Aftercare complications 29 Chapter

29.1.7 Contaminated lenses

This problem mainly applies to soft lenses contaminated by products like paint, varnish, hairspray and make-up, either by direct contact or indirectly via the hands. Rigid lenses are occasionally affected.

29.2 Grief cases (drop-outs)

However carefully lenses are fitted, not all patients adapt well.

29.2.1 Causes

•Unreasonable patient expectations.

•Limitations in available lens designs.

•Poor vision or comfort because of fitting or refitting with an inappropriate type of lens.

•Wearing the correct type of lens but an unsatisfactory fitting.

•Poor vision or comfort because of badly manufactured lenses.

•Using inappropriate solutions.

•Recurrent deposits or greasy lenses.

•Persistent red eyes or 3 and 9 o’clock staining because of poor blinking.

•Dry eyes.

•Spectacle blur.

•Allergic response to materials or solutions.

•The patient does not understand or follow instructions.

•The presence of an eye infection, either connected or unconnected with the contact lenses.

•The patient may no longer be suitable for contact lens wear because of corneal exhaustion, dry eyes or environmental factors.

•The patient has never really been suitable for contact lenses.

•The patient may have lost confidence in a previous practitioner, although the lenses are perfectly satisfactory.

29.2.2 Courses of action

If a second opinion is sought from a new practitioner, the main reason must be identified for previous dissatisfaction and whether successful contact lens wear is feasible. The following are the most common courses of action:

•Modify existing lenses. This applies mainly to rigid gas-permeable   lenses.

•Refit lenses of the same general type (e.g. soft with soft or rigid gaspermeable with rigid gas-permeable), but use a different material, Dk or design.

•Refit with lenses of an altogether different type (e.g. soft with rigid gas-permeable or silicone hydrogel with hydrogel).

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•Change the solutions or disinfection system. This is often advisable, even where refitting is also carried out.

•Give advice on correct blinking.

•Give clear instructions in the correct use of solutions, even where there is no sensitivity problem.

•Give instructions in correct lens handling and maintenance.

•Refer for medical opinion.

•Advise patients that they are now unsuitable for lenses. They will be disappointed but, at the same time, should accept the fact that they have at last been given unequivocal advice.

PRACTICAL ADVICE

•Grief cases have generally been disillusioned with contact lenses and are seeking a swift and positive resolution to their problems.

•Where refitting is necessary, dispense lenses from stock where possible.

•Give a safe but rapid wearing schedule.

•Put a time limit of 2–3 weeks on any course of action to prevent an unsuccessful case dragging on interminably.

•Where only partial success is possible, advise patients to be realistic (e.g. accept a restricted wearing time or limited bifocal near vision), or discontinue.

•Hold out the hope of possible future improvement since new lenses and materials are continually being introduced.

29.2.3 Avoiding grief cases

•Do not refit lenses just for the sake of it. If a patient is entirely happy with existing lenses and examination reveals no serious, asymptomatic problems (e.g. corneal oedema or vascularization), then leave well alone. This often applies to old-fashioned low Dk lenses, either rigid or soft.

•Explain, nevertheless, any relevant new developments and clarify misconceptions (e.g. disposables may not be feasible for some complex lens forms).

•If a patient has been refitted with theoretically better lenses (e.g. hydrogels with silicone hydrogels) and they do not settle rapidly, then return to the previous type without delay.

•If a replacement lens does not settle rapidly with an experienced lens wearer, change it or refit.

•Use only the best possible quality lenses. Poorly made examples can waste more in practitioner time than the cost of the lenses.

•Adopt a flexible and open-minded approach to contact lens fitting and be prepared to change from one type to another if problems arise.

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29.3 Side effects of systemic drugs

Many systemic drugs have side effects which give rise to symptoms of discomfort, blurred vision, dryness and lens discoloration (Table 29.1).

PRACTICAL ADVICE

•Pathologies of the cornea due to side effects are serious and tend to be progressive as the dosage continues.

29.4 Lens ageing

29.4.1 Soft lenses

Soft lenses stored in sealed vials or blister packs have long expiry dates and remain in good condition for several years. Once they are worn regularly, however, lens deterioration occurs in a variety of ways. Unlike rigid lenses, ageing is a common cause of conventional lens replacement and is influenced by a variety of factors:

•Lens material. High water content ionic lenses deteriorate more rapidly than low water content and non-ionic because of deposits and discoloration (see Section 7.3).

•Wearing schedule. Extended wear lenses are more badly affected by deposits than those used daily.

•Tear chemistry. Some patients’ lenses last only a few weeks, whereas others can remain in acceptable condition for several years. Dry eyes cause particular problems.

•Method of disinfection. Lenses had a shorter life span when sterilized by heat compared with solutions. Hydrogen peroxide is particularly good at keeping lenses in optimum condition (see Section 26.3.1).

•Regularity and method of cleaning.

•Patient care.

•The environment in which lenses are worn. Dry atmospheres exacerbate lens deposits.

•Prolonged use of VDUs also increases lens deposits.

Protein film

All lenses suffer protein deposits to some extent. With HEMA in particular, there is a chemical bonding between tear protein and the polymer’s hydroxyl groups. Heat disinfection exacerbates the problem by denaturing any surface protein that has not been removed by proper cleaning. It is observed as a blue-grey film by oblique illumination against a dark background (dark-field illumination). It can also be seen during slit lamp examination if the patient stares and the lens surface is allowed to dry.

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Table 29.1  Systemic drugs and their side effects

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Discoloration

Most high water content lenses suffer from brown discoloration to some extent. HEMA can also be affected and heat aggravates the problem. Adrenaline compounds in the tears, nicotine and make-up have been suggested as other causes. Some lenses fluoresce with ultraviolet light. This effect may be due either to the material (with new lenses) or chlorhexidine bound to surface deposits. Acuity may be reduced and significant reductions in light transmission occur.9 Hormonal problems and systemic drugs have also been implicated (see Section 29.3).

White spots

White spots almost invariably occur on the front surface of the lens. In the early stages they appear as fine punctate dots and gradually develop into discrete, elevated deposits scattered irregularly within the area of the exposed palpebral aperture. High water content lenses and those for extended wear are much more affected, particularly with dry-eyed patients and poor blinkers. In severe cases, white spots can be over 1 mm across and extremely uncomfortable. These larger deposits have also been referred to as mulberries and jelly-bumps. The composition of white spots has been variously described as a combination of mucoprotein and lipids, mucopolysaccharides, and calcium phosphate and calcium carbonate.10

Rust spots

Rust spots are mainly due to atmospheric pollution and are more often observed in patients from industrial areas or who travel by train. They are a form of benign ferrous contamination affecting all types of soft lens and are occasionally found as a manufacturing fault.

Surface and edge deterioration

As lenses become older and less flexible, they become uncomfortable because of surface scratches and edge chips. Engravings can either crack or become encrusted with deposits. Uneven drying of protein film at the lens periphery can cause crenellated edges.

Fitting changes

Lenses with deposits are more influenced by the upper lid and significant changes in fitting characteristics can occur. Usually they become looser and corneal diameter lenses may become badly decentred. High-riding lenses are frequently associated with CLIPC where the irregular tarsal plate pulls the deposited lens out of position.

Refractive changes

Old and less flexible lenses frequently give reduced acuity as well as spurious changes in over-refraction of as much as 1.00 D. The lens power, therefore, should always be rechecked with a new lens when refitting is necessary.

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PRACTICAL ADVICE

•Most ageing problems are avoided with disposable or frequent replacement lenses.

•Patients should be encouraged to replace lenses on a regular basis rather than expect an unrealistically long lifespan.

•It is now rarely worth attempting intensive cleaning of soft lenses and the previously available systems have been discontinued.

•It is sometimes beneficial to leave lenses in hydrogen peroxide for up to a week, changing the solution every 2 or 3 days.

•White spots are unlikely to respond to any form of intensive cleaning.

•Lenses with cracks and chips harbour microorganisms and should always be replaced.

29.4.2 Rigid gas-permeable lenses

Rigid gas-permeable lenses do not age in the same way as soft lenses but, depending upon the material, they also deteriorate in various ways. Their lifespan is approximately 2–4 years although some practitioners encourage annual replacement. Lenses for orthokeratology are often replaced at 6-monthly intervals.

Deposits

Silicon acrylate materials (see Section 7.1.2) attract protein from the tears and most patients benefit from the use of enzyme tablets. Monthly soaking is usually sufficient, although some patients require more frequent treatment.

Fluorosilicon acrylates present less of a problem with protein and many of the materials do not require enzyme tablets.

CAB lenses do not contain silicon. Protein deposits are rarely a problem and enzyme tablets are almost always unnecessary. Lenses do attract lipids, however, so greasing is sometimes a problem.

Most rigid lenses benefit from an intensive cleaner such as Progent (Menicon) which contains sodium hypochlorite.

Discoloration

Discoloration is rarely a problem with most materials. However, some (even when new) show haziness and lack of optical transparency.

Surface and edge deterioration

Certain of the higher Dk rigid gas-permeable lenses prove quite brittle so that edge damage or complete breakage can occur. Apart from scratches due to normal wear and tear in use, some lenses can show surface crazing.

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