GP Lens Case Grand Rounds Troubleshooting Guide – 45

Post-Hyperopic LASIK: Michael Ward, OD

Background

A 46 year old male complained of poor visual acuity and decreasing vision from his right eye and desires a contact lens for that eye only. Thirteen months prior to this visit he had underwent hyperopic LASIK surgery for the right eye as a result of his emerging presbyopia. There was no record of his pre-operative prescription. He reported that his vision was good immediately following the surgery.

His contact lens history included successful wear of soft lenses prior to the surgery. He stated that he had attempted soft toric and gas permeable (GP) lens wear without success during the past six months.

Test Procedures, Fitting/Refitting, Design & Ordering

Visual Acuity (without Correction):

OD: 20/200
OS: 20/20-1

Manifest Refraction:

OD: +3.00 -3.00 X 085 20/80-1
OS: +0.75 -0.25 X 138 20/20

Manual Keratometry:
OD: 46.7 @ 134; 43.0 @ 44 2+ mire distortion
OS: 43.6 @ 156; 44.2 @ 66 crisp mires

Corneal Topography:


Indicates keratectasia

Slit Lamp Examination:

OD: central and paracentral haze, vertical striae and thinned; nasal based flap with horseshoe shaped microkeratome scar noted
OS: cornea clear

Contact Lens Diagnostic Fitting:

Initial diagnostic lens
Design Surgical C4
Base curve 40.42D
Diameter 10.0mm

Manifest refraction over contact lens: +2.50DS 20/25+2

Initial diagnostic lens selection was based on a combination of keratometry readings, topography maps and fluorescein patterns. This type of lens fitting is similar to fitting keratoconus (see map). It is not recommended in these cases to fit the apex of the ectatic protrusion. The base curve radius is often fit somewhat flatter than “K”, but not as flat as the superior corneal topography. The overall diameter is slightly larger than normal to increase centration; larger diameters may be beneficial. The fluorescein pattern should show complete tear exchange over the entire corneal surface with each blink.

Contact Lens Order:

Laboratory: ABBA
Material: Fluoroperm 60
Base Curve Radius (BCR): 41.00D
Overall/Optical Zone Diameter (OAD/OZD):10.0/9.0mm
Power: +2.50D
Center Thickness: 0.23mm

Patient Consultation and Education

The lens was dispensed with proper instruction, a gradually increasing wearing schedule and Boston Advance Cleaner and Conditioning Solution.

Follow-Up Care/Final Outcome

At the one week follow-up visit, the patient’s vision was unchanged and he was adjusting well to GP lens wear and enjoying both his vision and depth perception. He was ultimately successful with this design.

Discussion/Alternative Management Options

Contact lenses offer an option to visually rehabilitate patients when refractive surgery results are less than desired. Rigid lenses have traditionally been used to correct irregular corneal astigmatisms following penetrating keratoplasty, phototherapeutic keratectomy (PTK), traumatic scarring and corneal ectasias. Gas permeable (GP) contact lenses can improve the visual performance of eyes with irregular corneal surfaces by providing a smooth, regular, anterior refractive surface to the eye. Tears fill the spaces between the posterior surface of the contact lens and the irregular anterior corneal surface, creating an optical bridge and minimizing the light scattering effects of the irregular corneal surface. This same technique can be used to rehabilitate patients with irregular corneal topographies following refractive surgeries or trauma. Mild ametropias may be adequately corrected with soft hydrogel or silicone hydrogel lenses, but are inadequate for correcting irregular astigmatism.

This patient had originally sought surgical monovision correction. He was offered monovision contact lens correction, but after his unexpected surgical result, he decided to seek his best corrected overall vision and use reading glasses for near correction. An alternative would be to use a multifocal GP lens. This is not an optimal choice since multifocal correction relies on good lens centration, which is often difficult following refractive surgery. Fortunately, we have GP options to correct post-surgical irregular astigmatism. This patient is quite satisfied and enjoying his quality of vision.

Supplemental Reading

    1. Ward MA. Visual rehabilitation with contact lenses after Laser in situ Keratomileusis. J Refractive Surgery 2001;17:433-440.
    2. Yeung KK, Olson MD, Weissman BA. Complexity of contact lens fitting after refractive surgery. Am J Ophthalmol 2002;133(5):607-612.
    3. Ward MA. Contact lens management following corneal refractive surgery. Ophthalmol Clin N Am 2003; 16: 395-403.

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