Overnight Orthokeratology

Systematic Review of Myopia Progression after Cessation of Optical Interventions for Myopia Control

Despite high discontinuation rates for myopia optical interventions, limited attention has been given to the potential rebound effects post-discontinuation. This systematic review aims to assess the extent of the rebound effects following the cessation of common clinical optical myopia-control interventions in children. A comprehensive search of PubMed, Embase, Cochrane CENTRAL, and ClinicalTrials.gov was conducted from inception to October 2023. The rebound effects, defined as changes in the axial length or spherical equivalent during and after treatment cessation, were categorized into four levels. These studies encompassed 703 participants and spanned from 2019 to 2023, with durations of treatment and cessation ranging from 6 months to 3.5 years and from 2 weeks to 5 years, respectively. This review, encompassing 14 studies, revealed a predominant strong rebound effect in orthokeratology (8 studies), a weak rebound effect in multifocal soft contact lenses (4 studies), and a variable rebound effect in peripheral-plus spectacle lenses (2 studies). Notably, with the increasing cessation duration, the rebound effects diminished, potentially linked to the reversal of choroidal thickening and the disappearance of peripheral myopic defocus. In conclusion, a temporal trend of rebound effects exists in all three myopia optical interventions, possibly contributing to their myopia control mechanisms.

The alterations in ocular biometric parameters following short-term discontinuation of long-term orthokeratology and prior to subsequent lens fitting: a preliminary study

PURPOSE

To investigate the alterations in biometric parameters among Chinese adolescents over an extended period of wearing orthokeratology lenses, as well as the subsequent changes after a one-month cessation of lens usage prior to the secondary lens fitting.

METHODS

Twenty-four myopic patients aged 7-14 were enrolled in this 37-month prospective observational study. Ocular biometric parameters were measured in the study. Ocular biometric parameters were assessed, and the utilization of Generalized Estimating Equations (GEE) was employed in the analysis to address the correlation between the two eyes of each participant.

RESULTS

The axial length (AL) increased by 0.55 mm after 36 months of lens wearing and further increased to 0.62 mm at the 37-month follow-up compared to the initial measurement. The differences in AL elongation per month between the 37-month time point and the 12-, 24-, and 36-month marks of lens wearing were found to be statistically significant (p12-month = 0.001; p24-month = 0.003; p36-month = 0.001). Following the cessation of lens wear for 1 month, there was no significant complete recovery observed in the flat and steep keratometry values. However, the intraocular pressure and anterior chamber depth returned to their baseline levels.

CONCLUSIONS

The AL elongation undergoes alterations during temporary discontinuation of lenses, with the flat and steep keratometry measurements remaining significantly flatter compared to the baseline. However, the intraocular pressure and anterior chamber depth return to their initial levels after one month of lens cessation.

Clinical Outcomes of a Randomized Trial with Contact Lenses for Astigmatic Myopia Management

SIGNIFICANCE

There are limited treatment options for myopia management of patients with moderate to high astigmatism. This work directly compares toric orthokeratology and soft toric multifocal lenses to show differences in visual acuity and patient satisfaction that could impact clinical care. Toric orthokeratology caused reduced visual acuity but was preferred subjectively for vision and overall.

PURPOSE

This study aimed to quantify objective and subjective clinical differences between toric orthokeratology and soft toric multifocal contact lenses in the same cohort of myopic wearers with moderate to high astigmatism.

METHODS

Thirty adults with refractive myopia (plano to -5.00 D) and astigmatism (1.25 to 3.50 D) were fitted empirically with both toric orthokeratology and soft toric multifocal contact lenses. Participants wore lenses for 10 days in random order, separated by a 14-day washout period. High-contrast visual acuity, low-contrast visual acuity, and glare logMAR visual acuity were measured. Surveys ascertained subject preference for comfort, vision, handling, and cost. Friedman, Wilcoxon signed rank, and χ2 tests were performed.

RESULTS

A subset of participants (n = 17) who achieved good vision with both lens types was analyzed. High-contrast and glare acuity with toric orthokeratology were reduced by one line compared with soft toric multifocal lenses (both 0.00 vs. -0.10, P ≤ .003). Participants preferred toric orthokeratology for vision ( P ≤ .03) but soft toric multifocal lenses for handling ( P ≤ .006). When forced to choose between lens types, participants preferred toric orthokeratology for vision and overall (both P ≤ .007).

CONCLUSIONS

Participants who achieved good vision with both lens types preferred toric orthokeratology over soft toric multifocal lenses, despite reduced high-contrast and glare visual acuity. Further research is needed to understand the relationship between visual performance and patient satisfaction.

Combination of orthokeratology lens with 0.01% atropine in slowing axial elongation in children with myopia: a randomized double-blinded clinical trial

BACKGROUND

To evaluate the additive effects of orthokeratology (OK) lenses and 0.01% atropine on slowing axial elongation in myopic children.

METHODS

A prospective, randomized, double-blinded, placebo-controlled trial was conducted over a 12-month period. Sixty children aged 8 to 12 years with spherical equivalent refraction from - 1.00 to -4.00 D who had been wearing OK lenses successfully for 2 months (as baseline) were randomly assigned in a 1:1 ratio to combination group (combination of OK lens and 0.01% atropine eye drops) and control group (combination of OK lens and placebo). The primary outcome was change in axial length, along with secondary outcomes including change in pupil diameter (PD) and accommodative amplitude (AMP) at 12 months (measured at 4-month intervals).

RESULTS

After 12 months, the overall axial elongation was 0.10 ± 0.14 mm and 0.20 ± 0.15 mm (p = 0.01) in the combination and control groups, respectively. The change in axial length in the two groups showed significant differences only in the first four months (median [Q1, Q3] (95% CI), -0.01 mm [-0.07, 0.05] (-0.06, 0.04) vs. 0.04 mm [0.00, 0.10] (0.02, 0.09); p = 0.04), but no difference thereafter. Multivariate linear regression analysis showed that the axial elongation was significantly slower in the combination group than in the control group (standard β = -0.10, p = 0.02). PD significantly increased by 0.45 mm [0.20, 0.68] at the 4th month visit (p < 0.001) and then remained stable in the combination group. The PD in the control group and AMP in the two groups remained stable from baseline to 12 months (all p > 0.05).

CONCLUSION

The combination therapy was more effective than the OK lens alone in slowing axial elongation after 12 months of treatment, and mainly in the first 4 months.

TRIAL REGISTRATION

The First Affiliated Hospital of Zhengzhou University, ChiCTR2000033904. Registered 16/06/2020, http://www.chictr.org.cn/login.aspx?referurl=%2flistbycreater.aspx.

Adjunctive effects of orthokeratology and atropine 0.01% eye drops on slowing the progression of myopia

CLINICAL RELEVANCE

All eye health care practitioners should know how to control myopia.

BACKGROUND

Investigating the adjunctive effects of orthokeratology and 0.01% atropine eye drops on controlling the progression of myopia in Chinese children.

METHODS

The prospective study included Chinese children aged 8 to 13 years having a spherical equivalent refractive error ranging from -2.00 to -5.00 D. Participants were categorised into two groups: combination group (orthokeratology and 0.01% atropine) or atropine group (0.01% atropine). The axial length and spherical equivalent refraction were measured at baseline and every three months post-treatment and compared over two years.

RESULTS

The combinaion and atropine groups comprised 20 and 22 participants. Following two years of treatment, the average spherical equivalent refraction change was 0.88 ± 0.31 D and 1.14 ± 0.63 D in the combination group and atropine group, respectively (P = 0.026), with an average increment in axial length of 0.50 ± 0.17 mm and 0.61 ± 0.21 mm, respectively (P = 0.091). In the atropine group, increased axial length was positively correlated with baseline spherical equivalent refraction (P = 0.018) and negatively correlated with baseline age (P = 0.003). However, these correlations were not observed in the combination group. In the subgroup of subjects aged 8-10 years and another subgroup of subjects with shorter initial axial length (22.00 to 24.50 mm), the changes in axial length over two years were significantly smaller in the combination group than the atropine group.

CONCLUSION

Orthokeratology and 0.01% atropine eye drops combination therapy were found to be more effective in reducing progression of myopia, as measured through spherical equivalent refraction changes, than atropine monotherapy in children over two years. Combinatorial therapy was more effective in controlling the elongation of axial length in children with younger baseline age or shorter baseline axial length.

Should Overnight Orthokeratology Patients Wear Their Lenses During Their Afternoon Nap?

PURPOSE

The purpose of this study was to evaluate changes in visual acuity, corneal curvature, elevation, pachymetry, and objective quality of vision of experienced orthokeratology patients using their contact lenses during a simulated 30-min afternoon nap.

METHOD

Twelve patients aged 30.8±8.3 years were recruited for the study, with a history of overnight orthokeratology of 27.4±23.0 months. Patients were instructed to close their eyes for 30 min while wearing their contact lenses or without lenses. Anterior corneal curvature, elevation, and corneal pachymetry were assessed with the Pentacam Scheimpflug System at 17 predefined corneal locations, and the HD Analyzer (Terrassa, Spain) was used to measure objective quality of vision. Measurements were conducted before eye closure (baseline), immediately after eye opening/lens removal (M1), and 30 min later (M2).

RESULTS

No statistically significant differences were found in anterior corneal curvature and elevation between baseline values and M1 or M2, with and without contact lenses. Corneal swelling at M1 was greater without contact lenses (change in central corneal thickness of 2.3%±3.1%, P=0.001) than with contact lenses (1.7%±1.3%, P<0.001). Recovery at M2 was slower when lenses were worn. A statistically significant improvement in objective quality of vision and visual acuity was found only when patients napped with their lenses.

CONCLUSIONS

Even if no significant changes were found in corneal curvature and elevation, patients of overnight orthokeratology may benefit from using their contact lenses during their afternoon nap in terms of objective quality of vision and visual acuity.

The Impact of Overnight Orthokeratology on Accommodative Response in Myopic Subjects

This study aimed to evaluate the effects of two months of orthokeratology (OK) treatment in the accommodative response of young adult myopes. Twenty eyes (21.8 ± 1.8 years) were fitted with the Paragon CRT^® 100 LENS to treat myopia between −1.00 and −2.00 D. Low- and high-contrast visual acuity (LCDVA and HCDVA), central objective refraction, light disturbance (LD), and objective accommodative response (using the Grand Seiko WAM-5500 open-field autorefractometer coupled with a Badal system) were measured at baseline (BL) before lens wear and after 1, 15, 30, and 60 nights of OK. Refractive error correction was achieved during the first fifty days of OK lens wear, with minimal changes afterwards. LD analysis showed a transient increase followed by a reduction to baseline levels over the first 30 nights of treatment. The accommodative response was lower than expected for all target vergences in all visits (BL: 0.61 D at 1.00 D to 0.96 D at 5.00 D; 60 N: 0.36 D at 1.00 D to 0.79 D at 5.00 D). On average, the accommodative lag decreases over time with OK lens wear. However, these differences were not statistically significant (p > 0.050, repeated-measures ANOVA and Friedman test). This shows that overnight OK treatment does not affect objectively measured the accommodative response of young, low myopic eyes after two months of treatment stabilization.

Efficacy of combined orthokeratology and 0.01% atropine solution for slowing axial elongation in children with myopia: a 2-year randomised trial

Eighty Japanese children, aged 8–12 years, with a spherical equivalent refraction (SER) of − 1.00 to − 6.00 dioptres (D) were randomly allocated into two groups to receive either a combination of orthokeratology (OK) and 0.01% atropine solution (combination group) or monotherapy with OK (monotherapy group). Seventy-three subjects completed the 2-year study. Over the 2 years, axial length increased by 0.29 ± 0.20 mm (n = 38) and 0.40 ± 0.23 mm (n = 35) in the combination and monotherapy groups, respectively (P = 0.03). Interactions between combination treatment and age or SER did not reach significance level (age, P = 0.18; SER, P = 0.06). In the subgroup of subjects with an initial SER of − 1.00 to − 3.00 D, axial length increased by 0.30 ± 0.22 mm (n = 27) and 0.48 ± 0.22 mm (n = 23) in the combination and monotherapy groups, respectively (P = 0.005). In the − 3.01 to − 6.00 D subgroup, axial length increased by 0.27 ± 0.15 mm (n = 11) and 0.25 ± 0.17 mm (n = 12) in the combination and monotherapy groups, respectively (P = 0.74). The combination therapy may be effective for slowing axial elongation, especially in children with low initial myopia.

Overnight orthokeratology

Overnight orthokeratology lenses are approved in countries all over the world for the temporary reduction in myopia, and recently, one lens design has received regulatory approval for myopia control in Europe. The modern orthokeratology lens has a substantial history from its origins of attempting to flatten the corneal curvature with a spherical rigid contact lens to sophisticated gas permeable lenses, designed to reshape the cornea. These lenses are predominantly prescribed for children to slow myopia progression and limit axial elongation of the eye. This article reviews the peer-reviewed literature on the efficacy of orthokeratology for myopia control, sustainability after treatment is discontinued, and the safety concerns of overnight contact lens wear. Future avenues of research are discussed.

The Topographical Effect of Optical Zone Diameter in Orthokeratology Contact Lenses in High Myopes

Purpose

To evaluate the effect of the optical zone diameter (OZ) in orthokeratology contact lenses regarding the topographical profile in patients with high myopia (−4.00 D to −7.00 D) and to study its effect over the visual quality.

Materials and Methods

Twelve patients (18 eyes) were fitted with overnight orthokeratology (OrthoK) with a randomized 6 mm or 5 mm OZ lens worn for 2 weeks, followed by a 2-week washout period, between both designs. Keratometry (K) readings, optical zone treatment diameter (OZT), peripheral ring width (PRW), higher-order aberrations (HOA), high (HC) and low contrast (LC) visual acuity, and subjective vision and comfort were measured at baseline and after 2 weeks of OrthoK lens wear of each contact lens.

Results

No significant differences were found between any measurements for the same subject at both baselines (p value > 0.05). There was no difference between OZ lens designs found in refraction, subjective vision or comfort, and HC and LC visual acuity. Contrast sensitivity was decreased in the 5 mm OZ lens design compared with 6 mm OZ design (p-value < 0.05). 5 mm OZ design provoked a greater flattening, more powerful midperipheral ring and 4^th-order corneal and total spherical aberration than the 6 mm OZ design, being statistically significant after 7 days, for corneal aberration, and 15 days, for corneal and total, of wearing the lens (p-value < 0.05). The OZT obtained were 2.8 ± 0.2 mm and 3.1 ± 0.1 mm for 5 mm and 6 mm OZ design, respectively (p-value < 0.05). Regarding PRW, the 5 mm OZ design had a wider ring width in both the nasal and temporal zones (p-value < 0.05).

Conclusions

A smaller diameter optical zone (5 mm) in orthokeratology lenses produces a smaller treatment area and a larger and more powerful midperipheral ring, increasing the 4^th-order spherical aberration that affects only the contrast sensitivity but without differences in visual acuity and subjective vision compared with a larger OZ diameter (6 mm).

The effect of part-time wear of 2-zone concentric bifocal spectacle lenses on refractive error development & eye growth in young chicks

The purpose of this study is to characterize in young chicks the myopia control effects of part-time wear of two-zone concentric bifocal lenses. Nine-day-old chicks (n = 115) were first made myopic with monocular -10 Diopter (D) single vision (SV) lenses worn for 3 days. Over the 6 days following myopia induction, either 1) two-zone bifocal lenses (-10 D center/-5 D periphery, BFDC) were worn for 12 (full-time), 10, 8, or 6 h, with -10 D SV lenses worn for the remainder of the day, or 2) BFDC or BFNC (-5 D center/-10 D periphery) lenses were worn every other day (EOD). Control birds wore -10 D SV lenses every day. Refractive error (RE) and axial ocular dimensions were monitored every three days with retinoscopy and high frequency A-scan ultrasonography respectively. Mean interocular RE and axial length differences after 3 days of myopia induction (±SEM) were -9.6 ± 0.19 D and 0.26 ± 0.01 mm across the groups. At the end of the following 6-day treatment period, equivalent values were: -10.66 ± 0.28 D, 0.42 ± 0.02 mm (SV-control); 1) -4.61 ± 0.29 D, 0.26 ± 0.02 mm (BFDC, 12 h); -4.82 ± 0.23 D, 0.28 ± 0.02 mm (BFDC, 10 h); -5.21 ± 0.27 D, 0.24 ± 0.02 mm (BFDC, 8 h); -6.34 ± 0.34 D, 0.25 ± 0.03 mm (BFDC, 6 h); 2) -8.29 ± 0.29 D, 0.32 ± 0.03 mm (BFDC, EOD), and -8.83 ± 0.36 D, 0.33 ± 0.03 mm (BFNC, EOD). Overall, full-time BFDC and part-time BFDC and BFNC lens groups exhibited similar changes and were less myopic than the SV group. The results suggest that bifocal lenses may have myopia control effects even when worn part-time, interleaved with standard (SV) myopic corrections, especially if worn for at least 6 h per day.

Increased Corneal Toricity after Long-Term Orthokeratology Lens Wear

Purpose

To investigate the change in corneal toricity and associated refractive astigmatism after discontinuation of long-term orthokeratology (ortho-k) lens wear.

Methods

This study investigated 136 subjects aged between 6 and 14 (9.1 ± 1.5) years old at the commencement of ortho-k treatment, who had been undergoing overnight ortho-k treatment for 24 to 72 (37.4 ± 11.9) months. Corneal refractive power and manifest refraction were measured and compared before ortho-k and 1 month after discontinuation of ortho-k lens wear. Changes in corneal curvature were analyzed. Corneal curvature data from a historical longitudinal study were used as control.

Results

Compared to pre-ortho-k values, the corneal curvature became significantly flatter in the flatter meridian (-0.22 ± 0.27 D, P < 0.001) and steeper in the steeper meridian (0.06 ± 0.34 D, P=0.032) after cessation of ortho-k lens wear, resulting in a significant increase in corneal toricity (0.28 ± 0.43 D, P < 0.001), which is associated with an increase in refractive astigmatism (0.57 ± 0.57 D, r=0.465, P < 0.001). The amount of residual corneal flattening in the flatter meridian is significantly affected by the length of ortho-k treatment (t=-2.965, P=0.004) and the baseline age of subject (t=-2.841, P=0.005), but not by the baseline spherical or cylindrical refractive error (both P > 0.05). In the historical control group, there is no significant change in the corneal curvature over two years in children wearing spectacle lenses (both meridians, P > 0.05). Change of corneal toricity was more significant in the ortho-k group than in the spectacle control group (P=0.001).

Conclusions

Long-term ortho-k lens wear increases corneal toricity after discontinuation of the treatment, which is associated with an increase in refractive astigmatism. A more pronounced change in corneal toricity was found in subjects who were younger to start ortho-k and have been in a longer period of treatment. This trial is registered with http://www.chictr.org.cn (ChiCTR-TNRC-11001210).

Changes and Diurnal Variation of Visual Quality after Orthokeratology in Myopic Children

Purpose

To assess the changes and the diurnal variation of visual quality after orthokeratology in myopic children.

Methods

Forty-four eyes of 22 subjects with a mean age of 10.55 ± 1.53 years (8 to 14 years) were enrolled in this prospective study. Their spherical equivalent ranged from -1.25 to -4.25 diopters (D) and astigmatism was less than 1.00 D. Parameters including corneal curvature, ocular objective scatter index (OSI), the modulation transfer function (MTF), root mean square of ocular and corneal wavefront aberrations, and contrast sensitivity function (CSF) were measured before and at two time points during the same day after 1 month of orthokeratology.

Results

After orthokeratology, uncorrected visual acuity (UCVA) and spherical equivalent were significantly improved from baseline (P < 0.001), and their diurnal variation was not significant (P=0.083, 0.568). OSI increased from 0.29 ± 0.15 to 0.65 ± 0.31 (P < 0.001). MTF decreased significantly (P < 0.01). Corneal curvature and ocular total aberration decreased (P < 0.001), while the ocular and corneal higher-order aberration increased significantly (P < 0.01). The CSF under photopic condition decreased at 3 cpd (P=0.006) and increased at 18 cpd (P=0.012). The diurnal variation of CSF at 18 cpd under mesopic and high glare conditions and at 12 cpd under photopic condition was significant (P=0.002, 0.01, 0.017).

Conclusions

Orthokeratology can effectively improve UCVA and high spatial frequency CSF by decreasing the low-order aberrations. However, MTF and CSF at low spatial frequency decreased because of the increase of intraocular scattering and high-order aberrations. Meanwhile, CSF at high spatial frequency fluctuates significantly at two times during the same day after 1 month orthokeratology.

Corneal morphology and visual outcomes in LASIK patients after orthokeratology: A pilot study

A STATEMENT OF SIGNIFICANCE

For the first time, this study shows that corneas that previous undergone orthokeratology treatment do not respond differently to LASIK compared with previous soft contact lens wear experience.

PURPOSE

To evaluate and compare the corneal morphology and visual outcomes of long-term soft and orthokeratology (OK) contact lens fitting in wearers undergoing corneal refractive surgery (LASIK) for myopia correction.

METHODS

Sixteen (16) myopic patients wearing hydrophilic soft contact lens (SCL, n = 8 subjects, control group) and OK (n = 8 subjects, OK group) lenses who undergone LASIK were retrospectively evaluated. Preoperative fitting of contact lenses and one year postoperative were studied using Pentacam (Oculus, Inc. GmbH, Wetzlar, Germany). Corneal pachymetry and volume, corneal topography, anterior and posterior surface elevation data and the anterior surface aberrometry of the cornea were recorded and used for fitting.

RESULTS

Age, refractive error and topographic parameters before LASIK did not showed statistically significant differences between the two study groups. LASIK post-treatment results showed identical changes in both control and OK groups and did not show significant differences in all the parameters evaluated. The changes on corneal parameters and HOA due to refractive surgery intervention were not different between Control and OK group (p > 0.050).

CONCLUSIONS

Corneal changes due to OK treatment are reversible after its discontinuation. The present study gives an overview of how OK does not impair future LASIK surgery for the correction of myopia and does not influence the success/results of such intervention. These findings suggest that OK CL wear does not change corneal biomechanics and does not compromise a possible LASIK refractive surgery. Although this is a pilot study and there is a need of evaluate this results/changes in future studies.

Discontinuation of long term orthokeratology lens wear and subsequent refractive surgery outcome

PURPOSE

To report a case of lens discontinuation in a long term orthokeratology (OK) lens wearer and describe regression in refraction, corneal topography, and corneal thickness over 408days after lens discontinuation. Furthermore, the outcome of subsequent LASIK treatment is also reported.

CASE REPORT

A 41year old Caucasian female who had been previously wearing OK lenses for 13 years discontinued lens wear in the left eye to consider refractive surgery in that eye. The greatest changes in subjective and objective refractions, corneal topography and thickness occurred during the first 28days after lens discontinuation. Subjective refraction did not reach baseline values, but corneal topography parameters returned to pre-OK values after 408days of no lens wear. The patient then received successful refractive surgery treatment in that eye, achieving uncorrected visual acuity of 0.00 LogMAR units, and residual refractive error within ±0.50D of emmetropia.

CONCLUSION

The period of lens discontinuation required for long term OK lens wearers before refractive surgery is likely to vary between individuals and the patient described in this case report required a significant period of lens discontinuation of at least one year before being considered suitable for refractive surgery.

A prospective interventional study of effect of accelerated orthokeratology on the corneal curvature and refraction among young adults with myopia

BACKGROUND

Orthokeratology with reverse geometry contact lens is a non-surgical alternative to conventional contact lenses for correction of myopia. However, the strength of evidence for its efficacy and safety is limited to retrospective studies and only a few prospective studies. This prospective study, the first on Indian subjects, evaluated the outcome of orthokeratology among young myopes.

METHODS

Fifty eyes of 25 young myopes (age 19-29 years) with myopia of -1 to 5.0 diopter underwent accelerated orthokeratology using the reverse geometry ortho K - LK lenses for correction of myopia. They were followed up prospectively with weekly vision, refraction, corneal topography, and pachymetry to assess the correction of myopia.

RESULTS

The mean Log MAR vision corrected from 0.748 ± 0.225 at base line to 0.025 ± 0.0630 at 12 weeks with 86% achieving 6/6 unaided day time vision. This was associated with significant central corneal flattening and thinning. The lenses were well tolerated with no significant complications.

CONCLUSION

Overnight accelerated orthokeratology effectively corrects moderate degree of myopia and provide excellent spectacle free day time vision without any significant adverse effects in the short term.

Anterior segment changes produced in response to long-term overnight orthokeratology

PURPOSE

To evaluate the effect of overnight orthokeratology (OK) on anterior chamber depth (ACD), posterior radius of corneal curvature (PRCC) and axial length (AL) over one year.

METHODS

In this prospective longitudinal study, measurements were made in 34 right eyes of 34 subjects at baseline, 15 days, 1 and 12 months after starting OK treatment. ACD and PRCC measurements were obtained using a Pentacam system and AL was measured using an IOL-Master. ACD and PRCC were measured along the horizontal and vertical meridians at 1 mm intervals. These measurements were expressed as the distance from the center in the nasal (N), temporal (T), superior (S) and inferior (I) directions.

RESULTS

A significant reduction in ACD was observed in both meridians during treatment. PRCC flattened significantly in the (T) direction after 15 d (1 mm, p < 0.05), at the corneal center after 15 d (p < 0.01), in the (T) direction after 1 month (1 mm, p < 0.05), in the (S) direction after 12 months (1 mm p < 0.05), in the (N) direction after 12 months (1 mm p < 0.05), in the (N) and (T) directions after 12 months (3 mm, p < 0.05) and in the (T) direction after 12 months (4 mm p < 0.05), at the corneal center after 12 months (p < 0.01). AL was significantly reduced during treatment (p < 0.05).

CONCLUSIONS

A long period of OK reduces ACD and AL and changes PRCC.

Changes in refraction, ocular aberrations, and corneal structure after suspending rigid gas-permeable contact lens wear in keratoconus

PURPOSE

This study reports on changes in visual acuity, ocular higher-order aberrations, and refraction after suspending rigid gas-permeable lens wear for 1 week in 15 patients with moderate to severe keratoconus. Alterations in the anterior surface, central corneal powers and axes, and central corneal thickness were also explored.

METHODS

Scheimpflug photography and Hartmann-Shack aberrometry were performed at 2 visits, 7 days apart, after the patients had removed their habitual contact lenses. Subjective refraction and both high- and low-contrast logarithm of the minimum angle of resolution visual acuities were also recorded at both visits.

RESULTS

Reductions in both high-contrast visual acuity (P = 0.001) and low-contrast visual acuity (P = 0.002), along with an increase in third-order root mean square aberrations (P = 0.008), occurred after rigid gas-permeable lens wear was suspended in these patients with keratoconus. However, no significant changes in subjective refraction were found over the 1-week period (P ≥ 0.10). Significant correlations were observed between third-order coma root mean square aberrations and the measured high-contrast (r(p) ≥ 0.59; P ≤ 0.02) and low-contrast visual acuities (r(P) ≥ 0.61; P ≤ 0.015). In addition to increases in the anterior surface central corneal powers (P ≤ 0.02), a reduction in central corneal thickness also was found between the 2 visits (P = 0.00016).

CONCLUSIONS

Changes in the optical and structural parameters of the keratoconic cornea occur after suspending rigid gas-permeable contact lens wear. This information may be of interest to practitioners concerned with prescribing aberration-controlling soft contact lenses for such patients.

Residual corneal flattening after discontinuation of long-term orthokeratology lens wear in asian children

OBJECTIVES

Most patients treated with orthokeratology (OK) in Asia are children. The effects of long-term OK on corneal curvature among children after lens wear discontinuation have not previously been reported.

METHODS

This study investigated 28 subjects, aged 10.4 +/- 2.5 years at commencement of OK lens wear, who had been treated with OK for 50.2 +/- 27.4 months. Corneal curvature was measured with a Canon RK3 autokeratometer before commencement of OK and again approximately 2 weeks (17.3 +/- 8.6 days) after discontinuation of OK lens wear. Data were analyzed using paired Student t tests, with a critical P value of 0.05.

RESULTS

Compared with baseline, residual flattening of the cornea was found after cessation of OK lens wear, averaging 0.07 +/- 0.04 mm in the flat meridian (P<0.001) and 0.02 +/- 0.07 mm in the steep meridian (P=0.07). This was confirmed by power vector analysis of curvature data, with a significant reduction in M (-0.27 +/- 0.23 diopter (D); P<0.001), and a slight increase in J0 (0.17D +/- 0.36D; P=0.02). A trend toward greater residual corneal flattening was found among subjects with more pretreatment myopic refractive error (P=0.04).

CONCLUSIONS

Corneal curvature may not necessarily return completely to baseline after discontinuation of long-term OK lens wear in children. Intermittent temporary discontinuation of OK lens wear and close monitoring of corneal recovery are recommended during long-term OK treatment.

Reversibility of effects of orthokeratology on visual acuity, refractive error, corneal topography, and contrast sensitivity

OBJECTIVES

To investigate the changes in corneal shape and optical performance during and after discontinuation of overnight orthokeratology for correction of myopia.

METHODS

Both eyes of 15 subjects were fitted with overnight reverse-geometry orthokeratology lenses, which were then worn for >4 hr overnight for 52 weeks. Subjects were free of ocular disease and had a corrected visual acuity of > or =1.0. Refractive correction, uncorrected visual acuity, corneal topography, and contrast sensitivity (at 4 spatial frequencies) were measured under photopic conditions.

RESULTS

Refractive error (spherical equivalent) and contrast sensitivity were decreased, whereas uncorrected visual acuity, the surface asymmetry index, and the surface regularity index were increased, 1 week after the onset of overnight orthokeratology and remained so during the 52 weeks of treatment. These parameters had largely returned to baseline values by 8 weeks after treatment discontinuation.

CONCLUSIONS

Overnight orthokeratology improved uncorrected visual acuity and reduced refractive error but increased corneal irregularity and impaired contrast sensitivity. However, these changes in visual function and corneal shape were reversed after discontinuation of orthokeratology lens wear.

Recovery of corneal irregular astigmatism, ocular higher-order aberrations, and contrast sensitivity after discontinuation of overnight orthokeratology

AIMS

To examine prospectively the recovery of various parameters after discontinuation of overnight orthokeratology.

METHODS

Seventeen subjects undergoing orthokeratology for 12 months were examined. Refraction, corneal topography, wavefront aberrometry, a visual acuity test and a contrast sensitivity test were performed at baseline, 12 months after commencement of the procedure, and 1 week and 1 month after discontinuation of the treatment. Asymmetry and higher-order irregularity components were calculated using a Fourier analysis of the corneal topography data. Contrast sensitivity was assessed at four spatial frequencies, and the area under the log contrast sensitivity function (AULCSF) was calculated.

RESULTS

Orthokeratology significantly reduced manifest refraction (p<0.0001, Dunnett test) and significantly improved uncorrected visual acuity (UCVA) at 12 months after commencement of the procedure (p<0.0001). Asymmetry and higher-order irregularity components increased significantly (p<0.0001, p = 0.0032, respectively), and third- and fourth-order aberrations also increased significantly (p<0.0001). The treatment resulted in significant decreases in AULCSF (p = 0.0004). After discontinuing lens wear, all parameters, such as refraction, UCVA, asymmetry, higher-order irregularity, third-order aberration, fourth-order aberration and AULCSF, returned to the baseline level at 1 week.

CONCLUSION

This study confirmed that the effect of orthokeratology is completely reversible in light of optical quality of the eye and quality of vision as well as refraction and visual acuity.

Histomorphometric profile of the corneal response to short-term reverse-geometry orthokeratology lens wear in primate corneas: a pilot study. Cornea. 2008;27:461-470. [PMID: 18434851 DOI: 10.1097/ico.0b013e318165642c]

PURPOSE

To investigate the histological changes in primate cornea induced by short-term overnight orthokeratology (OK).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Long-term clinical outcomes for overnight corneal reshaping in children and adults. Eye Contact Lens. 2008;34:94-99. [PMID: 18327044 DOI: 10.1097/icl.0b013e31811eba10]

PURPOSE

To retrospectively evaluate outcomes of overnight corneal reshaping (OCR) in children aged 12 years or younger compared to children older than 12 years and adults at one practice to establish the efficacy and safety of OCR during a period of 51 months.

METHODS

Examination records of OCR patients were reviewed for pretreatment data, including manifest refraction, keratometric readings, topography, corneal staining, and age at beginning OCR. Posttreatment records were reviewed for manifest refraction, unaided visual acuity, keratometric readings, topography, corneal staining, adverse events, and duration of OCR lens wear.

RESULTS

Records of 296 OCR patients were evaluated. One hundred fifty-four (52.0%) patients were 12 years old or younger. Sixty-eight percent of all patients in the study were Asian, and almost 95% of the patients aged 12 years or younger were Asian. The patients aged 12 years or younger had a mean original spherical equivalent refractive error of -3.50 +/- 1.50 diopters (D). The patients older than 12 years had a mean original spherical equivalent refractive error of -3.20 +/- 1.50 D. Refractive changes were similar between the group aged 12 years or younger and the group older than 12 years (3.30 +/- 1.40 D vs. 3.10 +/- 1.40 D) (P=0.14). The mean unaided, binocular logMAR visual acuity was 0.03 +/- 0.06 (i.e., 20/20) for the group aged 12 years or younger and 0.02 +/- 0.07 (i.e., 20/20) for the group older than 12 years. There were three adverse events during the study that did not result in a loss of best-corrected visual acuity. A total of 507 patient-years of wear was represented in the study.

CONCLUSIONS

OCR resulted in comparable safety and efficacy in temporarily reducing myopia for children younger than 12 years as it is for children older than 12 years and adults.

Bubble and corneal dimple formation after the first overnight wear of an orthokeratology lens: a case series

PURPOSE

To report the first documented case series of bubbles and corneal dimples associated with corneal reshaping after the first overnight wear of an orthokeratology lens.

METHODS

Three cases of transient corneal dimples are described after the first overnight use of the Be Free orthokeratology lens (BE; Ultravision Pty. Ltd., Brisbane, Australia) related to bubble formation under the posterior lens surface.

RESULTS

The corneal dimples were located most centrally and peripherally in correspondence to the reverse curve and did not produce a significant change in best-corrected visual acuity except in one patient, who had many bubbles in the central cornea.

CONCLUSIONS

The current findings suggest that the precorneal tear film between the corneal surface and the posterior orthokeratology contact lens surface plays a role in the development of bubbles and corneal dimples.

Corneal changes and wavefront analysis after orthokeratology fitting test

PURPOSE

To evaluate corneal changes and ocular aberrations during an orthokeratology test.

DESIGN

A prospective, nonrandomized cohort study.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Orthokeratology-Related Infectious Keratitis: A Case Series

PURPOSE

To describe five patients who developed infectious keratitis after the use of overnight orthokeratology contact lenses.

METHODS

Retrospective case report of five patients with infectious keratitis seen in Singapore National Eye Centre between 2001 and 2006.

RESULTS

Five children between the ages of 9 and 14 years, who wore their lenses for an average of 1.5 months before developing orthokeratology-related infectious keratitis, were seen and treated at the Singapore National Eye Centre. All five patients had cultures that were positive for Pseudomonas aeruginosa. They were treated with fortified cefazolin (50 mg/mL) and gentamicin (14 mg/mL) and responded well, with resolution of the infectious keratitis. Although most patients had a best-corrected visual acuity of 20/40 or better after the resolution of the acute infection, they all showed a central or paracentral residual scar.

CONCLUSIONS

Because of the safety issues involved, orthokeratology should be used with caution in children.

Corneal reshaping: is it a good alternative to refractive surgery?

PURPOSE OF REVIEW

To review current literature on overnight corneal reshaping and present this mode of vision correction in its current state.

RECENT FINDINGS

Overnight corneal reshaping uses specially designed rigid gas-permeable contact lenses. It is effective in temporarily reducing or eliminating low to moderate myopia. This nonsurgical mode of vision correction allows for good unaided vision during waking hours. There are reports of young patients experiencing serious adverse events, particularly bacterial and Acanthamoeba keratitis while using these lenses, although incidence rates are unknown.

SUMMARY

Overnight corneal reshaping is an alternative to refractive surgery and must continue to be studied and monitored to establish its safety.

Orthokeratology review and update

Orthokeratology (OK) is a clinical technique that uses specially designed rigid contact lenses to reshape the cornea to temporarily reduce or eliminate refractive error. This article reviews the history of traditional daily-wear OK (1960s to 1980s) and discusses the reasons for the recent resurgence in interest in the new modality of overnight OK, using reverse-geometry lens designs (1990s to the present). The clinical efficacy of the current procedure is examined and outcomes from clinical studies in terms of refractive error change and unaided visual acuity are summarised. Onset of the effects of overnight OK lens wear is rapid, with most change after the first night of lens wear and stability of refractive change after seven to 10 days. Mean reductions in myopic refractive error of between 1.75 and 3.33 D and individual reductions of up to 5.00 D have been reported. There appear to be slight reductions or minimal changes in astigmatism with the use of reverse-geometry lenses and most patients are reported to achieve 6/6 unaided vision or better. The induction of higher order aberrations, in particular, spherical aberration, has been reported and this may affect subjective vision under conditions of low contrast and pupil dilation. Patient satisfaction with overnight OK has been reported as similar to or better than with other popular modalities of contact lens wear. Available evidence suggests that the corneal changes induced by overnight OK are fully reversible. The refractive effect in OK is achieved by central epithelial thinning and this has raised concerns about compromise of the epithelial barrier to microbial infection. Recent reports of microbial keratitis in the modality are reviewed and the overall safety of the procedure is examined critically. Recent research on stromal contributions to the OK effect, particularly relating to overnight oedema, is summarised. Emerging issues in OK, including myopic control, correction of other refractive errors and permanency of the OK effect, are discussed.

Overnight Orthokeratology Experience With XO Material

PURPOSE

To evaluate long-term safety and effectiveness of overnight orthokeratology in a large sample of myopes by using three different lens designs and the highly gas-permeable Boston XO material (Bausch & Lomb, Rochester, NY).

METHODS

A total of three hundred forty-two subjects, 99 of whom were juveniles, were enrolled in the investigation at 26 clinical centers in the United States and Canada. Three different lens designs in Boston XO material were used. Subjects were limited to a measured visual need for correction of myopia less than or equal to 4.00 diopters and astigmatism less than or equal to 1.50 diopters with best-corrected Snellen visual acuity of 20/40 or better. Refractive error and unaided visual acuity were used to determine the effectiveness of the procedure at short-term (1 month) and long-term (12 months). The safety of the procedure was determined by the symptoms reported, and slitlamp findings suggested physiologic rejection of the procedure.

RESULTS

One hundred thirty-three adults and 68 juveniles completed the 12-month study. More than 60% of the subjects reached 20/20 vision or better at the end of 1 month of overnight lens wear, and this number remained stable during the next 11 months. A reduction in myopia of 70% and of more than 90% was measured at the 1- and 12-month visits, respectively. Safety data indicate a decrease in symptoms and in general a decrease in positive slitlamp findings with time.

CONCLUSIONS

The procedure with all three lenses in Boston XO material is effective. However, the safe use of orthokeratology lenses is predicated on the emphasis of clear patient direction on how to wear and take care of the lenses followed by regular examinations by an eye care practitioner.

The Current State of Corneal Reshaping

PURPOSE

The application of contact lenses to alter the shape of the cornea and temporarily reduce or eliminate myopia is known as orthokeratology, corneal refractive therapy, or corneal reshaping. It was first introduced in the 1960s, but high oxygen permeable materials and more sophisticated designs allow patients to wear contact lenses only during sleep, while dramatically improving the predictability and rate of myopia reduction. Many studies have shown that most corneal reshaping patients achieve uncorrected visual acuity of 20/25 or better that lasts all day long in one to two weeks of nighttime wear. Treatment is primarily effective through central epithelial thinning and midperipheral epithelial and stromal thickening. Much remains to be learned about corneal reshaping contact lenses and their effects on the cornea.

METHODS

The authors reviewed existing knowledge and determined what needs to be learned in order to provide patients with appropriate informed consent prior to corneal reshaping contact lens wear.

RESULTS

While corneal reshaping contact lenses are effective at temporarily reducing or eliminating myopia, claims about the progress of myopia being controlled with corneal reshaping contact lenses should not be made until further studies are published in peer-reviewed literature. The incidence and prevalence of microbial keratitis related to corneal reshaping contact lens wear is not known. Any overnight wear of contact lenses increases the risk of infection, but it is not known whether the risks of microbial keratitis are greater for corneal reshaping overnight contact lens wearers than other form of overnight contact lens wear. It is also not known whether the risk of microbial keratitis is greater for children than adults, but we must determine if children are at greater risk than adults because many children are wearing corneal reshaping contact lenses.

CONCLUSIONS

Finally, it is recommended that ongoing education be provided to practitioners and staff regarding safety, informed consent, and prevention of potential problems, with special emphasis on the critical need to properly and thoroughly disinfect lenses that will be worn overnight.

Refractive and Biometric Changes With Silicone Hydrogel Contact Lenses

PURPOSE

This study reports data from an 18-month longitudinal study of neophyte contact lens wearers and compares changes in ocular refraction and biometry induced by daily wear and continuous wear of two different silicone hydrogel (SiH) materials.

METHODS

Forty-five subjects were enrolled in the study and randomly assigned to wear one of the two silicone hydrogel materials: Lotrafilcon A or Balafilcon A lenses on either a daily or continuous wear basis. Measurements of objective refraction, axial length, anterior chamber depth, corneal curvature, and the rate of peripheral corneal flattening were performed before and 1, 3, 6, 12, and 18 months after initial fitting.

RESULTS

Mean spherical equivalent refractive error increased in the myopic direction in all contact lens groups across time (p < 0.001). Axial length was the main biometric contributor to the development of myopia. After 18 months of lens wear, subjects in the Lotrafilcon A group showed the greater mean increase in myopia (i.e., -0.50 D).

CONCLUSIONS

The results of this study show that increases in myopia, similar if not higher than those found to occur normally in young adult noncontact lens wearers, still occur with silicone hydrogel contact lens wear. The main biometric contributor to the progression of myopia was an increase in axial length. Differences between our results and those of previous studies with silicone hydrogel contact lenses could be attributed to the differing populations used in which both age and occupation may have played a role.