Accuracy of intraocular lens power calculation using Scheimpflug tomography and OKULIX ray tracing software in corneal scarring

Mapping Intimacies ◽

10.21203/rs.2.18091/v2 ◽

2020 ◽

Author(s):

karim Mahmoud nabil

Keyword(s):

Visual Acuity ◽

Ray Tracing ◽

Intraocular Lens ◽

Pearson Correlation ◽

Power Calculation ◽

Corneal Scarring ◽

Iol Power Calculation ◽

Intraocular Lens Power ◽

Iol Power ◽

Lens Power

Abstract Background: To evaluate the accuracy of intraocular lens power (IOL) calculation using Scheimpflug tomography and OKULIX ray tracing software in corneal scarring. Methods: This study was conducted on 40 consecutive eyes, 20 cases with corneal scarring and coexisting cataract, and 20 controls with clear cornea, which underwent uneventful phacoemulsification and IOL implantation following Scheimpflug tomography and OKULIX ray tracing software and third generation IOL power calculation formulas for IOL power calculation. Accuracy of IOL power calculation was evaluated by subtracting expected and achieved spherical refraction 3 months postoperatively and was recorded as mean absolute error (MAE). Distance uncorrected visual acuity (UCVA) for each eye was measured using Snellen chart preoperatively and 3 months postoperatively; visual acuity was scored and converted to the logarithm of the minimum angle of resolution (LogMar).Values were recorded as mean ±SD (standard deviation). Student t-test (t) and Mann Whitney test (U) were used for parametric comparison of the means. Intra class Correlation (ICC) coefficient and Pearson correlation Coefficient (r) were used to assess agreement. A P value less than 0.05 was considered statistically significant. Results: In cases of corneal scarring, 20 eyes (100 %) yielded a postoperative spherical refraction which differed less than 1 diopter (D) from predicted, in 16 eyes (80 %) the postoperative spherical refraction was within 0.50 D from expected. The MAE was 0.2 D in cases, which did not differ significantly compared to controls (MAE 0.1 D). In corneal scarring cases, distance UCVA showed significant improvement from 1.3 Log Mar (Snellen equivalent 20/400) preoperatively to 0.5 Log Mar (Snellen equivalent 20/60) 3 months postoperatively. Conclusion: Scheimpflug tomography combined with OKULIX ray tracing software for calculation of IOL power provides accurate results in cases of corneal scarring.

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Accuracy of intraocular lens power calculation using Scheimpflug tomography and OKULIX ray tracing software in corneal scarring

10.21203/rs.2.18091/v1 ◽

2019 ◽

Author(s):

Karim Mahmoud Nabil

Keyword(s):

Visual Acuity ◽

Ray Tracing ◽

Intraocular Lens ◽

Absolute Error ◽

Power Calculation ◽

Corneal Scarring ◽

Iol Power Calculation ◽

Intraocular Lens Power ◽

Iol Power ◽

Lens Power

Abstract Background: To evaluate the accuracy of intraocular lens power (IOL) calculation using Scheimpflug tomography and OKULIX ray tracing software in corneal scarring. Methods: This study was conducted on 40 consecutive eyes, 20 cases with corneal scarring and coexisting cataract, and 20 controls with clear cornea, which underwent uneventful phacoemulsification and IOL implantation following Scheimpflug tomography and OKULIX ray tracing software and third generation IOL power calculation formulas for IOL power calculation. Accuracy of IOL power calculation was evaluated by subtracting expected and achieved spherical refraction 3 months postoperatively and was recorded as mean absolute error (MAE). Distance uncorrected visual acuity (UCVA) for each eye was measured using Snellen chart preoperatively and 3 months postoperatively; visual acuity was scored and converted to the logarithm of the minimum angle of resolution (LogMar). Results: In cases of corneal scarring, 20 eyes (100 %) yielded a postoperative spherical refraction which differed less than 1 diopter (D) from predicted, in 16 eyes (80 %) the postoperative spherical refraction was within 0.50 D from expected. The MAE was 0.2 D in cases, which did not differ significantly compared to controls (MAE 0.1 D). In corneal scarring cases, distance UCVA showed significant improvement from 1.3 Log Mar (Snellen equivalent 20/400) preoperatively to 0.5 Log Mar (Snellen equivalent 20/60) 3 months postoperatively. Conclusion: Scheimpflug tomography combined with OKULIX ray tracing software for calculation of IOL power provides accurate results in cases of corneal scarring.

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Accuracy of intraocular lens power calculation formulas in a steep cornea: A case report

10.36811/irjo.2021.110012 ◽

2021 ◽

pp. 29-33

Author(s):

Ehab M Ghoneim ◽

Ahmed A Hassaan

Keyword(s):

Intraocular Lens ◽

Power Calculation ◽

Intraocular Lens Power Calculation ◽

Iol Power Calculation ◽

Intraocular Lens Power ◽

Manifest Refraction ◽

Iol Power ◽

Lens Power ◽

The Right ◽

Lens Power Calculation

There is no enough knowledge about the accuracy of intraocular lens (IOL) power calculation formulas in steep corneas. This study may be the first one that compares the accuracy of the SRK II formula with Holladay1, Hoffer Q and Haigis formulas in steep corneas. We reported a case of a 60-year-old female, with a cataract in the left eye and with a steep cornea. We used the modern formulas; Holladay1, Hoffer Q and Haigis. The result (+7.0D) was unexpected compared to the manifest refraction and to the IOL power calculated in the right eye using the same formulas which was (+17.0D). We implanted (+12.0D) Sensar 1-piece IOL depending on our clinical experience. The post-operative refraction was (+0.00/-1.75axis106). Postoperative, we used the patient data to find the best formula in this case. We found that the SRK II (A118) result was (+11.5D) and thus this formula was the most accurate in this case. Keywords: SRK II; Holladay1; Hoffer Q; Haigis

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Accuracy of Intraocular Lens Power Calculation Formulas for Highly Myopic Eyes

Journal of Ophthalmology ◽

10.1155/2016/1917268 ◽

2016 ◽

Vol 2016 ◽

pp. 1-7 ◽

Cited By ~ 9

Author(s):

Yichi Zhang ◽

Xiao Ying Liang ◽

Shu Liu ◽

Jacky W. Y. Lee ◽

Srinivasan Bhaskar ◽

...

Keyword(s):

Intraocular Lens ◽

Absolute Error ◽

Power Calculation ◽

Prediction Errors ◽

Intraocular Lens Power Calculation ◽

Iol Power Calculation ◽

Predictive Error ◽

Intraocular Lens Power ◽

Iol Power ◽

Lens Power

Purpose.To evaluate and compare the accuracy of different intraocular lens (IOL) power calculation formulas for eyes with an axial length (AL) greater than 26.00 mm.Methods.This study reviewed 407 eyes of 219 patients with AL longer than 26.0 mm. The refractive prediction errors of IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) using User Group for Laser Interference Biometry (ULIB) constants were evaluated and compared.Results.One hundred seventy-one eyes were enrolled. The Barrett Universal II formula had the lowest mean absolute error (MAE) and SRK/T and Haigis had similar MAE, and the statistical highest MAE were seen with the Holladay and Hoffer Q formulas. The interquartile range of the Barrett Universal II formula was also the lowest among all the formulas. The Barrett Universal II formulas yielded the highest percentage of eyes within ±1.0 D and ±0.5 D of the target refraction in this study (97.24% and 79.56%, resp.).Conclusions.Barrett Universal II formula produced the lowest predictive error and the least variable predictive error compared with the SRK/T, Haigis, Holladay, and Hoffer Q formulas. For high myopic eyes, the Barrett Universal II formula may be a more suitable choice.

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Comparison of accuracy of Partial Coherence Interferometry based Zeiss IOL Master 500 and Immersion Ultrasound [Ocuscan RXP] for intraocular lens power calculation

Asian Journal of Ophthalmology ◽

10.35119/asjoo.v14i4.154 ◽

2016 ◽

Vol 14 (4) ◽

Author(s):

Vijaya Pai ◽

Divya Shastri ◽

Asha Kamath

Keyword(s):

Intraocular Lens ◽

Refractive Error ◽

Partial Coherence ◽

Power Calculation ◽

Partial Coherence Interferometry ◽

Iol Power Calculation ◽

Intraocular Lens Power ◽

Iol Power ◽

Group B ◽

Lens Power

Aim: To compare accuracy of intraocular lens power (IOL) calculation using Partial coherence Interferometry based Carl Zeiss IOL master 500 and Immersion ultrasound (Alcon Ocuscan RXP). Methods: A prospective randomized study of patients who underwent clear corneal phacoemulsification with foldable (IOL) by a single surgeon, during the period September 2010 to 2012. Group A included those patients in whom IOL power calculation using Immersion ultrasound (Ocuscan RXP) was used. Group B included those patients in whom IOL power calculation using Partial coherence Interferometry based Zeiss IOL master was used. SRK T formula was used to calculate the IOL power in both the groups. Postoperative final refraction was done at 6 weeks. Unaided visual acuity and best corrected visual acuity was assessed. Postoperative refractive error was compared with predicted refractive error with each biometry method. Statistical analysis was done using SPSS 16.5. Continuous variables expressed as mean (standard deviation). P < 0.05 was considered significant.Results: There were 50 patients in Group A, 44 patients in Group B. Axial length of the patients varied from 22-26mm in both the groups. The postoperative refraction using Ocuscan, 88% had refractive error ≤± 0.5 D, 94% had ≤±1.00D, and 100% had ≤±2.0D of emmetropia. Using Zeiss IOL Master 72.7% had ≤± 0.5 D, 100% had ≤±1.00D of refractive error. Difference in absolute postoperative refractive error using Ocuscan vs. IOL Master was not statistically significant. Conclusion: In our study both ultrasound Ocuscan and IOL master were accurate in calculating intraocular lens power and achieving postoperative refraction closer to emmetropia.

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Intraocular Lens Power Calculation – Still Searching for the Holy Grail

European Ophthalmic Review ◽

10.17925/eor.2015.09.01.13 ◽

2015 ◽

Vol 09 (01) ◽

pp. 13

Author(s):

Nino Hirnschall ◽

Oliver Findl ◽

◽

Keyword(s):

Intraocular Lens ◽

Power Calculation ◽

Refractive Outcome ◽

Intraocular Lens Power Calculation ◽

Iol Power Calculation ◽

Lens Position ◽

Intraocular Lens Power ◽

Iol Power ◽

Lens Power ◽

Lens Power Calculation

Since the introduction of optical biometry and modern intraocular lens (IOL) power calculation formulae, the refractive outcome after cataract surgery improved significantly. This is necessary, as patient demand for spectacle independence is increasing. However, especially when it comes to short and long eyes, all formulae have their difficulties in predicting the effective lens position – and, therefore, the post-operative refractive outcome. This review summarises the development of IOL power calculation formulae, explains their basics and presents some alternative calculation methods.

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