mould-blown pieces were made from locally sourced raw materials. Iberian glassworkers seem to have preferred mould-blowing, probably because of the distinct working properties of locally available high lead glass. The results thus confirm the continuous long-distance exchange of vitreous material, as well as the existence of multiple glassmaking centres in the Iberian Peninsula, illustrating a link between secondary glass working techniques and chemical composition. Furthermore, the identification of several fragments belonging to the same object based on chemical composition allowed us to reconstruct entire vessels and thereby expand the repertoire of known typologies circulating in Umayyad Spain. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40494-021-00505-4.

Misalignment and tilt effect on aspheric intraocular lens designs after a corneal refractive surgery.

PURPOSE: To numerically evaluate and compare the tolerance to misalignment and tilt of aspheric intraocular lenses (IOLs) designed for three eyes: with standard cornea and with simulated corneas after myopic and hyperopic laser ablation surgery. METHODS: Three aspheric IOLs of +20.00 diopter (D) with different spherical aberration (SA) ([Formula: see text]) values have been designed using a theoretical model eye. Drastic changes on the theoretical eye anterior corneal asphericity have been performed to simulate myopic and hyperopic refractive surgeries. The effect of IOL misalignment and tilt on the image quality has been evaluated using a commercial optical software design for the three eye models. Image quality was assessed from the modulation transfer function (MTF), root mean square (RMS) values of defocus, astigmatism, coma and spherical aberration ([Formula: see text]), and retinal images obtained from a visual simulator using an aleatory optotype of 0.00 LogMar visual acuity (VA). RESULTS: IOL misalignment and tilt reduced MTF values in general, and increased wavefront aberrations errors. Aberration-free IOLs maintained best the MTF values when misalignments were applied, together with good on-axis optical quality. IOLs with negative SA ([Formula: see text]) correction decreased the MTF value under 0.43 for misalignments values higher than 0.50 mm with the three corneas. The effect of misalignment on RMS astigmatism and coma was correlated with the IOL SA ([Formula: see text]) and with the three corneas. CONCLUSIONS: This theoretical study shows that the largest degradation in image quality arises for the IOL with the highest amount of spherical aberration ([Formula: see text]). Moreover, it has been found that the aspherical design has a more influential role in misalignment tolerance than in tilt tolerance.

Ex novo development of lead glassmaking in early Umayyad Spain.

This study investigates glass finds from the Iberian Peninsula as a proxy for identifying the mechanisms underlying technological transformations and innovation in the wake of the Arab conquest in the seventh and eighth centuries CE. High-resolution laser ablation inductively coupled plasma mass spectrometry data combined with lead isotope analyses of a precisely dated (mid-eighth century to 818 CE) glass assemblage from the Rabad of Saqunda in Cordoba, capital of Umayyad Spain, enabled us to trace the origins of an Iberian glassmaking industry and to unambiguously link it to the exploitation of local raw materials. The analytical data reveal increased recycling, some isolated imports of Islamic plant ash glasses from Mesopotamia, and, most notably, the development of a new type of glassmaking technology that resorted to the use of lead slag from silver and lead mining and processing in the region around Cordoba. The production of this type of lead glass from Saqunda was short-lived and was subsequently refined by introducing additional fluxing agents. The technological innovation of Islamic glassmaking in Spain evidently drew inspiration from adjacent high-temperature technologies. The revival of glass and the development of a local glassmaking tradition was indirectly related to the wider processes of Islamization, such as the introduction of glazed ceramics that are compositionally related to the lead glasses from Saqunda.

Evaluation of the optical performance for aspheric intraocular lenses in relation with tilt and decenter errors.

PURPOSE: To evaluate and compare the effect of misalignment and tilt on the optical performance of different aspheric intraocular lens (IOL) designs. METHODS: Three aspheric IOLs with a different quantity of spherical aberration (SA) have been designed and the effect of IOL misalignment and tilt on the imaging quality of an eye model has been numerically assessed using a commercial optical design software. The prototypes have been manufactured by lathe turning and tested in vitro using the same optical bench (PMTF, Lambda-X) that complies with International Organization for Standardization standard 11979-2 requirements. Image quality was evaluated from the modulation transfer functions (MTFs), through-focus modulation transfer functions (TF-MTFs), root mean square (RMS) values of defocus, astigmatism and coma, and images of the United States Air Force (USAF) target were taken. A comparison with the optical performance of spherical IOLs has also been performed. RESULTS: Intraocular lens misalignment and tilt increased wavefront aberrations; the effect of misalignment on root mean square (RMS) astigmatism and coma was positively correlated with the spherical aberration of the IOL. Aberration-free IOLs showed the highest MTF for all misalignment values and for IOLs with negative SA correction the MTF decays below 0.43 when they are decentered 0.50 mm. CONCLUSIONS: Aspherical IOLs are more sensitive than spherical IOLs to misalignment or tilt, depending on their SA correction. The optical degradation caused by IOL misalignment had a greater effect on IOL designs with a higher amount of negative spherical aberration. In contrast, the effect of tilt on the optical performance was less sensitive to the IOL design.

Wide-field direct ocular straylight meter.

The impact of the intraocular straylight (IOS) on the visual performance and retinal imaging is still a challenging topic. Direct optical methods to measure IOS avoid psychophysical approaches and interaction with the patient. In this work, we developed an optical instrument providing direct imaging measurement of IOS based on the double-pass technology. The system was tested in an artificial eye IOS model constructed with holographic diffusers and validated with theoretical simulations.

Glass import and production in Hispania during the early medieval period: The glass from Ciudad de Vascos (Toledo).

One hundred and forty-one glass fragments from medieval Ciudad de Vascos (Toledo, Spain) were analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The glasses fall into three types according to the fluxing agents used: mineral natron, soda-rich plant ash, and a combination of soda ash and lead. The natron glasses can be assigned to various established primary production groups of eastern Mediterranean provenance. Different types of plant ash glasses indicate differences in the silica source as well as the plant ash component, reflecting changing supply mechanisms. While the earlier plant ash groups can be related to Islamic glasses from the Near East, both in terms of typology and composition, the chemical signature of the later samples appear to be specific to glass from the Iberian Peninsula. This has important implications for our understanding of the emerging glass industry in Spain and the distribution patterns of glass groups and raw materials. The plant ash that was used for the Vascos glasses is rich in soda with low levels of potash, similar to ash produced in the eastern Mediterranean. It could therefore be possible that Levantine plant ash was imported and used in Islamic period glass workshops in Spain. Unlike central and northern Europe where an independent glass industry based on potassium-rich wood ash developed during the Carolingian period, the prevalence of soda ash and soda ash lead glass on the Iberian Peninsula indicates its commercial and technological interconnection with the Islamic east. Our study thus traces several stages leading to the development of a specifically Spanish primary glassmaking industry.

Repeatability and Reproducibility of Virtual Subjective Refraction.

PURPOSE: To establish the repeatability and reproducibility of a virtual refraction process using simulated retinal images. METHODS: With simulation software, aberrated images corresponding with each step of the refraction process were calculated following the typical protocol of conventional subjective refraction. Fifty external examiners judged simulated retinal images until the best sphero-cylindrical refraction and the best visual acuity were achieved starting from the aberrometry data of three patients. Data analyses were performed to assess repeatability and reproducibility of the virtual refraction as a function of pupil size and aberrometric profile of different patients. RESULTS: SD values achieved in three components of refraction (M, J0, and J45) are lower than 0.25D in repeatability analysis. Regarding reproducibility, we found SD values lower than 0.25D in the most cases. When the results of virtual refraction with different pupil diameters (4 and 6 mm) were compared, the mean of differences (MoD) obtained were not clinically significant (less than 0.25D). Only one of the aberrometry profiles with high uncorrected astigmatism shows poor results for the M component in reproducibility and pupil size dependence analysis. In all cases, vision achieved was better than 0 logMAR. A comparison between the compensation obtained with virtual and conventional subjective refraction was made as an example of this application, showing good quality retinal images in both processes. CONCLUSIONS: The present study shows that virtual refraction has similar levels of precision as conventional subjective refraction. Moreover, virtual refraction has also shown that when high low order astigmatism is present, the refraction result is less precise and highly dependent on pupil size.

Retinal Image Simulation of Subjective Refraction Techniques.

Refraction techniques make it possible to determine the most appropriate sphero-cylindrical lens prescription to achieve the best possible visual quality. Among these techniques, subjective refraction (i.e., patient's response-guided refraction) is the most commonly used approach. In this context, this paper's main goal is to present a simulation software that implements in a virtual manner various subjective-refraction techniques--including Jackson's Cross-Cylinder test (JCC)--relying all on the observation of computer-generated retinal images. This software has also been used to evaluate visual quality when the JCC test is performed in multifocal-contact-lens wearers. The results reveal this software's usefulness to simulate the retinal image quality that a particular visual compensation provides. Moreover, it can help to gain a deeper insight and to improve existing refraction techniques and it can be used for simulated training.

Sphero-cylindrical error for oblique gaze as a function of the position of the centre of rotation of the eye.

PURPOSE: New designs of ophthalmic lenses customised for particular wearing conditions (e.g., vertex distance or wrap tilt angle) have emerged during the last few years. However, there is limited information about the extent of any improvement in visual quality of these products. The aim of this work was to determine whether customisation according to the centre of rotation of the eye (CRE) improves visual quality for oblique gaze in monofocal spherical lenses. METHODS: Conventional spherical lenses were designed by numerical ray tracing with back vertex powers (BVP) ranging from +8 to -8 dioptres (D) and base curves from 0 to 8 D. The wavefront error at oblique gaze (40°) was computed for each design with CRE positions from 20 to 35 mm. Sphero-cylindrical (SC) error was calculated using wavefront Zernike coefficients, considering only monochromatic aberrations. Visual acuity in logMAR was estimated following the Raasch empirical regression model. RESULTS: SC error and visual acuity maps were calculated for each BVP as a function of base curves and CRE in a graded colour scale. From SC error maps maximum spherical and cylindrical errors (MSE and MCE) of 1.49 D and -1.24 D respectively were found for BVP from 0 to -2 D, 2.27 D and -1.90 D for BVP from -2 D to -4 D, 2.59 D and -2.20 D for lenses from -4 D to -6 D and 2.63 D and -2.28 D for lenses from -6 D to -8 D. Concerning positive lenses, we obtained MSE and MCE of 0.37 D and -1.35 D respectively for lenses from 0 D to +2 D, 0.39 D and -2.23 D for lenses from +2 D to +4 D and 0.36 D and -2.73 D for lenses from +4 D to +6 D. Regarding visual acuity maps for 40° oblique gaze, significant loss of visual acuity (>0.30 logMAR, Snellen 6/12, 20/40, decimal 0.50) was found for BVP as low as -2 D. Clinically negligible high order aberration levels (equivalent spherical power <0.25 D) were found for all cases. CONCLUSIONS: We calculated SC error and visual acuity maps as a function of base curves and CRE position for a set of spherical lenses at oblique gaze. These maps could be useful as a clinical guide to select the best base as a function of CRE and BVP for each patient. It was found that negative lenses with low BVP provided high SC error when they were designed with low bases. However, high BVP negative lenses with low SC error were found for medium bases and low CRE or for low bases and high CRE positions. In the case of positive lenses, the dependence of SC error with CRE position was less noticeable. Finally, high order aberrations did not have a significant influence over visual quality.

Closed-loop adaptive optics with a single element for wavefront sensing and correction.

We propose a closed-loop adaptive optical arrangement based on a single spatial light modulator that simultaneously works as a correction unit and as the key element of a wavefront sensor. This is possible by using a liquid crystal on silicon display whose active area is divided into two halves that are respectively programmed for sensing and correction. We analyze the performance of this architecture to implement an adaptive optical system. Results showing a closed-loop operation are reported, as well as a proof of concept for dealing with aberrations comparable to those typically found in human eyes.

Reconfigurable Shack-Hartmann sensor without moving elements.

We demonstrate wavefront sensing with variable measurement sensitivity and dynamic range by means of a programmable microlens array implemented onto an off-the-shelf twisted nematic liquid crystal display operating as a phase-only spatial light modulator. Electronic control of the optical power of a liquid lens inserted at the aperture stop of a telecentric relay system allows sensing reconfigurability without moving components. Results of laboratory experiments show the ability of the setup to detect both smooth and highly aberrated wavefronts with adequate sensitivity.

Nephron-sparing surgery: our experience in open and laparoscopic approach in 254 cases.

OBJECTIVES: The majority of renal cell carcinomas are now incidentally detected as small renal masses in asymptomatic patients due to the widespread use of ultrasound and new improved noninvasive abdominal imaging modalities. Nephron-sparing surgery is the treatment of choice for patients with small renal masses in presence of normal contralateral kidney or in presence of an anatomic or functional solitary kidney. We reviewed retrospectively our experience in open and laparoscopic partial nephrectomy. METHODS: The records for all patients who underwent nephron-sparing surgery for a renal mass since 1995 at British Hospital of Buenos Aires and Hospital Aleman and since 2000 at Hospital Universitario Austral were reviewed. The most relevant data of 246 patients were collected, with special focus on demographic data, operative details, pathology results, complications and outcome in cancer control. RESULTS: We have performed 254 nephron-sparing surgeries. Open partial nephrectomy was performed in 220 procedures and the laparoscopic partial nephrectomy since 2001 in 34 patients. The indication was elective or relative in 236 patients with 8 patients with bilateral tumors and 18 tumors in a solitary kidney. The pedicle was clamped in 168 procedures with hypothermia in 43 patients. Mean ischemia time was 24.7 minutes. Average tumor size was 3.49 cm. The pathologic findings demonstrate a carcinoma in 193 cases and benign lesions in 61 patients (24%). One patient presented a positive surgical margin in the pathologic examination, but subsequent nephrectomy was negative for residual tumor. One patient presented a pseudo-tumoral mass on follow-up on CT scan and MRI, but nephrectomy was negative for residual tumor. There were postoperative complications in 20 patients (7.9 %). Oncologic follow up was available in 84% of the patients for an average of 46.6 months showing progression with metastasis in 8 patients. Local recurrence was observed in 4 patients (2%). One patient developed a tumor in the contralateral kidney 20 months after partial nephrectomy and another one 10 years later. The cancer specific survival and overall survival rates were 98 % and 95% respectively. In the last year the laparoscopic approach duplicated the indications of all previous years. CONCLUSIONS: Open partial nephrectomy is considered nowadays the gold standard treatment of small renal masses, and in our experience it is a safe and effective technique of treatment of these tumors. The evolution of the technology and the acquirement of laparoscopic skills allow us in selected cases to duplicate the open approach in a laparoscopic way, obtaining similar results.