Publication: Caracterización de la cicloposición ocular mediante el ángulo fóvea-disco óptico. Evaluación de nuevos métodos de medida
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2020-01-08
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Universidad Complutense de Madrid
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Abstract
En el polo posterior de un ojo sano el disco óptico se halla en posición nasal y ligeramente superior a fóvea. El ángulo que forman estas dos estructuras define la cicloposición ocular y presenta una gran variabilidad interindividual. Una cicloposición fuera del rango normal se denomina torsión ocular y supone una rotación anómala del globo ocular. Puede tener su origen en un estrabismo ciclovertical primario, una alteración de los músculos extraoculares, una afectación orbitaria o una cirugía ocular. En estos casos la cicloposición aporta información esencial acerca del componente torsional de la desviación. En ojos sanos supone, además, una referencia anatómica estable, utilizada en cirugía refractiva y en análisis de patología retiniana. El método gold standard en la evaluación de la cicloposición es la medida del ángulo fóveadisco óptico (AFD) en retinografía. Se determina mediante el ángulo que forma una línea que une la fóvea con el centro del disco óptico respecto a la horizontal. Su valor ronda los 7º en dirección inferior y es una medida repetible y reproducible. Los estudios discrepan en cuanto a las diferencias interoculares y entre sexos, y acerca de la relación entre cicloposición y edad. Además, no se ha descrito el valor del cambio mínimo detectable (CMD) asociado a la medida del AFD, que determina la diferencia entre exploraciones repetidas que debe considerarse un cambio real, no debido al error de medida. Los inconvenientes de la técnica incluyen la necesidad de dilatación pupilar y de exportar la imagen a un software externo para su medida. Además, precisa la determinación manual exacta de la posición foveal, dificultada en ojos con patología que afecta al área macular. La cicloposición puede también valorarse cualitativamente mediante la inclinación de las arcadas vasculares temporales, que viajan a ambos lados del eje fóvea-disco óptico y rotan con el ojo cuando existe torsión ocular. Los autores Parsa y Kumar han descrito un método para cuantificar esta inclinación que no ha sido comprobado junto al AFD, y puede ser de utilidad cuando la fóvea no se localice adecuadamente. Por último, el tomógrafo Spectralis cuenta con el software FoDi, que mide el AFD de manera semiautomática. Detecta la fóvea basándose en la fijación del paciente (importante si existe mala definición macular), y no precisa dilatación pupilar ni exportar la imagen para su medida. Ningún estudio ha comparado el AFD en imagen con el proporcionado por el tomógrafo Spectralis...
At the posterior pole of a healthy eye, the optic disc is localized in a nasal and slightly superior position from the fovea. The angle subtended by these two landmarks is called ocular cycloposition and presents a large interindividual variability. Cycloposition out of the normal range is considered ocular torsion and indicates an anomalous rotation of the globe. It may be due to a primary cyclovertical strabismus, an extraocular muscle condition, an orbital disorder or an ocular surgery. In these cases, cycloposition provides essential information about the torsional component of the ocular deviation. In addition, it is considered a stable anatomic landmark in healthy eyes, used in refractive surgery and in retinal pathology analyses. The gold standard method for cycloposition evaluation is the quantification of the disc-fovea angle (DFA) in fundus photograph. It is determined by the inclination angle of a line connecting the fovea and the optic disc centre. Its value is around 7º downwards and it’s a repeatable and reproducible measurement. Authors disagree on interocular and sex differences, and about the relationship between age and cycloposition. The minimal detectable change (MDC) value is not described in relation to the DFA evaluation. It determines if a difference in repeated examinations may be considered as a real change or due to an instrumental error. The disadvantages of the technique include the need of pupillary dilation and the exportation of the fundus image to an external measure software. Besides, it requires the accurate manual determination of the fovea position, which is difficult in eyes with pathology affecting macular area. Cycloposition can also be qualitatively assessed by the inclination of temporal vascular arcades. These vessels travel at both sides of the optic disc-fovea axis and rotate when ocular torsion exists. The authors Parsa and Kumar described a method for quantifying this inclination. It may be a valuable tool when there is no proper location of the fovea and it has not been correlated with the gold standard. Finally, the built-in software of the Spectralis tomograph named FoDi (fovea-to-disc alignment) provides a semi-automatic measurement of the DFA. Pupillary dilation and exporting the image to an external device are not necessary. FoDi determines the fovea based on patient fixation, useful in poor macular definition. There are no investigations comparing DFA in fundus photography with the angle provided by the Spectralis tomograph...
At the posterior pole of a healthy eye, the optic disc is localized in a nasal and slightly superior position from the fovea. The angle subtended by these two landmarks is called ocular cycloposition and presents a large interindividual variability. Cycloposition out of the normal range is considered ocular torsion and indicates an anomalous rotation of the globe. It may be due to a primary cyclovertical strabismus, an extraocular muscle condition, an orbital disorder or an ocular surgery. In these cases, cycloposition provides essential information about the torsional component of the ocular deviation. In addition, it is considered a stable anatomic landmark in healthy eyes, used in refractive surgery and in retinal pathology analyses. The gold standard method for cycloposition evaluation is the quantification of the disc-fovea angle (DFA) in fundus photograph. It is determined by the inclination angle of a line connecting the fovea and the optic disc centre. Its value is around 7º downwards and it’s a repeatable and reproducible measurement. Authors disagree on interocular and sex differences, and about the relationship between age and cycloposition. The minimal detectable change (MDC) value is not described in relation to the DFA evaluation. It determines if a difference in repeated examinations may be considered as a real change or due to an instrumental error. The disadvantages of the technique include the need of pupillary dilation and the exportation of the fundus image to an external measure software. Besides, it requires the accurate manual determination of the fovea position, which is difficult in eyes with pathology affecting macular area. Cycloposition can also be qualitatively assessed by the inclination of temporal vascular arcades. These vessels travel at both sides of the optic disc-fovea axis and rotate when ocular torsion exists. The authors Parsa and Kumar described a method for quantifying this inclination. It may be a valuable tool when there is no proper location of the fovea and it has not been correlated with the gold standard. Finally, the built-in software of the Spectralis tomograph named FoDi (fovea-to-disc alignment) provides a semi-automatic measurement of the DFA. Pupillary dilation and exporting the image to an external device are not necessary. FoDi determines the fovea based on patient fixation, useful in poor macular definition. There are no investigations comparing DFA in fundus photography with the angle provided by the Spectralis tomograph...
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Tesis de la Universidad Complutense de Madrid, Facultad de Óptica y Optometría, leída el 18/11/2019