GP Lens Case Grand Rounds Troubleshooting Guide

Segmented Design with Intermediate Correction: Tiffany J. Johnson, OD & Vinita A. Henry, OD, FAAO

Background

LM was a 46-year-old, long-term GP wearer (10+ years). She had successfully worn spherical GP’s for myopia for most of her younger adult life. She was currently wearing the X-Cel Solution bifocal, OU, and had been wearing that design for the past 2 and a half years. LM presented with a chief complaint of decreased lens wear due to the lenses popping out (OD > OS). The patient had a secondary complaint of poor intermediate vision.

Test Procedures, Fitting/Refitting, Design and Ordering

Entrance Visual Acuities (with Current Lenses):

OD: 20/20 Distance and Near
OS: 20/20 Distance and Near

Current Lens Parameters:

OD: -4.25/+2.00Add 8.0BC, 9.6 Diam
OS: -5.00/+2.00Add 7.9 BC, 9.6 Diam

Slit Lamp Evaluation (with Lenses):

Both lenses translated well. The lower edge of the right lens occasionally caught the lower lid creating the potential for the lens to be dislodged.

Manifest Refraction:

OD: -5.50 – 0.75 x 180; 20/20
OS: -5.25 – 1.25 x 180; 20/20

Keratometry:

OD: 42.25 @ 180; 44.75 @ 090 (mires clear)
OS: 42.25 @ 180; 45.62 @ 090 (mires clear)

Refitting Information:

The Essential Solution lenses were trialed to see if the aspheric front surface would possibly help the patient achieve more intermediate vision.

The Following Lenses Were Trialed:

Slit Lamp Evaluation (with Lenses):

Good movement with translation, centration, and fit, with the segment sitting 1 mm below pupil was noted, OU. Patient was able to see 20/20 at distance, intermediate, and near with the following over-refraction.

Over-Refraction:

OD: -2.00DS; 20/20
OS: -1.50DS; 20/20

The Following Lenses Were Ordered for the Patient:

Essential Solution (X-Cel):
OD: -5.00/+2.00D Add 7.80 base curve radius; 9.60 overall diameter
OS: -4.50/+2.00D Add 8.00 base curve radius; 9.60 overall diameter
Plus lenticular, segment height 1 mm below GC, OU; medium prism

Typically, segmented bifocal lenses are fit slightly flatter than “K” to allow the anterior center of gravity to shift these lenses inferiorly. However, as a result of the aspheric nature of the back surface of this design (the front surface is a segmented crescent bifocal), it is often fit slightly steeper than “K.” It is still desirable for these lenses to position at or near the lower pupil margin to assist in translation with downward gaze for reading.

As the right lens of her previous had been ejecting quickly, it was decided to steepen this lens. It would have been predicted that a higher minus power lens would be ordered for the right eye but the over-refraction indicated otherwise.

Patient Consultation and Education

The key factor with this patient was ensuring a good fit and meeting the patient’s visual demands. The patient had been a successful contact lens wearer and we wanted her to remain satisfied with her contact lenses.

Visual Acuities (with the New Lenses):

The patient was very satisfied with the fit and vision of the new lenses.

Follow-Up Care/Final Outcome

With LM, steepening the base curve radius of the right lens solved the problem of the poor fit and the lens trying to pop out of the eye. The base curve of the left lens was left alone. In addition to this, we tried a different lens design (aspheric translating design) to improve the intermediate vision and it was very successful.

The patient was evaluated for a follow-up visit after wearing the lenses for two weeks and she remained very satisfied with all ranges of vision with no change in the fitting relationship or vision. Subsequent visits since that time have also provided the same positive results.

Discussion, Alternative Management Options

Lens displacement from the eye is often caused by too flat of a lens fit, which is remedied by steepening either the base curve radius or peripheral curves (1). In this case, the primary problem appeared to be with the right eye, so we steepened the base curve radius of that lens.

The X-Cel Solutions lens is a translating segmented lens (2,3). The lenses were translating well and the patient was obtaining good vision at distance and near but was having difficulty achieving good vision in the intermediate range.

By trying the Essential Solution segmented aspheric multifocal, the patient was able to see better at intermediate distances due to the aspheric back surface, but still achieve sharp near vision through the translating segmented near portion. There are several other lens modalities that could have been utilized had the patient not been a good translating bifocal candidate.

Certainly, there are a number of translating multifocals that provide good intermediate vision from CLMA member laboratories including Llevations and Solitaire II (Tru-Form Optics; EZ Eyes (ABBA Optical); Presbylite II (Lens Dynamics) and Tangent Streak Trifocal (Fused Kontacts of Missouri).

Bibliography

1. Bennett ES, Hansen D. Presbyopia: Gas Permeable Bifocal Fitting and Problem Solving. In Bennett ES, Hom MM. Manual of Gas Permeable Contact Lenses (2nd ed.). Elsevier Science, St. Louis, MO, 2004:324-356.
2. Gromacki SJ. Preventing Contact Lens Challenges for Presbyopes. Contact Lens Spectrum: Aug 2004.
3. Norman CW. Combining Simultaneous and Alternating Vision GP Concepts. Contact Lens Spectrum: May 2003.

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