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@#AIM: To compare the accuracy of Barrett Universal Ⅱ, Haigis and modified Wang-Koch SRK/T formulas in calculating intraocular lens(IOL)power in eyes with long axial length(AL).<p>METHODS: Eyes were divided into three AL groups as follows: 26.0 to 28.0mm(group A), 28.0 to 30.0mm(group B), and 30.0mm or more(group C). All eyes underwent phacoemulsification cataract surgery. In the 3mo after operation, IOL powers that would have resulted in emmetropia were calculated according to results of subjective refraction. The predictive error(PE)and absolute error(AE)of each formulas were calculated and compared and the factors(AL, keratometry value, the anterior chamber depth)associated with PEs were analyzed.<p>RESULTS: The average PE of Barrett Universal Ⅱ, Haigis and modified Wang-Koch SRK/T formulas were 0.37±0.78D, 0.77±0.88D and 0.36±0.82D respectively. In groups A and B, the PEs and AEs of three formulas were not statistically significant(<i>P</i>>0.05). However, in group C, the PEs and AEs of Barrett Universal Ⅱ and modified Wang-Koch SRK/T formula were significantly less than Haigis formula(<i>P</i><0.05). The PEs of Haigis formula in cataract eyes with long AL was affected by AL and keratometry value, whereas the PEs of Barrett Universal Ⅱ and modified Wang-Koch SRK/T formula was not affected by AL.<p>CONCLUSION: In eyes with an AL of 26.0 to 30.0mm, all three formulas are acceptable. In eyes with AL of 30.0mm or more, the accuracy of Barrett Universal Ⅱ and modified Wang-Koch SRK/T formula are better than Haigis formula.
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@#AIM:To study the variation of ocular biometric parameters and their relationship before and after phacoemulsification in cataract patients with over-long axial length.<p>METHODS:A total of 44 cases(61 eyes)were collected from September 2013 to March 2015 in Xuanwu Hospital which had underwent phacoemulsification and intraocular lens(IOL)implantation. The study contained 29 eyes of 20 patients with over-long axial length and 32 eyes of 24 patients with normal axial length. Before cataract surgery, the optical biometric measurements had been measured by IOL Master. And 3mo after surgery, the ocular biometric parameters had been recorded by IOL Master and ultrasound biomicroscopy(UBM). The changes and correlation of biometric parameters was performed using the SPSS software(version 17.0).<p>RESULTS: Pearson correlation analysis showed there was no correlation between postoperative anterior chamber depth and age, preoperative axial length, or preoperative corneal curvature in over-long axial length group(<i>P</i>>0.05). There was a positive correlation between the postoperative anterior chamber depth and the preoperative anterior chamber depth(<i>r</i>=0.402, <i>P</i>=0.031). Compared with the preoperative biometric parameters in over-long axial length group, axial length shortened, corneal curvature increased, anterior chamber depth deepened after surgery, and the difference was statistically significant(<i>P</i><0.05). However, in the normal axial control group there was no correlation between the postoperative anterior chamber depth and age, preoperative axial length, or preoperative anterior chamber depth(<i>P</i>>0.05). There was a positive correlation between the postoperative anterior chamber depth and the preoperative corneal curvature(<i>r</i>=0.538, <i>P</i>=0.001). And in normal axial control group, the axial length was significantly shorter than that before surgery(<i>P</i><0.05). The anterior chamber depth was significantly increased compared with the preoperative(<i>P</i><0.05), and the corneal curvature was unchanged(<i>P</i>>0.05). The percent change of corneal curvature was statistically significant between two groups(<i>P</i><0.05), and the percent change of corneal curvature in over-long axial length group was bigger than normal axial length group. There was no significant difference in the percent change of axial length and anterior chamber depth(<i>P</i>>0.05). <p>CONCLUSION: In cataract patients with over- long axial length, postoperative axial length shortened, and postoperative corneal curvature increased. A certain number of degrees should be added when calculating the degree of intraocular lens in order to obtain better postoperative visual acuity. The prediction of postoperative anterior chamber depth in cataract patients with over-long axial length has complexity and unpredictability of individual differences, and requires further research.
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AIM: To compare the accuracy of intraocular lens(IOL)power calculations by using five formulas(Haigis, SRK-T, Hoffer Q, Holladay-1, SRK-Ⅱ)in eyes with long axial lengths in order to improve the accuracy of predicating IOL powers.METHODS: Fifty-one eyes of 51 cases of age-related cataract and with mild long axial(24.5mm27mm) were collected who`s optical biometry were performed by the Zeiss IOL Master500 before operation.They underwent regular phacoemulsification and posterior chamber IOL implantation.The actual postoperative refraction was measured with the methods of phoropter and subjective optometry 3mo after surgery.Then we compared the differences of the predicted and actual postoperative refraction of the five formulas in each group.RESULTS: In the mild axial lengths cases, the differences between SRK Ⅱ formula and the other four formulas were statistically significant (P0.05).In the moderate and severe long axial lengths cases, the differences between SRK Ⅱ formula and the other four formulas were statistically significant (P0.05).The differences of all the five formulas between the two groups were statistically significant (P<0.05).CONCLUSION: In the mild axial lengths cases, Haigis, SRK-T, Hoffer Q, Holladay-1 performed well.In the moderate and severe long axial lengths cases, Haigis, SRK-T and Holladay-1 performed better than other formulas.The accuracy of all the five formulas decreases as the axial length getting longer.
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Efficacy of intraocular lens power calculation formulas in a subset of Indian myopic population. Retrospectively reviewed 43 patients who underwent phacoemulsification with high axial length (AL) (>24.5 mm, range 24.75‑32.35 mm). The power of the implanted intraocular lens (IOL) was used to calculate the predicted post‑operative refractive error by four formulas: Sanders‑Retzlaff‑Kraff (SRK II), SRK/T, Holladay 1, and Hoffer Q. The predictive accuracy of the formulas was analyzed by comparing the difference between the “actual” and “predicted” postoperative refractive errors. Repeated measures analysis of variance (ANOVA) tests were done to have pair‑wise comparisons between the formulas and P < 0.05 was considered significant. A subcategory of axial length 24.5‑26.5 mm was also tested. Holladay 1, Hoffer Q and SRK/T formulas showed a slight tendency toward resultant hyperopia, with mean error of +0.24 diopters (D), +0.58 D, and +0.92 D, respectively. The Holladay 1 formula provided the best predictive result overall.