- Joined
- Apr 18, 2003
- Messages
- 14
- Reaction score
- 0
I've read a number of definitions of "tonic accommodation" but this term still confounds me. I found this definition online (see below), but I'm still not certain of its meaning. Is it a state of complete inactivity of the ciliary
muscles? Is it a state of partial contraction that is the particular
subject's resting state of accommodation?
I read a recent article that stated "fatigue reduces tonic accommodation." Does this mean that whatever state of contraction the ciliary muscles are in is reduced by fatigue? Or does it mean something else.
WHAT IS TONIC ACCOMMODATION?
TA is an accommodative state adopted without adequate
stimulation, for example in complete darkness.
It is an idiosyncratic, stable but adaptable, parameter for each
observer. For some, TA is suitable for a viewing distance of
infinity; for others it can be less than a metre. Leibowitz & Owens
(1975; Owens, 1984) found that observers who experienced
problems driving at night had a TA close to the distance of the
windscreen of their car and suggested that this could be a cause
of their problems.
Another puzzler is "accommodative hysteresis." Is this the same as a lag (delay) in accommodation, or does it mean something else?
Thanks,
Fran
muscles? Is it a state of partial contraction that is the particular
subject's resting state of accommodation?
I read a recent article that stated "fatigue reduces tonic accommodation." Does this mean that whatever state of contraction the ciliary muscles are in is reduced by fatigue? Or does it mean something else.
WHAT IS TONIC ACCOMMODATION?
TA is an accommodative state adopted without adequate
stimulation, for example in complete darkness.
It is an idiosyncratic, stable but adaptable, parameter for each
observer. For some, TA is suitable for a viewing distance of
infinity; for others it can be less than a metre. Leibowitz & Owens
(1975; Owens, 1984) found that observers who experienced
problems driving at night had a TA close to the distance of the
windscreen of their car and suggested that this could be a cause
of their problems.
Another puzzler is "accommodative hysteresis." Is this the same as a lag (delay) in accommodation, or does it mean something else?
Thanks,
Fran
