This case involves a 9-year-old Asian male born with congenital ptosis OS, which induced high astigmatism and amblyopia—a case near and dear to me as he is my son. When he was 3 months old, he was examined at a regional medical center and ptosis surgery was recommended. My mother, an ophthalmologist, advised against it, citing studies that general anesthetic at a young age has been associated with a negative effect on brain development. Thus, he did not have ptosis surgery until he was 7. 

Case Description

I’ve been examining him his whole life, observing as his left eye refractive error progressed from +1.25 -1.75 x 180 at 3 months, to -1.00 -3.25 x 176 at 9 years old.

Before ptosis surgery, his axial length in his left eye progressed from 21.12mm to 23.33mm, his astigmatism increased to -3.25 DC, and he was amblyopic with BCVA OS of 20/60. I performed OD patching, VT, a SCL fit and atropine, and finally ortho-K. 

He was fit with several ortho-K lenses to improve his vision, off label due to high astigmatism, with varying results. Finally, I tried the NewVision corneal-scleral lens (Acculens). Profilometry was used for lens design resulting in BCVA of 20/20 with manifest refraction -1.00 -3.25 x 176. The vision in his left eye is 20/20 with the lens on, and 20/20-1 when the lens removed. The right eye is 20/20 with and without lenses, which I had fit in ortho-K prophylactically, as I have done with my 4- and 7-year-old children as well. 

Discussion 

The design used here is larger (11.5mm) than standard ortho-K, with edges formulated in a way to improve comfort. This size is smaller than usual, as the patient has a very small HVID of around 11.0mm.

Fitting ortho-K lenses is about achieving lens centration. Larger diameter ortho-K lenses may be best described as trans-limbal that are designed such that the alignment/touch happens only at the cornea. 

The trans-limbal concept is to create a larger alignment section for improved centration. The edge is lifted over the limbal area to avoid stem cells and to improve tear dynamics, while the lens edge is moved away from the cornea.

Research has shown there is a low correlation between the central shape of the eye and the far periphery of the cornea and beyond the limbus (DeNaeyer, 2019).¹ Therefore, profilometry as used in this case may be best to measure sagittal height (SAG) in of the alignment and edge sections.

Figure 1 is an example of a toric eye with the rule. An 11mm chord length is used to show the amount of SAG difference (toricity). 160 microns (0.16mm) does require a toric design in the alignment section.

Axial length is stable, currently at 22.53, which according to Tideman graphs (Gifford, 2023)² is a risk of 16% for myopia, and no risk for high myopia.

Conclusion

A trans-limbal design may be the best choice in cases of ortho-K fitting when centration needs to be accurate as possible. Keeping up with the research, new trials and technologies will benefit the patient and the health system.

Rae Huang, OD, MS, has private practices in Boston and Newton, Mass. She writes about how to prevent myopia and other eye conditions at preventativeeyecare.com. She has no disclosures to report. 

REFERENCES

1. DeNaeyer G, Sanders DR, Michaud L, et al. Correlation of corneal and scleral topography in cases with ectasias and normal corneas: The SSSG Study. J Cont Lens Res Sci. 2019;3(1):10-20.

2. Gifford K. How to Use Axial Length Growth Charts. myopiaprofile.com/articles/how-to-use-axial-length-growth-charts. Accessed August 31, 2023.