The Experimental And Clinical Studies Of Transepithelial Photorefractive Keratectomy (Trans-PRK)

Part 1 Comparison of transforming growth factor-β1 in tear fluid following Trans-PRK and LASEK in patients with high myopiaPurpose To compare the release of transforming growth factor-β1 (TGF-β1) in the tear fluid of 30 patients with high myopia who underwent transepithelial photo refractive keratectomy (Trans-PRK) in one eye and laser subepithelial keratomileusis (LASEK) in the contralateral eye. Methods Tear fluid samples were collected with scaled microcapillary tubes preoperatively (day 0) and on the first, third and fifth postoperative days. The release of TGF-β1 was determined by multiplying the concentration of TGF-β 1 by capillary tear fluid flow. Corneal haze was also evaluated at 1,3 and 6 months following the surgeries. Results The median TGF-β1 release values for T-PRK and LASEK were:day 0.30.5±13.7 and 36.3±12.5 pg/min, respectively (P=0.09); day 1, 94.4±26.7 and 127.2±35.3 pg/min, respectively, which revealed a significant difference between the two procedures (P=0.0001); day 3,85.3±30.4 and 116.8±38.9 pg/min, respectively (P=0.001);day 5,74.1±26.5 and 92.5±34.6 pg/min, respectively (P=0.02). A statistically significant difference in the mean corneal haze score was observed between Trans-PRK and LASEK at 1 month (0.54±0.29 vs.0.89±0.51, respectively; P=0.001). At 3 (P=0.28) and 6 months (P=0.41) after surgery, no statistically significant differences in mean corneal haze score were identified between the two treatments. Conclusions The level of TGF-β1 in the tear fluid in the early postoperative days following Trans-PRK was reduced compared with that following LASEK surgery, which may be the cause of the lower grade of corneal haze.Part 2 One year clinical outcomes following Trans-PRK in patients with low to high myopiaPurpose To evaluate postoperative pain, corneal epithelial healing, development of corneal haze, refractive outcomes, uncorrected visual acuity, complications in patients with low to high myopia following Trans-PRK. Methods 405 eyes of 210 myopic patients were retrospectively recruited and divided into two groups according to myopic degrees:mild to moderate myopic group and high myopic group. Postoperative pain was evaluated in primary 24h after surgery. Corneal haze was evaluated at 1m,3m,6m,12m. Uncorrected visual acuity was evaluated at time when contact lenses were taken out, 1m,3m,6m,12m. Results Demographic data and the pain scores during surgery were similar between the two groups. The mean postoperative pain scores of patients in the cold patch group at 8,16, and 24 h we Conclusions The level of TGF-β1 in the tear fluid in the early postoperative days following Trans-PRK was reduced compared with that following LASEK surgery, which may be the cause of the lower grade of corneal haze.Part 3 Posterior corneal surface keeps in the original position in high myopia patients with a thin cornea following Trans-PRKPurpose To observe the stability of posterior corneal surface in patients with a thin cornea following Trans-PRK and evaluate the safety of Trans-PRK for the patients with a thin cornea. Methods In this retrospective study,20 high myopic patients (35 eyes) with a thin cornea after Trans-PRK were recruited as study group,20 myopic patiens (32 eyes) with the same amount of cutting depth after femtosecond laser assisted LASIK as control group. Best fit sphere (BFS) of posterior corneal surface before and 12 m after surgery in two groups were analized. Results 12m after surgery, BFS of posterior corneal surface increased by 0.9±9.1μm in Trans-PRK group and by 10.8±8.7μm in femto-LASIK group respectively (P<0.0001). Conclusions Posterior corneal surface keeps in the original position in high myopia patients with a thin cornea following Trans-PRK, which might be safer than femto-LASIK.Part 4 Application of cold patch in relieving pain after Trans-PRKPurpose To investigate the effects of a cold patch on postoperative pain and other relevant reactions to Trans-PRK. Methods In this prospective, randomized controlled study, forty patients (80 eyes) scheduled to undergo transepithelial photorefractive keratectomy for myopia or myopic astigmatism were randomly and equally divided to be treated with iced balanced salt solution during the surgery (washing group) or to wear a postoperative cold patch for 24h. The main outcomes were visual analogue pain score 8,16,24h after surgery, postoperative eyelid edema, conjunctival hyperemia, epithelial healing time, haze, and postoperative best-corrected visual acuity. Results Demographic data and the pain scores during surgery were similar between the two groups. The mean postoperative pain scores of patients in the cold patch group at 8,16, and 24 h were significantly lower than that of the washing group. Scores for postoperative eyelid edema and conjunctival hyperemia in the cold patch group were also lower than in the washing group. Patients in the cold patch group applied fewer painkillers. The epithelium healing time, haze, and early recovery of visual acuity were similar between the two groups. Conclusions Wearing a cold patch after transepithelial photorefractive keratectomy can effectively relieve pain and inflammation and reduce the consumption of painkillers.