The history of the scientific elucidation of ocular counterrolling
Documenta Ophthalmologica , Volume 61 - Issue 2 p. 183- 189
The history of the elucidation of ocular counterrolling (OCR) is an interesting one. Although discovered two centuries ago, OCR has remained a contro- versial issue, even in our days. The main reason for this, is that rolling move- ments of the eyes about the line of sight are not easily detected or measured. OCR can be static, i.e. about 5 degrees counterrolling of the eyes which partly compensates for tilting of the head with respect to gravity, or it can be dynamic, that is to say a rotatory optokinetic and vestibular nystagmus. The rolling movement of the eyes about the line of sight can be seen when tilting the head of another person towards one of his shoulders. Close inspec- tion of the conjunctival vessels reveals the jerking movements of the quick phase of the rotatory nystagmus. This is what John Hunter must have seen some two hundred years ago, as he described dynamic OCR in 'The use of the oblique muscles', in a book called 'Observations on certain parts of the animal oeconomy' (1786).