1997 年 56 巻 3 号 p. 242-257
Optokinetic nystagmus (OKN) of elderly Japanese was investigated as voluntary OKN and reflexive OKN, and results were analyzed both quantitatively and qualitatively. Subjects were healthy elderly Japanese over 65 years-old, and the OKN of these subjects were compared with those of healthy individuals in their 20's.
Experiments were conducted by Ohm-type rotating cylinder at 2°/sec2 for 90 seconds. Data were analyzed by a microcomputer. In the qualitative test, voluntary OKN was assessed as follows: delay of pursuit movements, deficit of smooth pursuit, delayed initiation in target catching and defect of catching movements; and reflexive OKN was assessed by the quality of nystagmus waves and nystagmus stripes. In the quantitative test, both voluntary and reflexive OKN were assessed by the number of nystagmus beats, slow phase velocity and rapid phase velocity.
The qualitative analysis of voluntary OKN showed a deficit of smooth pursuit, such as, saccadic pursuit, in many cases. Quantitatively, when the cylinder speed exceeded 40°-60°/sec, the slow phase velocity decreased in many cases. Furthermore, the rapid phase velocity decreased in some cases, and when compared with the rapid phase velocity per amplitude of younger subjects (in their 20's), that of elderly subjects was significantly lower.
The results of the qualitative and quantitative tests of reflexive OKN showed a few abnormalities.