动物造模,药效评价,角膜损伤 z-bio 2024-08-02 477

　　Corneal injury can be divided into damage to the corneal endothelium and damage to the corneal epithelium and stroma according to different levels. Damage to the corneal endothelium can be replicated through mechanical injury methods (such as needle insertion into the anterior chamber to scrape off the endothelium) and penetrating corneal freezing. Corneal epithelial and stromal damage can also be achieved through mechanical injury (removal of the conjunctival and limbal epithelium of the rabbit corneal plate and corneal margin) or laser injury. The following mainly introduces the laser corneal injury model.

　　The eye is the most sensitive and vulnerable target organ to laser in the body. The main sites of laser induced eye damage are the cornea and retina, and different laser parameters can have a significant impact on the location and severity of the damage. The cornea is the outermost layer of the eyeball, with an absorption rate of nearly 100% for far ultraviolet rays with wavelengths shorter than 280nm, and a full absorption body for mid infrared and far infrared rays above 1900nm. Therefore, the cornea is susceptible to damage from ultraviolet and mid infrared lasers. The wavelength of CO2 laser is 10.6 μ m, which is a far-infrared laser. The absorption coefficient of CO2 laser by biological tissues is high, and its biological mechanism is mainly thermal. When low-energy output and short-term irradiation occur, 98% of the CO2 laser energy is absorbed by the initial 40 μ m thickness of the cornea, mainly by the epithelial cells rich in water, causing minimal thermal diffusion and leading to corneal damage and scar formation.

　　After anesthesia of experimental animals, CO2 laser was immediately vertically irradiated onto the center of the cornea with a spot diameter of 5mm. Chloramphenicol was dropped twice a day and observed under a slit lamp microscope for 2 months.

　　[Model features] Mild corneal injury may result in white or grayish white coagulation spots, which are reversible and do not leave scars after recovery; For those with severe damage, it can involve the deep layers of the corneal stroma, leaving scars after recovery, and affecting vision when obstructing the pupil; Severe injuries can cause corneal perforation and blindness.

　　[Model Evaluation and Application] Experimental studies on rabbits have shown that at an irradiation time of 1 second and a power density of 127W/square centimeter, 60% of the cornea eventually developed perforation, 40% of the cornea developed scars, with a scar diameter of about 6.8mm, and a few cases had vascular hyperplasia, with scars reaching the entire corneal layer. When the irradiation time is 1 second and the power density is 102W/square centimeter, after 30 days, all corneas show scars with a diameter of about 6.4mm; When irradiated with the same power density for 0.5 seconds, all scars appeared after 20 days, with a scar diameter of about 5.7mm. Power density of 62W/square centimeter, time of 0.5 seconds, all scars appeared after 16 days, with a scar diameter of about 5.3mm. Therefore, it is believed that the most suitable laser parameters for corneal scar models are energy density of 30-100J/square centimeter and scar formation time of 15-30 days after irradiation. When establishing a corneal injury model, different exposure of the cornea before laser irradiation can result in varying water content on the corneal surface, thereby affecting the degree of corneal injury.