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Babies and Children

Introduction The contact lens practitioner is a key member of a multidisciplinary team involving paediatric ophthalmologists, optometrists and orthoptists concerned with ocular health and visual development of the child. Fitting infants and children with contact lenses is a challenging yet rewarding area of clinical contact lens practice. Contact lenses play an important role in the correction of complex refractive errors in infants and young children (…

High Ametropia

Introduction This chapter examines contact lens fitting for higher magnitudes of myopia, astigmatism and hyperopia. Prescribing contact lenses for high astigmatism ( Chapter 16, Chapter 17, Chapter 25 ) and hyperopia ( Chapter 27 ) is also covered in detail elsewhere. High Myopia In an epidemiological context, high myopia is defined as a spherical equivalent refraction of at least 5.00 D ( ) or 6.00 D…

Keratoconus

Introduction Congenital or developmental abnormalities of corneal topography include primary corneal ectasias, such as keratoconus and keratoglobus, and cornea plana ( Fig. 25.1 ). These atypical corneal shapes provide significant challenges to clinicians who are attempting to restore vision for patients with these conditions. Keratoglobus and cornea plana are relatively rare, so this chapter concentrates on the contact lens correction of keratoconus. Keratoconus is classically considered…

Sport

Introduction A significant proportion of the population participates in sports or leisure-time physical activities. For example, a world-wide metaanalysis found that among adults, walking was the most popular activity in the Americas (19% of the population), Eastern Mediterranean (15%), Southeast Asia (39%) and Western Pacific (42%). In Europe and Africa, soccer (10%) and running (9%), respectively, were top activities ( ). Sport and recreation are often…

Extended Wear

Introduction The term ‘extended wear’ (EW) has generally been applied to describe the wear of contact lenses for periods in excess of 24 hours between removal, including sleep with the lenses on the eye and regular, planned removal of the lenses. The term ‘continuous wear’ was originally used to describe prolonged wear of unspecified duration, but was discarded during the early 1980s because prolonged wear was…

Presbyopia

Introduction One of the more perceived challenging areas within contact lens practice is fitting presbyopic patients with contact lenses to allow the majority of their visual requirements to be met through the development of their presbyopia. However, the availability of newer optical designs, daily disposability and lens designs in enhanced hydrogel, silicone hydrogel and high-permeability rigid lens materials mean that there is less restriction to the…

Tinted Lenses

Introduction Eye colour is universally recognized as an important and defining natural physical characteristic of the body human, and a contact lens is an effective vehicle for modifying or enhancing this appearance for those who wish to do so. More importantly, tints can be applied to contact lenses to help normalize the appearance of disfigured eyes and help improve vision in diseased eyes. Tints have been…

Reusable Lenses

Introduction Contact lenses can be broadly categorised according to their frequency of use and frequency of replacement. Daily disposable lenses, which are worn during the day and discarded at the end of the day, are single-use, daily replacement lenses; this form of lens wear is discussed in Chapter 19 . All other lens types are reusable, meaning that lenses that are removed from the eye, cleaned…

Daily Disposable Lenses

Introduction Daily disposable lenses are one of the two versions of true, single-use-only, contact lenses – the other being extended-wear lenses. Daily disposable lenses first became available in 1994. The premier daily disposable lens was launched in the United Kingdom (later this was sold to Bausch & Lomb) and Johnson & Johnson released the 1-Day Acuvue daily disposable lens in western regions of the United States…

Rigid Lens Care Systems

Introduction This chapter reviews the care systems used with rigid contact lenses. Of course, many of the general principles of contact lens care, such as the rationale for lens cleaning and disinfection, regulatory control of the contact lens care industry and various approaches to comparing the efficacy of different solutions, have already been discussed in Chapter 10 and will not be repeated here. Disinfection and Wetting…

Rigid Scleral and Corneoscleral Lens Design and Fitting

Introduction and Historical Overview Scleral lenses were the first contact lenses used to protect the ocular surface, restore vision in keratoconus and correct simple ametropia ( ). Initially manufactured in glass and later polymethylmethacrylate, Sattler’s veil (corneal oedema) was common ( ) and required periodic lens removal to allow the cornea to recover. Other approaches to eliminate or delay the onset of corneal oedema included the…

Rigid Toric Corneal Lens Design and Fitting

Introduction The use of rigid toric corneal lenses (in preference to rigid spherical corneal lenses) is indicated under the following circumstances: 1. To improve the vision in cases where a lens employing spherical front and back optic zone radii is unable to provide the adequate refractive correction. 2. To improve the physical fit in cases where a lens with a spherical back optic zone radius (BOZR)…

Rigid Corneal Lens Design and Fitting

Introduction Fitting rigid corneal lenses is an improbable achievement. Essentially, it involves constructing a complex three-dimensional structure to sit, without the aid of any supplementary adhesive, on a vertically inclined surface while being repeatedly dislodged by a covering structure. Fortunately, the task is made easier by a number of mitigating factors: The lids help to prevent the lens falling from the eye. The change in curvature…

Rigid Lens Measurement

Introduction In contrast to soft lenses (see Chapter 7), rigid contact lenses are individually fitted and then lathe cut to meet particular optical, geometrical and material specifications. Although the manufacturing precision has improved significantly over the years, in particular with the introduction of computer numerical-controlled lathes, such improvements do not eliminate the need for careful lens inspection and measurements to ensure that only good-quality lenses are…

Rigid Lens Optics

Introduction Unlike soft lenses, which drape to fit the cornea so that on the eye the geometry of the back surface closely conforms to that of the anterior cornea, the back surface of a rigid lens (corneal, corneoscleral or scleral) maintains its shape. As a result, a tear lens of predictable form and power is generated between the contact lens and the cornea. The overall optical…

Rigid Lens Manufacture

Introduction Although lathing technology has been used to fabricate contact lenses since their invention over 130 years ago, developments over the past quarter of a century in precision engineering, materials technology and computer control systems have resulted in a capability to manufacture lenses of almost any imaginable shape – from basic spherical lens forms to highly complex aspheric designs. These developments have resulted in renewed interest…

Rigid Lens Materials

Introduction Rigid lens materials have played an important role in the development of rigid contact lenses generally and occupy a small but significant place in the range of currently available products. Much of the relevant information is contained in the patent literature, which is analysed in some detail elsewhere ( ). Polymethyl Methacrylate To appreciate the way in which rigid, as distinct from soft, materials have…

Soft Lens Care Systems

Introduction With the very notable exceptions of daily disposable lenses and extended-wear lenses that are discarded after each period of continuous wear, all contact lenses must be subjected to some form of maintenance procedure after each use. The key elements of lens maintenance are cleaning and disinfection. Contact lenses must also be safely stored in solution until they are next worn. This chapter explores the rationale…

Soft Toric Lens Design and Fitting

Introduction The use of soft toric lenses (in preference to spherical soft lenses) is indicated when there is ocular astigmatism present, be it corneal or noncorneal, that warrants correction. Unlike rigid lenses, soft lenses do not mask corneal astigmatism but rather conform to the shape of the cornea. Consequently, correcting ocular astigmatism with soft lenses requires that cylinder be incorporated into the back vertex power (BVP)…

Soft Lens Design and Fitting

Introduction Assessment of soft contact lens fit is probably the most commonly undertaken task in contact lens practice but is also one of the least discussed, possibly because it is regarded as a relatively straightforward exercise. However, soft lens fitting is not just a process of finding a soft lens that fits but also one of determining the soft lens and wearing regimen that will provide…