Korean J Ophthalmol.  2014 Feb;28(1):76-82. 10.3341/kjo.2014.28.1.76.

Effects of Argon Laser Iridotomy on the Corneal Endothelium of Pigmented Rabbit Eyes

• Youm JH
• Heo JH
• Kim HM
• Song JS

• KMID: 1792096
• DOI: http://doi.org/10.3341/kjo.2014.28.1.76

Abstract

PURPOSE
In Asian countries, laser iridotomy for the treatment of angle-closure glaucoma is a common cause of bullous keratopathy, which may be associated with a shallow anterior chamber and dark iris pigmentation in Asians. Several cases of corneal decompensation after argon laser iridotomy have been reported. In the present study, we evaluated the harmful effects of argon laser iridotomy on the corneal endothelium.
METHODS
Argon laser iridotomy was performed on the right eyes of pigmented rabbits. Changes in corneal thickness and endothelial cell density after laser iridotomy were evaluated. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed for assessment of corneal endothelial cell apoptosis. Combined staining with alizarin red and trypan blue, as well as a live/dead cell assay, were performed for evaluation of damage to the corneal endothelium induced by laser iridotomy.
RESULTS
Corneal thickness did not change immediately after laser iridotomy; however, a significant increase was observed 24 hours after iridotomy (p = 0.001). The endothelial cell density of laser-treated eyes four days after laser iridotomy was significantly decreased compared with control eyes (p < 0.001). TUNEL staining showed many TUNEL-positive cells in the corneal endothelium and corneal stroma. No endothelial trypan blue-stained cell nuclei were observed after laser iridotomy; however, several large endothelial cells with damaged membrane integrity were observed. The live/dead cell assay clearly showed a large number of dead cells stained red in several areas throughout the entire corneal button 24 hours after iridotomy.
CONCLUSIONS
Argon laser iridotomy induces corneal endothelial cell apoptosis in pigmented rabbit eyes, resulting in decreased endothelial cell density.

Keyword

Apoptosis; Argon laser iridotomy; Cornea; Corneal endothelium

MeSH Terms

Animals
Apoptosis
Corneal Diseases/pathology/*surgery
Disease Models, Animal
Endothelium, Corneal/*pathology
In Situ Nick-End Labeling
Iris/*surgery
Laser Therapy/*methods
Lasers, Gas/*therapeutic use
Ophthalmologic Surgical Procedures/*methods
Rabbits

Figure

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  Fig. 1 A rabbit eye after argon laser peripheral iridotomy in each of four quadrants (superior temporal, superior nasal, inferior temporal, and inferior nasal) using an Abraham iridotomy contact lens.

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  Fig. 2 Change in mean central corneal thickness after argon laser iridotomy (LI). Although corneal thickness did not differ significantly before and immediately after iridotomy (p = 0.276), it showed a significant increase 24 hours after iridotomy compared with before LI (p = 0.001, n = 10).

• 

  Fig. 3 (A) In normal rabbit corneas, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells were not detected in the corneal stroma or corneal endothelium. (B) Twenty-four hours after argon laser iridotomy, many TUNEL-positive cells (arrows) were observed in the corneal endothelium as well as in the corneal stroma. TUNEL staining, bar = 20 µm.

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  Fig. 4 (A) Twenty-four hours after iridotomy, intercellular borders of endothelial cells were clearly stained with alizarin red, and several large endothelial cells with damaged membrane integrity (arrows) were observed. (B) Endothelial cells with trypan blue-stained nuclei were not observed. (C) Four days after iridotomy, damaged endothelial cells were no longer found, and a normal mosaic pattern was observed. Dual staining of trypan blue and alizarin red, bar = 40 µm.

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  Fig. 5 (A) Almost all endothelial cells of normal cornea were viable and stained green. (B) One day after iridotomy, many dead cells stained red were observed in several areas throughout the corneal button. (C) Four days after iridotomy, dead cells were no longer observed. Live/dead cell assay, bar = 20 µm.

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  Fig. 6 The mean percentage of live cells in the corneal endothelium. Although 100% of corneal endothelial cells in the normal cornea were alive, 24 hours after laser iridotomy (LI), the percentage of live cells was 78.9% (n = 4, p < 0.001).

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