Related Experiment Video
Updated: May 19, 2026
The Measurement and Treatment of Suppression in Amblyopia
Published on: December 14, 2012
The effect of neutral density filters on testing in patients with strabismic amblyopia
Syed Yaser Habeeb1, Brian W Arthur, Martin W ten Hove
1Department of Ophthalmology, Queen's University, Kingston, Ont.
Objective:
To confirm if using a neutral density filter (NDF) affects eyes with strabismic amblyopia differently compared to fellow non-amblyopic eyes, and to determine if a similar effect could be observed when using a NDF during peripheral visual field testing.
Design:
Prospective controlled case series.
Participants:
19 subjects with strabismic amblyopia with visual acuities between 20/400 and 20/40 in their affected eyes were recruited to the study. Fellow non-amblyopic eyes served as the control group.
Methods:
Visual acuity in both eyes was assessed using a projected Snellen eye chart with two NDFs (0.4 and 3.0 densities). Visual fields were assessed using a Humphrey perimeter using one NDF (0.4 density). Best corrected visual acuity and visual fields were also recorded.
Results:
When using a 3.0 NDF, visual acuity was reduced in all eyes (p < 0.0001). When using a 0.4 NDF, visual acuity was significantly improved in eyes with strabismic amblyopia compared to unfiltered conditions (p = 0.0011). There was no significant effect by NDFs on visual field testing in eyes with strabismic amblyopia or fellow non-amblyopic eyes.
Conclusions:
Neutral density filters affect eyes with strabismic amblyopia differently than they do non-amblyopic eyes. A significant improvement in visual acuity of eyes with strabismic amblyopia was observed when using a 0.4 NDF compared to non-amblyopic eyes. Visual acuity was reduced in amblyopic as well as non-amblyopic eyes when viewing through a 3.0 NDF. No significant change in visual fields was observed when using a 0.4 NDF in amblyopic or non-amblyopic eyes.
