Retinal haemorrhages.

Site and appearance of retinal haemorrhages Retinal haemorrhages occur when there is extravasation of blood, either into the retina itself (intraretinal), between the retina and the retinal pigment epithelium (subretinal), or between the retina and the hyaloid face of the vitreous body (subhyaloid or preretinal). The shape and colour of the haemorrhages are determined by the level or levels of the retina affected, and they are often mixed. Often the hyaloid face ruptures and the haemorrhage spreads into the vitreous (intravitreal). Richman in 1936 classified retinal haemorrhages into four groups according to the morphological appearances,' and their location can be determined by their clinical appearance. The ophthalmoscopic appearance of preretinal blood depends on its age and the size and shape of the blood filled space. Fresh preretinal blood usually looks like a dome shaped, semilunar, crescentic, or geographic accumulation of dark red blood overlying and obscuring its source. With time the same accumulation of blood can look semilunar or crescentic in shape, with a fluid level caused by gravitational settling of the formed elements. The plasma-erythrocyte interface may shift with changes in the position of the head. A faint line of residual blood usually marks the superior extent of the space originally filled with whole blood. Intraretinal haemorrhages may be splinter shaped, flame shaped, or 'dot and blot' rounded haemorrhages. Splinter haemorrhages are small, linear, dull red, and lie superficially about the disc margin parallel to the major vessels, their shape being determined largely by the nerve fibre layer of the retina and the vessels. They may be single or multiple, and they clear rapidly. Flame shaped haemorrhages are bright red, and lozenge shaped with a striated or serrated outline on at least one margin, and they follow the course of the retinal nerve fibre layer. They occur in the posterior pole of the fundus and are characteristically associated with disorders of. the superficial radial peripapillary capillaries. Dot and blot haemorrhages are dense, dark red, and sharply outlined. They are located within the compact middle layers of the retina and are seen in association with disorders that predominantly affect the deep retinal capillary system. Occasionally several discrete blot haemorrhages may coalesce and appear as an irregular geographic accumulation of blood. Subretinal haemorrhages typically appear as irregular red plaques or opaque reddish circular lesions deep to the retina and retinal vessels (between the photoreceptors and pigment epithelial layer). On resolution they can result in a disturbance of the underlying retinal pigment epithelium. Haemorrhage beneath the retinal pigment epithelial layer is usually confmed, and related to a rupture (for example, trauma or pseudoxanthoma elasticum) in Bruch's membrane, which is normally adherent to it. This results in diffuse, roughly linear haemorrhages of variablesometimes great-extent. Haemorrhage within the choroid expands freely and forms pool like areas the ophthalmoscopic appearance of which is governed by the density of the overlying pigmentation. Generally, choroidal haemorrhages appear as dark reddish blue areas, obviously deep in the fundus, and they usually absorb leaving a normal fundus. Some intraretinal and preretinal haemorrhages have white centres. Such lesions (or Roth's spots) are not specific for any single underlying disorder. The white centre can be focal ischaemia, an inflammatory infiltrate, a colony of infective organisms, fibrin and platelets, or an accumulation of neoplastic cells. It is easy to mistake the bright light reflex from the internal limiting membrane over the apex of a retinal haemorrhage for the small white centre of a haemorrhage. Intravitreal haemorrhages are relatively uncommon in children; they usually resolve slowly but completely,2 but in young children may cause amblyopia warranting early vitrectomy.