Science project

Saline Solution vs. More Expensive Brands of Contact Lens Disinfectants

Research Questions

  • What is the correct way to clean contact lenses?
  • Do people still use hard contact lenses every day?
  • How long can you wear contact lenses without having to swap?


Soft contact lenses revolutionized the way people see. The earlier forms of the soft contact lens came in the form of hard plastic or even glass, which was highly uncomfortable compared to what most people wear today. Once these contacts are inside the eye, it feels as if you are not wearing anything.

However, not all luxuries come care-free. In order for contact lenses to be safe in the eye, the wearer needs to disinfect and store them everyday in a contact lens case. Not taking care of your contact lenses by cleaning them in saline solution can cause serious eye infections.

But not all saline solutions are the same. Cheap saline solution costs $2.00 for a 12 oz bottle, while more expensive kinds with different ingredients retail for $9.00 per 10 oz bottle. They both make very similar claims, but why is one so much more expensive than the other? We will evaluate their effectiveness, as well as their effect on the durability of monthly lenses.


  • A few packs of soft silicone hydrogel contact lenses (these are prescription-only in the USA, so you have to ask an optometrist)
  • Saline solution for contacts (you can get a twin-pack at Walgreens for $3.99)
  • Opti-Free lens solution (which apparently contains a patented ingredient that no one else has)
  • Contact-lens storage case (which you can get at the optometrist)
  • Microscope
  • Magnifying glass
  • Water

Terms to Know

  • Silicone hydrogel conact lenses
  • Pioneer contact lenses
  • Leonardo da Vinci and his contact lens ideas
  • Bacteria
  • Disinfection
  • Active ingredients in contact lens solutions

Experimental Procedure

  1. Take the monthly contact lenses out of the pack and discard the packaging.
  2. You do not need to rinse at this point, just wear both of the lenses like you would normally.
  3. At night, rinse one of the lenses with Saline and the other lens with Opti-Free. Remember which one! Put in the contact lens case to store overnight.
  4. In the morning, rinse the SAME lens with Saline and the SAME lens with Opti-Free.
  5. Rinse the contact lens case with water.
  6. Repeat the above steps for one month.

For the experimenter:

  1. Observe that the “new” contact lens should have no harmful bacteria present because it should be sterile.
  2. When your test subject takes off the contact lenses for the day, you are to observe the contact lenses underneath a microscope and look for any bacteria present. Bacteria is distinguishable because it is stringy-looking, among other factors.
  3. You should evaluate if there is a daily growth of bacteria, which lens has a more prolific growth of bacteria, and which lens is in overall better condition.

Suggested Chart


New Lens
Day 1
Day 2
Day 3
Day 4
Lens #1






Lens #2








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