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The bidirectional laser Doppler technique and monochromatic photography were used to measure the absolute blood flow rate in the majortemporal retinal arteries in seven patients foliowing unilateral scleral buckling and encircling procedures, and in two patients before and after removal of scleral buckling elements. In the seven patients who had undergone uncomplicated scleral buckling procedures the arterial flow rates were on average 50% lower (p=0-01) in the surgicaily treated eyes than in the contralateral eyes. Removal of scleral buckling elements in two patients produced increases of 73% and 44% in arterial blood flow rates.In the current study we used the newer bidirectional laser Doppler technique and monochromatic retinal photography to measure for the first time absolute retinal blood flow rates in seven patients who had undergone unilateral scleral buckling procedures for the repair of retinal detachment. Specifically we compared the blood flow rates measured in retinal arteries of surgically treated eyes with the flow rates measured in corresponding arteries in fellow eyes. In two additional patients who experienced complications after scleral buckling procedures absolute blood flow rates were measured in retinal arteries before and after removal of the buckling elements.

In a double-masked, randomized, placebo-controlled study, we evaluated the effect of topical timolol maleate 0.5% on the retinal, choroidal, and optic nerve head circulation in 5 healthy volunteer subjects. Changes in the pulsatile component of choroidal blood flow (PCBF) were determined from measurements of the ocular pulse wave. Changes in the retinal arterial blood flow rate (RBF) and optic nerve head capillary blood speed (CBS) were determined by laser Doppler velocimetry and monochromatic photography. In timolol-treated eyes, PCBF decreased by 32 ± 12% (p = 0.0007). Changes in RBF and CBS were not statistically significant. In the contralateral placebo-treated eyes, PCBF decreased by 15 ± 8% (p = 0.006) and RBF increased by 18 ± 10% (p = 0.002). The change in CBS was not statistically significant.

The effect of segmental scleral buckling (SB) on ocular circulation was evaluated by measurements of the ocular pulse amplitude (PA) and the ophthalmic artery pressure (OAP) (Br3' Ophthalmol 1992; 76: 529-531)

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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)