J Vet Sci.  2015 Sep;16(3):349-356. 10.4142/jvs.2015.16.3.349.

Air assisted lamellar keratectomy for the corneal haze model

• Kim S
• Park YW
• Lee E
• Park SW
• Park S
• Kim JW
• Seong JK
• Seo K

• KMID: 2344308
• DOI: http://doi.org/10.4142/jvs.2015.16.3.349

Abstract

To standardize the corneal haze model in the resection depth and size for efficient corneal haze development, air assisted lamellar keratectomy was performed. The ex vivo porcine corneas were categorized into four groups depending on the trephined depth: 250 microm (G1), 375 microm (G2), 500 microm (G3) and 750 microm (G4). The stroma was equally ablated at the five measurement sites in all groups. Significant differences were observed between the trephined corneal depths for resection and ablated corneal thickness in G1 (p < 0.001). No significant differences were observed between the trephined corneal depth for resection and the ablated corneal thickness in G2, G3, and G4. The resection percentage was similar in all groups after microscopic imaging of corneal sections. Air assisted lamellar keratectomy (AK) and conventional keratectomy (CK) method were applied to six beagles, after which development of corneal haze was evaluated weekly until postoperative day 28. The occurrence of corneal haze in the AK group was significantly higher than that in the CK group beginning 14 days after surgery. Alpha-smooth muscle actin expression was significantly higher in the AK group (p < 0.001) than the CK group. Air assisted lamellar keratectomy was used to achieve the desired corneal thickness after resection and produce sufficient corneal haze.

Keyword

ablated corneal depth; air assisted lamellar keratectomy; canine eye; corneal haze; porcine eye

MeSH Terms

Animals
Cornea/*surgery
Corneal Opacity/etiology/*surgery
Disease Models, Animal
Dogs
Humans
Ophthalmologic Surgical Procedures/*methods
Sus scrofa
*Wound Healing

Figure

• 

  Fig. 1 Air assisted lamellar keratectomy. (A) The enucleated porcine eye was placed on a specially designed frame. (B) The center of the cornea was trephined using a vacuum trephine. (C) Four mL of air was injected at the base of the trephination gutter into the corneal stroma using a 30-gauge needle attached to a syringe. (D) Intrastromal blanching was observed. (E) The blanched cornea was removed using a corneal dissector and blunt-tipped corneal scissors. (F) Appearance after keratectomy using air assisted lamellar keratectomy. (G) Schematic diagrams for measuring corneal thickness. The dotted line indicates the ablated corneal area and the arrows show an 8 mm diameter. The measurement sites of corneal thickness by ultrasonic pachymeter are marked by black dots. (H) Diagram of the corneal cross section. The thickness of the ablated area (b) was subtracted from the normal corneal thickness (a) to calculate the ablated corneal thickness (c).

• 

  Fig. 2 Ablated corneal thickness (%) calculated based on the pachymetry and photomicrographic image analyses results in each group; G1 = 250 µm, G2 = 375 µm, G3 = 500 µm, G4 = 750 µm trephine for resection.

• 

  Fig. 3 Photomicrograph of a porcine cornea with periodic acid Schiff (PAS) stain. (A) Normal porcine cornea showing aligned stromal layers. (B) Stroma of the air-injected cornea was deformed by small air bubbles above the layer for needle insertion. (C) After resection by the air assisted lamellar keratectomy showing smooth ablated surface. 200× magnification. Scale bars = 50 µm.

• 

  Fig. 4 Slit-lamp biomicroscopy of the corneas with subepithelial haze. Greater corneal haze developed following air assisted lamellar keratectomy (AK group; A-E) than conventional keratectomy (CK group; F-J). The size of the captured corneal section was fixed by controlling the magnification of the slit lamp (10× magnification) under diffuse illumination (45°).

• 

  Fig. 5 Corneal haze measurement by quantitative and qualitative methods. (A) Clinical corneal haze grading. (B) Quantification of corneal haze. Significant differences are indicated by Student's t-test (ap < 0.05) and one-way analysis of variance with Bonferroni's post-hoc test (bp < 0.05).

• 

  Fig. 6 Histopathological evaluation for the development of corneal haze in the normal cornea (A and D), conventional keratectomy (CK; B and E), and the air assisted lamellar keratectomy (AK; C and E) groups. DAPI-stained nuclei are shown in blue, SMA-stained cells are shown in green. (A-C) PAS stain. 200× magnification. Scale bars = 50 µm. (D-F) Immunohistochemistry stain for α-smooth muscle actin (SMA). 200× magnification. Scale bars = 50 µm.

• 

  Fig. 7 Total intensity of green color for the quantification of α-SMA positive cells in each group. Significant differences are indicated by Student's t-test (ap < 0.05) and one-way analysis of variance with Bonferroni's post-hoc test (bp < 0.05).

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