Mathematical Modelling of the Depth-of-Field of the Eye

Abstract

The depth-of-field (DOFi) of the eye is an important feature for a precise refractive correction, for the determination of accommodation response of the eye and for its implication in the development of new presbyopia corrections. Although the optical factors that influence DOFi have been widely investigated, new techniques such adaptive optics systems and objective methods could help us to further understand other factors such us the ones produced by the neural part of the visual function. This work aimed to investigate some important factors influencing DOFi such as pupil size, optical aberrations, and neural factors, using new methodologies. Chapter 2 describes the development of an eye model able to predict the combined changes in pupil size and 4th-order spherical aberration (C40) with accommodation and age. Results showed a slight change in C40 with age and accommodation for natural pupils (2.92-3.58 mm). Chapters 3 and 4 tested the suitability of new objective methods to estimate the change in DOFi produced by induced aberrations or by accommodation. These objective methods were able to predict the changes in DOFi produced by induced aberrations, but not to predict subjective DOFi measurements or the effect of the accommodation function on DOFi. In Chapter 5, we used an adaptive optics system to quantify the effect of natural aberrations on DOFi and to control aberrations and study neural factors that influence DOFi. Natural aberrations explained a 21% of the DOFi of our subjects, and a two-way ANOVA revealed that the inter-individual differences in DOFi were mainly due to neural factors. Chapter 6 investigated the use of a psychophysical method that determines the internal noise and the sampling efficiency of the visual function to predict the influence of neural factors on DOFi. Nevertheless, while the internal noise (typically associated to optical factors) was significantly correlated with the DOFi of our subjects, sampling efficiency was not a good predictor of the influence of neural factors on DOFi. As a final conclusion, our results show that the influence of neural factors on DOFi should be taken into account when designing new presbyopia corrections, as these corrections may not have the same effect in all subjects.

Date of Award	31 Dec 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Ian Murray (Supervisor) & Hema Radhakrishnan (Supervisor)