Abstract
Purpose :
Overnight orthokeratology (OK) effects include corneal tissue remodeling and refractive changes. OK outcomes might be influenced by corneal biomechanical factors and ethnicity. This preliminary study analyzed the effects of corneal refractive changes, biomechanical factors, and ethnicity on total corneal and epithelial thickness changes during short-term OK.
Methods :
15 subjects (8 Asian, 7 Non-Asian) with prescriptions of –1.00 D to –5.00 D and astigmatism up to -1.50 D wore GOV OK lenses for one night. Measurements of total corneal thickness and corneal epithelial thickness were taken using an Optovue RTVue XR optical coherence tomographer, and their changes were assessed in ring segments of 2 mm, 5 mm, 7 mm, and 9 mm. Corneal resistance factor (CRF) and corneal hysteresis (CH) were measured using an Ocular Response Analyzer. Corneal refractive power was measured using a Pentacam tomographer.
Results :
CRF and CH significantly impacted the corneal refractive power change. (P= 0.0018 and 0.0222, respectively). Following lens removal, the average diurnal regression of corneal refractive power was 0.49 D in the first hour, followed by a change of 0.16 D per hour for the next four hours, and then refractions leveled off at average values of -1.20 D. This was associated with concurrent changes in total corneal thickness and epithelial thickness changes, although the latter was less pronounced.
The influence of corneal refractive changes on the total corneal thickness was very strong (P< 0.0001) for all ring segments, while ethnicity did not have a significant influence. The influence of the corneal refractive changes and ethnicity on the epithelial thickness was only significant for the 2 mm ring (P = 0.0118 and 0.0016, respectively).
Conclusions :
Short-term corneal refractive power changes induced by overnight OK lenses were associated with total corneal thickness changes, which were statistically significant across the entire cornea, however, epithelial thickness changes were only significant at the 2-mm corneal center. This along with the achieved refractive changes suggests that the corneal stroma is the main contributor to these changes. Furthermore, the short-term changes were influenced by the CRF and the CH. Ethnicity did not influence overall corneal thickness changes but was significant for epithelial thickness changes in the 2-mm corneal center.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.