Comparison of the uniocular field of fixation assessed objectively and subjectively using the Goldmann perimeter

Aim: The uniocular field of fixation (UFOF) may be assessed using the Goldmann perimeter subjectively and objectively. Haggerty et al. in 2005 proposed a technique examining six axes corresponding to the primary field of action of each extraocular muscle (EOM). Comparative evidence on subjective and objective assessment and the effect of target size is unclear. The purpose of this study was to determine the effect of subjective and objective assessment and target size upon the mean total EOM excursions and individual muscle excursions using the Haggerty technique in normal subjects.

Methods: Volunteers were recruited with right visual acuity of 0.10 logMAR or better, no manifest strabismus, full ocular motility, and no ocular pathology. Subjective and objective UFOF using two fixation targets (1Ie and 1IIe) were plotted for the right eye by one examiner using the Haggerty technique on the Goldmann perimeter.

Results: Twenty-four participants (22 females, 2 males) with a mean age of 20.3 1.6 years were included. The mean total EOM excursions performed objectively using target 1Ie and 1IIe were 288.2 4.7 and 288.5 5.7 , and subjectively were 290.7 4.8 and 299.4 7.2. The mean total excursion comparing objective and subjective assessment was not affected by target size. Increasing the target size produced a significant enlargement in total EOM excursions when assessed subjectively but not objectively. As regards individual muscle excursions, the inferior rectus excursion showed the greatest difference when comparing subjective and objective assessment ( p < 0.0001). A significant difference was also found for the inferior oblique using target 1Ie. Only the inferior oblique was affected by increasing target size when assessed subjectively ( p ¼ 0.007). Bland-Altman analysis showed large variation comparing objective and subjective assessments and for increased target size.

Conclusion: The degree of excursion obtained performing objective and subjective assessment can vary for individual EOMs. Target size may also influence the mean total EOM excursion. Standardised method of assessment is vital when assessing the UFOF to avoid misinterpretation of change caused by a different methodology.