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Welcome to our monthly research update |
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Research Update is a resource available exclusively to IACLE and BCLA members to support your teaching and practice. Each month we send you a summary of some of the interesting findings appearing in peer-reviewed journals that month. Our aim is to help you keep up to date with the latest contact lens and anterior eye research, and to locate articles when you want to know more about a particular topic. |
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More information on Research Update and how to use it in your contact lens teaching here. Access archived issues via Member Login under Research. |
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Special Issue – February 2019 |
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Scleral Lens Special Edition
By now nobody doubts that scleral lenses work; since the resurgence of modern scleral lens fitting,many patients who did not have a satisfactory visual correction are visually rehabilitated because of access to this modality.
In past decade, scleral lenses have become very popular as well as one of the main lens modalities for irregular and challenging corneas.‘At the same time, this modality is still in its infancy, and we are still investigating and experiencing some growing pains,’ say the Guest Editors for this special edition of Contact Lens & Anterior Eye. This edition presents a number of these ‘growing pains’, including issues such as potential limited tear filmexchange and oxygen delivery to the cornea, and changes to the ocular surface as a result of scleral lenswear.
Here are some excerpts from the issue.
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The IACLE Education Team |
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Journal reviewed in this issue |
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JOURNAL |
VOLUME AND ISSUE NUMBER |
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Contact Lens & Anterior Eye |
42:1 |
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PATIENT OUTCOMES |
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Visual and physiological outcomes of scleral lens wear |
To describe patient-specific outcomes of scleral lens wear utilizing a variety of lens designs, Schornacket al administered a web-based survey to eye care providers who prescribe scleral lenses.A total of 292 valid responses were received from 26 countries. The most commonly reported indication for scleral lens wear was corneal irregularity (87%) followed by ocular surface disease (8%). Patients with corneal irregularity experienced the greatest improvement in visual acuity. Ocular surface condition improved in patients with both corneal irregularity and ocular surface disease.
Cont Lens Anterior Eye 2019;42:1 3-8. Click here for full text |
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FIT ASSESSMENT |
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Strategies for fitting and assessing scleral lenses |
The SCOPE (Scleral Lenses in Current Ophthalmic PracticeEvaluation) study group designed and administered a 22-item electronic survey regarding scleral lens fitting and assessment strategies to attendees of the 2017 Global Specialty Lens Symposium. Of 95 practitioners responding, new prescribers considered base curve first (60%) while experienced prescribers considered sagittal depth first (63%) in their initial scleral lens selection. Among practitioners with greater than 5 years of scleral lens experience, a consensus has emerged for best practices.
Cont Lens Anterior Eye 2019;42:1 9-14. Click here for full text |
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TOPOGRAPHY |
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Placido corneal topography data and fitting parameters |
Macedo-de-Araújo et al analyzed the relationship between corneal sagittal height and asymmetry parameters derived from Placido-video-keratoscopy with the parameters of fitted scleral lenses (ScCLs). Corneal topographies were measured in 126 eyes with irregular and regular corneas. Estimated Height (EHChord) parameters were taken for a chord equal to the diameter of the lens that each subject was wearing at different semi-meridians. These outcomes were correlated to ScCL parameters that subjects were wearing after 1 month. EHChord attributes were the parameters that best correlated with the ScCL sagittal height.
Cont Lens Anterior Eye 2019;42:1 20-27. Click here for full text |
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TEARS |
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Tear dynamics under scleral lenses |
This prospective, double-masked, randomized, bilateral, crossover study was conducted by Tse et al to evaluate post-lens tear dynamics at two different time points during scleral lens wear. All subjects wore scleral lenses for 5h on three separate visits. Out-in measurements were collected at 5h post-lens insertion in Group 1 (10 subjects) and compared with those obtained at 20min of lens wear in Group 2 (10 subjects). Tear flow into the tear reservoir under a scleral lens on these healthy corneas occurred at 20min and 5h after lens insertion.
Cont Lens Anterior Eye 2019;42:1 43-48. Click here for full text |
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OXYGEN |
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Corneal oedema with sealed minisclerals |
Vincent et al examined the magnitude and time course of central epithelial, stromal and total corneal thickness changes during sealed miniscleral lens wear. High-resolution OCT images were captured over an 8h period of miniscleral wear in 15 young, healthy participants with normal corneas. Scleral lens-induced oedema was stromal in nature. A significant increase in total corneal thickness was observed 15min following lens insertion which stabilised 45min after insertion and peaked after 90min of wear, while central epithelial thickness gradually decreased throughout lens wear. A greater initial central corneal clearance resulted in reduced oxygen delivery to the cornea, which had minimal short-term impact in healthy eyes.
Cont Lens Anterior Eye 2019;42:1 49-54. Click here for full text |
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FLEXURE |
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Centre thickness and miniscleral lens flexure |
To investigate the influence of centre thickness on miniscleral lens flexure and the association between lens flexure and scleral toricity, Vincent et al recruited nine healthy young participants with normal corneas and fitted them with 16.5mm minisclerals with centre thicknesses of 150, 250, and 350μm. Lens flexure was measured using a videokeratoscope. Decreasing the centre thickness from 350μm to150μm resulted in <0.25D increase in lens flexure for a high Dk and low modulus material. Scleral toricity >200μm was associated with more in-vivo lens flexure, with implications for lens designs for these eyes.
Cont Lens Anterior Eye 2019;42:1 63-69. Click here for full text |
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CONTRAINDICATIONS |
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Scleral lenses: to fit or not to fit? |
Fadel & Kramer’s review aims to illustrate the conditions for which scleral lenses (SL) are potentially contraindicated or require caution, namely: low endothelial cell density; Fuchs’ endothelial corneal dystrophy; glaucoma (because of the risk of increased intraocular pressure, and the existence and location of draining devices and blebs); or overnight wear. When benefits outweigh risks, careful documentation and achievable baseline measurements, photography, and other ocular examinations are helpful, and frequent follow-ups should be scheduled. Improved knowledge of SL limits should reduce the risk of adverse events and increase the likelihood of fitting success.
Cont Lens Anterior Eye 2019;42:1 92-103. Click here for full text |
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For more information on Research Update visit www.iacle.org. |
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