Gifford, Paul*; Swarbrick, Helen A.
This study reveiws the use of hyperopic overnight orthokeratology contact lenses over a 7 day period in an effort to restore near vision in prebyopic patients without glasses. Presbyopia is an age related condition which affects everyone and normally appears around the age of 40, leading to the need for reading glasses. Results showed that this was sufficient to provide functional correction of near vision. Lack of change in binocular distance showed that hyperopic OK offers a viable option for providing monovision correction in presbyopia.
It is worth noting that benefits for those approaching their 40's are already available in myopic overnight orthokeratology as it delays the need for reading glasses. This is because the flattening effect caused by the lens shape in the centre of the eye creates a raised plus prescription around the periphery of the pupil. The brain automatically knows to use the raised area for reading and the central area for distance. Uses can then move to monovison with this technique as their presbyopic prescription increases with age.
Purpose: To investigate the time course of refractive and corneal topographic changes in overnight hyperopic orthokeratology (OK) for emmetropic presbyopes.
Methods: Sixteen adult emmetropic presbyopic subjects were fitted with rigid hyperopic OK lenses (BE Enterprises, Brisbane, Australia/Capricornia, Slacks Creek, Australia) targeted to correct +2.00 D, in one eye only. The fellow eye acted as a non-lens-wearing control. Thirteen subjects completed the study. Lenses were worn overnight for a 7-day period, and changes in subjective refraction and corneal topography were measured in the morning on lens removal (A.M.) and 8 hr after lens removal (P.M.).
Results: There were statistically significant changes from baseline in all variables at all visits in lens-wearing eyes. Hyperopic OK caused a -1.00 (0.33) D shift in best vision sphere refraction at Day1 A.M., and -1.11 (0.61) D, at Day7 A.M., with -0.91 D of best vision sphere change from baseline still apparent by Day7 P.M. (mean [SD]). This led to an improvement in monocular near visual acuity (VA) from Jaeger 10.8 (2.4) at baseline to Jaeger 4.6 (2.5) at Day1 A.M., Jaeger 3.2 (2.3) at Day7 A.M., and Jaeger 3.9 (3.0) at Day7 P.M. Binocular distance VA did not change from baseline. The central cornea steepened, and the mid-peripheral nasal cornea flattened at lens removal after one night of wear. There was no significant difference in central corneal steepening between A.M. visits, but there was longer retention of effect by Day7 P.M. Nasal paracentral corneal flattening also showed a greater effect and longer retention of effect by Day7.
Conclusions: Hyperopic OK induced central corneal steepening and paracentral corneal flattening, which led to a monovision myopic shift in refraction that was sufficient to provide functional correction of near vision. Lack of change in binocular distance VA indicates that hyperopic OK offers a viable option for providing monovision correction in emmetropic presbyopia.
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