RGP insights

RGPs and Soft Torics:Making the Right Decision

BY EDWARD S. BENNETT, OD, MSED
MARCH 1999

When deciding what lens material is preferable for a given patient, several factors need to be considered. The final decision, however, should be made in each individual patient's best interest.

This is especially true when deciding between a soft toric contact lens and an RGP contact lens for astigmatic patients. You should consider both options. The following represents my recommendations.

When RGPs Are Preferred

• Critical vision is important and pertains not only to those individuals with excessive near demands, but also to those in need of optimum vision at night, especially if driving is involved.
• If the sphere-cylinder refractive error ratio is less than or equal to 2:1, RGPs should be fit.
• If the refractive cylinder is equal to or greater than 2.50D, and the corneal cylinder is also 2.50D or greater, a bitoric RGP will provide a stable and non-fluctuating vision correction.
• An RGP will provide a healthy alternative for irregular corneas while optimizing vision via the creation of a more spherical corneal surface.
• Lenses for hyperopes require two times more Dk than lenses for myopes for an edema-free corneal environment. The availability of high (>50) and hyper (>100) Dk RGP lens materials can meet this requirement. The thickness required, in addition to limited tear exchange of soft toric lenses, however, can potentially result in edema-related complications over time.
• Individuals desiring extended wear, or those in occupations where long wearing periods are necessary, benefit from the eye health and vision of RGPs.
• The astigmatic correction and the availability of numerous multifocal and bifocal lens designs providing satisfactory vision at multiple distances make RGPs a good alternative for the presbyopic patient.
• RGPs appear to slow down the progression of myopia in young people while providing them with an option that will often result in their return to the prescribing practitioner for their services.
• Patients desiring a non-surgical method of reducing or eliminating their existing myopic correction may benefit from orthokeratology.
• Borderline dry eyes: whereas this is certainly patient dependent for spherical refractive errors, the greater oxygen transmission would favor RGPs as the initial lens for astigmats.
• If poor or fluctuating vision or induced complications exist with soft torics, RGPs are indicated.

When RGPs and Soft Torics are Comparable

• Greater than 2:1 Sphere-Cylinder Ratio -- RGPs should be considered for any astigmat unless otherwise motivated.
• Regarding athletics, unless wind and dust are particularly bothersome, RGPs can be designed large with a low-medium edge lift to minimize displacement and loss. Visual acuity is especially important in many sports.

When Soft Torics Are Preferred

• For high reactors during the preliminary testing.
• For patients who are only going to be wearing their contact lenses occasionally.
• For patients who are a previous failure with RGPs due to contact lens awareness or adaptational problems.
• For patients who have an against-the-rule cylinder cornea.
• For patients who have equal to or greater than 0.75D residual (internal) astigmatism.
• For patients who spend much of their time in a windy or dusty environment. CLS

The author would like to acknowledge Drs. Shelley Cutler, Art Epstein, Milton Hom, and Jon Kendall for their assistance.

Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis and executive director of the RGP Lens Institute.