Assessment of the reliability (repeatability) of corneal thickness measurements in soft contact lens wearers using a non-contact specular microscope

Published:August 02, 2021DOI:


      • The most comprehensive assessment of in vivo pachymetry measures in contact lens wearers (76)
      • Non-contact specular microscopy can routinely yield central corneal thickness (CCT) values between 0.449 mm and 0.591 mm (98)
      • The average of 3 CCT measures can range from 0.458 mm to 0.589 mm.
      • The variance across 3 repeated measures was slightly higher in contact lens wearers.
      • This slight lower reliability of optical pachymetry in could be important in sample size calculations.



      To assess variability across 3 measures of central corneal thickness (CCT) obtained with a non-contact specular microscope and taken over a few minutes from habitual soft contact lens wearers.


      One eye from 200 healthy adults (with an average age of 21 y, half of whom had a 3.5 ± 2.1 year history of successful daily wear of soft contact lenses while the control group had nominally normal eyes) were assessed using the auto-focus Topcon 2000P instrument to obtain an image of the endothelium and CCT.


      The individual CCT values encountered in the 200 subjects ranged from 0.449 mm to 0.591 mm, with the average of 3 measures ranging from 0.459 to 0.591 mm in the control group and between 0.449 and 0.585 mm for the SCL wearers. The group mean CCT values were the same for both groups (at 0.524 mm), but the group mean SD value was marginally higher (at 0.028 mm) for the SCL group as compared to controls (SD = 0.026 mm). The normalized intra-subject variability (as the group-mean coefficient of variation, COV value) was 0.843 ± 0.401 for the control group and higher at 1.08 ± 0.546 for the SCL group (p < 0.001).


      Repeat measures of central corneal thickness, using a non-contact specular microscope, is very similar to those taken on age-matched non-contact lens wearers. These results may not equally apply to similar pachymetry measures in patients wearing RGP lenses or for older patients wearing soft contact lenses.


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