Amplitudes and implicit times of the several oscillatory potentials (OP's) in the human electroretinogram have been studied in relation to temporal, adaptive and spectral stimulus variables. The last of the OP-wavelets responds differently from the preceding ones; its implicit time shortens with increase in stimulus frequency or adaptive illumination, whereas that of the preceding OP's is prolonged or stays constant. Moreover, the last OP-wavelet is time locked with the stimulus offset, whereas the others are not. This can be confirmed by linear subtraction of responses to an isolated stimulus onset from responses to stimuli of variable durations. These results indicate, that the last oscillatory potential is related to the light offset and is presumably generated by the retinal off-elements described in single cell recordings.

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The permeability of the blood-ocular barrier was examined by fluorophotometry in adolescent and adult diabetic patients before the onset ofretinopathy. (r=0.79, p<0-0001) with the duration ofdiabetes. Anterior chamber (AQ) values, an index ofthe permeability ofthe blood-aqueous barrier (BAB), increased in the adolescent diabetic patients compared with the controls and showed a significant positive correlation with glycosylated haemoglobin levels. No significant differences from the controls were observed regarding the permeability of the blood-retinal barrier (BRB). In the adult group there was no significant difference in either the permeability of the BRB or the AQ values between the diabetic and the control groups. Our results suggest that adolescent diabetic patients differ from adults in that BAB permeability is increased before the onset of retinopathy, suggesting that this is the cause of the striking increase in lens autofluorescence. (BrJ Ophthalmol 1993; 77: 158-161)

To study the correlation between blood-retinal barrier (BRB) permeability and development of form deprivation (FD) myopia, FD was induced in tree shrews. The refractive error and the axial dimensions of the optical elements were measured. Ocular fluorescence was measured before and after fluorescein-Na injection. The inward permeability (P(in)) of the BRB was measured before and 15, 30, and 45 days after FD was induced. FD eyes became significantly myopic 15 days after FD was induced (P<0.01), and myopia progressed 45 days after FD was induced compared with untreated controls. Neither anterior chamber length nor lens thickness changed significantly. The vitreous chamber in FD eyes, however, was significantly elongated from 15 days after FD was induced (P<0.01) compared with controls. The P(in) ratio (P(in) [FD eye]/P(in) [untreated control]), increased significantly 45 days after FD was induced (P<0.05). In FD myopia in tree shrews, the BRB permeability increases abnormally. Impaired BRB function might be a secondary effect of myopia development rather than the cause of myopia.