ORCID Profile
0000-0002-4503-9668
Current Organisations
University of Waterloo
,
University of New South Wales
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Publisher: Informa UK Limited
Date: 07-2018
DOI: 10.1111/CXO.12542
Publisher: Springer Science and Business Media LLC
Date: 21-08-2013
DOI: 10.1038/NPP.2013.214
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2013
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2016
DOI: 10.1097/OPX.0000000000000896
Abstract: 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. 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. 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). Eyes with higher amounts of corneal toricity give rise to increased amounts of treatment zone decentration in overnight orthokeratology.
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.OPHTHA.2014.09.028
Abstract: To investigate the effect of overnight orthokeratology (OK) contact lens wear on axial length growth in East Asian children with progressive myopia. A prospective, randomized, contralateral-eye crossover study conducted over a 1-year period. We enrolled 26 myopic children (age range, 10.8-17.0 years) of East Asian ethnicity. Subjects were fitted with overnight OK in 1 eye, chosen at random, and conventional rigid gas-permeable (GP) lenses for daytime wear in the contralateral eye. Lenses were worn for 6 months. After a 2-week recovery period without lens wear, lens-eye combinations were reversed and lens wear was continued for a further 6 months, followed by another 2-week recovery period without lens wear. Axial eye length was monitored at baseline and every 3 months using an IOLMaster biometer. Corneal topography (Medmont E300) and objective refraction (Shin-Nippon NVision-K 5001 autorefractor) were also measured to confirm that OK lens wear was efficacious in correcting myopia. Axial length elongation and myopia progression with OK were compared with conventional daytime rigid contact lens wear. After 6 months of lens wear, axial length had increased by 0.04±0.06 mm (mean±standard deviation) in the GP eye (P=0.011) but showed no change (-0.02±0.05 mm) in the OK eye (P=0.888). During the second 6-month phase of lens wear, in the OK eye there was no change from baseline in axial length at 12 months (-0.04±0.08 mm P=0.218). However, in the GP eye, the 12-month increase in axial length was significant (0.09±0.09 mm P<0.001). The GP lens-wearing eye showed progressive axial length growth throughout the study. These results provide evidence that, at least in the initial months of lens wear, overnight OK inhibits axial eye growth and myopia progression compared with conventional GP lenses. Apparent shortening of axial length early in OK lens wear may reflect the contribution of OK-induced central corneal thinning, combined with choroidal thickening or recovery due to a reduction or neutralization of the myopiogenic stimulus to eye growth in these myopic children.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2011
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.JTOS.2017.01.009
Abstract: To investigate the recovery of orthokeratology (OK)-induced changes in corneal nerve morphology and sensitivity following lens wear discontinuation, over a 3-month period. Sixteen myopic subjects who wore OK lenses during sleep for 3 months discontinued lens wear for 3 months. Corneal nerve morphology and sensitivity were assessed on the right eye only 3 h after waking at the pre-lens wear baseline and after lens wear discontinuation. Corneal nerve fiber density (NFD) and global nerve fiber orientation (GNFO) were assessed by s ling a 1 mm Significant changes in corneal sensitivity, NFD, and GNFO were observed at various corneal locations during the lens wear discontinuation period. In the central cornea, NFD and corneal sensitivity increased during the 3-month non-lens wear period (p < 0.01) no significant changes in NFD or corneal sensitivity were noted in the mid-peripheral cornea. Central corneal sensitivity recovered to pre-lens wear levels after 1 month of non-lens wear. Central NFD appeared to remain slightly decreased after 3 months of non-lens wear compared to pre-lens wear levels, but this difference did not reach statistical significance (p = 0.09). GNFO did not change significantly at the central cornea during the 3-month non-lens wear period, but altered in a counter-clockwise rotational direction (reversal of OK-induced change) at the mid-peripheral cornea (p < 0.05), although it did not appear to fully recover to pre-lens wear orientation (p = 0.05). OK lens-induced reduction in corneal sensitivity recovers with cessation of lens wear, returning to pre-lens wear levels shortly after lens wear discontinuation. Changes to nerve morphology induced by OK lens wear, however, appear to recover more slowly towards pre-lens wear levels. This requires confirmation in a longer non-lens wear period.
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.JTOS.2016.07.005
Abstract: To investigate changes in corneal subbasal nerve fiber density and orientation during a 3-month orthokeratology (OK) lens wear period and their relationship with concurrent changes in corneal sensitivity. Sixteen subjects wore overnight OK lenses for 90 days and were assessed at baseline, Day 30, and Day 90. Nerve images at the corneal apex and temporal mid-periphery were captured from the right eye only using in vivo confocal microscopy and analyzed to calculate nerve fiber density (NFD) and global nerve fiber orientation (GNFO). Corneal sensitivity was measured using the Cochet-Bonnet aesthesiometer at similar corneal locations. Control groups of non-lens (NL) wearing and conventional rigid gas-permeable (GP) lens-wearing subjects were also examined. Significant changes in NFD, GNFO and corneal sensitivity were observed during OK lens wear over the study period. In the central cornea, both NFD and corneal sensitivity decreased by Day 30, with further reductions at Day 90. Reduced NFD was associated with reduced corneal sensitivity. In the mid-peripheral cornea only, GNFO was rotated in a clockwise direction at Day 30, with further rotation at Day 90. Corneal sensitivity reduction plateaued by Day 30. In the GP lens-wearing subjects, only corneal sensitivity decreased by Day 30 at both corneal locations. No changes were observed in the NL control subjects. Alterations in corneal nerve morphology occur rapidly with commencement of OK lens wear and appear to underpin functional sensitivity loss. Nerve fiber orientation can provide a useful index for changes in corneal nerve morphology.
Publisher: SPIE
Date: 07-06-2000
DOI: 10.1117/12.387530
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2017
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2017
DOI: 10.1097/OPX.0000000000001096
Abstract: This work aims to characterize the relationship between tear film neuropeptide substance P and the structural integrity of the sub-basal nerve plexus in diabetes. Seventeen healthy control participants and nine participants with diabetes were recruited in this cross-sectional study. Total protein content and substance P concentrations were determined in the flush tears of participants. Corneal nerve morphology was assessed by capturing the corneal sub-basal nerve plexus using the Heidelberg Retinal Tomograph II with the Rostock Corneal Module (Heidelberg Engineering GmbH, Heidelberg, Germany) in the central cornea. Corneal nerve fiber density (CNFD) was measured using ACCMetrics (M.A. Dabbah, Imaging Science and Biomedical Engineering, Manchester, UK) on eight captured images. Comparisons between groups were made using independent s les t-tests. Correlations between parameters were analyzed using Pearson’s correlations. Substance P concentrations were significantly higher in the tears of the control group compared to participants with diabetes (4150 ± 4752 and 1473 ± 1671 pg/mL, respectively, P = .047). There was no significant difference in total protein content between the groups (3.4 ± 1.8 and 2.6 ± 1.7 mg/mL in the control and diabetes groups, respectively, P = .262). CNFD was significantly lower in the participants with diabetes compared to the control group (16.1 ± 5.7 and 21.5 ± 7.0 mm/mm 2 , respectively, P = .041). There was a moderate correlation between substance P and CNFD ( r = 0.48, P = .01). Substance P is expressed at a significantly lower level in the tears of people with diabetes compared with healthy controls. The positive correlation between substance P and corneal nerve density indicates that substance P may be a potential biomarker for corneal nerve health.
Publisher: Elsevier BV
Date: 03-2004
DOI: 10.1016/J.CLAE.2003.11.002
Abstract: The study determined the effects of packaging solution osmolality and buffering agent on soft contact lens parameters. One lens type from each FDA contact lens material category was equilibrated to phosphate buffered saline (PBS) or borate buffered saline (BBS), at three osmolality concentrations: 270, 310 and 414 mOsmol/kg. Lens diameter (LD), base curve (BOZR) and back vertex power (BVP) were measured and compared to nominal packaging label values. Statistically significant differences were found in all three parameters across all osmolality levels for both buffering agents. Etafilcon A showed the largest amount of parameter change, followed by alphafilcon A and balafilcon A. Lotrafilcon A was the least affected. LD of alphafilcon A lenses (greater than +/- 0.2 mm) and BVP of lotrafilcon A and etafilcon A lenses (greater than +/- 0.25 D) measured outside the International Standards Organization (ISO) tolerance from their packaging labels when measured in solutions that mimicked their packaging solutions. Osmolality and buffering agents influence lens parameters. Packaging solutions can vary the parameters of some lens types from their nominal value to outside the tolerance range set by ISO.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2013
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 18-04-2012
DOI: 10.1167/IOVS.11-8706
Abstract: This study was designed to map the sub-basal nerve plexus (SBNP) in the cornea of orthokeratology (OK) lens wearers. Laser scanning confocal microscopy (LSCM) was performed in vivo on three subjects: a non-lens wearer and two OK lens wearers. Scans were performed on the right eye while the left eye fixated a moving target. A total of 575, 430, and 676 contiguous images of the SBNP were taken from the non-lens wearing and the OK lens wearing subjects, respectively, and used to construct maps of the central to mid-peripheral SBNP. In the non-lens wearing eye, nerves radiated towards a whorl-like complex centered nasally and inferiorly in an overall pattern consistent with previously reported studies. In the OK lens wearing eyes, this whorl pattern was absent, replaced by a tortuous network of nerve fibers centrally, and thicker curvilinear fibers mid-peripherally, particularly in the nasal, inferior, and temporal regions. This study maps the corneal SBNP in OK lens wearers and provides compelling evidence that OK lens wear alters the normal SBNP distribution observed in healthy, non-lens wearing eyes.
Publisher: Informa UK Limited
Date: 07-2007
DOI: 10.1111/J.1444-0938.2007.00124.X
Abstract: This case report describes the appearance of fibrillary lines in the anterior stroma of a 39-year-old Asian woman wearing overnight orthokeratology (OK) lenses. The fibrillary lines were fine, slightly curved and sub-epithelial, arranged in a band-like annulus in the corneal mid-periphery. The lines were not associated with epithelial staining, although a marked Fischer-Schweitzer corneal mosaic was noted after blinking. Fibrillary lines are a relatively common finding in normal and keratoconic corneas and have been reported previously accompanying OK lens wear. Their origin is unknown and epithelial neural remodelling, corneal biomechanical stress and abrupt corneal curvature changes have been suggested as contributing factors. The appearance of fibrillary lines in our OK patient had no adverse consequences on vision or ocular health, at least in the medium term.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2007
No related grants have been discovered for Edward Lum.