Consulting room procedures and equipment 4 Chapter

28 days in the treatment of contact lens-induced papillary conjunctivitis (CLIPC) to stop irritation, mucus production and growth of papillae. Generally effective in reducing symptoms but not always the size of papillae. Technically a hay fever remedy and not strictly available for optometric treatment. Gives better results in reducing papillae with atopic patients.

Lodoxamide (e.g. Alomide)

A mast cell stabilizer used to relieve the symptoms of ocular allergies such as hay fever.

Adrenalin 1%

A conjunctival decongestant, often used after taking eye impressions.6

Sodium bicarbonate 2%

Use to fill sealed scleral lenses on insertion; for ocular irrigation; and for lid hygiene with cotton buds.

4.3 Decontamination and disinfection of trial lenses

General advice used to be simply that all trial lenses, both rigid and soft, must be thoroughly cleaned before use and properly disinfected after being worn. In 1999, the Spongiform Encephalopathy Advisory Committee (SEAC) advised the UK Department of Health (DoH) of a remote theoretical risk that abnormal prion proteins could be transmitted from one patient to another by means of a contact lens. Since this time, the DoH and professional bodies have effectively banned the re-use of trial lenses except in special complex cases.7

The following definitions are currently used to distinguish between trial lenses and special complex diagnostic lenses:

A trial contact lens is used to assess fitting, following which it is either disposed of or dispensed to the patient. Such lenses may not be re-used with another patient.

A special complex diagnostic contact lens is used to assess the performance of the design on the eye. Although it may be of any type, it is nearly always rigid. The re-use of such lenses is permitted only under the following stringent conditions:

•The lenses should be used solely within the practitioner’s premises and under the control of the practitioner at all times.

•The practitioner should ensure that decontamination is carried out to the highest possible standards.

•The practitioner should keep full records to show the usage of each lens.

•The practitioner should inform the patient of all of the relevant risks and benefits associated with contact lens fitting.

In effect, this means that soft trial lenses are now almost never used, their place being taken by disposable lenses. With rigid lenses, several laboratories

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have introduced simplified designs for so-called ‘empirical fitting’ where the lens is supplied on the basis of ‘K’ readings and refraction. This has never really been a satisfactory substitute, however, for assessing a diagnostic lens on the eye and the fitting of complex cases such as keratoconus, grafts, irregular astigmatism, corneal distortion and post-refractive surgery is not feasible without the use of diagnostic lenses. Rigid lenses are therefore still used to a limited extent. The following represent current guidelines for the safe decontamination and disinfection of diagnostic lenses:

Decontamination and disinfection of rigid gas-permeable and PMMA lenses

•After removal from the eye, a rigid lens must not be allowed to dry prior to decontamination.

•It should be rinsed in Water for Irrigation BP for more than 30 seconds.

•It is cleaned with liquid soap or detergent and then rinsed again with Water for Irrigation BP for a further 30 seconds.

•The lens is then soaked in sodium hypochlorite 2% solution for 10 minutes.

•It is then removed from the solution.

•The lens must be rinsed in three changes of Water for Irrigation BP for not less than 10 minutes.

•The lens is shaken to remove excess liquid and dried with a tissue.

•It is then disinfected in the normal way by storing in a proprietary soaking solution since sodium hypochlorite is ineffective against spores and cysts of some microorganisms.

PRACTICAL ADVICE ON LENS DECONTAMINATION

•Set aside a ‘quarantine’ area for lenses to be decontaminated.

•2% Sodium hypochlorite solution should be stored safely with restricted access.

•2% Sodium hypochlorite can be obtained as the proprietary solution Menilab, from Menicon which also supplies a solution for patient cleaning and disinfection of rigid lenses. This consists of a mixture of Progent A (0.4% sodium hypochlorite) and Progent B (potassium bromide).

•Sodium hypochlorite is also available as Milton from pharmacies.

•It is recommended that the use of a diagnostic rigid lens is recorded.

GENERAL ADVICE

•It is no longer permitted in cases of loss or damage to lend old or obsolete trial lenses to patients while replacements are obtained.

•Avoid very viscous solutions for storage. A lens left for any length of time can be extremely difficult to remove from the vial.

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Soft lenses

Following the above advice, it is essential that straightforward soft lenses are either dispensed to the patient or disposed of. Where a special complex diagnostic lens is used, it must be decontaminated first and then disinfected before use with another patient.

Various disinfection methods are possible:

•Heat. Autoclaving in 0.9% saline in sealed vials is the safest method but high temperature can adversely affect the lifespan of some high water content lenses.

•Preserved solutions are the most convenient method but may be unreliable against Acanthamoeba, fungi and yeasts. A minimum of 4–6 hours is required before lenses can be reused and some patients are sensitive to the preservatives.

•Hydrogen peroxide is effective against most microorganisms but the various systems are inconvenient for routine trial lens storage.

Historically, other methods such as chlorine tablets and microwave radiation have been used but these are no longer feasible.6,8

WARNING

2% Sodium hypochlorite is extremely toxic and even concentrations much lower than this can cause severe damage to ocular tissues. Extremely thorough rinsing is absolutely essential after decontamination to ensure that no traces remain on the lens and, for this reason, it must not be used with soft lenses.

In case of accident

•The eye should immediately be irrigated with normal saline.

•Check the ocular surface with fluorescein for signs of epithelial damage.

•Arrange to re-examine the patient after 24 hours even if only minor signs are seen.

•Refer for medical examination if any serious signs are observed.

•Record details in the practice accident book.

4.4 Other procedures

4.4.1 Professional cleaning and rejuvenation

Rigid lenses

A modification unit can be used to repolish rigid lenses, recondition the lens surface and make other adjustments (see Section 30.3). Technically, however,

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these procedures can no longer be carried out by practitioners since they are now required to be CE accredited. Lenses can nevertheless be cleaned chemically using sodium hypochlorite and there is also a Boston professional cleaner for laboratory or practitioner use.

Soft lenses

Professional cleaning is now seldom required since the advent of disposable lenses and frequent replacement schemes. Magnetic stirrers incorporating a hotplate efficiently clean most soft lenses using oxidizing chemicals such as sodium perborate. Ultrasonic devices are claimed to have a cleaning and  disinfecting action with both soft and rigid lenses but have not achieved  routine use. The same applies to methods employing ultraviolet irradiation.

4.4.2 Lens verification

The instruments for rigid and soft lens verification are covered respectively in Sections 13.3 and 20.3.

4.4.3 Ancillary items

The following ancillary items are sometimes useful during fitting and aftercare:

•Soft-ended tweezers, a lens lift or a glass rod for removing soft lenses from their vials.

•A glass rod or muscle hook for removing a dislodged lens from the upper fornix.

•Suction holders for use with rigid lenses.

•Clean lens mailers or disposable lens blisters for temporary storage when lenses are removed from the eye during examination.

•Glass vials or lens cases for storage when lenses are retained for professional cleaning.

•A crimping device for resealing pharmaceutical lens vials.

•Small self-adhesive labels for identifying lenses temporarily stored in unmarked bottles.

•Miscellaneous items including facial rule, grease pencil, pupil gauge and pen torch.

4.5 Insertion and removal by the practitioner

PRACTICAL ADVICE

•Ensure that the patient is as relaxed as possible.

•Avoid the patient actually seeing the lens approach.

•Ensure that both eyes remain open because of Bell’s phenomenon.

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•The head and neck should lean firmly against a carefully positioned headrest.

•Stand to the side of the patient.

•Establish whether the lids are tight or loose, as this may influence the choice of method.

•With rigid lenses, have a suction holder readily available for speedy removal in case of a poor reaction.

•For the same reason, have available local anaesthetic for emergency use.

4.5.1 Rigid gas-permeable and PMMA lenses

Insertion

•The patient looks with both eyes either at a fixation target just below the horizontal or down at a point on the floor.

•The upper lid is retracted.

•The lens is placed onto the cornea from above using either the forefinger or a suction holder.

With very tight-lidded patients or where fixation cannot be controlled:

•The patient looks to the extreme nasal position.

•The lens is placed onto the temporal sclera and slid gently across to the cornea.

Once the lens is in position, the patient is advised to avoid looking up and to half-close the eyes, looking down to minimize lid sensation.

Removal

•The head is leaned firmly back into the headrest.

•The patient fixates straight ahead.

•The lens is ejected with pressure applied either at the top and bottom lid margins or at the outer canthus.

•Alternatively, the lens is removed from the cornea with a moistened suction holder.

4.5.2 Soft lenses

Insertion

Soft lenses may be inserted either onto the temporal sclera and slid across or in the same way as rigid lenses and placed directly onto the cornea.

Once the lens is correctly centred, the patient should notice only slight lid sensation. Any significant discomfort is probably due to a foreign body, either carried in with the lens or already present in the tear film and subsequently trapped. The lens should be removed, rinsed and reinserted. Mild discomfort,

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