Calculation of solar ultraviolet influx in the eye considering the field of view and pupillary dilation due to sunglasses.

The media and even the specialized literature report that the ultraviolet (UV) protection for sunglasses is critical, on the grounds that sunglasses can have a counter effect if the lenses do not provide adequate UV protection. They reason that the primary and natural mechanism is that the pupil of the eye contracts to attenuate radiation and protect the inner eye under sun exposure. Therefore, if dark lenses do not provide appropriate UV protection, there is an increased UV incidence in the inner eye due to pupil dilation, which enhances the adverse effects and impacts the ocular tissues more severely than in situations without UV protection. However, no existing literature properly quantified or supported this argument. In this work, the influx of solar UV throughout the pupil of the eye was calculated in two situations: when a person wear sunglasses and when he/she does not. In both situations, the pupil dilation and the field of view (squint) were considered with their dependence on the brightness of the ambient, calculated by modeling the solar irradiation. Finally, it was assessed whether sunglasses with poor UV protection actually increase the UV influx throughout the dilated pupil compared to the non-dilated pupil. A set of 214 sunglasses lenses were tested and the results show that pupil dilation does not play an important role in the UV influx throughout the pupil. It was observed that the FOV is the main player, surpassing the pupil size contribution by up to 314.3%, disproving the common explanation. Because of the major role of the FOV, our results show that sunglasses with UV-A protection below 86% may have a slight potential to increase hazards to the eye compared to not wearing sunglasses at all. These results can have direct impact on sunglasses standards regarding the UV protection linked to the category of the lenses.

Are sunglasses appropriate for driving? Investigation and prototype for public testing.

BACKGROUND: Good vision through sunglasses is important to safety when driving and ISO 12312-1:2013 sets requirements for luminous transmittance and the transmittance of traffic signals. METHODS: We measured the spectral transmittances, 380-780 nm in 5-nm steps, of 232 sunglasses lenses and calculated the luminous transmittance, category (1-4) and transmittance of red, yellow, green and blue traffic signals (Q values). Furthermore, we developed a prototype for the general public to self-check sunglasses regarding safety for driving. We combined a white LED, a photodetector, and calculations to measure luminous transmittance, traffic signal transmittance, category, and Q-factors in sunglasses. RESULTS: Spectroscopy shows that 75% of sunglasses on the Brazilian market comply with ISO 12312-1:2013 requirements to be suitable for driving. The prototype was validated by testing 232 samples by trained users. Additionally, 60 other samples were tested by untrained users and results were compared to spectrophotometric measurements. Bland-Altman analyses showed no significant biases and 95% agreement of limits within the pre-defined tolerances for all measurements. CONCLUSIONS: Our prototype offers the general public a way to check whether their sunglasses are suitable for driving. As tested, 24.6% of sunglasses are not appropriate for driving and consumer must be more attentive to this information. SIGNIFICANCE: Immediate attention regarding checking sunglasses for driving conditions is needed for non-certified sunglasses.

Building a resistance to ignition testing device for sunglasses and analysing data: a continuing study for sunglasses standards.

BACKGROUND: Sunglasses popularity skyrocketed since its advent. The ongoing trend led to the creation of standards to protect consumers from injuries and secondary hazards due to spectacles use. In Brazil, the corresponding standard is NBR ISO 12312-1:2015 and since there is no mandatory testing, evaluating sunglasses performance provides an insight into compliance with the standard. In a continuing revision of sunglasses standards requirements, resistance to ignition is one of the concerns, since sunglasses should be protected from burning into flames at a pre-determined temperature, which may protect user of getting their sunglasses into flames if some, cigarette sparks reaches the spectacles, as an example. This paper describes the building of a resistance to ignition system and the results of 410 samples that have been tested accordingly to ISO 12312-1. METHODS: The procedure is in accordance with the resistance to ignition test. It consists of heating a steel rod to 650 °C and pressing it against the sample surface for 5 s, with a force equivalent to the rod weight. For carrying out the assessments, we have build resistance to ignition testing system and assured the testing requirements of the standard. The apparatus has an electrical furnace with a temperature acquisition circuit and electronic control that maintains the temperature of the steel rod at 650 °C. A linear actuator was designed for the project to drive the steel rod vertically and pressing it against the sunglasses samples. The control system is composed by a Freescale development board FRDM-KL25Z with an ARM Cortex-M0 embedded. We have also provided a LabView PC interface for acquiring, displaying, and storing data as well as added a physical control panel to the equipment for performing the evaluations. We assessed 410 sunglasses frames at the built apparatus, where the 410 lenses came out to be in accordance with the guidelines provided by the ignition to resistance test. Out of the 410 tested frames, 50% were made of polyamide (nylon 12); 10% were made of polyamide (nylon 11, mamona oil); 5% were made of cellulose acetate; 15% were made of ABS and 20% were made of polycarbonate. Out of the 410 tested lenses, 80% were polycarbonate; 2% were polymethyl methacrylate (PMMA); 5% CR-39 (with polarizing filter inside); 12.8% polyamide; 0.2% glass. RESULTS: For all the 410 tested spectacles frames and lenses, none burst into flames or continued to melt at the end of the procedure, being in compliance with ISO 12312-1:2013. CONCLUSIONS: The evidences show that all the tested thermoplastic and thermosetting materials are exceptionally resistant to ignition and all samples assessed comply with the resistance to ignition test. The analysis of the sunglasses made herein assures that most of sunglasses currently available to population are made of safe material.

Equivalence between solar irradiance and solar simulators in aging tests of sunglasses.

BACKGROUND: This work is part of a broader research that focuses on ocular health. Three outlines are the basis of the pyramid that comprehend the research as a whole: authors' previous work, which has provided the public to self-check their own sunglasses regarding the ultraviolet protection compatible to their category; Brazilian national survey in order to improve nationalization of sunglasses standards; and studies conducted on revisiting requirements of worldwide sunglasses standards, in which this work is inserted. It is still controversial on the literature the ultraviolet (UV) radiation effects on the ocular media, but the World Health Organization has established safe limits on the exposure of eyes to UV radiation based on the studies reported in literature. Sunglasses play an important role in providing safety, and their lenses should provide adequate UV filters. Regarding UV protection for ocular media, the resistance-to-irradiance test for sunglasses under many national standards requires irradiating lenses for 50 uninterrupted hours with a 450 W solar simulator. This artificial aging test may provide a corresponding evaluation of exposure to the sun. METHODS: Calculating the direct and diffuse solar irradiance at a vertical surface and the corresponding radiant exposure for the entire year, we compare the latter with the 50-h radiant exposure of a 450 W xenon arc lamp from a solar simulator required by national standards. RESULTS: Our calculations indicate that this stress test is ineffective in its present form. CONCLUSIONS: We provide evidence of the need to re-evaluate the parameters of the tests to establish appropriate safe limits for UV irradiance. SIGNIFICANCE: This work is potentially significant for scientists and legislators in the field of sunglasses standards to improve the requirements of sunglasses quality and safety.

Contribution to the radiation protection for sunglasses standards.

Literature establishes safe limits on the exposure of the eyes to ultraviolet radiation, for the range of 180-400 nm, including spectrally weighted and the total ultraviolet radiant exposure. Most standards for sunglasses protection only require ultraviolet protection in the spectral range of 280-380 nm to ensure the limits for effective spectrally weighted radiant exposure. Calculations of these limits were performed for 27 Brazilian state capitals, and they led to a change in the upper UVA limit to 400 nm on the 2013 review of the Brazilian standard. Moreover, because the sunlight irradiance in Brazil is quite high, integration over the 280- to 400-nm range yields an ultraviolet radiant exposure that is an average of 49% greater than that for the 280- to 380-nm range. These conclusions suggest revision on the standards.

Self-service kiosk for testing sunglasses.

BACKGROUND: Sunglasses users may only be assured on their ultraviolet protection by purchasing certified products, however they are not able to check if sunglasses are still ultraviolet (UV) protected as they age, unless they resort themselves to a professional who is qualified for using a spectrophotometer and is acknowledged on the standards for providing a report for the user. Current literature establishes safe limits on the exposure of the eyes relatively to the ultraviolet radiation exposure for the UVA and UVB ranges (280 nm - 400 nm). The UV protection is category dependent. Sunglasses are categorized from 0 to 4 and the categories are determined by the lenses transmission's percentage on the visible range (380 nm - 780 nm). METHODS: In order to overcome inaccessibility of such measurements on sunglasses, a prototype for testing ultraviolet protection on sunglasses, according to Brazilian Standards, has been developed for amateur use. The system consists of assembling UVA and UVB light sources and two UV responsive photodiode sensors, with Erythema action response for measuring UV protection; for categories measurements, combination of white light and LEDs were used for the visible range, as well as a light sensor having spectral response similar to the human eye. Electronics has been developed for controlling the measurements and software has been implemented for providing the report as well as for the user's interface. RESULTS: All the system was embedded as a self-service touch screen kiosk and provides transmittance measurements that are within the deviation limit required by NBR15111, i.e., 0.25%. Measurements were performed in over 45 sunglasses and compared to CARY 5000 - VARIAN spectrophotometer and present a good correlation for the measurements of transmittance in the visible spectral range (r2 = 0.9999) and in the ultraviolet range (r2 = 0.9997). CONCLUSIONS: The prototype identifies the UV protection, for non-corrective sunglasses, according to category of the lens and is available for the public. In addition to educating the population about the importance of wearing protected sunglasses, the prototype has also allowed the public to have access to information about the quality of protection of their own sunglasses in an easy and free testing method.

Ultraviolet analysis of donated corneas: a portable prototype.

As technology improves human vision, some procedures currently performed may be causing a decrease of the natural UV protection of the cornea. A portable dual beam system prototype was assembled for physicians for clinical studies of these effects on the corneas endowing two types of 300-400 nm evaluations: 1, regularly donated corneas and 2, simulating refractive keratectomy by corneal lamellae removal. The system performs 500 measurements/s, providing ±0.25% precision for the transmittance. The measurements performed on the prototype are 95% in agreement with Cary 17 and HR4000CG-UV-NIR Ocean Optics spectrophotometers. Preliminary studies on cadaveric corneas demonstrate that, as the stromal layer is reduced (∼150 µm depth), there is significant loss--an average of 7.1%.--of the cornea's natural UV protection. The prototype is being tested in an eye bank for routine evaluation of donor corneas.

Keratometry device for surgical support.

BACKGROUND: High astigmatisms are usually induced during corneal suturing subsequent to tissue transplantation or any other surgery which involves corneal suturing. One of the reasons is that the procedure is intimately dependent on the surgeon's skill for suturing identical stitches. In order to evaluate the influence of the irregularity on suturing for the residual astigmatism, a prototype for ophthalmic surgical support has been developed. The final intention of this prototype is to be an evaluation tool for guided suture and as an outcome diminish the postoperative astigmatism. METHODS: The system consists of hand held ring with 36 infrared LEDs, that is to be projected onto the lachrymal film of the cornea. The image is reflected back through the optics of the ocular microscope and its distortion from the original circular shape is evaluated by developed software. It provides keratometric and circularity measurements during surgery in order to guide the surgeon for uniformity in suturing. RESULTS: The system is able to provide up to 23D of astigmatism (32D - 55D range) and is +/- 0.25D accurate. It has been tested in 14 volunteer patients intraoperative and has been compared to a commercial keratometer Nidek Oculus Hand-held corneal topographer. The correlation factors are 0.92 for the astigmatism and 0.97 for the associated axis. CONCLUSION: The system is potentially efficient for guiding the surgeon on uniformity of suturing, presenting preliminary data indicating an important decrease on the residual astigmatism, from an average of 8D - for patients not submitted to the prototype guidance - to 1.4D - for patients who have actually been submitted to the prototype guidance - after the first 24 hours post-surgery and in the subsequent weeks. It also indicates that the surgeon should achieve circularity greater or equal to 98% in order to avoid postoperative astigmatisms over 1D. TRIAL REGISTRATION NUMBER: CAAE - 0212.0.004.000-09.

Optical projection mires for measurements of the radii of curvature of the cornea in biomicroscopes.

Keratometry is currently achieved by projecting a circular mire onto the patient's cornea and analyzing the size and shape of its reflected image. The projection mires are decisive for the precision of the measurement. We have previously developed a keratometric module for slit lamps, and the development of four projection mires are presented. Mire 1 is composed of optical fibers and electrical cables; Mire 2, 48 LEDs; Mire 3, optical fibers and no electrical cables; and Mire 4, mechanical parts--cable free. Mires 2-4 provide accurate keratometry measurements at slit lamps. Mire 4 is the most adequate for the clinical environment.

Portable light transmission measuring system for preserved corneas.

BACKGROUND: The authors have developed a small portable device for the objective measurement of the transparency of corneas stored in preservative medium, for use by eye banks in evaluation prior to transplantation. METHODS: The optical system consists of a white light, lenses, and pinholes that collimate the white light beams and illuminate the cornea in its preservative medium, and an optical filter (400-700 nm) that selects the range of the wavelength of interest. A sensor detects the light that passes through the cornea, and the average corneal transparency is displayed. In order to obtain only the tissue transparency, an electronic circuit was built to detect a baseline input of the preservative medium prior to the measurement of corneal transparency. The operation of the system involves three steps: adjusting the "0 %" transmittance of the instrument, determining the "100 %" transmittance of the system, and finally measuring the transparency of the preserved cornea inside the storage medium. RESULTS: Fifty selected corneas were evaluated. Each cornea was submitted to three evaluation methods: subjective classification of transparency through a slit lamp, quantification of the transmittance of light using a corneal spectrophotometer previously developed, and measurement of transparency with the portable device. CONCLUSION: By comparing the three methods and using the expertise of eye bank trained personnel, a table for quantifying corneal transparency with the new device has been developed. The correlation factor between the corneal spectrophotometer and the new device is 0,99813, leading to a system that is able to standardize transparency measurements of preserved corneas, which is currently done subjectively.

Evaluation of the corneal endothelium in rabbits treated with subconjunctival ganciclovir (DHPG)

Design: It was carried out a prospective, masked and experimental study. Objectives: to detect possible modifications of the corneal endothelium at different times after subconjunctival injection of Ganciclovir into rabbit eyes. Method: The study was conducted on 24 eyes of 12 rabbits which received 8 mg Ganciclovir diluted in 0.16 ml distilled water by the subconjunctival route in one eye (selected at random) and 0.16 ml distilled water in the control eye. Specular microscopy of the cornea was performed in enucleated eyes; the corneal egdothelium was analyzed inside the preserving medium with the magnification of 250 times. The endothelial images were observed in the monitor of a PC (250X) and in the ocular lenses of the slit lamp (40X) simultaneously. Results: Subconjunctival injection of 8mg DHPG seems not to be toxic to corneal endothelium of rabbits in a period of 48 hours, and the alterations observed after 72 hours were similar in control and treated eyes. Conclusion: Subconjunctival injection of 8mg DHPG was not toxic to corneal endothelium of rabbits in a period of 48 hours

Sistema automático para diagnóstico de úlcera de córnea / Automatic system for diagnosis of corneal ulcer

Úlceras corneanas säo feridas na córnea, com alta potencialidade de cegueira, pois, mesmo curadas, tendem a tirar a transparência. Nos países em desenvolvimento e de natureza agrícola, elas respondem por cerca de 5 por cento das causas de cegueira. Uma das formas de o clínico acompanhar o tratamento delas é pela estimativa subjetiva de sua dimensäo. Evoluçöes favoráveis tendem a promover uma diminuiçäo da ferida. No entanto, as medidas existentes para essa estimativa säo rudimentares. Assim, estamos desenvolvendo um sistema ótico, automático, para a avaliaçäo da área afetada, a ser implementado num hospital público (400 pacientes säo analisados por semana no Setor de Doenças Externas Oculares). O sistema ótico é implementado numa Lâmpada de Fenda e acoplado a um detector do tipo CCD. A imagem é apresentada num monitor de vídeo para PC, através de uma placa de interface comercial, e está sendo desenvolvido um software dedicado à determinaçäo da área de úlcera de córnea.

Implementaçäo de um banco de olhos virtual / Implementing of a virtual eyes bank

O intuito deste projeto é incluir o serviço do Banco de Olhos do H.C. de Ribeirão Preto no servidor WWW (World Wide Web) via Internet. O objetivo não se limita apenas à implantação de um "site" informativo, mas sim de um serviço efetivo para a comunidade médica, no ramo da Oftalmologia. As principais vantagens da implementação deste sistema via WWW, em relação aos demais sistema de consulta on-line existentes (telnet, gopher, renpac, etc) está na popularidades e facilidade em sua interface. O projeto subdivide-se em três partes principais: um site informativo para a população em geral, um site informativo para a comunidade médica e um servidor exclusivo para a comunidade médica. As duas primeiras partes do projeto já encontram-se disponíveis e a última está em desenvolvimento.

The main goal of this project is to include an eye bank (Banco de Olhos do Hospital das Clínicas da USP de Ribeirão Preto) service in the WWW (World Wide Web) server via Internet. The main advantages in implementing this system via WWW over the other service systems (telnet, gopher, renpac, etc) are its popularity and the interface's facility. The work is divided in three main parts: an informative site for the population in general, an informative site for the clinicians and an yxclusive server site for the clinicians. The first two parts are already done and the third one is still in development.

Desenvolvimento de um sistema para contagem automatizada de celulas endoteliais da córnea / Development of an automatic measure system of corneal endothelial cells

A análise do endotélio de uma córnea doada é um dos procedimentos para se obter um laudo final quanto à sua qualidade o desenvolvimento de um sistema ótico automatizado, que realize medidas de forma objetiva e padronizada de córneas a serem utilizadas em transplante. Como, atualmente, essa análise é feita subjetivamente, o sistema em desenvolvimento deverá proporcionar uma avaliação objetiva da córnea dentro de seu meio de conservação, evitando, portanto, a sua descentrilização e danificação. Ainda, visa a aplicação imediata do sistema no Banco de Olhos do Hospital das Clínicas de Ribeirão Preto, que é responsável pela distribuição de córneas naquela cidade e região.

The corneal endothelium analysis is one of the used ways to evaluate the quality and viability of the donated cornea for the transplanting. The goal of the present work is the development of an automatic optical system for objectively measuring the donated corneas for transplant uses. As this measurement is generally subjectively done in the brazilian eye banks, the system in development should allow an objective evaluation of the cornea in its conservation environment avoiding damages. This system is to be implemented in the Banco de Olhos do Hospital das Clínicas de Ribeirão Preto, which is responsible for distributing corenas in that region.

Sistema de medidas automáticas de áreas de úlceras de córnea / Automatic measure systems of corneal ulcer area

Úlceras1 são feridas na córnea com alta potencialidade de cegueira, pois mesmo curadas tendem a tirar a transparência. Nos países em desenvolvimento e de natureza agrícola elas respondem por cerca de 10 por cento das causas de cegueira. Uma das formas do clínico acompanhar o tratamento delas é pela estimativa subjetiva de sua dimensão. Evoluções favoráveis tedem a promover uma diminuição da ferida. No entanto, as medidas existentes para essa estimativa são rudimentares. Assim, este trabalho apresenta o desenvolvimento de um sistema de captação de imagem em Lâmpada de Fenda (instrumento utilizado para analisar as córneas) e um "software" dedicado para o delineamento e cálculo da área úlcerada para ser implementado num hospital público (400 pacientes por semana). Inserido no contexto será desenvolvida uma biblioteca de arquivamento e análise de imagens de enfermidades corneanas.

Corneal Ulcer is a very common disease in agricultura! countries and it is responsible for 10% of the blindness causes. One of the main aspects to be observed in these cases is the increasing or decreasing of the affected area. We have been developing an automatic optical system in order to evaluate the affected area (the ulcer) to be implemented in a public hospital (400 patients per week are analyzed). The optical system is implemented in a Slit Lamp and connected to a CCD detector. The image is displayed in a PC monitor by a commercial frame grabber anda dedicated software for detennining the area ofthe ulcer has been developed.

Um programa simples para a adiçao de erros de refraçäo / A simple program for the addiction of refractive measurements

O objetivo deste trabalho é apresentar um curto programa para somar todos os tipos de erros de refração discutir o seu potencial prático e as maneiras de maximizá-los. O programa foi escrito em Qbasic da Microsoft. Consiste excencialmente em um método matemático para adição de erros refrativos e dois algorítmos. O método requer o uso sequencial de apenas três equações. Os algorítmos decodificam certos resultados matemáticos para a prática. O programa soma qualquer número de esferas, cilindros, esfero-cilindros e suas combinações. Porcausa de seu pequeno tamanho ele pode também ser usado em calculadoras programáveis, com poucos ajustes.

The objective of this paper is to present a short program to add ali kinds of refractive measurements, discuss its practical potential and the ways to maximize it. The program was written in Microsoft QBasic. lt consists essentially of one method of addition of refractive en-ors and two algorithms. The method requires the sequential use of only three equations. The algorithms decode certain mathematical results to practice. The program adds any number of spheres, cylinders, sphero-cylinders and their combinations. Because of its short size it can be used also in a programmable calculators, with few adjustments

Refrator ocular automático / Ocular autorefrator

Um sistema de medidas automáticas e objetivas de erros refrativos oculares (miopia, hipermetropia e astigmatismo), utilizando tecnologia laser, foi desenvolvido. O sistema consiste em projetar, através de um laser de diodo (lambida=850nm), um alvo luminoso (um anel) no fundo do olho do paciente e os feixes de luz que emergem do olho e atingem um detector CCD matricial são analisados quanto às suas vergências. Os feixes emergentes do olho testado são divididos em seis partes (três meridianos) e são analisados dois a dois pelo CCD. A distância entre as duas imagens formadas em cada meridiano fornece o poder de refração naquele meridiano. Com os poderes de refração dos três meridianos (0 graus, 120 graus e 240 graus) é possível determinar o erro refrativo ocular. Comparativamente com os sistemas por nós anteriormente desenvolvidos, este sistema utiliza o mesmo princípio básico de medidas, porém a forma do alvo de medida e o detector utilizados, resultaram num sistema menos complexo para o alinhamento ótico e com menor introdução de erros. Medidas em olhos artificiais e em olhos humanos foram realizadas apresentando excelente concordância com os resultados obtidos em consultórios oftalmológicos e estão dentro da precisão requerida para estes tipos de medidas (0,125di e 5 graus).

An automatic and objective system for measuring ocular refractive errors (myopia, hyperopia and astigmatism) was developed using laser technology. The system consists of projecting a light target (a ring), using a diode laser (À=850nm), at the fundus of the patient's eye. The light beams scattered from the retina are analyzed by a CCD detector (matrix) regarding their vergence. The beams which emerge from the tested eye are divided into six portions (three meridians) and are analyzed in pairs by the CCD. The distances between the two images in each meridian provide the refractive power in that particular meridian. As the refractive power is obtained for the fr meridians coº' 120° e 240°), it is possible to determine the ocular refractive error. This system uses the sarne basic principle for detecting the refractive errors as our previous ones 123, but the new measuring target and the detector have provided a less complex system for the optical alignment avoiding most of the measurement errors introduced in the other system. Measurements in artificial eyes and in human eyes were done and they are in good agreement with the retinoscopic measurements and also they are as precise as these kinds of measurement require (0,125di and 5°).