PRESENTATIONSOFT TORIC CONTACT LENS

INDICATIONS AND CONTRAINDICATIONS

TORIC

The term is used to describe specially designed soft toric contact lens that is used to correct astigmatism.

Soft toric contact lens are those lenses having different power in different meridians.

DEFINITION:

ACCORDING TO SURFACE:•FRONT TORIC LENS•BACK TORIC LENS•BITORIC LENS

ACCORDING TO LENS MATERIAL •HYDROGEL •SILICONE HYDROGEL

ACCORDING TO WEARING SCHEDULE•DISPOSABLE LENSES•EXTENDED WEAR LENSES

ACCORING TO COLOURED TORIC LENSES

ACCORDING TO SURFACE:

Front surface toric are capable of correcting both corneal and lenticular astigmatism upto about 4.50 Diopters. They are wide variety of both corneal and semi-scleral. Stabilization can be means by prism ballast, truncation or dynamic stabilization. The back surface may be either spherical or aspherical.

FRONT TORIC:

BACK SURFACE TORICBack surface toric have envolved logically from the fact that most of the astigmatism encountered in practice is predominantly corneal. The back surface of the lens is essentially designed to neutralize the toric cornea by replacing it with a spherical front surface. Cylinder as high as 6.00 Diopters can be corrected with back surface toric.

BITORIC Bitoric contact lens are the type of toric soft contact with two different curves, one curve is on the front surface and other curve is on the back surface. It is best to utilized when corneal cylinder is equal to or exceeds 2.50 Diopter. The two curves allows the saddle principle to provide the alignment fitting relationship in both meridians.

COLOURED TORIC CONTACT LENS

Toric lenses are suitable for astigmatism patients wanting to wear coloured contact lenses.

HYDROGEL LENSES

ACCORDING TO LENS MATERIAL

These lenses are made up of hydrophilic ("water-loving") plastics called hydrogels

This water-loving characteristic, the water content of various hydrogel contact lenses can range from approximately 38 to 75 percent.

Low water content (less than 40 percent water)Medium water content (50 to 60 percent water)High water content (more than 60 percent water)

Another feature of hydrogel materials used for soft contact lenses is their surface charge, which can affect how quickly protein deposits form on the lenses during wear.

SILICONE HYDROGEL LENSES

Silicon hydrogel is the name of a group of flexible, plastic like materials that contains silicon, carbon, oxygen and other chemicals. It is use to increase the oxygen permeability of contact lens.

It enables five times more oxygen to reach to the cornea than regular hydrogel lenses.

It is also used in the production of RGP lenses to improve oxygen permeability of the lenses.

SUFFIX: FILCON (E.g: omafilcon, methafilcon, hilafilcon etc ).

• ADVANTAGE

S• Very

high DKs available.

• Suitable for extended wear.

• Rapid adaptation.

• Suitable for patients with vascularization

• Good dehydration characteristics.

• Easier handing because of lens rigidity.

• Low uptake of fluorescein. During aftercare.

• DISADVANTAGES

• Limited range of complex designs (toric, bifocals).

• Many available only as disposable.

• Greater incidence of CLIPC.

• Frequently exhibit mucin balls.

• More expensive.

BENEFITSIt reduces the various conditions like:

Hypoxia

red eyes

blurred vision

eye discomfort

rate of eye infections etc.

ACCORSDING TO WEARING SCHEDULE

DISPOSABLE LENSES:

The wearing of contact lenses only during waking hours, usually daily, weekly, fotirnightly or monthly.

• ADVANATGE

S• Reduc

ed risk of allergies and infection.

• Eliminate the need for professional lens cleaning.

• Cost saving

• Ideal for children requiring soft lenses.

• Theoretically better for most extended wear.

• Spare lenses are also available.

• Lenses rearly reach the stage where they build up deposits.

• Less time and effort required with lens cleaning.

• DISADVANTAGES

• Increased cost on an annual basis

• cost management

• Lenses wear out and must be replaced in a timely fashion.

EXTENDED WEAR

the use of lenses which are worn continuously ( without removing) during sleep and waking hours. The waking period may vary from 24 hours to seven days (usually) or longer.

• ADVANTAGE

S• Can

usually be worn up to seven days without removal.

• Some lenses are FDA-approved for up to 30 days.

• Available in tints 

• DISADVANTAGE

S• Requir

e regular office visits for follow-up care.

• Could increase risk of complication.

• Require regular monitoring and professional care.

• Handling may be more difficult

• INDICATIONS

• Vision is unsatisfactory with a spherical soft lenses.

• Astigmatism is 0.75 D or greater.

• Tolerance is poor with RGP lenses.

• Keratometry and Optical consideration indicate that a rigid lens require a much more complex, bitoric design.

• CONTRAINDICATION

• Astigmatism is corneal and rigid lens tolerance is good.

• Existing rigid lens wearer.

• Irregular astigmatism.

• Monocular patients.

REFERENCE: MANUAL OF CONTACT LENS

AMERICAN ACADEMY

http://www.opto-centar.hr/eng/guide-to-contact-lenses.html

http://www.slideshare.net/Glenmorevision/types-of-contact-lenses

www.aoa.org

http://www.gpli.info/pdf/2013-q3-case-smith-stephen.pdf

http://optometry.berkeley.edu/class/opt260a/gasperm_fit_pp/rgp_torics.htm