Orbital depth measurements of human skulls in relation to retrobulbar anesthesia.

To investigate the orbital depth in human skulls in relation to retrobulbar anesthesia, we measured the distance between the lateral margin of the optic foramen and the border of the medium and outer third of the inferior orbital rim (retrobulbar needle pathway) in 50 skulls (25 males and 25 females). This distance varied from 4.4 to 5.7 cm in males (mean 5.024, SD 0.272) and from 4.5 to 5.5 cm in females (mean 4.9, SD 0.204). There was no real difference between males and females (p>0.05). For the total of 50 skulls the mean distance was 4.962 cm (SD 0.246). Shallow and deep orbits exist in both males and females but individuals with shallow orbits are obviously more susceptible to optic nerve injury by the retrobulbar needle.