Takeo Iida

Dynamic eye accommodation evoked by apparent distances

A three-dimensional optometer (TDO), which can measure simultaneously three major ocular functions in a working environment, was used to measure the visual responses of human subjects viewing: (1) actual artworks and (2) corrugation presented by moving random dots on a cathode ray tube (CRT). Measurements were performed in natural viewing conditions on two emmetropic females. Both subjects demonstrated distinct accommodative responses for the stimuli presented at a fixed distance. The results indicate that the accommodation generally shifts in accord with changes of perceived distance. The usefulness of the TDO was demonstrated in these experiments.

Three-dimensional optometer III

We describe a newly developed three-dimensional optometer III (TDO III) that can measure simultaneously three major ocular functions-accommodation, eye movement, and pupil diameter-and head movement in an actual working environment. The TDO III permits free head movement as well as free eye movement because the measurement component is mounted on the head. Its size has been reduced substantially compared with the original model. The remaining weight of TDO III is counterbalanced to minimize head loading weight. Normal lighting is permitted, and it is unnecessary to dilate the pupil withadrugfor measurement. TDO III can measure accommodation from -12.7 to + 26.6 D and 100% of the pupil diameter change when the eye moves within a 40° horizontal and 30° vertical area. Head movement is permitted within a sphere 200 mm in diameter. The accuracy when measuring both the accommodation and pupil diameter with TDO III is ±0.25 D and ±0.3 mm, respectively. The error when measuring the angles of the eyes is less than ±0.5°. The eye position accuracy is ±10 mm, and the three Cartesian angles are ±1°. The accuracy of TDO III has been intensively investigated in both artificial and human eyes.

Accommodation toward diameter change of a spotlight in a dark room.

The three-dimensional optometer (TDO III) was used to measure accommodative responses when gazing at a spotlight that changed its diameter in an otherwise completely dark room. Three emmetropic females served as subjects and the stimuli were presented at 33 cm ( -3 D) from the subjects. The subjects felt that the spotlight approached them when its diameter increased. However, the magnitude of accommodation when viewing the smaller diameter spotlight was greater than that for the larger diameter spotlight. This means that the eye accommodated less, although the spotlight was felt to be nearer, and contradicts the common belief based on the subjectively measured data reported earlier. By conducting several supplemental experiments, we infer that this phenomenon comes from the effort in reducing accommodation lag dynamically in order to see the smaller target more clearly.