Transparency, swelling and scarring in the corneal stroma

Meek, Keith Michael Andrew ORCID: https://orcid.org/0000-0002-9948-7538, Leonard, D., Connon, Che John, Hayes, Sally ORCID: https://orcid.org/0000-0001-8550-0108 and Khan, S. 2003. Transparency, swelling and scarring in the corneal stroma. Eye 17 (8) , pp. 927-936. 10.1038/sj.eye.6700574

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Abstract

Purpose This paper briefly reviews current explanations for corneal transparency and uses a well-developed model to try to explain the increased light scattering either accompanying corneal swelling or following phototherapeutic keratectomy (PTK). Methods The direct summation of fields (DSF) method was used to compute light transmission as a function of wavelength. The method requires input of a number of structural parameters. Some of these were obtained from electron micrographs and others were calculated from X-ray diffraction data. Results By swelling sections of stroma cut from different depths in the tissue, we have shown that fluid entering the cornea causes more swelling in the posterior lamellae than in the anterior lamellae. Furthermore, posterior lamellae can reach a higher final hydration than anterior lamellae. Collagen-free regions ('lakes') exist in corneas swollen in vitroand in Fuch's dystrophy corneas, many of which may be caused by the death of cells. The DSF method shows that local fibril disordering, increased refractive index mismatch, and increased corneal thickness together can account for a 20% increase in light scattering in a Fuch's dystrophy cornea at H=5.8 compared to the normal cornea. Additional scattering is probably caused by 'lakes'. The DSF method applied to PTK rabbit stroma with high levels of haze suggests that the newly deposited collagen is not the cause of the increased light scattering. Conclusions Fluid is not uniformly distributed within the corneal stroma when the cornea swells. Increased hydration of posterior lamellae may be because of known differences in the glycosaminoglycans between the anterior and posterior stroma. Lamellar interweave in the anterior stroma probably limits the extent to which the constituent lamellae can swell. The DSF method can be used to account for increased light scattering in oedematous corneas but cannot account for haze following PTK.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
Uncontrolled Keywords:	corneal transparency, stroma, swelling, oedema, phototherapeutic keratectomy
Additional Information:	Cambridge Ophthalmological Symposium
Publisher:	Nature Publishing Group
ISSN:	0950-222X
Date of First Compliant Deposit:	30 March 2016
Last Modified:	17 Nov 2024 09:45
URI:	https://orca.cardiff.ac.uk/id/eprint/37025

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