ENHANCED S-CONE SENSITIVITY SYNDROME - LONG-TERM FOLLOW-UP, ELECTROPHYSIOLOGICAL AND PSYCHOPHYSICAL FINDINGS

1. Six patients with enhanced S (short wavelength sensitive, blue) con e sensitivity syndrome including a follow-up between 1 and 19 y are de scribed. Four patients were male, two were female; two patients were b rothers. The enhanced S cone sensitivity syndrome is of autosomal rece ssive inheritance with variable expression even within a family. 2. Re cording the standard electroretinogram (ERG) showed similar responses at dark and light adapted conditions and reduced flicker responses. ER G recordings were unchanged up to 9 y follow-up. The reduction of ERG amplitudes induced by light adaptation is shifted to higher background intensities compared to normals. 3. ERGs elicited by chromatic stimul i revealed only blue cone responses for all stimulus conditions. There was no evidence for L (long wavelength sensitive, red) or M (middle w avelength sensitive, green) cone or rod activity in the ERG. 4. Colour vision was normal. Spectral sensitivity measurements showed no eviden ce for rod activity but the presence of all cone photopigments. A norm al course of transient tritanopia indicated an interaction between L a nd S cones. 5. The differences between psychophysical and electroretin ographical findings indicate the existence of functioning receptors an d neuronal pathways in all three cone systems in the presence of alter ed intraretinal electrical phenomenas.