Relief in Sight for Astigmatic Presbyopes

BY MICHAEL B. SHAPIRO, M.D., & DOUGLAS C. BREDESON, C.O.T.
MAR. 1996

Would a toric soft multifocal provide acceptable correction for astigmatic presbyopes? This new lens demonstrates promising results.

By the year 2000, more than 60 percent of the population in the United States will be presbyopic. Until now, the only contact lens options an astigmatic presbyope had were rigid gas permeable lenses in a bifocal or multifocal design, monovision in either rigid gas permeable or toric soft lenses, or single-vision contact lenses and reading glasses. The Horizon 55 Bi-Con toric multifocal contact lens, manufactured by Westcon Contact Lens Co., Inc., is the first hydrophilic toric multifocal lens available in the United States.

To evaluate this new lens, we fit 15 presbyopic patients over three months to determine if a soft toric multifocal contact lens would be successful for presbyopes with higher astigmatism. Comfort, acceptable visual acuity at distance, intermediate and near, and the lack of physiologic problems were all factors in our clinical investigation. We also evaluated chair time and the number of lens exchanges required to achieve a satisfactory fit. We charged all patients the customary fee for multifocal contact lens fitting with no incentives provided for participating in the evaluation.

Of the 15 patients fit with the Horizon 55 Bi-Con multifocal lens, 12 are still wearing the lens, which indicates an initial acceptance rate of 80 percent.

MATERIALS AND METHODS

The Horizon 55 is a toric bifocal lens with a spherical front surface to correct visual acuity in presbyopic patients who are myopic or hyperopic. The posterior surface is toric to correct vision in an astigmatic eye. The lens has a double slab-off flange ballast stability feature so that the toricity remains in the proper axis. The lens is designed and fabricated with a zonal blend between the centrally positioned segment (center add) and the surrounding distance power zone. Since this is a high water content lens, the manufacturer recommends chemical or hydrogen peroxide disinfection. Table 1 lists fitting parameters, distance powers and reading add powers.

TABLE 1: HORIZON 55 BI-CON TORIC DATA* Material Methafilcon A Water content 55 percent Base curves 8.3; 8.6; 8.9 Sphere power -10.00 to +10.00 (increments of 0.25 diopters) Cylinder power -0.75 to -5.00 (increments of 0.25 diopters) Add power +1.00 to +3.00 (increments of 0.50 diopters) Optical zone, 2.0mm, 2.5mm central near Central thickness (low minus) 0.14mm (plus lens) up to 0.37mm Diameter 14.5mm Design Lathe cut, back toric double slab-off Simultaneous, concentric Central near *Custom parameters are also available

We evaluated and fit 15 patients with the Horizon toric multifocal. Astigmatic presybopes who had never worn contact lenses or who were RGP-intolerant were included in the study. Patients had a refractive error between +7.00 and -9.00 diopters of spherical power and between -1.00 and -4.00 diopters of refractive cylinder. They required additions between +1.00 and +3.00 (Table 2). Patients otherwise had a completely normal ophthalmologic exam with no objective contraindications to soft contact lens wear.

TABLE 2: PATIENT DATA No. of patients 15 Female 13 Male 2 Age 40-65 year Myopes 9 Hyperopes 6 Previous cl experience 13 Keratometric range 40.00 to 47.00 Sphere power range +6.75 to -8.25 Refractive astigmatism range -1.00 to -3.50 Add power range +1.25 to +2.75

After fitting and evaluating our first three patients, we reviewed the results and decided to fit the remaining patients empirically. The study consisted of four visits.

During visit number one, we measured distance acuity with and without correction with the

Snellen chart at 20 feet. Next, we measured near visual acuity at 14 inches and 28 inches using a Rosenbaum pocket vision screener and obtained each patient's best corrected distance and near vision. We then performed a slit lamp exam, keratometry readings, rechecked manifest refraction and measured pupil size in standard illumination. After documenting these measurements, we either fit the patient with trial lenses or ordered the lenses empirically.

At visit two, we evaluated fit and visual acuity. After inserting the lenses, we allowed them to equilibrate 20 minutes. We repeated the visual acuity tests, and then did an overrefraction of the contact lenses using hand-held trial lenses in standard illumination. (Note: When overrefracting any simultaneous vision multifocal, maintaining a normal pupil size is critical. Abnormal lighting or use of a phoropter can alter pupil size, resulting in a false overrefraction).

Slit lamp examination confirmed a proper lens-to-cornea relationship. We reviewed proper lens care and handling with all patients, and dispensed Bausch & Lomb's ReNu multipurpose care kits unless contraindicated. We scheduled a two-week follow-up visit and instructed the patients to call if they had questions or problems.

Visit three was our routine two-week follow-up for any new multifocal contact lens patients. We measured distance and near visual acuity, did an overrefraction with hand-held trial lenses in standard room lighting, slit lamp biomicroscopy and keratometry readings. We ordered lens changes as necessary or scheduled a six-week follow-up. At visit four we repeated all previously performed measurements.

RESULTS

After six months, 12 of the 15 patients are still wearing their Horizon 55 Bi-Con lenses on a daily basis. Two of the three study dropouts achieved good visual acuity and comfort with the lens (Table 3).

TABLE 3: VISUAL ACUITY Distance VA No. of patients
20/20 OU	12
20/25 OU	1
20/30 OU	1
20/40 OU	1
Near VA at 14 inches	No. of patients
J-1+ OU	11
J-1 OU	3
J-2 OU	1
Intermediate VA at 28 inches	No. of patients
J-1 OU	2
J-2 OU	9
J-3 OU	4

Of the three dropouts, one patient had never worn soft contact lenses before and found them too difficult to insert. The second was a younger (41) hyperopic woman who, during her initial eye exam, complained of near visual acuity problems with her single-vision spectacles. She did equally well with single-vision and multifocal toric contact lenses objectively at near and distance; however, subjectively she preferred the single-vision soft toric lenses. The third patient never achieved good distance visual acuity with the toric multifocal and is wearing bifocal spectacles.

Although concentric in design, the Horizon lens subjectively met the intermediate needs of the 12 successful patients. All patients tolerated the lens well and developed no anterior segment abnormalities.

We used an average of three lenses per patient to achieve a satisfactory fit. We replaced only two lenses due to tearing or loss, and found that lens duplication was not a problem.

DISCUSSION

Based on our preliminary results with the Horizon 55 Bi-Con multifocal, we feel that the lens will meet the needs of a select group of patients in the presbyopic market. It effectively provides the same comfort and stable visual acuity of a single-vision soft toric lens as well as subjectively good near and intermediate vision using concentric design, simultaneous vision optics.

Our preliminary evaluation showed a success rate of 80 percent. The lens demonstrated positive results in light of a difficult fitting situation and complicated optics. Although the Horizon toric multifocal may not be the lens of choice for every astigmatic presbyope, we believe the lens will be useful for patients who can't wear rigid gas permeable lenses (for example, patients who live in poor environmental conditions, patients who are poorly motivated, patients who want contact lenses for intermittent wear, and athletes). Emerging presbyopes wearing single-vision soft toric contact lenses are also good candidates for the Westcon Horizon 55 Bi-Con multifocal lens. CLS

Dr. Shapiro is a corneal specialist with Davis Duehr Dean Eye Associates in Madison, Wisc. He is involved in corneal, cataract and refractive surgery.

Mr. Bredeson is a contact lens specialist at Davis Duehr Dean Eye Associates. He assists Dr. Shapiro in clinic.

Dr. Shapiro and Mr. Bredeson have no financial interest in Westcon Contact Lens Co., Inc.

References are available upon written request to Contact Lens Spectrum; to receive references via fax, call (800) 239-4684 and enter Document #11. (Be sure to have a fax number ready.)