FRAME BY FRAME ANGIOGRAPHY

Volume monografia in lingua italiano/ inglese per il 78\ub0congresso S.O.I del 18-21 novembre 199

Arterio-venous transit time in the superficial layer of the optic nerve head: A new parameter of glaucomatous damage

Purpose:To evaluate arterio-venous transit time (AVTT) of the superficial layer of the optic nerve head (ONH) in primary open angle glaucoma (POAG). Methods:Circulation times of the superficial layer of the ONH were quantified - in 35 POAG and 35 age-matvhed controls - using an objective, electronic guided examination of a high speed dynamic fluorescein angiography. AVTT of the superficial layer of the ONH was compared between groups, and vs ONH morphology and visual field defects. Results: AVTT of the superficial layer of the ONH was significantly: higher in POAG patients vs controls ( 2.28 vs 1.29 sec; p< .001), and related to ONH morphology and field defects. Conclusion: AVTT of the superficial layer of the ONH may be exactly quantified and may represent a new, objective parameter of glaucomatous damage

Heritability of myopic refractive errors in identical and fraternal twins.

The existence of a visual feedback control of eye growth in humans is controversial, as the contributions of genetic and environmental factors are still unknown. To evaluate the heritability of refractive defects, we measured ocular refraction in 19 monozygote and 20 dizygote twin pairs (mean age 5 years). Monozygosity was ascertained by a common chorion, similarity of somatic traits, and identical dermatogliphes and was confirmed in myopes by blood marker diagnosis. Ocular refractive defects and axial length were evaluated by cycloplegic autorefractometry and biometry. By comparing identical and fraternal twins heritability of refractive defects was estimated to be 0.08-0.14; this low value indicates that the observed variability in refractive errors is nongenetic in origin. Three monozygote pairs were anisomyopic; differences between eyes in identical twins were related to the increased axial length of myopic eyes. In one eye, myopia was attributed to visual deprivation induced by a congenital cataract, while in five eyes it was correlated directly to the degree of astigmatic defects. The discordant axial length observed in monozygote twins is nongenetic. In agreement with previous findings reported in the literature, it is proposed that visual impoverishment of retinal images may play an early regulatory role in postnatal eye growth

Frame by frame dilution analysis of ICG angiography: a new method to measure choridal blood flow in glaucoma

Purposes: To identify a new method of choroidal blood flow analysis in glaucomatous patients. Methods: Twenty-four glaucomatous patients (G), 15 subjects with normal tensional glaucoma (NTG) and 26 age-matched controls were recruited for the study. They were submitted to dynamic indocyanine green angiography (ICGA) with a scanning laser ophthalmoscope (SLO) (Rodenstock, Munchen, Germany). The choroidal filling phases were digitized and stored in a computer. Twenty-five frames per second were obtained. Each frame was elaborated by means of a “ threshold technique ” in order to obtain black or white pixels. The area occupied by the white pixels in a field of 35° of the choroid surrounding the disc was measured. The data obtained from each frame were plotted versus time in order to obtain a “ frame-by-frame ” dilution curve. The 10% filling time and the 55% filling time were compared among the three groups. Results: NTG and G groups showed a significantly delayed filling time of the posterior choroid when compared to the controls (10% filling time, p<0.01; 55% filling time, p<0.05). No statistical difference between NTG and G could be observed. Conclusions: These data suggest that an altered choroidal blood flow can play a role in the pathogenesis of glaucoma. CR: None -