PURPOSE: To determine whether variation
in ocular rigidity (a quantity which describes the elastic properties of the
globe) affects the characteristics of horizontal saccadic eye movements
METHODS: Thirty-three young, visually
normal subjects participated with informed consent in the study. Axial length
was measured using the IOLMaster ocular biometer (Carl Zeiss, UK). Ocular
Rigidity coefficients were determined using Schiotz tonometry. Horizontal
saccades were stimulated randomly to 40 degrees in 10 degree steps using high
contrast targets presented on a CRT monitor. Eye movements were recorded
continuously at a sampling rate of 60 Hz using the Viewpoint video-eyetracker
(Arrington Research, USA)
RESULTS: Peak velocity increased
significantly with increasing ocular rigidity (F=30.810, df=2,263,
p<0.001). Time to peak velocity (F=41.601, df=2,263 p<0.001) and total
response time (F=22.167 df=2,263 p<0.001) decreased significantly with
increasing ocular rigidity. Ocular rigidity was significantly positively
correlated with peak velocity (R2=0.67, p<0.001), and
significantly negatively correlated with time to peak velocity (R2=0.64,
p<0.001), and total response time (R2=0.62, p<0.001).
CONCLUSION: The known relationship of ocular
rigidity with myopia can be extended to shorter hyperopic eyes which are
found to have higher ocular rigidity. The dynamic characteristics of saccadic
eye movements are found to vary systematically with ocular rigidity. These
findings suggest that the structural characteristics of the ocular globe are
an important factor in determining dynamic characteristics of eye movements.
|