In academic studies of color blindness, on the other hand, there is more interest in developing flexible tests to collect precise datasets, identify copunctal points, and measure just noticeable differences. Pseudoisochromatic plates
A pseudoisochromatic plate (from Greek pseudo, meaning "false", iso, meaning "same" and chromo, meaning "color") is the type of test exemplified by the Ishihara test, where a figure (usually one or more numerals) is embedded in the plate as a number of spots surrounded by spots of a slightly different color. The figure can be seen with normal color vision, but not with a particular color defect. The figure and background colors must be carefully chosen to appear isochromatic to a color deficient individual, but not an individual with normal color vision. Pseudoisochromatic Plates are used as screening tools because they are cheap, fast and simple, but they do not provide precise diagnosis of CVD, and are often followed with another test if a user fails the Ishihara test.The basic Ishihara test may not be useful in diagnosing young, preliterate children, who cant read the numerals, but larger editions contain plates that showcase a simple path to be traced with a finger, rather than numerals.One of the most common alternative color vision tests based on pseudoisochromatic plates is the HRR color test (developed by Hardy, Rand, and Rittler), which solves many of the criticisms of the Ishihara test. For example, it detects blue-yellow color blindness, is less susceptible to memorization and uses shapes, so it is accessible to the illiterate and young children.
Subgaleal hemorrhage, also known as subgaleal hematoma, is bleeding in the potential space between the skull periosteum and the scalp galea aponeurosis. Symptoms
The diagnosis is generally clinical, with a fluctuant boggy mass developing over the scalp (especially over the occiput) with superficial skin bruising. The swelling develops gradually 12–72 hours after delivery, although it may be noted immediately after delivery in severe cases. Subgaleal hematoma growth is insidious, as it spreads across the whole calvaria and may not be recognized for hours to days. If enough blood accumulates, a visible fluid wave may be seen. Patients may develop periorbital ecchymosis ("raccoon eyes").Patients with subgaleal hematoma may present with hemorrhagic shock given the volume of blood that can be lost into the potential space between the skull periosteum and the scalp galea aponeurosis, which has been found to be as high as 20-40% of the neonatal blood volume in some studies. The swelling may obscure the fontanel and cross cranial suture lines, distinguishing it from cephalohematoma, in which the bleed is confined by its subperiosteal location.Patients with subgaleal hemorrhage may also have significant hyperbilirubinemia due to resorption of hemolyzed blood. Laboratory studies may demonstrate reduced hemoglobin and hematocrit due to blood loss into the subgaleal space, and coagulation studies may reflect an underlying coagulopathy. Mortality has been reported to occur in 12-14% of cases, generally as a consequence of massive blood loss presenting with shock, often in the setting of uncorrected coagulopathy.