YEAR
2015
ISSUE
No. 4
Quarterly newsletter on Soft Specialty Contact Lens Research, Developments, Designs and Materials
WORLD WIDE VISION
Customized Soft Lenses based on Sagittal Height Segments

Whether standardized or custom made, most lens designs are monocurves, bicurves or apheric lens designs. Due to flat fitting and the resulting deformation, soft lenses change their characteristic shape on-eye, induce tension and shift power to minus in vivo. It would be more ideal to have a corneal alignment soft lens fitting technique as with RGPs. The challenge of this objective is to design a soft lens with perfect fitting accuracy. When we look at the shape of the cornea, we can identify three different zones from center to periphery. The center of the cornea is approximately spherical, followed by an elliptical zone with different degrees of flattening. Using this knowledge, we have tried to design a contact lens that includes three different SAG-zones conforming to the shape of the cornea. A critical and nearly incalculable point for best lens design is the measurement of the corneo-scleral profile, which includes the peripheral cornea, corneo-scleral junction angle and the limbal sclera. The angle of the corneo-scleral junction tends to be sharpest at the nasal area and flatter elsewhere. However, it is almost impossible to accurately determine the corneo-scleral junction with the slit-lamp as used by most contact lens practitioners. Therefore, we designed a SAG3-zone lens with a tangential character following a non-axial radius that flattens toward periphery and therefore covers a large number of different corneo-scleral profiles. We can control SAG1, SAG2 and SAG3 segments individually by modifying their shape and/or changing the angles between the zones. The shape data is derived from corneal topography. It is clear that a topographic system that is capable of a larger measuring zone is desirable and provides better results. New technologies can achieve this in a better way in the future.

Mario Rehnert
Product engineering and Project Management at Hecht Contactlinsen GmbH (Freiburg, Germany)
Modern Role of Soft Lenses for the Irregular Cornea
Irregular Cornea, Soft Lens Wear Time, Lens Comfort, Corneal Physiology.

Mary Jo Stiegemeier in Contact Lens Spectrum looks at managing irregular corneas with soft lenses. Today, there are a number of ways to utilize soft lenses in the care of irregular cornea patients, she writes. Higher-modulus soft lenses can mask irregular astigmatism in the early stages of keratoconus, and we have used soft lenses as a base lens in piggyback lens systems, which continues to work well for managing keratoconus. However, these options may not be enough as a patient progresses in the disease process. In recent years, new soft lens designs have become available that can help extend patients' wear time, improve comfort and physiology and change that contact lens continuum. Today, advances in both specialty soft contact lenses and in our knowledge of the corneal, limbal and scleral contour make this possible, as specialty lens laboratories can customize soft lens powers, thickness, peripheral systems, diameter and toricities to help improve patients' vision, comfort and wearability. A number of case reports are presented in the article.

Stiegemeier, Contact Lens Spectrum - May 2015
Subjective versus Objective Soft Lens Evaluation On-Eye
Soft Lens Centration, Horizontal Lag, Post-blink Movement, Push-up Recovery

Lurdes Belda-Salmer�n, Tom Drew, Lee Hall and James Wolffsohn looked at the usefulness of subjective soft lens evaluation on-eye. Soft lens centration, horizontal lag, post-blink movement in up-gaze and push-up recovery speed were assessed subjectively (by four observers) and objectively from slit-lamp biomicroscopy captured images and video. They found that experienced observers were variable in their estimations, that subjective estimates used less range than objective measures did, that subjective estimates had lower precision and that subjective estimates generally had poorer repeatability compared to objective measures. The investigators concluded based on this that objective image analysis provides an accurate, reliable and repeatable assessment of soft contact lens fitting characteristics, making it a useful tool for research and optimization of lens fit in clinical practice. Eye care practitioners should be aware of this, and future technology may aid in objective assessment to improve soft lens evaluation on-eye.
Custom-Made Soft Lenses in Keratoconus with Intracorneal Ring Segments
Intracorneal Ring Segments, Custom-Made Lenses, Visual Acuity 

To analyze the feasibility of a custom-made silicone hydrogel contact lens in keratoconus with intracorneal ring segments, 30 eyes of 22 patients were reviewed, with an average follow-up time of 10.3 months. The geometry of the fitted lenses consisting of lens-full periphery and sector management control were compared. Statistically significant improvement was observed between corrected spectacle distance visual acuity (CDVA) and visual acuity with the custom-made lenses (CLVA). Twenty sector management control designs were recorded and associated with lower levels of CDVA (0.36 vs. 0.18) and CLVA (0.06 vs. 0.01) compared to those eyes fitted with lens-full periphery designs. No statistical differences were found in the amount of differences between flat and steep simulated keratometry values or wearing time between both sub-groups. Conclusion: fitting custom-made silicone hydrogel lenses in keratoconus with intracorneal ring segments is a feasible treatment with a low rate of complications and adequate visual acuity and wearing time. Photo: Henny Otten - Visser Contact Lenses

Fern�ndez-Vel�zquez, Fern�ndez-Fidalgo, Contact Lens & Ant Eye, June 2015
Visual Performance of Single Vision and Multifocal Contact Lenses in Non-Presbyopic Myopic Eyes
Multifocal Lenses, Single Vision Lenses, Decentation, Aberration.  

To assess visual performance of single vision and multifocal soft contact lenses, 44 myopic participants (aged 18-35 years) were fitted bilaterally with a control lens and at the four follow-up visits with a total of 16 study lenses (5 single vision, 11 multifocal lenses). After 1h of lens wear, participants rated (scale 1-10) vision clarity (distance, intermediate and near), magnitude of ghosting at distance, comfort during head movement, and overall comfort. Distance high-contrast visual acuity, central refraction and higher-order aberrations, and contact lens centration were measured as well. They found that single vision lens design differences had no impact on subjective vision, but visual acuity was better with lenses that have increased negative spherical aberration. Decentered lenses reduced vision rating scores. Subjective measures were more sensitive indicators of vision quality than objective measures were, which may be an important tool in clinical practice.

Fedtke et al, Contact Lens & Ant Eye, July 2015
OCT Imaging of Bandage Lenses for Epithelial Healing after Photorefractive Keratectomy
PRK, Bandage Soft Contact Lenses, Comfort, Epithelial Healing.

The purpose of this study was to evaluate the efficacy of two silicone hydrogel bandage lenses on epithelial healing following photorefractive keratectomy (PRK) with anterior segment optical coherence tomography (OCT). At the end of the procedure, one eye of each patient was fitted with a lotrafilcon B contact lens whereas the fellow eye was fitted with a comfilicon A lens. Patients were examined on the day of surgery and at days 1-5 postoperatively. The average epithelial defect size for comfilcon A and lotrafilcon B was 32.7mm2 vs. 33.3mm2 at day 1 and 13.1mm2 vs. 14.5mm2 at day 3 postoperatively (p=0.018). Average re-epithelialization time was 3.1 days for comfilcon A and 3.6 days for lotrafilcon B (p=0.03). Mean subjective discomfort score was 2.25 in eyes with lotrafilcon B and 1.64 in eyes with comfilcon A on the first exam the day after surgery. The investigators concluded that OCT is a reliable, noncontact method for assessment of re-epithelialization under contact lenses after PRK. Another study by Mohammadpour et al, compared two silicone hydrogel bandage contact lenses in reducing pain and discomfort after PRK. Lotrafilcon B lenses resulted in significantly less postoperative pain and discomfort, especially in the first 24h after the procedure.

Elia�ık et al, Contact Lens & Ant Eye, July 2015
Custom Soft Lens Update
GPLI live webinar available online (with COPE-approved CE credit)
 
  Dr. Susan Resnick from New York City (US) covers the topic of customized lenses fully from A to Z, as presented in the August 2015 Custom Contact Lens Education platform of the GPLI. She digs into soft contact lens use for the irregular cornea, for the presbyope - and also for the normal cornea and for the emerging topic of myopia control. She also looks at materials that we can use. Aberration control lenses are discussed as well. She describes the use of high-molecular-weight fluorescein to evaluate soft lens fit. Different fitting techniques for custom soft lenses are discussed, based on diameter and sagittal height rather than using central keratometry values as the prime basis for the lens fit. A fitting nomogram is introduced for lens thickness in keratoconic eyes based on best-corrected visual acuity and cone location. In some cases, soft custom-made lenses can be an alternative to sclerals, she states. The highly recommended 1-hour webinar can be seen in full via the link below.
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