Quarterly newsletter on Soft Specialty Contact Lens
Research, Developments, Designs and Materials   FALL 2013


Due to some technical difficulties at the email platform server, the FALL edition of this newsletter was sent out Saturday with most of the links not working. Apologies. The newsletter listed below should have this corrected.
                                                                                    

WORLD WIDE VISION 
Sagittal Height and Soft Lens Fitting

New Thoughts, New Understandings
It is well established that insights into the sagittal height of the anterior eye can be helpful in the fitting of both custom soft and scleral RGP lens designs. In a study of 55 normal eyes at Pacific University, we showed that, at a chord of 15.0 mm, the average sagittal height of the eye was 3,681 microns, with a range of 3,310 to 4,080 microns. In this first part of a series of three, the role of central corneal radius, corneal eccentricity and overall corneal diameter on anterior segment height are evaluated to illustrate how normal variation in the population may affect overall sagittal depth. It appears that central radius of curvature, corneal eccentricity and even diameter are actually pretty poor indicators of overall sagittal height of the eye, in contrast to the general thinking. Click here for full report.
                      

 

Patrick Caroline and Randy Kojima
Portland (OR) USA
LETTER TO THE EDITOR
How to Improve Soft Lens Fitting
Lens Design, Lens Parameters, Base Curve, Drop Out

 

'All contact lens specialists want the best fitting contact lens for each and every individual patient,' begins Helmer Schweizer in response to 'A Statement on How to Improve Soft Lens Fitting' by Peter Moest. 'There are several criteria when determining what the best fitting lens is, including Dk, replacement frequency, etc. When it comes to soft lens fitting, industry may have to provide more information on the design of the contact lenses to allow eye care practitioners (ECPs) to consider the differences between them. ECPs, on the other hand, may need to re-learn and understand the impact that such differences have and not just look at the labeled base curve on the package. It would, of course, be nice to get all the designs and all the parameters one likes within one material (brand) of contact lens, but this is not reality (and is financially not possible with today's prices and the continued competitive pressure on them).' The key point, according to Schweizer, is that academics, ECP and industry should work together to create this kind of knowledge about the fitting of soft contact lenses to make the fitting process more efficient and more effective for the benefit of the wearer. This may ultimately also reduce the dropouts that are related to suboptimally fitted contact lenses.
FROM THE WEB
Custom Soft Contact Lenses
Prescribing & Practice

The cover story of the August edition of Contact Lens Spectrum features the topic of custom soft lenses. Significant improvements have occurred with custom soft lenses in the last three years, the article states. This is largely due to the advent of latheable silicone hydrogel materials, the authors David Kading and Mile Brujic write, which have spurred RGP laboratories to invest in the technology. Newer lenses are continually being brought to market in toric, multifocal, and custom irregular cornea designs. As customization becomes more standardized, they state, we can expect that technology will drive innovation in producing contact lenses for advanced aberration control, high-definition lenses, superior customized multifocals, and computerized contact lenses.

IN THE LITERATURE
Soft Bandage Lenses after PRK
Silicone Hydrogels, Bandage, Photorefractive Keratectomy (PRK), Efficacy

 

The efficacy of two silicone hydrogel contact lenses for bandage use after photorefractive keratectomy was investigated in this study from Greece. Forty-seven myopic patients (94 eyes) underwent bilateral PRK in this prospective, double-masked, comparative study. Silicone hydrogel lenses indeed proved effective as bandage lenses after PRK due to the limited time requested for achieving complete corneal re-epithelialization. Faster and smoother epithelial healing can also be achieved. Slight differences were found between the materials tested.   

IN THE LITERATURE
Hydrogel Induced Corneal Warpage
Corneal Warpage, Corneal Topography, Pachymetry

In the series of 'classical papers' regarding soft lens fitting, this paper by Muriel Schornack in Contact Lens & Anterior Eye keeps reminding us that corneal changes beneath soft lenses do occur and need the eye care practitioners' attention. Removing the lenses on a regular basis to check for topographical changes seems wise. This paper describes three cases with severe unwanted topographical changes. One of the cases was a 14-year-old male, who reported to the emergency service at the department of ophthalmology, Mayo clinic in Rochester (USA) complaining of a 4-day history of blurred vision and photophobia in his right eye. Hypoxia may have played a role in this case. After refitting him with a silicone hydrogel material, at the one-month follow-up visit he reported good vision and comfort with the new lenses.
RESOURCES

'SURVIVAL OF THE FITTING' 

Soft Lens Fitting, Sagittal Height, Base Curve, Lens Assessment  

 

A series of three papers were presented in consecutive editions of the Global Contact journal. The first article discusses topographical changes beneath soft lenses (the R.E.S.P.E.C.T. article). The second article looks at using alternative methods, such as sagittal height, to better understand soft lens fitting. The third article in the trilogy - called 'survival of the fitting' - looks at limitations we have in everyday practice to effectively assess soft lens fits. Physiological management of the cornea, such as looking for corneal staining and other signs - as well as follow up corneal topography may prove to be of great assistance in lens evaluation rather than, or in addition to, current methods including evaluation of lens movement and centration.
EDUCATION

Custom Soft Lens Fitting for Presbyopia 

Matt Lampa & Mark André

 

As more of the optic zone is dedicated to the add power of the lens, less can be dedicated to distance and intermediate power. Once the ideal add power is chosen, it may be more beneficial to alter the add power zone size rather than alter the amount of add power. In some cases, dissimilar zone sizes or add powers can also be considered. Custom soft multifocal contact lenses can be very beneficial for patients when their prescription falls outside the limits of the typical diagnostic fitting set. Because there are unlimited combinations of parameters that can be made with custom soft multifocal contact lenses, we recommend working closely with the consultation team of the laboratory that is fabricating the lenses.

CONFERENCE

CLSS 2013    

Ocular Surface Shape, Soft Lens Fitting, Myopia Control 

 

The Contact Lens Specialist Symposium 2013 will take place 28th & 29th September 2013 in The Renaissance Hotel, Bath Road, London Heathrow. Keynote speakers will be Pat Caroline, Eef van der Worp and Randy Kojima who will take you on an exciting journey through optics - from understanding the surface of the eye to optimal contact lens fitting. Our Exhibition will guide you through lens choices as well as offer advice on how to build a successful, sustainable business. www.clss.eu
In this Edition:
World Wide Vision
Letter to the Editor: 'How to Improve Soft Lens Fitting'
Custom Soft Lenses
Soft Bandage Lenses after PRK
Corneal Warpage
Survival of the Fitting
Education
CLSS

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