Purpose: To report the results of different methods for true corneal power and intraocular lens (IOL) power Calculation in 10 eyes with previous radial keratotomy (RK) with or without astigmatic keratotomy.Methods: In this case series including 10 eyes of 7 patients who had undergone RK with or without astigmatic keratotomy, we firstly determined corneal power using two methods: contact lens method (CLM) and mean keratometry of 3 mm zone in topography. In the next step, 10L power of these eyes was calculated using three formulas including SRK II, SRK T and Holladay II, but the results of Holladay 11formula were used as determinant of 10L power during cataract surgery. Since 1.50 diopter change in 10L power results in 1.00 diopter change in patient's refraction at spectacles plane, we estimated the manifest refraction of these eyes with other formulas for comparing with the results of Holladay 11formula three months after cataract surgery.Results: Postoperative manifest refraction in 8 eyes by using CLM ranged from -3.00 to +2.00 diopter. In both CLM and mean keratometry of 3 mm zone in topography, the amount of hyperopia after cataract surgery with SRK II formula was more than SRK T, and with SRK T was more than Holladay II. Mean spherical equivalent was 0.08 diopter in mean keratometry of 3 mm zone in topography and Holladay 11formula and -0.05 diopter in CLM and Holladay II formula indicating adequate precision of these two methods.Conclusions: It seems that after RK, mean keratometry of 3 mm zone in topography yield a precise estimate of true corneal power as compared to CLM and that Holladay 11formula has the most exact result closer to emetropia in comparison with SRK11and SRKT formulas.

Purpose: Considering the popularity of cataract surgery throughout the country and lack of ultrasound biometry facilities in some regions, this study was designed to compare results of IOL power Calculations by refraction- based formulas with those obtained by ultrasonographic biometry as the gold standard.Patients & Methods: This is a diagnostic clinical trial performed at Farabi Eye Hospital on 100 eyes in 50 cases in whom refraction was feasible during 1999. Each patient underwent refraction, and ultrasound biometry.Thereafter IOL Calculations were done based on the SRK II formula and the two following refraction-based formulas and finally compared.Formula I: PC IOL Power =20+45-MK-------------3+SE-----------3+2 (11.5-VID)MK=Mean keratometry SE = Spherical EquivalentVID= Visible Iris DiameterFormula II:PC IOL= 18±1.6 ( SE)            PowerResults: Mean difference between figures obtained by formula I and biometry was 1.30±0.90. Corresponding figure for formula II was 3.55±1.10 In emmetropic cases (with in ±0.5) of true emmetropia), average PC IOL Calculation based on biometry was 21.20 D. Conclusion: Formula I yields better IOL Calculations than formula II when compared with ultrasound biometry provided that the refractive status of the eye prior to cataract surgery is known.

Purpose: To compare the accuracy of various intraocular lens power formulas for two monofocal hydrophobic foldable lenses, the AcrySof SN60WF and the Tecnis ZCB00. Methods: This retrospective study included 409 eyes from 409 patients who underwent uncomplicated cataract surgery (299 eyes with SN60WF and 110 eyes with ZCB00). Biometry was performed for all eyes with an IOLMaster 700. Predicted refraction from five different IOL power formulas (Barrett Universal II, Haigis, Hoffer-Q, Holladay 2, and SRK/T) was compared to postoperative refraction at one to three months for the following axial length strata: short eyes (<22. 5 mm), medium eyes (22. 5–25. 5 mm), and long eyes (>25. 5 mm). Results: In patients with medium eyes, there were no significant differences in the mean absolute error (MAE) and the percentage of eyes within ±0. 5 D (%±0. 5 D) between both IOLs. In short eyes, although MAE was similar between both lenses, %±0. 5 D was significantly higher for Barrett Universal II in ZCB00 than in SN60WF (P = 0. 01) while Hoffer-Q and Holladay 2 performed equally for both lenses. In long eyes, ZCB00 had a higher MAE than SN60WF for Barrett Universal II, Haigis, and Hoffer-Q. Additionally, in long eyes, the percentage of eyes within %±0. 5 D was significantly higher for SN60WF than ZCB00 for all formulas (P < 0. 001). Conclusion: Although there were no significant differences in the formula accuracy between these two lenses in medium eyes for all formulas and in short eyes for most formulas, the accuracy decreased significantly in long eyes for ZCB00 compared to SN60WF. The effect of IOL model on the postoperative outcomes should be further investigated.

Purpose: To evaluate the ray tracing method's accuracy employing Okulix ray tracing software and thin-lens formulas to calculate intraocular lens (IOL) power using a swept-source optical coherence tomography (SS-OCT) biometer (OA2000). Methods: A total of 188 eyes from 180 patients were included in this study. An OA-2000 optical biometer was used to collect biometric data. The predicted postoperative refraction based on thin-lens formulas including SRK/T, Hoffer Q, Holladay 1, and Haigis formulas and the ray tracing method utilizing the OKULIX software was determined for each patient. To compare the accuracy of approaches, the prediction error and the absolute prediction error were determined. Results: The mean axial length (AL) was 23. 66 mm (range: 19–35). In subgroup analysis based on AL, in all ranges of ALs the ray tracing method had the lowest mean absolute error (0. 56), the lowest standard deviation (SD,0. 55), and the greatest proportion of patients within 1 diopter of predicted refraction (87. 43%) and the lowest absolute prediction error compared to the other formulas (except to SRK/T) in the AL range between 22 and 24 mm (all P < 0. 05). In addition, the OKULIX and Haigis formulas had the least variance (variability) in the prediction error in different ranges of AL. Conclusion: The ray tracing method had the lowest mean absolute error, the lowest standard deviation, and the greatest proportion of patients within 1 diopter of predicted refraction. So, the OKULIX software in combination with SS-OCT biometry (OA2000) performed on par with the third-generation and Haigis formulas, notwithstanding the potential for increased accuracy in the normal range and more consistent results in different ranges of AL.

Purpose: To investigate and optimize the accuracy of aphakic refraction (AR) techniques for secondary intraocular lens (IOL) power Calculation in aphakic children. Methods: Thirty-three aphakic eyes of 18 patients who were candidates for secondary IOL implantation were enrolled in the present study. Axial length (AL) measured by optical biometry was used in the biometric formula (SRK-T, Holladay II, and Hoffer-Q). AR and spherical equivalent (SE) were used in two AR-based formulas (Ianchulev, Leccissotti). True power was calculated based on postoperative SE at three months’ follow-up. Results: Regarding the postoperative SE, 13 (40%) eyes were within ±1. 00 diopters (D) and 22 (66%) were within ±2. 00 D. Median absolute error (MedAE) was predicted to be 4. 4 and 7. 3 D with the use of Ianchulev and Leccissotti formulas, respectively. The corresponding value was 0. 8 D with the biometric formula. All eyes were deemed to have myopic refraction when using the AR-based formulas except one eye with the Ianchulev formula. The coefficient of our modified formula was 1. 7 instead of 2. 01 in the Ianchulev formula. MedAE with the use of new formulae was 0. 5 D and was comparable with the true IOL power (P = 0. 22). Conclusion: Both Ianchulev and Leccissotti formulas resulted in a significant myopic surprise in aphakic children aged between 4. 5 and 14 years. The modified formula proved to determine a more accurate SE that is comparable with biometric formulas.

Purpose: To compare the performance of OKULIX ray-tracing software with SRK-T and Hoffer Q formula in intraocular lens (IOL) power Calculation in patients presenting with cataract. Methods: In this prospective study, 104 eyes of 104 patients with cataract who underwent phacoemulsification and IOL implantation were recruited. Three IOL brands were used and for all eyes, IOL power Calculation was performed using SRK-T, Hoffer Q formula and also OKULIX ray-tracing software. For all patients, axial length and keratometry data was obtained with IOLMaster 500 device and IOL power was determined using Hoffer Q and SRK-T formula. The IOL powers were also calculated using the OKULIX ray-tracing software combined with CASIA ASOCT and IOLMaster 500 device. Optically measured axial length of eyes were inserted to OKULIX software from IOLMaster 500 device, and anterior and posterior tomographic and corneal pachymetry data was imported from CASIA AS-OCT into the OKULIX. The performance of each Calculation methods was measured by subtracting the predicted postoperative refraction from the postoperative manifest refraction spherical equivalent (MRSE). For each of the 3 methods, the mean absolute prediction error was determined, too. Results: The mean value absolute prediction error by OKULIX, SRK-T and Hoffer Q formulas, respectively, were 0. 42 (± 0. 03), 0. 36 (± 0. 02) and 0. 37 (± 0. 02). The mean absolute prediction error by OKULIX had no significant difference between three IOL groups (P ¼ 0. 96), and it was confirmed that there was no meaningful statistically difference in mean absolute prediction error between the OKULIX, SRK-T and Hoffer Q formula. (P ¼ 0. 25). Also in each group of implanted IOLs, all three formulas worked with the same accuracy. The prediction error using OKULIX were within ± 0. 50 diopter in 63. 5% of eyes and within ± 1. 00 diopter in 94. 2% of eyes. Conclusion: OKULIX ray-tracing IOL power measurements provides reliable and satisfactory postoperative results, which are comparable to other 3rd generation formulas of SRK-T and Hoffer Q.

Background& Purpose: IOL power Calculation is one of the current problems in cataract surgery. This study was performed to evaluate the accuracy of six IOL power Calculation formulas in patients undergoing senile cataract surgery.Patients & Methods: This was a clinical trial on 61 eyes in 58 patients with senile cataract.All eyes underwent uncomplicated phacoemulsification or extracapsular cataract extraction and posterior chamber intraocular lens (PCIOL) implantation.Final refraction was performed 6 months after surgery; absolute refractive error was calculated as observed error minus expected error. Eyes were divided into three groups regarding axial length: <22mm, 22-24.5 mm and >24.5mm. Results were analyzed using the ANOVA and LSD tests.Results: Out of 58 cases, 32 subjects (55.0%) were male and (45.0%) were female. Patients age ranged from 35-80 y (mean 65±11.2 y) overall mean absolute error was 1.09±0.67 and there was no significant difference among the six formulas. In eyes of short axial length SRKI yielded better results in terms of final absolute error (P<0.05) However in medium and long eyes no significant difference was observed among the six formulas.Conclusion: Overall, the mean absolute errors of the six formulas were similar. We suggest that the choice of IOL Calculation formulas should be based on availability, familiarity and simplicity; a higher level of caution should be considered in short eyes.

Purpose: To compare the results of the current gold standard, laser interferometry, and keratometry by the IOL-Master, with a newly developed Galilei G6 using raytracing software Okulix for intraocular lens (IOL) power Calculations. Methods: For comparison of the IOL-power Calculation of both devices, we analyzed the difference between the actual one-month postoperative subjective refraction and the theoretically calculated target refraction before cataract surgery. The IOL was selected according to the IOL Master recommendation aiming for emmetropia after surgery. We analyzed the differences of the measurements of the basic biometric data in 205 healthy eyes by each device. Results: Our study included 205 healthy, unoperated eyes from 117 patients (61 women, 56 men) aged 20 to 75 years. Twenty-two eyes of cataract patients were also included in this retrospective study design. The mean difference between the prediction of the postoperative refraction and the refraction actually achieved was 0. 03 D for the IOL Master and –0. 23 D for the Galilei G6. The difference was not statistically significant (P = 0. 059). The difference between the IOL power Calculation of the IOL Master and the Calculation of the G6 was not statistically significant (P = 0. 064). The difference between the predicted refraction of the G6 and the refraction achieved after one month was also not statistically significant (P = 0. 12) and neither was the difference between the predicted refraction of the IOL Master and the achieved refraction (P = 0. 39). The mean axial length was calculated as 24. 21 ± 0. 80 mm using the IOL Master and 24. 27 ± 0. 82 mm using the Galilei G6 device. The mean value regarding anterior chamber depth (ACD) of the IOL master was 3. 46 ± 0. 23 mm and for the Galilei was G6 3. 51 ± 0. 25 mm. When comparing the white to white (WTW) values of the IOL master, it showed mean values of 12. 32 ± 0. 31 and Galilei showed mean values of G6 12. 21 ± 0. 28. All of these differences (between Galileo and IOL Master measurements) were statistically significant (P < 0. 001). Conclusion: Both the laser interferometry/keratometry performed by the IOL Master and the interferometry/raytracing biometry strategy performed by the Galilei G6 demonstrated equal results when executing the IOL power Calculation before cataract surgery in eyes with no prior ocular surgery.

Purpose: To compare AcrySof IQ and Sensar intraocular lens (IOLs) in terms of spherical aberration and contrast sensitivity.Methods: Thirty-four eyes of 34 patients undergoing phacoemulsification cataract surgery were randomly assigned for implantation of AcrySof IQ or Sensar IOLs. Three months postoperatively, bestcorrected visual acuity (BCVA), spherical aberration (with 4 and 6 mm pupil diameters) and contrast sensitivity under photopic and mesopic conditions at spatial frequencies of 1, 2, 5, 10 and 20 cycles per degree (cpd) were determined.Results: Patients included 21 male (61.8%) and 13 female (38.2%) subjects. Mean BCVA was 0.083±0.071 logMAR in the IQ group and 0.145±0.097 logMAR in the Sensar group (P=0.079). Spherical aberration with both 4 and 6 mm pupil diameters in the IQ group was less than in the Sensar group (0.183±0.107 mm vs 0.354±0.138mm, P<0.001 and 0.26±0.096mm vs 0.435±0.152mm, p=0.002; respectively). Contrast  sensitivity was higher in the IQ group at 1, 2, 5, 10 and 20 cpd under photopic conditions and at 1, 10 and 20 cpd under mesopic conditions (P<0.02).Conclusion: AcrySof IQ aspheric IOL seems to have better visual outcomes regarding spherical aberration and contrast sensitivity as compared to spheric Sensar IOL.