Nearwork-induced changes in lenticular thickness in different refractive groups

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Myopia is a prevalent refractive error associated with increased risk of visual impairment.
• Understanding the accommodative mechanisms in myopia is crucial for developing effective interventions.
• Previous studies suggested a role for the crystalline lens in accommodative changes during near work.

Purpose of the Study:

• To directly measure changes in human crystalline lens thickness.
• To assess the additivity of lenticular thickening after prolonged reading.
• To compare these changes between myopic and emmetropic young adults.

Main Methods:

• A-scan ultrasonography was used to measure axial lenticular thickness.
• Measurements were taken before and after 1 and 2 hours of continuous near reading (35-40 cm).
• Thirty-five young adults (12 early-onset myopes, 11 late-onset myopes, 12 emmetropes) participated.

Main Results:

• Mean lenticular thickness increased by 0.025 ± 0.011 mm after 1 hour and 0.035 ± 0.017 mm after 2 hours.
• The increase in lenticular thickness was significantly greater after the second hour compared to the first.
• This additive effect was observed exclusively in both early-onset and late-onset myopic groups.

Conclusions:

• Lenticular thickening during prolonged near work is additive in myopic individuals.
• This finding objectively supports the hypothesis of increased lenticular accommodative susceptibility in myopia.
• The crystalline lens plays a significant role in the accommodative response of myopes during sustained near tasks.