Depth-of-Focus and its Association with the Spherical Aberration Sign. A Ray-Tracing Analysis

Abstract

PURPOSE: To investigate the relationship between the sign of spherical aberration (SA) and the corresponding depth-of-focus (DoF) values around best focus, at three different spatial frequencies (SF). Additionally, to study the influence of the Stiles-Crawford effect (SCE) on DoF. METHODS: We modeled schematic eyes having a range of SA values, C (4, 0), from -0.20 to 0.20 μm, at 6 mm pupil, in a ray-tracing software (Zemax). The through-focus optical performance was obtained via Modulation Transfer Function (MTF) calculations using thin paraxial lenses in-front of the model eye, from -2.00 to+2.00 D in 0.05D steps. Through-focus full-width (defocus) occurring at the half maximum of MTF value was considered as DoF, in diopters. RESULTS: For the low-SF configuration, +SA and -SA results were close to being mirror symmetries of one another. However, for midand high-SF targets, in the SA range spanning from -0.15 to 0.15 μm, models of equal SA magnitude but opposite sign produced similar DoF measures, but those with SA more negative than -0.15 μm showed marginally higher DoF than their positive counterparts. The SCE improved DoF for low SF (10 cycles/mm), while for mid and higher SF (>30 cycles/mm) mixed results were observed. CONCLUSIONS: As regards presbyopic-correction strategies that use deliberately induced aberrations to increase the depth of focus, the current study suggests that both positive and negative SA have equal potential. However, practical considerations will probably limit the useful DoF achievable through the utilization of SCE in presbyopes. for reference to a contemporary record detailing refractive history. RESUMEN OBJETIVO:Investigar, para tres frecuencias espaciales (FE) distintas, la relación entre el signo de la aberración esférica (AE) y la correspondiente profundidad de foco (PdF) alrededor del mejor foco. Además, se estudiará cómo afecta el efecto Stiles-Crawford (ESC) a la PdF. MÉTODOS: Hemos utilizado un modelo de ojo esquemático con distintos valores de aberración esférica (AE) (C (4, 0) comprendido entre 0.20 y 0.20 μm, para un diámetro de pupila de 6 mm) para investigar la relación que existe entre el signo de la AE y la correspondiente profundidad de foco (PdF) alrededor del mejor foco para tres frecuencias espaciales (FE) distintas. También se estudió la influencia del efecto Stiles-Crawford (ESC). RESULTADOS: Para FE bajas, los resultados correspondientes a +AE y AE presentan simetría especular. Sin embargo, para FE medias y altas, y en el intervalo de AE comprendido entre 0.15 y 0.15 μm, modelos de igual AE (en módulo) pero distinto signo da lugar a valores de PdF similares, pero para valores de AE más negativos que 0.15 μm se obtuvieron PdF ligeramente más altas que para un valor positivo equivalente de AE. El ESC hace que aumente la PdF para FE bajas (10 ciclos/mm), mientras que para FE medias y altas (>30 ciclos/mm) se observan resultados variados. CONCLUSIONES: En lo que respecta a las estrategias de corrección de la presbicia basadas en la inducción deliberada de ...

In Vitro Aberrometric Assessment of a Multifocal Intraocular Lens and Two Extended Depth of Focus IOLs

“…One solution to this problem is based on the control of HOAs (high order aberrations). HOAs may influence the quality of vision, and also they have been recently shown that they may increase the depth of focus of the eye and therefore provide a good functional intermediate and near vision [ 3 , 4 ]. Moreover, the wavefront analysis has been widely used to detect the effects of lower and higher order aberrations and their contribution to the optical quality in both in vitro and in vivo sets [ 5 ].…”

Modified Monovision With Spherical Aberration to Improve Presbyopic Through-Focus Visual Performance

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Designing multifocal corneal models to correct presbyopia by laser ablation

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