GP Lens Case Grand Rounds Troubleshooting Guide

Post-Penetrating Keratoplasty due to Fuch’s Dystrophy: Intralimbal Lens Correction: Bruce W. Anderson, OD, FAAO

Background

A 79-year-old female (RL) presented for a contact lens fitting for her right eye. RL had a history of a corneal transplant in the right eye secondary to Fuch’s Dystrophy. RL’s vision in this eye at distance with her current glasses, was 20/80⁺². She had never worn contact lenses previously. She did not report any significant health problems. She was not taking any medications and was allergic to sulfa, codeine and Feldene.

Test Procedures, Fitting/Refitting, Design & Ordering

Manifest Refraction (very variable without a definite end point)/Visual Acuity:

OD:   pl – 5.00 x 027      20/80-

Slit Lamp Evaluation: The slit lamp evaluation revealed a deep and clear anterior chamber. The conjunctiva was white. The central cornea was clear and revealed a well-healed and stable corneal transplant. The host / donor interface was flat without significant plateauing. There were no sutures still in place. There was a clear posterior chamber intraocular lens (IOL) in place. Corneal topography was performed is shown below.

Diagnostic fitting:

Due to the significant central distortion and astigmatism, it was decided to fit her into a GP lens. With the aid of the information from the topography, she was fit into a Dyna Intralimbal design. The initial diagnostic contact lens placed on her eye had a prescription of:

Over-Refraction/Visual Acuity: 

OD:  -0.25DS  20/30

Slit Lamp Evaluation:

Good centration with 0.5mm movement with the blink was present. There was slight central touch with fluorescein application. There was minimal edge lift peripherally. 

The following Dyna Intralimbal design was ordered:

Contact lens ordered:

The initial contact lens was dispensed on March 10, 2009. 

Visual Acuity: 

OD:  20/40+

Slit Lamp Evaluation: The contact lens did not move excessively and decentered slightly nasally. Mild apical touch was also present.

The lens was dispensed at this visit with a wearing schedule beginning at two hours the first day and increasing by one hour a day. A follow-up visit was scheduled for one week. 

Follow-Up Care/Final Outcome

One Week Follow-Up Visit

At this visit the patient stated that she was doing very well. She currently had the lens on the eye for two hours at this visit, and had worn the lens for a maximum of eight hours. 

Visual Acuity/Over-Refraction:

OD: 20/40⁺²   (variable: Plano to +0.50D)

Slit Lamp Evaluation: The contact lens exhibited approximately 0.25mm movement with the blink and decentered slightly nasally. There was no significant corneal staining or irritation secondary to the wearing of the lens. 

One Month Follow-Up Visit

At this visit, she stated that she was doing extremely well and was now wearing the lens all day.   

Visual Acuity/Over-Refraction:

OD: 20/30^-1   (variable: Plano to +0.25D)

Slit Lamp Evaluation: The contact lens exhibited approximately 0.25 – 0.50mm movement with the blink and decentered slightly nasally. There was no significant corneal staining or irritation secondary to the wearing of the lens. 

The final assessment is that she was doing very well and the fit was stable. She was discharged for one year with follow-up with her anterior segment specialist back north in six months (she was a seasonal resident of our state). 

Discussion/Alternative Management Options

In an attempt to correct this astigmatism, one needs to review the corneal topography and evaluate the condition of the eye and determine what lens design may be most successful. With evaluation of the corneal topography, it is noted that the astigmatism is located more centrally than peripherally. The astigmatism is located primarily within the graft region. However, there is a nasal drop-off. From this I would expect the lens to shift nasally. By using a large diameter lens, the lens was able to vault over the central cornea and hold to the peripheral cornea to keep the lens in place. This would also make the lens more comfortable and easier to adapt to wearing.  Also from the corneal topography, there is a flatter region at approximately 180º on the cornea. There were concerns that the lens would bear in this area and cause irritation. Because of the drop-off nasally and flat region temporally, the initial contact lens used for evaluating the fit was based on the flatter end of the curvature spectrum based on the corneal curvature. The “sim Ks” were 40.07 @ 018; 55.57D @ 108. With this drop-off nasally, a slightly steeper lens could vault over some of these areas and align with the peripheral cornea. The initial diagnostic lens had a base curve radius of 45.00D and 11.2 diameter. The diagnostic lens fit very well on the eye; however, it was slightly tight, and thus, the use of a slightly flatter peripheral curve and slightly flatter base curve radius was necessitated. Once the contact lens was worn, the lens was decentering slightly nasally. This is due to the steeper region nasally, which allows the lens to slide in the nasal direction. There was slight bearing of the peripheral curve at the 180º flat region; however, this did not prove to be a problem during the wearing of the lens. This was evaluated during each follow-up visit. Fortunately, even though RL did not have a history of wearing contact lenses previously, she adapted to the lens quickly. She performed extremely well with the wearing of the lens and was very determined to be successful. She was discharged from immediate follow-up care and was scheduled to return in one year.

Using larger diameter lenses such as this, you can vault over the central cornea. Many times, you may be able to ignore the measured astigmatism in the central region, even if it appears to be significant. The topography of the peripheral cornea can be evaluated to determine how far the toricity extends. If the astigmatism is central, a large diameter spherical lens may be the best option. The peripheral curves and edge of the lens are used to stabilize and hold the lens in place. Another important decision is the material to be used. With corneal transplants, you do not want to cause irritation to the eye due to insufficient oxygen transmission. You should use the highest DK material available with any particular design. The design must be stable with any material and not flex. Some of my preferred materials include Menicon Z (Menicon) and Boston XO2 (Bausch + Lomb). 

Other lens designs that may have been used to fit this patient could be a mini-scleral or full scleral lens. These larger designs would have the same benefit of the intralimbal in covering the central astigmatic cornea as well as possible additional comfort from the larger design. If this patient could not adapt to the intralimbal, these larger lenses would be an excellent next choice.

The final fitting pearls that may be taken from fitting this cornea:

1.  Use topography to evaluate corneal astigmatism and irregularity and realize that many times, the astigmatism that is measured is only central and not peripheral. If this is the case a large diameter lens will usually be successful.
2. Think large.  The larger diameter lenses hold more stably on the eyes, keep their position better, move less and cause less lens awareness.  Large diameter lens will fit up under the upper lid and create a more comfortable fit.
3. Use high permeable and stable materials to prevent a hypoxic situation that could aggravate a corneal transplant.

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