title: Do small-aperture presbyopic corrections influence the visual field?
abstract: OBJECTIVE
  To explore the effect of small-aperture optics, designed to aid presbyopes by increasing ocular depth-of-focus, on measurements of the visual field.
  
  
  METHODS
  Simple theoretical and ray-tracing models were used to predict the impact of different designs of small-aperture contact lenses or corneal inlays on the proportion of light passing through natural pupils of various diameters as a function of the direction in the visual field. The left eyes of five healthy volunteers were tested using three afocal, hand-painted opaque soft contact lenses (www.davidthomas.com). Two were opaque over a 10 mm diameter but had central clear circular apertures of 1.5 and 3.0 mm in diameter. The third had an annular opaque zone with inner and outer diameters of 1.5 and 4.0 mm, approximately simulating the geometry of the KAMRA inlay (www.acufocus.com). A fourth, clear lens was used for comparison purposes. Visual fields along the horizontal meridian were evaluated up to 50° eccentricity with static automated perimetry (Medmont M700, stimulus Goldmann-size III; www.medmont.com).
  
  
  RESULTS
  According to ray-tracing, the two lenses with the circular apertures were expected to reduce the relative transmittance of the pupil to zero at specific field angles (around 60° for the conditions of the experimental measurements). In contrast, the annular stop had no effect on the absolute field but relative transmittance was reduced over the central area of the field, the exact effects depending upon the natural pupil diameter. Experimental results broadly agreed with these theoretical expectations. With the 1.5 and 3.0 mm pupils, only minor losses in sensitivity (around 2 dB) in comparison with the clear-lens case occurred across the central 10° radius of field. Beyond this angle, sensitivity losses increased, to reach about 7 dB at the edge of the measured field (50°). The field results with the annular stop showed at most only a slight loss in sensitivity (≤3 dB) across the measured field.
  
  
  CONCLUSIONS
  The present theoretical and experimental results support earlier clinical findings that KAMRA-type annular stops, unlike circular artificial pupils, have only minor effects on measurements of the visual field.
authors.affiliation: Institute of Health & Biomedical Innovation, School of Optometry & Vision Science, Queensland University of Technology, Brisbane, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Atchison
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Crete, Greece.
authors.forename: Stella
authors.initials: S
authors.lastname: Blazaki
authors.affiliation: Institute of Health & Biomedical Innovation, School of Optometry & Vision Science, Queensland University of Technology, Brisbane, Australia.
authors.forename: Marwan
authors.initials: M
authors.lastname: Suheimat
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Crete, Greece.|Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Sotiris
authors.initials: S
authors.lastname: Plainis
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: W Neil
authors.initials: WN
authors.lastname: Charman
mesh_terms: D000328:Adult; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D008962:Models, Theoretical; D055095:Optics and Photonics; D011305:Presbyopia / Q000503:physiopathology* / Q000628:therapy; D011680:Pupil / Q000502:physiology*; D014786:Vision Disorders / Q000503:physiopathology*; D014785:Vision, Ocular; D014792:Visual Acuity; D014794:Visual Fields / Q000502:physiology*
keywords: KAMRA inlay; depth-of-focus; presbyopia; small-aperture optics; visual field