Syhi.pptx

SILICONE HYDROGEL CONTACT LENS

Mohamad Arief Herdiawan

Introduction

Oxygen

Attached to the Cornea

Initially used for

correcting refractive

errors

More than 30 millions

Americans use contact lenses

and 128 millions

worldwide.

Contact Lens

Introduction

•Hard• Rigid

gas permeable

•Hydrogel•Hybrid

Material

• Daily wear • Continuous

or extended • Flexible• Convention

al • Disposable • Occasional

Wear and Replacem

ent

• Optical• Therape

utic• Cosmeti

c

Purpose• Spherica

l• Aspheric • Toric • Bifocal • Progress

ive • Multicur

ve • Reverse

curve

Design

History of Contact Lens

• (1827) : a spherical glass jelly over the corneal surface• 1888, Eugene Kalt : contact Lens for keratoconus

Sir John Herschel

History of Contact Lens

(+)• Hydrofilic• Less

mechanical effect, much comfort

Hydrogel(+) : • High oxygen

transmissibility

Silicon

( - ) : • Hydrophobic• mechanical

effects

( - )• Oxygen

permeability depends on water content

Silicone Hydrogel

Oxygen is primarily

transmitted through the

silicone component of the lens

material increasing the oxygen

permeability

silicone rubber is combined

with conventional

hydrogel monomers

Introduced in 1999

high oxygen transmissibili

ty

Resistance to dehydration

Good fluid transport

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AAO

Types of Silicone Hydrogel CL

Advantages

1. Very high Dks A term describing the oxygen permeability of a

lens material D : diffusion coefficient for oxygen movement

in the material k : solubility constant of oxygen in the material Significantly reduce the incidence of hypoxic

complications

2. Suitable for extended wear High-Dk, low-water-content silicone

hydrogels are used for extended wear. Study : the annual incidence of severe

keratitis among those who wear conventional hydrogel lenses overnight is 100/10,000 wearers.

Silicone hydrogel lenses : 20/10,000 wearers

3. Minimal Dry Eye Symptoms Sensation of dryness is related to a variety of factors,

lens material dehydration include. Silicone hydrogel contacts generally are low-water

lenses and may help reduce dry eye symptoms high-water lenses draw tears away to stay properly

hydrated Highly oxygen permeable SiH materials support a

connection between improved comfort and dryness and the level of available oxygen.

4. High durabilitySiH materials have a higher modulus of

elasticity than the majority of conventional hydrogel materials easier to handle and potentially more durable

Disadvantages

1. Mucin Balls Spherical and translucent or opalescent

bodies sandwiched between a CL and the cornea

20 and 200 mm in diameter

2. Not available in Complex Designs Astigmatism is not easily corrected The lens contours to the eye and corneal

astigmatism frequently remains uncorrected.

Special designs of toric lenses available to correct astigmatism of dioptric powers up to 4D

Types of contact lensesContact lenses can be classified by the nature of the

material from which they are made, by their wearing schedule, by their purpose, or by their design.

Nature of the Material 1. Hard 2. Rigid gas permeable 3. Hydrogel 4. Hybrid

Indications for contact lens1. Optical Indications Most contact lens wearers fall into this group. The great majority are

myopic with or without astigmatism.

2. Medical Indications Keratoconus Irregular Astigmatism and/or Corneal Opacification Anisometropia Unilateral Aphakia Nystagmus After Refractive Surgery After Penetrating Keratoplasty

3. Cosmesis Prosthetic, tinted lenses are often used in patients with a disfiguring corneal scar or an iris

coloboma to improve the aesthetics of a nonseeing eye or to occlude an iris coloboma. Cosmetic lenses may also simply be used to alter the color of the eye.

4.Therapeutic Lenses treatment of a corneal disease

ContraindicationsEvaluate the patient’s motivation, ocular needs, and ocular and medical

history. Unmotivated patients tend not to adhere to the prescribed methods and care regimens for the contact lens, putting them at greater risk of complications.

1. Any acute or subacute inflammation of the anterior segment of the eye2. Acute and chronic ocular infections3. Any eye disease affecting the cornea, conjunctiva, and lids (e.g., epithelial

fragility, endothelial failure, dry eye, allergy, pinguecula, pterygium)4. Corneal hypesthesia5. Uncontrolled glaucoma6. Vitreocorneal touch in aphakia7. Psychological intolerance to the placement of a foreign body in the eye

Advantages and disadvantages of contact lensescompared with spectacles

Advantages • Wider field of view.• Better for refractive anisometropia.• Retinal image size almost normal with

refractive ametropia (e.g. with aphakia, high minus).

• No unwanted prismatic effects with eye movements.

• Less convergence required by hyperopes for near vision.

• Avoid surface reflections.• Minimal oblique or other aberrations.• Cosmetically superior.• More practical for sports.• Avoid weather problems (rain, snow,

fogging up).• Provide good acuity for irregular

corneas (keratoconus, trauma, and subsequent to refractive surgery).

• Therapeutic uses.• Vocational uses

Disadvantages

•Time required for fitting and adaptation.• Handling skills required by patient.•Hygienic procedures and lens disinfection necessary.•Wearing time may be limited.•Range of useful tints limited, especially with complex lenses.•For binocular problems, only limited vertical prism possible.•Greater convergence required by myopes for near vision.•Lenses can be lost or broken.•Problems with foreign bodies.•Peripheral flare (especially at night).•Deteriorate with use and age.•Retinal image size disparity in axial anisometropia•Maintenance costs.•Greater overall expense.•Administrative procedures for disposable lens supplies

Rigid gas permeable A rigid gas permeable lens is made of a

material with a molecular structure that permits the passage of oxygen and carbon dioxide gas

Advantages • High oxygen

permeability• Reduced spectacle

blur• More comfort• More stability, better

centration• Prevent lid impact

and blink inhibition• Ease in handling

Disadvantages

• Need adaptation• Uncomfortable for

novice• Expensive cost• Poor wetting• Greater fragility• Easily scrathed

surfaces

RGP CONT..

Advantages • Low maintenance cost (can be clean & polished easily)

• Good visual performance

• Better masking of astigmatism

• Less glare• Resist deposits than

soft lens• More durable, last

longer

Disadvantages

• Need adaptation• Uncomfortable for

novice• Expensive cost• Poor wetting• Easily scrathed

surfaces

RGP

Indication •Rigid / soft lens drop out•Keratoconus•Excessive spectacle blur•Patients susceptible to flare•High corneal astigmat up to 2.5D•Giant Papilary Conjuctivitis•Rigid lens discomfort

Contraindications

•Sports activities•Wide pupil (> 6mm)•Acute inflammation•Uncontrolled Glaucoma•Psychologycal intolerance

RGP

water content (degree ofhydration) of a hydrophilic contact lensThe water content represents the percent water contained in the

polymer matrix and ranges from 35% to 80% in hydrogel contact lenses.

Hydrophilic contact lenses can be classified in two categories based on water content:

1. Low water content (less than 50% water)2. High water content (greater than 50% water)

The oxygen transmissibility of a hydrophilic contact lens is directly related to its water content and inversely related to its thickness.

Ionic Content of Hydrogel CL Contact lenses may also be classified by

their ionic nature. Ionic materials are negatively charged and therefore more reactive, whereas nonionic materials are electrically neutral. The ionic lenses are more prone to protein deposition on the surface of the lens.

therapeutic contact lens indications● Pain reduction caused by defects or lesions of the corneal

epithelium● More rapid restoration and preservation of corneal epithelial

integrity● Protection of the cornea in cases of corneal drying● Protection of the cornea in cases of mechanical injury secondary

to entropion and trichiasis● Restoration of the anterior chamber after shallowing caused by

small corneal perforations● Delivery of medications to the ocular surface

benefits of using a therapeutic contact lens?

● Alleviation of pain ● Treatment of corneal disease ● Improvement of visual acuity

The following testing should be completed at the follow-up visit for hydrophilic soft lens wearers: 1. Visual acuity measurement 2. Overrefraction 3. Assessment of the patient’s contact lens–related comfort 4. Evaluation of the length of wear 5. Evaluation of lens maintenance 6. Biomicroscopy (examination for microcysts, fluorescein staining of the cornea, infiltrates,

neovascularization, edema, and erosions) The follow-up schedule depends on the sensitivities and individual characteristics of each

eye. First-time contact lens wearers should be examined 2 weeks after the initial dispensing visit and then at 3- to 6-month intervals during the first year, depending on the wearing schedule and lens type. In wearers who intend to sleep with their contact lenses, the clinician should verify that there are no contraindications to extended wear, with immediate discontinuation of use at the first signs of any adverse effects on the cornea. For those wearers who do not intend to sleep with their contact lenses, an annual examination is sufficient. In follow-up examinations, the clinician should always verify that the instructions for contact lens maintenance are being adhered to. Many eyes are very sensitive and show signs of hypoxia and overwear. In these cases, wearing time with a contact lens of low permeability should be reduced 4 to 6 hours per day

The TBUT measures the interval between the last

complete blink and the first appearance of a dry spot or disruption of the tear film

Three TBUT scores were averaged : > 10 seconds = normal < 10 seconds = presence of dry eye

Schirmer TestTest Topical

anesthesiaTime Nasal

StimulationNormal value

Basic tear secretion

+ 5 min - > 10 mm

Schirmer I - 5 min - > 10 mmSchirmer II - 5 min + > 15 mm