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Tonic accommodation: a review. II. Accommodative adaptation and clinical aspects
M Rosenfield1, K J Ciuffreda, G K Hung
1Department of Vision Sciences, State University of New York/State College of Optometry, NY 10010.
Summary
Tonic accommodation (TA) adaptation may involve a slow decay of stimulus-mediated responses, not a change in ciliary muscle innervation. Evidence linking TA or adaptation to myopia is inconclusive, suggesting a minor role for TA in steady-state accommodation.
Area of Science:
- Ophthalmology
- Optometry
- Vision Science
Background:
- Tonic accommodation (TA) refers to the accommodative response under degraded stimulus conditions.
- Accommodative adaptation is the change in TA after sustained fixation.
- Part II of this review examines accommodative adaptation and clinical aspects of TA.
Purpose of the Study:
- To review accommodative adaptation and its clinical implications.
- To discuss the relationship between TA, accommodative adaptation, and myopia.
- To evaluate the role of TA in steady-state accommodation.
Main Methods:
- Review of existing literature on tonic accommodation and accommodative adaptation.
- Analysis of the mechanisms underlying accommodative adaptation.
- Discussion of clinical implications for refractive error development.
Main Results:
- The apparent shift in TA post-fixation likely reflects slow decay of adaptive responses, not altered ciliary muscle innervation.
- Evidence associating TA or accommodative adaptation with myopia, particularly nearwork-induced myopia, is equivocal.
- Tonic accommodation appears to play a minor role in the closed-loop steady-state accommodative response.
Conclusions:
- Accommodative adaptation mechanisms are distinct from baseline tonic accommodation.
- The link between TA, accommodative adaptation, and myopia requires further investigation.
- Tonic accommodation has a limited influence on overall steady-state accommodation.