GP Lens Case Grand Rounds Troubleshooting Guide – 51

Intermediate Myopia (1.75 – 3.0D): John Rinehart, OD

Background

A 38 year old female presented with a 15 year history of wearing soft contact lenses. She felt her vision was clear both near and distance but lens comfort had decreased. Her lens care products include AO Sept and Pliagel. She was concerned that her correction had increased over the past five years from OD: -1.00D to -1.75D and OS -1.25D to -2.00 D. The progression of her myopia is the reason it was determined that corneal reshaping was her best option for her.

Test Procedures, Fitting/Refitting, Design & Ordering

Visual Acuity with Current Soft Lenses:

OD: 20/20
OS: 20/20

Unaided Distance Visual Acuity:

OD: 20/80
OS: 20/80

Manifest Refraction:

OD: -1.50 -0.50 x 095 20/20
OS: -2.00 DS 20/20

Keratometry Readings:

OD: 43.75 @ 180; 43.75 @ 090 no distortion
OS: 44.00DS no distortion

Prefit corneal topography shows the values of OD .79 OS .80 in the flat meridian.

Diagnostic fitting was performed using the R & R Lens Design. Danker Laboratories of Sarasota, FL fabricated the lenses. On the open eye (OD) the diagnostic lens with an alignment curve (AC) radius of 7.9mm was considered loose and the lens with an AC of 7.76mm was considered slightly snug on the open eye trial. The diagnostic fitting on the left eye showed the AC of 7.85mm was slightly loose and the AC of 7.76mm was slightly snug. The initial alignment curve radius for both left and right was 7.80 mm. Lens diameter of 10.0 mm OU and a base curve of 8.18 mm OU were chosen for the lenses.

At the time of lens dispensing the patient was instructed to put the lenses on 15 minutes before going to bed and upon rising to lubricate the lenses with reconditioning solution and remove 10-15 minutes later. The lenses were prescribed for overnight wear only. After one night of lens wear the patient’s unaided visual acuity was 20/20 with each eye.

Keratometry Readings:

41.50 @ 180; 42.00 @ 090 OU

Manifest Refraction:

OD: +0.25 DS 20/20
OS: +0.50 DS 20/20

Corneal Topography of both eyes was very similar to that of the right eye.

The corneal topography shows a very clear smiley face which indicates that the sagittal depth of the lens is too low. At this time the patient should have been refit, but wasn’t. As visual acuity, refraction and keratometry readings were so good the patient was not refit and instructed to return in 10 days.

Follow-Up Care/Final Outcome

At the 10 day visit the patient’s unaided acuity was OD 20/40 OS 20/30.

Manifest Refraction:

OD: +1.50 -1.75 X 065 20/20
OS: +1.75 -1.25 x 125 20/20

Keratometry Readings:

OD 42.50 @ 180; 43.00 @ 090
OS 42.50 @ 180; 44.00 @090

Topography (below) again shows a distinct smiley face.

This time the patient was refit with an alignment curve of 7.76 mm OU and the overall diameter was increased from 10.0 mm to 10.6 mm. Theses changes increased the sagittal depth of the lenses by 9.0 microns.

At the one and two month visits the patient’s subjective refraction was OD +0.25 D OS plano sphere and +0.75 D OD, OS respectively.

Keratometry Readings:

42.75DS OU

Unaided visual acuity: OD 20/20 OS 20/20

The best outcome was delayed due to the fact that the patient was not refit after the first night of lens wear. Stable clear vision should have been achieved by one week but failing to refit in a timely fashion delayed this to one month of lens wear. The patient currently wears her lenses 4-5 nights per week and is able to maintain clear comfortable 20/20 acuity for up to 36-40 hours without lens wear.

Discussion/Alternative Management Options

The clinical pearls here are determine the success of the lens fit by the appearance of the difference maps and not refraction and K readings. The other pearl is that refitting soft lens wearers into GP corneal reshaping lenses can be a simple straightforward procedure that provides the patient with clear comfortable vision without the need for any appliance during their waking hours.

This patient could have also been fit with traditional GP lenses and one would expect that the progression of her myopia would have ceased. She did however appreciate her lack of dependence on corrective appliances during her waking hours.

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