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Microbiology, Lens Care and Maintenance

Effective care and maintenance of contact lenses is central to the safety and success of contact lens wear ( , ). Ineffective and noncompliant lens care are two of many reasons for cessation of wear contributing to the number of so-called contact lens dropouts. However, over the last three decades there has been a significant decline in the perceived importance of lens care due largely to:…

Anatomy and Physiology of the Cornea and Related Structures

Current anatomical literature has widely adopted the terminology recommended by the and published in Terminologia Anatomica (1998). More than 100 years ago it was recognised that eponyms are not descriptive and that more uniform anatomical terms should be developed to promote better and clearer communications involving anatomical structures. The first text on anatomical nomenclature ( Nomina Anatomica ) was thus published in Latin in Basel, Switzerland…

Contact Lens Materials

Introduction An overview of factors that influenced materials development To appreciate the current spectrum of commercial contact lens materials and their structural variations, it is useful to summarise briefly the way in which materials have developed over time. Accounts of early attempts to improve vision by use of a lens contacting the eye are limited to a few isolated observations ( ). Practical success was not…

The History of Contact Lenses

Introduction * Updated for the 6th edition by Timothy J Bowden and Jacqueline Lamb from previous work by Anthony Sabell The development of contact lenses is long and complex, starting mainly in Germany and then moving across Europe to the USA before going international. The authors have tried to keep things chronological; however, these developments do not fall into a nice convenient timeline. As you read…

Endothelial Polymegethism

In the 1980s, a series of articles alerted contact lens practitioners to a potentially adverse effect of contact lens wear that could be observed in the cornea – namely, endothelial polymegethism ( Fig. 32.1 ). These observations were made soon after Zantos and Holden published their reports of transient changes in the endothelium induced by contact lenses (endothelial blebs; see Chapter 30 ). A picture of…

Endothelial Cell Redistribution

Concern that contact lenses may be adversely affecting the corneal endothelium has resulted in endothelial examination becoming a routine procedure during biomicroscopic examination of the cornea of contact lens wearers ( Fig. 31.1 ). This concern can be traced back to the original observation by Zantos and Holden in 1979 of acute transient changes (‘blebs’) in the corneal endothelium associated with contact lens wear (see Chapter…

Endothelial Blebs

Before 1977, it was thought that contact lenses could only affect the cornea by direct mechanical influence or oxygen deprivation. Because the endothelium is located on the posterior surface of the cornea and is known to obtain all of its required oxygen from that dissolved in the aqueous humor, this tissue layer was thought to be immune to the effects of contact lenses. The first clue…

Endothelial Bedewing

Eye care practitioners from time to time will observe deposits, such as keratic precipitates, on the endothelial surface. These may be benign or may be associated with a broad range of uveal responses. In 1979, McMonnies and Zantos described the appearance of endothelial deposits of uncertain origin in patients who were intolerant to contact lens wear ( Fig. 29.1 ). They described this condition as ‘endothelial…

Corneal Warpage

Because contact lenses are in direct contact with the eye, it stands to reason that physical forces can act to change the shape of both the lens and the eye. Indeed, both types of change have been documented and both can have important clinical sequelae. This chapter shall concentrate on changes in ocular shape induced by contact lens wear. Primary consideration will be given to corneal…

Microbial Keratitis

As explained in some detail in Chapter 26 , microbial keratitis is a particular type of corneal infiltrative event (CIE) characterised by the fact that replicating microorganisms are the cause. Microbial keratitis can be ‘self-limiting’, whereby it develops to a certain level of severity and then subsides, perhaps only resulting in mild discomfort at the peak of its development. A case of microbial keratitis may be…

Corneal Infiltrative Events

One of the most challenging aspects of contact lens practice is the diagnosis and management of potentially sight-threatening microbial keratitis (MK). When involved in any such form of clinical decision-making, practitioners rely on their own clinical experience and draw upon guidance that can be found in the relevant literature. This latter aspect has become problematic. Notwithstanding the evolution of a solid body of basic and clinical…

Corneal Neovascularization

Although reports of contact lens–induced corneal neovascularization can be traced back as far as 1929 it is only in the past five decades that this problem has attracted the attention of contact lens practitioners at large. A variety of terms can be used to describe the vascular response of the cornea to lens wear. This has unfortunately resulted in some ambiguity in the literature, with various…

Deep Stromal Opacities

A limited number of reports have been published in the literature detailing the appearance of deep stromal opacities in the eyes of contact lens wearers. As will be discussed in this chapter, the evidence in some of these reports supporting the notion that deep stromal opacities are caused by contact lens wear is not entirely convincing. However, the possibility of a causative relationship in some of…

Stromal Thinning

As discussed in Chapter 22 , stromal oedema is a reliable indicator of the level of hypoxic stress induced by contact lens wear. It is an acute response in that the oedema will increase to steady state within a few hours when the cornea is subjected to hypoxic stress and will return to baseline within a few hours of the hypoxic stress being removed. Of course,…

Stromal Oedema

Contact lens–induced corneal oedema was recognised in the first two written accounts of the clinical application of contact lenses published over a century ago. In his original treatise on contact lenses, published in 1888, Adolf Fick noted that the cornea became cloudy within hours of insertion of a glass haptic shell. Although Fick would not have been aware of the exact cause of this disturbing pathological…

Epithelial Wrinkling

Epithelial wrinkling is a severe ocular complication of contact lens wear and is characterised by the appearance of a series of deep parallel grooves in the corneal surface, giving the impression of a ‘wrinkled’ effect ( Fig. 21.1 ). This condition was originally described as ‘epithelial folds’ by Quinn and was later described more fully by Lowe and Brennan, who coined the term ‘corneal wrinkling’. Epstein…

Epithelial Oedema

A small number of vacuoles and/or bullae (singular: ‘bulla’) can sometimes be observed in the corneas of contact lens wearers. Although they appear to be clinically innocuous, vacuoles and bullae can be confused with other small epithelial inclusions that have potentially more serious clinical ramifications, and it is for this reason that their clinical presentation is given due consideration in this book. One of the earliest…

Epithelial Microcysts

The first report of the appearance of corneal epithelial microcysts in association with contact lens wear was published in 1976 by Ruben and co-workers. As will be outlined in this chapter, these authors were correct in surmising that ‘corneal microcysts are evidence of chronic changes in the … epithelium …’. This observation was confirmed in 1978 by Zantos and Holden (who used the term ‘microvesicles’) in…