EXTENSIVE accounts of the blood vessels of the orbit are to be found in various text-books of ophthalmology and anatomy, but there are few systematic descriptions of the anomalies. The various authors differ very little from one another in their descriptions, and deal almost exclusively with the socalled normal pattern of the ophthalmic artery. It was therefore considered desirable to study the origin, course, branches, and anastomoses of the ophthalmic artery in detail.
MaterialThe origin and intra-cranial and intra-canalicular course of the ophthalmic artery were studied in 106 human orbits obtained from 58 dissection-room cadavers. There were three specimens from male children aged 4, 11, and 12 years, and the rest were from adults mostly past middle-age. Both sides were examined in 48 individuals, and in the remaining ten only one.Some features were studied in 170 specimens (this includes the 106 mentioned above). MethodsThe skull was opened and the brain removed leaving behind a long stem of the internal carotid arteries. The optic tracts were cut so that the optic chiasma and optic nerves were left intact within the skull, and investigations were carried out by two methods:(i) In 56 specimens from 28 cadavers (22 adult males, 3 adult females, 3 children), the origin and intra-cranial and intra-canalicular course were studied under a lowpower stereoscopic binocular dissection microscope with direct illumination from a ltmp having a high-power and low-voltage filament. Distances were measured by a micrometer disc introduced into the eye-piece of the microscope.(ii) The remaining fifty specimens (both sides in 20 individuals and only one side in 10) were examined with the naked eye.All the findings in those examined by the first method were submitted to statistical analysis and all the measurements and statistical data given in the text pertain to the first 56 specimens examined. The findings in the second group were not usually analysed statistically because they were not sufficiently detailed, but wherever the data from the second group are mentioned, a note to that effect is given in the text.
MaterialTHIS study was carried out in 61 human orbits obtained from 38 dissectionroom cadavers. In 23 cadavers both the orbits were examined, and in the remaining fifteen only one side was studied. With the exception of three cadavers of children aged 4, 11, and 12 years, the specimens were from old persons.Method Neoprene latex was injected in situ, either through the internal carotid artery or through the most proximal part of the ophthalmic artery, after opening the skull and removing the brain. The artery was first irrigated with water. After injection the part was covered with cotton wool soaked in 10 per cent. formalin for from 24 to 48 hours to coagulate the latex. The roof of the orbit was then opened and the ophthalmic artery was carefully studied within the orbit.
Observations
COURSEFor descriptive purposes the intra-orbital course of the ophthalmic artery has been divided into three parts (Singh and Dass, 1960).(1) The first part extends from the point of entrance of the ophthalmic artery into the orbit to the point where the artery bends to become the second part. This part usually runs along the infero-lateral aspect of the optic nerve.(2) The second part crosses over or under the optic nerve running in a medial direction from the infero-lateral to the supero-medial aspect of the nerve.(3) The third part extends from the point at which the second part bends at the supero-medial aspect of the optic nerve to its termination. It lies medial to the nerve.In two places the ophthalmic artery bends to change direction: one is seen at the junction of the first and the second parts and is designated the "Angle" in the text (
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