Journal List > J Korean Ophthalmol Soc > v.58(9) > 1010629

Park, Park, and Lee: Effects of Ocular Parameters on Diameter of Well-fitted Rigid Gas Permeable Lens in Koreans

Abstract

Purpose

To compare the differences of parameters of 9.3 mm and 8.8 mm rigid gas permeable lenses (RGP lenses) that were prescribed by trial lens fitting.

Methods

Ninety-three eyes of 49 patients were prescribed RGP contact lenses (YK spherical lens, Lucid Korea, Bonghwa, Korea) by a single ophthalmologist at the same hospital. We analyzed the differences of parameters of 9.3 mm and 8.8 mm rigid gas permeable lenses (RGP lenses) that were prescribed by trial lens fitting. Steep keratometric value (Ks), flat keratometric val-ue (Kf), and corneal astigmatism (Kast) were measured by keratometer. Simulated steep keratometric value (Sim Ks), simulated flat keratometric value (Sim Kf), simulated corneal astigmatism (Sim Kast), white to white corneal diameter (WTW), and eccen-tricity were measured by corneal topography. We also analyzed the differences of back optic zone radius (BOZR) and lens pow-er between the two groups.

Results

In this study, 40 eyes wearing 8.8 mm lenses and 53 eyes wearing 9.3 mm lenses were included. Keratometric value and eccentricity were significantly higher in the 8.8 mm lens group, while WTW and BOZR were significantly lower. Corneal as-tigmatism (Kast, Sim Kast) and lens power were not significantly different between the groups.

Conclusions

RGP lenses with a smaller diameter were likely to be prescribed to patients with higher keratometric value, higher eccentricity, and shorter WTW, and the average BOZR of the prescribed RGP lenses with a smaller diameter was likely to be steeper.

References

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Figure 1.
Corneal keratometric value (Ks, Kf, Sim Ks, Sim Kf, Kast, Sim Kast) in 8.8 mm and 9.3 mm lens groups. (A) Corneal kera-tometric value (Ks, Kf, Sim Ks, Sim Kf) is significantly higher in 8.8 mm lens group compared to 9.3 mm lens group (8.8 mm group vs 9.3 mm group; Ks: 45.32 ± 1.96 D vs. 44.34 ± 1.48 D, p = 0.007; Kf: 43.34 ± 1.35 D vs. 42.78 ± 1.34 D, p = 0.05; Sim Ks: 45.21 ± 1.93 D vs. 44.19 ± 1.47 D, p = 0.005; Sim Kf: 43.33 ± 1.36 D vs. 42.73 ± 1.40 D, p = 0.043). (B) Corneal astigma-tism (Kast, Sim Kast) is not significantly different in 2 groups. p-value by independent t-test. Ks, Kf, Kast = steep keratometric value, flat keratometric value, corneal astigmatism measured by keratometer, respectively; Sim Ks, Sim Kf, Sim Kast = simulated steep keratometric value, simulated flat keratometric value, simulated corneal astigmatism measured by corneal topographer, respectively. * p < 0.05, p < 0.01.
jkos-58-1031f1.tif
Figure 2.
White to white corneal diameter (WTW) and Eccentricity in 8.8 mm and 9.3 mm lens groups. (A) WTW is significantly lower in 8.8 mm lens group (11.64 ± 0.42 mm vs. 12.11 ± 0.58 mm, p < 0.001). (B) Eccentricity is significantly higher in 8.8 mm lens group (0.54 ± 0.15 vs. 0.47 ± 0.13, p = 0.011). p-value by independent t-test. * p < 0.05; p < 0.01.
jkos-58-1031f2.tif
Figure 3.
Back optic zone radius (BOZR) and power in 8.8 mm and 9.3 mm lens groups. (A) BOZR is significantly lower in 8.8 mm lens group (7.78 ± 0.24 mm vs. 7.92 ± 0.23 mm, p = 0.008). (B) Power is not significantly different in 2 groups. p-value by independent t-test. * p < 0.01.
jkos-58-1031f3.tif
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