Bifocal RGP Contact Lenses for Progressive Myopia

By David W. Hansen, O.D.

Clinically, we have known for years that rigid contact lenses retard refractive changes, especially throughout the teen-age years. During the second semester of school, especially in northern regions, myopic changes are more prevalent due to increased educational demands and inclement weather that keeps people indoors doing near activities. A convergence excess posture of the eyes often results, but RGP bifocal contact lenses can supplement reading comfort and help slow the myopic shift.

THE VALUE IN BINOCULAR EVALUATION

Most of us learned that the clinical evaluation should consist of three parts: evaluation of ocular and systemic health, refraction and correction of the optical system, and assessment of the binocular components. But in this day of managed care within a litigious society, it seems we focus on the first two components and neglect the third.

Phorias and ductions give a simple yet thorough evaluation of the patient's binocularity and can be performed in just a few minutes. I'm finding more and more convergence excess in the pediatric population, so these tests are important for a lifetime visual treatment program.

Most lateral alignment of the eye posturing should be between 4 and 6 exophoria. When there's more esophoric posture for near, plus lenses and especially bifocals will reduce the accommodative stress. The therapeutic value of bifocal RGP contact lenses makes them more beneficial than spectacles.

CORRECTING TWO PROBLEMS WITH ONE DESIGN

The following patient demonstrates the advantages of using RGP multifocals to aid binocular vision, improve comfort and help retard myopic progression.

A On January 12, 1989, J.G., a 13-year-old girl, demonstrated:

• OD -2.00D +0.25 x 165; 20/20
• OS -2.00 +0.50 x 170; 20/20
• Distance phoria: orthophoric
• Near phoria: 5 esophoric
• K's: OD 44.75/44.50 @104;
  OS 44.37/44.62@115

We prescribed single vision RGP lenses.

A On February 13, 1990, she demonstrated:

• OD -2.25 +0.25 x 170; 20/20
• OS -2.25 +0.50 x 175; 20/20
• Distance phoria: 1 exophoria
• Near phoria: 16 esophoria
• K's: OD 44.62/44.37 @ 91;

OS 45.00/44.50 @ 53

On March 12, 1991, J.G. was still wearing rigid contact lenses, but losing motivation. We prescribed Softperm lenses (combination RGP/soft lens), also a single-vision modality. During this time, we were concerned about the convergence excess.

A On April 15, 1991, J.G. returned with significant changes in the subjective exam:

• OD -3.50 +0.50 x 105; 20/20
• OS -3.75 + 0.25 x 105; 20/20
• Near lateral phoria: 15 esophoria

J.G. wanted to continue with single-vision contact lenses.

A On September 10, 1992, subjective examination was:

• OD -4.50 +0.50 x 75; 20/20
• OS -4.00 +0.75 x 105; 20/25+
• Near esophoria: 22 diopters

Due to the increased myopia and the increased convergence excess, we prescribed an aspheric multifocal RGP design (Conforma's VFL-3). J.G. was very comfortable with the lenses, wearing them 15-16 hours per day.

A On May 24, 1995, there were no overrefractive changes; her visual acuity with contact lenses was 20/20 in each eye.

• Near phoria: 8 esophoria
• K's: OD 43.50/44.37@91;
  OS 43.87/44.75@73

A On December 19, 1996, the subjective examination was:

• OD -4.00 +0.25 x 115; 20/20
• OS -4.75 +0.50 x 70; 20/20
• Near phoria: 14 esophoria
• K's: OD 43.37/44.12@112;
  OS 44.12/45.00@90

In four years of RGP multifocal contact lens wear, there was minimal change in J.G.'s myopic progression and an improvement in esophoric posture for near through the distance lens. With the +2.00D add effective power, she is orthophoric for near.

Now a senior in college, J.G. represents a population of young people with progressive myopic changes as well as visual accommodative problems throughout their adolescent and young adult years. I feel that RGP bifocal contact lens wear in these patients helps reduce both myopic shift and functional vision symptoms such as headaches. CLS

Dr. Hansen, a cornea and contact lens diplomate and fellow of the American Academy of Optometry, is in private practice in Des Moines, Iowa.