1. Essilor Anti-Reflective Coatings Induce Haidinger’s Brushes Reversal
Christopher M Putnam OD, Carl J Bassi PhD
University of Missouri – St. Louis College of Optometry
Purpose
Results
Haidinger’s brushes are an entoptic phenomenon observed when a light source is viewed through a rotating polarizer and a “blue” filter. Anecdotal reports of Haidinger’s brushes reversal have been reported when viewed through spectacle lenses with an anti-reflective (AR)-coating.
Of the 9 lens blanks evaluated, only 2 resulted in a perceptual rotation reversal recognized by all 11 subjects. Both lenses are manufactured by Essilor: Crizal Alize and Crizal Avance. Additionally, off-axis viewing caused changes in rotational direction.
Experimental Methods
Table 1: Results for 11 subject’s rotational perception of Haidinger’s brushes when viewed through lens blanks.
A rotating polarizer was built using an LED array and a reversible, variable speed motor to maximize contrast during viewing of Haidinger’s brushes (Fig. 1 & 2). Nine different AR-coated lens blanks from Hoya, Zeiss, Sola and Essilor were assessed by 11 subjects for perceptual reversal of Haidinger’s brushes compared to viewing through no lens or non-AR coated lenses. Each trial used a fixed rotational velocity of the polarizer and a 50cm viewing distance. Masked AR lens blanks were presented in random order and each subject reported visualization of Haidinger’s brushes before placing a trial AR lens blank in place.
Conclusions
Two Essilor AR-coatings (Crizal Alize and Crizal Avance) produced reversal of the rotational direction of Haidinger’s brushes in all of our subjects. Such changes have possible implications for assessment of the entoptic phenomenon in clinical settings as well as possible interactions with the polarized displays found in many electronic devices. Further work is on-going to determine the mechanisms involved with these findings.
Figure 1: Subject’s view of Haidinger’s brushes.
Future Directions
Existing literature reports changes in rotational direction of a non-polarized object as a function of rotational velocity. Further study is warranted to determine if polarized objects also show rotational velocity dependence.
References
1) Bone RA. (1980). The role of the macular pigment in the detection of polarized light. Vision Research. 20(3):
2) Le Floch A, Ropars G, Enoch J, Lakshminarayanan V. (2010). The polarization sense in human vision. Vision research. 50(20):
3) Misson GP. (2003). A Mueller matrix model of Haidinger's brushes. Oph and Physl Optics. 23(5):
Figure 2: Rotating polarizer used to generate Haidinger’s brushes.
Figure 3: Diagram depicting AR coating effect on incident light.