Straylight As The Result Of Refractive Correction.

PURPOSE: To investigate the effect of refractive correction on straylight. PATIENTS AND METHODS: Straylight values were measured with the C-Quant (Oculus Optikgeräte, GmbH, Wetzlar, Germany) in 1) near-emmetropic eyes (n=30) with various negative powered refractive lenses and in 2) myopic eyes (n=30) corrected with prescribed eyeglasses and contact lenses. The straylight measurements in each group were compared in the different conditions. RESULTS: In the near-emmetropic group, a significant effect (p<0.001) of each added negative diopter was found to increase straylight values with 0.006 log-units. In the second group, no significant correlation with type of correcting lens was found on straylight values. CONCLUSION: Refractive correction with high minus power (contact) lenses result in subtle increase of straylight values. These changes are relatively small and do not lead to visual disability in a clinical setting.

Glistening Formation and Light Scattering in Six Hydrophobic-Acrylic Intraocular Lenses.

PURPOSE: To study the glistening formation in various hydrophobic-acrylic intraocular lens (IOL) models, and to evaluate the effect of glistenings on light scattering in these IOLs. DESIGN: Laboratory investigation. METHODS: The susceptibility of the hydrophobic-acrylic material to develop glistenings was evaluated in 6 IOL models. Accelerated lens aging was induced by immersing the IOLs in a solution at 45 C for 24 hours and cooled to 37 C for 2.5 hours. Light microscopy and image acquisition were performed. Glistening statistics-that is, microvacuoles' (MV) number and size-were derived from image analysis. Light scattering was measured using a clinical device featuring an adaptation for in vitro IOL assessment. RESULTS: The number of glistenings differed among the studied IOLs and ranged from 0 to 3532 MV/mm2. In 1 model, glistenings were found only at the periphery, with diffuse light scattering observed centrally despite the absence of microvacuoles. The mean size of glistenings ranged from 5.2 to 10.2 µm. The mean straylight parameter of the IOLs increased from 0.6 to 5.0 deg2/sr after accelerated aging. Straylight elevation demonstrated a proportional relationship with the glistening number. CONCLUSIONS: We showed that hydrophobic-acrylic lenses differ in their resistance to glistenings, as one group proved to be glistening-free, but the other models revealed varying grades of glistenings. Moreover, we demonstrated that the presence of glistenings results in increased straylight, and that straylight proportionally depends on the glistenings number irrespective of the IOL model. However, more research is needed to confirm that the relationship we found holds for all hydrophobic-acrylic IOLs.

The significance of changes in pupil size during straylight measurement and with varying environmental illuminance / Importancia de los cambios del tamaño de la pupila durante la medición de la dispersión lumínica, con variación de iluminancia ambiental

Purpose: In this work, we investigated the pupillary conditions during straylight measurement, and the potential effect this might have on the measured straylight. Methods: Five young (26-29-years-old) and 15 older (50-68-years-old) individuals participated in this study. First, the pupil diameter of both eyes was measured at three room illuminances. Next, straylight was assessed at two room illuminances. Simultaneously, the change in pupil size of the fellow eye was registered by a camera. Results: Pupil size decreased with room illuminance and with age (both p < 0.05). The dependency of pupil size on age decreased as room illuminance increased (0.018 mm/year at 4 lux, 0.014 mm/year at 40 lux, and 0.008 mm/year at 400 lux illuminances). However, during straylight measurement, pupil sizes hardly differed between 4 and 40 lux illuminances. Respective pupil sizes corresponded with 399 and 451 lux adaptation on average. No statistically significant difference was found between the straylight under the two illuminances with average R2 = 0.85, p < 0.05. Conclusion: We conclude that the illuminance of the examination room during straylight assessment does not affect the outcome in normal eyes. In fact, under mesopic and scotopic conditions, the luminance of the test field is so much higher than that of the room so that it determines the pupil size. Regardless of the lighting level, straylight measured in a laboratory, is valid for photopic pupils at an adaptation level corresponding with about 400 lux room illuminance

Objetivo: En este trabajo investigamos las condiciones de la pupila durante la medición de la dispersión lumínica, así como el efecto potencial que ello podría tener sobre la dispersión lumínica medida. Métodos: En el estudio participaron cinco individuos jóvenes (de 26 a 29 años) y 15 mayores (de 50 a 68 años). En primer lugar, se midió el diámetro de la pupila de ambos ojos con tres iluminancias ambientales. A continuación, se evaluó la dispersión lumínica con dos iluminancias ambientales. De manera simultánea, se registró mediante una cámara el cambio del tamaño de la pupila del otro ojo. Resultados: El tamaño de la pupila se redujo con la iluminancia ambiental y la edad (p < 0,05 para ambos). La dependencia del tamaño de la pupila con la edad se redujo a medida que aumentaba la iluminancia ambiental (0,018 mm/año a iluminancias de 4 lux, 0,014 mm/año a 40 lux, y 0,008 mm/año a 400 lux). Sin embargo, durante la medición de la dispersión lumínica, los tamaños de la pupila difirieron escasamente entre iluminancias de 4 y 40 lux. Los tamaños de la pupila respectivos se correspondieron con una adaptación de 399 y 451 lux, de media. No se encontraron diferencias estadísticamente significativas entre la dispersión lumínica bajo las dos iluminancias y la media de R2 = 0,85, p < 0,05. Conclusión: Concluimos que la iluminancia de la sala de examen durante la valoración de la dispersión lumínica no afecta al resultado en ojos normales. De hecho, en condiciones mesópicas y fotópicas, la iluminancia del campo de prueba es muy superior a la de la sala, lo cual determina el tamaño de la pupila. Independientemente del nivel de iluminación, la dispersión lumínica medida en un laboratorio es válida para pupilas fotópicas a un nivel de adaptación correspondiente a una iluminancia ambiental de alrededor de 400 lux