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Reusable contact lenses needing care products are worn by about half of UK contact lens wearers. Despite the efforts of R&D departments to develop products that are efficient antimicrobials and cleaning agents, while being non-toxic and non-allergenic, solution-induced ocular irritation persists in some contact lens wearers. Solution-induced corneal staining (SICS) is one manifestation of incompatibility between care system, lens material and contact lens wearer. Care system incompatibility can give rise to reduced satisfaction with contact lens wear increasing the likelihood of discontinuation. There is some evidence linking SICS to increase risk of corneal infiltrates.
How do I see it?
Careful examination of the conjunctiva, cornea, limbal areas and palpebral conjunctiva on the slit lamp with fluorescein and blue light, 10-16X magnification and a yellow filter in the observation system.
Symptoms
- May be asymptomatic even with extensive staining
- Stinging on insertion - often considered normal by wearers, so ask!
- Lens comfort scores lower in stainers than non-stainers, irrespective of wearing time
- Dryness/reduced comfort at end of wearing time
- Reduced wearing times
- Lenses greasing/smeary vision
- Itching
- Mucous discharge
- New lenses significantly better - symptoms may disappear for a few days when lenses changed.
Signs
- Instability of the tear film over the cornea
- Salt and pepper' stain - areas of 'negative' staining mixed with fine or micro-punctate stain in the peripheral cornea spreading to the mid periphery (rarely centrally) - a doughnut shape
- Palpebral conjunctiva - punctate stain (a yellow filter is essential to visualise this) with associated low grade hyperaemia
- Extensive punctate staining over all the cornea and the conjunctiva if there is a full-blown toxic reaction
- Limbal and/or conjunctival hyperaemia
- Conjunctival reaction limited to area under lens
- Silicone hydrogel SICS most obvious in first four hours of wear
- Hydrogel SICS persists later in day.
Causes
- Incompatibility between lens material, solution ingredients and wearer's ocular surface
- Contradictory evidence about most compatible lens-solution combinations
- Some combinations worse in the short term - others worse in long term
- Many lens and solutions - no data are yet available for some combinations
- Silicone hydrogel SICS appears earlier in the day then fades, suggests that solution is adsorbing on the lens surface (or to deposits on lens) then is washed off by tears
- Hydrogel lenses - the staining seems to progress through the wearing day as the irritant chemicals slowly leached out of the lens matrix
- Poor corneal wetting may be an early suggestion of incompatibility
- Poor compliance with rub and rinse may lead to mucous and lipid deposits which concentrate solution chemicals leading to staining
- Case hygiene - not cleaning old solution out of case leads to a concentrated residue in the bottom of cases when air dried. Adding fresh solution the next day leads to an irritating mixture
- Topping up overnight solution has been shown to alter the composition of the care product.
Management
- SICS tends to be transient, so unless particularly severe, no need to discontinue lens wear
- Start fresh pair of lenses or refit with single use lenses
- New solution system - change antimicrobial
- Consider early review to ensure resolved and not recurring with new care system, and to reassure wearer
- Controversy about significance of SICS. Some suggest because it is transient and asymptomatic then it does not need managing, but there is evidence of improved comfort and wearing times when care system is changed and SICS resolved. Practitioners report if no action taken then SICS and symptoms worsen over time
- Careful selection of lens material and care system refer to www.thestaininggrid.com and www.siliconehydrogels.org/editorials/jul_08.asp and www.truthaboutstaininggrid.com
- Pay attention to compliance, stress rub and rinse, case hygiene
- Case hygiene - rinse in mornings then wipe with clean tissue and air dry upside down, rinse with fresh solution prior to next use
- Hydrogen peroxide shows low level of SICS (unless inserted un-neutralised!)
- Single-use lenses obviate need for care solutions (daily disposable or continuous wear).
Prognosis
- Excellent. SICS is superficial and resolves rapidly on removal of the cause. There is sufficient choice of care systems and single-use lenses available to ensure a wear regimen that does not induce SICS can be found. Wearers must, however, be counselled that should they revert back to the old solution (or a brand with the same ingredients) then problems will recur. Confusion can arise with own-label solutions, especially if a company changes the formulation.
Differential diagnosis
The pattern, distribution and transient nature of SICS is very characteristic. Lens contamination with an irritant chemical (soap, shampoo, astringent lotion, perfume, CL cleaner) may cause a similar punctate stain but this tends to be more generalised over the cornea and more symptomatic.
? Optometrist Andrew Elder Smith runs Contact Solutions Consultants which offers in-practice training to team members from optometrists to front of house. Training is tailored, and covers clinical and non-clinical aspects of patient and customer care