Section

Preliminaries ONE

4.1 Hygienic procedures to avoid cross-infection

Hygienic procedures within the consulting room are extremely important to avoid any risk of cross-infection between patients as well as between patient and practitioner.1 Standard practice should include the following:

Hand washing between patients

•For routine washing, use an antiseptic hand cleaner such as 4% chlorhexidine gluconate (e.g. Hibiscrub).

•After known contact with a source of infection, use an antibacterial hand cleaner such as 5% chlorhexidine in 70% isopropyl alcohol (e.g. Hibisol).

Decontamination and disinfection of trial lenses

All diagnostic lenses, which in effect means only rigid lenses, must be routinely decontaminated and disinfected after use (see Section 4.3).

Disinfection of instrumentation

Surfaces of ophthalmic instruments that come into direct contact with the patient, such as chin rests, forehead supports and trial frames, should be routinely disinfected (e.g. with wipes containing 70% isopropyl alcohol). Worktops should be similarly treated.

©2010 Elsevier Ltd, Inc, BV

DOI: 10.1016/B978-0-7506-7590-1.00011-X

Section ONE Preliminaries

Temporary lens containers

Containers for temporary storage of patients’ lenses during examination (in the absence of their own case) should be clean and sterile. The plastic blisters in which disposable lenses are supplied can be kept by the practitioner for single use with future patients. Glass vials can be autoclaved for repeated use.

4.2 Solutions and drugs

Water

Sterile water may be used for rinsing rigid lenses after cleaning and prior to their insertion with a suitable wetting solution. It should not be used with soft lenses because of the likelihood of hypotonic adhesion to the cornea (see Section 17.7).

Tap water should not be used with soft lenses because of the risk of contamination by microorganisms, particularly Pseudomonas and Acanthamoeba2 (see Section 29.1.1). For the same reason, it should not be used for rinsing lens cases, although the use of boiled water followed by air drying is acceptable.

Saline (0.9% sodium chloride BP)

Normal saline is extensively used in contact lens practice for a variety of applications:

•Ocular irrigation.

•Rinsing lenses prior to insertion.

•Rinsing and storing diagnostic lenses after fitting and prior to cleaning.

•Heat disinfection of soft lenses and subsequent storage.

•Wet cells of instruments for soft lens verification.

•Wetting fluorescein strips.

•Rewetting soft lenses.

PRACTICAL ADVICE

•For soft lenses, use unpreserved saline or those designated ‘for sensitive eyes’.

•For rigid lenses, use either preserved or unpreserved.

Proprietary solutions

A range of proprietary wetting, soaking and cleaning solutions is required for both rigid and soft lenses (see Chapter 26).

Staining agents

Fluorescein sodium BP

Used in 1% or 2% solution or, much more usually, as impregnated paper strips which can be stored indefinitely if kept dry. Cross-infection is avoided by using a different strip for each patient and, in some cases, for each eye.

48

Consulting room procedures and equipment 4 Chapter

Fluorescein is the main method of checking rigid lens fitting. It makes the tear pattern visible either by means of ultraviolet fluorescence with a Burton lamp or with the cobalt filter of the slit lamp. Fluorescein is almost entirely washed out of the eye within an hour but a saline rinse is recommended before soft lens reinsertion to avoid any risk of discoloration. This discoloration is less significant with silicone hydrogels which do not absorb as much fluorescein and is relatively unimportant with daily disposables.

It is an important diagnostic aid because it stains damaged living corneal tissue green and the conjunctiva yellow.3 Contrast with the slit lamp can be enhanced by a combination of filters. A yellow barrier filter such as Kodak Wratten 12 is used for observation in conjunction with either the standard cobalt filter or a Wratten 47A blue placed in front of the light source.

The degree of fluorecence also increases with:

•Thickness of the fluorescein layer.

•Concentration, up to about 0.001% above which it decreases.

•pH, up to about pH 8 beyond which it decreases in alkaline conditions.

•Wavelength of the exciting light with a peak at 495nm.4

Fluorescein is also used to assess dry eyes by evaluating the break-up time and prism height of the tears (see Section 6.3).

High molecular weight fluorescein (e.g. Fluorexon)

The molecular weight is sufficiently great to prevent immediate penetration into most soft lens materials, although care is still required with high water content lenses as there may be some uptake and discoloration. (N.B. Do not subsequently disinfect with hydrogen peroxide since oxidation may well bind molecules of dye to the lens). The degree of fluorescence is less than with standard fluorescein so that a yellow filter is recommended for observation. High molecular weight fluorescein can be used to:

•Assess corneal integrity.

•Evaluate the fitting of soft lenses, or rigid/soft combination lenses (see Section 32.8).

•Assess break-up time (BUT) and tear prism immediately prior to soft lenses fitting.

•Assess BUT and tear prism with soft lenses in situ.

•Locate axis markings of toric soft lenses.

Rose bengal 1%

Devitalized epithelial cells of the cornea and conjunctiva are stained bright red, indicating abnormal ocular conditions or skin disease. Rose bengal also stains mucus. It can cause mild discomfort if instilled directly into the eye and takes several hours to absorb, even if used in very small amounts. A better technique is to use a cotton wool bud or impregnated paper strip.

Lissamine green

Also a diagnostic agent for evaluating corneal and conjunctival abnormalities, equivalent to rose bengal but causing far less discomfort. It is, however, more

49

Section ONE Preliminaries

difficult to use since there is an optimum time – between 1 and 4 minutes – to allow the staining to develop and before it begins to fade. The correct level of illumination is also important.

It is now considered that both rose bengal and lissamine green stain an epithelial surface that has been deprived of mucin protein or which has exposed epithelial cell membranes.4

Alcian blue

Stains mucus blue. Not generally used in contact lens practice as traces remain in the eye for too long; rose bengal and lissamine green can be used for the same purpose.

Topical anaesthetics

Benoxinate 0.4%; amethocaine 0.5% and 1.0%

Used for the removal of foreign bodies but primarily employed with scleral lenses prior to taking eye impressions. Sometimes used with rigid lenses when fitting very sensitive eyes (e.g. keratoconus), where lid spasm prevents lens removal, and for special techniques such as orthokeratology (see Chapter 14). Anaesthetics tend to retard healing of the corneal epithelium and, in cases of trauma and overwear, are used only in the presence of extreme pain.

Antimicrobial agents

Chloramphenicol BP 0.5%

A prescription-only broad-spectrum antibiotic normally used in emergency as a prophylactic, ophthalmic anti-infective. May now be prescribed by UK optometrists and is available in some formulations as an over-the-counter medication. Non-preserved minims are still a prescription only medication.

Fucithalmic 1%

The main component is fusidic acid. Fucithalmic is used in treating bacterial infections, mostly Gram-positive. It is indicated in bacterial conjunctivitis, blepharitis, styes but mainly staphylococcal colonization in anterior lid margin disease.

Brolene (0.1% propamidine isetionate)

Antibiotic with some efficacy against Acanthamoeba.5 Available over the counter.

Other drugs

Sodium cromoglycate 2% (e.g. Opticrom, Broleze, Vividrin)

An anti-allergic mast cell stabilizer, antihistaminic, over-the-counter preparation to reduce inflammation and mucus secretion. Used generally for a period of

50