title: Sagittal height differences of frequent replacement silicone hydrogel contact lenses.
abstract: OBJECTIVE
  This study aims to evaluate the sagittal height differences among a selection of commercially available monthly or two weekly replacement silicone hydrogel soft lenses.
  
  
  METHODS
  The sagittal height (CL-SAG) of four frequent replacement silicone hydrogel lenses (lotrafilcon B, balafilcon A, comfilcon A and senofilcon A) was measured for all base curve radius manufactured in spherical (-3.00D and +3.00D) and toric (=C-0.75×180°) designs (11 spherical and 8 toric lenses in total). Two different lenses of each lens type were evaluated (the intra CL-SAG) using the SHSOphthalmic omniSpect by Optocraft.
  
  
  RESULTS
  The intra CL-SAG difference (the difference between two identical lenses from the same batch) was 11±SD 2μm. The CL-SAG of all minus lenses ranged from 3454 to 3765μm (an inter CL-SAG difference of 311μm), while the plus spherical lenses ranged from 3493 to 3757μm (inter CL-SAG difference 264μm). In the toric lens group, the range in toric minus lenses was 3495-3953μm (inter CL-SAG difference 458μm) and 3493-3980μm in the plus group (inter CL-SAG difference 487μm). The inter CL-SAG difference between the spherical and the toric lenses was statistically significant (p=0.03).
  
  
  CONCLUSIONS
  Marked differences in sagittal height among different commercially available frequent replacement silicone hydrogel lenses exist. Different lenses with the same package base curve value had marked differences in CL-SAG, with potential clinical significance on-eye in terms of lens behavior. The inter CL-SAG variance in the spherical lens group was smaller than in the toric lens group.
authors.affiliation: University of Maastricht, Maastricht, The Netherlands. Electronic address: eefvanderworp@netherlens.com.
authors.forename: Eef
authors.initials: E
authors.lastname: van der Worp
authors.affiliation: Microlens Contact Lens Technology, Arnhem, The Netherlands.
authors.forename: Cristian
authors.initials: C
authors.lastname: Mertz
mesh_terms: D003263:Contact Lenses, Hydrophilic; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D012826:Silicone Elastomers; D013499:Surface Properties
chemical_list: D012826:Silicone Elastomers
keywords: Base curve radius; Frequent replacement; Lens fitting; Sagittal height; Silicone hydrogels; Soft contact lenses