Age-related changes in visual performance: A defocus curve study in healthy phakic eyes.

Defocus curves remained stable up to 44 years of age, with significant decline in baseline VA, curve steepness, and overall visual performance beginning at 45 years.

• 105 subjects were evenly distributed into seven age groups spanning 20-65 years (15 subjects per group)
• Age groups were: G1 (20-24), G2 (25-34), G3 (35-44), G4 (45-50), G5 (51-55), G6 (56-60), G7 (61-65)
• A clear demarcation was found between younger groups (G1-G3; 20-44 years) and older groups (G4-G7; 45-65 years)
• A linear mixed-effects model was used to assess group differences in defocus curve shape

Area under the curve (AUC) values significantly decreased with age, with clear separation between younger and older age groups.

• AUC was used as a metric to capture overall visual performance across the defocus range from -3.00 D to +1.00 D
• Non-parametric and parametric tests were used to evaluate differences in AUC between groups
• Younger groups (G1-G3; 20-44 years) showed significantly higher AUC values compared to older groups (G4-G7; 45-65 years)
• Monocular VA was measured at defocus levels from -3.00 D to +1.00 D in 0.50 D steps

The 0.2 logMAR cut-off point could not be reached in most younger subjects, indicating preserved accommodative capacity in those aged 20-44 years.

• The negative defocus cut-off point at 0.2 logMAR VA was used as one of four key metrics for defocus curve analysis
• Younger subjects (G1-G3) largely did not reach the 0.2 logMAR threshold under negative defocus, indicating preserved depth of focus
• Older subjects showed a progressive reduction in depth of focus
• Statistically significant differences in cut-off points were found particularly between groups G4 (45-50 years) and G7 (61-65 years)

Older subjects showed a progressive reduction in depth of focus with statistically significant differences particularly between groups G4 and G7.

• G4 corresponded to the 45-50 year age group and G7 to the 61-65 year age group
• The reduction in depth of focus was characterized as progressive across the older age groups
• This finding reflects early-to-advancing presbyopic changes in depth of focus tolerance
• Both AUC and cut-off point metrics demonstrated statistically significant differences between these groups

Four key metrics were identified for characterizing defocus curves: baseline VA at zero defocus, curve slope, area under the curve, and the negative defocus cut-off point at 0.2 logMAR VA.

• This was an observational cross-sectional study design
• All measurements were monocular
• Defocus levels ranged from -3.00 D to +1.00 D in 0.50 D steps
• A linear mixed-effects model was used to assess group differences in defocus curve shape alongside non-parametric and parametric tests for AUC and cut-off points

Defocus curve analysis was identified as a valuable tool to assess age-related visual changes beyond conventional distance and near VA tests.

• The study characterizes the impact of age on visual performance across a wide age range (20-65 years) in healthy phakic eyes
• The transition at 45 years was described as reflecting 'early presbyopic changes, marked by reduced tolerance to defocus and diminished depth of focus'
• Conventional VA tests were considered insufficient to capture the full scope of age-related visual performance changes
• The authors suggest defocus curves provide additional functional information about accommodative capacity and depth of focus