prescribing for presbyopia
A New Lens Joins The Soft Lens Bifocal Parade
BY N. REX GHORMLEY, OD, FAAO
Bausch & Lomb released the SofLens Multifocal in the United States in Fall 2002. It is a center-near lens design with an aspheric anterior surface and a posterior spherical bi-curve. Plus power
power gradually increases toward the center in both the low and high add powers, but the high add lens center has a distinct central zone of greater plus power. Table 1 lists the lens parameters.
Material and Replacement
The SofLens Multifocal is cast-molded in polymacon, a Group I low water (38 percent) non-ionic polymer. Polymacon is durable, resists lens deposits and dehydrates slower than most higher water content lens polymers. The major disadvantage of polymacon is its very low oxygen permeability (Dk 8.4). This could be a concern in moderate to high plus powers and high minus lenses.
This lens is approved only for daily wear. B&L suggests two-week replacement. I would suggest monthly replacement for many patients because polymacon's "excellent tear strength" and "low-deposit profile," as reported by B&L, should cause minimal problems.
Good candidates for the SofLens Multifocal have normal corneal physiology, less than 0.75D corneal astigmatism, motivation and realistic expectations. Patients who want these lenses to provide better vision than their bifocal glasses are usually not good candidates. Active patients who hate glasses may be excellent candidates.
Use diagnostic lenses to evaluate visual performance of the SofLens Multifocal. Determine distance power from your refraction. Use the spherical equivalent and compensate for the vertex distance. Try the low add lenses for early presbyopes (<50 years). For more advanced presbyopes (>50 years), I start with a low add in the dominant eye and a high add in the non-dominant eye.
Try the 8.8mm base curve first. Check distance and near visual acuity binocularly after 10 minutes. Use handheld trial lenses (±0.25D) to modify the lens power. A 0.25D change may significantly improve vision for many patients.
If distance vision is not acceptable, consider these changes:
- If low add lenses, add 0.25D to the dominant eye
- If high add lenses, add 0.25D to the dominant eye, or use a low add in the dominant eye and a high add in the non-dominant eye
If your patient has near vision difficulties, try these changes:
- If low add lenses, use modified monovision and add +0.25D to +0.50D to the non-dominant eye
- Use a low add lens in the dominant eye and a high add in the non-dominant eye
- High add lenses OU
If the patient complains of variable vision and visual clarity fluctuates with a blink, you may need to change the base curve from 8.8mm to 8.5mm.
Success with multifocals depends on good patient selection, patient education and practitioner skill. A skilled clinician knows the product and gains experience by fitting many patients.
TABLE 1: SofLens Multifocal Lens Parameters
|POWER||+6.00D to 10.00D|
Low add (up to +1.50D)
High add (+1.75D to +2.50D)
|BASE CURVE||8.5mm and 8.8mm|
|CENTER THICKNESS||0.10mm (3.00D)|
Dr. Ghormley is in private practice in St. Louis, MO. He is a past president of the American Academy of Optometry and a Diplomate of its Cornea & Contact Lens Section. He is also the team optometrist for the St. Louis Rams (NFL) and the St. Louis Blues (NHL).