Wydanie 3/2009

Soczewki do korekcji astygmatyzmu - nowoczesne konstrukcje i rezultaty dopasowań

Astigmatic Lenses - Modern Designs & Clinical Applications

Ioannis G. Tranoudis DO, MSc, PhD

Professional Affairs Manager Europa Centralna i Południowo-Wschodnia Johnson & Johnson Vision Care

Summary: Improvements in lens design over the past decade have made toric soft lenses a popular prescribing option for astigmatic patients. New manufacturing techniques have brought improvements in reproducibility and made toric soft lenses simpler and quicker to fit. A major advance has been the introduction of toric soft lenses utilizing the Accelerated Stabilisation Design (ASD). This was developed after much research to understand what happens during blinking and the interaction between the lids and the lens. ASD lenses have shown a number of advantages over traditional designs in reducing variable vision and blur. In prism-ballasted and dual-thin zone designs, the lens can interact with the lid(s) during the blink, even when correctly aligned, which can in turn result in unwanted lens rotation. With ASD, when the lens is in the correct position there is minimal destabilizing interaction with the lids. Only when the lens is misaligned, for instance, when first placed on the eye, does lid interaction have maximum effect. The upper and lower lid forces therefore continually orient and stabilize the lens to return it to its correctly orientated position. For the practitioner achieving a stable and reliable fit while minimizing chair time are key factors in successful toric soft lens fitting. Unstable lens orientation and variable visual acuity were among the reasons practitioners have traditionally cited for not fitting more soft torics. For the wearer, fast lens orientation is equally important so that they can achieve optimal vision correction as quickly as possible after lens insertion every morning. Recent studies have therefore focused on the rotational stability of toric soft lenses and have led to a better understanding of factors influencing lens fit. On one hand orientation stability and position are essential for good visual performance and patient satisfaction with toric soft contact lenses. ASD lenses offer significant advantages over prism ballasted designs for visual performance. On the other hand practitioners need to understand the patients? visual needs and lifestyle in their usual environment. Recent studies have led to a reappraisal of toric soft lens design and fitting. New assessment techniques help determine the best vision performance results both within and beyond the consulting room. The recent peer-reviewed results show the importance of toric soft lens design on visual performance. In clinical practice, ASD lenses are especially useful in dynamic situations where clear, stable vision is critical, such as when watching or playing sport. However, it is worth remembering that most astigmatic patients lead active lives that challenge lens performance in many different ways, even in sedentary situations and occupations. Everyday activities such as looking in a rear-view mirror when driving or watching TV when lying down are other demanding visual situations where rotational stability is important and ASD lenses would offer significant advantages.