Topographical Thickness of the Epithelium and Total Cornea after Hydrogel and PMMA Contact Lens Wear with Eye Closure (original) (raw)
Related papers
Eye & Contact Lens: Science & Clinical Practice, 2004
To investigate thickness changes of the total cornea and epithelium across the horizontal corneal meridian after 4 weeks of overnight corneal refractive therapy (CRT) rigid contact lens (Paragon Vision Sciences, Mesa, AZ) wear. Methods. Thirty subjects were fitted with CRT contact lenses (Dk/t ϭ 67), which were worn overnight for 4 weeks. Corneal thickness was measured at nine locations along the horizontal meridian by using optical coherence tomography (OCT) before lens insertion in the evening. Corneal thickness was measured the next morning immediately after lens removal and 1, 3, 7, and 14 hours later. This was repeated on days 4, 10, and 28 of the study and then 3 days after discontinuing lens wear. Results. Twenty-three subjects completed the study. At lens removal on day 1, the central and paracentral cornea swelled by 4.9% and 6.2%, respectively (both P ϭ 0.000). The central epithelium thinned by 7.3%, and the mid peripheral epithelium thickened by 13% (both P ϭ 0.000). Corneal swelling recovered throughout the day, with most of the deswelling taking place within the first 3 hours after lens removal. Maximal central epithelial thinning reached 13.5% by day 4. Three days after the study completion, corneal and epithelial thickness had recovered to baseline values. Conclusions. This study shows that CRT lenses induce differential overnight swelling across the cornea, with rapid deswelling during the day. Central epithelial thinning and paracentral thickening occurs, with recovery 3 days after discontinuation of lens wear.
The Effects of Overnight Orthokeratology Lens Wear on Corneal Thickness
Investigative Opthalmology & Visual Science, 2003
To investigate corneal thickness changes during overnight orthokeratology with reverse-geometry rigid gas-permeable (RGP) contact lenses worn over a 3-month period. METHODS. Eighteen young adult subjects with low myopia (Յ4.00 D) were fitted with reverse-geometry lenses (BE; Ultra-Vision 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. RESULTS The orthokeratology group showed significant reductions in myopia (ϩ1.66 Ϯ 0.50 D; P Ͻ 0.001) from day 1, which stabilized by day 10. Central corneal thinning (Ϫ9.3 Ϯ 5.3 m, P Ͻ 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 (ϩ10.9 Ϯ 5.9 m, P Ͻ 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. CONCLUSIONS. 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.
Variations in Central Corneal Thickness During the First Year of Contact Lens Wear
Acta Ophthalmologica, 2009
Variations in central corneal thickness during the first year of hard, hydrophilic or silicone lens wear are reported. The mean corneal swelling after 1/2,3 and 6 months was 4.7-3.0% in the first 2 groups (P < 0.001-P = 0.005), but only 1.3-0.8% in the latter group (P = 0.01 1-0.050). These differences were statistically significant (P < 0.001-P = 0.046) and are ascribed to a higher oxygen tension under the silicone lenses. An overall reduction of corneal oedema was noted after 1/2 month (P = 0.025). One year after lens fitting a similar and not significant corneal swelling was found in the 3 lens groups. In addition to an initial 'osmotic' adaptation our results indicate that a further corneal adaptation to hard and hydrophilic lenses may take place between 6 and 12 months after lens fitting. Development of lens intolerance was not correlated to the degree of corneal oedema after 112 month of lens wear.
Purpose: To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. Methods: Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-pointtouch fitting approach. The lens' back optic zone radius (BOZR) was 0.4 mm and 0.1 mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. Results: A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p < 0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p < 0.05). Significant reduction was found over time in CCA (p = 0.001) and anterior corneal asphericity in both groups (p < 0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p < 0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p < 0.05).
Contact Lens and Anterior Eye, 2019
To evaluate the changes in corneal epithelial thickness and corneal anterior and posterior curvatures during the day, and the effect of wearing daily disposable soft contact lenses. Methods: Thirty-two healthy volunteers were enrolled in a randomized crossover study. At the baseline visit, corneal and epithelial thickness maps (OCT; Optovue, Inc., Fremont, CA, USA) and keratometric measurements (Pentacam, Oculus, GmbH, Germany) were performed in the morning and in the afternoon (8 hours after). Then, each subject was fitted with the following brands of daily disposable contact lenses in random order: Dailies Total 1 (Delefilcon A), Dailies Aqua Comfort (Nelfilcon A), TruEye (Narafilcon A) and Biotrue Oneday (Nesofilcon A) on different days. All fitted lenses had a power of −3.00 diopters (D). Measurements were repeated before putting the contact lens on and after an-eight-hour contact lens wear. Results: With no lens wear, the anterior topographic indices showed significant steepening [Kflat: p < 0.0001; Ksteep: p < 0.0001 and maximum keratometry value (Kmax): p = 0.04] and the corneal thickness significantly decreased in the central and temporal portion of the cornea in the afternoon. There were no significant changes in the posterior topographical indices and corneal epithelial thickness. With contact lens wear, no significant change occurred in the corneal and epithelial thickness, and the anterior and posterior curvatures during the day (all p values > 0.05). There was no statistically significant difference in the epithelial thickness among the groups wearing different contact lens types (p > 0.05). Conclusions: Anterior corneal topographic indices steepen depending on the natural diurnal variations. Daily wear of soft contact lenses appears to mask this steepening. The corneal epithelial thickness is not affected by daily disposable soft contact lenses.
Epithelial Thickness Changes from the Induction of Myopia with CRTH RGP Contact Lenses
Investigative Ophthalmology & Visual Science, 2008
To investigate changes in epithelial thickness after overnight wear of CRTH rigid gas-permeable (RGP) lenses (Paragon Vision Sciences, Mesa, AZ) for the correction of hyperopia. METHODS. Twenty subjects wore a ϩ3.50 D hyperopia-correcting CRTH lens on one eye for a single night in an attempt to induce myopia (first study). The untreated eye served as the control. Corneal and epithelial thickness was measured at nine points across the horizontal meridian by OCT. Measurements were obtained the night before lens wear, immediately after lens removal the next morning, and 1, 3, 6, and 12 hours after removal. Measurements were obtained 28 hours later, to observe recovery. Then, the attempted hyperopic corrections of ϩ1.50 and ϩ3.50 D were evaluated, using CRTH lenses in both eyes of 20 subjects for a single night (second study). RESULTS. All values were compared to baseline unless otherwise stated. In the first study, the treated eye's central and midperipheral epithelial thickness increased by 21.5% Ϯ 8.6% and 13.3% Ϯ 7.6%, respectively, after lens removal (P Ͻ 0.001). The control eye's central epithelial thickness (CET) increased by 7.1% Ϯ 6.0% (P Ͻ 0.05). In the second study, CET increased by 17.6% Ϯ 8.5% (P Ͻ 0.001) in the ϩ3.50 D-treated eye and by 13.3% Ϯ 4.8% (P Ͻ 0.001) in the ϩ1.50 D-treated eye. Midperipheral epithelial thickening was 5.9% Ϯ 4.7% (P Ͻ 0.05) in the ϩ3.50 D-treated eye and 6.0% Ϯ 6.3% (P Ͻ 0.05) in the ϩ1.50 D-treated eye. CONCLUSIONS. CRTH lenses, designed to correct hyperopia, when worn overnight, caused an increase in CET. The amount of epithelial change seemed to differ with modified lens design. (Invest Ophthalmol Vis Sci. 2008;49:3345-3350)
2019
Background: To investigate the changes in the corneal epithelial thickness along the steep (ETS) and flat (ETF) meridians of astigmatic corneas after six months of overnight spherical myopic orthokeratology (OK) lens wear.Methods: A prospective study. Fifty-seven subjects (age range: 9–38 years) with up to 1.50 diopters (D) of corneal toricity wore spherical OK lenses in both eyes for 6 months. Evaluations of OK lens fit, visual acuity, refractions and corneal topography were performed at baseline and after 6 months’ of overnight OK lens wear. Fourier-domain optical coherence tomography (FD-OCT) was conducted to measure the central corneal epithelial topography along varying meridians over a diameter of 6mm. The values of epithelial thickness (ET) along the steep and flat meridians were recorded at 1mm intervals from the corneal apex to the mid-periphery along chords with a diameter of 6mm（Φ6mm）and compared between pre- and post-lens wear (change of ET at the steep meridian: △ETS; c...
Apical Clearance Rigid Contact Lenses Induce Corneal Steepening
Purpose. Anecdotal reports suggest that steeply fitted rigid contact lenses can induce corneal steepening and myopic shifts in refraction. This study investigated changes in corneal topography, corneal thickness, and refraction after short-term wear of apical clearance lenses. Methods. Ten young adults participated in the study in which apical clearance lenses (Conoid, Hydron Pty. Ltd., Frenchs Forest, NSW, Australia), fitted approximately 0.3 mm steeper than the flattest keratometric reading, were worn for 4 h. A polymethyl methacrylate (PMMA) lens was worn in one eye, and a Boston XO lens (Bausch & Lomb, Rochester, NY) was worn in the other. Lenses were nonfenestrated in the first trial, and a single midperipheral fenestration was incorporated for a second trial. Corneal topography was monitored using the EyeSys topographic analysis system (EyeSys Vision, Inc., Houston, TX); central corneal thickness was quantified using ultrasonic pachometry; and refraction and anterior ocular response were also monitored. Results. Significant central corneal edema (8.2 2.2%) was demonstrated in the PMMA lens-wearing eye only. Fenestration did not reduce the edema response. We found significant corneal steepening over a 5-to 6-mm central zone, which was more pronounced in the PMMA lens-wearing eye and was modified by lens fenestration. The curvature changes altered central corneal shape from prolate (Q 0.06 0.10) to oblate (Q 0.26 0.31). A slight myopic shift in refraction (0.38 0.60 D) was found with the PMMA lenses only. Conclusions. Apical clearance lenses induce corneal steepening after short-term wear. Although corneal molding is implicated as the primary factor driving the shape change, corneal edema and postlens tear film pressures can modify this response. (Optom Vis Sci 2004;81:427-435) T here is growing interest in the use of rigid contact lenses to manipulate corneal topography for refractive purposes. Recent reports of impressive clinical results with reverse geometry rigid lens designs 1-4 have reawakened interest in the technique of orthokeratology (OK) for the reduction of myopia and astigmatism. 5 There have been no reports in the recent literature of attempts to manipulate corneal topography for hyperopic correction. In the early 1960s, Jessen 6, 7 reported successful hyperopic OK using steeply fitting polymethyl methacrylate (PMMA) lenses. In the orthofocus technique described by Jessen, lenses were fitted steeper than K (flattest keratometric reading) by the amount of desired correction in diopters; the contact lens itself was plano in power, and the tear lens created by the lens fitting supplied the desired refractive correction. Although no data were presented, Jessen 7 claimed that up to 3.50 D of hyperopia could "respond well to use of the lens" and that after at least 1 year of lens wear patients "manifested less than 1/2 of their original refractive error." 7 He also claimed that the effects were stable after lens removal, particularly in young patients. 6 Coon 8 later commented that this clinical technique was subsequently largely abandoned because of problems with corneal edema, presumably because of the use of steeply fitted lenses in oxygen-impermeable PMMA material. It is difficult to find any published studies that provide support for Jessen's claims. The early PMMA literature presented conflicting reports on corneal curvature changes even during conventional rigid contact lens wear, partly because of the difficulty in separating the effects of corneal hypoxic edema and corneal molding. It was recognized that the cornea typically demonstrated transient cor-neal steepening during the initial "adaptation" period because of central corneal edema, followed by gradual flattening presumed to be the result of corneal molding. Carney 9 was able to demonstrate that these two factors (edema and molding) provoked different and independent patterns of corneal curvature change and that steeply
Corneal response to rigid contact lens wear
British Journal of Ophthalmology, 1982
Three adult rhesus monkeys were subjected to 2 and 24 hours of polymethylmethacrylate (PMMA) contact lens wear. The induced corneal changes were examined with the electron microscope. Mild epithelial oedema as well as early degenerative cell changes was present already after 2 hours' wear. Rigid lens wear for 24 hours produced more severe oedema and cell alterations together with premature cell loss and ultimately, in areas of lens bearing, corneal denuding. Only the monkeys wearing contact lenses for 24 hours had significant stromal swelling, which was primarily evident in the posterior region, while the anterior limiting lamina remained unaffected. The stromal swelling was patchy and mainly around keratocytes and between lamellae, while fluid within the lamellae was evident only occasionally in posterior stroma. Changes among keratocytes were evident, especially posteriorly, where reaction was frequently severe. Endothelial reaction was restricted to a limited fluid uptake in the 24-hour-wear experiment. In addition there was in these monkeys an apparent loosening of the endothelial adhesion to the posterior limiting lamina. It is concluded that the oedematous epithelium undergoes cell shrinkage and flattening, which is compensated for by an uptake of fluid. The uptake of fluid maintains the overall normal thickness of the epithelium. The conclusion is supported by other studies, where the normal thickness of oedematous epithelium has been shown by pachometry. The results in the present study further suggest that stromal oedema in the contact lens wearer is a result of a relative loss of endothelial function, leading to a swelling that moves in a posterior to anterior direction.