A study on the effect of the corneal biomechanical properties undergoing overnight orthokeratology
To evaluate the changes of corneal biomechanical properties and corneal topography undergoing overnight orthokeratology treatment.
Thirty teenagers with low and moderate myopia with age of 11.67 + or - 1.63, myopia (-2.56 + or - 0.86) D, were included and were fitted with Ortho-K CL. The corneal biomechanical properties, including corneal hysteresis (CH), corneal resistance factor (CRF), goldmann-correlated IOP (IOPg) and corneal-compensated intraocular pressure (IOPcc) were measured with ocular response analyzer (ORA). Corneal topography, central corneal thickness (CCT) and corneal endothelium density were measured with computerized corneal topography, optical coherence tomography (OCT) and non contact specular microscope respectively. The measurements were taken at pre-wear, 1 day and 7, 30, 90, 180 days after orthokeratology. Only data from the right eyes were analysed.
All subjects were significantly reduced the myopia amount after 1 day of lens wear. The corneal curvature flattening (F = 38.837, P < 0.01) became slightly down to stable after the first week. There were significant decrease in CH and CRF after the orthokeratology treatment within the first week, and CH and CRF reversed and thereafter into the original level at 3-month and 6-month follow up. IOPg and IOPcc decreased and reached the lowest level at 1-week visit and after then became down to stable. There were significant reduction in CCT after 1 week (F = 4.739, P < 0.05). There were no significant changes in corneal endothelium density during orthokeratology treatment for 6 months.
The amount of myopia reduction with orthokeratology occurred mostly within 1 week while the corneal biomechanical properties such as CH and CRF were decreased. However the corneal biomechanical properties are reversal to the original level thereafter and remain unchanged within the 6 months follow up visits. It proves that orthokeratology does not damage corneal microstructure. The early sign of reduction may due to the temporal response to the reshaping of the cornea.
Available from: António Queirós
- "In another study, during short-term OK treatment, CRF was shown to decrease with increasing duration of lens wear, while there was no significant change in CH . On the other hand, a significant decrease in CH and CRF was reported within the first week of OK treatment . However, CRF and CH returned to original values and remained unchanged thereafter. "
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ABSTRACT: Several refractive and therapeutic treatments as well as several ocular or systemic diseases might induce changes in the mechanical resistance of the cornea. Furthermore, intraocular pressure measurement, one of the most used clinical tools, is also highly dependent on this characteristic. Corneal biomechanical properties can be measured now in the clinical setting with different instruments. In the present work, we review the potential role of the biomechanical properties of the cornea in different fields of ophthalmology and visual science in light of the definitions of the fundamental properties of matter and the results obtained from the different instruments available. The body of literature published so far provides an insight into how the corneal mechanical properties change in different sight-threatening ocular conditions and after different surgical procedures. The future in this field is very promising with several new technologies being applied to the analysis of the corneal biomechanical properties.
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