International multi-centre study of potential benefits of ultraviolet radiation protection using contact lenses.

PURPOSE: To examine the effects of long-term ultraviolet radiation (UVR) blocking wearing contact lenses on ocular surface health, eye focus and macular pigment. METHOD: 210 pre-presbyopic patients were recruited from Birmingham UK, Brisbane Australia, Hong Kong China, Houston USA and Waterloo Canada (n = 42 at each site). All patients had worn contact lenses for ≥ 5 years, half (test group) of a material incorporating a UVR-blocking filter. Ocular health was assessed using slit-lamp biomicroscopy and UV autofluorescence. Accommodation was measured subjectively with a push-up test and overcoming lens-induced defocus. Objective stimulus response and dynamic measures of the accommodative response were quantified with an open-field aberrometer. Macular pigment optical density (MPOD) was assessed using heterochromatic flicker photometry (MPS II). RESULTS: The two groups of participants were matched for age, sex, race, body-mass-index, diet, lifestyle, UVR exposure, refractive error and visual acuity. Limbal (p = 0.035), but not bulbar conjunctival redness (p = 0.903) was lower in eyes that had worn UVR-blocking contact lenses compared to controls. The subjective (8.0 ± 3.7D vs 7.3 ± 3.3D; p = 0.125) and objective (F = 1.255, p = 0.285) accommodative response was higher in the test group, but the differences did not reach significance. However, the accommodative latency was shorter in eyes that had worn UVR-blocking contact lenses (p = 0.003). There was no significant different in MPOD with UVR filtration (p = 0.869). CONCLUSIONS: Blocking the transmission of UVR is beneficial in maintaining the eye's ability to focus, suggesting that presbyopia maybe delayed in long-term UVR-blocking contact lenses wearers. These lenses also provide protection to the critical limbal region.

Predicting corneal refractive power changes after orthokeratology.

This study aimed to characterise corneal refractive power (CRP) changes along the principal corneal meridians during orthokeratology (OK). Nineteen myopes (mean age 28 ± 7 years) were fitted with OK lenses in both eyes. Corneal topography was captured before and after 14 nights of OK lens wear. CRP was calculated for the central 8 mm cornea along the horizontal and vertical meridians. The central-paracentral (CPC) power ratio was calculated as the ratio between maximum central and paracentral CRP change from individual data. There was a significant reduction in CRP at all locations in the central 4 mm of the cornea (all p < 0.001) except at 2 mm on the superior cornea (p = 0.071). A significant increase in CRP was evident in the paracentral zone at 2.5, 3 and 3.5 mm on the nasal and superior cornea and at 3.5 and 4 mm on the temporal cornea (all p < 0.05). No significant change in CRP was measured in the inferior cornea except decreased CRP at 2.5 mm (p < 0.001). CPC power ratio in the nasal and temporal paracentral regions was 2.49 and 2.23, respectively, and 2.09 for both the inferior and superior paracentral corneal regions. Our results demonstrates that OK induced significant changes in CRP along the horizontal and vertical corneal meridians. If peripheral defocus changes are inferred from corneal topography, this study suggests that the amount of myopia experienced on the peripheral retina was greater than twice the amount of central corneal power reduction achieved after OK. However, this relationship may be dependent on lens design and vary with pupil size. CPC power ratios may provide an alternative method to estimate peripheral defocus experienced after OK.

CLEAR - Contact lens optics.

The most fundamental aspect of a contact lens is its optics; the manner in which the refraction of light is managed to optimise vision to the clinical benefit of the lens wearer. This report presents contemporary information on the optical structure of the eye and the optical models employed to understand the correction of refractive error. The design, measurement and clinical assessment of spherical, aspheric, toric, multifocal and myopia control contact lenses are described. The complexity and variety of multifocal lenses is recognised and detailed information is provided for alternating, simultaneous, diffractive, annular, aspheric and extended depth of field lens designs. In terms of clinical assessment, a contemporary review is provided for the measurement of: visual acuity, contrast sensitivity, through focus curves, reading performance, peripheral refraction, toric displacement realignment and patient reported outcomes. Overall, the paper aims to serve as a resource for the prescribing clinician, who can optimise contact lens corrections for patients by building on the optical rationale of these devices; and also highlights future opportunities for research innovation.

CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye.

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia). However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation. In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.

Nasal-temporal asymmetry in peripheral refraction with an aspheric myopia control contact lens.

A combination of human subject data and optical modelling was used to investigate unexpected nasal-temporal asymmetry in peripheral refraction with an aspheric myopia control lens. Peripheral refraction was measured with an auto-refractor and an aberrometer. Peripheral refraction with the lens was highly dependent upon instrument and method (e.g. pupil size and the number of aberration orders). A model that did not account for on-eye conformation did not mirror the clinical results, but a model assuming complete lens conformation to the anterior corneal topography accounted for the positive shift in clinically measured refraction at larger nasal field angles. The findings indicate that peripheral refraction of highly aspheric contact lenses is dependent on lens conformation and the method of measurement. These measurement methods must be reported, and care must be used in interpreting results.

Zone of Clear Single Binocular Vision in Myopic Orthokeratology.

PURPOSE: To examine the zone of clear single binocular vision (ZCSBV) in myopic children and young adults after 12 months of orthokeratology (OK) wear, in comparison with single-vision soft contact lens (SCL) wear. METHODS: Twelve children (8-16 years) and 8 adults (18-29 years) were assessed with a series of near-point binocular vision tests when myopia was corrected using single-vision SCLs and again after 1 and 12 months of OK wear, and axial length was measured. The ZCSBV was constructed for baseline SCL wear and after 12 months of OK wear. RESULTS: After 1 month of OK wear, increased accommodative responses were noted in children (C) and adults (A) as increased binocular amplitude (C:P=0.03, A:P=0.04) and reduced accommodative lag (C:P=0.01, A:P=0.01). Divergence reserves improved after 1 month in both groups (P<0.04), and a near exophoric shift was evident at 12 months (C:P=0.01, A:P=0.04). All changes at 1 month maintained stability at 12 months. An increase in accommodation and vergence responses without reduction in range resulted in an expansion of the ZCSBV in both age groups. Axial length did not significantly change in either children (P=0.25) or adults (P=0.72). CONCLUSION: In both pediatric and young adult myopes, the ZCSBV expands toward a more divergent, increased accommodation response in OK compared with SCL wear. This occurs without a corresponding loss of convergence or accommodation deactivation, indicating improved depth of focus. These findings are relevant to visual acceptance and possible mechanisms of OK's efficacy for myopia control.

Reducing treatment zone diameter in orthokeratology and its effect on peripheral ocular refraction.

PURPOSE: To determine whether orthokeratology (OK) induced treatment zone (TZ) diameter can be reduced by altering OK lens design, and if so the impact of modifying TZ diameter on relative peripheral refraction (RPR). METHODS: 16 subjects (mean age 23.4 ±â€¯1.5 years; 8 female) completed the study. Standard (Control) OK lens design (PJ, Capricornia, Australia) or a modified version (Test) where the back optic zone diameter was reduced, and back optic zone asphericity and intermediate lens curves were altered, were worn overnight only for 7-nights in a randomised double masked order, with a minimum 1-week wash out (no lens wear) between lens designs. Full correction of refractive error was targeted. Refraction; best corrected visual acuity (BCVA); RPR (Shin-Nippon NVision-k 5001) along the horizontal and vertical meridians; and corneal topography (Medmont E300) were measured before starting lens wear and in the morning after lens removal after the seventh night of lens wear for both lens designs. TZ diameter and decentration was calculated from corneal topography. RESULTS: After 7-nights of wear both lens designs created -2.00D refraction effect with no significant difference in refractive effect or change to BCVA between the designs. The Test design created a significantly smaller horizontal (4.78 ±â€¯0.37 vs 5.70 ±â€¯0.37 mm, p < 0.001) and vertical (5.09 ±â€¯0.51 vs 5.92 ±â€¯0.51 mm p < 0.001) TZ diameter. The TZ was decentered inferior temporal with no significant difference between designs. There was no significant difference between the lens designs in RPR along the horizontal and vertical meridians at any measurement period. CONCLUSIONS: OK induced TZ diameter can be reliably reduced by altering OK lens design without detrimentally effecting lens centration or refractive effect. Reducing TZ diameter did not alter RPR, though measurement artifacts could be responsible for masking an effect. Longitudinal studies are needed to assess whether smaller TZ OK lens designs increase efficacy for slowing progression of myopia.

Stability of peripheral refraction changes in orthokeratology for myopia.

PURPOSE: Orthokeratology (OK) is known to alter relative peripheral refraction (RPR) with this presumed to be its key myopia control mechanism. A prospective, longitudinal study was performed to examine stability of OK-induced RPR changes in myopic children and young adults. METHODS: RPR of twelve children (C)(8-16 years) and eight adults (A)(18-29 years) with spherical equivalent refraction of -0.75 to -5.00D were measured unaided and while wearing single vision soft contact lenses (SCL). Measurements were repeated after 1, 6 and 12 months of OK wear. RPR was measured using an open-field Shin Nippon SRW-5000 autorefractor at 10, 20 and 30 degrees nasally (N) and temporally (T), converted into power vectors M, J0 and J45. On-axis refractions and axial lengths (IOL Master) were also measured. RESULTS: Compared to the unaided state, 1-month of OK wear shifted the RPR in the myopic direction at 30 T (C: p = 0.023; A:, p = 0.002) and 30 N (C&A, p = 0.003) and was stable thereafter, with similar changes compared to SCL wear. J0 showed a myopic shift in comparison to both unaided and SCL correction in children but not adults, and J45 did not change in either group. The on-axis OK correction was predictive of the RPR shift in both children and adults at 30 T (C: r=-0.58, p = 0.029; A: r=-0.92, p < 0.001) and 30 N (C: r=-0.60, p = 0.024; A: r=-0.74, p = 0.013) with symmetry of RPR shifts (C: r = 0.67, p = 0.008; A: r = 0.85, p = 0.004). No relationships between changes in RPR and axial length were found after twelve months of OK wear; level of myopia was stable in both groups. CONCLUSION: Relative to both unaided and single vision SCL correction, OK shifted the RPR in the myopic direction; the RPR was stable from 1 to 12 months. The RPR shift in OK wear varied with the degree of myopia but was not correlated with myopia progression.

Near binocular visual function in young adult orthokeratology versus soft contact lens wearers.

PURPOSE: To compare near point binocular vision function of young adult myopes wearing orthokeratology (OK) lenses to matched single vision soft disposable contact lens (SCL) wearers. METHODS: A retrospective clinical record analysis of all OK wearers (18-30 years) presenting over an 18 month period was undertaken. Data was extracted for 17 OK wearers, with 17 SCL wearers matched for age, refractive error and duration of contact lens wear. Binocular vision data included horizontal phoria (phoria), horizontal base-in (BIFR) and base-out fusional reserves (BOFR) and accommodation accuracy (AA). RESULTS: The OK group was 25.8±3.2years, with a duration of wear of 45.7±25months and refractive error of R -2.09±1.23D, L -2.00±1.35D. Compared to matched SCL wearers the OK group were significantly more exophoric (OK -2.05±2.38Δ; SCL 0.00±1.46Δ, p=0.005) and had better accommodation accuracy (OK 0.97±0.33D; SCL 1.28±0.32D, p=0.009). BIFR and BOFR were not different in the two groups. Frequency histograms showed that more SCL wearers had high lags of accommodation (AA≥1.50D: 8 SCL,2 OK) and esophoria (≥1Δ: 5 SCL,1 OK) than OK wearers. A positive correlation was found between refraction and phoria in the SCL group (r=0.521, p=0.032). CONCLUSION: Young adult myopes wearing OK lenses display more exophoria and lower accommodative lags at near compared to matched single vision SCL wearers. Young adult myopes with specific binocular vision disorders may benefit from OK wear in comparison to single vision SCL wear. This has relevance to both the visual acceptance of OK lenses and in managing risk factors for myopia progression.

Treatment Zone Decentration During Orthokeratology on Eyes with Corneal Toricity.

PURPOSE: To compare the magnitude of treatment zone decentration between eyes with minimally toric corneas (≤1.50 DC, LoTor group) and eyes with moderately toric corneas (1.50 to 3.50 DC, HiTor group) after a single overnight wear of spherical orthokeratology lenses. METHODS: In the LoTor group, 21 participants (9 M, 12 F, 20-40 years) were fitted using a conventional fitting approach based on the flat corneal meridian. In the HiTor group, 12 participants (5 M, 7 F, 19-45 years) were fitted using the conventional fitting method in one eye (HiTor group I) and the other eye was fitted with a lens with slightly deeper sagittal height (HiTor group II). In all groups, BE spherical orthokeratology trial contact lenses (Boston XO) were used and corneal topography data (Medmont E300) were obtained at baseline and after a single overnight wear. The magnitude of treatment zone decentration relative to vertex normal was determined from corneal topography refractive power difference maps. Treatment zone parameters including magnitude and direction of decentration were analyzed and related to baseline corneal parameters. RESULTS: After a single overnight wear, the mean magnitude of treatment zone decentration was 0.48 ± 0.20 mm in the LoTor group, 1.06 ± 0.57 mm in HiTor group I, and 0.95 ± 0.44 mm in HiTor group II. Treatment zone decentration in the LoTor group was significantly different from HiTor group I (p < 0.001), both fitted using a conventional fitting method. Treatment zone decentration was not significantly different between HiTor group I and II (p = 0.606). The magnitude of treatment zone decentration was positively correlated with the amount of baseline corneal toricity (LoTor and HiTor group I combined, p = 0.048). CONCLUSIONS: Eyes with higher amounts of corneal toricity give rise to increased amounts of treatment zone decentration in overnight orthokeratology.

The Future of Myopia Control Contact Lenses.

The growing incidence of pediatric myopia worldwide has generated strong scientific interest in understanding factors leading to myopia development and progression. Although contact lenses (CLs) are prescribed primarily for refractive correction, there is burgeoning use of particular modalities for slowing progression of myopia following reported success in the literature. Standard soft and rigid CLs have been shown to have minimal or no effect for myopia control. Overall, orthokeratology and soft multifocal CLs have shown the most consistent performance for myopia control with the least side effects. However, their acceptance in both clinical and academic spheres is influenced by data limitations, required off-label usage, and a lack of clear understanding of their mechanisms for myopia control. Myopia development and progression seem to be multifactorial, with a complex interaction between genetics and environment influencing myopigenesis. The optical characteristics of the individual also play a role through variations in relative peripheral refraction, binocular vision function, and inherent higher-order aberrations that have been linked to different refractive states. Contact lenses provide the most viable opportunity to beneficially modify these factors through their close alignment with the eye and consistent wearing time. Contact lenses also have potential to provide a pharmacological delivery device and a possible feedback mechanism for modification of a visual environmental risk. An examination of current patents on myopia control provides a window to the future development of an ideal myopia-controlling CL, which would incorporate the broadest treatment of all currently understood myopigenic factors. This ideal lens must also satisfy safety and comfort aspects, along with overcoming practical issues around U.S. Food and Drug Administration approval, product supply, and availability to target populations. Translating the broad field of myopia research into clinical practice is a multidisciplinary challenge, but an analysis of the current literature provides a framework on how a future solution may take shape.

Variation in normal corneal shape and the influence of eyelid morphometry.

PURPOSE: To investigate variation in normal corneal shape and the influence of eyelid morphometry on corneal shape in primary gaze. METHODS: Corneal topography (Medmont E300) and external eye photographs (Nikon D5000 SLR camera) were captured in primary gaze from 32 East Asians (13 male and 19 female subjects, 18 to 37 years) and 32 non-East Asians (10 male and 22 female subjects, 18 to 30 years). Participants with refractive error within ±6.00 DS and up to 1.50 DC corneal toricity were enrolled. A custom MATLAB program was used to determine hemi-meridional and sectorial corneal asphericity. A separate MATLAB program (i-Metrics) was used to determine the dimensions of anterior eyelid parameters. Sectorial corneal asphericity and eyelid morphometry dimensions were compared between ethnic groups. The interactions between sectorial asphericity and eyelid morphometry were also investigated. RESULTS: There was no significant difference in the sectorial corneal asphericity variation between ethnicities (p = 0.231). Eyelid features including horizontal palpebral fissure width; vertical palpebral fissure height; palpebral fissure slant; upper eyelid position, slope, and curvature; and lower eyelid slope and tilt were significantly different (all p < 0.05) between ethnicities. Analysis from the combined data revealed that horizontal palpebral fissure width correlated negatively with corneal spherical equivalent M (r = -0.369, p = 0.003). Upper eyelid curvature correlated negatively with corneal M (r = -0.377, p < 0.001), with differences between ethnicities. Lower eyelid slope was significantly associated with corneal power vector J45 (r = 0.262, p = 0.037). Only lower eyelid curvature showed interaction with inferotemporal (r = -0.351, p = 0.004) and inferonasal (r = -0.250, p = 0.047) mean corneal asphericity. CONCLUSIONS: Sectorial variation is present in normal corneal shape and this variation is not significantly different between East and non-East Asian eyes. Several eyelid features appear to influence corneal shape in primary gaze.

Changes to corneal aberrations and vision after Presbylasik refractive surgery using the MEL 80 platform.

PURPOSE: To investigate changes to corneal surface aberrations and vision between PresbyLASIK and LASIK for correction of presbyopia using the MEL 80 platform (Carl Zeiss Meditec, Jena, Germany). METHODS: The retrospective data of 31 patients who underwent PresbyLASIK (the PresbyLASIK group) between January 2009 and November 2011 and 20 matched patients who underwent LASIK (the LASIK group) were analyzed for changes to refraction, corrected distance visual acuity, and corneal surface wavefront aberrations calculated over 4- and 6-mm pupils. Outcomes at the 3-month follow-up visit were compared to data collected immediately prior to surgery and between PresbyLASIK and LASIK correction. Associations between induced corneal aberrations and best spherical equivalent refraction were explored. RESULTS: PresbyLASIK and LASIK significantly reduced refractive error in both myopes and hyperopes. Residual refractive error was not significantly different between treatment groups, except for spherical equivalent refraction, which was significantly more myopic following LASIK treatment compared to PresbyLASIK in myopes. There was no significant difference in postoperative corrected distance visual acuity between groups. LASIK and PresbyLASIK induced positive spherical aberration in myopes and negative spherical aberration in hyperopes, with significant differences between treatments only apparent in myopes when analyzed over a 4-mm pupil (PresbyLASIK group: 0.07 ± 0.06 µm; LASIK group: 0.03 ± 0.04 µm, P < .05). In hyperopes, induced spherical aberration was more highly associated with refractive change after LASIK (r = 0.82, P < .05) than PresbyLASIK (r = 0.64, P < .001); instead PresbyLASIK led to a more consistent shift of approximately 0.3 µm independent of induced change to refraction. CONCLUSIONS: PresbyLASIK using the MEL 80 platform induced significant changes in spherical aberration in myopes and hyperopes. PresbyLASIK appears to offer an improved response over LASIK when correcting myopes due to an apparent increase in depth of focus resulting from changes in spherical aberration. For hyperopes, PresbyLASIK provides a more consistent spherical aberration effect independent of refractive change.

Can manipulation of orthokeratology lens parameters modify peripheral refraction?

PURPOSE: To investigate changes in peripheral refraction, corneal topography, and aberrations induced by changes in orthokeratology (OK) lens parameters in myopes. METHODS: Subjects were fitted with standard OK lenses that were worn overnight for 2 weeks. Peripheral refraction, corneal topography, and corneal surface aberrations were measured at baseline and after 14 nights of OK lens wear. Subsequent to a 2-week washout period, subjects were refitted with another set of lenses where one eye was randomly assigned to wear an OK lens with a smaller optic zone diameter (OZD) and the other eye with a steeper peripheral tangent. Measurements were taken again at a second baseline and after 14 days of overnight wear of the second OK lens set. RESULTS: Standard OK lenses with a 6-mm OZD and 1/4 peripheral tangent caused significant changes in both peripheral refraction and corneal topography. Significant hyperopic shift occurred in the central visual field (VF) while a myopic shift was found at 35 degrees in the nasal VF. OK induced significant reductions in corneal power at all positions along the horizontal corneal chord except at 2.4 mm nasal where there was no significant change and at 2.8 mm nasal where there was an increase in corneal refractive power. A positive shift in spherical aberration was induced for all investigated lens designs except for the 1/2 tangent design when calculated over a 4-mm pupil. Reducing OZD and steepening the peripheral tangent did not cause significant changes in peripheral refraction or corneal topography profiles across the horizontal meridian. CONCLUSIONS: OK lenses caused significant changes in peripheral refraction, corneal topography, and corneal surface aberrations. Modifying OZD and peripheral tangent made no significant difference to the peripheral refraction or corneal topography profile. Attempting to customize refraction and topography changes through manipulation of OK lens parameters appears to be a difficult task.

Central and paracentral corneal curvature changes during orthokeratology.

PURPOSE: To investigate regional changes in corneal curvature and power induced by overnight orthokeratology (OK) contact lens wear over a period of 2 weeks. METHODS: Corneal topography data (Medmont E300) from 21 myopes (12 M, 9F, 20 to 40 years), who had worn BE OK lenses manufactured in Boston XO material for 14 nights, were analyzed retrospectively. Enrollment criteria were myopia up to 4.50 D and corneal toricity up to 1.50 D. Custom MATLAB programs were used to determine sectorial tangential curvature and refractive power, and to investigate changes from baseline after 1 and 14 nights, and between 1 and 14 nights of lens wear in the central circular zone (CCZ) and surrounding paracentral annular zone (PCZ), with each zone subdivided into nasal, superior, temporal, and inferior sectors. RESULTS: After OK, significant asymmetry was found in tangential curvature across sectors. In the CCZ, by day 14 there was greater flattening in the temporal (-1.27 ± 0.62 D, p < 0.001) than nasal sector (0.05 ± 0.62 D, p = 0.893). In the PCZ, by day 14 there was greater steepening in the temporal (2.37 ± 1.09 D, p < 0.001) than nasal sector (0.30 ± 1.36 D, p = 0.326). In both zones, vertical sectors did not show any asymmetry. The variation in corneal curvature across sectors and the mirror asymmetry was also reflected in variations in the corneal refractive power. CONCLUSIONS: OK induces non-uniform corneal changes to the central and paracentral regions. This non-uniformity may influence peripheral refraction profiles reported with OK that have been suggested to be influential in myopia control.

Corneal versus ocular aberrations after overnight orthokeratology.

PURPOSE: To investigate relationships between changes to corneal and ocular aberrations induced by orthokeratology (OK) and their influence on visual function. METHODS: Eighteen subjects (aged 20 to 23 years) were fitted with OK lenses (BE Enterprises Pty Ltd, Australia), manufactured in Boston XO material (Bausch & Lomb Boston, Wilmington, MA), and worn overnight for seven nights. Corneal and ocular aberrations were simultaneously captured (Discovery, Innovative Visual Systems, Elmhurst, IL), and contrast sensitivity function was measured on days 1 and 7, within 2 and 8 hours after lens removal on waking. Data from the eye achieving the higher myopic correction were analyzed for changes over time. RESULTS: There was a significant refractive effect at all visits. Orthokeratology induced an increase in corneal and ocular root mean square higher order aberrations (HOAs) and a positive shift in spherical aberration (SA) on day 1, with further increases by day 7. Increases in root mean square coma became significant by day 7. Changes to corneal and ocular SA were similar on day 1; however, by day 7, there was a greater increase in corneal than ocular SA, indicating a change in internal SA. Orthokeratology led to an overall decrease in contrast sensitivity function, which was isolated to spatial frequency changes on day 1 at 1 cycle per degree and on day 7 at 1 and 8 cycles per degree. CONCLUSIONS: A greater positive shift in corneal compared with ocular SA on day 7 suggests a negative shift in internal SA, which would be consistent with an increased accommodative response. Lack of any difference on day 1 indicates that this may be an ocular adaptation response toward neutralizing induced positive SA, rather than a direct effect of SA changes on the accommodation mechanism.

Refractive changes from hyperopic orthokeratology monovision in presbyopes.

PURPOSE: To investigate the time course of refractive and corneal topographic changes in overnight hyperopic orthokeratology (OK) for emmetropic presbyopes. METHODS: Sixteen adult emmetropic presbyopic subjects were fitted with rigid hyperopic OK lenses (BE Enterprises, Brisbane, Australia/Capricornia, Slacks Creek, Australia) targeted to correct +2.00 D, in one eye only. The fellow eye acted as a non-lens-wearing control. Thirteen subjects completed the study. Lenses were worn overnight for a 7-day period, and changes in subjective refraction and corneal topography were measured in the morning on lens removal (A.M.) and 8 hr after lens removal (P.M.). RESULTS: There were statistically significant changes from baseline in all variables at all visits in lens-wearing eyes. Hyperopic OK caused a -1.00 (0.33) D shift in best vision sphere refraction at Day1 A.M., and -1.11 (0.61) D, at Day7 A.M., with -0.91 D of best vision sphere change from baseline still apparent by Day7 P.M. (mean [SD]). This led to an improvement in monocular near visual acuity (VA) from Jaeger 10.8 (2.4) at baseline to Jaeger 4.6 (2.5) at Day1 A.M., Jaeger 3.2 (2.3) at Day7 A.M., and Jaeger 3.9 (3.0) at Day7 P.M. Binocular distance VA did not change from baseline. The central cornea steepened, and the mid-peripheral nasal cornea flattened at lens removal after one night of wear. There was no significant difference in central corneal steepening between A.M. visits, but there was longer retention of effect by Day7 P.M. Nasal paracentral corneal flattening also showed a greater effect and longer retention of effect by Day7. CONCLUSIONS: Hyperopic OK induced central corneal steepening and paracentral corneal flattening, which led to a monovision myopic shift in refraction that was sufficient to provide functional correction of near vision. Lack of change in binocular distance VA indicates that hyperopic OK offers a viable option for providing monovision correction in emmetropic presbyopia.

Ocular aberrations and visual function with multifocal versus single vision soft contact lenses.

PURPOSE: To investigate differences in ocular aberrations induced by centre-near multifocal soft contact lenses (SCL) relative to single vision SCLs and their effect on contrast sensitivity function (CSF). METHODS: Ocular aberrometry was measured in 18 cyclopleged subjects (19-24 years) while wearing Ciba Air Optix low (AOlow) and high (AOhigh) add, Bausch & Lomb PureVision low (PVlow) and high (PVhigh) add multifocals, and a Bausch & Lomb PureVision single vision (PVsv) control with the same -3.00 D distance back vertex power. Zernike polynomials were scaled to 4, 5 and 6 mm pupils. CSF was measured at equivalent distances of 6 m, 1 m and 40 cm while fully corrected with spherical trial lenses at 6m. RESULTS: AOlow, AOhigh and PVhigh induced a negative shift in primary spherical aberration (Z12) from PVsv and all multifocal SCLs induced a positive shift in secondary spherical aberration (Z24) (all p<0.01), without significantly increasing coma. Area under the CSF (AUCSF) reduced at 40 cm for all multifocals relative to PVsv (p<0.05), but was not significantly different at 6 m or 1 m. A moderate correlation (r = -0.80, p<0.005) was found between changes in Z12 and AUCSF at 40 cm for AOhigh, with an increase in negative Z12 reducing multifocal-induced loss of CSF. CONCLUSIONS: Centre-near multifocal SCLs induced a negative shift in Z12 and a positive shift in Z24. Although CSF was unaffected at 6 m and 1m it was reduced at 40 cm, possibly because changes in Z12 and Z24 were not great enough to induce a significant shift in centre of focus and increase in depth of field.

Comparison of topcon optical coherence tomography and ultrasound pachymetry.

PURPOSE: To establish within-rater repeatability and minimum measurements required for reliable assessment of central corneal thickness (CCT) using Topcon three-dimensional OCT-2000 (Topcon Medical Systems, Oakland, NJ) Fourier-domain optical coherence tomography (FD-OCT) and to test agreement against ultrasound pachymetry (USP). METHODS: Twenty participants underwent five scans using FD-OCT followed by five CCT measurements using USP. Each FD-OCT scan produced 12 meridional optical sections, giving 60 sections in total. The FD-OCT CCT was calculated from each section using Topcon FastMap software. Within-rater repeatability was assessed using intraclass correlation coefficient (ICC), within-subject variance (Sw), and within-subject coefficients of repeatability (COR) and variation (COV). Agreement was assessed using analysis of variance, simple linear regression, Bland-Altman analysis, and ICC. The minimum number of FD-OCT scans required to achieve a mean CCT within the 99% confidence intervals of all 60 measurements was calculated. RESULTS: Mean CCTs were 528 ± 27 µm (FD-OCT) and 544 ± 29 µm (USP). The FD-OCT within-rater repeatability values assessed using ICC, Sw, COR, and COV were 0.99, 5.07 µm, 14.07 µm, and 0.01%, respectively. The USP within-rater repeatability values assessed using ICC, Sw, COR, and COV were 0.96, 5.49 µm, 15.22 µm, and 0.01%, respectively. Both instruments were similarly correlated (p < 0.05), with FD-OCT underestimating CCT by 16.08 µm relative to USP. Four FD-OCT scans were required to achieve a mean within the 99% confidence interval of all measurements for each participant. CONCLUSIONS: Both instruments displayed high repeatability, with strong agreement between devices, although FD-OCT significantly underestimated CCT compared with USP. The FD-OCT agreement with USP remained strong when only four scans were analyzed.

Repeatability of internal aberrometry with a new simultaneous capture aberrometer/corneal topographer.

PURPOSE: To compare repeatability of internal eye aberrations derived from aberrometry and corneal topography (CT) measured simultaneously by the Innovative Visual Systems Discovery, against time displaced but same instrument measurement (Nidek OPD-Scan 3), and time displaced different instrument measurement (Medmont E300 and Imagine Eyes irx3). METHODS: Three aberrometry and CT measurements were captured with each instrument, except for the OPD-Scan 3 where three aberrometry scans were followed by a single CT. Measurements were repeated across 2 days. Corneal surface Zernike coefficients were derived from CT and subtracted from aberrometry to establish internal aberration coefficients. For the OPD-Scan 3, internal Zernike coefficients were derived by the instrument's software. Repeatability for second-order root mean square (RMS), spherical aberration, coma RMS, trefoil RMS, and the refraction components M, J0, and J45 were assessed using intraclass correlation coefficient (ICC). RESULTS: Intrasession repeatability was similar between the Discovery and E300/irx3, with the E300/irx3 slightly more repeatable for second-order RMS. Across days, the Discovery was most repeatable for second-order RMS (ICC 0.98) followed by the E300/irx3 (ICC 0.96) and OPD-Scan 3 (ICC 0.88). All instruments were less repeatable for higher order aberrations with only the Discovery moderately repeatable for spherical aberration and trefoil RMS (both ICC ≥ 0.75). The Discovery was highly repeatable for all derived refractive components (ICC ≥ 0.96). The E300/irx3 was highly repeatable for M (ICC 0.98) and moderately repeatable for J0 (ICC 0.89). The OPD-Scan 3 was highly repeatable for the M component (ICC 0.98) but not repeatable for the cylindrical components. CONCLUSIONS: The Discovery was highly repeatable for second-order RMS and derived refractive components. The lower repeatability for internal higher order aberrations measured with all instruments suggests caution in their use until further work is carried out to investigate sources of error and to develop methods to improve repeatability.