Analysis of parameters for the automatic computation of the tear film break-up time test based on CCLRU standards.

Dry eye syndrome is affecting a remarkable percentage of population. The prevalence is 10-15% of normal population, and 18-30% of contact lenses users. The break-up time (BUT) is a clinical test used for the diagnosis of this disease. In this work, we perform an analysis of parameters for a global and a local automatic computation of the BUT measure, based on criteria of specificity and sensitivity. We have tested our methodology on a dataset composed of 18 videos annotated by 4 different experts. The local analysis preserves the results of the global approach providing useful additional information about the break-up tear zone.

Automatic classification of the interferential tear film lipid layer using colour texture analysis.

The tear film lipid layer is heterogeneous among the population. Its classification depends on its thickness and can be done using the interference pattern categories proposed by Guillon. This papers presents an exhaustive study about the characterisation of the interference phenomena as a texture pattern, using different feature extraction methods in different colour spaces. These methods are first analysed individually and then combined to achieve the best results possible. The principal component analysis (PCA) technique has also been tested to reduce the dimensionality of the feature vectors. The proposed methodologies have been tested on a dataset composed of 105 images from healthy subjects, with a classification rate of over 95% in some cases.

[Effect of double anaesthetic Colicursi (tetracaine 0.1% and oxybuprocaine 0.4%) on central and paracentral corneal thickness]. / Efecto de la instilación del colicursi anestésico doble (tetracaína 0,1% y oxibuprocaína 0,4%) sobre el espesor corneal central y paracentral.

OBJECTIVE: To study the effect of 1 drop of combined topical anaesthesia (tetracaine 0.1% and oxybuprocaine 0.4%) on central corneal thickness (CCT) values and at 2.5 mm from the corneal centre in nasal, temporal, superior and inferior hemi meridians, monitored by Orbscan over a period of 16 minutes. MATERIALS AND METHODS: The corneal thickness of 12 right eyes of 12 young healthy men was determined using the Orbscan Topography System. Values were determined at the centre and paracentral regions 2.5 mm from the centre every 2 minutes for 16 minutes before and after the administration of 1 drop of double anaesthetic Colircusi which contains tetracaine 0.1% and oxybuprocaine 0.4%. RESULTS: There was no obvious trend of central and paracentral corneal thickness value change before and after administration of Colircusi (paired ANOVA, p>0.05). Although corneal thickness variation was not statistically significant, higher differences were observed at the 6 minute time-point for CCT and at 8 minutes for nasal paracentral corneal thickness. CONCLUSIONS: One drop of double anaesthetic Colircusi with tetracaine 0.1% and oxibuprocaine 0.4% does not produce any significant change in central corneal thickness or in paracentral regions 2.5 mm from the centre (nasal, temporal, superior and inferior hemi meridians).

Efecto de la instilación del Colicursi(R) anestésico doble (tetracaína 0.1% y oxibuprocaína 0.4%) sobre el espesor corneal central y paracentral / Effect of double anaesthetic colicursi(R) (tetracaine 0.1% and oxibuprocaine 0.4%) on central and paracentral corneal thickness

Objetivo: El objetivo del presente trabajo es estudiar el efecto sobre el espesor corneal central (ECC) y paracentral a 2,5 mm del centro en los hemimeridianos nasal, temporal, superior e inferior, de la anestesia tópica en la que se combinan el clorhidrato de tetracaina 0,1% y el clorhidrato de oxibuprocaina 0,4%. Material y método: Se determinó el espesor corneal central y paracentral a 2,5 mm del centro de la córnea en los ojos derechos de 12 varones jóvenes mediante Orbscan. Las medidas se realizaron cada dos minutos durante un periodo de 16 minutos previo y posterior a la instilación del anestésico. Resultados: El análisis estadístico muestra que no existe variación en el espesor corneal central y paracentral antes y después de la instilacion del anestésico Colircusi(R) anestésico doble con clorhidrato tetracaina 0,1% y clorhidrato de oxibuprocaina 0,4% (ANOVA para medidas repetidas, p>0,05). Aunque no fueron estadísticamente significativas la mayor variación de espesor se observa para el ECC a los 6 minutos y para el paracentral a los 8 minutos en el hemimeridiano nasal. Conclusiones: Una gota de Colircusi(R)® anestésico doble con clorhidrato tetracaina 0,1% y clorhidrato de oxibuprocaina 0,4% no produce una variación significativa del ECC ni paracentral a 2 mm del centro en los hemimeridianos nasal, temporal, superior e inferior

Objective: To study the effect of 1 drop of combinedtopical anaesthesia (tetracaine 0.1% and oxybuprocaine0.4%) on central corneal thickness (CCT)values and at 2.5 mm from the corneal centre innasal, temporal, superior and inferior hemi meridians,monitored by Orbscan over a period of 16minutes.Materials and methods: The corneal thickness of12 right eyes of 12 young healthy men was determinedusing the Orbscan Topography System. Valueswere determined at the centre and paracentralregions 2.5 mm from the centre every 2 minutes for16 minutes before and after the administration of 1drop of double anaesthetic Colircusi(R) which containstetracaine 0.1% and oxybuprocaine 0.4%.Results: There was no obvious trend of central andparacentral corneal thickness value change beforeand after administration of Colircusi(R) (pairedANOVA, p>0.05). Although corneal thicknessvariation was not statistically significant, higherdifferences were observed at the 6 minute timepoint for CCT and at 8 minutes for nasal paracentralcorneal thickness.Conclusions: One drop of double anaestheticColircusi® with tetracaine 0.1% and oxibuprocaine0.4% does not produce any significant change incentral corneal thickness or in paracentral regions2.5 mm from the centre (nasal, temporal, superiorand inferior hemi meridians)(AU)

[The relationships between ocular optical components and implications in the process of emmetropization]. / Relación entre los componentes ópticos oculares e implicaciones en el proceso de emetropización.

PURPOSE: To report the relationship between different optical ocular components and the influence of axial length on emmetropization. METHODS: 109 young university students, divided into five groups, were enrolled in this study: emmetropes, hyperopes, low myopes, moderate myopes and high myopes. Intraocular parameters and topographic corneal analyses were performed by ultrasonography and videokeratoscopy respectively. RESULTS: Anterior chamber depth and axial length were found to correlate significantly in eyes with axial lengths less than 24 mm (r = 0.441; p < 0.001) However this correlation was not found in eyes with longer axial lengths (r = 0.098; p = 0.527). Lens thickness showed an inverse correlation with axial length for shorter eyes (r = 0.391; p < 0.001), whereas any correlation in longer eyes was associated with moderate to high levels of myopia. Anterior corneal curvature only correlated, although weakly, with vitreous chamber depth for shorter eyes (r = 0.363; p < 0.003). CONCLUSION: Differences in optical parameters of the human eye displayed different associations in longer eyes. A lack of correlation was seen between ocular components in eyes with higher myopia, corresponding to myopia in excess of 2.00 D.

Relación entre los componentes ópticos oculares e implicaciones en el proceso de emetropización / The realtionships between ocular optical components and implication sin the process of emmetropization

Objetivo: Determinar la relación entre los diferentes componentes ópticos oculares y la emetropización en función de la longitud axial (LA). Métodos: Participaron 109 jóvenes universitarios divididos en cinco grupos según el error refractivo: emétropes, hipermétropes, miopes bajos, miopes moderados y miopes altos. La medida de los parámetros intraoculares y el análisis de la topografía corneal se realizó mediante ultrasonografía y videoqueratoscopia respectivamente. Resultados: Se encontró una correlación estadísticamente significativa entre la profundidad de la cámara anterior (PCA) y la LA en ojos con LA menor de 24 mm (r = 0,441; p < 0,001). Sin embargo en ojos con LA mayor no se encontró tal relación (r = 0,098; p = 0,527). El espesor del cristalino (EC) mostró una correlación inversa con la LA para los ojos con LA < 24 mm (r = 0,391; p < 0,001), siendo nula en el caso de ojos con LA ≥ 24 mm. La curvatura corneal (RC) sólo mostró una débil correlación con la profundidad de la cámara vítrea (PCV) en ojos con LA < 24 mm (r = 0,363; p < 0,003). Conclusión: Los parámetros ópticos del ojo humano se relacionan de distinta forma según el tamaño del ojo, encontrándose en los ojos más miopes una ausencia de coordinación entre los componentes ópticos oculares, que según los resultados de este estudio, es a partir de 2,00 D

Purpose: To report the relationship between different optical ocular components and the influence of axial length on emmetropization. Methods: 109 young university students, divided into five groups, were enrolled in this study: emmetropes, hyperopes, low myopes, moderate myopes and high myopes. Intraocular parameters and topographic corneal analyses were performed by ultrasonography and videokeratoscopy respectively. Results: Anterior chamber depth and axial length were found to correlate significantly in eyes with axial lengths less than 24 mm (r = 0.441; p < 0.001) However this correlation was not found in eyes with longer axial lengths (r = 0.098; p = 0.527). Lens thickness showed an inverse correlation with axial length for shorter eyes (r = 0.391; p < 0.001), whereas any correlation in longer eyes was associated with moderate to high levels of myopia. Anterior corneal curvature only correlated, although weakly, with vitreous chamber depth for shorter eyes (r = 0.363; p < 0.003). Conclusion: Differences in optical parameters of the human eye displayed different associations in longer eyes. A lack of correlation was seen between ocular components in eyes with higher myopia, corresponding to myopia in excess of 2.00 D (Arch Soc Esp Oftalmol 2008; 83: 307-316)

[Diurnal variations of central and paracentral corneal thickness and curvature]. / Variaciones diurnas de espesor y curvatura corneal central y paracentral.

OBJECTIVE: Corneal topography and thickness has clinical importance in contact lens fitting and refractive surgery, however repeated measurement of corneal thickness and curvature is complicated by the natural phenomenon of diurnal variation. Our aim was determine diurnal variations of central and paracentral corneal thickness and curvature over a period of ten hours. MATERIALS AND METHODS: Corneal thickness and curvature of 10 right eyes of 10 young healthy men were determined by Orbscan Topography System and EyeSys videokeratoscope respectively. Both parameters were determined for central and paracentral regions 1 mm and 2 mm from the centre of the cornea at 2-hour internals for ten hours. RESULTS: The cornea was thickest and flattest on awakening. There was a difference in corneal thickness (ANOVA, Schfféc method p< 0.05) and curvature (ANOVA, Tamhane method p< 0.05) over time for all the corneal locations studied, with greater changes observed in the peripheral corneal data. The minimum value was 10 and 8 hours after eye opening for central and paracentral zones, respectively. Change in central and paracentral corneal thickness was strongly correlated with corneal curvature, except for the 2 mm nasal and superior semi-meridians. CONCLUSIONS: These data indicate a shift in corneal thickness and curvature that can be of clinical relevance as individual changes vary greatly.

Variaciones diurnas de espesor y curvatura corneal central y paracentral / Diurnal variations of central and paracentral corneal thickness and curvature

Objetivo: La topografía y espesor de la córnea tienen una gran importancia clínica en la adaptación de lentes de contacto y en cirugía refractiva. Sin embargo, la repetibilidad en las medidas de estos parámetros se ve comprometida por el fenómeno natural de las variaciones diurnas. Nuestro objetivo es determinar las variaciones diurnas de espesor y curvatura corneal central y paracentral durante un periodo de 10 horas. Material y método: Se determinó la curvatura y espesor corneal en los ojos derechos de 10 varones jóvenes mediante Orbscan y videoqueratoscopio respectivamente. Ambos parámetros fueron determinados para la zona central y paracentral a 1 y 2 mm del centro de la córnea, cada dos horas durante un periodo de 10 horas. Resultados: La córnea presentaba su espesor máximo y curvatura mínima al abrir el ojo. Se observó una variación estadísticamente significativa de espesor (ANOVA, método de Schefféc p< 0,05) y de curvatura (ANOVA, método de Tamhane p < 0,05) a lo largo del día en todas las localizaciones estudiadas, si bien la variación y los rangos de valores en la zona paracentral eran mayores. Los valores mínimos para ambos parámetros se observaron a las 10 y 8 horas después de abrir los ojos para las zonas central y paracentral respectivamente. Las variaciones de espesor y curvatura estaban altamente correlacionadas excepto para la localización nasal y superior a 2 mm del centro. Conclusiones: Estos datos evidencian un cambio en espesor y curvatura que pueden ser de relevancia clínica atendiendo a la variación individual encontrada

Objective: Corneal topography and thickness has clinical importance in contact lens fitting and refractive surgery, however repeated measurement of corneal thickness and curvature is complicated by the natural phenomenon of diurnal variation. Our aim was determine diurnal variations of central and paracentral corneal thickness and curvature over a period of ten hours. Materials and methods: Corneal thickness and curvature of 10 right eyes of 10 young healthy men were determined by Orbscan Topography System and EyeSys videokeratoscope respectively. Both parameters were determined for central and paracentral regions 1 mm and 2 mm from the centre of the cornea at 2-hour internals for ten hours. Results: The cornea was thickest and flattest on awakening. There was a difference in corneal thickness (ANOVA, Schfféc method p< 0.05) and curvature (ANOVA, Tamhane method p< 0.05) over time for all the corneal locations studied, with greater changes observed in the peripheral corneal data. The minimum value was 10 and 8 hours after eye opening for central and paracentral zones, respectively. Change in central and paracentral corneal thickness was strongly correlated with corneal curvature, except for the 2 mm nasal and superior semi-meridians. Conclusions: These data indicate a shift in corneal thickness and curvature that can be of clinical relevance as individual changes vary greatly (Arch Soc Esp Oftalmol 2008; 83: 183-192)

[Changes in axial length/corneal radius ratio (AL/CR) according to refractive state of the eye. Relationship with ocular components]. / Variación de la ratio longitud axial/radio corneal (LA/RC) con el estado refractivo ocular. Relación con los componentes oculares.

PURPOSE: Determination of the role of the axial length/corneal radius ratio (AL/CR) in the refractive state and investigation of its relationship with the ocular optical components: AL, CR, anterior chamber depth (ACD), crystalline lens thickness (CT) and vitreous chamber depth (VCD). METHODS: The RE (right eye) of 193 University students 22.27 (SD 3.24) years, with different refractive errors (spherical equivalent range: +3.00 D to -11.00 D), being divided into: emmetropes, hyperopes and myopes (low, moderate and high). The ACE, the CT, the VCD and the AL were measured by ultrasonography (unidimensional echography); and the mean CR by videokeratoscopy. RESULTS: The value of AL/CR obtained was 2.98 (SD 0.69) for emmetropes, 2.89 (SD 0.87) for hyperopes, 3.01 (SD 0.07) in low myopias, 3.10 (SD 0.11) in moderate myopias and 3.23 (SD 0.12) in high myopias. The AL/CR ratio showed a higher correlation with the refractive error. Besides, all the refractive groups were observed to have lower CE values as the AL/CR increased. This tendency is statistically significant in hyperopes, emmetropes and low myopes; and is not in moderate and high myopias. All the study groups could be observed to have a positive and statistically significant correlation between AL/CR and ACD. CONCLUSION: The ratio AL/CR is the most important parameter and the best predictor of the refractive state of the human eye. It provides important information on how best to determine the degree of emmetropization given by the crystalline, decreasing its power and the ACD in concordance with the LA. A value for the ratio AL/CR above 3.00 could be considered as a risk factor for the development of myopia in emmetropic eyes.

Variación de la ratio longitud axial/radio corneal (LA/RC) con el estado refractivo ocular: Relación con los componentes oculares / Canges in axial lenght/corneal radius ratio (AL/CR) according to refractive state of the eye. Relationship with ocular componets

Objetivo: Determinación del papel de la ratio longitud axial/radio corneal (LA/RC) en el estado refractivo e investigación de su relación con los componentes ópticos oculares: LA, RC, profundidad de cámara anterior (PCA), espesor del cristalino (EC) y profundidad de cámara vítrea (PCV). Métodos: Se ha examinado el ojo derecho (OD) en 193 estudiantes universitarios de 22,27 (DE 3,24) años, con diversas formas de error refractivo (rango equivalente esférico: +3,00 D a –11,00 D), dividiéndose en emétropes, hipermétropes y miopes (bajos, moderados y altos). La PCA, el EC, la PCV y la LA se han medido por ultrasonografía (ecografía unidimensional); y, el RC promedio por videoqueratoscopía. Resultados: El valor de LA/RC resultó ser 2,98 (DE 0,69) para emétropes, 2,89 (DE 0,87) para hipermétropes, 3,01 (DE 0,07) en miopías bajas, 3,10 (DE 0,11) en miopías moderadas y 3,23 (DE 0,12) en miopías altas. La ratio LA / RC presentaba la más alta correlación con el error refractivo. Además, en todos los grupos refractivos se observó que a medida que aumentaba el valor de LA / RC, el EC tendía a disminuir. Esta tendencia es estadísticamente significativa en hipermétropes, emétropes y miopes bajos; no siéndolo en miopías moderadas y altas. En todos los grupos de estudio se observa una correlación positiva y estadísticamente significativa entre LA/RC y PCA. Conclusión: La ratio LA/RC es el parámetro más determinante y el mejor predictor del estado refractivo del ojo humano. Proporciona información importante para determinar el grado de emetropización que aporta el cristalino, reduciendo su potencia y, la PCA en concordancia con la LA. Una ratio LA/RC superior a 3,00 podría considerarse un factor de riesgo para el desarrollo de miopía en ojos emétropes(AU)

Purpose: Determination of the role of the axial length/corneal radius ratio (AL/CR) in the refractive state and investigation of its relationship with the ocular optical components: AL, CR, anterior chamber depth (ACD), crystalline lens thickness (CT) and vitreous chamber depth (VCD). Methods: The RE (right eye) of 193 University students 22.27 (SD 3.24) years, with different refractive errors (spherical equivalent range: +3.00 D to –11.00 D), being divided into: emmetropes, hyperopes and myopes (low, moderate and high). The ACE, the CT, the VCD and the AL were measured by ultrasonography (unidimensional echography); and the mean CR by videokeratoscopy. Results: The value of AL/CR obtained was 2.98 (SD 0.69) for emmetropes, 2.89 (SD 0.87) for hyperopes, 3.01 (SD 0.07) in low myopias, 3.10 (SD 0.11) in moderate myopias and 3.23 (SD 0.12) in high myopias. The AL/CR ratio showed a higher correlation with the refractive error. Besides, all the refractive groups were observed to have lower CE values as the AL/CR increased. This tendency is statistically significant in hyperopes, emmetropes and low myopes; and is not in moderate and high myopias. All the study groups could be observed to have a positive and statistically significant correlation between AL/CR and ACD. Conclusion: The ratio AL/CR is the most important parameter and the best predictor of the refractive state of the human eye. It provides important information on how best to determine the degree of emmetropization given by the crystalline, decreasing its power and the ACD in concordance with the LA. A value for the ratio AL/CR above 3.00 could be considered as a risk factor for the development of myopia in emmetropic eyes(AU)