title: The effect of cycloplegia on measurement of the ocular components.
abstract: OBJECTIVE
  The purpose of this study was to examine the effect of cycloplegic agent on the measurement of refractive error and the ocular components.
  
  
  METHODS
  We compared two commonly used topical cycloplegic agents, 1% tropicamide and 1% cyclopentolate, for their effect on the measurement of refractive error (by Canon R-1 autorefraction), accommodative response (by Canon R-1 autorefraction and by the conventional, subjective "pushup" method), crystalline lens power (by video phakometry and by calculation), and axial ocular dimensions (by A-scan ultrasonography) in 20 emmetropic to moderately hyperopic children.
  
  
  RESULTS
  Comparison of refractive error at each drug's reported time of maximum cycloplegia (30 minutes for tropicamide and 60 minutes for cyclopentolate) showed that distance autorefraction in the vertical meridian differed by +0.20 +/- 0.30 diopters (D) (P = 0.008). The average difference was +0.07 +/- 0.10 mm for anterior chamber depth (P = 0.004), -0.03 +/- 0.05 mm for crystalline lens thickness (P = 0.025), -0.65 +/- 0.69 D for phakometrically measured crystalline lens power (P < 0.001), +0.03 +/- 1.55 D for calculated crystalline lens power (P = 0.94), and -0.09 +/- 0.19 mm for vitreous chamber depth (P = 0.062, all paired t tests; positive signs denote greater values with cyclopentolate). Residual accommodation was 0.47 and 0.67 D greater with tropicamide when measured by autorefraction and the pushup method (P = 0.013 and 0.08 respectively, paired t test). All significant differences were consistently in the direction of poorer cycloplegia with tropicamide.
  
  
  CONCLUSIONS
  Although tropicamide, as expected, showed poorer cycloplegia compared to cyclopentolate, the degree of difference appeared to be small, with minimal effect on the measurement of distance refractive error and the ocular optical components.
authors.affiliation: School of Optometry, University of California, Berkeley 94720.
authors.forename: D O
authors.initials: DO
authors.lastname: Mutti
authors.forename: K
authors.initials: K
authors.lastname: Zadnik
authors.forename: S
authors.initials: S
authors.lastname: Egashira
authors.forename: L
authors.initials: L
authors.lastname: Kish
authors.forename: J D
authors.initials: JD
authors.lastname: Twelker
authors.forename: A J
authors.initials: AJ
authors.lastname: Adams
mesh_terms: D000065:Accommodation, Ocular / Q000187:drug effects*; D000328:Adult; D002648:Child; D002924:Ciliary Body / Q000187:drug effects / Q000502:physiology*; D003519:Cyclopentolate / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007908:Lens, Crystalline / Q000187:drug effects / Q000502:physiology; D009883:Ophthalmic Solutions; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000503:physiopathology*; D015203:Reproducibility of Results; D014331:Tropicamide / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D009883:Ophthalmic Solutions; D003519:Cyclopentolate; D014331:Tropicamide