Accommodation - Convergence Relationships and Age
Purpose. The objective of this study was to determine if there are differences in accommodative-convergence/accommodation (AC/A) and convergence-accommodation/convergence (CA/C) ratios in subjects with increasing age. The authors aimed to relate the findings to the present theories of the development of presbyopia.
Methods. Using a Canon AutoRef R-1 to measure accommodation and an IRIS eye movement monitor to measure eye movements, the authors determined objective AC/A and CA/C ratios for 23 subjects between 17 and 42 years of age with normal binocular vision. Changes in accommodation and convergence responses were stimulated by lenses (-1.00 DS and -2.00 DS) and prisms (4 and 8 prism diopters), respectively. Measures were made at two visits on consecutive days.
Results. A moderate linear relationship was found between AC/A ratio and age (P < .002), and a strong linear relationship was found between CA/C ratio and age (P < .0001). The decrease in CA/C ratio with age was due to a decreased accommodative response to prisms (P = .0001). Measurements were reliable, with 95% confidence intervals at ± 1.28 Δ/D and ± 0.02 D/Δ for AC/A and CA/C ratios, respectively. A reciprocal relationship existed between the AC/A and CA/C ratios.
Conclusion. The AC/A ratio increases, and the CA/C ratio decreases, in persons between 20 and 40 years of age. This may be because increasing ciliary muscle contraction is required to produce a given change in accommodation with increasing age or because of changes in the adaptability of the tonic accommodation and vergence systems with age.
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|Item Type:||Journal Article|
|Additional Information:||For more information, please refer to the journal’s website (see link) or contact the author. Author contact details: firstname.lastname@example.org|
|Keywords:||accommodation, convergence relationship, accommodation, convergence, age|
|Subjects:||Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)|
|Divisions:||Current > QUT Faculties and Divisions > Faculty of Health|
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 1995 Association for Research in Vision and Ophthalmology|
|Deposited On:||28 Sep 2006|
|Last Modified:||15 Jan 2009 17:12|
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