Toric intraocular lenses in eyes with with-the-rule, against-the-rule, and oblique astigmatism: One-year results

Simultaneous Presbyopia and Astigmatism Correction with a Novel Trifocal Toric Intraocular Lens—A One-Year Follow-Up

The current investigation evaluates the efficiency of the trifocal toric Liberty 677MTY intraocular lens (IOL) in correcting preoperative corneal astigmatism in cataract patients demanding spectacle independence. The retrospective evaluation included 28 eyes of 15 patients with preoperative corneal astigmatism of at least 1.0 Dioptre (D). All patients were followed up for one year postoperatively. Residual refractive errors and visual acuities at multiple distances were measured. Binocular visual acuity and contrast sensitivity defocus curves were plotted. Visual functions and patient satisfaction were assessed. The efficiency of astigmatism correction was determined using the vector analysis method. The mean spherical equivalent refraction (SEQ) improved from 2.72 ± 1.62 D to 0.10 ± 0.48 D. The cylindric refraction decreased from 1.18 ± 0.45 D to 0.16 ± 0.31 D. Vector analysis proved efficient astigmatism correction with a centroid of 0.10 ± 0.34 D at 161°. Ninety-two percent of eyes resulted within 0.5 D from the target refraction. Visual acuities were 0.1 logMAR or better from +1.0 to −3.5 D defocus values. Visual tasks could be performed without major difficulties. Our patients were highly satisfied. Refractive and visual outcomes with the investigated presbyopia-correcting toric IOL are predictable and the lens provides excellent trifocal vision.

Predicted vs measured posterior corneal astigmatism for toric intraocular lens calculations

PURPOSE

To evaluate the astigmatic correction obtained with a toric intraocular lens using the keratometric readings (Ks) from a swept-source optical coherence tomography (SS-OCT) biometer and the Barrett toric formula with its predicted posterior corneal astigmatism (PCA) value and to compare the results with those expected by using the OCT Ks and a measured PCA from a scheimpflug topographer and by using the SimKs and the measured PCA from the Scheimpflug topographer.

SETTING

Private practice, Lynwood, California.

DESIGN

Retrospective observational study.

METHODS

All measurements were performed by the SS-OCT biometer and the Scheimpflug topographer and using the Barrett toric formula.

RESULTS

We evaluated 122 eyes of 122 patients. The mean absolute errors in predicted residual astigmatism for the entire series were 0.41 ± 0.19 diopters (D) (0.00 to 0.85 D) using the OCT Ks and predicted PCA, 0.45 ± 0.25 D (0.00 to 1.01 D) using the OCT Ks and measured PCA, and 0.49 ± 0.25 D (0.00 to 1.30 D) using the SimKs and measured PCA. The statistically significant differences between the errors had a P value of .062 for the entire series (n = 122), .26 for the subgroup with against-the-rule astigmatism (n = 68), .47 for the subgroup with oblique astigmatism (n = 11), and .05 for the subgroup with with-the-rule astigmatism (n = 43). The percentage of eyes within ±0.50 D were 74% (n = 90), 71% (n = 87) and 64% (n = 78) (P = .13) and within ±0.75 D were 99% (n = 121), 95% (n = 116) and 84% (n = 102) (P < .001), respectively.

CONCLUSIONS

The Barrett toric formula and its predicted PCA performed better with the OCT K readings than with the topographer SimKs and a measured PCA.

Long-term outcomes of cataract surgery with toric intraocular lens implantation by the type of preoperative astigmatism

Surgical outcomes of toric intraocular lens (IOL) implantation for 8 years after surgery were analyzed. Data were retrospectively collected in 176 eyes of 176 patients before and 1 month, 1, 3, 5, and 8 years after phacoemulsification and implantation of a toric IOL. Preoperative corneal and postoperative manifest astigmatism was analyzed by converting to power vector notations; horizontal/vertical (J₀) and oblique (J₄₅) astigmatism components. Toric IOL implantation significantly reduced pre-existing astigmatism by decreasing J₀ in eyes with preoperative with-the-rule (WTR) astigmatism, increasing J₀ in eyes with against-the-rule (ATR) astigmatism, and correcting J₄₅ in eyes with oblique astigmatism. After surgery, the eyes with preoperative ATR astigmatism showed a significant ATR astigmatic shift, and J₀ at 5 and 8 years was significantly smaller than that at 1 month postoperatively. Uncorrected distance visual acuity was also significantly worse at 5 and 8 years than at 1 month postoperatively. In eyes with WTR and oblique astigmatism, the effects of toric IOLs on astigmatism and visual acuity were sustained for 8 years. The long-term astigmatism-correcting effects did not differ among the models of toric IOL used in this study, SN6AT3–8 (Alcon Laboratories). In eyes with preoperative ATR astigmatism, astigmatism-correcting effects of toric IOLs decreased at 5 years and later postoperatively, indicating that overcorrection may be considered at the time of cataract surgery. In eyes with WTR and oblique astigmatism, the effects of toric IOLs were maintained throughout the 8-year follow-up period.

Impact of small incision sutureless cataract surgery on the natural course of astigmatism in 10 to 20 years

PURPOSE

To retrospectively assess astigmatic changes over 10- and 20-years after small incision cataract surgery.

SETTING

Five ophthalmic surgical sites in Japan.

DESIGN

Retrospective case series.

METHODS

Data were collected from patients who had undergone phacoemulsification and implantation of an intraocular lens (IOL) through a 2.2- to 2.4-mm incision. Preoperative corneal and postoperative manifest astigmatism were converted to power vector notations: horizontal/vertical (J0) and oblique (J45) astigmatism components.

RESULTS

In 422 eyes of 422 patients who were followed up for 10 years, data before and at 1 month, and 1, 3, 5, 8, and 10 years after surgery were analysed. The mean J0 decreased significantly (p<0.001, repeated measures analysis of variance) with an against-the-rule (ATR) shift of 0.363 ± 0.433 D over 10 years, but the mean J45 did not change significantly (p=0.150). Double-angle plot analyses also showed similar ATR shifts in all astigmatism groups. In the subgroup analysis conducted in 34 patients who were followed up for 20 years, J0 declined significantly (p<0.001) by 0.649 ± 0.576 D over 20-year follow-up, while J45 did not (p=0.516). The postoperative changes in J0 and J45 were not significantly different between eyes with preoperative with-the-rule, ATR, or oblique astigmatism.

CONCLUSIONS

Postoperative astigmatism continued to shift towards ATR during the follow-up period of 20 years after small incision cataract surgery, which appears to reflect the natural course of corneal astigmatic changes that commonly occur with aging. ATR astigmatic shifts were similar in both pattern and magnitude regardless of the type of preoperative astigmatism.

Long-term changes in the refractive effect of a toric intraocular lens on astigmatism correction

Purpose

To examine the long-term changes in the astigmatism-correcting effect of a toric intraocular lens (IOL) after stabilization of surgically induced astigmatic changes due to cataract surgery.

Methods

Unilateral eyes of 120 patients that received a toric IOL for against-the-rule (ATR) or with-the-rule (WTR) astigmatism were enrolled. Manifest refractive and anterior corneal astigmatism, and ocular residual astigmatism which is mainly derived from internal optics were examined preoperatively, at approximately 2 months postoperatively (baseline) and at 5 ~ 10 years postbaseline. The astigmatism was decomposed to vertical/horizontal (Rx) and oblique components (Ry), which was compared between baseline and 5 ~ 10 years postbaseline.

Results

In the eyes having ATR astigmatism, the mean Rx and Ry of the manifest refractive and corneal astigmatism significantly changed toward ATR astigmatism between the baseline and 5 ~ 10 years postbaseline (p ≤ 0.0304), but those of ocular residual astigmatism did not change significantly between the 2 time points. In the eyes having WTR astigmatism, the Rx and Ry of refractive, corneal, and ocular residual astigmatism did not change significantly between the 2 time points. Double-angle plots revealed an ATR shift in refractive and corneal astigmatism and no marked change in the ocular residual astigmatism in the eyes with ATR astigmatism, and there is no change in this astigmatism in the eyes with WTR astigmatism.

Conclusion

The long-term changes with age in the effect of a toric IOL significantly deteriorated due to an ATR shift of corneal astigmatism in the eyes having ATR astigmatism, while it was maintained in eyes having WTR astigmatism, suggesting that ATR astigmatism should be overcorrected.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-021-05406-7.

Comparison of visual and refractive outcomes of 2 trifocal intraocular lenses

PURPOSE

To compare clinical outcomes after cataract surgery and bilateral implantation of 2 diffractive trifocal toric intraocular lenses (IOLs).

SETTING

Hospital da Luz, Lisbon, Portugal.

DESIGN

Double-arm, randomized, prospective case series.

METHODS

A total of 60 patients were randomly allocated to receive bilateral implantation of either the FineVision Pod FT toric IOL (PhysIOL) or the AcrySof IQ PanOptix toric IOL (Alcon). Visual and refractive outcomes, contrast sensitivity, IOL misalignment, and quality of vision outcomes (QoV questionnaire) were evaluated at 3 months postoperatively. Surgically induced astigmatic changes were evaluated by vector analysis.

RESULTS

Each group (FineVision toric and AcrySof IQ PanOptix toric) comprised 30 patients (60 eyes). No significant differences between groups were found regarding uncorrected and corrected distance and near visual outcomes (P ≥ .333). Mean postoperative distance-corrected intermediate visual acuity at 60 cm was 0.04 ± 0.09 logarithm of the minimum angle of resolution (logMAR) and 0.09 ± 0.11 logMAR in the PanOptix and Pod FT group, respectively (P = .032). Mean IOL axis misalignment was 1.59 degrees ± 2.15 degrees (PanOptix group) and 1.89 degrees ± 3.31 degrees (Pod FT group) (P = .821). Mean magnitude of error of astigmatic correction was -0.09 diopters (D) and -0.11 D in the PanOptix group and Pod FT group, respectively (P = .333). Contrast sensitivity, QoV scores for the presence of photic phenomena, and the level of spectacle independence were similar in both groups (P > .05).

CONCLUSIONS

Both trifocal toric IOLs allowed complete patient visual restoration, and good spectacle independence and good visual quality outcomes. The PanOptix IOL provided superior intermediate visual acuity for distances around 60 cm.

Evaluation of preoperative corneal astigmatism using swept-source optical biometry in Chinese cataract surgery candidates with high myopia: a prospective, comparative observational study

Background

High myopia and cataracts are major causes of blindness in East and Southeast Asia. Corneal astigmatism is a major contributor to uncorrected poor vision after cataract surgery in patients with high myopia. The purpose of the present study was to evaluate the demographic characteristics and distribution of preoperative corneal astigmatism in Chinese cataract surgery candidates with high myopia.

Methods

Swept-source optical coherence tomography-based optical biometry was performed preoperatively in consecutive cataract surgery candidates who were classified by axial length (AL) into a high myopia group (defined as AL ≥26.0 mm) and a control group (normal ALs). The demographics, ALs, and keratometry values were recorded.

Results

Among 15,063 cataract surgery candidates (15,063 eyes), 1,921 patients (12.8%, 1,921 eyes) in the high myopia group and 11,880 patients (11,880 eyes) in the control group were enrolled. In the high myopia group, the mean age was 59.8±12.6 (standard deviation) years, which was younger than that in the control group (69.1±11.0 years, P<0.001). In the high myopia group, the mean corneal astigmatism was 1.20±0.83 dioptre (D), which was greater than that in the control group (0.93±0.69 D, P<0.001). In the high myopia group, 82.2% had corneal astigmatism ≥0.50 D, 51.4% ≥1.00 D, 27.4% ≥1.50 D and 14.4% ≥2.00 D, all of which were higher than the respective proportions in the control group (P<0.001 for all). In the high myopia group, 66.8% had moderate to high corneal astigmatism, and 42.8% had “with-the-rule” astigmatism, and both of these proportions were higher than the respective proportions in the control group (P<0.001 for both). In the high myopia group, corneal astigmatism tended to increase with increasing age (r =0.134, P<0.001) after the age of 50, which was consistent with the tendency in the control group.

Conclusions

A significant burden of preoperative corneal astigmatism was observed in Chinese cataract surgery candidates with high myopia. Moderate to high corneal astigmatism was more common in highly myopic eyes than in normal AL eyes.

Evaluation of posterior and total corneal astigmatism with colour-LED topography

PURPOSE

To characterise the posterior and total corneal astigmatism using colour point-source light-emitting diodes (LED) topography.

METHODS

In a prospective case series 400 eyes from 400 patients were evaluated by colour-LED topography. Only eyes with normal topographies were considered. The following parameters were studied: magnitude and distribution of SimK and posterior corneal astigmatism, correlation between SimK and posterior corneal astigmatism, and differences in magnitude and axis between total and anterior corneal astigmatism.

RESULTS

The mean SimK corneal astigmatism was 1.21 ± 0.94 D. The mean posterior corneal astigmatism was 0.37 ± 0.24 D. Posterior astigmatism was vertically oriented in 68% of eyes. Twenty-two percent of eyes showed a posterior corneal astigmatism ≥ 0.50 D. The correlation coefficients between SimK and posterior corneal astigmatism were: r² = 0.066; p = 0.371 in WTR eyes, r² = 0.112; p = 0.173 in ATR eyes and r² = -0.019; p = 0.879 in oblique eyes. A difference between SimK and total corneal astigmatism ≥ 0.50 D was found in 7% of eyes. A difference in axis between SimK and total corneal astigmatism ≥ 10° was found in 24% of eyes.

CONCLUSIONS

The percentage of eyes with posterior corneal astigmatism ≥ 0.50 D and the differences between anterior and total corneal astigmatism were higher than those previously reported in the literature. Therefore, this study supports the consideration of total corneal astigmatism magnitude and axis is mandatory for a precise surgical correction of astigmatism.

Comparison of the clinical efficacy of AcrySof® IQ and TECNIS® toric intraocular lenses: A real-world study

Corneal astigmatism significantly compromises uncorrected visual acuity (UCVA) after phacoemulsification with implantation of traditional spherical or non-spherical monofocal intraocular lens (IOL). Toric IOL provides an effective way to gain favorable postoperative UCVA for the patients with cataracts with corneal astigmatism. There are numerous types of toric IOLs; however AcrySof^® IQ toric IOL (Alcon Laboratories, Inc.) and TECNIS^® toric IOL (Johnson & Johnson Vision; Johnson & Johnson) are most frequently used in our clinical practice. The purpose of the current study was to compare the clinical efficacy of AcrySof IQ with TECNIS toric IOL implantation, and to provide a clinical basis on selecting an appropriate toric IOL before cataract surgery for patients with corneal astigmatism. A total of 30 patients with cataract (44 eyes) with corneal astigmatism [0.82-7.27 diopters (D)], who have undergone phacoemulsification with toric IOL implantation between October 2012 and December 2017, were included in the current retrospective cohort study. Patients were divided into two groups: One group (26 eyes) received the AcrySof IQ toric IOL (AcrySof group) and the other group (18 eyes) received the TECNIS toric IOL (Tecnis group). The indexes of curative effect, such as uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively), refractive outcomes, contrast sensitivity (CS), IOL rotation, and satisfaction, were evaluated. Both toric IOLs significantly improved UDVA and CDVA. Postoperative mean residual astigmatism was similar in the AcrySof group and in the Tecnis group (0.75±0.50 and 0.78±0.90 D; P=0.896). There was no statistically significant between postoperative CS in the AcrySof and Tecnis groups. Rotations of >10˚ were considered to be significant and were identified in three eyes. The mean IOL rotation showed no statistically significant difference (AcrySof group, 0.24±5.54˚; Tecnis group, -0.19±6.28˚; P=0.416). The mean patient satisfaction score was 8.46±1.21 in the AcrySof group and 8.78±1.44 in the Tecnis group (P=0.260). The results of the current study indicated that patients with cataracts with corneal astigmatism undergoing phacoemulsification with AcrySof IQ and TECNIS toric IOL implantation achieved similar clinical efficacy in term of visual outcomes, refraction correction, CS, rotational stability and satisfaction.

How Can We Improve Toric Intraocular Lens Calculation Methods? Current Insights

In this paper, we review current strategies for calculating toric intraocular lenses (IOLs). We discuss the prevalence and clinical relevance of astigmatism and the assessment of toric IOL candidates. We detail recommendations for evaluating astigmatism and current biometry and IOL power calculation techniques. Finally, error sources and results of current toric IOL calculators are discussed.

Refractive outcome of toric intraocular lens calculation in cases of oblique anterior corneal astigmatism

PURPOSE

To establish whether toric intraocular lens (IOL) calculation on the basis of anterior corneal measurements alone, in corneas with oblique anterior astigmatism, will result in a systematic overcorrection or undercorrection of postoperative refractive astigmatism, and to establish whether adjustment of oblique anterior corneal astigmatism to allow for the likely effect of posterior corneal astigmatism is needed in such eyes.

SETTING

The Queen Elizabeth Hospital, Department of Ophthalmology, Adelaide, South Australia.

DESIGN

Retrospective case series.

METHODS

Data were collected from consecutive eyes with oblique anterior corneal astigmatism undergoing cataract surgery or refractive lens exchange. Toric IOL calculations were made using unadjusted anterior corneal astigmatism measurements and an astigmatically neutral technique. By comparison of targeted vs achieved astigmatic correction using vector analysis, the astigmatic power prediction error and angle of error were derived.

RESULTS

In 50 eyes, the mean postoperatively measured refractive astigmatism was 0.42 diopters (D) (SD 0.33 D), the mean targeted refractive astigmatism was 0.15 (SD 0.18), and the vector-derived mean absolute prediction error was 0.23 D (SD 0.21). All 50 eyes (100%) fell at or within ±1.00 D of the target and 45 eyes (90%) at or within ±0.50 D. The geometric mean astigmatism correction index was 0.98, and the mean absolute angle of error was 8.63 degrees (SD 8.55).

CONCLUSIONS

There is no systematic error attributable to posterior corneal astigmatism in toric IOL calculation and no need for adjustment of anteriorly measured corneal keratometric values for toric IOL calculation in eyes with oblique anterior corneal astigmatism. To do so may introduce an error in astigmatic outcome.

Comparison of incidence of repositioning surgery to correct misalignment with three toric intraocular lenses

PURPOSE

To compare the incidence of re-orientating surgery to improve misalignment of three models of acrylic toric intraocular lenses: AcrySof toric intraocular lens (Alcon Laboratories, Inc.), TECNIS toric intraocular lens (Johnson & Johnson Vision, Inc.) and HOYA 355 toric intraocular lens (HOYA).

METHODS

In this retrospective, multicenter case series, medical charts were reviewed for collecting data on realignment surgery of toric intraocular lenses at 10 ophthalmic surgical sites in Japan.

RESULTS

Over all, intraocular lens repositioning surgery was conducted in 89 of 9430 eyes (0.944%) at an average of 10.5 ± 9.7 days after the initial cataract surgery. The incidence was 0.213% (11/5155), 1.797% (62/3451) and 1.942% (16/824) with AcrySof, TECNIS and HOYA toric intraocular lenses, respectively. The incidence was significantly lower with AcrySof than with other two brands of toric intraocular lenses (p < 0.0001). In those eyes which underwent reorientation surgery, the amount of misalignment was 26.4 ± 21.9°, 29.7 ± 15.4° and 28.1 ± 20.7° with AcrySof, TECNIS and HOYA toric intraocular lenses, respectively; there was no significant difference among groups (p = 0.821). The repositioning surgery significantly reduced misalignment in all three groups.

CONCLUSION

The rotational stability was considerably different among toric intraocular lenses of different manufacturers. The incidence of repositioning surgery was significantly lower with AcrySof than with TECNIS and HOYA toric intraocular lenses.

Rotational Stability of Monofocal and Trifocal Intraocular Toric Lenses With Identical Design and Material but Different Surface Treatment

PURPOSE

To compare the rotational stability, total misalignment, and visual and refractive outcomes achieved with a trifocal toric versus a monofocal toric intraocular lens (IOL).

METHODS

In this prospective, interventional case series, eyes of patients consecutively scheduled for cataract surgery who had clinically relevant astigmatism were implanted with a FineVision Pod FT trifocal toric IOL or an Ankoris monofocal toric IOL (both PhysIOL SA, Liège, Belgium). Certain comorbidities, such as pseudoexfoliation syndrome, were allowed. IOL rotation and total misalignment were analyzed 15 minutes, 1 day, 1 week, 6 weeks, 6 months, and 1 year postoperatively.

RESULTS

Seventy-one eyes of 53 patients were assessed: 37 eyes were implanted with the trifocal IOL and 34 eyes with the monofocal IOL. More IOL rotation occurred in the monofocal group compared to the trifocal group (mean 4.23° ± 4.64° vs 2.55° ± 2.62°; P = .043, 12 months). Mean total misalignment was higher in the monofocal group (6.67° ± 6.59° at 12 months vs 3.79° ± 3.59° in the trifocal group) (P = .017). Postoperatively, more eyes achieved a refractive cylinder of 0.50 diopters or below in the trifocal group (65% at 12 months) than in the monofocal group, even in the monofocal subgroup analysis that excluded keratoconic eyes (42% at 12 months; P = .009).

CONCLUSIONS

The monofocal and trifocal toric IOLs both appear to effectively reduce refractive astigmatism and provide good visual acuity in astigmatic patients having cataract surgery. The trifocal toric IOL offers better rotational stability than the monofocal IOL, probably due to the higher frictional coefficient of its surface. [J Refract Surg. 2018;34(2):84-91.].

Prediction of surgically induced astigmatism in manual and femtosecond laser-assisted clear corneal incisions

Purpose:

To assess the surgically induced astigmatism with femtosecond laser-assisted and manual temporal clear corneal incisions and to evaluate the performance of a model for prediction of the surgically induced astigmatism based on the preoperative corneal astigmatism.

Methods:

Clinical data of 104 right eyes and 104 left eyes undergoing cataract surgery, 52 with manual incisions and 52 with femtosecond laser-assisted incisions in each eye group, were extracted and revised retrospectively. In all cases, manual incisions were 2.2 mm width and femtosecond incisions were 2.5 mm width, both at temporal location. A predictive model of the surgically induced astigmatism was obtained by means of simple linear regression analyses.

Results:

Mean surgically induced astigmatisms for right eyes were 0.14D@65° (manual) and 0.24D@92° (femtosecond) (p > 0.05) and for left eyes, 0.15D@101° (manual) and 0.19D@104° (femtosecond) (p > 0.05). The orthogonal components of the surgically induced astigmatism (XSIA, YSIA) were significantly correlated (p < 0.05) with the preoperative orthogonal components of corneal astigmatism (Xpreop, Ypreop) (r = −0.29 for X and r = −0.1 for Y). The preoperative astigmatism explained 8% of the variability of the XSIA and 3% of the variability of YSIA. The postoperative corneal astigmatism prediction was not improved by the surgically induced astigmatism obtained from the model in comparison with the simple vector subtraction of the mean surgically induced astigmatism.

Conclusion:

Temporal incisions induce similar astigmatism either for manual or for femtosecond procedures. This can be clinically negligible for being considered for toric intraocular lens calculation due to the great standard deviation in comparison with the mean. The usefulness of the prediction model should be confirmed in patients with high preoperative corneal astigmatism.

Tomographic Analysis of Anterior and Posterior and Total Corneal Refractive Power Changes After Femtosecond Laser-Assisted Keratotomy

PURPOSE

To analyze the effect of penetrating femtosecond laser-assisted keratotomy (pFLAK) during laser lens surgery on anterior and posterior corneal astigmatism and total corneal refractive power (TCRP) astigmatism (CA_ant, CA_post, CA_TCRP) measured with Scheimpflug tomography.

DESIGN

Prospective, interventional case series.

METHODS

This institutional study included 27 eyes of 23 patients (aged 65 ± 8 years) with low-to-moderate CA_TCRP determined with Scheimpflug tomography (Pentacam HR; Oculus, Wetzlar, Germany) after penetrating femtosecond laser-assisted keratotomy (pFLAK) and laser lens surgery. The CA_ant, CA_post, and CA_TCRP were determined before and 1 and 3 months after surgery. Vector analysis according to the Alpins method was used to calculate surgically induced astigmatism (SIA).

RESULTS

The mean preoperative CA_ant (0.97 ± 0.30 diopter [D]) was significantly reduced to 0.63 ± 0.34 D (P < .001). SIA_ant was 0.71 ± 0.37 D. The CA_post showed no significant change, from preoperative 0.26 ± 0.12 D to 0.26 ± 0.10 D postoperatively (P = .625). In line with this finding, SIA_post was low (0.12 ± 0.07 D). The CA_TCRP showed similar results as CA_ant.

CONCLUSION

pFLAKs planned according to Scheimpflug-based CA_TCRP result in a significant reduction of the CA_ant and CA_TCRP, but do not affect the posterior corneal curvature significantly, as measured by Scheimpflug tomography. Further research is required to develop a new valid nomogram for laser-assisted lens surgery.