Yes / Background: The aim was to profile transient accommodative axial length changes from early adulthood to advanced presbyopia and to determine whether any differences exist between the responses of myopic and emmetropic individuals. Methods: Ocular biometry was measured by the LenStar biometer (Haag-Streit, Switzerland) in response to zero, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes, aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline lens thickness with accommodation. Accommodative responses were measured sequentially by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Hiroshima, Japan). Results: Axial length increased significantly with accommodation (p < 0.001), with a mean corrected increase in axial length of 2 18 μm and 8 16 μm observed at 3.00 and 4.50 D, respectively. The magnitude of accommodative change in axial length was not dependent on refractive error classification (p = 0.959); however, a significant reduction in the magnitude and variance of axial length change was evident after 43 to 44 years of age (p < 0.002). Conclusion: The negative association between transient increase in axial length and age, in combination with reduced variance of data after age 43 to 44 years, is consistent with a significant increase in posterior ocular rigidity, which may be influential in the development of presbyopia. / DL received funds from the College of Optometrists, UK

no / PURPOSE: To estimate refractive indices used by the Lenstar biometer to translate measured optical path lengths into geometrical path lengths within the eye. METHODS: Axial lengths of model eyes were determined using the IOLMaster and Lenstar biometers; comparing those lengths gave an overall eye refractive index estimate for the Lenstar. Using the Lenstar Graphical User Interface, we noticed that boundaries between media could be manipulated and opposite changes in optical path lengths on either side of the boundary could be introduced. Those ratios were combined with the overall eye refractive index to estimate separate refractive indices. Furthermore, Haag-Streit provided us with a template to obtain 'air thicknesses' to compare with geometrical distances. RESULTS: The axial length estimates obtained using the IOLMaster and the Lenstar agreed to within 0.01 mm. Estimates of group refractive indices used in the Lenstar were 1.340, 1.341, 1.415, and 1.354 for cornea, aqueous, lens, and overall eye, respectively. Those refractive indices did not match those of schematic eyes, but were close in the cases of aqueous and lens. Linear equations relating air thicknesses to geometrical thicknesses were consistent with our findings. CONCLUSION: The Lenstar uses different refractive indices for different ocular media. Some of the refractive indices, such as that for the cornea, are not physiological; therefore, it is likely that the calibrations in the instrument correspond to instrument-specific corrections and are not the real optical path lengths.

La myopie est maintenant considérée comme un problème de santé publique. La forte myopie est associée à des pathologies oculaires comme le glaucome, les cataractes précoces et les problèmes de rétine. La longueur axiale de l’oeil, en plus de sa réfraction, sont des mesures importantes pour assurer le suivi de la progression myopique. Bien que ces variables aient été étudiées en position primaire, peu d’auteurs se sont penchés sur leur variation en périphérie. Ce mémoire a pour principal objectif d’étudier, chez des myopes, la variation de la longueur axiale du centre vers la périphérie de la rétine dans les méridiens horizontaux et verticaux. De plus, elle vise à investiguer si la relation qui existe entre la longueur axiale et la réfraction de l’oeil varie selon l’angle auquel ces variables sont mesurées. 53 participants (83% F; 25,6 ± 2,7 ans) ont été recrutés pour cette étude. Trente minutes après l’instillation de gouttes permettant la dilatation pupillaire, des mesures de longueurs axiales (Lenstar) et de réfractions (Grand Seiko WAM-5500) en position primaire et en périphérie ont été prises en rétine horizontale (10°, 20°, 30°) et verticale (5°, 10°) par rapport à la fovéa. Les résultats obtenus montrent une symétrie horizontale de la longueur axiale jusqu’à une excentricité de 20° et suggèrent une symétrie sur 360° jusqu’à 10°. L’analyse statistique a également permis de confirmer que la relation entre la longueur axiale et la réfraction demeurait la même jusqu’à 20° en nasal, alors qu’elle changeait significativement à 20° en rétine temporale. En comparant la rétine nasale à la rétine temporale, les relations obtenues à 10° étaient similaires, alors que les relations obtenues à 20° étaient différentes. En conclusion, la longueur axiale de l’oeil ainsi que sa relation avec la réfraction demeurent symétriques jusqu’à des angles qui varient entre 10 et 20 degrés. Ceci pourrait influencer la conception des produits optiques développés pour le contrôle de la progression de la myopie. / Today, myopia is considered a public health issue. High myopia is associated with eye pathologies such as glaucoma, early cataracts and retinal abnormalities. In fact, the axial length of the eye, in addition to its refraction, are important measures for monitoring myopic progression. Although these variables have been studied in the central retina, few authors have examined their variation in the peripheral retina. The main objective of this study is to evaluate the variation in the axial length from the center to the periphery of the retina in the horizontal and vertical meridians of myopes. In addition, it aims to investigate whether the relationship between axial length and refraction varies depending on the angle at which these variables are measured. 53 participants (83% F; 25.6 ± 2.7 years) were recruited for this study. Thirty minutes after instillation of drops causing pupillary dilation, measurements of central and peripheral axial lengths (Lenstar) and refractions (Grand Seiko WAM-5500) were taken on the horizontal (10°, 20°, 30°) and vertical (5°, 10°) meridians of the retina relative to the fovea. The results demonstrate horizontal symmetry of the axial length up to an eccentricity of 20° and suggest a symmetry over 360° up to an angle of 10°. Statistical analysis also confirmed that the relationship between axial length and refraction remained the same up to 20° nasally, while it changed significantly at 20° temporally. By comparing the nasal retina to the temporal retina, the relationships obtained at 10° were similar, while the relationships obtained at 20° were different. In conclusion, the axial length of the eye as well as its relation to refraction remain symmetrical up to angles varying between 10 and 20 degrees. This could influence the design of optical products developed for the control of the progression of myopia.

Objetivo: Estudar os componentes refrativos da hipermetropia em crianças com ambliopia por esotropia, comparando os olhos amblíopes com os olhos contralaterais. Métodos: Foram incluídos 37 pacientes de 5 a 8 anos de idade, com hipermetropia bilateral e ambliopia por esotropia. Foi realizada avaliação oftalmológica completa, incluindo refratometria sob cicloplegia, ceratometria e biometria ultrassonográfica modo A. Foram registrados profundidade da câmara anterior, espessura do cristalino, profundidade da câmara vítrea e comprimento axial total. O poder refrativo do cristalino foi calculado pelas equações de Bennett. Para comparar erro refrativo, poder da córnea, poder calculado do cristalino e componentes ecobiométricos entre os olhos amblíopes e os olhos contralaterais foi empregado o teste t de Student pareado. Para avaliar a relação entre os principais componentes refrativos individuais e o erro refrativo foram empregados o coeficiente de correlação de Pearson e a análise de regressão linear. Foram construídos também modelos multivariados, incluindo comprimento axial, poder da córnea e poder do cristalino. Resultados: Os olhos amblíopes apresentaram hipermetropia mais alta, menor poder da córnea, maior poder do cristalino, menor profundidade da câmara vítrea e menor comprimento axial. Não houve diferença entre os olhos quanto à profundidade da câmara anterior ou à espessura do cristalino. A variável que apresentou correlação mais forte com o erro refrativo foi a razão comprimento axial/raio de curvatura da córnea (r = -0.92, p < 0.001 nos olhos amblíopes e r = - 0.87, p < 0.001 nos olhos contralaterais). O comprimento axial representou 39,2% da explicação da variabilidade do erro refrativo nos olhos amblíopes e 35,5% nos olhos contralaterais. O modelo que combinou comprimento axial e poder da córnea explicou 85,7% e 79,6% da variabilidade do erro refrativo, respectivamente. Houve correlação significante entre comprimento axial e poder da córnea, indicando diminuição do poder da córnea com o aumento do comprimento axial e os coeficientes de correlação foram semelhantes entre os olhos amblíopes (r = -0.53, p <0.001) e os olhos contralaterais (r = -0.57, p < 0.001). Houve correlação significante entre comprimento axial e poder do cristalino, indicando diminuição do poder do cristalino com o aumento do comprimento axial e os coeficientes de correlação também foram semelhantes entre os olhos amblíopes (r = -0.72, p < 0.001) e os olhos contralaterais (r = -0.69, p < 0.001). Conclusão: As correlações entre os principais componentes refrativos e sua contribuição individual para o erro refrativo foram semelhantes nos olhos amblíopes e nos olhos contralaterais de crianças com esotropia, a despeito da hipermetropia mais alta nos olhos amblíopes / Purpose: To study the refractive components of hyperopia in children with esotropic amblyopia, comparing amblyopic eyes with fellow eyes. Methods: Thirty-seven patients (5 to 8 years old) with bilateral hyperopia and esotropic amblyopia underwent a comprehensive ophthalmic examination, including cycloplegic refraction, keratometry and A-scan ultrasonography. Anterior chamber depth, lens thickness, vitreous chamber depth and total axial length were recorded. The refractive power of the crystalline lens was calculated using Bennett`s equations. Paired Students t-tests were used to compare refractive error, corneal power, calculated lens power and ocular biometric measurements between amblyopic eyes and their fellow eyes. The relationship between the major oculometric parameters and refractive error was assessed using Pearson correlation coefficients and linear regression. Multivariable models including axial length, corneal power and lens power were also constructed. Results: Amblyopic eyes were found to have significantly more hyperopic refraction, lesser corneal power, greater lens power, shorter vitreous chamber depth and shorter axial length, despite similar anterior chamber depth and lens thickness. The strongest correlation with refractive error was observed for the axial length/corneal radius ratio (r = -0.92, p < 0.001 for amblyopic and r = -0.87, p < 0.001 for fellow eyes). Axial length accounted for 39.2% of the refractive error variance in amblyopic eyes and 35.5% in fellow eyes. The combination of axial length and corneal power accounted for 85.7% and 79.6% of the refractive error variance respectively. A significant correlation was found between axial length and corneal power, indicating decreasing corneal power with increasing axial length, and they were similar for amblyopic eyes (r = -0.53, p < 0.001) and fellow eyes (r = -0.57, p < 0.001). A significant correlation was found between axial length and lens power, indicating decreasing lens power with increasing axial length, and they were also similar for amblyopic eyes (r = -0.72, p < 0.001) and fellow eyes (r = -0.69, p < 0.001). Conclusion: The correlations among the major refractive components and their individual contribution to refractive error were similar in amblyopic and non-amblyopic eyes in esotropic children, despite more hyperopic refraction in amblyopic eyes

Objetivo: Estudar os componentes refrativos da hipermetropia em crianças com ambliopia por esotropia, comparando os olhos amblíopes com os olhos contralaterais. Métodos: Foram incluídos 37 pacientes de 5 a 8 anos de idade, com hipermetropia bilateral e ambliopia por esotropia. Foi realizada avaliação oftalmológica completa, incluindo refratometria sob cicloplegia, ceratometria e biometria ultrassonográfica modo A. Foram registrados profundidade da câmara anterior, espessura do cristalino, profundidade da câmara vítrea e comprimento axial total. O poder refrativo do cristalino foi calculado pelas equações de Bennett. Para comparar erro refrativo, poder da córnea, poder calculado do cristalino e componentes ecobiométricos entre os olhos amblíopes e os olhos contralaterais foi empregado o teste t de Student pareado. Para avaliar a relação entre os principais componentes refrativos individuais e o erro refrativo foram empregados o coeficiente de correlação de Pearson e a análise de regressão linear. Foram construídos também modelos multivariados, incluindo comprimento axial, poder da córnea e poder do cristalino. Resultados: Os olhos amblíopes apresentaram hipermetropia mais alta, menor poder da córnea, maior poder do cristalino, menor profundidade da câmara vítrea e menor comprimento axial. Não houve diferença entre os olhos quanto à profundidade da câmara anterior ou à espessura do cristalino. A variável que apresentou correlação mais forte com o erro refrativo foi a razão comprimento axial/raio de curvatura da córnea (r = -0.92, p < 0.001 nos olhos amblíopes e r = - 0.87, p < 0.001 nos olhos contralaterais). O comprimento axial representou 39,2% da explicação da variabilidade do erro refrativo nos olhos amblíopes e 35,5% nos olhos contralaterais. O modelo que combinou comprimento axial e poder da córnea explicou 85,7% e 79,6% da variabilidade do erro refrativo, respectivamente. Houve correlação significante entre comprimento axial e poder da córnea, indicando diminuição do poder da córnea com o aumento do comprimento axial e os coeficientes de correlação foram semelhantes entre os olhos amblíopes (r = -0.53, p <0.001) e os olhos contralaterais (r = -0.57, p < 0.001). Houve correlação significante entre comprimento axial e poder do cristalino, indicando diminuição do poder do cristalino com o aumento do comprimento axial e os coeficientes de correlação também foram semelhantes entre os olhos amblíopes (r = -0.72, p < 0.001) e os olhos contralaterais (r = -0.69, p < 0.001). Conclusão: As correlações entre os principais componentes refrativos e sua contribuição individual para o erro refrativo foram semelhantes nos olhos amblíopes e nos olhos contralaterais de crianças com esotropia, a despeito da hipermetropia mais alta nos olhos amblíopes / Purpose: To study the refractive components of hyperopia in children with esotropic amblyopia, comparing amblyopic eyes with fellow eyes. Methods: Thirty-seven patients (5 to 8 years old) with bilateral hyperopia and esotropic amblyopia underwent a comprehensive ophthalmic examination, including cycloplegic refraction, keratometry and A-scan ultrasonography. Anterior chamber depth, lens thickness, vitreous chamber depth and total axial length were recorded. The refractive power of the crystalline lens was calculated using Bennett`s equations. Paired Students t-tests were used to compare refractive error, corneal power, calculated lens power and ocular biometric measurements between amblyopic eyes and their fellow eyes. The relationship between the major oculometric parameters and refractive error was assessed using Pearson correlation coefficients and linear regression. Multivariable models including axial length, corneal power and lens power were also constructed. Results: Amblyopic eyes were found to have significantly more hyperopic refraction, lesser corneal power, greater lens power, shorter vitreous chamber depth and shorter axial length, despite similar anterior chamber depth and lens thickness. The strongest correlation with refractive error was observed for the axial length/corneal radius ratio (r = -0.92, p < 0.001 for amblyopic and r = -0.87, p < 0.001 for fellow eyes). Axial length accounted for 39.2% of the refractive error variance in amblyopic eyes and 35.5% in fellow eyes. The combination of axial length and corneal power accounted for 85.7% and 79.6% of the refractive error variance respectively. A significant correlation was found between axial length and corneal power, indicating decreasing corneal power with increasing axial length, and they were similar for amblyopic eyes (r = -0.53, p < 0.001) and fellow eyes (r = -0.57, p < 0.001). A significant correlation was found between axial length and lens power, indicating decreasing lens power with increasing axial length, and they were also similar for amblyopic eyes (r = -0.72, p < 0.001) and fellow eyes (r = -0.69, p < 0.001). Conclusion: The correlations among the major refractive components and their individual contribution to refractive error were similar in amblyopic and non-amblyopic eyes in esotropic children, despite more hyperopic refraction in amblyopic eyes

No / The aims of the research may be outlined as follows: to measure the degree of transient axial elongation during the accommodation response in emmetropic and myopic young adults. To evaluate the effect of refractive error and accommodative demand on transient axial elongation of the eye. Axial length of the right eye was measured in 30 emmetropes and 30 myopes, by using the IOLMaster (Carl Zeiss Meditec, Inc., Dublin, CA), while accommodative stimuli of 0, 2, 4 and 6 D were presented with a Badal optometer. Axial length increased in both emmetropic and myopic subjects during short periods of accommodative stimulation. Greater transient increases in axial length were observed in myopic than in emmetropic subjects. The mean axial elongation with a 6-D stimulus to accommodation was 0.037 mm in emmetropes and 0.058 mm in myopes (P = 0.02). The degree of transient axial elongation correlated well with the stimulus to accommodation in emmetropes and myopes. Anterior chamber depth decreased, on average, by 0.19 mm in emmetropes and 0.18 mm in myopes when observing a 6-D stimulus to accommodation. During relatively short periods of accommodative stimulation, axial length increases in both emmetropic and myopic young adults. At higher levels of accommodative stimulation, a significantly greater transient increase in axial length is observed in myopic subjects than in their emmetropic counterparts.

No description available.

No description available.

O crescimento e as dimensões das estruturas oculares em cães de diversas raças têm sido objeto de estudo. Sabe-se que quanto mais longilíneo o crânio, maior o comprimento axial do bulbo ocular. O objetivo deste trabalho foi acompanhar o desenvolvimento das dimensões dos componentes oculares (comprimento axial, espessura da lente, profundidade da câmara anterior e da câmara vítrea) e relacionar as medidas com o sexo, a idade, tamanho, medidas do crânio e peso de cães da raça Cavalier King Charles Spaniel, uma raça braquicéfala. Foram realizadas 117 medidas biométricas oculares em cães variando entre 15 dias e 36 meses de idade, não sedados, sentados ou deitados em posição esternal, utilizando-se ultrassonografia modo-B com transdutor microconvexo de 8 MHz. No momento de cada medida ocular os cães foram pesados e as medidas de comprimento, altura, distâncias fronto-occipital, fronto-nasal, bizigomática e circunferência do crânio foram registradas. As estruturas oculares mostraram uma curva de rápido crescimento entre 15 dias e 4 meses de idade e uma curva suave de crescimento até os 12 meses, idade em que cessou o crescimento do cão (altura e comprimento). Os machos apresentaram medidas maiores de altura, comprimento e crânio do que fêmeas, porém não houve diferença significativa entre os parâmetros de biometria ocular de machos e fêmeas. O valor médio de comprimento axial do bulbo para cães adultos (acima de 12 meses) foi de 18,10 ± 0,48 mm, para a espessura da lente, de 7,15 ± 0,16 mm, para profundidade da câmara anterior, de 2,05 ± 0,37 mm e para a profundidade da câmara vítrea, de 8,91 ± 0,30 mm. Não houve diferença entre as medidas dos olhos direito e esquerdo. Os resultados sugerem que a curva de crescimento ocular acompanha a curva de crescimento do cão, fato semelhante ao que ocorre em diferentes espécies estudadas por outros autores. Em cães adultos, não foi observada relação entre as medidas dos componentes oculares e as medidas de altura, comprimento, peso e tamanho do crânio. Foi estabelecida uma tabela de crescimento correlacionando comprimento axial do bulbo e idade do cão com a finalidade de padronizar esses dados para a raça. / Ocular biometry and ocular growth has been studied in dogs of different breeds. It\'s already known that dogs with longer skulls have longer axial length of the eye. This study aimed to evaluate the development of ocular dimensions (axial length of the bulbus, lens thickness, anterior and vitreous chamber depth) in Cavalier King Charles Spaniels, a braquicephalic breed, and its relationship to age, gender, weight, height and lenght of the dog and dimensions of the head. Ocular dimensions were obtained from 117 measurements between 15 days and 3 years old, in standing nonsedated animals using B-mode ultrasound with an 8 MHz curvilinear probe. At the same time the dogs were weighted and height, length and head dimensions (head circumference, fronto-occipital, fronto-nasal distance and bizigomatic distances) were recorded. The ocular parameters showed a rapid growth curve from 15 days to 4 months and then a slow curve until 12 months, same age that the height and length ceased its growth. Males showed significant higher measurements of height, length and head parameters than females, but no difference in ocular biometry was found between males and females. The mean value for axial lenght for adults (over 12 months) was 18,10 ± 0,48 mm, for lens thickness was 7,15 ± 0,16 mm, for anterior chamber depth was 2,05 ± 0,37 mm and for vitreous chamber depth was 8,91 ± 0,30 mm. There was no significant difference between left and right eyes. Results suggest that eye growth curves accompanies dogs height, length, head size growth curves, what is similar to the data found in different species studied by other authors. There was no relation between eye parameters and dog\'s height, length, head size or weight in adult individuals. A table was established correlating axial length of the bulbus and age to be used as a reference for the breed.

Myopia is a refractive defect of the eye in which collimated light produces images focused in front of the retina. Myopia can be artificially induced in animal models by form deprivation (form deprivation myopia, FDM) or by application of negative lenses (lens induced myopia, LIM). In this study myopia was induced using diffusers. The project had two main aims: 1. To determine if there is an interaction between the GABAergic system and dopaminergic system in the retina in terms of myopia? 2. To determine if there is an interaction between the GABAergic system and cholinergic system in the retina in terms of myopia? Firstly, an experiment focusing on the interaction between dopaminergic receptors antagonists and GABAC receptor antagonist was developed. Comparison of the different drug treated eye with the control was found and the effects of combination injections were compared to individual drug injections. Use of different blockers for various subtype of receptors simplified the understandings the underlying pharmacological interventions for GABAC receptor antagonist TPMPA. The D1 subtype of receptors was found to be involved in transmission of signals from GABAC receptors. Our results showed that D1 receptor antagonist SCH-23390 antagonizes the actions of TPMPA. In addition to this it was also found that possibly 5HT receptor may also play an important role in modulation of signaling from GABA receptor to dopaminergic receptors in the retina. These results were consistent with the drug combination effects for agonists. GABA A/C receptor agonist muscimol negativate the efficacy of D1 receptor agonist SKF-38393 but the activity of D2/4 receptor agonist quinpirole was not affected by muscimol. Although dopaminergic receptors are found to interact with GABAergic signaling, but an alternative interaction with anticholinergic (most widely studied antimyopic agents) could not be ruled out. This problem led to a follow-up experiment, in which GABA receptors intervention in anticholinergic agents was studied. The GABAergic receptor agonist muscimol when injected with anticholinergics (atropine and pirenzepine) showed a moderate interaction. As muscimol interacted with atropine to a lesser extent a more specific M1/5 receptor antagonist pirenzepine (earlier found to inhibit myopia) was used under these circumstances. The second aim to study the interaction between muscimol and pirenzepine showed more interaction with GABAA/C receptor agonist. There were data suggesting that there is a muscarinic and GABAergic interaction in retina, such that each modulation of each receptor had an effect on FDM. However, a drug combination treatment helped in understanding the underlying mechanism. Several previous studies have indicated that there exist a strong interaction between excitatory neurotransmitter acetylcholine and inhibitory transmitter GABA in retina. The results of this study indicate a similar finding. Thus results of this study may be summarized as: 1. D1 antagonists and not D2 antagonists blocks the antimyopic effects of GABAC antagonist TPMPA 2. GABA A/C agonist muscimol partially blocks the antimyopic activity of anticholinergics (e.g. atropine and pirenzepine).