Development of air assisted lamellar keratectomy for corneal haze model and deep anterior lamellar keratoplasty in dogs

Abstract

The purpose of the present study was development of air assisted lamellar keratectomy (AK) technique for the standardized corneal haze model and deep anterior lamellar keratoplasty in dogs. The AK was performed to achieve a constant ablation depth and size and to generate the efficient corneal haze. The ex vivo porcine corneas were categorized into four groups depending on the following trephined depths: 250, 375, 500 and 750 µm. After 4 ml air was injected to the stroma at the base of the trephination groove, the fuzzy region of the white opaque cornea was removed. No significant differences were observed between the trephined corneal depths for resection and the ablated corneal thickness at depths deeper than 375 µm. AK and conventional keratectomy (CK) were applied to six beagles and development of corneal haze was evaluated weekly until postoperative day 28. The occurrence of corneal haze and α-smooth muscle actin (SMA) expression following AK were significantly higher than those following CK. Therefore, AK was used to achieve the desired corneal thickness after resection and produce a sufficient corneal haze. The effect of onion extract ointment on corneal haze suppression was evaluated to verify the experimental utility of AK technique for the evaluation of haze development. After the AK was performed, an artificial tear (group C), prednisolone acetate (group P), onion extract ointment (group O), and transforming growth factor (TGF)-β1 (group T) were applied to each group. The haze was significantly suppressed in the group P and O compared with the group C from day-14 after the surgery. Also, the total green intensity for α-SMA was significantly less expressed in the group P and O than in the group C. Thus, the onion extract ointment was demonstrated to have the suppression effects for corneal haze development and AK technique was sufficient to evaluate these effects. The feasibility of deep anterior lamellar keratoplasty (DALK) using big-bubble technique (BBT), upon which the AK technique was based, was evaluated in three dogs. The eyes were examined until 150 days after the operation of DALK. The central portion of the transplanted cornea remained transparent while corneal haze developed around the transplanted margin. The marginal haze was rarely observed between the donor and recipient corneas at 150 days after the operation. A spotted haze developed in the central part of the deep stroma near the Descemets membrane (DM). Alpha-SMA positive cells were detected at the transplanted margin in which the corneal haze appeared clinically. Based on the results of the present studies, AK technique could be useful for the evaluation of corneal haze and contribute to improving the standardized corneal haze model.