GP Lens Case Grand Rounds Troubleshooting Guide

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Keratoconus and Presbyopia – addressing full patient needs: S. Barry Eiden OD, FAAO, FSLS


A 53-year-old male was managed for keratoconus and presbyopic symptoms. The patient initially presented at age 45 with a prior history of keratoconus and corneal GP wear (first diagnosed at age 33). At initial presentation the patient was wearing flat fitting / apical bearing corneal GPs:

Design: McGuire Oval OU

OD: BC 7.10/8.6 TD
OS: BC 7.20/8.6 TD

Biomicroscopy revealed a bilateral central stromal scar +2-3 and associated apical epithelial staining +2 OU. Scheimpflug corneal tomography revealed a fairly well centered oval keratoconus pattern on axial curvature maps OU. There was classically keratoconic posterior elevation abnormalities that were greater than the anterior elevation abnormalities (anterior apical elevation OD 39 microns, OS 34 microns and posterior apical elevation OD 89 microns, OS 87 microns). The thin point on each cornea was OD 395 microns and OS 425 microns. Anterior corneal eccentricity was highly prolate (OD e= 1.18, OS e= 1.35). Scheimpflug imaging revealed bilateral anterior stromal scaring.

Fig 1. Scheimpflug Tomography Right Eye

Fig 2. Scheimpflug Image Right Eye: demonstrating apical corneal scar

Fig 3. Scheimpflug Tomography Left Eye

Fig 4. Scheimpflug Image Left Eye: demonstrating apical scar

Initial manifest refraction was:

OD: -17.00 – 5.50 x 30 Aa: 20/50
OS: -18.50 – 4.75 x 105 VA: 20/40

Initial keratometry values were:

OD: 50.62/53.62 with +3 distortion
OS: 52.37/53.87 with +2-3 distortion

Contact Lens Management

Initial refitting was made into a “Dyna Z Cone” design (ABB Optical Group)

OD: BC 6.7/ 8.8 TD with +1 steep periphery 360 degrees / power -15.00 Va: 20/25+

OS: BC 6.65/ 8.8 TD with +2 steep periphery and localized +3 steep along the 270 degree meridian to account for inferior edge standoff / power -16.25 VA: 20/20-

Fitting characteristics were symmetric demonstrating an interpalpebral positioning with mild inferior central vertical location upon settling and excellent lateral centration. There was mild apical clearance over the cone apex and appropriate alignment of the lenses in the mid peripheral areas OU. There was appropriate edge clearance with mildly greater degree along the inferior lens section (however, no edge standoff). Movement with blink was adequate OU.

Fig 5. Example of a GP lens with symmetric peripheral edge lift demonstrating inferior edge standoff and the elimination of inferior edge standoff with the use of asymmetric peripheral geometry.

The patient was able to wear these lenses with excellent comfort and maximum wearing time of 16 hours daily with clear vision until age 52+ when the patient reported noticeable reduction of near vision. Near acuity was at this point in time 20/40+ with contact lenses and required an add of +1.25D for each eye to achieve clear near vision. Biomicroscopy was stable with no progression of scarring and no evidence of apical corneal staining for either eye.

Although the patient could easily have used reading glasses over the contact lenses he desired contact lens alternatives to address his presbyopia. These would include:

  1. Monovision contact lens powers (rejected by the patient)
  2. Multifocal contact lens options:
    • a. Posterior Aspheric Custom Multifocal Design (good for central cones)
    • b. Anterior Concentric Custom Multifocal Design (or combination designs) (with posterior keratoconus design configuration)
    • c. Anterior Aspheric Custom Multifocal Design (with posterior keratoconus design configuration)

We decided to design an anterior aspheric element to the current corneal GP design:

Dyna Z Cone with Front Aspheric Multifocal using the same fitting parameters as his habitual contact lens with the implementation of a front aspheric curvature within the optic zone (e = 0.90 ) which creates an effective add of approximately +1.25 D. There was no change in DVA; however, near acuity improved to 20/20- for each eye and intermediate acuity was also improved to 20/20.

Patient Education and Consultation

This is a wonderful case that addresses a number of key points in keratoconus contact lens management. First is the importance of avoiding bearing of corneal GPs on the apex of the cone. In this case there was likely progressive scarring induced by the apical bearing of his original McGuire Oval corneal GPs OU. A refit into a design that is able to achieve apical cone clearance appeared to result in no progression of scarring after refitting. The second point relates to the use of asymmetric peripheral geometry designs to better contour the corneal surface in keratoconus. It is most common to observe greater inferior curvature in keratoconus compared to other geometries. This often results in lenses that have inferior edge standoff of the cornea. This is typically associated with poorer comfort and lenses that have a tendency to dislocate and “pop-off” of the eye. Today we have the ability from many laboratories to design asymmetric peripheral geometries. As such we can design a lens that is steeper along the inferior meridians in order to properly contour the cornea for 360 degrees. The third element of this case pertains to presbyopia. Keratoconic patients are no different than our other contact lens wearing patients in that they often prefer contact lens alternatives rather than over-glasses for near vision to address their presbyopic symptoms. There are numerous ways to achieve this, both in terms of monovision and multifocal design options. Although you are adding multifocal optics to an already challenging optical system in keratoconus, they often are highly effective, especially when using corneal GP lens designs.

Concluding Remarks

When managing keratoconic patients with contact lenses it is incumbent upon the ECP to address the physiological requirements of optimized lens physical fitting along with the optical demands. Typically optimizing distance vision is paramount; however, addressing near vision in presbyopia often is also highly desirable. Utilizing the array of multifocal GP lens designs we have in our armamentarium can be the difference between a happy patient and an ecstatic patient!

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