Developmental Dynamics of Accommodation and Convergence in the Visual System

Priyanka Roy

Abstract: Aim: This review aims to explore current research on how the visual functions of convergence (eye alignment) and accommodation (focusing) develop in early life. These two visual processes are essential for clear, single vision with both eyes working together. If their development is disrupted, it can lead to vision problems such as strabismus (eye turn), accommodative disorders, and possibly interfere with the natural process of the eye growing towards correct focus (known as emmetropisation). Method: The review examines the unique challenges of studying these visual functions in infants, who cannot communicate or follow instructions like adults. As a result, researchers have had to use different approaches compared to adult studies. The review then discusses current findings on how these visual abilities develop and how closely they are connected in early life. Results: Accommodation begins with a default nearsighted (myopic) state in newborns, but becomes more accurate and adult - like by around 4 months of age. Vergence (the ability to align both eyes) also improves after this age but is seen to begin even earlier?before infants can use binocular disparity (a key depth perception cue). The early presence of vergence suggests alternative developmental mechanisms, which are explored in this review. Interestingly, the coordination between accommodation and vergence in infants shows more variation than what is typically reported in adults. However, this difference may not be entirely due to developmental immaturity?it could also stem from how these functions are measured in infants versus adults. Conclusions: Infant visual responses are marked by flexibility and variability. Rather than being signs of dysfunction, these may reflect a natural strategy that helps infants build a strong and adaptable binocular vision system as they grow. Studying how infants use visual cues may also offer valuable insights into the causes of conditions like strabismus and refractive errors.

Keywords: Accommodation, Development, Emmetropisation, Infant Vision, Vergence, AC/A ratio, CA/A ratio, BSV, Refractive errors