Night Of Lens Wear Research Articles

Changes in corneal thickness, corneal volume, and densitometry after long-term orthokeratology wear

PurposeTo investigate changes in the corneal volume, corneal densitometry and pachymetry of young myopes wearing over-night orthokeratology (OK) contact lenses. MethodsThe medical records of 28 right eyes of young myopes wearing OK between 2013 and 2018 were reviewed retrospectively. The baseline refractive error, best corrected visual acuities at baseline and uncorrected visual acuity at the most recent visit were recorded. Corneal volume of the central 10 mm cornea; densitometry at central, nasal and temporal cornea; and pachymetry along the horizontal and vertical meridians were collected from the Pentacam® HR at baseline, after one night of lens wear, and at the latest visit. ResultsThe mean age of subjects was 12.03 ± 3.80 years at the time of OK lens fitting and wore OK overnight for a mean duration of 666 days (range 206–1736 days). The baseline spherical equivalent refractive error was −3.03 ± 1.56 D (range −1.00 to −6.00 D). The corneal volume increased significantly after OK wear (p = 0.001). Corneal densitometry increased after OK wear, but the change did not reach statistical significance (p = 0.113). Pachymetry in the central cornea did not change significantly across all visits (p > 0.05) but increased significantly in the mid-peripheral regions of the cornea. Baseline refractive error was not found to be correlated with the changes in corneal volume, corneal densitometry, or pachymetry. ConclusionThe increase in corneal volume and densitometry and no significant change in the central corneal thickness may indicate the presence of corneal oedema from long-term OK wear. The baseline refraction was not correlated with the changes in corneal volume, densitometry or pachymetry.

Refractive error, visual acuity, and corneal-curvature changes in high and low myopes with orthokeratology treatment: A Malaysian study

Background/PurposeThe effect of orthokeratology (OK) on low myopia is well known, but there are a few reports on its effect on high myopia. In this study, the parametric changes in high and low myopia as results of wearing OK lenses for a period of 6 months have been analyzed. MethodsRecords of schoolchildren (age 7–17 years) undergoing OK treatment from an optometry clinic were retrospectively reviewed. Data involving refractive errors, uncorrected visual acuity, and corneal curvatures at baseline and after 1 day, 1 week, 1 month, 3 months, and 6 months of OK treatment from 25 patients who fulfilled the inclusion criteria were examined. For the analysis, the participants were arbitrarily divided into two groups comprising high myopia (< −6.00 D) and low to moderate myopia (from −1.00 D to −6.00 D). ResultsSignificant reductions of refractive error, improvement in visual acuity, and corneal-curvature flattening were found in all participants after 6 months of OK lens wear compared to the baseline. No significant changes were found in corneal toricity in both high and low to moderate myopic groups. Almost all of these occurred after one night of lens wear in both the high- and low-myopia groups. ConclusionThe OK lens wear significantly reduced the refractive error and corneal curvature that results in the improvement in visual acuity in both high- and low-myopia groups, and the reduction seemed to occur nearly at the same time despite the difference in initial myopic power. High myopes with refractive power up to −8.25 D would benefit significantly from OK lenses.

Vertical and Horizontal Thickness Profiles of the Corneal Epithelium and Bowman's Layer after Orthokeratology

To investigate thickness profile changes of the corneal epithelium and Bowman's layer at the vertical and horizontal meridians with overnight myopia orthokeratology (OK) lenses. Twenty subjects (age range: 19-33 years) wore reverse-geometry rigid gas-permeable OK lenses in both eyes for 30 days. Before lens wear and after 1, 7, and 30 days of overnight lens wear, evaluation of lens fitting, visual acuity examination, corneal topography, and ultra-high resolution optical coherence tomography (UHR-OCT) were performed. The central, midperipheral, and peripheral cornea were imaged in both the horizontal and vertical meridians. Custom software was produced to acquire the thickness profiles of the epithelium and Bowman's layer. Unaided visual acuity and refraction were improved significantly after OK lens wear. The central corneal epithelium thinned in the horizontal and vertical meridians after one night of lens wear (P < 0.05). In the horizontal meridian, the epithelium thickened at the temporal and nasal midperipheries (P < 0.05), while the superior midperipheral epithelium thinned in the vertical meridian. There were no changes in the thickness profile of Bowman's layer during the study period. Overnight wear of OK lenses caused the central corneal epithelium to thin in both the vertical and horizontal meridians, while the midperipheral nasal and temporal epithelium became thicker and the superior midperipheral epithelium became thinner. The thickness of the central or midperipheral Bowman's layer in either meridian did not change. Improved vision acuity after overnight OK lens wear can be attributed to changes in the corneal epithelium and not Bowman's layer.

Corneal Refractive Therapy Gas Permeable Lenses for the Correction of Hyperopia After One Night of Lens Wear

To examine the refractive and keratometric response of corneal refractive therapy (CRT) contact lenses for hyperopia (CRT) after a single night of contact lens wear with the goal of reducing hyperopia by +3.50 D. Twenty participants were fitted with a CRT HDS 100 contact lens, in one eye only. The back optic zone radius of the CRT lens was designed to correct 3.50 D of hyperopia. The eyes were randomly selected. The Nikon Auto Refractor was used to measure refractive error. Corneal topography and simulated K readings were measured using the Humphrey Atlas topographer. The lens was subsequently worn overnight, and the lens was assessed the next morning on awakening. Refractive error changed by 1.50±0.71 D (mean ± SD, range 0.50-2.75 D) immediately after lens removal in the experimental eye. Similarly, there was a change in flat K readings of 0.58±0.62 D with a range of -0.25 to +1.87 D. These results were significantly different from the baseline measurements (P<0.0001). The fitting of CRT HDS for hyperopia has a significant effect on corneal shape and refractive error. There was a moderate yet significant steepening of the cornea.

Corneal Changes and Wavefront Analysis after Orthokeratology Fitting Test

To evaluate corneal changes and ocular aberrations during an orthokeratology test. A prospective, nonrandomized cohort study. Fourteen myopic patients (26 eyes) underwent an orthokeratology fitting test with the BE contact lens (Ultravision Pty, Ltd, Brisbane, Australia). Best spectacle-corrected visual acuity (BSCVA), uncorrected (Ultravision Pty, Ltd, Brisbane, Australia) visual acuity (UCVA), subjective cycloplegic refraction, biomicroscopy, corneal topography, optical pachymetry, and aberrometry were performed at baseline and one and eight nights orthokeratology. The short-term effect of orthokeratology using corneal topography, tomography, and ocular aberrations was evaluated. The mean spherical equivalent changed from -2.24 +/- 0.98 diopters (D) at baseline to 0.15 +/- 0.76 D after the eight nights of lens wear (P = .001). All patients had an UCVA of 20/30, 69.2% with 20/20. Changes in central corneal pachymetry were not observed. There was a statistically significant increase in the temporal corneal thickness from night one, without any difference between nights one and eight (P > .001). A significant increase of higher-order root mean square values was observed from baseline (0.42 +/- 0.16 mum), night one (0.81 +/- 0.24 mum), and night eight (1.04 +/- 0.24 mum). Increases in coma (Z7+Z8) and spherical aberration (Z12) were observed. Positive horizontal (Z8) coma increased in right eyes, and negative horizontal (Z8) coma increased in left eyes (P < .001). Myopia reduction resulting from rapid central corneal flattening and improvement of UCVA occurred after orthokeratology. Higher-order aberrations (HOAs), particularly spherical aberration and coma, increased significantly during the orthokeratology test. An increase of temporal pachymetry and differences in coma direction induced between the eyes may be related to the subclinical lens decentration temporally.

Empirical Versus Trial Set Fitting Systems for Accelerated Orthokeratology

To compare the short-term clinical performance of two reverse-geometry rigid contact lens systems for accelerated orthokeratology with different fitting approaches and designs: an experimental lens that was fitted empirically (No. 7 Contact Lens Laboratory, Ltd.) and a more established lens using a trial set system, the BE lens (NKL). Twenty-four subjects were enrolled in a clinical study in which the two reverse-geometry lenses were worn contralaterally for seven nights. The No. 7 lens was manufactured based on subject keratometric readings, refraction, and horizontal visible iris diameter. The BE lens was fitted in accordance with fitting guidelines provided by the manufacturer and included the use of proprietary computer software in addition to an overnight trial before lens ordering. Data were collected at baseline, day 1, and day 7 (morning and afternoon). Unaided visual acuity, best-corrected visual acuity, subjective refraction, corneal topography, biomicroscopy (corneal staining), and subjective reaction were recorded at each visit. Nine subjects (18 eyes) completed the study. All eyes fitted with the No. 7 lens and 67% of the eyes fitted with the BE lens were within +/-1.00 diopter of the attempted correction after seven nights of lens wear. There was more myopic reduction (F = 16.2, P=0.0002), better unaided high-contrast visual acuity (F = 8.7, P=0.005) and low-contrast visual acuity (F = 9.5, P=0.003), and more change in corneal numerical eccentricity (F = 8.6, P=0.005) with the BE lens than with the No. 7 lens. There were no significant differences between the lenses for best-corrected visual acuity, change in apical radius, corneal staining, and subjective reaction. Both lens types investigated in this study were effective in temporarily reducing myopia and in providing good unaided visual acuity during the day (without lenses) in subjects with low levels of myopia. Subjective reaction showed that the lenses were perceived as being equally effective, but clinical data showed that the BE lens effected more myopic reduction and better unaided visual acuity than did the No. 7 lens during the 7-day period investigated.

Topographical Thickness of the Epithelium and Total Cornea after Overnight Wear of Reverse-Geometry Rigid Contact Lenses for Myopia Reduction

To investigate topographical thickness changes of the epithelium and total cornea measured with optical coherence tomography (OCT) after overnight wear of rigid gas-permeable lenses. Reverse geometry design CRT (Dk=100) rigid (test) lenses (Paragon Vision Sciences, Mesa, AZ) were randomly fitted on one eye of each of 20 neophyte subjects (mean age, 24.6 +/- 2.7 years) and the other eye was fitted with an alignment tricurve rigid lens of the same material (control). Epithelial and total corneal thickness was measured at intervals of 10 degrees across a 10-mm zone of the horizontal meridian of the cornea, before and after overnight wear. Refractive error was measured with an autorefractor. These measurements were repeated 20 and 60 minutes and 3, 6, and 12 hours after lens removal. After one night of lens wear, myopia decreased in the test eye by 1.18 +/- 0.81 D, which was significantly different from baseline (P<0.001). No significant change was found in the control eye. Twelve hours after removal, two thirds of the myopic reduction was still present. Different topographical swelling patterns were induced by the two lens designs, with greatest swelling occurring in the center with the control lens and in the midperiphery with the test lenses (polynomial regression: P<0.005). Significantly greater central corneal swelling was found with the control lens than the test lens (6.9% +/- 3.1% vs. 4.9% +/- 2.0%, respectively, P=0.006). The effect on epithelial thickness differed between lenses and depended on both position and time (F(48,912)=2.3; P=0.000). Immediately after removal of the test lens, the central epithelium was 5.1% +/- 4.5% thinner than baseline, and all other locations (P<0.005 post hoc tests) and the epithelium in the midperiphery showed significant thickening (1.9% on the temporal side and 2.4% on the nasal side, both P<0.006 compared with the baseline). There were no significant changes in epithelial thickness with the control lens during the study period (post hoc tests: P>0.05). The optical coherence tomograph is a sensitive instrument that can detect small changes in epithelial and corneal thickness across the entire cornea. Topographical thickness changes of the epithelium and total cornea induced by one night of reverse-geometry lens wear appear to be associated with the decrease of myopia.