[Evaluation of quality of vision in early stage after sub-bowman keratomileusis].

OBJECTIVE: To assess the quality of vision in the early stage after sub-bowman keratomileusis (SBK) for the correction of moderate and high myopia. METHODS: Retrospective case series. Sixty eight myopic eyes of 35 consecutive patients in Chongqing Medal Eye Institute from May to November 2011 were enrolled in this study. All patients were evaluated at 2 weeks, 1 and 3 months postoperatively. The main measurements included visual acuity, corneal and total optical wavefront aberration, photopic and mesopic contrast sensitivity. RESULTS: The median values of preoperative uncorrected central visual acuity (UCVA) and best corrected visual acuity (BCVA) were 0.05 and 1.00, respectively. The median value of postoperative UCVA was 1.20. There was no significant difference between the preoperative and postoperative anterior corneal total aberration (F = 0.712, P > 0.05). Compared with preoperative value (0.47 ± 0.17)µm, the corneal high orders aberrations in 2 weeks after SBK (1.37 ± 0.72) µm increased by 3 times. The total optical aberrations in 2 weeks after SBK (0.99 ± 0.58) µm decreased to one-eighth of preoperative measurements (8.26 ± 2.93) µm. Compared with preoperative value (0.30 ± 0.12)µm, the total high order aberrations in 2 weeks after SBK (0.46 ± 0.19) µm increased by 1.5 times. Although photopic and mesopic contrast sensitivity fluctuated mildly after SBK, the measurements did not decline significantly. Compared with preoperative data, mesopic contrast sensitivity at 3 months increased 0.294 (F = 20.88,P < 0.01) and 0.296 (F = 13.64, P < 0.01) at 12 and 18 c/d, respectively. CONCLUSION: Patients could obtain good quality of vision at the early stage after SBK.

[The early post-operative wound healing mode study of the rabbit cornea after flap-free epiploic laser in-situ keratomileusis].

OBJECTIVE: To evaluate the wound healing mode of rabbit corneal epithelium after Epi-LASIK(epiplolic laser in-situ keratomileusis) and Flap-free Epi-LASIK(Flap-free epiploic laser in-situ keratomileusis). METHODS: Twenty-four New Zealand white rabbits (48 eyes) were randomly divided into four groups. There were six rabbits in every group, which were randomly treated with Epi-LASIK in one eye and Flap-free Epi-LASIK in the other by VISX20/20 excimer laser. Other three rabbits (6 eyes) without any treatment were used as control. The corneal epithelium wound healing mode was observed at 1, 2, 4, 7 days after surgery by light microscope and electron microscope. The number of keratocytes cells in the central anterior stroma were counted by hematoxylin-eosin-stained. The expression of basic fibroblast growth factor (bFGF) in corneal stroma were assessed by Immunohistochemistry staining. Cornea stromal cell apoptosis was evaluated by terminal deoxyribonuc-1-eotidyl transferase-mediated deoxynuridine triphosphate nick end labeling (TUNEL) assay.All the data was analysised by t-test to evaluate the different of wound healing mode after Epi-LASIK and Flap-free Epi-LASIK. RESULTS: The findings of light microscope and electron microscope investigation demonstrated that, at the first day after surgery, there was one layer of neogenesis of the corneal epithelial cells covering the area of surgery in Flap-free Epi-LASIK specimens. It would increase gradually after 7 days. At the first day after the surgery, the base membrane of the corneal epithelium was tightly attached to the stroma in Epi-LASIK specimens. At the second day after the surgery, there was edema observed on the epithelium flap in the Epi-LASIK specimens. There were more keratocytes cells found at 4 days after surgery in Flap-free Epi-LASIK group (33.85 +/- 3.39) than that in Epi-LASIK group (t = -2.315, P < 0.05). The expression of bFGF in Flap-free Epi-LASIK group at 2, 4 days after surgery were 101.75 +/- 8.07 and 110.56 +/- 9.00, which were more than Epi-LASIK (t = -2.339, -2.396, P < 0.05). There was less keratocyte apoptosis cells in Flap-free Epi-LASIK group than Epi-LASIK group at 2, 4 days after surgery (t = 3.332, 2.989, P < 0.05). CONCLUSIONS: Due to the specific way of the epithelium removal resulting in the more rapid epithelium healing, the Flap-free Epi-LASIK technique is advantageous in reducing the stimulative symptoms after the surgery. It's also beneficial for the corneal wound healing.

[The structure and viability analysis of corneal epithelial flap in the rabbit cornea after Epi-LASIK].

OBJECTIVE: To evaluate the changes of ultrastructure and viability in the rabbit corneal epithelial flap after Epi-LASIK (epiploic laser in-situ keratomileusis) surgery and its effect on keratocyte apoptosis and proliferation of peripheral corneal epithelium (out of corneal epithelial flap). METHODS: Fifty-eighty eyes of 29 New Zealand rabbits were used, Epi-LASIK was performed in 28 eyes and Photorefractive keratectomy (PRK) was carried out in 24 eyes. treated-eyes were randomly divided into four groups and were sacrificed at 1, 3, 5, 7 days after surgery, six eyes without treatment were served as blank controls. Histological structure from The specimens of Epi-LASIK and controls eyes were assessed by light, transmission electron microscopy; epithelial cells viability were assessed by enzyme-histochemistry and Immunohistochemistry staining (proliferating cell nuclear antigen, PCNA) were performed to detect proliferation of peripheral corneal epithelial cells. Apoptotic cells were detected by TUNEL assay (TdT-mediated dUTP nick-end labeling) from the specimens of Epi-LASIK and PRK. RESULTS: The study from Transmission electron microscopy demonstrated that epithelial flap separated by KM5000D type epikeratome retained its typical stratification and integrity and the basement membrane including lamina densa and lamina lucida were compaginated with stroma. The expression of ATP enzyme, G-6-P enzyme from epithelial flap to peripheral epithelium of Epi-LASIK-treated eyes were (79%, 58%, 69%, 86%), (79%, 63%, 77%, 97%) at 1, 3, 5, 7 days after surgery respectively. There was no statistically significant difference in the cell Viability and the number of PCNA in peripheral epithelial cells among four Epi-LASIK groups and control group. At 1 day after surgery, no difference in TUNEL positive cells were seen between specimens of Epi-LASIK (3.429 +/- 1.693) and PRK (3.796 +/- 1.998); At 3, 5, 7 days, there was a significant difference in the number of keratocyte apoptosis in PRK compared to Epi-LASIK specimens. CONCLUSIONS: Epithelial flap separated by KM5000D type epikeratome retained its typical stratification and integrity. The flap keeps high viability and no peripheral epithelial cell proliferation and therefore it may play a role in the inhibition of keratocyte apoptosis.

[An analysis about the safe range of thickness of the residual corneal stroma bed after LASIK].

OBJECTIVE: To ascertain the safe range of thickness of the residual corneal stroma bed and the length of stable time after LASIK operation. METHODS: Two hundred and twenty seven eyes were randomly selected from cases treated with LASIK in 2000. The posterior curvature of cornea was measured by Obscan II preoperatively and 1, 2, 3, 6 months, 1 year and 2 year postoperatively. These data were compared and analyzed. RESULTS: Ectasia of central corneal posterior surface was detected at different degrees in all cases at the early postoperative period after LASIK. Ectasia was more prominent in eyes with thinner corneal stroma bed (< 300 microm). In eyes with thicker corneal stroma, ectasia remained stable or reverting obviously during the first year. The posterior curvature of cornea had no significant difference between 1 year and 2 year after operation in all cases. CONCLUSIONS: Ectasia of corneal posterior surface presents in the early postoperative period after LASIK. It is safer to reserve more than 300 microm of the corneal stroma bed. The posterior curvature of cornea of all cases remains stable after one year postoperatively.

[An analysis of measurement error in Orbscan topography system].

OBJECTIVE: To discuss the measurement error and the influence factor of Orbscan Topography to provide more accurate data for clinical application. METHODS: Orbscan Topography System and A-scan ultrasonography were used to measure the corneal thickness and anterior chamber depths pre-operatively and post-operatively, including 200 cases (400 eyes) undergoing laser in situ keratomileusis (Lasik) and 50 cases (100 eyes) undergoing photorefractive keratectomy (PRK). The curvature of posterior corneal surface was measured by Orbscan topography before and after the operations, and the result of measurement was compared. RESULTS: Pre-operatively, the value of corneal thickness was (18.83 - 24.29) microm lower measured by Orbscan topography than that by A-ultrasonography, and post-operatively the value was (56.32 - 139.52) micro m lower than that by A-ultrasonography. The postoperative value was obviously higher than the pre-operative one. The value of central anterior chamber depth was (0.16 - 0.25) mm lower measured by Orbscan system than that by A-ultrasonography pre-operatively and post-operatively. There was no clinical significance. The difference in the comparison of posterior corneal surface curvature before and after Lasik was -0.60 D measured by Orbscan System. The difference in the comparison of posterior corneal surface curvature before and after PRK was -0.51 D in the lower diopter group and -1.12 D in medium diopter group. CONCLUSIONS: It is necessary to improve the accuracy of Orbscan Topography System. The Haze and the change of anterior corneal surface curvature after Lasik and PRK are the main causes of measurement error in Orbscan Topography System. Clinically, it is an un-negligible important problem in the measurement of Orbscan system.