The entoptic view of the retinal vessels

The first time the retinal vessels were seen in man in vivo was reported in 1819 by Purkinje as an entoptic view. This was understood to show the shadow of the vessels, an interpretation objected to in 1834 by Brewster. Müller in 1855 (Über die entoptische wahrnehmung der netzhautgefässe, insbesondere als beweismittel für die lichtperception durch die nach hinten gelegenen netzhautelemente, Stahel, Würzburg) used the phenomenon to deduce the location of the photoreceptive layer of the retina, and his conclusion is accepted as true today. Because the phenomenon has some characteristics of an afterimage, it touches on the question of what is subjective and what is objective physical reality. It was recently used clinically to measure potential visual acuity and in the diagnoses of diabetic retinopathy and macular degeneration.     

Bietti crystalline retinal dystrophy with subfoveal neurosensory detachment and congenital tortuosity of retinal vessels: case report

A 34-year-old man presented with reduction and distortion of vision in both the eyes. The best-corrected vision was 20/20 parts, N6 in either eye. The external and slit lamp examination of both the eyes was unremarkable. The fundus examination showed multiple intraretinal crystalline deposits at the posterior pole, extending up to midperiphery, tortuous retinal blood vessels with S-shaped deflections, and absent foveal reflex in both the eyes. There were no corneal crystals, and the color vision was defective in both the eyes. Fundus autofluorescence and fundus fluorescein angiogram (FFA) were suggestive of geographic areas of retinal pigment epithelium (RPE) and choriocapillary (CC) loss. OCT revealed subfoveal neurosensory detachment. Flash ERG and EOG were normal except for a slight decrease in amplitude and delay in latency of pattern ERG waveforms. The Humphrey’s visual field showed paracentral scotoma with reduction in the amplitude of waveforms from the corresponding area in the multifocal ERG in both the eyes. Systemic evaluation for crystalline retinopathy was unremarkable. He was diagnosed to be a case of Bietti crystalline retinopathy (local/regional variant). The subfoveal neurosensory detachment could represent early RPE dysfunction caused by these crystals and could account for the mild visual disturbance in both the eyes. Retinal vascular tortuosity and neurosensory detachment seen in this case is the first time to be reported in literature.     

Vitreoretinal juncture over retinal vessels

Summary Previous studies have attributed changes in the retinal surface over or adjacent to large superficial retinal vessels to a variety of conditions, the most common being anomalous vitreoretinal attachments. The fundamental nature of the lesions and their pathogenesis, however, has remained controversial. The present study was undertaken to categorize the ultrastructural alterations of the vitreoretinal juncture over retinal vessels in the posterior fundus of man, and to clarify the relationship of these fundamental changes to clinically significant lesions in this region.Results show no difference in vitreoretinal, or more specifically vitreolaminar attachments over vessels when compared with adjacent regions. The cause of the more significant anomalies, notably surface breaks and their sequelae, is apparently multifactorial and related to a sequence of events. Initially three events predispose to or cause small surface breaks: developmental thinning of the inner limiting lamina; subsurface retinal degeneration; and transmigrating macrophages. These small surface breaks, when complicated by vitreous incarceration or by simple epiretinal membrane formation, can during posterior vitreous detachment cause peeling of the retinal surface, and the resulting large surface breaks may in turn provoke more complex proliferative lesions of the vitreoretinal juncture.This investigation was supported in part by U.S. Public Health Service research grants EY 00331, EY 01090, and EY 00725 from the National Eye Institute, National Institutes of Health     

Rat retinal blood vessels.

The largest arteries in the rat retina are the arterioles in the nerve fiber layer adjacent to the optic papilla. They are 50 to 100 micrometer in diameter, have an incomplete internal elastic lamina and usually a single layer of smooth muscle. Smaller arterioles of 10 to 50 micrometer have no internal elastic lamina and the media is formed by one or two layers of slender smooth muscle cells. In these vessels, myoendothelial junctions and close contact areas between smooth muscle cells are numerous. Capillaries are present in all layers of the rat retina and from plexuses in the nerve fiber, outer plexiform and exterior part of the inner plexiform layers. In nearly all capillaries, pericytes and their processes from a single layer external to the endothelium with numerous contact points or zones between endothelium and pericytes without any intervening basal laminar material. Areas of close contact between adjacent pericyte processes are frequent. The possible functions of myoendothelial junctions and pericyte-endothelial contacts in relation to vessel tone, mechanical stabilization and metabolic exchange are discussed.     

正常视网膜血管直径的非对称性研究

目的:利用IMAGEnet软件对眼底血管造影数字图像进行视网膜血管直径测量以探讨正常眼视网膜血管直径是否存在差异。方法:利用IMAGEnet软件对眼底血管造影数字图像进行放大和对比度调整,测量4个象限近视盘周围1PD范围内的视网膜动脉直径(RAD)和静脉直径(RVD),计算视网膜动静脉比值(A/V)并检验该测量方法的可重复性。结果:左右眼对应象限之间的RAD,RVD和A/V比值差异无统计学意义,但对单眼而言,颞侧与鼻侧象限的RAD和RVD以及A/V比值有着显著性差异。可重复性检验以类内相关系数(intraclass correlation coefficient,ICC)来表示,RAD的者内信度为0.97(P<0.01),RVD为0.986(P<0.01);RAD的者间信度为0.976(P<0.01),RVD为0.975(P<0.01)。结论:正常双眼对应象限的视网膜血管直径没有差异,但单眼不同象限的视网膜血管直径存在差异,利用IMAGEnet软件对视网膜荧光造影血管直径进行测量是可行和可靠的。     

In vivo micropuncture of retinal vessels

Micropuncture has proven to be a valuable tool for the local study of vascular parameters in many organ systems; however, it has not been applied to the study of the circulation of the retina. We report here our extension of micropuncture techniques [4] to use in the intact retina of the anesthetized cat. We use extremely sharp micropipettes with tip sizes much smaller than the diameter of erythrocytes to avoid hemorrhage. The micropipette is held by a microdrive which in turn is mounted on a precision goniometric micromanipulator. We micropuncture retinal arteries and veins with diameters ranging from 20 to 130 m with no apparent damage to the vessel wall and no observed hemorrhage. During micropuncture we routinely inject nanoliter quantities of dyed saline, which we observe flowing in a plume from the micropipette tip within the lumen of the vessel. Micropuncture techniques may be used in the laboratory to study retinal autoregulatory mechanisms by microinfunsion of vasoactive substances and by measuring blood pressure in retinal microvessels. In the clinic micropuncture may be useful for treating disorders such as retinal vascular occlusion.