ABSTRACT
OBJECTIVE: To observe the predictability of corneal flap creation with the FEMTO LDV femtosecond laser and analyze preliminarily the factors correlating to the thickness and diameter of the flap . METHODS: It was a study of serial cases. 260 eyes of 130 consecutive patients were treated with the FEMTO LDV. The eyes were assigned to two groups according to intended flap thickness, 110 µm (208 eyes) and 90 µm (52 eyes). Intended flap diameter varied from 8.5 to 9.5 mm. Difference analysis of flap diameter and intended diameter as well as flap thickness and intended thickness were made. The data was analyzed with SPSS to sum up a multiple stepwise regression formula that could express their quantitative relationship. RESULTS: The 90 µm flap group had a average flap thickness of (95.12 ± 7.65) µm, while for the 110 µm group the average flap thickness was (104.81 ± 3.09) µm. The difference between right and left eyes was not statistically significant (t(110 µm) = -1.223, t(90 µm) = -1.343, P > 0.05). Corneal flap thickness was inversely correlated with flap diameter (r(110 µm) = -0.143, r(90 µm) = -0.315, P < 0.05), but was not related to preoperative patient age, corneal thickness, keratometric value K or intraocular pressure (r(110 µm) = -0.160, 0.054, -0.011, -0.363; r(90 µm) = 0.024, 0.074, -0.212, -0.434, all P > 0.05). Corneal flap diameter was positively correlated with preoperative corneal keratometric value K and thickness (P < 0.001, P < 0.05). Multiple stepwise regression analysis showed flap diameter was an influencing factor for flap thickness. Preoperative corneal keratometric value K and thickness were influencing factors for flap diameter. CONCLUSIONS: The LASIK flap creation with the FEMTO LDV laser has relatively good predictability. Flap diameter is an influencing factor for flap thickness.
Subject(s)
Cornea/surgery , Keratomileusis, Laser In Situ/methods , Myopia/surgery , Surgical Flaps , Adolescent , Adult , Cornea/anatomy & histology , Corneal Transplantation , Female , Humans , Male , Young AdultABSTRACT
OBJECTIVE: To study the incidence and risk factors of intraocular pressure (IOP) elevation in patients who underwent vitreoretinal surgery. METHODS: Data for 422 patients (446 eyes) who underwent vitreoretinal surgery from June 2005 to June 2007 were retrospectively analyzed. IOP was measured before surgery and on day 1, 2, 3, 7-14 after surgery with Goldmann applanation tonometer. Ocular hypertension was defined as IOP 25 mmHg or more. All factors were analyzed for association with Ocular hypertension. RESULTS: 232 of the 422 patients were female. 190 were male. The IOP was elevated significantly in 185 eyes (41%) after surgery within 2 weeks. Among them the IOP occurred mostly in day 1 (152 eyes, 82%). The rate of IOP elevation with intraocular tamponade of C3F8 or silicone oil was 53% or 55%, the difference being not statistically significant (P>0.05). The incidence of high IOP in C3F8 injection group and silicone oil injection group were statistically higher than simple pars plana vitrectomy group (P<0.01). The risk factors of ocular hypertension include C3F8 injection (chi2=37.82, P<0.01), silicone oil injection (chi2=27.84, P<0.01), lentectomy (chi2=8.98, P<0.01), scatter endolaser (chi2=7.41, P<0.01), diabetes (chi2=12.12, P<0.01) and increasing patient age (chi2=7.07, P<0.01). CONCLUSION: IOP elevation was a common complication of vitreoretinal surgery. The risk factors of ocular hypertension include C3F8 injection, silicone oil injection, lentectomy, scatter endolaser, diabetes and increasing patient age.
Subject(s)
Ocular Hypertension/etiology , Postoperative Complications/etiology , Vitrectomy/adverse effects , Adolescent , Adult , Aged , Aged, 80 and over , Female , Humans , Incidence , Intraocular Pressure , Male , Middle Aged , Retina/surgery , Risk Factors , Vitreous Body/surgery , Young AdultABSTRACT
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.