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Comparison of predicted and measured axial length for ophthalmic lens design.

ABSTRACT: Ocular parameters have been applied to ophthalmic lens designs in order to satisfy individual wearers. An axial length (AL) of them can be used in individual ophthalmic lens designs. Our aim was to propose a reliable formula that predicts an individual's AL using the corneal radius and refractive error, and to demonstrate the applicability of this formula. A total of 348 subjects underwent keratometry, objective and subjective refraction, and AL measurement. The formula of calculated AL for prediction obtained from the original Gullstrand simplified schematic eye: calculated AL = (24.00 × aveK/7.80)-(SE × 0.40), where aveK and SE denote average corneal radius and spherical equivalent, respectively. Calculated AL was 24.50 ± 1.83 mm, which was 0.18 ± 0.47 mm longer than the measured value of 24.32 ± 1.73 mm (p < 0.001). The proportion showing the differences between the calculated and measured ALs were 284 eyes (40.8%) for 0.00-0.25 mm, 525 eyes (75.4%) for less than 0.50 mm, 665 eyes (95.5%) for less than 1.00 mm, and 31 eyes (4.5%) for more than 1.01 mm. Correlation coefficient showed a very high correlation between calculated and measured ALs (r = 0.967, p < 0.001), and higher in the myopic than in the hyperopic group. The mean difference was 0.18 mm; the 95% limit of agreement was +1.10--0.75 mm in all groups. Agreement was better in hyperopic eyes than myopic eyes. Prediction from calculation of AL with a formula using the corneal radius and SE provides an alternative method to direct measurements of AL, especially in the restricted environment, which can't use biometric equipment for personalized ophthalmic lens design.

SUBMITTER: Kim HS

PROVIDER: S-EPMC6322735 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Comparison of predicted and measured axial length for ophthalmic lens design.

Kim Hyeong-Su HS Yu Dong-Sik DS Cho Hyun Gug HG Moon Byeong-Yeon BY Kim Sang-Yeob SY

PloS one 20190107 1

Ocular parameters have been applied to ophthalmic lens designs in order to satisfy individual wearers. An axial length (AL) of them can be used in individual ophthalmic lens designs. Our aim was to propose a reliable formula that predicts an individual's AL using the corneal radius and refractive error, and to demonstrate the applicability of this formula. A total of 348 subjects underwent keratometry, objective and subjective refraction, and AL measurement. The formula of calculated AL for pred ...[more]

PMID: 30615674

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Project description:BackgroundA major focus of toric intraocular lens (IOL) implantation is the rotational stability, especially in the patients with long axial length (AL). In this study, we aimed to evaluate the clinical outcomes after implantation of TECNIS toric IOL in eyes with long AL and identify factors influencing their early-stage stability with preoperative corneal astigmatism.MethodsThe study population consisted of 64 eyes from 52 cataract patients, and these patients had preoperative corneal astigmatism between 1.0 and 3.7 diopters (D) and underwent phacoemulsification and TECNIS toric IOL implantation. Ophthalmic biological measurements were carried out preoperatively, including AL, anterior chamber depth (ACD), lens thickness (LT), vitreous length (VL), anterior chamber volume (ACV), sulcus-to-sulcus (STS) and keratometric value (K). Clinical examinations, including visual acuity, manifest refraction, keratometry, digital anterior segment photographs with pupillary dilation, were performed at 1 and 3 months after surgery.ResultsThe mean best corrected distance visual acuity (BCDVA) was improved from 0.93 ± 0.35 logarithms of the minimal angle of resolution (logMAR) preoperatively to 0.07 ± 0.10 logMAR postoperatively at 3 months after surgery. The mean residual astigmatism (RAS) was 0.91 ± 0.74D at 3 months, which was significantly decreased compared with the preoperative corneal astigmatism of 1.71 ± 0.55 D. The mean absolute rotation of TECNIS toric IOL at 1 and 3 months was 7.42 ± 11.32 degree (°) (0-79°) and 7.48 ± 11.19°(0-79°), respectively. The mean area of capsulorhexis and the overlapped area between capsulorhexis and IOL optic intraoperatively was 21.04 ± 3.30 mm2 and 7.40 ± 2.87 mm2.A positive correlation was found between IOL rotation and the area of capsulorhexis (p = 0.017) at 3 months after surgery. No correlation was found between IOL rotation and AL (p = 0.876), ACD (p = 0.387), LT (p = 0.523), VL (p = 0.546), ACV (p = 0.480), STS (p = 0.884), K1 (p = 0.429), K2 (p = 0.644), average of K1 and K2 (p = 0.520), intraoperative IOL axial direction (p = 0.396), preoperative corneal astigmatism (p = 0.269) or the overlapped area between capsulorhexis and IOL optic intraoperatively (p = 0.131) .ConclusionsThe large CCC was a risk factor for toric IOL rotation. An appropriately smaller sized CCC was conducive to increase the rotational stability of TECNIS toric IOL implantation in cataract cases with long AL.

Project description:BackgroundPreoperative evaluation of macular disorders is crucial to predict postoperative visual outcomes among patients with cataract. The swept-source optical coherence tomography (SS-OCT) based optical biometer was proved to be useful in screening macular pathology, while the impact of lens opacities and axial lengths on macular disease screening using SS-OCT based optical biometer remained unknown. This study aimed to evaluate the influence of lens opacities and axial lengths on foveal image quality detected by SS-OCT-based optical biometer, as well as sensitivity and specificity for the detection of macular diseases.MethodsThis was a diagnostic accuracy study that retrospectively included patients who underwent preoperative cataract examinations at our hospital between November 2020 and June 2021. All patients underwent SS-OCT based optical biometer and spectral-domain OCT (SD-OCT). The SD-OCT was the golden standard for diagnosing macular diseases. Sensitivity, specificity, and receiver operating characteristic (ROC) were calculated to evaluate the value of foveal SS-OCT scans for the detection of macular disease.ResultsOf the 224 eyes enrolled in the study, 82 eyes were diagnosed with macular disease by SD-OCT. The foveal image was almost indistinguishable due to poor quality when the mean grayscale of the image was less than 40. The posterior subcapsular opacity score and the axial length were significantly correlated with the gray density of the foveal image (r=-0.70, P<0.0001 and r=-0.40, P<0.0001). After excluding cases with indistinguishable foveal images (subcapsular opacities score ≥3.5, axial length ≥28.9 mm), the SS-OCT yielded 68% (95% confidence interval, 0.54-0.79) sensitivity and 87% (95% confidence interval, 0.78-0.92) specificity in 136 eyes.ConclusionsRoutine SS-OCT based biometric measurement for the evaluation of macular pathology simultaneously prior to cataract surgery is suggested except for patients with advanced cataract (posterior subcapsular opacities score ≥3.5) and long axial length (≥28.9 mm).

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Comparison of predicted and measured axial length for ophthalmic lens design.

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Comparison of predicted and measured axial length for ophthalmic lens design.

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