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Abstract(s)
Introdução: A pseudofaquia é uma condição na qual um indivíduo foi submetido a uma cirurgia
para remoção do cristalino, sendo este substituído por uma lente intraocular de câmara
posterior. No entanto, os olhos pseudofáquicos perdem a capacidade de acomodar devido ao
facto da lente intraocular não alterar a sua curvatura como resposta à ação do músculo ciliar
ao contrário do que acontece com o cristalino, especialmente em indivíduos mais jovens.
Contudo, existem alguns indivíduos pseudofáquicos que apresentam bons níveis de visão de
perto após o implante de lentes intraoculares monofocais, fenómeno este chamado de
pseudoacomodação, e assume-se que o diâmetro pupilar é uma das principais características
responsáveis.
Objetivo: O objetivo deste estudo consistiu em medir, analisar e modelar a variação do
diâmetro pupilar em função da distância ao estímulo visual (vergência do estímulo) num grupo
de indivíduos pseudofáquicos implantados bilateralmente com uma lente intraocular
monofocal.
Métodos: Participaram neste estudo 59 indivíduos pseudofáquicos com erro refrativo não
compensado, com idades compreendidas entre os 40 e os 90 anos, que foram recrutados durante
um exame ocular de rotina. Os diâmetros pupilares de ambos os olhos foram medidos através
de um sistema de Eye-Tracker binocular durante a observação de um estímulo visual (cruz de
Malta) às distâncias de observação de 300, 100, 66, 50, 40 e 33 cm e que correspondem às
vergências de 0.33, 1.00, 1.50, 2.00, 2.50, 3.00 D. Estas medições foram realizadas com a área
iluminada na retina constante e o fluxo luminoso no plano corneal também constante.
Resultados: Um estudo comparativo entre os dois olhos (OD e OS) demonstrou que não existem
diferenças estatisticamente significativas entre os diâmetros pupilares de longe (p = 0.430) e
que a variação dos diâmetros pupilares ocorre de igual forma nos dois olhos (p = 0.997).
Analisando o OD de todos os participantes, verificou-se um diâmetro pupilar médio de 4.44 mm
para a vergência de 0.33 D e um diâmetro pupilar médio de 3.84 mm para a vergência de 3.00
D, mostrando assim uma miose de cerca 0.60 mm com o aumento da vergência. Uma análise de
agrupamento hierárquico revelou a existência de 3 grupos na amostra. O grupo 1 apresenta
diâmetro pupilar médio pequeno (4.09 mm) com uma miose média pequena ( -0.18 mm/D), o
grupo 2 apresenta diâmetro pupilar médio grande (5.47 mm) com miose média grande (-0.58
mm/D), e por sua vez o grupo 3 apresenta diâmetro pupilar médio grande (5.89 mm) com uma
miose quase inexistente (-0.11 mm/D). Foi também encontrada uma curva de ajuste linear
(declive e ordenada na origem) para cada grupo de participantes que modela a resposta de
cada grupo à vergência do estímulo visual.
Conclusões: Concluiu-se que os diâmetros pupilares variam de forma significativa com o
aumento da vergência do estímulo visual (p < 0.001). Através da análise por grupos, verifica-se
que a grande proporção dos participantes está inserida no grupo 1, sendo que este se caracteriza por ter diâmetros pupilares pequenos combinados com uma miose igualmente
pequena resultante do aumento da vergência do estímulo visual.
Concluiu-se ainda que um modelo de regressão linear pode ser usado para descrever a variação
do diâmetro pupilar em função da vergência do estímulo visual. Isto possibilita assim uma forma
simples de estimar o diâmetro pupilar para distâncias de observação comuns, o que é
importante uma vez que as relações existentes entre o diâmetro pupilar e a posição do estímulo
visual podem ser usadas para prever o desempenho visual de olhos pseudofáquicos.
Introduction: Pseudophakia is a condition in which an individual has undergone surgery to remove the lens, which is replaced by a posterior chamber intraocular lens. However, pseudophakic eyes lose the ability to accommodate because the intraocular lens does not change its curvature in response to ciliary muscle action as opposed to the lens, especially in younger individuals. However, there are some pseudophakic individuals who present good levels of vision from far and near after the implantation of monofocal intraocular lenses, a phenomenon known as pseudoaccommodation, and it is assumed that the pupillary diameter is one of the main responsible characteristics. Objective: The objective of this study was to measure, analyze and model the variation of pupillary diameter as a function of distance to the visual stimulus (stimulus vergence) in a group of pseudophakic individuals implanted bilaterally with a monofocal intraocular lens. Methods: 59 pseudophakic individuals with uncompensated refractive error with ages between 40 to 90 years were recruited during a routine ocular examination. The pupillary diameters of both eyes were measured through a binocular Eye-Tracker system during observation of a visual stimulus (Maltese cross) at the observation distances of 300, 100, 66, 50, 40 and 33 cm and corresponding to the vergencies of 0.33, 1.00, 1.50, 2.00, 2.50, 3.00 D. These measurements were performed with the illuminated area in the constant retina and the luminous flux in the corneal plane also constant. Results: A comparative study between two eyes (OD and OS) showed that there are no statistically significant differences between farrowing diameters (p = 0.430) and pupillary diameters vary in both eyes (p = 0.997). Analyzing the OD of all participants, a mean pupillary diameter of 4.44 mm was found for the vergency of 0.33 D and a mean pupil diameter of 3.84 mm for the vergency of 3.00 D, thus showing a miosis of about 0.60 mm with the increase of the vergence. A hierarchical grouping analysis revealed the existence of 3 groups in the sample. Group 1 had a small mean pupillary diameter (4.09 mm) with a small mean miosis ( -0.18 mm / D), and group 2 had a large mean pupillary diameter (5.47 mm) with a large mean miosis (-0.58 mm / D), and Group 3 has a large mean pupillary diameter (5.89 mm) with an almost nonexistent miosis (-0.11 mm / D). A linear fit curve (slope and order at origin) was also found for each group of participants that models the response of each group to the visual stimulus vergence. Conclusions: It was concluded that the pupillary diameters vary significantly with the increase of vergence of the visual stimulus (p <0.001). Through the analysis by groups, it is verified that the great proportion of the participants in group 1, which is characterized by small pupillary diameters combined with an equally small miose resulting from the increase of vergence of the visual stimulus. It was also concluded that a linear regression model can be used to describe the pupil diameter variation as a function of visual stimulus vergence. This allows a simple way of estimating the pupillary diameter for common observation distances, which is important since the relationships between the pupillary diameter and the position of the visual stimulus can be used to predict the visual performance of pseudophakic eyes.
Introduction: Pseudophakia is a condition in which an individual has undergone surgery to remove the lens, which is replaced by a posterior chamber intraocular lens. However, pseudophakic eyes lose the ability to accommodate because the intraocular lens does not change its curvature in response to ciliary muscle action as opposed to the lens, especially in younger individuals. However, there are some pseudophakic individuals who present good levels of vision from far and near after the implantation of monofocal intraocular lenses, a phenomenon known as pseudoaccommodation, and it is assumed that the pupillary diameter is one of the main responsible characteristics. Objective: The objective of this study was to measure, analyze and model the variation of pupillary diameter as a function of distance to the visual stimulus (stimulus vergence) in a group of pseudophakic individuals implanted bilaterally with a monofocal intraocular lens. Methods: 59 pseudophakic individuals with uncompensated refractive error with ages between 40 to 90 years were recruited during a routine ocular examination. The pupillary diameters of both eyes were measured through a binocular Eye-Tracker system during observation of a visual stimulus (Maltese cross) at the observation distances of 300, 100, 66, 50, 40 and 33 cm and corresponding to the vergencies of 0.33, 1.00, 1.50, 2.00, 2.50, 3.00 D. These measurements were performed with the illuminated area in the constant retina and the luminous flux in the corneal plane also constant. Results: A comparative study between two eyes (OD and OS) showed that there are no statistically significant differences between farrowing diameters (p = 0.430) and pupillary diameters vary in both eyes (p = 0.997). Analyzing the OD of all participants, a mean pupillary diameter of 4.44 mm was found for the vergency of 0.33 D and a mean pupil diameter of 3.84 mm for the vergency of 3.00 D, thus showing a miosis of about 0.60 mm with the increase of the vergence. A hierarchical grouping analysis revealed the existence of 3 groups in the sample. Group 1 had a small mean pupillary diameter (4.09 mm) with a small mean miosis ( -0.18 mm / D), and group 2 had a large mean pupillary diameter (5.47 mm) with a large mean miosis (-0.58 mm / D), and Group 3 has a large mean pupillary diameter (5.89 mm) with an almost nonexistent miosis (-0.11 mm / D). A linear fit curve (slope and order at origin) was also found for each group of participants that models the response of each group to the visual stimulus vergence. Conclusions: It was concluded that the pupillary diameters vary significantly with the increase of vergence of the visual stimulus (p <0.001). Through the analysis by groups, it is verified that the great proportion of the participants in group 1, which is characterized by small pupillary diameters combined with an equally small miose resulting from the increase of vergence of the visual stimulus. It was also concluded that a linear regression model can be used to describe the pupil diameter variation as a function of visual stimulus vergence. This allows a simple way of estimating the pupillary diameter for common observation distances, which is important since the relationships between the pupillary diameter and the position of the visual stimulus can be used to predict the visual performance of pseudophakic eyes.
Description
Keywords
Miose Profundidade de Foco Pseudoacomodação Pseudofaquia Pupila