Subjective Accommodative Function and Defocus Curve Metrics in Phakic Adults Aged 45-65 Years

To evaluate accommodative amplitude (AA), accommodative lag (LAG) and defocus curve (DC) metrics in phakic adults aged 45-65 years, and investigate their relationships.

Observational cross-sectional study including 77 subjects stratified into four age groups (G1-G4: 45-50, 51-55, 56-60 and 61-65 years, respectively). AA was measured using the push-up method and LAG at 40 cm and 66 cm using an open-field autorefractometer. Monocular DC were obtained and two summary metrics derived: area under the curve (AUC) and defocus cut-off at 0.20 logMAR. Differences among age groups were analysed using appropriate statistical tests, and regression models evaluated the predictive value of age and defocus cut-off for AA.

AA decreased significantly with age (G1-G4: 2.41 ± 0.53, 2.13 ± 0.63, 1.61 ± 0.44 and 1.75 ± 0.73 D; p < 0.001), with higher values in younger (45-55 years) compared with older subjects (56-65 years) and no significant differences within each age cluster. LAG remained stable at both 40 cm (p = 0.27) and 66 cm (p = 0.50). DC metrics showed significant age-related changes, with reduced AUC and less defocus cut-off values in older groups (p < 0.001). AUC differed significantly between G1 and G4 and between G2 and G4, whereas defocus cut-off differed only between G2 and G4. Age (R² = 0.22) and defocus cut-off (R² = 0.09) had limited predictive value for AA.

AA and DC metrics decline with age, whereas LAG remains stable. Their weak association suggests that they reflect partially distinct aspects of visual function. DC analysis captures aspects of functional near visual performance that are not fully reflected by accommodative measurements alone, which may be useful for a more comprehensive characterisation of presbyopic visual function and for the evaluation of presbyopia-correcting interventions.