Corneo-pterygium total area measurements utilising image analysis method / Mediciones del área total de pterigium corneal utilizando un método de análisis de imagen

PURPOSE: To describe an objective method to accurately quantify corneo-pterygium total area (CPTA) by utilising image analysis method and to evaluate its association with corneal astigmatism (CA). METHODS: 120 primary pterygium participants were selected from patients who visited an ophthalmology clinic. We adopted image analysis software in calculating the size of invading pterygium to the cornea. The marking of the calculated area was done manually, and the total area size was measured in pixel. The computed area is defined as the area from the apex of pterygium to the limbal-corneal border. Then, from the pixel, it was transformed into a percentage (%), which represents the CPTA relative to the entire corneal surface area. Intra- and inter-observer reliability testing were performed by repeating the tracing process twice with a different sequence of images at least one (1) month apart. Intraclass correlation (ICC) and scatter plot were used to describe the reliability of measurement. RESULTS: The overall mean (N = 120) of CPTA was 45.26 ± 13.51% (CI: 42.38-48.36). Reliability for region of interest (ROI) demarcation of CPTA were excellent with intra and inter-agreement of 0.995 (95% CI, 0.994-0.998; P < 0.001) and 0.994 (95% CI, 0.992-0.997; P < 0.001) respectively. The new method was positively associated with corneal astigmatism (P < 0.01). This method was able to predict 37% of the variance in CA compared to 21% using standard method. CONCLUSIONS: Image analysis method is useful, reliable and practical in the clinical setting to objectively quantify actual pterygium size, shapes and its effects on the anterior corneal curvature

OBJETIVO: Describir un método objetivo para cuantificar con precisión el área total corneal invadida por pterigium (CPTA) utilizando un método de análisis de imagen evaluando su asociación con el astigmatismo de la córnea (AC). MÉTODOS: Se seleccionaron 120 participantes con pterigium primario de entre los pacientes que acudieron a la clínica oftalmológica. Utilizamos un software de análisis de imagen para calcular el tamaño del pterigión invasivo hacia la córnea. La marcación del área calculada se realizó manualmente, midiéndose en píxeles el tamaño del área total. El área computada se define como el área desde el ápex del pterigium al borde del limbo corneal. A continuación, a partir del análisis de pixels, se transformó en un porcentaje (%), que representa el CPTA relativo al área total de la superficie de la córnea. Se realizaron pruebas de fiabilidad Intra- e inter-observador mediante un proceso, de doble repetición, con una secuencia de imágenes diferente, con separación de un (1) mes como mínimo. Se utilizaron la correlación intra-clase (ICC) y el gráfico de dispersión para describir la fiabilidad de las mediciones. RESULTADOS: La media global (N = 120) de CPTA fue 45,26 ± 13,51% (IC: 42,38-48,36). La fiabilidad para la demarcación de la región de interés (ROI) de CPTA fue excelente con intra e inter-acuerdo de 0,995 (95% IC, 0,994-0,998; P < 0,001) y 0,994 (95% IC, 0,992-0,997; P < 0,001) respectivamente. El nuevo método se asoció positivamente al astigmatismo de la córnea (p < 0,01). Este método fue capaz de predecir el 37% de la varianza de AC, en comparación con el 21% utilizando el método estándar. CONCLUSIONES: El método de análisis de imagen descrito es útil, fiable y práctico en el entorno clínico, para cuantificar objetivamente el tamaño real del pterigium, así como sus formas y efectos sobre la curvatura anterior de la córnea

Corneo-pterygium total area measurements utilising image analysis method.

PURPOSE: To describe an objective method to accurately quantify corneo-pterygium total area (CPTA) by utilising image analysis method and to evaluate its association with corneal astigmatism (CA). METHODS: 120 primary pterygium participants were selected from patients who visited an ophthalmology clinic. We adopted image analysis software in calculating the size of invading pterygium to the cornea. The marking of the calculated area was done manually, and the total area size was measured in pixel. The computed area is defined as the area from the apex of pterygium to the limbal-corneal border. Then, from the pixel, it was transformed into a percentage (%), which represents the CPTA relative to the entire corneal surface area. Intra- and inter-observer reliability testing were performed by repeating the tracing process twice with a different sequence of images at least one (1) month apart. Intraclass correlation (ICC) and scatter plot were used to describe the reliability of measurement. RESULTS: The overall mean (N=120) of CPTA was 45.26±13.51% (CI: 42.38-48.36). Reliability for region of interest (ROI) demarcation of CPTA were excellent with intra and inter-agreement of 0.995 (95% CI, 0.994-0.998; P<0.001) and 0.994 (95% CI, 0.992-0.997; P<0.001) respectively. The new method was positively associated with corneal astigmatism (P<0.01). This method was able to predict 37% of the variance in CA compared to 21% using standard method. CONCLUSIONS: Image analysis method is useful, reliable and practical in the clinical setting to objectively quantify actual pterygium size, shapes and its effects on the anterior corneal curvature.