The field of medical contact lenses spans a potential gap between the disciplines of ocular surface medicine and refractive contact lens fitting. Contact lenses can be used as medical devices to treat ocular surface disease. In contrast, contact lenses worn for refractive purposes can cause medical problems. In addition, there are patients with eye problems such as allergy who would like to wear contact lenses for refractive purposes, but may be exposing themselves to a greater risk of medical problems.

The fields of ocular surface medicine and refractive contact lens fitting commonly come under the care of two different professions – ophthalmologists for the former and optometrists for the latter. This book will help individuals from either profession to bridge this gap. Contact lens fitters will gain the medical knowledge needed to diagnose pre-existing conditions and complications, apply simple medical care and decide when to refer the patient. Similarly, doctors in the emergency room or receiving referrals will learn about contact lenses and how they may have caused a problem. In addition those from either profession will benefit from the knowledge of how to use therapeutic contact lenses to treat medical conditions.

Elisabeth Millis has a background in ophthalmology, but her work with gurus in medical contact lenses, and then as a well-recognized expert in her own right, has given her a wealth of experience on which to draw when writing this book. The practical tips she is able to pass on will facilitate the care of the trickiest clinical conditions and the most difficult of contact lens fits.

The ocular surface is a complex environment. Any clinical picture can be multifactorial in origin,

and any condition can have a variety of secondary effects. The early chapters outline the skills in clinical history-taking and examination technique needed to unravel the presenting symptoms and signs and identify the problem. The later chapters describe how contact lenses can be used to treat ocular surface disease and complex refractive errors. There are discussions of some of the newer techniques and materials, such as digital photography, projection-based topography and silicone hydrogel lenses.

Dr Millis has selected for coverage in greater detail some of the areas causing particular difficulty in the clinic. She highlights the differences in the normal ocular surface and refractive status of older patients, the importance of changes to the ocular surface physiology when the eye is closed, and the use of topical medications in contact lens wearers.

The frequent subheadings, tables and boxes make the text easy to read and assimilate, and the ample clinical photographs contribute to it being a valuable handbook for trouble-shooting in the clinical setting. It is easy to follow-up points of particular interest due to the extensive bibliography in each chapter.

I therefore congratulate Elisabeth on giving us a book which draws together experience from both the medical ocular surface and contact lens fields. I highly recommend it to ophthalmologists and optometrists alike, and even those specialising in the field will find valuable tips from which to learn.

As an ophthalmologist who has specialized in fitting contact lenses both in hospital and private practice, I have been particularly concerned with those who have medical indications for such lenses. This book assumes a basic knowledge of contact lens fitting, although some suggestions are made for fitting in particular circumstances. Instead emphasis is placed on aspects such as inflammation and hypersensitivity, the evaluation of the older patient, the changes occurring in the closed eye, and pharmacology

and therapeutics. The advent of silicone hydrogel lenses has improved the prospects for extended wear, and their use in cases of corneal vascularization is discussed. A short chapter on keeping and maintaining clinical records has been included. It is hoped that greater understanding of these factors will help the practitioner to safely and successfully fit lenses to a wide range of patients.

My grateful thanks to Jonathan Walker for his advice, and to Melanie Corbett for all the helpful advice she has given me throughout the preparation of the manuscript and who willingly agreed to write the foreword. To Anita O’Sullivan, my secretary, for her tireless help with all the administration and to my husband Tom for all his support when the going got tough.

I would also like to thank the following for providing many of the illustrations:

John Dart for Figs 6.5 and 6.7

Andrew Gasson for Figs 2.2, 2.5, 2.7, 4.1, 5.3, 5.4, 5.5, 5.8, 5.9, 5.11, 5.12, 5.15, 5.16, 5.18, 7.1, 7.5, 9.5 and 11.2

Kathy Dumbleton for Fig. 5.10

Jack Kanski for Figs 2.4, 3.1, 3.2, 3.3, 3.4, 9.1, 9.2, 9.6, 9.9 and 9.10

Michael Loughnan for Fig. 2.3 Ian Mackie for Figs 7.6 and 7.7

Michael Wilson for Figs 2.1, 7.1, 7.3 and 7.4 Steve Lennox of SCL Contact Lenses for Figs

12.2 and 12.3

Karl Southern of The Western Eye Hospital, London for Figs 5.1, 6.1, 6.2, 6.3, 6.6, 6.8, 8.3, 8.5, 9.3, 9.8, 10.4, 11.4, 12.1, 12.4, 12.5, 12.6 and 13.2.

Finally, my gratitude to the two people without whom this book would not have been completed – my editors Caroline Makepeace and Kim Benson, for their expertise and patience.

CHAPTER CONTENTS

History and examination 1 Examination 2

Fitting contact lenses with videokeratoscopy 8

Photography of the anterior eye 12 Teaching appointment 14 Follow-up examination 14 References 15

Further reading 15

HISTORY AND EXAMINATION

Initial visit

All potential and current contact lens wearer should undergo a full ophthalmic history an examination (Tables 1.1 and 1.2) at their first visit to

●exclude any conditions that may contraindicat lens wear

●record any abnormalities

●identify and treat conditions such as blephariti before lens wear.

Many excellent texts describe the routine exam ination of the eye, and the indications and con traindications for lens wear. This chapter outline these points, and looks in greater detail at the par

Table 1.1 Initial patient examination

Patient history

General medical history Family history

Contact lens history Visual acuity

General examination, including hands and fingernails Full slit-lamp examination including intraocular pressure

measurement

Keratometry and topography Refraction

Ophthalmoscopy Assessment tear film Eversion upper lid Corneal sensitivity

Table 1.2 Factors affecting choice of lens and mode of wear

Ocular condition, including refraction

Type of employment

Sports and hobbies

Environmental conditions

Special visual needs

played by modern technology in both the examination and the recording of the findings.

History of the present condition

The contact lens history will cover the present symptoms and signs as described by the patient. The information should not be “interpreted” by the examiner, but recorded as described by the patient. In the event of the notes or the diagnosis being reviewed, the patient’s description may be more informative than a clinician’s opinion of what was said.

The duration of the symptoms and signs will determine whether the condition is acute or chronic. Details of previous similar episodes, the degree of resolution, and whether it is spontaneous or the result of medication, may all suggest the nature of the condition. A lens-related problem is likely if there is improvement when the lens is removed from the eye and the problem recurs when the lens is reinserted.

Medical history

Details of the patient’s general health, including allergies, asthma, eczema, hay fever, diabetes and other general medical conditions, and any medication must be sought:

●dry eyes and contact lens discoloration may be due to systemic medicines

●drugs such as amiodarone and tamoxifen may cause corneal deposits

●tricyclic antidepressants may result in blurred vision and raised intraocular pressure.

Current use of topical corticosteroids would normally contraindicate contact lens wear and a

past history of topical or systemic use may be complicated by cataract formation or glaucoma. Patients do not always volunteer this information and should be asked directly if they take any tablets or other medication.

Specific questioning may also be needed to elicit the use of preparations not prescribed by a medical doctor because many patients do not think to include homeopathic, herbal or home remedies as “treatment”.

Family history

Any family history of systemic or ocular disease, or atopy should be recorded.

Contact lens history

If the patient is a new lens wearer the reason for wanting contact lenses should be determined because this may influence the type of lens selected. If the patient has worn lenses previously, the lens type or types, the wearing regime, and any problems arising either from the lenses or the solutions used must be documented.

EXAMINATION

Observation of patients begins as they enter the room. Conditions such as arthritis, rosacea, red eye, heterochromia, or lid and pupil anomalies (Fig. 1.1) may affect lens wear and are often best viewed from a distance in a good light, when the two eyes are more easily compared.

Patients who are normally contact lens wearers who attend the consultation wearing spectacles should be asked why. Have they been told to attend without having worn lenses for a period of time? Are they having difficulty with lens wear? Have they lost a lens or run out of supplies of disposable lenses?

This is an opportunity to observe the patient’s hands and fingernails. Is there any condition that might make lens handling difficult? Are the nails clean and reasonably short? Some patients wear artificial nails and these are more prone to causing soft lens damage.

The visual acuity for each eye separately and for near and distance is recorded at each visit.

Figure 1.1 Soft contact lens wear in a patient with lens opacities and coloboma.

A careful note should be made of whether the visual acuity was measured unaided, with glasses, or lenses. Failure to record visual acuity may lead to medicolegal problems.

A complete, systematic ophthalmic examination is carried out, including an assessment of corneal sensation and eversion of the upper lids, which is often best achieved by grasping the lid margin and rolling the lid over a cotton bud. It is important that the lid margins are examined carefully on the slit lamp to exclude meibomian gland disease and blepharitis, and that the tear film is examined before installation of fluorescein or other drops (see Ch. 2).

The clinician identifies and records all abnormalities. A comparison of the two eyes may yield vital information. The full range of slit-lamp magnification and beam width is used to examine any lesion, and a detailed description of the findings including size, color and situation is made and recorded by drawing, or by photographic or image capturing techniques (see below).

Grading scales such as those by Efron1 and the Cornea and Contact Lens Research Unit (CCLRU)2 may be used to monitor any change and may be useful if examination is undertaken by different clinicians.

Initially it is more important to have an accurate description of a condition than to identify it.

All abnormalities whether pathologic or nonpathologic must be recorded because patients tend to examine their eyes more closely when wearing contact lenses and may think that a problem present before lens wear has been caused by the lens.

With modern rigid, gas-permeable and sof lenses refraction can usually be undertaken o removal of the patient’s lenses. For those few stil wearing polymethylmethacrylate (PMMA) lenses removal should precede refraction by 3 or mor days. If the patient cannot manage without lenses for example in cases of keratoconus, it may be pos sible for the patient to manage with one lens for few days and to refract one eye at one visit and th other a week or so later.

The fit, parameters and general condition o any lenses worn by the patient should be assesse and entered in the records.

Corneal topography

It is essential to measure corneal curvature whe fitting any type of lens. This is most important i the fitting of rigid lenses. For fitting soft lense measuring corneal curvature is useful as a base line record, for comparison in the future, and as guide to selection of the trial lens, and should b carried out when soft lenses are fitted.

Keratometry

The most commonly used method of measurin corneal curvature is the keratometer based o Helmholz’s assumption that the central cornea i spherocylindrical. It has been used as the standar with which all other methods are compared.

The corneal surface acts as a convex mirror which creates a virtual image behind the cornea The keratometer measures an area of 2.8–4.0 mm centrally, depending on the corneal curvature an type of instrument. The size of the image is deter mined by the anterior corneal surface – a stee cornea results in a small image and a flat corne a large image.

The keratometer measures the radius of curva ture of the cornea in millimeters. The same corne may provide different readings, depending on th instrument used. Different types of keratometer us different mire separations, so the area of reflectio is different, or may use different refractive indice so the same radius gives differing surface powers

If a lens support is used it is possible to use th keratometer to measure the back optic zone radiu (BOZR) of a rigid lens.

Automated keratometry

Automated keratometers measure different areas of cornea (Canon 3.8 mm diameter, Humphrey 2.6–3.24 mm) and use different algorithms for their calculations. Accuracy and repeatability of measurements is high for test spheres and normal corneas.3,4 Rapid, accurate measurements are obtainable in most cases, but the manual keratometer may be able to record data over a wider range (e.g. in cases of corneal irregularity and high astigmatism, and in those with blepharospasm or head tremor, when results are not obtainable with the automated instrument).

Handheld autokeratometers are now available and are useful in the operating theater or as part of a domiciliary ophthalmologic examination, and may appear less frightening for children.

Photokeratoscopy

The photokeratoscope uses the principle of Placido’s disc to produce a photographic record of the reflection of a series of black and white illuminated concentric rings. Qualitative information is obtained from a Polaroid photograph as the mires appear distorted if there is irregular astigmatism. Narrowing of the space between mires suggests steepening of the cornea and widening suggests flattening, but tear film abnormalities and epithelial irregularities may cause difficulties in interpreting

the findings. Measuring the diameter of each ring allows the shape factor to be calculated.

Videokeratoscopy

Reflection-based systems Videokeratoscopy (VKS) has superseded photokeratoscopy, but most systems in clinical use are still based on Placido’s disc. Data are gathered over a wider area of cornea (8–9 mm) and curvature or power is calculated for thousands of points. Images are captured by one or more video cameras and a frame grabber; they are then digitized and analysed by computer software. Algorithms construct a three-dimensional shape from the two-dimensional image and this shape is then displayed on the monitor, most commonly as color-coded maps, but also as wire-mesh or solid models, depending on the instrument.5

Videokeratoscopes are used to examine and monitor corneal shape (Fig. 1.2). They are particularly useful in showing the site of the cone in keratoconus, and in identifying irregular astigmatism, which is essential to select the most appropriate contact lens design.

Videokeratoscopy monitors shape changes following surgery or contact lens fitting, assists in the identification of corneal warpage, whether as a result of lens decentration or orthokeratology, and may make some corneal pathology more apparent than on clinical examination.