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Purpose: Application of adequate correction of refractory errors for the treatment of asthenopia of young visual display terminal (VDT) workers was evaluated from subjective complaints and the effect on accommodation dynamics (step response) before and after 6 months., Methods: Young VDT workers who visited the clinic because of eye strain were consecutively selected. Fifteen workers who were under-corrected for myopia and three workers who were over-corrected for myopia were treated by "adequate correction of refractory errors" with spectacles or soft contact lenses. The adequate correction was defined as minimum convex lenses which could obtain visual acuity of 1.2 or better, similar to daily life conditions, without cyclopegia or fogging. The workers were in their 20's. Accommodative responses to step stimuli were recorded by infrared optometer, and questionnaires were filled out by the VDT workers concerning the severity (a severity rating in percent in five steps) of subjective symptoms (headache, dry eye, eye strain, and eye irritation). Spectacles or disposable contact lenses were prescribed for the workers for "adequate correction". Six months later, accommodative responses and subjective symptoms were evaluated and compared with under-or over-corrected conditions and adequate correction., Results: In under-corrected workers, the adequate correction significantly improved complains i.e. headache, eye strain, eye tiredness (p < 0.005). Accommodative responses also improved in gain (%), maximum velocity (D/sec), and time of accommodation and relaxation (p < 0.05). Three over-corrected workers showed improvement of complains and also accommodative response in gain, maximum velocity, and time of accommodation and relaxation., Conclusions: Application of "adequate correction" to young VDT workers with asthenopia by using adequately corrected spectacles or soft contact lenses improved the asthenopia and accommodative dynamics.

Purpose: Recording of "near triad responses" was done by static accommodative stimulation to reveal the qualitative analysis of asthenopia., Method: Twelve healthy subjects in agegroups of 20, 30, and 40 years were examined before and after several hours of visual display terminal (VDT) work after informed consent. Three trials of forward <-> backward movement of focusing on a target were carried out. Response curves of horizontal eye tracking and pupillary diameter, that is, convergence with miosis and divergence with mydriasis, were recorded continuously, bilaterally and simultaneously by TriIRIS., Results: 1) Normal patterns of vergence and pupillary responses with constant amplitudes were recorded in five subjects and were stable. 2 ) Gradual decline of the mydriatic peak was observed in two subjects, suggesting spastic accommodation. Increasing mydriatic peak or notching of mydriatic phase was seen in one eye each, suggesting tonic disaccommodation. These abnormal patterns were reversed by adequate refractive correction, and classified as an eye-fatigue group. 3) Abruption of miotic phase was observed in two cases of exophoria. 4) Low and declining amplitudes despite normal light response were observed in two subjects, suggesting debilitated accommodation, and they were classified as an eye-strain group. 5) Post-traumatic mydriatic anisocoria responded in parallel, suggesting paretic accommodation., Conclusions: Coordinated dynamics of near triad responses revealed remarkable characteristics of accommodative iris movements with vergence. These objective findings revealed the different patterns of functional disorder of accommodation.

Purpose: We investigated the effect on eyestrain of optical stimuli that we designed for accommodation and convergence systems., Methods: Eight female students were given optical stimuli for accommodation and convergence systems for 1.5 min immediately after 20 min of a sustained task on a 3-D display. Before and after the trial, their ocular functions were measured and their symptoms were assessed. The optical stimuli were applied by moving targets of scenery images far and near around the far point position of both eyes on a horizonal place, which induced divergence in the direction of the eye position of rest. In a control group, subjects rested with closed eyes for 1.5 min instead of applying the optical stimuli., Results: There were significant changes in the accommodative contraction time (from far to near) and the accommodative relaxation time (from near to far) and the lag of accommodation at near target, from 1.26 s to 1.62 s and from 1.49 s to 1.63 s and from 0.5 D to 0.65 D, respectively, and in the symptoms in the control group after the duration of closed-eye rest. In the stimulus group, however, the changes of those functions were smaller than in the control group., Conclusion: From these results, we suggest that our designed optical stimuli for accommodation and convergence systems are effective on asthenopia following accommodative dysfunction.

Purpose: We investigated eyestrain in normal subjects induced by gazing at a random-dot stereogram on a parallax barrier system 3-D display., Methods: The 41 subjects were divided into 4 groups according to the type of correction. Near point of accommodation, accommodative relaxation, and contraction times were measured with an accommodo-polyrecorder before and after a stereoscopic visual load, and 15 min and 30 min after a rest. The subjective symptoms were assessed by a 7-point rating questionnaire at the same time as the measurements., Results: After 15 min of sustained visual load, the near point of accommodation was prolonged significantly in the groups without correction and with soft contact lenses(SCL), and accommodative contraction and relaxation times were significant delayed in the groups without correction, with hard contact lenses(HCL), and with SCL but not in the group with spectacles. These changed values of accommodation returned to their previous value following the rest. Significant increase in the rating questionnaire was found in the subjective symptoms of "eyestrain", "eye heaviness", "clouding", "eye dryness" and "irritation of eyes" after loading in the groups without correction, with HCL, and with SCL. In the spectacle group, there was no significant change in the subjective symptoms of "clouding" and "eye dryness"., Conclusion: From these results, it is concluded that gazing at stereoscopic images on the parallax barrier system 3-D display causes severer eyestrain in cases of correction with contact lenses and in uncorrected cases than in cases with spectacles.

Using a computer-assisted infrared optometer with a pupillometer, we studied pupillary unrest of 20 eyes of 20 patients suffering from nonspecific ophthalmic complaints, and of 20 eyes of 20 normal controls. The patient group had smaller mean pupil area than the control group (29 mm2 vs 38 mm2, p < 0.01), and showed prominent pupillary unrest and increased mean coefficient of variation (CV) of the pupil area (9.2% vs 3.4%, p < 0.001). Frequently, fairly long duration waves (longer than 1 sec) could be seen in the recordings of pupillary unrest in the patient group, but not in the control group. The patient group also showed significantly higher dark focus of accommodation than the control group (1.1 D vs 0.4 D, p < 0.01). These findings suggest that abnormal parasympathetic excitation may play a role in the etiology of continued nonspecific ophthalmic complaints.

The authors studied tonic accommodation in cases of asthenopia. The subjects consisted of ten college students, aged 20 to 22 years old as normal control and seven patients with asthenopia, aged 20 to 27. The dark focus of accommodation was measured with the infrared optometer before and after a 15 min sustained visual task. No significant differences were found between the two groups on the pre-task dark focus of accommodation. After the task, significant differences were found between the pre- and post-task dark focus of accommodation in patients with asthenopia. The results suggest that the patients with asthenopia are more susceptible to autonomic nervous system imbalance than healthy persons.

The effects of magnetic fields on the accommodation of operators engaged in visual display terminals (VDT) who complained of asthenopia and proved to have some abnormalities in the semistastic properties of accommodation were examined. Before and after loading a magnetic field of 400 Gauss or 2,000 Gauss on the eye, the quasistatic properties of accommodation were measured and compared. The quasistastic properties analyzed in this experiment were the maximum amplitude of accommodation and the gradient of accommodation that means a ratio of accommodative response to accommodative stimulus. Both factors were statistically improved in a dose dependent manner after loading the magnetic field, i.e. 2,000 Gauss was more effective than 400 Gauss concerning the improvement of accommodation. To exclude a psychogenic effects, simulated loading by a placebo which was an imitation magnet which did not produce a magnetic field was also applied to the patients, but no improvement was detected. Normal persons who were examined as controls showed no statistical change in the semistastic properties of accommodation after loading of the magnetic field. After examination of the semistatic properties of accommodation, refraction was also estimated by an autorefractometer, but no change was detected in either patients or controls. The magnetic field seemed definitely to have effects on the functionally involved accommodative system.