Healthcare and Medicine Reference
In-Depth Information
INTRODUCTION
Care solutions are essential for contact lens (CL) safety and durability. They
were fi rst intended for cleaning and disinfecting non-planned replacement
lenses, commonly using products with poor compatibility with the ocular
surface, such as hydrogen peroxide, chlorhexidine or benzalconium
chloride. In spite of their effi cacy against microorganisms, they were
somewhat inconvenient, at least in their earlier formulations particularly
when used with hydrophilic lenses that absorb such components into their
matrix.
Care systems were initially complex requiring that the wearer must use
different products; nowadays the care systems have evolved into complex
formulations that meet all the requirements for a care system in a single
package in order to make their use easier and more convenient to the CL
wearer and to promote compliance. However, this combination of properties
into the same package requires an optimal balance between the disinfecting
and cleaning activity and the respect for the ocular surface homeostasis.
Today, development of effective care systems is a challenging task once
they have to be effective for cleaning and disinfection, and at the same time
respect the physiology of the ocular surface, be convenient for the wearer
and when possible improve the comfort of the CL during the whole day.
These are the requirements for current MPDS that represent over 80% of
the all care systems prescribed (Morgan et al. 2010). With the advent of
disposable CL cleaning capability has become less important and industry
makes efforts to provide MPDS with new features that address one of the
main unsolved issues for contact lens wearers: all day comfortable wear.
As a result, current MPDS are the result of complex chemical and biological
engineering that must have a critical combination of properties such as
pH, osmolality, viscosity maintaining high standards of disinfection and
cleaning effi cacy.
REQUIREMENTS AND COMPOSITION OF CURRENT
CARE SOLUTIONS
The basic requirements for a CL care system are to clean tear and
environmental products deposited on the surface of the lens, to remove the
materials that had been strongly adhered to the CL material, to disinfect
the lens by reducing the populations of microorganisms to safety levels,
to warrant that the CL material remains fully hydrated, and desirably, to
improve the CL wetting properties to extend wearing comfort during the
whole day.
Table 1 shows some examples of soft CL MPDS marketed and their
composition. Composition of MPDS is critical because of the potential
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