title: Improving detection of mild loss of retinal light increment sensitivity at the posterior pole with the microperimeter MP1.
abstract: OBJECTIVE
  With "standard" stimuli (white, Goldmann size III, 200 ms), the Nidek Microperimeter MP1 underestimates retinal light increment sensitivity (LIS). We thoroughly analyze this problem, suggest alternative settings to improve sensitivity to detect dysfunction, and provide true normal values.
  
  
  METHODS
  LIS was tested at 55 positions in the macular region using a 4-2-1 staircase strategy with 200 ms white or red stimuli on a 1.3 cd m⁻² background. Stimulus size was Goldmann III and I, and additionally II in the healthy subjects. All participants underwent a complete ophthalmologic examination, spectral domain optical coherence tomography (OCT), and fundus autofluorescence (FAF).
  
  
  RESULTS
  In normals, distributions of LIS for white Goldmann sizes II and III within the central 6° to 10° were clipped off at 20 dB--the MP1 cannot attenuate them any further. When the stimulus size was reduced to Goldmann I or the color changed to red, median LIS in the fovea (∼15 dB) was approximately 5 dB higher than at 10° eccentricity. Estimated from these results, central LIS for white Goldmann sizes II and III stimuli were 21 and 27 dB, respectively. In four patients with either focal or diffuse macular pathology, as confirmed by funduscopy, OCT, or FAF, reduced LIS was detected clearly with Goldmann size I stimuli, but not III.
  
  
  CONCLUSIONS
  In all subjects reported here, standard central LIS was above the technical limit of the MP1. To measure true thresholds in healthy subjects, either smaller (Goldmann size I) or dimmer stimuli (red) must be used.
authors.affiliation: Department of Ophthalmology, Justus-Liebig-University, Universitätsklinikum Giessen und Marburg GmbH, Giessen Campus, Giessen, Germany.
authors.forename: Wadim
authors.initials: W
authors.lastname: Bowl
authors.forename: Birgit
authors.initials: B
authors.lastname: Lorenz
authors.forename: Melanie
authors.initials: M
authors.lastname: Jäger
authors.forename: Christoph
authors.initials: C
authors.lastname: Friedburg
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000502:physiology*; D012164:Retinal Diseases / Q000175:diagnosis*; D012684:Sensory Thresholds / Q000502:physiology*; D041623:Tomography, Optical Coherence; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult
keywords: macula; microperimetry; perimetry; retinal light increment sensitivity; spatial summation