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Study suggests full reversibility of tear film response to ortho-K
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Long-term hydrogel and orthokeratology lens wear led to an increase in tear film osmolarity compared to spectacle wear, but osmolarity returned to lower-than-baseline levels 1 month after treatment ceased.
This study designed as two experiments was published in Eye & Contact Lens.
In the first experiment, tear film osmolarity (TFO) measurements were taken in 77 right eyes of 23 non-contact lens wearers, 26 hydrogel wearers and 28 overnight orthokeratology (ortho-K) contact lens wearers with the TearLab osmolarity system.
In the second experiment, a prospective, longitudinal, single-center study, 31 habitual soft contact lens wearers were evaluated for long-term TFO response to ortho-K treatment.
TFO measurements were compared at baseline, 1 month and 1 year after starting ortho-K treatment and 1 month after ortho-K treatment cessation. Participants were fitted with HDS 100 Paragon-CRT (Paragon Vision Sciences) or Seefree lenses made of Boston XO2 material (Conóptica), and TFO readings were recorded at baseline and after 1 month and 1 year of lens wear and after 1 month of ortho-K treatment interruption, according to the study.
Inclusion criteria after a full eye examination included participants 18 to 30 years of age with -0.50 D to -5.00 D of sphere, -0.25 D to -1.25 D of cylinder and monocular best-corrected visual acuity of at least 0.04 logMAR.
Participants in the hydrogel group had been wearing hydrogel daily disposable lenses for at least 3 years before study commencement.
Researchers identified significant differences in TFO among groups. The higher TFO values were observed in ortho-K and hydrogel lens wearers than in non-contact lens wearers, and values were higher in the ortho-K group than in the hydrogel group.
They also determined that mean sphere magnitudes and sphere equivalents decreased significantly during ortho-K wear, whereas refractive cylinder values remained unchanged in both the Paragon CRT and Seefree groups. After 1-year of ortho-K treatment, central corneal power was significantly reduced at both the steeper and flatter meridians, according to researchers.
Measurements of TFO were within normal limits during follow-up in both ortho-K treatment groups. Osmolarities varied significantly at baseline between the Paragon-CRT and Seefree groups at 299.9 mOsm/L versus 288.5 mOsm/L, respectively. TFO was significantly lower at the final time point after lens wear cessation than at the remaining time points.
“It is reasonable to assume that this higher TFO could be attributed to contact lens wear,” the researchers stated.
Unexpectedly, the two groups differed significantly in TFO at baseline, according to researchers. Paragon-CRT wearers showed the higher mean value. The researchers proposed that the washout period was not long enough, or the subjects may have failed to comply with the stipulated wash-out period.
“The low TFO levels were comparable to the osmolarities observed in non-contact lens wearers and suggest the full reversibility of the corneal response to orthokeratology treatment,” researchers wrote. – by Abigail Sutton
Disclosures: Interlenco and Conóptica provided the ortho-K lenses used in this study, and Avizor provided the lens cleaning solutions and lubricant eye drops. The authors reported no relevant financial disclosures.
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