Non-contact measurement of ocular microtremor using laser speckle

E. Kenny; D. Coakley; G. Boyle

doi:10.1117/12.854557

Abstract

The human eye moves continuously even while it appears to be at rest. The involuntary eye movements causing this motion are called fixational eye movements. Ocular Microtremor (OMT) is the smallest (150 - 2500nm amplitude) and fastest (~ 80Hz) of these eye movements. OMT has been proven to provide useful clinical information regarding depth of consciousness and neurological disorders. Most quantitative clinical investigations of OMT have been carried out using an eye-contacting piezoelectric probe. However, this measurement procedure suffers from a number of disadvantages which limit the potential of the technique in the clinical environment. The need for eye contact requires the eye to be anaesthetised and not all subjects can tolerate the procedure. A promising alternative to the piezoelectric technique is speckle metrology. A speckle correlation instrument for measuring OMT was first described by Al-Kalbani et al. The approach presented in this paper is a non contact measurement technique implementing laser speckle correlation and using a highly light sensitive video camera operating at 500Hz. The OMT measurement technique in this paper was investigated using a human subject and an eye movement simulator. Using this system, measurement of speckle on the eye takes only a few minutes, no eye drops are necessary and no discomfort is caused to the subject. The paper describes the preliminary results of capturing speckle from the simulator and from the human eye in-vivo at eye safe laser powers. The effects of tear flow, biospeckle and speckle shifting by larger eye movements on the displacement information carried by the speckle are also discussed.

Citation Download Citation

E. Kenny, E. Kenny, D. Coakley, D. Coakley, G. Boyle, G. Boyle, } "Non-contact measurement of ocular microtremor using laser speckle", Proc. SPIE 7715, Biophotonics: Photonic Solutions for Better Health Care II, 771528 (18 May 2010); doi: 10.1117/12.854557; https://doi.org/10.1117/12.854557

ACCESS THE FULL ARTICLE

PERSONAL SIGN IN
Full access may be available with your subscription

Email or Username Forgot your username?

Password Forgot your password?

Show

Remember Email/Username on this computer

Remember Password

No SPIE account? Create an account
or Institutional Sign In via Shibboleth

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members: $14.40

Non-members: $18.00 ADD TO CART

Show All Keywords

Keywords/Phrases

Search In:

Publication Years