[Calculation of corneal curvature after laser in situ keratomileusis for correction of myopia].

OBJECTIVE: To describe and evaluate a refraction-derived method and a clinical-derived method to calculate the correct corneal curvature for intraocular lens (IOL) power calculations after laser in situ keratomileusis (LASIK) and to compare the results to the commonly used history-derived method. METHOD: Retrospective analysis of consecutive case treated with LAIK clinically. We measured pre-LASIK and post-LASIK spectacle refraction, pre-LASIK and post-LASIK K readings in each patient. We then calculated pre- and post-LASIK refraction at the corneal plane and the amount of correction obtained by the refraction surgery. Patients were divided into two groups. Group I was used to establish the two different formulas for the refraction- and clinical-derived methods. The values obtained with these two methods were compared with the K by history-derived method (Kc. hd) in group II to validate the results. RESULTS: The K values calculated using the refraction-derived method and clinical-derived method were correlated significantly with that obtained from Kc. hd. CONCLUSION: The calculation of corneal curvature for intraocular lens (IOL) power calculation after LASIK can use the refraction- and clinical-derived methods instead of history-derived method when some refractive parameters are not available.

Evaluation and comparison of various renal function tests in elderly patients with chronic kidney disease / 中华老年医学杂志

Objective To find out whether the levels of serum creatinine and urea,creatinine clearance rate and GFR estimated by using different equations correlate with the exact measurement of GFR with ~(99m)Tc-DTPA in elderly patients with chronic kidney disease.Methods Renal function was determined by using ~(99m)Tc-DTPA technique in 83 elderly patients aged 65—96 years.Blood and urine tests were done at the same time.Estimated clearance was determined by using the equations of Cockcroft-Gauh,MDRD(modification of diet in renal disease)predigestion and MDRD seventh,and the correlation coefficients between the above parameters and ~(99m)Tc-GFR were determined.Veracity for the diagnosis of renal dysfunction was calculated by using receiver operating characteristic(ROC) curves.Results Cockcroft-Gault formula(r=0.833),MDRD predigestion formula(r=0.811), MDRD seventh formula(r=0.803),creatinine(r=-0.672),Ccr(r=0.632),urea(r=-0.612), and albumin(r=0.444)were correlated significantly with ~(99m)Tc-GFR in this sequence.If GFR 30, 40,50,60ml/min were defined respectively as renal impairment thresholds and areas under the curve (AUC)were compared,the best parameter for estimation of GFR was the Cockcroft-Gault formula. Then MDRD predigestion formula and MDRD seventh formula,creatinine and Ccr were less accurate in all different renal dysfunction thresholds.Conclusions The Cockcroft-Gault equation seems to be the best formula available for GFR estimation,the two equations of MDRD are the second,creatinine is the third,Ccr and urea are the last.