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Contact Lens Spectrum

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HYBRID HOW-TO

HIGH SAG IN A TORIC CORNEA: IMPROVING QUALITY OF VISION

By: STEPHANIE RAMDASS, OD, MS, MBA
Contact Lens Spectrum June 1, 2021 Vol 36, Issue June 2021 Page(s): 24

In my April 2020 Custom Soft Corner column, I reviewed the clinical case of two sisters who were on the hunt for comfortable daily disposable lenses that provided stable and clear vision. Table 1 provides a summary of their updated ocular measurements. 

TABLE 1 PATIENTS’ OCULAR MEASUREMENTS
  CASE 1 (16 years old) CASE 2 (19 years old)
Spectacle Refraction OD: –5.00 –1.00 x 170
OS: –5.00 –1.00 x 165		 OD: –4.50 –1.50 x 175
OS: –4.50 –1.50 x 005
Flat K/steep K (D) OD: 44.31/46.00 @ 090
OS: 44.13/46.10 @ 067		 OD: 44.98/46.60 @ 100
OS: 45.27/46.46 @ 080
Diagonal Visible Iris Diameter (mm) OD: 12.37
OS: 12.43		 OD: 11.97
OS: 11.94
Horizontal Visible Iris Diameter (mm) OD: 12.4
OS: 12.5		 OD: 12.0
OS: 12.1

A dollar store ruler is really all that you need to gauge how successful each of these patients will be in a mass-produced soft lens. We know that the larger the cornea, the deeper or greater the sagittal height of the eye. The daily disposables trialed on each sister all decentered and resulted in increased lens awareness, especially after a few hours of wear, and in unstable vision. Each sister was fit in empirically ordered hybrid contact lenses by supplying the manufacturing lab with spectacle Rx, Ks, and horizontal visible iris diameter (HVID) (Figure 1).

Figure 1. Handheld ruler used to measure HVID (> 12mm). Photo captured of the measurement and then zoomed in to accurately measure.
Figure 1. Handheld ruler used to measure HVID (> 12mm). Photo captured of the measurement and then zoomed in to accurately measure.

Notable Improvements

During the dispense visit, each sister reported excellent quality of vision that was far superior to that with any of the soft toric daily disposables that they had previously trialed. The lenses settled on-eye for at least five minutes and then were evaluated. Ideal movement of the soft skirt is similar in primary gaze and upgaze to that of a soft lens (video available below). The 8.5mm GP diameter matches the optic zone diameter in newer-generation hybrid lenses, theoretically giving wearers an optimal visual experience regardless of pupil size. The tear lens under the GP center adds to the high quality and quantity of vision. There was full corneal coverage, with only slight decentration of each 14.5mm diameter lens on-eye (Figure 2).


 

Figure 2. First dispense of an empirically ordered hybrid lens. Note the excellent centration, and visual quality was comparable to spectacle lens acuity.
Figure 2. First dispense of an empirically ordered hybrid lens. Note the excellent centration, and visual quality was comparable to spectacle lens acuity.

One Week Later

One week after successful dispense of their hybrid lenses, the sisters returned for a follow-up visit. Wear time was eight-to-10 hours every day for the 16-year-old, while the 19-year-old struggled with application and felt that the lenses blurred her peripheral vision. The 16-year-old was happy with the comfort and level of vision with the lenses. Slit lamp examination revealed a decrease in lens movement on both eyes for each sister, with no signs of corneal compromise upon removal.

Next Steps

Should modifications to the hybrid lens linear skirt be incorporated? I will discuss my clinical approach in my October 2021 column. CLS

Dr. Ramdass is in private practice in Toronto, Canada. You can reach her at StephanieRamdass@ferris.edu. She has received travel funding from Paragon Vision Sciences and lecture honoraria from Wink Productions, Inc. and Bausch + Lomb.

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