FALL 2023

SoftSpecialEdition is a quarterly newsletter FOR HEALTH CARE PROVIDERS that gives independent updates from the international literature on soft specialty lens-related topics. View as Webpage

World Wide Vision XXXXXI

It's a Material World

It has been noted that lens shape and design may be important factors in soft lens fitting, but let’s face it: lens material properties play a huge role in lens acceptance on the eye. Silicone hydrogel lenses were introduced in the 2000s, and their enhanced oxygen permeability represented a technological leap. One might argue that silicone hydrogels are a superior choice in comparison to hydrogel lenses. However, recent research shows that there isn't a definitive superior material; the suitability depends entirely on the wearer. The research team at the University of Zaragoza in Spain delved into the impact of soft lens wear on corneal tissue alterations. Corneal stress indicators were investigated, and over half of the participants exhibited alterations due to lens wear. Intriguingly though, no specific material was consistently found to be more responsible for these corneal changes; it varied among individuals. A similar outcome emerged when examining topographical limbus and corneoscleral junction angles. In one study that compared wear of one silicone hydrogel lens with wear of one hydrogel lens, while individual differences were noticeable, there was no conclusive evidence indicating that one material caused more significant corneoscleral alterations than the other. In essence, our evolving understanding emphasizes the necessity of personalized approaches in prescribing soft contact lenses. As we delve deeper into the intricacies of ocular interactions with contact lens materials, tailored solutions will continue to redefine the landscape of vision correction. Want to read more? Click link below for full the full story.

World Wide Vision XXXXXI - Alejandra Consejo - University of Zaragoza (ES)

Lens Choice

2023 Contact Lenses & Solutions Summary

Anita Gulmiri and Jennifer Liao from the New England College of Optometry (NECO) compiled the 2023 Contact Lenses & Solutions Summary (CLASS), which is printed as a supplemental guide to the September edition of Contact Lens Spectrum and is also available online. Most soft lenses available in the US, with their labelled material, water content, lens thickness and Dk/t are listed (as well as rigid lenses). Looking for a specific toric soft lens in a particular power? Consult the guide, and you will find it. The Contact Lens Compendium from the University of Waterloo is a similar but ongoing online lens database, which aims at presenting all lens materials and parameters available. They have a US and a CA version (drop-down menu, top right). Contact lens care systems are also covered by both guides.

CLSpectrum Supplement
Contact Lens Compendium

Toric Talk

Toric Price

Collaboration between the Department of Economics, Appalachian State University in Boone, North Carolina (US) and Eurolens Research in Manchester (UK) led to a study looking at the clinical performance and 'willingness to pay' for soft toric contact lenses in low and moderate astigmats. Subjects with binocular low-to-moderate astigmatism (−0.75DC to −1.50DC) wore pairs of soft toric and spherical soft lenses in random sequence. For the four measures of visual acuity, the toric lens outperformed the spherical lens by 0.6 to 1.1 lines, and subjective vision performance was statistically significantly better with the toric lens for the distance task. Comfort scores were not significantly different. The 'Willingness To Pay Premium' (additional fee) for a monthly supply of toric lenses (over spherical lenses) was between £13 and £16 when the toric lens provides better vision and similar comfort, as shown in the clinical study. In conclusion, consumers are willing to pay a monthly premium of around 50% to benefit from the typical experience of better vision and similar comfort for toric vs. spherical lenses, the authors state. The level of additional cost for toric lenses compared to their spherical equivalents is less than this in the market, so eye care professionals should consider that toric lenses are delivering a greater clinical return than anticipated.

Morgan et al  - Contact Lens & Ant Eye - July 2023

Toric Vision

Not all toric lenses are the same. A study by Koh et al from Japan looked at the optical quality and visual performance of different toric contact lens designs. Twenty soft lens wearers aged 20 to 39 years were enrolled, and two different daily disposable silicone-hydrogels were tested, with different stabilization systems (one by eyelid stabilization, one with prism-ballast). A spherical daily disposable silicone hydrogel was used as a control. The toric lenses provided a better corrected distance visual acuity than the spherical lens. However, differences in coma (a higher-order aberration) and subjective symptoms may occur because of the design of the toric lens. The eyelid-stabilization lens showed significantly less coma than the prism-ballast lens, and the subjective ratings for blurred and double vision were significantly lower for the eyelid-stabilization lens.

Koh et al  - Eye & Contact Lens - Sept 2023

Toric Myopia & Presbyopia Management

As noted in the previous item, finding the right toric lens can be a challenge sometimes. Studies investigating myopia management effectiveness seem to show that correcting astigmatism may be beneficial with ortho-k and with soft lenses (Kang 2021, Tomiyama 2022). This typically means moving away from daily disposables for soft lens options and into monthly or quarterly replacement (Van der Worp, Montani 2023). In progressive myopia, values of the ametropia can be extreme at times. Melissa Barnett (August 2023) offers 'Toric Tips for Succesful Fits' for presbyopia in a Contact Lens Spectrum publication. Most studies demonstrate that patients prefer multifocal contact lenses over monovision contact lenses, even in subjective or “real-world” situations, she writes. Commercially available lenses offer various replacement options and a range of multifocal designs, while custom-designed lenses allow practitioners to specify multiple parameters including base curve, diameter, and power. Custom optic zones can also be manufactured for several lens types. Options for custom monthly replacement soft toric multifocals in both standard hydrogel and silicone hydrogel materials are vast and offer combinations of sphere (+30.00D to –30.00D), cylinder (–0.75D to –10.00D), axis (any degree), and add power (up to +4.00D). And numerous custom designs, including near-center, distance-center, and aspheric near-center and distance-center, are made to order.

Pediatric Aphakia

Soft Lens Options & Fitting in Pediatric Aphakia

This study from Chicago (US) looked at soft contact lens options in the management of pediatric aphakia. Historically, the lens of choice for this indication has been a silicone elastomer lens (Silsoft SuperPlus). Due to supply chain disruption of this lens, many aphakic children require an alternative lens. Quantitative and qualitative comparisons between Silsoft SuperPlus and alternative aphakic soft contact lenses in sixty-nine aphakic eyes of 49 patients were executed. Twenty-four patients (49%), 4 (8%), and 1 (2%) were refit into Flexlens Definitive 74, Biofinity XR, and Intelliwave Pro Toric lenses, respectively. Sixteen patients (34%) remained in Silsoft SuperPlus due to personal lens surplus or inability to handle the new lens, while 2 (4%) opted for glasses. Flexlens Definitive 74 required a base curve 0.4mm steeper than the the average keratometry values. A trend was reported toward greater comfort with handling Silsoft SuperPlus; however, patients experienced fewer adverse side effects with the alternative soft contact lenses. In conclusion, the authors state that Flexlens Definitive 74 was an adequate alternative to Silsoft SuperPlus in aphakic children; however, lens parameters must be steepened.

 Shaikh et al - Contact Lens & Anterior Eye - June 2023 (open access)

Global Specialty Lens Symposium 2024

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