Research

Human ocular accommodation (the auto-focus mechanism of the human eye)is achieved primarily by a change in the power of lens inside the eye. The change in the lens power is brought about the constriction of the ciliary muscle in response to parasympathetic innervation sent the brain. As we age, our accommodative ability progressively deteriorates primarily due to the inability of the lens to change shape. The progressive deterioration in the focusing ability with aging is termed as 'presbyopia'. While we have a fairly good understanding of the different bio-mechanical structures involved in accommodation and how their properties change with age, our knowledge of the neural control of accommodation is still limited. As a graduate student, I investigated various aspects of the neural control of accommodation and how the neural control changed with age. A second-order feedback control model of accommodation was developed based on the static and dynamic characteristics of accomodation and based on already observed neural firing patterns that are related to accommodation responses. Through these empirical and modeling exercises, I realized that the accommodative system in humans does not work with machine-like properties but it adopts different control strategies in order to optimize different response characteristics. These control strategies are likely to change with viewing conditions, practice and with age.