2. SOLUTIONS AND ACCESSORIES
• Many solutions and accessories are used in
fitting, wearing, and maintenance of contact
lenses.
• Understanding of these solutions is required by
practitioner and assistant.
• Problems from mild discomfort to severe ocular
damage can occur if the systems are not properly
used.
• Proper patient education and instruction avoid
adverse effects.
3. General principles of contact lens
solution pharmacology
• Tonicity (osmolality):
• When the cornea bathed in a solution that has a
salt concentration of about 0.9% to 1.0% the
cornea will maintain its normal thickness, such
solution is called isotonic.
• If the salt is less than this, it is called hypotonic. If
the cornea bathed on this, water will flow from
the solution into the cornea, causing corneal
swelling( e.g. when swimming in fresh water(
causing cloudy or hazy vision).
4. • Excessive tearing (crying or tearing caused by
uncomfortable lens)cause some corneal swelling.
• Using distilled( water from which salts and other
materials have been removed) or plain tap water,
the water will flow causing osmotic pressure.
Thus, the lens is tightly adhere to the cornea.
• Hypertonic solution( salt concentration over
1.0%) causes corneal thinning. Thus solution is for
treatment of corneal oedema( caused by ocular
disease).
5. HYDROGEN ION
CONCENTRATION(PH)
• The pH of tears is very close to that of the
blood , which is 7.3 to 7.4.
• Studies have shown considerable variation in
human tears, ranging from 5.2 to 8.35 with
the majority at 7.0 to 7.4 .
• If the pH more than 1to 2 pH units patient
may complain of discomfort.
6. VISCOSITY (THICKENING AGENTS)
• compounds that increase the viscosity are often
added to solutions to maintain it on the eye or
the lens for longer time.
• They act as lubricating and cushioning agent on
placement of a contact lens and also help to
prevention of contamination through handling
prior to placement.
• Methyl cellulose is the most common used to
increase viscosity.
• Others examples hydroxyethyl, hydroxypropyl
cellulose, povidone, and gelatin.
7. PRESERVATIVES
• Any solution that instilled on the eye or used with
contact lenses should be free of living organisms,
including bacteria, viruses amoebae, and fungi,
which might cause an infection.
• Sterile solution is free of living organisms.
• Benzalkonium chloride is used as preservative in
contact lens solutions in concentrations of
0.001% to 0.01%.
• Others chorobutol, thimerosal (sodium ethyl
mercurithiosalicylate).
8. SHELF LIFE
• Many solutions containers have an expiration date.
• The reason for this is that most chemical compounds
tend to break down and change with time.
• The preservative may break down and not be effective
against bacteria.
• Buffering compound may be ineffective, allowing the
pH of the solution to change significantly.
• The breakup products may become irritant to the eye,
causing discomfort, some solutions will turn colour
owing to break down of some of the chemicals,
commonly a yellow or brown.
• Do not used expired solutions.
9. TYPE OF SOLUTIONS
• Hard contact lens solutions.
• Wetting solutions
• Soaking.
• Storage containers
• Cleaning solutions
• Combination solutions
10. Solutions for use with hydrogel contact
lenses
• Unpreserved saline solution.(saline solution is
made up of 0.9% sodium chloride in distilled
water).
• Preserved saline solution
• Chemical (cold) disinfection
• Hydrogen peroxide disinfection.
• Cleaning
• Heat ( thermal disinfection).
• All in one solutions
11. ACCESSORY SOLUTIONS
• Irrigating solutions: are used to wash foreign
bodies and chemicals and moisten fluorescein
strips.
• PH 7.0 to 7.5 supplied in bottles that can be
used to spray a constant stream of solution
onto the eye.
• Stains:
• Fluorescein
• Rose Bengal.
