Caracterización clínica y epidemiológica del queratocono / Clinical and epidemiological characterization of keratoconus

OBJETIVO: describir las características clínicas y epidemiológicas del queratocono en el Instituto Cubano de Oftalmología "Ramón Pando Ferrer". MÉTODOS: se realizó un estudio descriptivo en 72 pacientes (128 ojos) con queratocono, atendidos entre enero y diciembre de 2012, para identificar las enfermedades generales y oculares, tiempo de uso de lentes de contacto, manifestaciones clínicas, tipo de astigmatismo, poder queratométrico, espesor de la córnea central, topografía y microscopia confocal. RESULTADOS: el 50 % de los pacientes presentó disminución lenta y progresiva de la visión, con significativa ausencia de enfermedades generales. Fueron significativos (p< 0,05) el uso prolongado de lentes de contacto (67 %), la mejoría de la agudeza visual con corrección y el astigmatismo miópico compuesto (85,2 %). Predominó la disminución del espesor de la córnea central (493,2 µm). Los intervalos de poder queratométrico de la córnea central fueron igualmente representados (p= 0,211). Por topografía predominó el astigmatismo irregular (99,2 %) y el cono central (87,5 %). La microscopia confocal reflejó alteraciones en casi todas las capas de la córnea. CONCLUSIONES: la queratoconjuntivitis alérgica es la enfermedad ocular más frecuentemente asociada al queratocono. Posee un patrón topográfico de astigmatismo irregular con cono central y agudeza visual con corrección, con lentes de contacto de 0,6. La microscopia confocal constituye una herramienta valiosa en el diagnóstico del queratocono.

OBJECTIVE: to describe the clinical and epidemiological characteristics of keratoconus treated at "Ramón Pando Ferrer" Cuban Institute of Ophthalmology. METHODS: a descriptive study was conducted in 72 patients (128 eyes) with keratoconus, from January to December 2012, to identify general and ocular diseases, length of time wearing the contact lenses, clinical features, type of astigmatism, keratometric power and central corneal thickness, topography and confocal microscopy. RESULTS: in the group, 50 % had slow gradual decrease of vision, with no significant medical illnesses. Wearing contact lenses for a long time (67 %), the improvement of visual acuity with correction and myopic compound astigmatism (85,2 %) were significant (p< 0,05). Thinning of the central cornea (493,2 microns) predominated. Keratometric power intervals of the central cornea were equally represented (p= 0,211). The irregular astigmatism (99,2 %) and the central cone (87,5 %) prevailed in terms of topography. Confocal microscopy changes in almost all the corneal layers. CONCLUSIONS: Allergic keratoconjunctivitis is the most associated eye disease. It has topographic pattern of irregular astigmatism with central cone and corrected visual acuity, with 0,6 contact lenses. Confocal microscopy is a valuable tool in the diagnosis of keratoconus.

El análisis estadístico de los datos de la refracción / Statistical analysis of refractive data

OBJETIVO: describir la técnica de la descomposición en coordenadas cartesianas para el análisis estadístico de datos de la refracción. Proponer y ejemplificar una metodología. MÉTODOS: se realizó una revisión de la técnica de la descomposición cartesiana para el análisis estadístico de los datos de la refracción. Se emplearon datos de ejemplo para describir el algoritmo. En el análisis estadístico se realizaron pruebas de hipótesis con el uso del estadígrafo t de Student y T2 de Hotelling, para los datos univariados y multivariados, respectivamente. RESULTADOS: se describe y ejemplifica un método que transformó la información de un esferocilindro a un punto en un espacio tridimensional, mediante la conversión a 3 componentes independientes, ortogonales de un sistema de coordenadas cartesianas. A diferencia de otros métodos matemáticamente equivalentes, este procedimiento produjo 3 componentes con significación óptica para describir la esfera y el cilindro: equivalente esférico y 2 cilindros cruzados. Se eliminó el carácter direccional de los datos. En este sistema de coordenadas cartesianas están definidas las operaciones propias de los números reales: adición, multiplicación por escalares, entre otros que permiten con la ayuda de matrices de 3 x 1, la realización de análisis estadísticos y el cálculo de medidas de uso clínico como variación de astigmatismo, astigmatismo inducido, sorpresa refractiva o error del procedimiento refractivo, astigmatismo medio, comparaciones de medias de poblaciones, correlaciones, entre otras. CONCLUSIONES: la representación cartesiana de la refracción es una notación no polar que permite la representación gráfica y el análisis estadístico de los datos de individuos y de la población.

OBJECTIVE: to describe the decomposition technique into Cartesian coordinates for the statistical analysis of refractive data and the proposal and exemplification of a methodology. METHOD: the Cartesian decomposition technique for the statistical analysis of refractive data was reviewed. Sample data were used to exemplify the algorithm. In the statistical analysis, summary measures and hypothesis tests were applied by using Student's t statistic and Hotelling's T2 for univariate and multivariate data, respectively. RESULTS: a method that allows transforming data from one spherocylinder into a point in the three-dimensional space was described and exemplified, by means of the conversion of refraction into three independent orthogonal components of a Cartesian coordinate system. Unlike other mathematically equivalent methods, this technique brought about three components with optical significance to describe the sphere and the cylinder (the spherical equivalent and two Jackson crossed cylinders), thus eliminating the directional characteristics of data. In this system of Cartesian coordinates, the operations in real numbers are defined (addition, multiplication by scalars, among others), allowing mathematical and statistical analysis based on 3 x 1 matrices. The most common clinical measures that can be estimated with such a method are astigmatism variation, induced astigmatism, refractive surprise or error of the refractive procedure, mean astigmatism, comparison of population means, correlations, etc. CONCLUSIONS: the Cartesian representation of refraction is a non-polar notation that facilitates the graphical representation and statistical analysis of individual and population data.

Postoperative Astigmatic Outcomes Based on the Haptic Axis of Intraocular Lenses Inserted in Cataract Surgery

PURPOSE: This study was conducted to compare post-operative astigmatic outcomes of two groups, with-the-rule (WTR) and against-the-rule (ATR) astigmatism patients, according to the haptic axis of intraocular lenses (IOLs) inserted in cataract surgery. METHODS: Seventy-two eyes with WTR astigmatism and 79 eyes with ATR astigmatism had cataract surgery through a clear corneal temporal incision. These two groups of eyes were then each divided into 2 groups based on whether the haptic axis of the inserted IOL was at 180degrees or 90degrees. For ATR patients, the outcomes were analyzed according to the three types of IOLs. RESULTS: There was no difference in corneal astigmatism, but WTR patients with a 180degrees haptic axis of the inserted IOL and ATR patients with a 90degrees hepatic axis of the inserted IOL had a significant decrease in postoperative refractive astigmatism (p < 0.05). The changes in ATR astigmatism according to the IOL type were more effective in single-piece acrylic IOLs than in the three-piece polymethylmethacrylate haptic IOL group. CONCLUSIONS: Insertion of the IOL at the 180degrees haptic axis in WTR patients and at 90degrees in ATR patients during cataract surgery may have an effect in reducing pre-existing astigmatism. This observed effect was not consistent among the different types of IOLs.

Design, construction and test of a surgical keratometer / Desenho, construçäo e teste de um ceratômetro cirúrgico

Objetivos: desenhar, construir e testar um ceratômetro cirúrgico simples e de baixo custo. Métodos: para a montagem do aparelho foram utilizados os princípios descritos por Plácido da Costa. Um anel circular iluminado foi construido e acoplado a um microscópio cirúrgico. O sistema de zoom do microscópio era acionado pelo observador, que deveria aumentar ou diminuir o tamanho da imagem do anel, produzida pela superfície de teste, até a coincidência com uma retícula circular, presente na lente ocular do microscópio. Uma escala graduada foi montada para a obtençäo de valores numéricos. A localizaçäo dos meridianos também foi realizada. Resultados: o aparelho apresenta

Incidence of astigmatism in Alexandria population

Astigmatism was studied in 1000 patients [500 Males and 500 females] using Nidek [AR 1100] Autorefractometer. The total incidence off astigmatism was found to be 95.4%. The incidence of significant astigmatism [above 0.5 diopters] was 56.5%. There was no statistically significant difference between males and females. The most common type of astigmatism was found to be compound myopic astigmatism was found to be compound myopic astigmatism [55.07%]