Adoption, implementation, definitions, and future of blockchain technology in ophthalmology

In this era of cutting-edge research and digitalization, artificial intelligence (AI) has rapidly penetrated all subspecialties, including ophthalmology. Managing AI data and analytics is cumbersome, and implementing blockchain technology has made this task less challenging. Blockchain technology is an advanced mechanism with a robust database that allows the unambiguous sharing of widespread information within a business model or network. The data is stored in blocks that are linked together in chains. Since its inception in 2008, blockchain technology has grown over the years, and its novel use in ophthalmology has been less well documented. This section on current ophthalmology discusses the novel use and future of blockchain technology for intraocular lens power calculation and refractive surgery workup, ophthalmic genetics, payment methods, international data documentation, retinal images, global myopia pandemic, virtual pharmacy, and drug compliance and treatment. The authors have also provided valuable insights into various terminologies and definitions used in blockchain technology.

Intraoperative aberrometry versus preoperative biometry for intraocular lens power selection in patients with axial hyperopia

Purpose: This study was conducted to evaluate the accuracy of intraoperative aberrometry (IA) in intraocular lens (IOL) power calculation and compare it with conventional IOL formulas. Methods: This was a prospective case series. Eyes with visually significant cataract and axial hyperopia (AL <22.0 mm) underwent IA?assisted phacoemulsification with posterior chamber IOL (Alcon AcrySof IQ). Postoperative spherical equivalent (SE) was compared with predicted SE to calculate the outcomes with different formulas (SRK/T, Hoffer Q, Haigis, Holladay 2, Barrett Universal ? and Hill?RBF). Accuracy of intraoperative aberrometer was compared with other formulas in terms of mean absolute prediction error (MAE), percentage of patients within 0.5 D and 1 D of their target, and percentage of patients going into hyperopic shift. Results: Sixty?five eyes (57 patients) were included. In terms of MAE, both Hoffer Q (MAE = 0.30) and IA (MAE = 0.32) were significantly better than Haigis, SRK/T, and Barrett Universal ? (P < 0.05). Outcomes within ±0.5 D of the target were maximum with Hoffer Q (80%), superior to IA (Hoffer Q > IA > Holladay 2 > Hill?RBF > Haigis > SRK/T > Barrett Universal ?). Hoffer Q resulted in minimum hyperopic shift (30.76%) followed by Hill?RBF (38.46%), Holladay 2 (38.46%), Haigis (43.07%), and then IA (46.15%), SRK/T (50.76%) and Barrett Universal ? (53.84%). Conclusion: IA was more effective (statistically significant) in predicting IOL power than Haigis, SRK/T, and Barrett Universal ? although it was equivalent to Hoffer Q. Hoffer Q was superior to all formulas in terms of percentage of patients within 0.5 D of their target refractions and percentage of patients going into hyperopic shift

Ten commandments for biometry in tricky situations

Background: Recently, the number of litigations on cataract surgeons has increased. Because of the increasing ambitions of surgeons and demands for a spectacle?free life, the incidence of unhappy patients is at an all?time high. To an ophthalmologist, the fruits of a good surgery are dependent largely on their skills. However, more importantly, the roots of good results of a surgery are laid by a perfect IOL (intraocular lens) power calculation. Inaccurate biometry is one of the major reasons for unhappy patients, especially in some challenging scenarios. Purpose: To hit the bull’s eye, as far as target refraction is concerned, it is necessary to understand the benefits and limitations of currently available cutting?edge technology and formulae and apply them to the cataract surgery practice. The aim of the video is to familiarize modern?day ophthalmologists to these situations to achieve a perfect IOL power calculation. Synopsis: Using a step?by?step approach, we decoded biometry in special scenarios like poor cornea, ocular surface disorders, dry eyes, toric IOL calculation, cases with posterior corneal astigmatism, irregular corneas like keratoconus, pellucid marginal degeneration, post Lasik ectasia and penetrating keratoplasty. In this video we tried to address the solution to these special conditions and how to attain target refraction in such cases. A few more issues are addressed like biometry post retina surgery, very dense cataract where it is difficult to obtain axial length, and cases with extreme axial lengths. Highlights: In this case?based approach, with relevant example, we tried to provide solutions for biometry in tricky scenarios like poor cornea, biometry post refractive surgery, dense cataracts, and cataract post retinal surgery. On following these commandments, not only will the litigations stop but our patients will be happier as well

Refractive prediction by various intraocular lens formulas using optical biometry and effect of ocular parameters on their accuracy

Purpose: To assess the prediction accuracy of intraocular lens (IOL) formulas and study the effect of axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), and lens thickness (LT) on the accuracy of formulas using optic biometry. Methods: This study was performed on 164 eyes of 164 patients who underwent uneventful cataract surgery. Ocular biometry values were measured using Lenstar?900, and intraocular lens (IOL) power was calculated using the SRK/T, SRK II, Hoffer Q, Holladay 2, and Barrett Universal II formulas. We evaluated the extent of bias within each formula for different ocular biometric measurements and explored the relationship between the prediction error and the ocular parameters by using various IOL formulas. Results: The summarization of refractive prediction error and absolute prediction error for each IOL formulation was performed after adjusting the mean refractive error to zero. The deviation in the error values was minimum for SRK/T (0.265) followed by Holladay 2 (0.327) and Barret (0.382). Further, SRK/T had the lowest median (0.15) and mean (0.198) absolute error as compared to other formulations. For the above formulations, 100% of the eyes were in the diopter range of ±1.0. It was observed that the overall distribution of error was closer to zero for SRK/T, followed by Holladay 2 and then Barrett. Conclusion: In summary, we found that accuracy was better in SRK/T formula. We achieved a better understanding of how each variable in the formulas is relatively weighed and the influencing factors in the refraction prediction.

Analyze the effect of keratometry on the calculation accuracy of intraocular lens diopter in patients with normal axial cataract / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To evaluate the effect of keratometry on the calculation accuracy of intraocular lens(IOL)diopter in patients with normal axial cataract.METHODS:Totally 157 cases(157 eyes)with age related cataract were collected in Kaifeng Central Hospital from June 2020 to June 2021. Patients were divided into 3 groups according to keratometry: group A(53 eyes)(K<42D), group B(55 eyes)(42D≤K≤46D), group C(49 eyes)(K>46D). The IOL diopter was calculated by SRK/T, Hoffer Q, Holladay 2, Haigis, Kane and Barrett Ⅱ formulas respectively. Subjective optometry was performed after 1mo operation. The average refractive prediction error(RPE)and mean absolute error(MAE)were calculated, and their differences were compared and analyzed.RESULTS:There were significant difference between RPE of each formula and 0D in groups A and C(<i>P</i><0.05), and Barrett Ⅱ formula was significantly different with SRK/T, Hoffer Q, Holladay 2 and Haigis formula(<i>P</i><0.01), but was no significantly different with Kane formula in RPE(<i>P</i>>0.01). There was no significant difference in RPE between group B and 0D(<i>P</i>>0.05). The ratio of Barrett Ⅱ formula in MAE≤0.5D in group A was significantly higher than SRK/T, Hoffer Q, Holladay 2 and Haigis formula(all <i>P</i><0.01), but there was no significant difference compared with Kane formula(<i>P</i>>0.01). In group B, there was no significant difference among Barrett Ⅱ formula and the other formulas in the ratio of MAE≤0.5D and ≤1.0D(all <i>P</i> >0.01). In group C, the ratio of SRK/T and Hoff Q formula in MAE≤0.5D was lower than Barrett Ⅱ formula(all <i>P</i><0.01), and there were no significant difference among Barrett Ⅱ formula and the other formulas in the ratio of MAE≤1.0D(<i>P</i> >0.01).CONCLUSION:If K<42D or K>46D before operation, the commonly used formulas will produce refractive error, but the accuracy of Kane and Barrett Ⅱ formulas are still higher than other formulas.

Changes of biological parameters and the accuracy of IOL power calculation formulas after phacoemulsification / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To measure the changes of ocular biological parameters before and after phacoemulsification, and compared the choice of intraocular lens(IOL)power calculation formulas based on the new optical biometric instrument IOL Master 700.METHODS: A prospective study. Clinical data were collected from 52 patients(57 eyes)with cataract at the First Affiliated Hospital of Soochow University from January to June 2021. The axial length(AL), anterior chamber depth(ACD)and corneal curvature(Km)were measured and analyzed before and 3mo after phacoemulsification by IOL Master 700. The target refractive value reserved in the calculation of different IOL formulas and the actual refractive value of the automatic refractor 3mo after phacoemulsification were compared and statistically analyzed.RESULTS: The average values of AL measured before and after phacoemulsification were 24.20±1.86, 24.09±1.86mm, the postoperative AL shortened by 0.11mm, and the ACD values were 3.08±0.44, 4.55±0.36mm(P&#x003C;0.001), ACD deepened by 1.49mm after phacoemulsification. The Km values were 44.14±1.86, 44.14±1.82D(P&#x003E;0.05). The refractive error of the results measured by the Barrett Universal Ⅱ formula was the smallest before operation, followed by Holladay Ⅱ and the SRK/T formula, the Holladay Ⅰ formula had the largest error and the difference was statistically significant(P&#x003C;0.05). CONCLUSION: The AL was shortened and the ACD was deepened after phacoemulsification. A correction factor of 0.1mm is suggested to add when calculating the degree. The Barrett Universal Ⅱ formula has the best predictability in the IOL power calculation formulas, follow by Holladay Ⅱ and SRK/T formula.

Observation on the effect of combined surgery in cataract patients with pterygium / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To observe the effect of combined surgery in cataract patients with pterygium.<p>METHODS:A prospective single centered study was performed on 22 patients(mean age: 59.05±8.70 years)of concurrent cataract and pterygium(size 2-5 mm in length), who attended the outpatient department during the study period of one year, and the minimum follow up was 3mo-1a for all patients. Mean keratometry(K_mean), mean astigmatism, best corrected visual acuity(LogMAR), preoperatively and 3mo postoperatively had been determined. The corneal curvature, pterygium size and the prediction error(PE)were observed.<p>RESULTS: The amount of PE was <±0.50 D in 18 patients(81.8%)and ±0.50 D to ±1.00 D in 4 patients(18.2%). None of the patients had PE of >1.00 D. The mean axial length did not change significantly(<i>P</i>=0.77)postoperatively. The mean keratometric reading increased from 42.994±1.536 preoperatively to 43.324±1.479 postoperatively but this was not significant(<i>P</i>=0.105). The corneal astigmatism decreased significantly from 2.09±0.789 D preoperatively to 0.523±0.277 D postoperatively(<i>P</i><0.05). BCVA(LogMAR)significantly improved from 1.007±0.402 preoperatively to 0.024±0.062 postoperatively(<i>P</i><0.05). No correlation was found between changes in keratometry and PE(<i>r</i>=-0.29, <i>P</i>=0.19). And, there was no correlation was found between pterygium size and PE(<i>r</i>=0.2997, <i>P</i>=0.17). <p>CONCLUSION: Combined phacoemulsification+foldable intraocular lens(IOL)implantation and conjuctival autograft(CAG)application was safe and effective procedure.

Effect of pupil dilation on ocular biometry measurement and IOL power calculation in cataract patients with high myopia / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To evaluate the effect of pupil dilation on ocular biometry and IOL power in cataract patients with high myopia, and the difference between cataract patients with high myopia and cataract patients with normal axial length(AL).<p>METHODS:Measurements of AL, corneal curvature(K including K1 and K2), anterior chamber depth(ACD)were performed using IOLmaster in 22 cataract patients with high myopia(34 eyes)(group A)and 23 cataract patients with normal AL(39 eyes)(group B)before and after pupil dilation. SRK-T and Haigis were used to caculate pre- and post-cycloplegic IOL power.<p>RESULTS:ACD after dilation(3.84±0.58mm)significantly increased comparing with ACD before dilation(3.61±0.35mm)in group A(<i>P</i><0.01). ACD after dilation(3.30±0.70mm)also significantly increased comparing with ACD before dilation(3.13±0.63mm)in group B(<i>P</i><0.01). But the difference of pre- and post-cycloplegic ACD between the two groups was not statistically significant(<i>P</i>>0.05). Pre- and post-cycloplegic AL and K(including K1 and K2)were not significantly different in two groups(<i>P</i>>0.05). The differences between pre- and post-cycloplegic IOL power were not statistically significant using the SRK-T and Haigis formula(<i>P</i>>0.05), but the IOL power changed by over 1D after pupil dilation using the SRK-T and Haigis formula respectively in 15% and 27% of eyes in group A,in 3% and 5% in group B.<p>CONCLUSION:ACD increases after pupil dilation in cataract patients with high myopia, which is not different from cataract patients with normal AL. Pupil dilation does not affect AL, K and the IOL power(using SRK-T and Haigis)in cataract patients with high myopia. But the IOL power may change greater than in cataract patients with normal AL, so we suggest IOL power should be measured and calculated without mydriasis.

Accuracy of the refractive prediction determined by intraocular lens power calculation formulas in high myopia

Purpose: Our study was conducted to evaluate and compare the accuracy of the refractive prediction determined by the calculation formulas for different intraocular lens (IOL) powers for high myopia. Methods: This study reviewed 217 eyes from 135 patients who had received cataract aspiration treatment and IOL implantation. The refractive mean numerical error (MNE) and mean absolute error (MAE) of the IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) were examined and compared. The MNE and MAE at different axial lengths (AL) were compared, and the percentage of every refractive error absolute value for each formula was calculated at ±0.25D, ±0.50D, ±1.00D, and ±2.00D. Results: In all, 98 patients were recruited into this study and 98 eyes of them were analyzed. We found that Barrett Universal II formula had the lowest MNE and MAE, SRK/T and Haigis formulas arrived at similar MNE and MAE, and the MNE and MAE calculated by Holladay and Hoffer Q formula were the highest. Barrett Universal II formulas have the lowest MAE among different AL patients, whereas it reached the highest percentage of refractive error absolute value within 0.5D in this study. The MAE of each formula is positively correlated with AL. Conclusion: Barrett Universal II formula rendered the lowest predictive error compared with SRK/T, Haigis, Holladay, and Hoffer Q formulas. Thus, Barrett Universal II formula may be regarded as a more reliable formula for high myopia.

Intraocular lens power calculation in eyes with previous LASIK/PRK / 国际眼科杂志(Guoji Yanke Zazhi)

@#Calculating the intraocular lens(IOL)power in eyes with prior corneal refractive surgery(LASIK/PRK)is still a challenging task for all cataract ophthalmologists. The accuracy of the IOL power calculating is lower than virgin eyes, because the three generation formulae and traditional corneal instruments which measure central corneal radius of curvature in the paracentral 2.5-3.2mm zone are incorrect after myopic refractive surgery. There are three main sources of error in IOL calculation after refractive surgery: the radius measurement error, the keratometer index error and the IOL formula error. The purpose of the present paper is to describe the different available techniques to improve the accuracy of the IOL power calculation after refractive procedures.

Aplicación de un factor de corrección para el cálculo del lente intraocular en pacientes con cámara anterior / Application of a correction factor for intraocular lens power calculation in patients with a narrow anterior chamber and augmented crystalline lens thickness

Objetivo: evaluar la aplicación de un factor corrección en el cálculo del lente intraocular en pacientes con cámara anterior estrecha y grosor del cristalino aumentado. Métodos: se realizó un estudio experimental donde se aplicó un factor de corrección y se comparó con dos grupos de control. Resultados: predominó el sexo femenino con el 71 por ciento de los casos. La edad fue de 70 años y más. El 48,4 por ciento de los pacientes presentó una esfera posoperatoria entre ± 0,50 dioptrías; el 19,4 por ciento estuvo por debajo de -0,50 dioptrías y el 32,3 por ciento de los pacientes por encima de + 0,50 dioptrías. El grupo 3 (grosor del cristalino mayor que 4,60 mm si factor de corrección) tuvo el mayor porcentaje de esfera posoperatoria ± 0,50 dioptrías (58,3 por ciento). El grupo 2 tuvo el mayor porcentaje de pacientes con esfera obtenida mayor de 0,50 dioptrías (38,2 por ciento). Conclusiones: los pacientes a quienes se les aplica el factor de corrección obtienen una esfera posoperatoria cercana a la emetropía a pesar de que la muestra no es homogénea y no se obtienen esferas por encima de 1 dioptría(AU)

Objective: Evaluate the application of a correction factor for intraocular lens power calculation in patients with a narrow anterior chamber and augmented crystalline lens thickness. Methods: An experimental study was conducted in which a correction factor was applied and compared with two control groups. Results: Female sex prevailed with 71 percent of the cases. Age was 70 years and over. 48.4 percent of the patients had a postoperative sphere between ± 0.50 diopters; 19.4 percent were below - 0.50 diopters and 32.3 percent were above + 0.50 diopters. Group 3 (crystalline lens thickness above 4.60 mm without correction factor) had the highest postoperative sphere percentage of ± 0.50 diopters (58.3 percent). Group 2 had the highest percentage of patients with an achieved sphere above 0.50 diopters (38.2 percent). Conclusions: Patients to whom the correction factor was applied achieved a postoperative sphere close to emmetropia, despite the fact that the sample was not homogeneous and spheres above 1 diopter were not obtained(AU)

Comparative Efficacy of the New Optical Biometer on Intraocular Lens Power Calculation (AL-Scan versus IOLMaster)

PURPOSE: To evaluate the agreement in axial length (AL), keratometry, and anterior chamber depth measurements between AL-Scan and IOLMaster biometers and to compare the efficacy of the AL-Scan on intraocular lens (IOL) power calculations and refractive outcomes with those obtained by the IOLMaster. METHODS: Medical records of 48 eyes from 48 patients who underwent uneventful phacoemulsification and IOL insertion were retrospectively reviewed. One of the two types of monofocal aspheric IOLs were implanted (Tecnis ZCB00 [n = 34] or CT Asphina 509M [n = 14]). Two different partial coherence interferometers measured and compared AL, keratometry (2.4 mm), anterior chamber depth, and IOL power calculations with SRK/T, Hoffer Q, Holladay2, and Haigis formulas. The difference between expected and actual final refractive error was compared as refractive mean error (ME), refractive mean absolute error (MAE), and median absolute error (MedAE). RESULTS: AL measured by the AL-Scan was shorter than that measured by the IOLMaster (p = 0.029). The IOL power of Tecnis did not differ between the four formulas; however, the Asphina measurement calculated using Hoffer Q for the AL-Scan was lower (0.28 diopters, p = 0.015) than that calculated by the IOLMaster. There were no statistically significant differences between the calculations by MAE and MedAE for the four formulas in either IOL. In SRK/T, ME in Tecnis-inserted eyes measured by AL-Scan showed a tendency toward myopia (p = 0.032). CONCLUSIONS: Measurement by AL-Scan provides reliable biometry data and power calculations compared to the IOLMaster; however, refractive outcomes of Tecnis-inserted eyes by AL-Scan calculated using SRK/T can show a slight myopic tendency.

Principios para el cálculo de la lente intraocular tras cirugía refractiva corneal / Principles for the intraocular lens power calculation after corneal refractive surgery

Se estima que aproximadamente un millón o más de pacientes se realizan cirugía refractiva al año. Es por eso que con el envejecimiento son cada día más frecuentes los pacientes con catarata, a quienes previamente se les ha efectuado cirugía refractiva. El cálculo inexacto de la potencia dióptrica de la lente a implantar en la intervención de estos es también un problema de importancia creciente y con él la sorpresa refractiva. Este es mucho más complejo de lo normal, ya que existen dos fuentes de error: la incorrecta predicción de la posición efectiva de la lente por parte de la fórmula y la determinación errónea de la potencia de la córnea por parte de la queratometría. La corrección de estos dos factores permitirá realizar un cálculo correcto en estos ojos. De ahí la motivación para realizar una búsqueda actualizadas de los últimos diez años de diversos artículos publicados, con el objetivo de describir los principios para el cálculo de la lente intraocular tras cirugía refractiva corneal. Se utilizó la plataforma Infomed, específicamente la Biblioteca Virtual de Salud, con todos sus buscadores(AU)

It is considered that approximately one million or more patients undergo refractive surgery every year. Due to aging, the number of patients with cataract, who had previously undergone refractive surgery, is increasingly higher. The inaccurate calculation of the dioptric power of the lens to be implanted is also a growing significant problem and thus the refractive surprise. This is a much more complex situation since two error sources exist: the incorrect prediction of the effective position of the lens based on the formula and the wrong determination of the corneal power through keratometry. The correction of these two factors will allow making a suitable power calculation. Hence the motivation for updated search of several articles published in the last ten years, with the objective of describing the principles for intraocular lens power calculation after corneal refractive surgery. The Infomed platform, mainly the Virtual Library of Health, was fully used(AU)

Effect of pupillary dilation on intraocular lens power calculation / 国际眼科杂志(Guoji Yanke Zazhi)

Abstract?AIM: To investigate the effect of pupillary dilation on intraocular lens power calculation.?METHODS: This prospective study included 52 eyes of 45 patients diagnosed with cataract and indicated for phacoemulsification with intraocular lens ( IOL ) implantation at the Faculty of Medicine of Mersin University. For each patient, preoperative corneal topography, autokeratometric measurements and biometric measurements were performed before and after pupil dilation.?RESULTS: Kh ( horizontal ) values obtained through autokeratometry and anterior chamber depth measured by biometric ultrasonography were significantly greater when pupils were dilated compared with values obtained when pupils were undilated. Implanting IOLs with power calculated using measurements taken during pupillary dilation resulted in a significantly higher rate of emmetropia. Comparison of emmetropic eyes and ametropic eyes showed significantly larger anterior chamber depth in emmetropic eyes.? CONCLUSION: Keratometric and biometric measurements are more important in IOL power calculation than the formula used. If biometric ultrasonography is performed using contact technique, care must be taken to avoid corneal compression. Anterior chamber depth should be followed during measurement, and the margin of error can be minimized by using the highest value obtained in IOL power calculation.

Preliminary evaluation of an algorithm to minimize the power error selection of an aspheric intraocular lens by optimizing the estimation of the corneal power and the effective lens position / 国际眼科杂志(Guoji Yanke Zazhi)

?AIM: To evaluate the refractive predictability achieved with an aspheric intraocular lens ( IOL ) and to develop a preliminary optimized algorithm for the calculation of its power ( PIOL ) .?METHODS:This study included 65 eyes implanted with the aspheric IOL LENTIS L-313 ( Oculentis GmbH ) that were divided into 2 groups:12 eyes (8 patients) with PIOL≥23. 0 D (group A), and 53 eyes (35 patients) with PIOL<23. 0 D ( group B ). The refractive predictability was evaluated at 3mo postoperatively. An adjusted IOL power ( PIOLadj ) was calculated considering a variable refractive index for corneal power estimation, the refractive outcome obtained, and an adjusted effective lens position ( ELPadj ) according to age and anatomical factors.?RESULTS: Postoperative spherical equivalent ranged from -0. 75 to +0. 75 D and from -1. 38 to +0. 75 D in groups A and B, respectively. No statistically significant differences were found in groups A (P=0. 64) and B (P=0. 82 ) between PIOLadj and the IOL power implanted ( PIOLReal ) . The Bland and Altman analysis showed ranges of agreement between PIOLadj and PIOLReal of +1. 11 to -0. 96 D and +1. 14 to -1. 18 D in groups A and B, respectively. Clinically and statistically significant differences were found between PIOLadj and PIOL obtained with Hoffer Q and Holladay I formulas (P<0. 01).?CONCLUSION: The refractive predictability of cataract surgery with implantation of an aspheric IOL can be optimized using paraxial optics combined with linear algorithms to minimize the error associated to the estimation of corneal power and ELP.

Intraocular Lens Power Calculations Using Dual Scheimpflug Analyzer

PURPOSE: To investigate the accuracy of intraocular lens power calculations using simulated keratometry (simK) of dual Scheimpflug analyzer and 5 types of formulas in cataract patients. METHODS: The keratometry (K), axial length (AXL) and anterior chamber depth (ACD) were measured using ultrasound biometry (USB) combined with auto-keratometry (Auto-K), parital coherence interferometry (PCI; IOL master®) and dual Scheimpflug analyzer (DSA; Galilei®) in 39 eyes of 39 patients. Predicted refraction was calculated using Auto-K, mean K of PCI, and simK and total corneal power (TCP) of DSA in the Sanders-Retzlaff-Kraff (SRK-T) formula. The SRK-II, SRK-T, Holladay II, Haigis, and Hoffer-Q formula were used to calculate predicted refraction with the simK of DSA and AXL of USB. Manifest refraction, mean numerical error (MNE) and mean absolute error were evaluated 1, 3 and 6 months after cataract surgery. RESULTS: TCP of DSA was lower compared with other keratometric values (p < 0.05). The MNE was not different among Auto-K, mean K and simK. The MNE using TCP was larger compared with Auto-K, mean K and simK at 1 month after surgery (p < 0.05). There was a difference in MNE between simK and TCP of DSA at 6 months after surgery (p < 0.05). The MNE of SRK-T formula was the smallest in the intraocular lens (IOL) power calculation using the simK of DSA. CONCLUSIONS: We suggest using IOL power calculations with simK of DSA and SRK-T formula rather than TCP of DSA in cataract patients with normal corneas.

The correlation study between the difference of equal IOL pre-and post Lasik and the degree of my-opia / 中国医师杂志

Objective The difference of the equivalent IOL powers before and after LASIK was calculated by using the Haigis-L formula and Sirius ray-tracing respectively.And study the correlation be-tween the intraocular lens power and the myopic before laser in situ keratomileusis.Methods Ninety-one patients undergoing myopic laser in situ keratomileusis were enrolled, they were divided into 3 groups ac-cording to myopic diopter, group I (-1.00D~-3.00D) 13cases, group II( -3.25D and -6.00D)60 cases, group III(-6.25D~-10.0D)18 cases.The equivalent IOL power before and after LASIK will be calculated using Haigis-L formula and Sirius ray-tracing.The data were analyzed using SPSS20.0.Results 80.2%of the cases calculated using Haigis-L formula were within ±0.50D of the predicted refraction , 94.5%were within ±1.00D, and 100%within ±1.50D.also, within ±0.50D of the predicted refrac-tion 13cases(100%),51cases(85%),9cases(50%) in group I, II, III respectively.74.7% of the eyes calculated using Sirius ray-tracing were within ±0.50D of the predicted refraction , 89.0%were within ± 1.00D, and 100%within ±1.50D.within ±0.50D of the predicted refraction 12cases(92.3%),48cases (80%),8cases(44.4%) in group I, II, III respectively.Conclusions Sirius ray-tracing and Haigis-L formula can calculate IOL power accurately in eyes with prior myopic LASIK, with no need for preoperative data.and there is positive correlation between the intraocular lens power aberration and the myopic diopter before LASIK.

Application of Pentacam in the cataract surgery / 国际眼科杂志(Guoji Yanke Zazhi)

With the improvement of cataract operation, the cataract surgery has become increasingly perfect. The cataract patients show greater expectation for the result of cataract operation. As a result, refractive cataract surgery has become the main trend. Detailed investigations of corneal diseases, lens density, corneal topography, preferable intraocular lens ( IOL ) choice, and IOL power calculation can help us get a better knowledge of preoperative conditions on patients, which can be conducted with pentacam. So we can have a better forecast of post - operative outcome and improve the quality of vision for cataract patients after surgery.

Sample size determination for repeated measures design using G Power software

Repeated measures designs are widely used in the field of anesthesiology because they allow the detection of within-person change over time and provide a higher statistical power for detecting differences than a single measure design while reducing the costs and efforts to conduct a study. However, the complex process of calculating the sample size for repeated measures design requires profound statistical knowledge and also programming skills in some instances. In the present article, the author describes 1) the basic statistics for repeated measures design, 2) the explanation for G Power software, and 3) how to calculate the sample size using an example.

Intraocular Lens Power Estimation in Combined Phacoemulsification and Pars Plana Vitrectomy in Eyes with Epiretinal Membranes: A Case-Control Study

PURPOSE: To evaluate the accuracy of postoperative refractive outcomes of combined phacovitrectomy for epiretinal membrane (ERM) in comparison to cataract surgery alone. MATERIALS AND METHODS: Thirty-nine eyes that underwent combined phacovitrectomy with intraocular lens (IOL) implantation for cataract and ERM (combined surgery group) and 39 eyes that received phacoemulsification for cataract (control group) were analyzed, retrospectively. The predicted preoperative refractive aim was compared with the results of postoperative refraction. RESULTS: In the combined surgery group, refractive prediction error by A-scan and IOLMaster were -0.305+/-0.717 diopters (D) and -0.356+/-0.639 D, respectively, compared to 0.215+/-0.541 and 0.077+/-0.529 in the control group, showing significantly more myopic change compared to the control group (p=0.001 and p=0.002, respectively). Within each group, there was no statistically significant difference in refractive prediction error between A-scan and IOLMaster (all p>0.05). IOL power calculation using adjusted A-scan measurement of axial length based on the macular thickness of the normal contralateral eye still resulted in significant postoperative refractive error (all p<0.05). Postoperative refraction calculated with adjusted axial length based on actual postoperative central foveal thickness change showed the closest value to the actual postoperative achieved refraction (p=0.599). CONCLUSION: Combined phacovitrectomy for ERM resulted in significantly more myopic shift of postoperative refraction, compared to the cataract surgery alone, for both A-scan and IOLMaster. To improve the accuracy of IOL power estimation in eyes with cataract and ERM, sequential surgery for ERM and cataract may need to be considered.