Biometric error analysis after cataract surgery performed by residents, in patients with high myopia with SRK/T formula and Wang-Koch formula adjustment. (original) (raw)
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Journal of Advances in Medicine and Medical Research
Background: Contact A-scan ultrasonic biometry is the most frequently utilized technique for determining axial length (AXL). Optical biometry is a technique that utilises partial coherence interferometry to determine ocular biometry parameters. The aim of this research was to compare the efficacy in estimating postoperative refraction by measuring intraocular lens (IOL) power by the optical biometry (IOL Master) and contact A-scan ultrasound plus Bausch & Lomb (B&L) keratometry after phacoemulsification surgery. Methods: This prospective, comparative, interventional and randomized study involved 40 eyes with uneventful phacoemulsification surgery and in the bag IOL of adult patients with cataract. Subjects were allocated into 2 equal groups: group A: implanted the IOL power estimated by the automated method and group B: implanted the IOL power estimated by the manual method. All patients were subjected to complete ophthalmic examination, best-corrected visual acuity (BCVA), uncorrec...
Journal of Evidence Based Medicine and Healthcare, 2020
BACKGROUND IOL implantation has turned into a very significant part of modern-day cataract surgery. IOL implantation no longer only sub serves the purpose of better visual rehabilitation but is currently considered as a form of refractive surgery. Accurately predicted post-operative visual outcome has become the necessity of present times. In this regard, precise pre-operative biometric measurement is an essential prerequisite. The aim of the study was to compare the accuracy of optical biometry and conventional ultrasound measurement of the preoperative intraocular lens power calculation formula (SRK/T) of highly myopic eye. METHODS This study included 58 eyes of 50 patients [(10 cases of bilateral and 48 cases of unilateral cataract) (20 female (45%) and 30 male (55%)] with extreme myopia and axial lengths ≥25.0 mm with cataract as the only ocular pathology. Patients were divided in two groups. Group 1 (the optical biometry group) included 25 patients and group 2 (the A-scan ultrasound group) included 25 patients. Those eyes were included in the present study which had visually significant lenticular opacity. Eyes which were not suitable for phacoemulsification and primary in-thebag posterior chamber IOL insertion were excluded for minimizing the confounding factors, all patients were operated by the same surgeon and implantation of single piece soft hydrophobic aspheric acrylic IOL from the same manufacturer was done. (power range ±12.0. D to ±16.0 D). RESULTS This study was carried out on 58 Eyes of 50 high myopia patients who had initially presented with visually significant cataract. Patients were randomly divided into two groups: First Group (Group 1 included 30 eyes all of which underwent Optical Biometry using a single machine from the same manufacturer (Zeiss 700 IOL master) and Second Group (Group 2) included 28 eyes all of which underwent conventional A Scan Ultrasound Biometry using a single machine from the same manufacturer (Sonomed PAC SCAN 300 AP). The proportion of eyes with postoperative spherical equivalent of ≤±0.5 D, ≤±0.75 D and ≤±1 D in the conventional ultrasound biometry group were significantly lower when compared with corresponding proportions in the IOL Master group (p<0.00) respectively. CONCLUSIONS Optical Biometry using partial coherence interferometry gives significantly better pre-operative IOL power prediction as compared to conventional ultrasound-based biometry in high myopia patients.
Comparative Study of Manual Versus Automated Biometry on Refractive Outcome of Cataract Surgery
Journal of Evolution of Medical and Dental Sciences
BACKGROUND Intraocular Lens (IOL) power calculation is the most important step to achieve best refractive outcome in cataract surgery. Various studies had revealed that about 54% of the error in predicted refraction occurred due to inaccuracy in axial length measurement alone. Therefore, axial length measurement is the most important step to minimise these errors. The aim of this study was to compare IOL power calculation using a manual method (Applanation ultrasound A-Scan and Keratometry) with the automated method (Optical biometry). MATERIALS AND METHODS It was a prospective, comparative study. In this study, 200 eyes of 196 patients were analysed in the Department of Ophthalmology. Each eye underwent measurement by both methods, with manual method (Applanation Ultrasound A-Scan and manual Keratometer) and with automated optical biometry. Axial length and Keratometric readings were obtained and IOL power calculation was done by both the methods. Patient underwent clear corneal phacoemulsification cataract surgery within the IOL implantation in all the cases, then postoperative autorefraction was noted in all cases in follow-ups. RESULTS The Mean Axial Length calculated by optical A scan was 23.02±1.00 mm and by ultrasound A scan was 22.93±1.03 mm. The mean difference in axial length between optical system and Ultrasound A scan was 0.087±0.039 mm, which is statistically not significant (p value 0.19). However, differences in axial length measurement were more when compared, for short eyes, by two devices. After analysis of Bland-Altman plot. All differences were within two standard deviations (95% confidence level) from mean differences (0.0869±0.038 mm, i.e. between 0.0096 mm and 0.1641 mm). The regression line between the two methods, Pearson's correlation coefficient 'r' is 0.999, which evaluates excellent agreement of axial length measurement between two methods. The differences in mean IOL power between automated method and manual method was 0.43±0.38 D, which was statistically and clinically insignificant (p value 0.09). CONCLUSION To measure axial length and IOL power, optical biometry is very precise and interchangeable with ultrasound method. Optical biometry in short eyes gives better result in axial length measurement as compared to ultrasound A-scan.
JOURNAL OF CLINICAL AND DIAGNOSTIC RESEARCH
Introduction: The evolution of modern technologies for cataract surgery has made it crucial for aiming emmetropia with highly defined vision. The key factor responsible for postoperative emmetropia is an accurate biometry, along with various other factors. Ultrasonic biometry is the gold standard method of Intraocular Lens (IOL) power calculation but the corneal indentation with the probe underestimate the axial length and result in a myopic shift which is overcome by the newer optical biometry devices, including swept source optical coherence biometry which uses infrared light to measure the ocular distances. Aim: To determine the precision and accuracy of IOL power calculation by ultrasound A-scan and optical IOL master and their refractive outcomes. Materials and Methods: This prospective, and observational study was conducted between September 2019 to February 2021 in 155 patients with cataract undergoing phacoemulsification in Kalinga Institute of Medical Sciences, KIIT Univers...
Clinical Ophthalmology, 2017
Purpose: To evaluate the accuracy of the SRK/T formula using ultrasound (US) biometry in predicting a target postoperative refraction of ±1.00D in eyes with medium axial length (AL) that underwent phacoemulsification. Methods: The present study was a retrospective analysis, which included 538 eyes with an AL from 22.0 to 24.60 mm that underwent phacoemulsification and foldable intraocular lens (IOL) implantation (six different IOLs) in the bag. Preoperative AL was measured by US biometry and IOL power (IOLp) was calculated with the SRK/T formula. Patients had a complete ophthalmic examination, preoperatively and 1, 7, and 30 days after surgery. The achieved spherical equivalent (SE) and the prediction error (PE) were calculated. The prediction error was defined as the difference between attempted predicted target refraction and the achieved postoperative SE refraction. Statistical analysis was performed with SPSS V21. Results: The mean age of the patients was 66.96±9.67 years, the mean AL was 23.29±0.62 mm, the mean K1 was 43.62±1.49D, the mean K2 was 43.69±1.53D, the mean IOL power was 21.066±1.464D, the mean attempted (predicted) SE was-0.178±0.266D, and the mean achieved SE was-0.252±0.562D. The mean PE (difference between predicted and achieved SE) showed a relatively hyperopic shift (mean ± standard deviation: 0.074±0.542D, ranging from-1.855 to 2.170D, P=0.001). A total of 93.87% of eyes were within ±1.00D of the PE and 92.75% of eyes within ±1.00D of achieved postoperative refraction. A total of 39 eyes (7.25%) had a refractive surprise. A total of 32 of 39 eyes were more myopic than-1.00D and 7 of them were more hypermetropic than +1.00D. There was no correlation between the mean PE and IOL type, AL, K1, K2, and IOLp. There were a positive statistically significant correlation between PE and age (r=0.095; P=0.028) and a negative statistically significant correlation between achieved SE and AL (Spearman's r=-0.125; P=0.04), and age (r=-0.141; P=0.01). Conclusion: The IOLp calculation using the SRK/T formula with US biometry may demonstrate very good postoperative refractive outcomes in medium eyes with a few refractive surprises.
Biometry, Refractive Errors, and the Results of Cataract Surgery: A Large Sample Study
Journal of Ophthalmology, 2021
The statistical characteristics of biometry and refractive error in a large sample of cataractous Cuban patients are presented, comparing between sexes and age groups. All patients were studied at the Cuban Institute of Ophthalmology “Ramón Pando Ferrer,” La Habana. The sample consists of 28252 eyes of 25068 patients, subjected to cataract surgery during the time period between 2006 and 2019. Their biometry was obtained using IOL Master devices; also, visual acuity, refraction, and corneal power were registered. After surgery, the visual acuity and refraction were measured. The refractive prediction error was determined. For patients with both eyes registered, anisometropia was also calculated. Age and sex were used to segment the data. The preoperative biometric parameters show highly significant differences between sexes, with male eyes being longer and with a deeper anterior chamber but with a thinner lens. Also, keratometry shows highly significant differences, with female eyes ...
Biometry and Formula Accuracy With Intraocular Lenses Used for Cataract Surgery in Extreme Hyperopia
American Journal of Ophthalmology, 2007
PURPOSE: To audit intraocular lens (IOL) power predictions for cataract surgery in extreme hyperopia and to compare the accuracy across different biometry formulae and IOL types. • DESIGN: A retrospective analysis of 76 eyes from 56 patients undergoing cataract surgery with IOLs ranging in power from 30 to 35 diopters (D). • METHODS: Axial lengths, corneal powers and anterior chamber depths were measured with ultrasound or optical methods, and the IOLMaster (Carl Zeiss Meditech, Inc, Dublin, California, USA) software was used to predict the refractive outcome for each IOL used. Differences between the predicted and actual postoperative refraction were then analyzed for each formula. • RESULTS: In practice, 55% of patients were within ؎1.0 D of the refraction predicted by their surgeon. In theory, the Haigis formula would have given the smallest mean refractive error (؉0.51 ؎ 0.12 D), followed by the Hoffer Q (؊0.70 ؎ 0.14 D), Holladay 1 (؊1.11 ؎ 0.13 D), and SRK/T formulae (؊1.45 ؎ 0.14 D). The Haigis formula overpredicted the lens power required, which would have generated a myopic result. The other formulae underpredicted the lens power required and would have generated a hyperopic result. There was a significant difference between lens designs: the Haigis was more accurate for open-loop, whereas the Hoffer Q was more accurate for plate-haptic lenses. The anterior chamber depth measurement could also be used to predict changes in intraocular pressure after surgery. • CONCLUSION: This represents the largest published series to date of biometry predictions for cataract surgery in extreme hyperopia and confirms the Haigis formula to be the most accurate. A consistent difference between open-loop and plate-haptic lenses suggests that haptic design may influence the effective lens position in very small eyes. We further propose a simple formula to optimize the Haigis and Hoffer Q formulae in patients with extreme hyperopia. (Am J Ophthalmol 2007; 143:920 -931. © 2007 by Elsevier Inc. All rights reserved.)
It is possible that different techniques used to measure axial length (AL) and anterior chamber depth (ACD) is the cause of discrepancy in refractive outcomes of cataract surgery. This study evaluated the agreement and repeatability of AL and ACD measurements using immersion and contact A-scan biometry techniques and compared the refractive outcomes from both techniques. Twenty four patients were evaluated for agreement and repeatability of AL and ACD measurements using the two different methods. The results were analyzed using Bland and Altman plots. Another 60 patients with age-related cataract were selected to compare the refractive outcomes between both methods. The IOL power was calculated using Sanders-Retzlaff-Kraff-Theoretical (SRK-T) equation. Refraction was determined between four to six weeks postoperatively and the results were analyzed using paired t-test. The results of this study showed good agreement between both techniques was noted with no significant difference detected between measurements (p > 0.05). Significant correlation was found in all parameters (AL: r = 0.99; p < 0.01, r = 0.99; p < 0.01) ACD: r = 0.91; p < 0.01, r = 0.97; p < 0.01). No significant difference in refractive outcomes of post cataract surgery was detected between the two techniques (p = 0.07). This study concludes that contact A-scan biometry and immersion techniques provide reliable results and should not be the cause of discrepancy in the refractive planned and outcome of cataract surgery.