[Sensitivity loss in short wavelength sensitive cones in myopic eyes]

To investigate early changes of visual function in high myopic eyes, the relative sensitivity of the short-wavelength sensitive cones (s-cones) was measured by flash-evoked cortical potentials and electroretinograms and their relation with refractive error and axial length of the eyes was studied. A Ganzfeld stimulus was employed. The subjects were all under 37 years of age and were divided into 3 groups according to the magnitude of the refractive error as follows; 1) emmetropia/low myopia group (10 eyes), between +0.50 D and -3.00 D; 2) medium myopia group (8 eyes), between -3.25 D and -6.00 D; and 3) high myopia group (10 eyes), over -6.25 D. Their corrected visual acuities were better than 1.0 and their color vision was normal according to Panel D-15 and SPPII. They had no other ophthalmological abnormalities except tigroid fundus. The s-cone sensitivity was significantly correlated with the refractive error and axial length (p < 0.001) and was reduced prior to ophthalmoscopic retinal changes in the medium and high myopia groups. This indicates that the site of s-cone sensitivity loss in myopia is in the retinal.