GP Lens Case Grand Rounds Troubleshooting Guide – 04

Soft Toric Lens Failure – Poor Vision: Phyllis Rakow, COMT, NCLE-AC, FCLSA(H)

Background

RG, a 44 year old female presented with a history of poor vision with soft spherical and toric lenses.over a 14 year period. She had tried four different soft toric designs prior to her visit, but was unable to achieve rotational stability with any of them.

Manifest Refraction:

OD -3.00 -1.50 X 105 20/25+
OS -3.50 -2.50 X 090 20/20-

Keratometry Readings:

OD 46.37 @ 155/47.00 @ 065
OS 46.37 @ 180/45.87@ 090

Original keratometry readings from 14 years previous were:

OD 45.00/44.75 (no axis indicated)
OS 45.25/44.75 (no axis indicated)

Slit Lamp Examination:

Neovascularization inferonasally OU; no visible corneal edema, but hypoxia due to lens overwear suspected.

Patient Consultation and Education

This patient was advised to discontinue soft lens wear and return for a GP fitting in two weeks. RG was told that the steepness of her corneas precluded successful soft toric fitting with stable visual acuity at this point in time. Advantages of GP lens wear, especially the increased oxygen transmission and better visual acuity were discussed. At the follow-up visit, new keratometry readings and manifest refraction were performed. Residual astigmatism and the need for a special front toric design for the left eye were explained to the patient.

Manifest Refraction:

OD -3.00 -0.75 X 105
OS -2.25 -1.50 X0 90

Keratometry:

OD 45.37 @ 175/46.12 @ 085
OS 45.37 @ 090/45.62 @ 180

Lenses Ordered:

BCR (mm)Power (D)OAD (mm)Material

OD 7.50 -2.75 9.6 Boston ES
OS 7.55 -2.00 -1.00 X 90 9.6 Boston ES

Dispensing Visit

Visual Acuity:

OD 20/20 with effort
OS 20/20

Slit Lamp Examination:

Lid attachment and alignment with fluorescein OU

Follow-Up Care/Final Outcome

The lenses were dispensed with the Boston Advance cleaner and the Boston Original Conditioning solution. RG adapted rapidly and appreciated the crisp acuity with her new GPs. Initially, she still had enough accommodation to read with her contact lenses, but over time, she purchased drugstore reading glasses. Three years after her GP refit, we suggested trying multifocal GPs.

Manifest Refraction:

OD -2.50 -1.25 X 95
OS -1.75 -0.25 X 88
Add +2.25 OU

Keratometry Readings:

OD: 45.25@90º/45.62@180º
OS: 45.62@90º/45.62@180º

The near-spherical refraction of RG’s left eye surprised us, and made the fitting of multifocal GP lenses much simpler. RG was fit with Art Optical Magniclear Plus front surface multifocals. These lenses are fit conventionally and combine the principle of simultaneous vision for distance and intermediate with that of translation for near vision. They have a low negative eccentricity 7.0 mm distance zone and a spherical near zone that is controlled independently of the distance/intermediate zones with no image jump.

This fitter has found that most patients require a significantly greater add power with these lenses than they have in their spectacles.

Lenses Ordered for RG:

Magniclear Plus

BCR (mm)Power (D)OAD (mm)Add (D)Material

OD 7.50 -2.25 9.5 +3.75 Boston EO = 20/20 J2
OS 7.50 -2.50 9.5 +3.75 Boston EO = 20/20 J2

Discussion, Alternative Management Options

Some fitters hesitate to recommend GP lenses to mature adults because they think they will not be able to adapt to a rigid material at this point in life. By leaving these patients in soft lenses, both visual acuity and corneal health are compromised. Placing a diagnostic GP lens on astigmatic patients’ eyes will often achieve a “WOW” factor when they realize how sharp and stable their vision is. Patients with keratometry values greater than 45.00D in both principal meridians are often unable to achieve rotational stability with soft toric lenses. Many of these patients, if they have worn soft toric lenses (especially low-water-content torics) in the past, will also show signs of corneal hypoxia, including neovascularization and even corneal ectasias that resemble early keratoconus under the base of the prism.

As astigmatic patients enter their presbyopic years they will find soft lens options even more limited. A multitude of excellent GP multifocal lenses are available in anterior and posterior surface designs. Some of the posterior surface designs allow fitters to incorporate an additional concentric zone of add power on the anterior surface of the lenses for mature presbyopes. As most patients today spend time at a computer, this fitter prefers using a multifocal GP to an alternating vision bifocal design whenever possible.

We explain to our patients that their entire multifocal prescription is compressed into less than 9.5 mm of space, including the bevels, and that they might occasionally need to use a pair of low-power “booster glasses” to see very tiny print. Surprisingly few GP wearers actually need this supplementary power compared with soft lens multifocal wearers, but it does emphasize that patients need to have realistic expectations about presbyopic contact lens correction.

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