Overnight orthokeratology causes rapid central corneal epithelial thinning and midperipheral stromal thickening. The consequent change in corneal sagittal height is the primary factor underlying the refractive effect of orthokeratology.

No abstract

Both the PRT and Schirmer tests displayed good repeatability; however, there was a poor correlation between the tests, as reported previously. The mean PRT value in normal Saudis was higher, when compared with those reported previously for other ethnic groups.

KeraRing (A) and MyoRing (B) corneal implants both performed well in improving vision and stabilising the cornea. Implantation of the MyoRing caused greater reduction in coma and better patient satisfaction, but CDVA improved only in the Keraring group, at the final visit.

We found that the average osmolarity for subjects living in Saudi Arabia was 299.06±7.65 mOsm/L, which falls within the reference range and is in agreement with published results (298.0-301.9±7.2-16.0 mOsm/L). Osmolarity was positively correlated with McMonnies questionnaire and negatively correlated with TBUT values. The TearLab osmolarity system test showed good precision in repeated measurements. This is the first report of use of the TearLab osmolarity system to assess tear film in normal Saudi adults.