1. Introduction to Contact Lenses
Intoduction to Contact Lenses

2. Objectives Describe evolution of contact lenses
Describe types of contact lenses
Identify basic parameters of contact lenses
Identify uses and benefits
Describe fitting procedures and care regimens
Objectives
This module covers the history and development of contact lenses; characteristics of contact lens materials; types of contact lenses; and the benefits of contact lenses over spectacles.
Upon completion of this module, you will be able to:
Describe the evolution of contact lenses
Describe the types of contact lenses available today
Identify the basic parameters of contact lenses
Discuss the uses and benefits of contact lenses
Describe fitting procedures and care regimens for contact lenses.
Intoduction to Contact Lenses

3. Contemporary History Four significant milestones:
1940s – development of PMMA (hard lenses)
1970s – development of HEMA (“hydrogels” or soft lenses)
1980s – development of rigid gas permeable (RGP) lenses
1999 – development of silicone hydrogel lenses
Contemporary History
There are four significant milestones in the contemporary history of contact lens development:
1940s–development of PMMA (hard lenses)
1970s–development of HEMA (hydrogels or soft lenses)
1980s–development of rigid gas permeable (RGP) lenses
1999–development of silicone hydrogel lenses
In 1938, Muller and Obrig developed the first scleral contact lens made entirely of plastic – a polymethyl methacrylate (PMMA) resin originally used in the production of aircraft canopies.
Kevin Touhy developed the first plastic corneal lens in 1947, using PMMA. Touhy established the need for tear exchange under the lens to provide oxygen, setting the standard for hard lens fitting. PMMA or hard lenses were widely prescribed until the 1970s, and are still fit in many countries today.
In the late 1950s, Otto Wichterle of Czechoslavakia developed the hydrogel polymer, hydroxyethyl methacrylate (HEMA), which formed the basis for soft contact lenses. HEMA absorbs water to become soft and flexible, while permitting the transmission of oxygen.
Intoduction to Contact Lenses

4. What is a Contact lens ?
Contact lens is an Optical device or lens which is used to correct Refractive errors,
change color of the eye or for therapeutic purposes

5. Types of Contact Lens:
Hard Contact lens - Obsolete as does not allow Oxygen to pass through
Rigid Gas Permeable lens (semi-soft lens)- allows better oxygen transmission.Poor comfort. Cumbersome fitting procedure
Soft Contact lens - allows good oxygen transmission. Highly comfortable. Easy to fit.

6. Conventional Soft Lens Materials
HEMA ( Hydroxy Ethyl Methacrylate) is the most common material for conventional lenses
FDA has divided SCL materials into 4 groups on the basis of water content & Ionicity
Group1- LWC,Non-Ionic
Group2 –HWC,Non-Ionic
Group 3- LWC, Ionic
Group 4 –HWC, Ionic
Conventional Soft Lens Materials
The first soft lenses were used to correct mild myopia and hyperopia in a limited range of powers. Today, they also are prescribed to correct astigmatism and presbyopia, as well as enhance or change the color of the eye. Soft contact lenses, which are considered medical devices by most governmental regulartory bodies (e.g., the FDA), can be used to correct medical conditions. Aphakic lenses are used to improve vision following cataract removal. Bandage lenses may be applied to protect the eye and enhance healing. Some hydrogel lenses may even be used to deliver medication to the eye.
Intoduction to Contact Lenses

7. RGP Lens Materials RGP lenses combine standard PMMA with silicone
PMMA is a clear plastic material that is impermeable to oxygen
Offer excellent vision
Easy to handle, durable
Simple to care for
RGP Lens Materials
Rigid gas permeables lenses generally combine standard PMMA material with silicone. PMMA, or polymethyl methacrylate, is a clear plastic material that is impermeable to oxygen, which can result in physiological problems if the lens is poorly designed or fitted. Silicone is a material that is extremely permeable to oxygen.
RGP lenses afford excellent vision, especially for patients with moderate or severe astigmatism. These lenses are easy to handle, durable and simple to care for. The high oxygen permeability (Dk) of some RGP materials makes some lenses suitable for extended wear. While most patients initially experience some discomfort with RGP lenses, they become unaware of the lenses after a brief adaptation period.
Intoduction to Contact Lenses

8. Silicone Hydrogel Lens Materials
Silicone and hydrogel are combined to create a revolutionary soft contact lens material
Exceptional oxygen permeability
Excellent on-eye performance and comfort
Silicone Hydrogel Lens Materials
Recent advanced technologies have been applied to combine silicone and hydrogel to create a revolutionary soft contact lens material. The silicone component of the material contributes exceptional oxygen permeability for ocular health, yielding over four times that which conventional hydrogel lens materials typically allow. The hydrogel component facilitates fluid transport for excellent on-eye performance and comfort.
Clinical studies and early market experience with these new materials has demonstrated significantly fewer adverse responses with extended or continuous wear up to 30 days, especially those related to hypoxia (oxygen deprivation).
Intoduction to Contact Lenses

9. Wear Modality
Wear modality refers to how the contact lens if worn by the patient.
Wear modality is divided into two groups:
Daily wear
Extended wear
Continuous wear
Wear Modality
Wear modality refers to how the contact lens is worn by the patient. Wear modality can be divided into two groups:
Daily wear
Extended wear
Intoduction to Contact Lenses

10. Replacement Schedule
Replacement schedule refers to how often contact lenses are replaced
Lenses are generally replaced on a “traditional schedule” or a planned replacement/disposable schedule
Replacement Schedule
A contact lens replacement schedule refers to how often contact lenses are replaced. Contact lenses are generally replaced on a “traditional schedule” or on a planned replacement/disposable schedule.
Intoduction to Contact Lenses

11. “Traditional” Contact Lens Wear
Patients once wore same pair of lenses until they experienced discomfort, or lens was lost or torn.Average life of a traditional lens is 1 year.
Today, “traditional lens replacement” has been replaced with Planned Replacement/ Disposable schedules
“Traditional” Contact Lens Wear
Historically, when contact lenses were prescribed, the patient wore the same pair of lenses for six months or more, or until they experienced discomfort, or a lens was torn or lost. For many reasons, including advances in lens design and materials, “traditional lens replacement” has been replaced with Planned Replacement/ Disposable schedules and is much less common today
Intoduction to Contact Lenses

12. Planned Replacement/ Disposable (PRD)
Contact lenses are replaced more frequently (one to three months)
Disposables are discarded at end of wear and never reused
Disposable may be worn daily or extended wear basis
Planned Replacement/Disposables
In recent years, contact lenses and planned replacement programs have been developed which make it practical for eye care professionals to recommend more frequent lens replacement. These frequent, planned-replacement programs dictate that lenses be worn and cared for on a daily wear or extended wear basis, and replaced on a regular schedule (e.g., monthly or quarterly replacement).
Disposable contact lenses, by strict definition, should be discarded at the end of the period of wear. They should not be reused and are hence, ‘disposable.’ In most countries, however, ‘disposable’ has come to mean one or two week replacement, independent of the number of uses. Disposable lenses may be worn for either daily wear or extended wear, depending on the parameters of the lens and practitioner recommendation.
Intoduction to Contact Lenses

13. Advantages of Contact lens over Spectacles:
Wider field of view (Improved Peripheral Vision)
Active lifestyle
No tell tale marks , no sliding down the nose
No fogging wih sudden temperature changes
Natural Good Looks
Intoduction to Contact Lenses

14. Advantages of Contact lens over Spectacles:
Better clarity of Vision
Actual size of object is seen unlike in high power spectacles
IMMENSE SELF-CONFIDENCE
See Better, Look Better, Feel Better
Intoduction to Contact Lenses

15. Indications for Contact Lens Wear
Myopia
Hyperopia
Astigmatism
Presbyopia
Aphakia
Keratoconus
Astigmatism secondary to post-op/trauma
Corneal protection
Corneal healing
Occupational requirements
Indications for Contact Lens Wear
Contact lenses are especially indicated for certain refractive conditions such as high refractive errors, irregular astigmatism and anisometropia (a condition that exists when eyes have significantly different refractive errors).
Contact lenses are suitable for the following visual, medical and practical indications:
Myopia
Hyperopia
Astigmatism
Presbyopia
Aphakia
Keratoconus
Astigmatism secondary to post-op/trauma
Corneal protection
Corneal healing
Occupational requirements
Intoduction to Contact Lenses

16. Contraindications for Lens Wear
Anterior segment inflammation or infection
Chronic ocular allergy
Certain systemic diseases
Ptosis
Corneal hyposensitivity
Chronic dry eye
Poor quality or inadequate tearfilm
Occupational incompatibility
Noncompliant, unmotivated patient
Poor patient hygiene
Contraindications for Contact Lens Wear
While the majority of people can wear contact lenses successfully, there are circumstances where contact lens wear should not be worn, or at minimum should be considered very carefully.
The following conditions or circumstances may be contraindication for contact lens wear:
Anterior segment inflammation or infection including keratitis, blepharitis, and conjunctivitis
Chronic ocular allergy
Certain system diseases (e.g., diabetes, rheumatoid arthritis)
Ptosis (“drooping eyelid”)
Corneal hyposensitivity
Chronic dry eye
Poor quality or inadequate tearfilm
Occupational incompatibility (e.g., glass blower, biochemist)
Noncompliant, unmotivated patient
Poor patient hygiene
Intoduction to Contact Lenses

17. Contact Lens Design and Application
Intoduction to Contact Lenses

18. Single Vision Spherical Soft Contact Lenses
Myopia
Hyperopia
Presbyopia
Aphakia
Most widely prescribed contact lenses
Single Vision Spherical Soft Contact Lenses
Single Vision Spherical (SVS) soft lenses can be designed to correct myopia, hyperopia, minor astigmatism, aphakia and presbyopia over a wide range of correction ( to ). Spherical lens materials vary in water content, and are available in different base curves, thickness and diameters. SVS lenses are the most widely prescribed contact lenses.
Intoduction to Contact Lenses

19. Toric Soft Contact Lenses
Toric soft lenses correct the vision of patients with significant amounts of astigmatism. Toric lenses are designed to ensure the eye receives required correction at each of the major axes. Unlike soft spherical lenses, which rotate continuously on the eye, toric lenses must maintain a constant orientation. To ensure that the major axes of the lenses are properly positioned, toric lenses incorporate design features that provide a consistent and stable position in the eye.
Intoduction to Contact Lenses

20. Presbyopic Soft Contact Lens Correction
Presbyopic Soft Contact Lenses
Presbyopia is the increasing inability of the eye to focus on objects up close as the patient ages (loss of accommodation). Several methods are currently available to provide presbyopic correction.
Monovision
With a monovision or monofit system using SVS, or toric lenses, one eye is fitted with the proper distance vision power and the other with the power necessary for near vision. In the case of emmetropes, a single near vision lens is needed. In spite of these limitations, monovision is the most common and successful method of correcting presbyopia with contact lenses.
Bifocal and Multifocal Soft Contact Lenses
Bifocal and multifocal soft contact lenses are available in two basic designs – alternating and simultaneous vision. Distance viewing is directed through the top portion and near viewing through the bottom portion. With simultaneous vision designs, the patient looks through both the distance and the near portion at the same time, producing two images on the retina simultaneously. The brain must selectively suppress or ignore one image.
Intoduction to Contact Lenses

21. Cosmetic Tinted Soft Contact Lenses
Tinted contact lenses are available to enhance the color of the eye or change the color entirely. Initially, only transparent tints were offered. These lenses were effective only on blue and other relatively light-colored eyes. Tints include aqua, blue, green amber and brown. Opaque colored lenses were introduced for patients with dark eyes. These lenses mask the original color of the eye while introducing a new color. The centers of these lenses are clear to minimize interference with vision.
Intoduction to Contact Lenses

22. Therapeutic and Bandage Lenses
Promote corneal healing
Treat corneal/ocular disease
Collagen lenses offer good results
Therapeutic and Bandage Lenses
Therapeutic or bandage lenses are used to promote healing and/or treat certain corneal or ocular diseases. The normal blinking process can disrupt the corneal surface, slowing or preventing the healing process. Soft lenses act like a bandage, allowing corneal cells to regenerate when placed on a damaged cornea.
Collagen lenses represent a class of materials known as biopolymers made from the scleral tissue of animals. These biodegradable materials have a water content in excess of 90%, are highly permeable to oxygen and have been shown to facilitate corneal healing following anterior segment surgery. They are also therapeutically used to deliver drugs to the eye over several days.
Intoduction to Contact Lenses

23. Lens Care Systems
Deposits composed of protein, lipids, mucin and other organic and inorganic substances need to be removed
Cleaning
Surfactant – to remove surface deposits
Enzymatic – to remove protein deposits
Lens Care Systems
In order to maintain proper performance and to avoid contamination, contact lenses must be cleaned and disinfected on a regular basis.
Cleaning
During lens wear elements of the tearfilm deposit on the surface of the lens. Deposits are composed of protein, lipids, mucin and other organic and inorganic substances. These deposits can compromise contact lens wear if they are not regularly and effectively removed. Clinical complications that are associated with deposits include:
Irritation and reduced comfort
Reduced visual acuity
Shortened lens life
Increased potential for infection
Increased potential for Giant Papillary Conjunctivitis (GPC)
Reduced oxygen transmissibility.
Contact lens care regimens are dispensed by eye care practitioners and must closed adhered to by the patient to reduce the risk of adverse responses to leans wear.
Two types of cleaners may be used. A surfactant cleaner is used after each removal from the eye prior to disinfection to remove organic and inorganic surface deposits.
An enzymatic cleaner is used to reduce any protein deposits that accumulate on the lens.
Intoduction to Contact Lenses

24. Lens Care Systems Rinsing Disinfection Storage Chemical disinfection
Thermal disinfection
Hydrogen peroxide
Storage
Lens Care Systems
Disinfection Methods
The proper use of a contact lens disinfection system is imperative to prevent contact lens related infection. While the eye does have a natural defense system, it cannot effectively reduce large numbers of microorganisms (bacteria, viruses, etc.) introduced by contaminated contact lenses.
Disinfection systems work to significantly reduce the number of microorganisms present on the lens to a safe level, prior to insertion into the eye. Patient compliance to the lens care regimen plays a significant role in maintaining ocular health. Without the proper use of disinfections systems, the risk of microbial infection is increased.
Chemical disinfection involves bactericidal agents incorporated into saline solutions.
Bausch & Lomb Multi-Plus Solution is a one step cleaner/ disinfectant that is appropriate for soft lens care.
Thermal disinfection requires heat to disinfect the lenses when they are stored in saline.
Hydrogen peroxide (H2O2) can be used as a disinfection method however, a neutralization step is required to chemically change hydrogen peroxide into water and oxygen prior lens wear.
Intoduction to Contact Lenses

25. Lens Lubricants
Lens lubricants are used when lenses become dry and uncomfortable
Extended-wear lens patients are encouraged to use lubricants prior to sleep and upon waking
Lens Lubricants
Lens lubricants are available for contact lens wearers whose lenses become dry and uncomfortable, a relatively common end of day complaint. Patients with extended-wear lenses are encouraged to use a lubricant prior to sleep and upon waking to ensure optimal lens comfort and performance.
Intoduction to Contact Lenses

26. For Further Queries Contact :
Ms. Priyanka Singh
Head – Optometry Service –

27. End
Intoduction to Contact Lenses