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Accommodation responses of dominant and non-dominant eyes were compared in 18 healthy subjects aged 19-21 years to clarify the characteristics of dynamic accommodation. Internal targets were placed at -0,25D and -4.0D in an infrared optometer of a modified model, and external targets (brightness 30cd/cm^, diameter 35 mm) identical in appearance with the internal targets, were placed 4.0 m and 0.25 m in front of the eyes. Three experiments were carried out by monocular viewing of the internal targets and monocular and binocular viewing of the external targets, and the results were compared between the dominant and non-dominant eyes, in viewing the internal targets, near-to-far responses were suppressed. In binocular viewing, the accuracy of accommodative position was increased, and the function of dynamic responses was improved. Furthermore, myopic shifts were observed in the near position after far-to-near accommodation and in the far position after near-to-far accommodation in the dominant eye compared with the non-dominant eye, and shortening of the response time and an increase in the response velocity were noted only in binocular viewing. These findings suggest that the dominant eye is in a tonic state and plays the primary role in far-tonear accommodation in binocular viewing.

Accommodation responses of dominant and non-dominant eyes were compared in 18 healthy subjects aged 19-21 years to clarify the characteristics of dynamic accommodation. Internal targets were placed at -0.25 D and -4.0 D in an infrared optometer of a modified model, and external targets (brightness 30 cd/cm2, diameter 35 mm) identical in appearance with the internal targets, were placed 4.0 m and 0.25 m in front of the eyes. Three experiments were carried out by monocular viewing of the internal targets and monocular and binocular viewing of the external targets, and the results were compared between the dominant and non-dominant eyes. In viewing the internal targets, near-to-far responses were suppressed. In binocular viewing, the accuracy of accommodative position was increased, and the function of dynamic responses was improved. Furthermore, myopic shifts were observed in the near position after far-to-near accommodation and in the far position after near-to-far accommodation in the dominant eye compared with the non-dominant eye, and shortening of the response time and an increase in the response velocity were noted only in binocular viewing. These findings suggest that the dominant eye is in a tonic state and plays the primary role in far-to-near accommodation in binocular viewing.

A 61-year-old patient suffered from Charles Bonnet syndrome (CBS) while his visual acuity declined, whereas CBS subsided after he became blind. These findings suggest that reduction of visual acuity (dynamic or acute impairment) has a greater impact on the onset of CBS than low visual acuity (static or chronic impairment) per se in some patients. They may also explain why patients with low visual acuity do not always suffer from CBS. Although further studies are required, the present case highlights the importance of the differentiation between lowering and low visual acuity in the etiology of CBS.