Overnight Orthokeratology Lens Wear Research Articles

Myopia Control during Orthokeratology Lens Wear in Children Using a Novel Study Design

To investigate the effect of overnight orthokeratology (OK) contact lens wear on axial length growth in East Asian children with progressive myopia. A prospective, randomized, contralateral-eye crossover study conducted over a 1-year period. We enrolled 26 myopic children (age range, 10.8-17.0 years) of East Asian ethnicity. Subjects were fitted with overnight OK in 1 eye, chosen at random, and conventional rigid gas-permeable (GP) lenses for daytime wear in the contralateral eye. Lenses were worn for 6 months. After a 2-week recovery period without lens wear, lens-eye combinations were reversed and lens wear was continued for a further 6 months, followed by another 2-week recovery period without lens wear. Axial eye length was monitored at baseline and every 3 months using an IOLMaster biometer. Corneal topography (Medmont E300) and objective refraction (Shin-Nippon NVision-K 5001 autorefractor) were also measured to confirm that OK lens wear was efficacious in correcting myopia. Axial length elongation and myopia progression with OK were compared with conventional daytime rigid contact lens wear. After 6 months of lens wear, axial length had increased by 0.04±0.06 mm (mean±standard deviation) in the GP eye (P=0.011) but showed no change (-0.02±0.05 mm) in the OK eye (P=0.888). During the second 6-month phase of lens wear, in the OK eye there was no change from baseline in axial length at 12 months (-0.04±0.08 mm; P=0.218). However, in the GP eye, the 12-month increase in axial length was significant (0.09±0.09 mm; P<0.001). The GP lens-wearing eye showed progressive axial length growth throughout the study. These results provide evidence that, at least in the initial months of lens wear, overnight OK inhibits axial eye growth and myopia progression compared with conventional GP lenses. Apparent shortening of axial length early in OK lens wear may reflect the contribution of OK-induced central corneal thinning, combined with choroidal thickening or recovery due to a reduction or neutralization of the myopiogenic stimulus to eye growth in these myopic children.

The Effects of Overnight Orthokeratology Lens Wear on Ocular Scatter

Purpose: To evaluate the change of visual quality after wearing orthokeratology lenses overnight. Methods: This study included 13 patients (24 eyes) who wore orthokeratology lenses for the first time. Visual quality was assessed with the optical quality analysis system (OQAS) using the double-pass technique. The value of modulation transfer function (MTF) cutoff, Strehl ratio, and objective scatter index (OSI) were measured at baseline and 4 weeks after wearing the lenses. Results: The mean spherical equivalent decreased from -2.70 ± 1.03 diopters (D) to 0.03 ± 0.36 D after 4 weeks of wearing orthokeratology lenses and uncorrected visual acuity improved from log MAR 0.88 ± 0.17 to log MAR 0.03 ± 0.04. The MTF cutoff decreased from 38.20 ± 11.01 to 34.79 ± 10.30 and the Strehl ratio decreased from 0.24 ± 0.07 to 0.21 ± 0.07 but without statistical significance. The OSI significantly increased from 0.38 ± 0.19 to 0.72 ± 0.40 after wearing orthokeratology lenses. Conclusions: Orthokeratology lenses were effective for correction of myopia and astigmatism. The OSI increased after wearing the lenses, but MFT cutoff and Strehl ratios were not affected. J Korean Ophthalmol Soc 2014;55(11):1595-1599

Persistent corneal epitheliopathy after discontinuation of overnight orthokeratology lens wear: a case report

Purpose: To report an unusual case of persistent corneal epitheliopathy after ceasing orthokeratology lens wear in a Chinese patient.

Posterior Corneal Shape Changes in Myopic Overnight Orthokeratology

To evaluate changes in the shape of the posterior cornea at the end of the day based on anterior corneal topography and corneal thickness during myopic overnight orthokeratology (OK) over 14 nights' wear of reverse geometry gas-permeable (GP) contact lenses. Eighteen subjects (aged 19 to 32 years) with low myopia and astigmatism were fitted with reverse geometry lenses (BE; Capricornia Contact Lens Pty Ltd) for myopic OK, which were worn overnight only for a 14-day period. A separate group of 10 subjects (aged 19 to 32 years) with low astigmatism wore J-Contour conventional GP lenses (Capricornia Contact Lens Pty Ltd) for one night. Corneal topography (Medmont E-300) and total corneal thickness (Holden-Payor optical pachometer) across the horizontal meridian were measured at baseline and approximately 8 to 10 hours after lens removal on days 1, 4, 7, and 14 of overnight OK lens wear and after one night of GP lens wear for the control group. Posterior corneal apical radius of curvature and asphericity (Q) were calculated using an in-house program based on the anterior corneal ellipse curve and corneal thickness. Myopia reduced from -2.64 ± 0.99 diopters (mean ± SD) to -0.39 ± 0.49 diopters during 14 days of overnight OK lens wear. In the OK lens-wearing eyes, there were no statistically significant changes in posterior corneal apical radius of curvature during 14 days of overnight OK. However, there were statistically significant increases in posterior corneal Q on days 4 and 7. In the conventional GP lens-wearing eyes, there were no statistically significant changes in either posterior corneal apical radius or Q after overnight lens wear. The results of this study support the current hypothesis that the OK refractive effect is achieved primarily through remodeling of the anterior corneal layers, without overall corneal bending.

Lens Dk/t Influences the Clinical Response in Overnight Orthokeratology

To investigate the influence of lens oxygen transmissibility (Dk/t) on the clinical response to overnight (ON) orthokeratology (OK) lens wear over 2 weeks. Eleven subjects (age, 20 to 39 years) were fitted with OK lenses (BE; Capricornia Contact Lens) in both eyes. Lenses in matched design/fitting but different materials (Boston EO and XO; nominal Dk/t: 26 and 46 ISO Fatt, respectively) were worn ON only in the two eyes over a 2-week period. Changes in logarithm of the minimum angle of resolution visual acuity, subjective refraction (spherical equivalent), corneal apical radius ro and asphericity Q (Medmont E300), and central stromal thickness (Holden-Payor optical pachometer) were measured. There were statistically significant differences in outcomes between the two lens materials (analysis of variance, p < 0.001) throughout the study. After 2 weeks of ON OK lens wear, changes from baseline (mean ± standard deviation) with the EO lenses were significantly less than XO for visual acuity (-0.72 ± 0.37 vs. -0.83 ± 0.41; p = 0.012), refraction [+2.19 ± 0.73 diopter (D) vs. +2.74 ± 0.70 D; p = 0.004], ro (0.34 ± 0.08 mm vs. 0.46 ± 0.11 mm; p < 0.001), and Q (0.26 ± 0.08 vs. 0.36 ± 0.08; p < 0.001). After the first ON OK lens wear, change in central stromal thickness was greater for EO compared with XO (27 ± 36 μm vs. 10 ± 31 μm; p = 0.05), but ON edema was reduced after 2 weeks for both lens materials (8 ± 25 μm vs. -1 ± 33 μm; p > 0.05). An increase in lens Dk/t appears to increase the clinical effects of ON reverse-geometry lens wear over the medium term. This adds further support to the recommendation that high Dk materials should be used for ON OK not only to provide physiological advantages but also to optimize clinical outcomes.

Histomorphometric Profile of the Corneal Response to Short-term Reverse-geometry Orthokeratology Lens Wear in Primate Corneas

To investigate the histological changes in primate cornea induced by short-term overnight orthokeratology (OK). Nine young adult primates were used. One animal served as negative control. The remaining 8 animals wore reverse-geometry OK lenses for periods of 4, 8, 16, and 24 hours on 1 eye with the other eye as control. Central and midperipheral corneal thickness, as well as ultrastructural changes in corneal epithelium, stroma and endothelium in response to OK lenses, were evaluated. OK significantly reduced the thickness of the central cornea in all treatment groups. The central corneal thinning was both stromal and epithelial in origin. Substantial midperipheral corneal thickening was seen in 16-hour and 24-hour lens-wear groups and this effect was both stromal and epithelial in origin as well. Histology evidence indicated the primary epithelial response in the central cornea was compression of cells that resulted in wing cells becoming shorter and basal cells being squatted rather than lost or migration of cell layers. These pronounced cell shape changes occurred without compromising the structural integrity of the desmosomes. The thickened corneal epithelium has normal cell layers. The squamous cells have larger surface sizes and are composed of oval instead of flattened nuclei. This implied delayed surface cell exfoliation at the thickened midperipheral epithelium. Physical presence of OK lens over the cornea did not influence the microstructures of microvilli and microplicae, endothelium, and collagen distribution. The primate cornea, particularly the corneal epithelium, responds rapidly to the application of reverse-geometry OK lenses with significant epithelial cell shape alterations with short-term OK lens wear. This finding suggests that the corneal epithelium is moldable in response to the physical forces generated by the OK lenses.

Corneal foreign body injury during overnight orthokeratology lens wear: A case report

Purpose A case of asymptomatic corneal foreign body injury during orthokeratology lens wear is reported. Case report An 8-year-old Chinese female myopic child with 21 months of overnight orthokeratology lens wear experienced a corneal foreign body injury without symptoms. The foreign body was removed and the eye treated with prophylactic antibiotic and ocular lubricant. Orthokeratology treatment was resumed 4 weeks after initial detection and management and a small residual corneal scar remained. Discussion The mechanisms, differential diagnoses, management and role of neural sensitivity in corneal foreign body injury during orthokeratology lens wear are discussed. Clinicians should be aware that subtle corneal insult may be without symptoms during prolonged overnight orthokeratology lens wear.

Changes in the Anterior and Posterior Radii of the Corneal Curvature and Anterior Chamber Depth by Orthokeratology

To investigate the mechanism of the refractive effect of orthokeratology by using measurements of the anterior and posterior radii of the corneal curvature and anterior chamber depth with a Pentacam analysis system. Nine women (18 eyes) with a mean age of 29.6+/-3.8 years and low to moderate myopia (<or=-4.00 diopters [D]) were recruited for a 53-week trial of overnight orthokeratology using RD171K lenses (hexafocon A). After wearing the orthokeratology lenses overnight, subjects were examined during the day. With a Pentacam analysis system, subjects were examined at 2, 4, 8, 12, 24, 36, and 53 weeks for the assessment of the anterior and posterior radii of the corneal curvature and anterior chamber depth. Myopic refractive error significantly reduced during the trial (P<0.001, analysis of variance). The mean refractive error was -2.85+/-0.46 D at baseline and significantly reduced to -0.28+/-0.65 D at 2 weeks (P<0.01, Bonferroni-Dunn post hoc test). At any week, no significant differences were seen in the central posterior radius of the corneal curvature (P=0.55, analysis of variance) or the anterior chamber depth (P=0.69, analysis of variance). The amount of change in the central anterior radius of the corneal curvature significantly correlated with the change in refractive error at 24 weeks (r=0.57, P<0.05, Pearson correlation coefficient). Overnight orthokeratology lens wear alters the anterior corneal shape rather than the posterior radius of the corneal curvature and the anterior chamber depth. This finding suggests that the primary factor in the refractive effect of orthokeratology is change in the anterior corneal shape rather than overall corneal bending.

Good Visual Outcome After Prompt Treatment of Acanthamoeba Keratitis Associated With Overnight Orthokeratology Lens Wear

To describe a patient with a good visual outcome after prompt treatment of Acanthamoeba keratitis as a complication of overnight orthokeratology lens wear. Interventional case report. A 9-year-old boy experienced pain, photophobia, and redness in his right eye 3 days after visiting a swimming pool. He had been wearing overnight orthokeratology lenses for 5 months for the correction of moderate myopia in both eyes. On examination, best-corrected visual acuity in the right eye was 20/40. A diagnosis of Acanthamoeba keratitis with the presence of the classic feature of perineural infiltrates was made. The patient responded well to treatment with polyhexamethylene biguanide and propamidine isethionate (Brolene). Culture of corneal scrapings and contact lens solution showed heavy growth of Acanthamoeba. Treatment was tapered gradually during the next 4 months, and the final best-corrected visual acuity was 20/25. Acanthamoeba keratitis may be a vision-threatening complication associated with overnight orthokeratology lens wear. It is essential for eye care professionals to fully explain and warn parents of the potential downsides that may be associated with orthokeratology. Ophthalmologists should have a high level of suspicion of this complication because prompt diagnosis and treatment can result in good visual outcome.

Stromal response to orthokeratology: an X‐ray diffraction study

Abstract Purpose: To examine the impact of overnight orthokeratology lens wear on stromal collagen fibril diameter and spacing using synchrotron X‐ray diffraction. Methods: Seven New Zealand White rabbits (10 eyes) wore orthokeratology lenses (Capricornia, Brisbane, Australia) overnight during a 2‐week period to determine the effect of corneal refractive therapy on stromal collagen fibrils. To verify the effectivity of treatment, corneal topography (Medmont, Brisbane, Australia), corneal thickness (Allergan Humphrey pachymetry) and refractive error (retinoscopy) were measured prior to and every 3‐4 days during the treatment period. Following completion of treatment, rabbits were euthanased and corneas immediately dissected and snap frozen for subsequent X‐ray diffraction analysis every 1mm over the central c.10mm horizontal corneal band. Results: Orthokeratology treatment induced an average change in refraction of 2.0 +/‐ 1.3DS, and a topography‐measured treatment zone diameter of 4.2 +/‐ 0.7mm. The results from X‐ray diffraction revealed no significant difference in collagen fibril diameter between treated and untreated eyes (p&gt;0.05). Interfibrillar spacing (IFS) was positively correlated with tissue hydration but no significant association between the change in IFS and refraction was apparent. Conclusions: The magnitude and time course of refractive change induced by orthokeratology in the rabbit eye is similar to that reported in humans, producing significant rapid and characteristic changes in corneal topography. Such specific changes in topography seem limited to the epithelial layers, with no parallel topographic modification evident in the underlying stromal architecture.

Fibrillary lines in overnight orthokeratology

This case report describes the appearance of fibrillary lines in the anterior stroma of a 39‐year‐old Asian woman wearing overnight orthokeratology (OK) lenses. The fibrillary lines were fine, slightly curved and sub‐epithelial, arranged in a band‐like annulus in the corneal mid‐periphery. The lines were not associated with epithelial staining, although a marked Fischer‐Schweitzer corneal mosaic was noted after blinking. Fibrillary lines are a relatively common finding in normal and keratoconic corneas and have been reported previously accompanying OK lens wear. Their origin is unknown and epithelial neural remodelling, corneal biomechanical stress and abrupt corneal curvature changes have been suggested as contributing factors. The appearance of fibrillary lines in our OK patient had no adverse consequences on vision or ocular health, at least in the medium term.

Infectious keratitis related to orthokeratology

To report 28 cases of infectious keratitis related to orthokeratology lens overnight wear in China. From March 2000 to August 2001, 28 cases of infectious keratitis related to overnight orthokeratology lens wear were diagnosed in Beijing Institute of Ophthalmology. These were retrospectively reviewed with regard to the pathogens isolated, duration of wear, the time since onset of symptoms, and age. Cultures of corneal scrapes for bacteria, fungus and Acanthamoeba were performed in all of the 28 cases. All cases were students, including 10 males and 18 females, average age was 16 years (range 10-21 years). The duration of orthokeratology overnight wearing was from 2 weeks to 2 years. Uncorrected visual acuity (UCVA) on initial examination in our institute was from 20/200 to light perception. Of 28 isolates, 24 were culture positive (including 11 bacteria, 11 Acanthamoeba and two fungi), and four were culture negative. In two of the four culture negative cases, Acanthamoeba cysts were detected in the corneal stroma with the confocal microscope. Acanthamoeba and Pseudomonas aeruginosa accounted for 75% (21 of 28) of the cases of infectious keratitis. Infectious keratitis is a severe complication associated with overnight orthokeratology lens wear. Ophthalmologists should pay more attention to this complication in practice.

Acanthamoeba keratitis as a complication of orthokeratology

Purpose To present four cases of Acanthamoeba keratitis as a complication of orthokeratology. Design Observational case report. Methods Four patients with Acanthamoeba keratitis had histories of overnight orthokeratology lens wear of 6 months to 2 years. Results Three cases were diagnosed with Acanthamoeba keratitis by corneal scraping and one by confocal microscopy examination. The patients were treated with chlorhexidine, metronidazole, and neomycin sulfate, resulting in a rapid resolution of ocular inflammation. Conclusion Overnight wear of orthokeratology lenses may induce Acanthamoeba keratitis.

The effects of overnight orthokeratology lens wear on corneal thickness.

To investigate corneal thickness changes during overnight orthokeratology with reverse-geometry rigid gas-permeable (RGP) contact lenses worn over a 3-month period. Eighteen young adult subjects with low myopia (<or=4.00 D) were fitted with reverse-geometry lenses (BE; UltraVision Pty. Ltd., Brisbane, Queensland, Australia), which were worn for 3 months on an overnight basis and were removed during the day. Another 10 subjects were fitted with conventional RGP lenses (J-Contour; UltraVision) that were worn for 1 month in the right eye on a similar wearing schedule; the left eye acted as a non-lens-wearing control. Refractive error was recorded in the morning and evening, and total, epithelial, and stromal corneal thicknesses were measured across the horizontal meridian with an optical pachometer. The orthokeratology group showed significant reductions in myopia (+1.66 +/- 0.50 D; P < 0.001) from day 1, which stabilized by day 10. Central corneal thinning (-9.3 +/- 5.3 microm, P < 0.001), which was epithelial in origin, was found from day 1; central stromal change was negligible. Midperipheral corneal thickening, which was stromal in origin, was confirmed by day 4 (+10.9 +/- 5.9 microm, P < 0.001). No change was found in peripheral corneal thickness. Analysis of day-90 data by Munnerlyn's formula indicated that corneal sagittal height change resulting from the thickness changes could account for the refractive effect. In the conventional RGP group, there were no significant changes in refractive error or corneal thickness. 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.