Accommodative esotropia: relationship between accommodation and convergence.

This study investigated the change in corneal curvature and corneal wave-front aberrations with accommodation. The corneal curvature of the right eyes of 12 young adults was measured using a corneal topography system, while subjects fixated far (4.0 m) and near (0.2 m) targets with their left eyes. Convergence was controlled. Both the mean corneal radius at the vertex and the shape parameter significantly increased from the far to the near viewing condition. No significant change in root mean square of wave-front aberrations with accommodation was observed for the group, but there was individual variation in the change of wave-front aberration. A significant mean change for the group in both x-axis coma and spherical aberration was found. The change in corneal surface with accommodation suggests an increase in peripheral curvature with flattening at the vertex.

Accommodation, Ocular↗

PubMed2003

Can tonic accommodation predict surgical performance?

BACKGROUND: Pilots undergo many visual tests for both selection and assessment, and we know that there are many similarities between pilots and surgeons. Hence, it would not be unreasonable to bring similar visual tests into surgery. Tonic accommodation (TA) is a stable parameter that is adopted by the eye in the absence of any stimulation. Over recent years, surgery has undergone change from traditional open surgery to minimally invasive procedures, bringing many advantages. However, not every surgeon has the ability to perform under conditions where the operative field is represented on a flat monitor. METHOD: We determined the TA values in medical students and then correlated this with their performance on a virtual reality surgical simulator. RESULTS: We found that TA values predicted the number of errors made with the dominant hand, accounting for 27% of the variance. CONCLUSION: The data suggest that TA may play a role in the individual differences that are noted when surgeons perform laparoscopic surgery. Further studies are needed to evaluate the exact role of TA in surgical performance.

Accommodation, Ocular↗

PubMed2003

Presbyopia among normal individuals.

BACKGROUND: To define ocular variables that might affect the need for early use of reading glasses. METHODS: A retrospective, non-randomized clinical trial was conducted at an aero-medical center. The charts of 100 healthy male pilots who suffered from presbyopia were reviewed. All subjects had undergone a complete eye examination every year for 30 years. Ocular parameters measured at the ages of 20, 30, 40, 45, and 50 years were recorded. Individuals were divided into two groups: those who needed reading glasses at the age of 45 years or earlier (group 1) and those who had needed reading glasses after 45 years of age (group 2). RESULTS: Of all the ocular variables examined each year, two differed significantly between the two groups. Refraction at age 20 was 0.1+/- 0.3 D in group 1 and 0.0 +/- 0.3 D in group 2 ( P <0.05). Amplitude of accommodation at age 20 was 9.5 +/- 1.2 D in group 1 and 9.9 +/- 1.0 D in group 2 ( P <0.05). CONCLUSION: Hyperopia and low amplitude of accommodation at the age of 20 might predispose to early development of presbyopia in normal individuals.

Accommodation, Ocular↗