ABSTRACT
Background The surgery for femtosecond laser created laser in situ keratomileusis(LASIK)flaps has made great progression recent year,but the postoperative corneal wound healing and regeneration of nerve fibers after surgery are closely concerned.Objective This study was to compare and analyze the clinical outcomes between FEMTO LDV femtosecond laser flap and mechanical microkeratome Hansatome flap in LASIK.Methods A prospective case-controlled study was designed.The serial 38 myopic eyes of 38 patients were included from March through July,2010 in Henan Armed Police Force General Hospital.The patients were randomized into FEMTO LDV femtosecond laser assisted flap group(20 patients/20 eyes)and mechanical microkeratome Hansatome assisted flap group(18 patients/18 eyes)with the matched age,gender and refraction of spherical equivalent.HRT Ⅲ examinations were performed before surgery,1 week,1 month and 3 months after surgery to compare the morphological changes atthe center and margin of the flaps,and evaluate the similarities and differences of cellular morphology after surgery between the two approaches.Written informed consent was obtained from each patient prior to this medical trial.Results The best corrected visual acuity was ≥ 1.0 and the refract diopter was similar in both groups(+0.21 D±0.48 D and-0.04 D±0.54 D)1 month after LASIK.The corneal thickness was insignificant increased in the first week after LASIK,and the density of shallow stromal cells was decreased in 1 week,1 month and 3 months compared with pre-operation in the femtosecond laser assisted flap group(t =-27.99,-25.49,-28.87,P ＜ 0.01).In the Hansatome assisted flap group,significantly thickened corneal epithelium was seen in the first week after LASIK compared before LASIK(56.73 μm±2.47 μm versus 51.16 μm±1.11 μm)(t=9.29,P＜0.05),and the density of shallow stromal cells was decreased in 1 week,1 month and 3 months compared with pre-operation in the Hansatome assisted flap group(t =-17.57,-14.13,-19.63,P =0.00).The density of high reflective interface particles in cornea was lower in 1 week,1 month and 3 months after LASIK in the femtosecond laser assisted flap group than that in the Hansatome assisted flap group,showing significant differences between them(t =-13.505,-11.900,-14.084,P＜0.01).The active stromal cells were seen beneath the interface in both groups in the first week and gradually decreased after that time.Intact corneal nerve fibers were found in the femtosecond laser assisted flap group,but those in the Hansatome assisted flap group were shorter and smaller 3 months after LASIK.At 3 months after surgery,the flap margin showed stromal higher reflection and irregular secondary fibrosis in the femtosecond laser assisted flap group,and in contrast,the flap margin had the appearance of a unclearly identified fibrotic scar in the Hansatome assisted flap group.Conclusions Compared with the LASIK and Hansatome assisted flap,the LASIK with FEMTO LDV flap shows earlier nerve fiber regeneration and greater fibrotic scarring,which imply a good wound healing process in the LASIK with FEMTO LDV flap.
ABSTRACT
<p><b>BACKGROUND</b>Astigmatism is one of the most significant obstacles for achieving satisfactory visual function. This study was to evaluate the influence of astigmatism on contrast sensitivity (CS) and higher-order aberrations.</p><p><b>METHODS</b>CS, accommodation response and wavefront aberration were measured in 113 patients with astigmatism, aged 18 - 36 years. Both single and binocular visual performance were examined under four lighting conditions: photopia, photopia with glare, scotopia and scotopia with glare respectively. Accommodation response was classified as normal, abnormal and low. The contribution of the power and axis of astigmatism to CS, accommodation response and wavefront aberration was analyzed.</p><p><b>RESULTS</b>As the dioptric power of astigmatism increased, the loss of CS spatial frequency changed from high to intermediate, and then to low frequency. CS scores varied at different illuminance levels, descending in the following sequence: photopia, photopia with glare, scotopia, and scotopia with glare. However, the normal accommodation group showed better CS values under photopia with glare than without glare. The range of influenced direction of sine-wave gratings remained mostly at the meridian line of high dioptric power, which would be expanded when optical accommadation attenuated. The patients with symmetrical astigmatism got higher CS scores with binoculus vision than with dominant eye vision, while the patients with asymmetrical astigmatism did this only at scotopia with glare. Among higher-order aberrations, coma aberration, secondary coma aberration and the total higher order aberration were influenced by astigmatism, all of which rising with the power of astigmatism increased.</p><p><b>CONCLUSIONS</b>Reducing astigmatism might improve the performance of visual function. Not only the power of astigmatism should be cut down, but also the binocular axes should be made symmetrically.</p>