Light transmission in the human cornea as a function of position across the ocular surface: theoretical and experimental aspects.
This article investigates the theoretical basis for differences in visible light transmission through the human cornea as a function of distance from the center. Experimentally, transmission decreases approximately linearly up to 3 mm from the central axis, then quadratically beyond this. It is known that collagen fibril number density and collagen fibril radii change from the central region to the corneal periphery. We modeled, using the direct-summation-of-scattered-fields method, the effects these ultrastructural changes would be expected to have on light transmission, accounting for the increase in corneal thickness from center to edge. Fibril positions for the modeling were obtained from electron micrographs of human cornea. Theoretically, transmission remains fairly constant across the central cornea; then, as the fibril diameter increases, the predicted scattering increases. Interfibrillar spacing changes alter the refractive index ratio between matrix and fibril; this was modeled in our theoretical deductions. Fibril number density had a minimal effect on light propagation. Our theoretical deductions were in broad agreement with our experimental data. It is concluded that the reduced transparency in the peripheral stroma is primarily caused by changes in fibril radius and an increase in refractive index ratio between the fibril and the interfibrillar substance.
Doutch
James
J
Structural Biophysics Group, School of Optometry and Vision Science, Cardiff University, Cardiff, United Kingdom.
Quantock
Andrew J
AJ
Smith
Valerie A
VA
Meek
Keith M
KM
D003315:Cornea / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D016850:Limbus Corneae / Q000502:physiology; D008954:Models, Biological; D013499:Surface Properties; D014785:Vision, Ocular
J Opt Soc Am. 1969 Jun;59(6):766-74
5805456
J Mol Biol. 1982 Oct 5;160(4):593-607
7175938
Ophthalmic Physiol Opt. 1986;6(1):47-56
3714275
Biophys J. 1993 Jan;64(1):273-80
8431547
J Physiol. 1973 Sep;233(3):589-612
4754873
Exp Eye Res. 1975 Jul;21(1):59-70
124659
J Physiol. 2002 Sep 1;543(Pt 2):633-42
12205195
J Physiol. 1970 Oct;210(3):601-16
5499815
Appl Opt. 1971 Mar 1;10(3):459-73
20094474
Invest Ophthalmol Vis Sci. 2007 Sep;48(9):4061-9
17724188
J Mol Biol. 2004 Feb 6;336(1):179-86
14741213
Invest Ophthalmol Vis Sci. 1995 Jul;36(8):1508-23
7601631
Eye (Lond). 2003 Nov;17(8):927-36
14631399
J Refract Surg. 2003 May-Jun;19(3):323-32
12777028
Biophys J. 1991 Aug;60(2):467-74
1912282
Invest Ophthalmol Vis Sci. 1991 Jul;32(8):2244-58
2071337
Optom Vis Sci. 2000 Jul;77(7):347-56
10939312
Cornea. 1998 Nov;17(6):627-39
9820944
Vision Res. 1997 Jan;37(2):249-53
9068825
Br J Ophthalmol. 1953 Feb;37(2):77-84
13032358
Ophthalmology. 2006 May;113(5):792-9.e2
16650675
Curr Eye Res. 1987 Jul;6(7):841-6
3621979
Exp Eye Res. 1996 Jun;62(6):651-62
8983947
Exp Eye Res. 2007 Mar;84(3):423-34
17178118
J Physiol. 1957 Apr 30;136(2):263-86
13429485
Exp Eye Res. 1966 Jul;5(3):221-8
5914654
Biophys J. 1997 Mar;72(3):1382-7
9138583
Invest Ophthalmol Vis Sci. 2003 Jul;44(7):2941-8
12824235
Exp Eye Res. 1988 May;46(5):765-8
3384021
Eye Contact Lens. 2005 Nov;31(6):281-7
16284509
IEEE Trans Biomed Eng. 1970 Jul;17(3):186-90
5464476
J Cell Sci. 1999 Mar;112 ( Pt 5):613-22
9973596
Structure. 2004 Feb;12(2):249-56
14962385
Curr Eye Res. 1995 Jun;14(6):459-64
7671627
Appl Opt. 1994 Jun 20;33(18):4013-24
20935748
J Opt Soc Am A. 1986 Nov;3(11):1970-82
3783292
Curr Eye Res. 1984 Jan;3(1):3-14
6690228
Exp Eye Res. 2004 Mar;78(3):493-501
15106928
Exp Eye Res. 1990 Apr;50(4):393-5
2338122
Br J Ophthalmol. 2003 Feb;87(2):225-36
12543757
Int Ophthalmol Clin. 1962 Oct;2:561-72
13934004
Biophys J. 2003 Oct;85(4):2205-12
14507686
Appl Opt. 1986 Aug 15;25(16):2739
18231553
Q Rev Biophys. 1984 Nov;17(4):423-51
6398877
Exp Eye Res. 2004 Mar;78(3):553-60
15106935