Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.2 (focal adhesion kinase)
 44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intraocular lens power calculation is increasing in use in the United Kingdom. Primarily to avoid anisometropia, intraocular lens power calculation may also be used to provide the patient with three rather than two working distances, but to achieve this greater accuracy of IOL power calculation is required. Using the SRK regression formula, three groups of patients have been studied. The effect of inaccurate use of the formula of choice is shown and the need to modify the 'A' constant to account for variation both in technique and biometry equipment emphasised. The variation in results due to inaccurate biometry are statistically assessed. Accuracy of IOL power calculation requires consistency but not absolute accuracy in biometry. No ocular factors were found to affect the accuracy of IOL power calculation.
 ...
PMID:Factors affecting intraocular lens power calculation. 347 92

IOL power prediction was performed by streak retinoscopy on the operating table after taking the previous refractive status of the patient into consideration. In 180 eyes posterior chamber lenses were implanted after determining the power of the IOL by retinoscopy on the table and selecting a suitable lens. The method though not so accurate as A scan ultra sonography and use of the SRK formula and the Colebrander formula is a good substitute to these methods particularly for avoiding high post operative refractive errors.
 ...
PMID:IOL power determination by retinoscope. 350 80

The postoperative refraction prediction was evaluated in 99 patients with a 19.0-diopter standard power anterior chamber lens using a theoretical, computer-assisted method based on Gaussian optics and an empirical intraocular lens calculation method based on the SRK formula. Both the theoretical and the empirical predictions accorded with the observed values in the near emmetropia region. In the prediction of ametropia, the SRK method showed a tendency to predict refractions that were lower than the actual values in hyperopic eyes and higher than the actual values in myopic eyes. The bias of the SRK method may be due to the use of an erroneous refraction factor that converts the ametropia to the deviation in implant power from the emmetropia power. By introducing an individual refraction factor, the accuracy of the SRK method approached that of the theoretical method.
 ...
PMID:Theoretical, computer-assisted prediction versus SRK prediction of postoperative refraction after intraocular lens implantation. 357 70

Several different formulas are available for preoperative calculation of the required implant power for a desired postoperative refraction. However, the application of both theoretical and statistically derived regression formulas to the new generation of soft intraocular lens implants poses several difficulties. In this paper the calculation of an A constant for a specific intraocular hydrogel lens implant, as well as the derivation of a universal theoretical formula, is described. The theoretical formula can be applied to other implant styles with various optical configurations and composed of different biomaterials. The SRK and theoretical formulas have been applied retrospectively to a series of patients receiving an intraocular hydrogel lens implant. A comparison shows that both perform satisfactorily in predicting the desired postoperative refraction.
 ...
PMID:Intraocular lens calculation formulas for new intraocular lens implants. 362 16

The aphakic refraction was predicted from preoperative and postoperative keratometry and axial length determinations in 43 patients subjected to cataract extraction without intraocular lens implantation using a theoretical and an empirical (Sanders, Retzlaff, Kraff [SRK]) method of calculation. The error (mean +/- SD; observed value minus expected value) of the theoretical vs the empirical method was 0.02 +/- 0.76 diopters (D) vs 0.66 +/- 0.72 D, respectively, when the preoperative data were used in the calculations, and 0.21 +/- 0.80 D vs 0.84 +/- 0.79 D, respectively, when the postoperative data were used in the calculations. The mean error was significantly different from zero (predicted values were lower than observed values) for the SRK method but not for the theoretical method. The mean error of the SRK method could be eliminated by adjusting the offset constant in the regression formula.
 ...
PMID:Theoretical vs empirical prediction of aphakic refraction. 363 11

Sixty-seven patients were examined 3 to 5 1/2 (mean 4) months after intended extracapsular cataract extraction with implantation of the 3 M, style 83, posterior chamber lens. A visual acuity greater than or equal to 0.5 was recorded in 58 (86.6%) of the patients. The complications were: one (1.5%) case of acute iritis, one case of pupillary capture and two (3.0%) cases of capsulotomy-requiring early secondary cataract. There were no posterior segment complications. None of the patients were treated with anti-glaucomatous medication, and none had intraocular pressure above 20 mmHg. Pre-operatively, biometry was performed, and the SRK-formula was employed in estimating the post-operative spherical equivalent refraction: The actually measured refraction differed less than 2 diopters from the predicted refraction in 84.5% of the cases.
 ...
PMID:Complications and visual outcome 4 months after extracapsular cataract extraction with implantation of posterior chamber lenses. A prospective clinical study. 381 64

The postoperative refraction of the eye after intraocular lens (IOL) implantation is an important aspect of the quality of aphakia correction. The postoperative refraction cannot be guessed with consistent accuracy as the refractive power of an eye is multifactorial. Calculation of IOL power is based upon measurements of corneal curvature and axial length and an estimation of postoperative anterior chamber depth. There are a number of formulae available for the calculation of IOL power. The optical formulae, of which those of R. D. Binkhorst are the most popular, give results which are very similar and which all differ from the mathematical regression SRK formula by the indication of a stronger IOL power for short eyes. A statistical analysis of postoperative results confirms that the R. D. Binkhorst formula gives the author an over-powered IOL for short eyes when calculated for emmetropia but not when calculated for planned ametropia. Results with the R. D. Binkhorst formula will be improved by the modification of the anterior chamber depth according to the axial length. Both formulae give satisfactory results for the range of axial lengths commonly encountered in clinical practice. Whichever formula is used, it is important for each surgeon to analyse postoperative results and to modify the selection of IOL power according to this feedback to correct for consistent errors of instrumentation or technique.
 ...
PMID:Intraocular lens power calculation--the selection of formula. 386 11

Out of 2,000 calculated and implanted posterior chamber lenses with the convex side posteriorly we selected all patients with intraocular lenses having a power of 9 to 11 or 29 to 30 diopters. We found significant differences in the results of IOL-power calculation, using the SRK-formula or the theoretical mathematic formula. Using the distance between the corneal vertex and the first principal point of the plano convex lens as the anterior chamber depth we find that the theoretical formula is the most accurate in calculating the IOL-power of higher hypermetropic eyes.
 ...
PMID:Posterior chamber lenses with convex side posteriorly--the calculation of dioptric power and results. 390 34

The refractive results of 43 consecutive triple procedures (transplant, cataract extraction, and lens implant) performed by one surgeon were analyzed. Twenty-one out of 43 eyes achieved refractive errors within 2 diopters (D) of emmetropia. The mean refractive error was -1.79 D, and the mean corneal astigmatic error was 2.75 D. Seventy percent of the eyes achieved 20/40 or better corrected acuity. Forty-four percent had 20/80 or better uncorrected acuity. Using the average postoperative keratometry readings from other recent transplant cases and an updated A constant in the SRK regression formula would have placed 39 of 43 eyes (91%) within 2 D of emmetropia with a mean refractive error of -0.07 D. The use of recent keratometry readings in a multiple regression formula is recommended to improve refractive results with the triple procedure.
 ...
PMID:Intraocular lens powers used in the triple procedure. Effect on visual acuity and refractive error. 390 37

The SRK Regression formula for intraocular lens power calculation was used to predict postoperative emmetropia in two series of routine cataract operations using different posterior chamber lenses. More accurate results were obtained when the intraocular lenses were used in one dioptre steps. Some practical points about the routine use of ultrasound are made.
 ...
PMID:Intraocular lens power calculation using the SRK formula: a clinical study. 390 47


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>