title: The effect of neutral density filters on testing in patients with strabismic amblyopia.
abstract: 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.
  
  
  METHODS
  Prospective controlled case series.
  
  
  METHODS
  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.
authors.affiliation: Department of Ophthalmology, Queen's University, Kingston, Ont.
authors.forename: Syed Yaser
authors.initials: SY
authors.lastname: Habeeb
authors.forename: Brian W
authors.initials: BW
authors.lastname: Arthur
authors.forename: Martin W
authors.initials: MW
authors.lastname: ten Hove
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000550:Amblyopia / Q000175:diagnosis* / Q000503:physiopathology; D002648:Child; D006801:Humans; D008875:Middle Aged; D055096:Optical Devices; D011446:Prospective Studies; D013285:Strabismus / Q000175:diagnosis* / Q000503:physiopathology; D014787:Vision Tests / Q000295:instrumentation*; D014792:Visual Acuity / Q000502:physiology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology