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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:BACKGROUND:A 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. METHODS:The 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. RESULTS:The 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) . CONCLUSIONS:The 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:PurposeTo test the hypothesis that pterygium presents with both refractive and anatomical changes, especially short axial length.MethodsA retrospective, hospital-based cross-sectional study included 521 eyes from 521 patients who were enrolled through a community survey by Shanghai Heping Eye Hospital was conducted. Patients with primary pterygium in at least 1 eye were considered the pterygium group, and those with normal eyes were considered the nonpterygium group. The prevalence and length of pterygium, refractive characteristics including spherical power, astigmatism, corneal curvature, and anatomical parameters including axial length, anterior chamber depth, endothelial cell density, and corneal thickness were compared between groups.ResultsFive hundred twenty-one eyes of 521 patients (214 men and 307 women) with a mean age of 70.5 ± 7.6 years were included in the study. The prevalence of hyperopia (81.6%, 65.1%, P = 0.001), axial length (23.1 ± 1.2 mm, 24.2 ± 2.4 mm, P < 0.001), anterior chamber depth (2.9 ± 0.3 cm, 3.1 ± 0.4 cm, P = 0.001), flat K value (42.94 ± 2.16 diopters, 43.73 ± 1.48 diopters, P = 0.002), Kmax (51.13 ± 7.74 diopters, 47.49 ± 5.62 diopters, P < 0.001), and spherical power (0.97 ± 2.40 diopters, -0.82 ± 4.40 diopters, P < 0.001) were statistically different between the pterygium and nonpterygium groups. Age (r = -0.21, P = 0.025), corneal astigmatism (r = -0.41, P < 0.001), flat K value (r = -0.39, P < 0.001), and endothelial cell density (r = -0.33, P = 0.001) were all negatively correlated with the length of pterygium. The prevalence of pterygium and severe pterygium over 3 mm were statistically different according to the severity of hyperopia (P < 0.001) and axial length (P < 0.001). Stratified ? analysis showed that axial length, rather than hyperopia, was a related factor to pterygium (odds ratio = 5.23, 95% confidence interval: 2.50-10.93).ConclusionsWe conclude from our study that the prevalence of pterygium is related to small eye size. SDF-1/CXCR4 signaling may play a vital role in pterygium and shorter axial length. Further study focused on SDF-1/CXCR4 signaling will be needed.

Project description:Purpose:To assess the efficacy and safety of a novel ophthalmic viscosurgical device-free (OVD-free) method for posterior chamber phakic intraocular lens (PIOL) implantation in myopic eyes. Methods:In this retrospective cohort study, the medical records of myopic eyes that underwent PIOL (Implantable Collamer Lens, ICL) implantation for myopia correction at the Eye Hospital of Wenzhou Medical University between May 2015 and March 2017 were reviewed. A total of 49 eyes with complete data that met follow up requirements (2?h, 1?day, 1?week, 3?months postoperatively) were recruited. Based on the surgical techniques used, the eyes were divided into the OVD-free method group and the standard method group. The clinical data, including intraocular pressure (IOP), corrected distance visual acuity (CDVA) and spherical equivalent (SE), at each follow-up were collected for comparison. Endothelial cell loss and complications were also investigated. Results:Twenty-one eyes received the standard method, and 28 eyes received the OVD-free method. A rise in IOP >?22?mmHg at 2?h was noted in 14 eyes (66.7%) in the standard group and none (0%) in the OVD-free group (p?<?0.001). The rise in IOP from baseline was significantly higher at 2?h in the standard group (10.5?±?5.2?mmHg vs. 2.2?±?3.3?mmHg, difference: 8.3, 95% CI 5.8 to 10.8; p <?0.001). There was a significant difference in the time course of LogMAR CDVA changes between the two groups (p?=?0.047). The LogMAR CDVA was significantly better in the OVD-free method group compared to the standard group at 1?day (-?0.076, 95% CI -?0.134 to -?0.018; p?=?0.012), 1?week (-?0.071, 95% CI -?0.135 to -?0.007; p?=?0.03), but not at 3?months (-?0.046, 95% CI -?0.107 to 0.015; p?=?0.134). There was no significant difference in the time course of SE changes between the two groups (p?=?0.471; p?=?0.705). In the OVD-free group, mean endothelial cell loss was 4.6% at 3?months (2522?±?281 vs. 2407?±?226 cells/mm2, difference: -115, 95% CI -?295 to 65; p?=?0.187). No complications were reported in both groups except for the early IOP elevation in the standard group during the observation period. Conclusions:The OVD-free method is safe and efficient for ICL implantation. It can be a safer method of ICL implantation compared to the standard method in that it completely eliminates ophthalmic viscoelastic devices-related complications without causing additional complications.

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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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