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Contact Lens Primer
Monica Chaudhry
1:
Contact Lens Milestone
2:
Contact Lens Terminology
3:
Contact Lens Design
4:
Cornea, Oxygen and Contact Lens
5:
Slit-lamp Biomicroscopy and Contact Lens
SLIT-LAMP ILLUMINATION TECHNIQUES
Diffuse Illumination
To Set Up (Fig. 5.2)
Used to Observe (Fig. 5.3)
Direct Illumination
Optic Section
To Set Up (Fig. 5.4)
Used to Observe (Fig. 5.5)
Parallelepiped
Broad Beam Illumination
Conical Beam Illumination
To Set Up
Specular Reflection
To Set Up (Fig. 5.10)
Used to Observe
Indirect Illumination
Retroillumination
To Set Up
Used to Observe (Figs 5.13 and 5.14)
Sclerotic Scatter
To Set Up (Fig. 5.15)
Used to Observe (Fig. 5.16)
Filtered Illumination (Fig. 5.17)
Abnormalities
6:
Keratometry and Corneal Topography
LET US REVISE
Corneal Diameter
Eccentricity Value of the Human Cornea
Instruments Used to Study the Corneal Topography
Ophthalmometer
Types of Keratometers
Principle
Overview of Steps in Taking Measurements— (Baush and Lomb Keratometer)
CORNEAL TOPOGRAPHY
Computerized Video Keratography (VKG)
Uses of VKG
Interpretation of Corneal Topography
Contact Lens Fitting Assisted with Topographer
7:
Contact Lens Materials
OXYGEN PERMEABLE RGP MATERIALS
Cellulose Acetate Butyrate
Siloxane Methacrylate
Fluoro-Siloxane-methacrylates
Alkyl Styrene Copolymers—Butyl Styrene
FLEXIBLE FLUOROPOLYMER LENS—PERFLUOROETHERS
ELASTOMERIC LENSES
Silicone Rubber
Acrylic Rubber
SOFT CONTACT LENSES—HYDROGELS
FDA CLASSIFICATION GROUPS
Soft materials and Dk—depends on
Lenses with Rigid Gas Permeable Optics and Soft Hydrophilic Periphery—Hybrid Lenses
The New Generation Lens Material
8:
Optical of Contact Lens
9:
The Initial Examination
OCULAR MEASUREMENTS
Corneal Curvature—Keratometry (Fig. 9.2)
Corneal Diameter—HVID
Pupil Size
Palpebral Aperture and Lid Tension
Blink Rate
Tear Layer Assessment
Schirmer Test (Figs 9.4 and 9.5)
Phenol Red Thread Test
Break-up Time
Lipid Layer Evaluation
Tear Prism Height
Patient's Specific Needs
SUMMARY OF PRELIMINARY EXAMINATIONS
Recording History and Assessment of Indication/Contraindication
Ocular Examination
10:
Selection of the Lens—Options Available
11:
Soft Contact Lens Fitting
SUMMARY
12:
RGP—Rigid Lens Fitting
PROCEDURE FOR RGP FITTING
Measure
Keratometry
Refraction
Tear Quality
Type of Astigmatism Affects Lens Choice
HVID
Pupil size
TRIAL LENS SELECTION
The Trial Sets
Selection of the Lens
Base Curve
Overall Diameter Selection
Power of the Trial Lens
How to Estimate Contact Lens Power in RGP Bases on Spectacle Prescription
Other Parameters: Optic Zone, Peripheral Curves
Optic Zone is
Peripheral Curves are usually
Peripheral Curve width
Central Thickness
Material
Insertion of the Lens on the Eye and its Adaptation
ASSESSMENT OF FIT
With a Torch or Diffuse Illumination and White Light of Slit-lamp
Fluorescein Evaluation
Central
Mid-peripheral
Edge
Diameter
Over Refraction
Central Thickness and Flexure and the Material to be Ordered
Tint
SUMMARY: STEPS
13:
Soft Toric Contact Lens Fitting
SUMMARY—TORIC SOFT LENS FIT
14:
Fitting Young Children with Contact Lens
15:
Fitting Contact Lenses in Presbyopes
BIFOCAL/MULTIFOCAL CONTACT LENSES
Translating Vision Type (Fig. 15.3)
Advantages
Disadvantages
Simultaneous Vision
Advantages
Disadvantages
Concentric Design
Central Near Segment
Central Distance Segment
Pupil Size Dependency
Diffractive Bifocal (Fig. 15.5)
Aspheric Designs (Fig. 15.6)
Aspheric back surface lens design
Aspheric front surface lens design
Modified Monovision
SUMMARY
16:
Keratoconus
CORRECTION OF KERATOCONUS WITH CONTACT LENSES
Keratometry Readings
Fitting Technique
Tips for Parameters Selection in Keratoconus
Diameter
Peripheral Curves
Power Calculation
Judgment—During Fluorescein Evaluation
Soper Lens Design
Fitting
Piggy Back Lenses (Fig. 16.4)
Rose K Lens (Fig. 16.5)
Progression
17:
Therapeutic Contact Lenses
COLORED CONTACT LENSES (Fig. 17.3)
Visibility (Handling) Tint
Cosmetic Tint
Transparent Tints
Opaque Tint
Prosthetic Contact Lenses
Tinting Methods
Fitting Guidelines for Prosthetic Lens (Figs 17.8A and B)
Lens Care
Disposables are Gaining Popularity
18:
EXtended Wear Lenses
19:
Lens Dispensing
20:
Contact Lens Care Systems
THE LENS CARE SOLUTIONS HAVE FOLLOWING PROPERTIES AND INGREDIENTS
Tonicity—0.9% NaCl
Degree of Acidity/Basicity pH—6.6 to 7.8 Comfort Range
Buffering Agent—Maintain pH
Viscosity—Increase Contact
Antimicrobial Activity
Commonly used Antimicrobial Agents in Contact Lens Solutions
Surfactants
Stabilizers
LENS CARE REGIME STEPS
Cleaning (Figs 20.1 to 20.3)
Enzymatic Cleaners (Fig. 20.4)
Procedure
RINSING AGENTS (Fig. 20.5)
DISINFECTION
Heat or Thermal Disinfection (Fig. 20.6)
Advantages
Chemical Sterilization (Figs 20.7A and B)
Advantages
Disadvantages
Oxidative Chemical Disinfection—Hydrogen Peroxide (Fig. 20.8)
One step peroxide
Two step peroxide
Lubricating or Rewetting Drops (Fig. 20.9)
Efficacy
Compliance
Multipurpose Solutions
Disinfection of Trial Lenses
OVERVIEW OF LENS CARE SYSTEMS
Optional Lens Care Systems
21:
Instructions to Patients
RIGID LENS INSERTION AND REMOVAL
Basic Step—Wash Hands Insertion Technique
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Other method of recentration
Removal Technique (Fig. 21.9A)
Step 1
Step 2
Step 3
Step 4
Step 5
Using two fingers (Fig. 21.9B)
Locating the decentered lens
CLEANING AND DISINFECTION
Soft Contact Lens Care Regimen: Daily Steps
Clean
Rinse
Soaking and Disinfect
Rinse
Apply the Lens on the Eye
Rigid Lens Care Regimen: Daily Steps
Clean
Rinse
Soaking and Disinfecting
Rinse
Apply on the Eye
Soft Lens Wearning Schedule
Normal Adaptation Symptoms
DO'S AND DON'TS OF LENS CARE
Reinforce these Do's
Warn these Don'ts
Reinforce Lens Care Tips
Care of Lens Case (Fig. 21.12)
Soft lens care regimen
RGP lens regimen
USE OF COSMETICS WITH CONTACT LENSES
Hints
Problems—that may Arise from Cosmetics
Follow-up or Next Appointment
22:
Follow Up Care
THE AFTER CARE ROUTINE
Subjective Assessment
Patient Discussion
Objective Assessment
Visual Acuity
Retinoscopy Over the Lenses
Slit-lamp Examination
Re-examine without Lenses Next
Slit-lamp Examination
Keratometry
Refraction
Dry Eye Tests
“Successful” Contact Lens Wearer
Improve Compliance
Replace Lenses
Recommendations—Follow Up Schedule
Next Follow Up Date
23:
Contact Lens Manufacturing and Verification
LATHE CUTTING (Fig. 23.1)
Hydration of Soft Lenses
Advantages
Disadvantages
SPIN CASTING
CAST MOLDING
Quality Assurance and Inspection
Sterilization
RGP Manufacturing
Tinting of RGP Lenses
Soft Contact Lens Manufacturing
CONTACT LENS VERIFICATION
Base Curve
Radiuscope (Fig. 23.4)
POWER VERIFICATION
Central Thickness
Surface Quality
Blend and Edge Shape (Fig. 23.9)
Material
Verification of Parameters—Summary
24:
Rigid Contact Lens Modification
25:
Contact Lens Complications
THE ADVERSE EFFECT OF LENSES
Effect on Epithelium
Effect on Stroma
Edema (Striae and Folds) (Fig. 25.15)
Stromal Thinning
Vascularization
Corneal Distortion
Effect on Endothelium
Endothelial Blebs (Fig. 25.17)
Appendices
INDEX
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Index
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