Theoretical versus SRK I and SRK II calculation of intraocular lens power

Olsen, Thomas; Thim, Kirsten; Corydon, Leif

doi:10.1016/s0886-3350(13)80734-1

Cited by 45 publications

(24 citation statements)

References 20 publications

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“…The myopic shift seemed to increase with increasing myopic group. When we en- No systematic variation between error and axial length was found, which corresponds to other studies (Olsen et al 1990;McCormack et al 1991). Our results are not directly comparable to the above, as they have divided eyes into groups ac- cording to axial length, whilst we are using refractive status.…”

Section: Discussioncontrasting

confidence: 57%

Accuracy of IOL calculation in cataract surgery

Brandser

Haaskjold

Drolsum

1997

Acta Ophthalmologica Scandinavica

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ABSTRACT. The accuracy of IOL calculation using the SRK I1 formula was studied in 515 cataract extractions with posterior chamber IOLs. All excessively myopic patients (8 patients) and those where we had predicted an emmetropic postoperative result, from a consecutive series of 994 patients, were included. Preoperatively the patients were divided into different groups according to their refractive status and the mean postoperative refraction was calculated in each group. The mean postoperative refraction increased almost linearly with increasing myopic status. The emmetropic group achieved a mean postoperative refraction of -0.6 D, whilst in the most myopic group mean refraction was -1.8 D. We believe that the SRK I1 formula is inaccurate for myopic eyes, and that new formulas are needed, taking into account all those factors that make up the dioptric power of an eye.Key words: cataract extraction -IOL calculation -SRK I1 formula -emmetropic eyes -myopic eyes.Acta Ophthalmol. Scand. 1997: 75: 162-165 uccessful intraocular lens (IOL) im-S plantation in cataract surgery depends partly on the ability to predict postoperative refraction with accuracy, in particular when we now enter the era of bifocal IOL implantation.The second generation empirical formula for implant power calculation, the SRK I1 formula, improved upon the first SRK formula in predicting of IOL power in short and long eyes (Sanders et al. 1988). However, inaccuracy is still found, especially when dealing with excessively myopic eyes, and third generation formulas are now being introduced Hoffer 1993). Earlier studies have not found any statistical correlation between axial length and error prediction (Olsen et al. 1991). Furthermore, there are different opinions concerning the statistical relationship between corneal power and error prediction (McCormack et al. 1991;Olsen et al. 1991).In our clinical practice we had the impression that the highly myopic patients turned out more myopic than predicted compared to the emmetropic patients. To measure the predictive accuracy of our IOL calculations, using the SRK II formula, we compared the results in eyes with different refractive status. Materials and MethodsFrom a consecutive series of 994 patients undergoing cataract surgery between January 1990 and January 1993 wechose those patients with a posterior chamber IOL and a final visual acuity better than 5/50. Preoperatively, patients were divided into six groups according to their refractive status: hyperopic groups (> + 3 D, + 0.5 D to + 3 D); emmetropic group ( tient records. Insufficient information concerning refractive status excluded 91 patients from the study. In the majority of cases an emmetropic refraction of

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Section: Discussioncontrasting

confidence: 57%

Accuracy of IOL calculation in cataract surgery

Brandser

Haaskjold

Drolsum

1997

Acta Ophthalmologica Scandinavica

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“…21,22 If not corrected for the axial length dependence, the IOL power calculation formula becomes biased and gives erroneous predictions in long and short eyes. 23,24 The preoperative ACD has also been described as a predictor for some time, 22,25,26 and is included in the ACD algorithms of several modern IOL power calculation formulas. An example is the Haigis formula, 7 which uses the following regression approach to the ACD prediction:…”

Section: Discussionmentioning

confidence: 99%

Prediction of the effective postoperative (intraocular lens) anterior chamber depth

Olsen

2006

Journal of Cataract and Refractive Surgery

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223

111

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The postoperative ACD was significantly correlated with and hence predictable by a 5-variable regression method incorporating the preoperative axial length, ACD, keratometry reading, lens thickness, and refraction as the most significant variables. The statistical relationship can be used to create a new ACD prediction algorithm to incorporate in a modern "thick lens" IOL power calculation formula with significant improvement in the accuracy of the refractive predictions as a result.

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“…Effective visual rehabilitation after cataract surgery also depends on accurate intraocular lens power calculations which are primarily derived from normative ocular biometric data [15][16][17][18][19]. Therefore, it is important to understand the factors that have an influence on the CCT.…”

Section: Research Articlementioning

confidence: 99%

Central Corneal Thickness: Important Considerate in Ophthalmic Clinic

Thakur¹

2017

Austin J Clin Ophthalmol

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Results:The mean SE, KM and CCT of the patients under the study were (-) 0.47 ± 2.26,43.79 ± 1.18D and 528.41 ± 19.1µm. Mean CCT was higher in age group C (46 to 60 yrs) than other groups (p = 0.008) but no impact was found on increasing age after regression analysis. CCT was not affected by gender (p = 0.168). Mean CCT for Myopic was found to be 522.87±18.03µm which was lower compared to in Hypermetropic (536.39 ±17.753µm) (p = <0.001). There was a positive correlation between CCT and SE (r = 0.520, p = <0.001). However KM showed negative correlation with CCT (r = -0.288, p = <0.001). Conclusion:From above study we concluded that CCT was related to age, refractive status and keratometry but not to sex.

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Theoretical versus SRK I and SRK II calculation of intraocular lens power

Cited by 45 publications

References 20 publications

Accuracy of IOL calculation in cataract surgery

Accuracy of IOL calculation in cataract surgery

Prediction of the effective postoperative (intraocular lens) anterior chamber depth

Central Corneal Thickness: Important Considerate in Ophthalmic Clinic

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