Effects of Ocular Parameters on Diameter of Well-fitted Rigid Gas Permeable Lens in Koreans

Min Seon Park; Young Kee Park; Sang-Mok Lee

doi:10.3341/jkos.2017.58.9.1031

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

Original Article

J Korean Ophthalmol Soc 2017;58(9):1031-1035.

Published online: 8 September 2017

DOI: https://doi.org/10.3341/jkos.2017.58.9.1031

Effects of Ocular Parameters on Diameter of Well-fitted Rigid Gas Permeable Lens in Koreans

Min Seon Park, M.D.¹, Young Kee Park, MD, PhD², Sang-Mok Lee, MD, PhD^1,

¹Department of Ophthalmology, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea

²YK Eye Clinic, Seoul, Korea

Address reprint requests to Sang-Mok Lee, MD, PhD Department of Ophthalmology, Hallym University Sacred Heart Hospital, #22 Gwanpyeong-ro 170beon-gil, Dongan-gu, Anyang 14068, Korea Tel: 82-31-380-3834, Fax: 82-31-380-3833 E-mail: lsm10003@gmail.com

Received 8 June 20179 August 2017 Accepted 31 August 2017

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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.

Keywords: Back optic zone radius, Corneal diameter, Eccentricity, Keratometric value, Rigid gas permeable (RGP) lens

References

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4. Efron N, Morgan PB, Woods CA. International Contact Lens Prescribing Survey Consortium. International survey of rigid con-tact lens fitting. Optom Vis Sci. 2013; 90:113–8.

5. Bennett ES, Henry VA. Clinical Manual of Contact Lenses. 4th ed. Philadelphia: Lippincott Williams & Wilkins;2014. p. 112–26.

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7. Lee DH. Basic fitting of RGP contact lens. The Korean Contact Lens Study Society. ed. Lens: Principles and practice, 1st ed. Paju: Kunja;2015. v.1:p. chap. 7.

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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.

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.

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.

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