Eye Care and Contact Lens Management of Contact Lenses

Introduction to Contact Lenses

Reasons for choosing contact lenses over eyeglasses:
- Eyeglasses fail to provide satisfactory vision in certain cases.
- Cosmetic preferences.
- Eyeglasses can be a hindrance during sports or vigorous activities.
Benefits of contact lenses:
- No obstruction of vision from eyeglass frames.
- Greater clarity in peripheral vision.
- No fogging of lenses caused by sudden temperature changes (e.g., moving from a cold to a warm environment).
- Increased freedom of motion during vigorous activity.
- Seeing objects in their true sizes (minimizing magnification or minification effects of glasses).
- Perceived improvement in personal appearance.

Contraindications and Precautions for Contact Lens Usage

Occupational Hazards:
- Exposure to wind and glare.
- Presence of molten metals or irritants.
- Environments with dust and particulate matter.
- Exposure to tobacco smoke.
- Contact with chemicals or chemical fumes.
Medical Conditions and Physiology:
- Chronic conjunctivitis.
- Blepharitis.
- Recurrent viral, bacterial, or fungal infections.
- Poor blink rate or incomplete blinking.
- Insufficient tear production (Dry Eye Syndrome).
- Diabetes: Generally advised against extended-wear types.
- Chronic common cold or allergic conditions.
- Pregnancy.
- Use of oral contraceptives.

Classification and Characteristics of Contact Lenses

Broad categories based on chemical make-up and physical properties:
- Hard Lenses: No longer in common use.
- Rigid Gas-Permeable (RGP) Lenses.
- Soft Lenses.

Comparison of RGP and Soft Lenses

Rigidity:
- RGP Lenses: ${+++}$
- Soft Lenses: ${0}$
Durability:
- RGP Lenses: ${++}$
- Soft Lenses: ${0}$
Oxygen transmission:
- RGP Lenses: ${+++}$
- Soft Lenses: ${+}$ to ${++}$ (up to ${+++}$ for specific materials).
Chemical Adsorption:
- RGP Lenses: ${0}$
- Soft Lenses: ${+++}$
Optical Quality/Visual Acuity:
- RGP Lenses: ${+++}$
- Soft Lenses: ${++}$
Correction of Astigmatism:
- RGP Lenses: Yes.
- Soft Lenses: Requires Toric lenses.
Spectacle Blur:
- RGP Lenses: ${++}$
- Soft Lenses: ${0}$
Convenience:
- RGP Lenses: ${++}$
- Soft Lenses: ${+++}$
Comfort:
- RGP Lenses: ${+}$
- Soft Lenses: ${+++}$
Adaptation Period:
- RGP Lenses: Days.
- Soft Lenses: Hours.
Extended Wear:
- RGP Lenses: Yes.
- Soft Lenses: Yes.

Rigid Gas-Permeable (RGP) Lenses

Physical properties:
- Relatively inflexible and smaller in size compared to soft lenses.
- Do not absorb water (< 10\% ).
- Retain their shape when removed from the eyes.
- Available in Toric designs for astigmatism correction.
Material and Oxygen importance:
- Made of flexible polymers with silicone incorporated to allow oxygen permeability.
- Lack of oxygen (Hypoxia) can cause red eyes, blurred vision, eye discomfort, and increased risk of eye infections.

Soft Contact Lenses

Physical properties:
- Moderately to highly flexible.
- Absorb a high percentage of water (> 10\% ).
- Conform to the shape of the supporting eye structure (cornea/iris).
- Larger in size: They cover the whole iris and part of the cornea.
Types of Soft Lenses:
- Disposable soft lenses: Daily, Weekly, Monthly replacements.
- Extended wear.
- Toric lenses (for astigmatism).
- Conventional soft lenses: Replaced every $6 \, \text{months}$ or longer.
Materials:
- Hydrogel: Lower oxygen permeability.
- Silicone hydrogel (e.g., Acuvue Oasys): Higher oxygen permeability; some are comparable to RGP lenses.
- Both are made of plastics that are hard when dry but absorb water to become soft and gel-like when hydrated.
Advantages:
- Easier to remove.
- More comfortable than rigid lenses.
- Photophobia is unlikely.
- Spectacle blur is unlikely.
- Less likely to trap dust, eyelashes, or foreign particles.
- Less likely to be dislodged.
Disadvantages:
- Visual acuity may not be excellent for all wearers.
- Hydration levels can change.
- Material tears easily.
- Lower oxygen permeability in older hydrogel models.
- May cause dry eyes.
- Can adsorb chemical compounds from topical ophthalmic products.
- Shorter life span ( $12 \text{ to } 18 \, \text{months}$ ) than RGP lenses ( $18 \text{ to } 36 \, \text{months}$ ).

Importance of Lens Cleaning

Tear components (proteins and oils) are hydrophobic and tend to adhere to the lens surface.
Residue hardens to form coatings and tenacious deposits, creating an irregular surface.
Risks of neglected cleaning:
- Acts as a growth medium for bacteria.
- Irritates eyelids and corneal epithelium.
- Potential for infection.
- Decreased visual acuity.
- Decreased lens wear time.

Lens Care Solutions

Cleaning Solutions:
- Contain non-ionic or amphoteric surfactants to emulsify oils and solubilize debris.
- Weakly alkaline to dissolve proteins and lipids.
- Note: High pH may cause lens decomposition.
- Usually contain preservatives.
Hydration Importance:
- Rigid lenses absorb $1 \text{ to } 3\%$ moisture by weight.
- Lenses dehydrate in air and rehydrate in lacrimal fluid or soaking solution.
- Inserting a dehydrated lens causes discomfort.
- Dry lenses allow accumulated deposits to harden, making them harder to remove.
Soaking Solutions:
- Used for storage when lenses are not in use.
- Maintains constant hydration.
- Aids in removing accumulated deposits.
- Contains preservatives to maintain sterility.

Self-Care of Soft Contact Lenses

General Protocol:
1. Remove lens from eye.
2. Clean lens.
3. Rinse lens.
4. Disinfect lens (Chemical or Peroxide methods).
5. Rinse lens.
6. Insert lens.
7. Rewet lens as needed.
8. Weekly: Clean with enzymatic cleaner.
Surface-Active Cleaners:
- Components: Non-ionic detergent, wetting agent, chelating agents, buffers, and preservatives.
- Effective for lipids; less effective for proteins.
Multipurpose Solutions (MPS):
- All-in-one system for cleaning, rinsing, disinfecting, and storing.
- Includes surfactants, disinfectants (e.g., Biguanide, Polyquad), and lubricants.
- Manual rubbing (approx. $20 \, \text{seconds}$ ) in the palm of the hand is recommended even for "no-rub" products.
Enzymatic Cleaners:
- Used weekly to hydrolyze polypeptide bonds of proteins.
Rinsing Solutions (Saline):
- Can be MPS or Saline.
- Purpose: Remove loosened contaminants and residual cleaners; rehydrate lenses.
- Saline is NEVER to be used for disinfection.
- Example: Bausch & Lomb Sensitive Eyes Plus Saline Solution (contains Boric Acid, Sodium Borate, Potassium Chloride, Sodium Chloride, preserved with Polyaminopropyl Biguanide $0.00003\%$ and Edetate Disodium $0.025\%$ ).
Disinfection Methods:
- Thermal: Heat-based.
- Chemical: Stored for $4 \text{ to } 6 \, \text{hours}$ in antimicrobial solutions.
- Hydrogen Peroxide Disinfection:
  - Strong antioxidant; kills bacteria, yeasts, fungi, spores, and viruses by damaging cell membranes and creating free radicals.
  - Requires a special case with a neutralization mechanism (Catalase tablet or Catalytic disc) to convert peroxide to oxygen and water.
  - Preservative-free after neutralization (ideal for sensitive users).
  - If lenses soak in neutralized solution for more than one day, the process must be repeated before wear.
  - Warning: Direct contact with non-neutralized peroxide causes extreme pain, stinging, and potential corneal damage. If it occurs, flush with sterile saline immediately and consult a doctor.

Self-Care of RGP Contact Lenses

Protocol:
1. Remove lens from eye.
2. Clean lens (Rub in palm for $20 \text{ to } 30 \, \text{seconds}$ with index finger).
3. Rinse lens.
4. Disinfection/Conditioning.
5. Insert lens.
6. Rewet as needed.
7. Weekly: Enzymatic clean.
Special Solutions:
- Cleaning Solutions: May contain silica gel to mechanically break adhesive bonds of deposits. Discard $90 \, \text{days}$ after opening.
- Enzymatic Cleaner: Use weekly (2 drops in each lens well); soak for at least $4 \, \text{hours}$ or overnight.
- Conditioning Solutions: A formulated wetting solution that enhances wettability, creates a cushioning tear layer, increases comfort, disinfects, and stabilizes the lens on the fingertip for insertion. Soak at least $4 \, \text{hours}$ . Discard $90 \, \text{days}$ after opening.

Rewetting and General Storage

Rewetting Solutions:
- Used while lenses are in the eyes.
- Counteract dehydration from wind or high temperatures.
- Contain low-concentration surfactants for cleaning and polymers for lubrication.
Storage Case Care:
- Clean thoroughly and air-dry between uses.
- Scrub the case weekly.
- Replace the case at least every $3 \, \text{months}$ .

Counseling Tips

Do not wash or rinse lenses with water or saliva (risk of Acanthamoeba or bacterial infection).
Avoid swimming with contact lenses.
Remove lenses immediately if eyes hurt.
Always wash hands before handling lenses.
Do not sleep with contact lenses (unless specifically designed for extended wear and approved).

Questions & Discussion

Question 1: Which of the following statements is FALSE?
- RGP lens allow more oxygen transmission as compared to hydrogel soft lens.
- RGP lens absorb around $30\%$ of water.
- Soft contact lens wearers are unlikely to experience spectacle blur.
- Soft contact lens are more comfortable than rigid lenses.
- Answer: The second statement is false; RGP lenses absorb < 10\% water (typically $1-3\%$ ).
Question 2: Which of the following statements about lens care is TRUE?
- Cleaning solutions should be discarded $30 \, \text{days}$ after opening.
- Conditioning solutions mechanically break adhesive bonds formed between lens and deposits.
- Enzymatic cleaners are used daily to remove protein deposits on lens.
- Cleaning solutions contain surfactants.
- Answer: The fourth statement is true; cleaning solutions contain surfactants. (Cleaning solutions with silica gel, not conditioning solutions, break adhesive bonds).
Question 3: Which of the following statements about lens care is FALSE?
- Saline can be used as a disinfecting, rinsing and storage solution.
- The rinsing step helps to rehydrate the lens.
- Peroxide disinfection is suitable for people who are sensitive to preservatives.
- Polyquad is a preservative found in disinfecting solutions.
- Answer: The first statement is false; Saline is NEVER to be used for disinfection.