CASE STUDY I - Dr. Quinn

Hx: 22-year-old waitress interested in contact lenses

Refraction:
     OD -1.00 - 3.00 x 180
     OS -2.00 - 2.25 x 175

K's:
     OD 41.00 @ 180; 44.00 @ 090
     OS 43.00 @ 175; 45.00 @ 085

Treatment options:
     1. Toric soft contact lenses
     2. Spherical GP lenses
     3. Toric GP lenses

Diagnostic lens applied OD:
     Base curve: 8.03mm (42.00 D)
     OAD/OZ: 9.2/7.8
     Power: -2.00
     ct: .16

Spherical diagnostic lens demonstrates poor centration; therefore elected to pursue toric GP fit. Where to start?

All maintain a 0.75 difference in fitting relationship between horizontal and vertical meridians to mimic fitting the "ideal" cornea.

Order:
     BC: 41.00 (8.23mm)/43.25 (7.80mm)
     BVP: -1.00/-3.25
     Difference in base curve (D): 2.25 D
     Difference in lens powers: 2.25 D

Conclusion: Spherical Power Effect (SPE) Design

• Difference in base curve (D) is equal to the difference in lens power (in air)
• Provides: fit like a toric base lens with power effect of non-flexing sphere
• Advantage: lens can rotate without compromising vision!

Diagnostic spherical lens OD
Toric lens on same eye

CASE STUDY II - Dr. Quinn

CC: 63-year-old female complaining of blurred vision OD following broken running corneal suture

Eye Hx: Fuchs Dystrophy (OD > OS) with penetrating keratoplasty OD three years prior (see photo)

Refraction:
     OD +4.50 -7.25 x 119 20/25
     OS +2.50 -1.25 x 065 20/20-1

Topography:
     Simulated K: 11.37 D of corneal toricity!

Treatment options:
     1. GP sphere
     2. GP toric
     3. Astigmatic keratotomy to attempt to reduce post-PK astigmatism to
         a more manageable level

Question: What would you do?

Final treatment:
     Topography OD shows a fairly regular astigmatic shape; thus a toric GP lens
     was pursued. Potential problems included:
          1. Laboratories can manufacture toric lenses up to around 7 D of toricity
          2. The assymetry of the astigmatism evident in topographic map
     A lens of the following parameters (after two unsuccessful attempts) was
     fit successfully, achieving 20/20-2 acuity:
     BC: 6.85/7.90
     SCR: 7.7/8.7
     SCW: 0.4
     PCR: 10.5/11.0
     PCW: 0.25
     Power: -3.50/+3.00
     ct: .22
     Tint: light blue
     Type: Boston EO (49.25 D/42.75 D)
     Difference in base curves: 6.50 D
     Difference in lens powers: 6.50 D. Therefore, is a SPE design.

 
CASE STUDY III - from a Symposium Participant

This is a case of a 64-year-old white male with a history of keratoconus sp PKP x2 OD and x1 OS 23 years ago. He was operated on at LSU. The OS graft apparently "slipped" or had wound over ride and he had a revision of the graft 10/29/02 at LSU by Dr. Kaufman.

I think he may have keratoglobus in the left eye, as the host cornea itself is abnormal and bulging. On top of this, nasally the cornea has an abrupt change in curve at the graft/host interface. The OD has a nice graft and appears more or less normal.

The host corneal bed is thick superiorly and temporally and thin inferiorly and nasally. I think this thinness was the reason a new graft was not done. The measurements are 601 microns at 12:00, 700 at 3:00, 370 at 6:00, and 418 at 9:00.

I was able to get a 7.15 BC/8.7/-2.25 RGP lens to stay on long enough to get an over refraction of -.25+1.50x165, which gave him an amazing 20/20 vision. He is otherwise CF in the eye. I am thinking that I would start by trying to fit a lens as small as possible, as I think that I may just be able to fit the "tip" of this mountain, so to speak, which is the corneal graft/cap area. He has very lax lids, and I am thinking this may work.

What are the recommendations of your panel experts?