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Purpose: To evaluate whether the toric intra?ocular lens (IOL) power calculation based on total corneal astigmatism (TCA) in eyes with high posterior corneal astigmatism (PCA) could result in a systematic over?correction or under?correction after operation. Methods: The present study included a mono?centric retrospective study design. The data were collected from 62 consecutive eyes during uncomplicated cataract surgery by a single surgeon with a measured PCA of 0.50 diopters (D) or higher. Toric IOL calculations were made using TCA measurements. The eyes were grouped as either “with?the?rule” (WTR) or “against?the?rule” (ATR) on the basis of the steep anterior corneal meridian. The post?operative refractive astigmatic prediction error was analyzed 1 month post?operatively using the vector analysis by the Alpins method and double?angle plots method. Results: The correction indexes were 1.14 ± 0.29 in the ATR eyes and 1.25 ± 0.18 for the WTR eyes, indicating a tendency toward over?correction. The mean over?correction was 0.22 ± 0.52D in the ATR group and 0.65 ± 0.60D in the WTR group. The magnitude of error (ME) values were significantly different from the ideal value of zero in both groups (ATR: P = 0.03; WTR: P = 0.00). No significant difference in mean absolute error (MAE) in predicted residual astigmatism was found between ATR and WTR groups (0.61 ± 0.42 D versus 0.64 ± 0.39 D; P = 0.54). The ATR group yielded better results, with 48% <0.50D prediction error in the main analysis. Conclusions: The results suggested that in cases of high PCA, the toric IOL calculation, which was performed using TCA, may cause a potential over?correction in the ATR and WTR eyes. For ATR eyes, over?correction led to slight disruption of post?operative visual quality because of the “with?the?rule” residual astigmatism after operation. Therefore, we suggested using TCA for toric IOL calculation in ATR eyes.
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@#AIM: To investigate dynamic changes of posterior corneal power and astigmatism after cataract surgery based on Pentacam three-dimensional anterior eye segment analyzer.<p>METHODS: Totally 96 elderly patients(116 eyes)with cataract underwent phacoemulsification combined with intraocular lens implantation in our hospital from January 2019 to January 2020 were selected. Parameters including anterior corneal power, posterior corneal power, flat keratometry, steep keratometry, mean keratometry, anterior corneal astigmatism, posterior corneal astigmatism, and total corneal astigmatism were obtained using Pentacam three-dimensional anterior eye segment analyzer system at postoperative 1wk, 1mo and 3mo. Spearan correlation analysis was performed on the anterior segment. <p>RESULTS: The anterior corneal power(flat keratometry, steep keratometry, mean keratometry)was lower at postoperative 1wk than that before operation, and began to return to the preoperative level at postoperative 1mo and 3mo. The posterior corneal power and total corneal power(flat keratometry, steep keratometry, mean keratometry)were higher at postoperative 1wk than before operation, and began to stabilize at postoperative 3mo. The anterior corneal astigmatism, posterior corneal astigmatism, and total corneal astigmatism were also higher at postoperative 1wk than before operation, and began to decrease and stabilize at postoperative 3mo. The anterior corneal power was significantly positively correlated with total corneal power; The posterior corneal power was significantly negatively correlated with the total corneal power, and was significantly positively correlated with its absolute value(<i>P</i><0.05). The total corneal astigmatism before operation and at postoperative 1wk and 3mo was significantly positively correlated with anterior corneal astigmatism at corresponding time points(<i>P</i><0.01), while showed no significant correlation with posterior corneal astigmatism.<p>CONCLUSION: Changes of posterior corneal power and astigmatism can be observed with 3mo of cataract surgery, and Pentacam three-dimensional anterior eye segment analyzer system can accurately assess the dynamic changes of anterior and posterior corneal power and astigmatism before and after operation, which is of great clinical value.
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Objective To analysis the distribution of posterior corneal astigmatism (PA) and evaluate the influence of keratometric astigmatism (KA) and total corneal astigmatism (TCA) on the calculation of Toric intraocular lens (Toric IOL) in patients with age-related cataract (ARC) and high corneal astigmatism.Methods An observational study design was adopted.Pentacam was used to measure 200 eyes of 181 patients with ARC and KA＞0.75 D in Affiliated Hospital of Nantong University from August 2016 to April 2017.KA,PA,TCA and anterior corneal astigmatism (AA) were recorded.The astigmatism magnitude and axis of PA was studied.The subjects were divided into astigmatism with the rule group,astigmatism against the rule group and oblique astigmatism group according to the axis of AA.The correlations of decomposition values between PA and AA or KA and TCA in each group were analyzed by Pearson linear correlation analysis.The difference of decomposition values between KA and TCA in each group was compared by paired sample t test.The type and axis of Toric IOL were calculated by online formula according to KA and TCA.This study followed the Declaration of Helsinki and written informed consent was obtained from each patient prior to any medical examination.Results The mean astigmatic magnitudes of PA was -0.32 D×93.1°.PA exceeded 0.5 D in 22 eyes (11％).The steepest posterior corneal meridian was vertically aligned in 163 eyes (81.5％).The decomposition value KP(0) and KP (45) of PA were positively correlated with those ofAA (r=0.480,P＜0.001;r=0.251,P＜0.001).The mean astigmatic magnitudes of KA and TCA were 1.44D×89.6° and 1.32 D×89.5° in astigmatism with the rule group,1.39 D×153.4° and 1.71 D×154.4° in astigmatism against the rule group and 1.13 D× 122.0° and 1.24 D× 124.2° in oblique astigmatism group.53 eyes (69.7％) had KA higher than TCA in astigmatism with the rule group.82 eyes (87.3％) had KA lower than TCA in astigmatism against the rule group;20 eyes (66.7％) had KA lower than TCA in oblique astigmatism group.There were significant differences in KP (0) between KA and TCA in different astigmatism groups (all at P＜0.001).The calculated Toric IOL type were inconsistent in 85 eyes(42.5％) and the calculated axis were inconsistent in 176 eye s (88.2％).Conclusions In patients with high corneal astigmatism,the astigmatism type of PA is mostly astigmatism against the rule.Ignoring the PA can lead to deviation of Toric IOL type selection and axis placement in some patients.For patients who cannot measure PA or TCA,the type of Toric IOL should be adjusted appropriately.
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PURPOSE: To compare the effect of posterior corneal astigmatism on the estimation of total corneal astigmatism using anterior corneal measurements (simulated keratometry [K]) between eyes with keratoconus and healthy eyes. METHODS: Thirty-three eyes of 33 patients with keratoconus of grade I or II and 33 eyes of 33 age- and sex-matched healthy control subjects were enrolled. Anterior, posterior, and total corneal cylinder powers and flat meridians measured by a single Scheimpflug camera were analyzed. The difference in corneal astigmatism between the simulated K and total cornea was evaluated. RESULTS: The mean anterior, posterior, and total corneal cylinder powers of the keratoconus group (4.37 ± 1.73, 0.95 ± 0.39, and 4.36 ± 1.74 cylinder diopters [CD], respectively) were significantly greater than those of the control group (1.10 ± 0.68, 0.39 ± 0.18, and 0.97 ± 0.63 CD, respectively). The cylinder power difference between the simulated K and total cornea was positively correlated with the posterior corneal cylinder power and negatively correlated with the absolute flat meridian difference between the simulated K and total cornea in both groups. The mean magnitude of the vector difference between the astigmatism of the simulated K and total cornea of the keratoconus group (0.67 ± 0.67 CD) was significantly larger than that of the control group (0.28 ± 0.12 CD). CONCLUSIONS: Eyes with keratoconus had greater estimation errors of total corneal astigmatism based on anterior corneal measurement than did healthy eyes. Posterior corneal surface measurement should be more emphasized to determine the total corneal astigmatism in eyes with keratoconus.
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Humanos , Astigmatismo , Córnea , Queratocono , MeridianosRESUMEN
AIM:To assess the anterior corneal astigmatism (ACA)and posterior corneal astigmatism (PCA) patterns across various age groups.We also evaluated the association between magnitudes and axes of the ACA and PCA across these age groups.METHODS:The present study was a cross-sectional analysis of clinical data of 381 eyes.We converted the clinical astigmatic notation to vector notation for analysis of ACA and PCA.We estimated the correlation between magnitude and axes of the ACA and PCA in the whole population and in four age groups (5-19,20-39,40-59,and ≥ 60y).We used random effects linear regression models for estimating the association between the magnitudes of ACA and PCA.RESULTS:The mean of the magnitude of the ACA (3.59D) and the PCA (0.50D) was highest in children (5 to 9y).Overall,the magnitude of the ACA ranged from 0D to 10.0 Diopters (D) and the magnitude of the PCA ranged from 0 to 3.5 D.There was a significant correlation between the ACA and the PCA in the younger age group (r=0.85,P＜0.001).In those 60y or older,the PCA increased by 0.04 units (95％ confidence intervals:0.005,0.07;P=0.03) with each unit increase in the ACA,the increase was the smallest in this age group.CONCLUSION:It will be prudent to measure the both the magnitude and axis of the PCA,particularly in those above 60y rather than rely on rule-of-thumb calculations based on ACA parameters for IOL power calculation.
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PURPOSE: To determine if there is a difference in surgically induced astigmatism (SIA) of the posterior corneal surface between superior and temporal incision and its effect on total corneal power in patients who underwent clear corneal incision cataract surgery. METHODS: A retrospective study of 81 patients (84 eyes) who underwent clear corneal incision phacoemulsification by one surgeon. Patients were divided into two groups according to the steep axis: the temporal and superior groups. Anterior, posterior and total corneal SIA (simulated keratometry [Sm K], posterior keratometry [PK] and total corneal power [TCP] respectively) were measured using autorefractive keratometry (ARK) and dual Scheimpflug imaging before and after surgery. RESULTS: There were 61 eyes with temporal incision and 23 eyes with superior incision. The mean SIA was larger in the superior incision group than in the temporal incision group according to ARK, Sm K, PK and TCP (p < 0.05). There were no significant cylindrical changes in ARK in the temporal incision group, however, there was a significant decrease in the superior incision group before and after the operation (p < 0.05). Change in the amount and axis of PK before and after operation were not significantly different, for both incision groups. There was a significant correlation between post-operative TCP and both pre-operative ARK and Sm K for both groups. However, there was no correlation between post-operative TCP and pre-operative PK. In all patients, when pre-operative PK was more than 0.5 D, SIA-ARK, SIA-Sm K and SIA-TCP were all significantly larger than when pre-operative PK was less than 0.5 D, whereas SIA-PK was not. When pre-operative PK was more than 0.5 D, there were no significant differences in SIA-ARK, SIA-Sm K, SIA-PK or SIA-TCP in the temporal incision group. However, SIA-ARK was significantly larger in the superior incision group. CONCLUSIONS: There was no significant cylindrical change in PK before and after operation in both the temporal and superior incision groups. Therefore, when predicting post-operative TCP, it might be meaningful to consider SIA-ARK and SIA-Sm K.
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Humanos , Astigmatismo , Catarata , Facoemulsificación , Estudios RetrospectivosRESUMEN
PURPOSE: To assess the changes in anterior, posterior, and total corneal astigmatism after cataract surgery with on-axis clear corneal incision cataract surgery. METHODS: This study included 48 eyes (24 eyes with 'with-the-rule [WTR]' and 24 eyes with 'against-the-rule [ATR]') that underwent phacoemulsification and intraocular lens insertion through on-axis clear corneal incision. The ATR group with vertically steep axis of posterior corneal astigmatism was divided into subgroups 1 and 2 for the opposite axis. Autorefraction, uncorrected and best-corrected visual acuities were measured. Corneal astigmatism (anterior, posterior and total) was measured using Pentacam(R) preoperatively and 1 week, 1 month, and 2 months postoperatively. RESULTS: Multivariate linear regression analysis of preoperative data showed positive correlations among anterior, posterior and total astigmatism. Anterior corneal astigmatism showed a significant decrease in both WTR and ATR groups in all measured points (all p 0.05) and significant decrease in the ATR subgroup 1 (p 0.05). According to correlation analysis based on trend line equations, 1.7 diopters of anterior astigmatism could expect 0.3 diopters of posterior astigmatism and 0.5 diopters of total astigmatism for the WTR group and 0.4 diopters of anterior astigmatism could expect 0.2 diopters of posterior astigmatism and 0.4 diopters of total astigmatism for the ATR group. CONCLUSIONS: Considering the majority of cataract patients have vertically steep posterior corneal astigmatism, temporal incision for ATR patients is generally effective. Moreover, for patients with WTR astigmatism of more than 1.7 diopters or ATR astigmatism greater than 0.8 diopters, additional preoperative correction based on posterior astigmatism is needed for more precise prediction of postoperative total corneal astigmatism.
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Humanos , Astigmatismo , Vértebra Cervical Axis , Catarata , Lentes Intraoculares , Modelos Lineales , Facoemulsificación , Agudeza VisualRESUMEN
PURPOSE: To analyze the change in posterior corneal astigmatism and total corneal astigmatism in patients with anterior corneal astigmatism less than 1.0 diopter (D). METHODS: In the present study we evaluated 52 eyes with anterior corneal astigmatism less than 1.0 D. Patients were divided into 2 groups according to steep axis: Group 1 included 33 eyes with within-the-rule (WTR) astigmatism and Group 2 included 19 eyes with against-the-rule (ATR) astigmatism. Anterior, posterior and total corneal astigmatism were measured using Scheimpflug imaging (Pentacam(R)). RESULTS: In Group 1, preoperative anterior astigmatism, posterior astigmatism and total astigmatism were 0.55 +/- 0.44 D, 0.31 +/- 0.14 D and 0.30 +/- 0.72 D, respectively. At postoperative 2 months, anterior astigmatism, posterior astigmatism and total astigmatism were 0.51 +/- 0.67 D, 0.31 +/- 0.15 D and 0.35 +/- 0.81 D, respectively. There was no statistically significant difference between preoperative and postoperative anterior, posterior and total corneal astigmatism in Group 1. In Group 2, preoperative anterior astigmatism, posterior astigmatism and total astigmatism were -0.48 +/- 0.46 D, 0.26 +/- 0.09 D and -0.51 +/- 0.65 D, respectively. At postoperative 2 months, anterior astigmatism, posterior astigmatism and total astigmatism were -0.17 +/- 0.68 D, 0.25 +/- 0.13 D and -0.30 +/- 0.55 D, respectively. There was no statistically significant difference between preoperative and postoperative anterior, posterior and total corneal astigmatism in the 2 groups. There was no statistical correlation between preoperative posterior corneal astigmatism and postoperative 2 months total corneal astigmatism. After vector analysis, surgically induced astigmatism (SIA) of the anterior and total astigmatism in Group 1 were 0.03 D @ 30degrees and 0.07 D @ 74degrees, respectively, and in Group 2 were 0.27 D @ 100degrees and 0.36 D @ 86degrees, respectively. CONCLUSIONS: In patients with preoperative total corneal astigmatism less than 1.0 D, posterior corneal astigmatism had a small effect on postoperative total corneal astigmatism.