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.