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Carmen M Martinez-Garcia, Francisco Javier Avila, Patricia Gallego-Muñoz, Elvira Lorenzo-Martín, Lucia Ibares-Frías, Juan M Bueno; Long term studies in alkali burn corneal healing.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4352. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Long-term studies on corneal tissue recovery after alkali burns are limited in the literature. In this study we propose to describe the last stages of the healing process from different points of view: clinical, optical and histological.
Left eyes of New Zealand rabbits were burned for 60 seconds with an 8-mm filter paper soaked in 0.5N NaOH. Corneas were excised at 1, 3, 5 and 6 months. Right eyes were used as control. Clinical signs such as opacity (measured by Fantes scale), and pachymetry (using an ultrasonic pachymeter), were revised every two weeks over a 6-month period. Hematoxylin-Eosin (HE) stained sections were used for histologic assessment of both stroma and epithelium thickness. Collagen disposition was observed with picrosirius red stain and polarized light microscopy. The presence of α-smooth actin (α-SMA) and re-innervation were assayed by means of immunofluorescence. Visible-light transmittance was measured with a spectrophotometer. Changes in collagen organization at the anterior stroma were studied using a Second Harmonic Generation (SHG) microscopy and a Fourier transformation algorithm, that provide numerical information by means of two parameters, the organization index (OI) and the dominant direction of the fibers (DD).
Corneal opacity of burned eyes disappeared after 6 weeks. Compared to the control eyes, pachymetry values were higher and significantly different until 3months, then they reduced to similar values at 6 months. Corneal thickness measured in histological sections did not show significant differences with the control after 5 months of healing. However, the decrease in epithelium thickness showed significant differences to the control after 6 months. At this time point, histological sections with HE and Picrosius red stain were similar to control, and negative to αSMA immunofluorescence. Tubulin immunofluorescence showed thick branches in the stroma and tiny and thin ramifications in the epithelium. Transmittance ratio (burned vs. control) was very low at 1month and increased at 6 months. SHG microscopy images revealed that after 6 months the stroma recovered its OI and a structural DD re-appears.
Our results demonstrated by objective measurements the extraordinary regeneration of the cornea and the ability to remodel its extracellular matrix to get the transparency. Being able to shorten the period of time involved poses a challenge for vision science.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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