title: Visual acuity vs letter contrast sensitivity in retinitis pigmentosa.
abstract: This study examined the quantitative relationship between foveal visual acuity and contrast sensitivity for large-letter optotypes in a group of patients with retinitis pigmentosa (RP), in order to assess more completely the extent of foveal vision loss in this group of hereditary retinal dystrophies. High-contrast visual acuity and large-letter contrast sensitivity were measured with a computer-based testing system and with commercially available letter charts (Lighthouse Distance Visual Acuity Test; Pelli-Robson Contrast Sensitivity Chart). Findings from 20 patients with typical RP or Usher syndrome were compared with those from 15 age-similar control subjects with normal vision. On both the computer-based test and the chart tests, the patients with RP showed approximately equal reductions in visual acuity and large-letter contrast sensitivity. However, intersubject controls was greater for contrast sensitivity than for visual acuity on both test protocols. As a result, the patients with RP required a greater reduction in contrast sensitivity than in acuity to exceed the normal range, indicating that visual acuity was the more sensitive index of the loss of foveal visual function.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine 60612, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Alexander
authors.forename: D J
authors.initials: DJ
authors.lastname: Derlacki
authors.forename: G A
authors.initials: GA
authors.lastname: Fishman
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D005584:Fovea Centralis / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012174:Retinitis Pigmentosa / Q000503:physiopathology* / Q000523:psychology*; D012684:Sensory Thresholds / Q000502:physiology; D014787:Vision Tests / Q000379:methods; D014792:Visual Acuity / Q000502:physiology*