Typical and atypical ocular accommodation and convergence characteristics and relationships over the lifespan.
Lead Research Organisation:
University of Reading
Department Name: Sch of Psychology and Clinical Lang Sci
Abstract
Accommodation (focusing the eyes to clear blurred near images) and vergence (turning the eyes inwards to look at near objects) usually occur together automatically. If accommodation and vergence are disordered, blurred vision, double vision, reading difficulties and eye strain occur. In children, serious consequences such as squint, long or short sight can permanently damage eyesight if not treated correctly. These are common causes of referral to hospital and community eyecare services, but treatments are frequently poorly targeted, especially in community services.
Dr Anna Horwood will study 1) Premature infant development and extend studies into adolescents and typical ageing adults; 2) How much traditional treatment methods rely on true treatment, in comparison to practice / placebo effects; 3) How the visual system adapts to sudden or gradual changes in demand such as occur with new spectacles or presbyopia (the natural decline in accommodation that occurs with age). By understanding how commonly used, simple treatments act we will be able to target them better and so save time and resources. We will also collaborate with a commercial manufacturer of child vision screening equipment to develop simple and effective methods of measuring eye position at the same time as refraction (focus).
Dr Anna Horwood will study 1) Premature infant development and extend studies into adolescents and typical ageing adults; 2) How much traditional treatment methods rely on true treatment, in comparison to practice / placebo effects; 3) How the visual system adapts to sudden or gradual changes in demand such as occur with new spectacles or presbyopia (the natural decline in accommodation that occurs with age). By understanding how commonly used, simple treatments act we will be able to target them better and so save time and resources. We will also collaborate with a commercial manufacturer of child vision screening equipment to develop simple and effective methods of measuring eye position at the same time as refraction (focus).
Technical Summary
Ocular vergence (inward rotation of each eye to look at near objects) and accommodation (focusing of the lens) are fundamental to near vision and are closely associated with refractive error (long- and short-sight), presbyopia (deterioration of focusing for close work with age), strabismus (squint), anisometropia (unequal strength of long or short sightedness in each eye) asthenopia (eye strain) and reading difficulties, so can affect most of the population at some time in their life. Difficulties with vergence and accommodation are usually managed by orthoptists and optometrists but, especially in the community, treatments are often offered that are inappropriate, unnecessary, ineffective or even damaging. This results from a lack of evidence of the typical developmental progression and poor knowledge of the mode of action of treatments.
This research will extend studies at the Infant Vision Laboratory in Reading on the stimuli which drive accommodation, vergence, and their inter-relationships. I will study typical natural history over the wider lifespan, identify how established traditional treatments act, and so help develop evidence-based clinical assessment and treatment methods. Current research into treatments has not separated placebo, practice and treatment effects and has led to considerable disagreement between professional groups (ophthalmologists, mainstream optometrists, behavioural optometrists and orthoptists). In the proposed studies:
We will further adapt our laboratory to measure objective responses more efficiently. We will work with the commercial company that manufactures part of our equipment to develop and improve assessment of ocular alignment simultaneously with refraction. This will help develop clinical equipment to assess eye position in pre-verbal children, patients with unilateral poor vision, and in screening contexts.
Lifespan studies will add premature infants, adolescent, pre-presbyopic, and presbyopic adults to our published infant, child and young adult data.
Clinical studies will look at how the accommodative and vergence systems adapt to sudden and gradual changes in demand as occur with anisometropia, at the time of strabismus surgery or with new spectacle corrections and monovision contact lenses (one near and one distance correction), which have not been studied before. We will compare different methods of training vergence and accommodation to identify and quantify placebo, practice and treatment effects and so refine effective treatments. This is a poorly researched area of traditional vision science, often combined and confused with alternative therapies with little evidence base. By understanding how treatments act, we will be able to target primary, secondary and tertiary eyecare services more effectively.
This research will extend studies at the Infant Vision Laboratory in Reading on the stimuli which drive accommodation, vergence, and their inter-relationships. I will study typical natural history over the wider lifespan, identify how established traditional treatments act, and so help develop evidence-based clinical assessment and treatment methods. Current research into treatments has not separated placebo, practice and treatment effects and has led to considerable disagreement between professional groups (ophthalmologists, mainstream optometrists, behavioural optometrists and orthoptists). In the proposed studies:
We will further adapt our laboratory to measure objective responses more efficiently. We will work with the commercial company that manufactures part of our equipment to develop and improve assessment of ocular alignment simultaneously with refraction. This will help develop clinical equipment to assess eye position in pre-verbal children, patients with unilateral poor vision, and in screening contexts.
Lifespan studies will add premature infants, adolescent, pre-presbyopic, and presbyopic adults to our published infant, child and young adult data.
Clinical studies will look at how the accommodative and vergence systems adapt to sudden and gradual changes in demand as occur with anisometropia, at the time of strabismus surgery or with new spectacle corrections and monovision contact lenses (one near and one distance correction), which have not been studied before. We will compare different methods of training vergence and accommodation to identify and quantify placebo, practice and treatment effects and so refine effective treatments. This is a poorly researched area of traditional vision science, often combined and confused with alternative therapies with little evidence base. By understanding how treatments act, we will be able to target primary, secondary and tertiary eyecare services more effectively.