Comparison of Tear Distributions by the Corneal Eccentricity when Fitted with Spherical and Aspherical RGP Lenses

구면 및 비구면 RGP렌즈 피팅 시 각막 이심률별 눈물분포 비교

  • Received : 2016.05.01
  • Accepted : 2016.06.09
  • Published : 2016.06.30


Purpose: The present study was aimed to compare the tear volume and distribution by corneal eccentricity when fitted with spherical and aspherical RGP lenses. Methods: Spherical and aspherical RGP lenses were fitted in best alignment on a total of 77 subjects (136 eyes) in their twenties and thirties without any ocular disease or ocular surgery experience. The tear volume was analyzed by estimating the concentration of tear stained with fluorescein in the center of RGP lens as well as at the mid-peripheral and peripheral areas, and the difference of tear distributions was analyzed according to corneal eccentricity. Results: Tear distribution from the center to the peripheral area was not significantly different when spherical RGP lenses were fitted on the corneal eccentricities of e < 0.38 and $0.68{\leq}e$, indicating the relatively even tear distribution compared with other corneal eccentricity. In the case of aspherical RGP lenses, the difference of tear distribution between the central and peripheral areas was smaller than spherical RGP lenses. The significant difference of tear distribution according to RGP lens design was observed in the corneal eccentricity of 0.48 < e < 0.68. In other words, more even tear distribution was shown when aspherical RGP lenses were fitted on the cornea with eccentricity of $0.48{\leq}e<0.68$ and spherical RGP lenses were fitted on the cornea with eccentricity $0.68{\leq}e$. Furthermore, tear volume in the mid-peripheral area increased with higher corneal eccentricity. Conclusions: The results suggest that the appropriate selection of RGP lens design according to corneal eccentricity is necessary since tear volume and distribution by the regions of spherical and aspherical lenses are affected by corneal eccentricity.


Corneal eccentricity;Tear volume;Tear distribution;RGP lens fitting;RGP lens design


  1. Clark BAJ. Mean topography of normal corneas. Aust J Optom. 1974;57(4):107-114.
  2. Kiely PM, Smith G, Carney LG. The mean shape of the human cornea. Optica Acta. 1982;29(8):1027-1040.
  3. Mandell RB. The enigma of corneal contour; Everett Kinsey Lecture. CLAO J. 1992;18(4):267-273.
  4. Davis WR, Raasch TW, Mitchell GL, Mutti DO, Zadnik K. Corneal asphericity and apical curvature in children : a cross-sectional and longitudinal evaluation. Invest Ophthalmol Vis Sci. 2005;46(6):1899-1906.
  5. Eghbali F, Yeung KK, Maloney RK. Topographic determination of corneal asphericity and its lack of effect on the refractive outcome of radial keratotomy. Am J Ophthalmol. 1995;119(3):275-280.
  6. Mandell RB, Sthelen R. Mathematical model of the corneal contour. Br J Physiol Opt. 1971;26(3):183-197.
  7. Guillon M, Lydon DP, Wilson C. Corneal topography: a clinical model. Ophthalmic Physiol Opt. 1986;6(1):47-56.
  8. Sheridan M, Douthwaite WA. Corneal asphericity and refractive error. Ophthalmic Physiol Opt. 1989;9(3):235-238.
  9. Maseedupally V, Gifford P, Swarbrick H. Variation in normal corneal shape and the influence of eyelid morphometry. Optom Vis Sci. 2015;92(3):286-300.
  10. Bier N. The contour lens a new form of corneal lens. Australas J Optom. 1957; 40(7):318-320.
  11. Bayshore CA. Report on 276 patients fitted with micro corneal lenses, apical clearance and cetral ventilation. Am J Optom Arch Am Acad Optom. 1962;39(10):552-553.
  12. Gasson A, Morris JA. The contact lens manual a practical guide to fitting, 3rd Ed. Seoul: Daihakseolim, 2005;153-158.
  13. Park SI, Lee SE, Kim SR, Park M. A comparison of the movement of aspheric RGP lens on cornea by the amounts of keratometric astigmatisms using keratometer and corneal topography. J Korean Ophthalmic Opt Soc. 2011;16(2):123-133.
  14. Park EH, Kim SR, Park M. The comparison of fluorescein patterns between spherical RGP lens and aspherical RGP lens by corneal type and astigmatic degree. J Korean Ophthalmic Opt Soc. 2012;17(1):37-45.
  15. Lim SG, Lee MH, Choi SM, Park SH, Kim SR, Park M. A relationship between corneal type, corneal astigmatism and lens fitting states and the stable centration of spherical RGP lens. J Korean Ophthalmic Opt Soc. 2012;17(2):143-151.
  16. Park EH, Kim SR, Park M. A comparison of the contact areas between cornea and RGP lenses by fitting status. J Korean Ophthalmic Opt Soc. 2012;17(3):255-264.
  17. Kim J, Kim SR, Park M. The effects of corneal type and corneal astigmatism on tear volume between rigid gas permeable lens and the cornea. J Korean Ophthalmic Opt Soc. 2015;20(2):141-150.
  18. Park EH, Kim SR, Park M. A Relationship between corneal eccentricity and stable centration of RGP lens on cornea. J Korean Ophthalmic Opt Soc. 2012;17(4):373-380.
  19. Mannis MJ, Zadnik K, Coral-Ghanem C, Kara-Jose N. Contact lenses in ophthalmic practice, 1st Ed. New York: Springer Verlag, 2004:62-64.
  20. Douthwaite WA. Contact lens optics and lens design, 3rd Ed. London: Butterworth-Heinemann, 2006;99-104.
  21. Fletcher R, Lupelli L, Rossi AL. Contact lens practice: a clinical guide, 1st Ed. London: Blackwell Scientific Publications, 1994;34-35.
  22. van der Worp E. Respecting the shape of the cornea in RGP lens fitting. Optom Pract. 2004;5(4):153-162.
  23. Young G. The effect of rigid lens design on fluorescein fit. Cont Lens Anterior Eye. 1998;21(2):41-46.
  24. Gonzlez-Mijome JM, Villa-Collar C, Monts-MicR, Gomes A. Asphericity of the anterior human cornea with different corneal diameters. J Cataract Refract Surg. 2007;33(3):465-473.