Correcting astigmatism with toric intraocular lenses: Effect of posterior corneal astigmatism
Citations
147 citations
130 citations
Cites result from "Correcting astigmatism with toric i..."
...Our data show a partial discrepancy with those of a similar study comparing toric IOL outcomes as predicted by KA and TCA.(21) The authors, in fact, found that TCA improved astigmatism prediction only in ATR eyes....
[...]
...Moreover, the repeatability of posterior corneal curvature by Scheimpflug cameras has been shown to be lower than that for anterior corneal curvature.20 Our data show a partial discrepancy with those of a similar study comparing toric IOL outcomes as predicted by KA and TCA.21 The authors, in fact, found that TCA improved astigmatism prediction only in ATR eyes....
[...]
96 citations
Cites background from "Correcting astigmatism with toric i..."
...Using the recommended 5 scans, this device provides keratometry (K) readings based on 640 reference points.6 Similar to most standard keratometry and topography devices, corneal power is estimated according to anterior corneal curvature measurements with a keratometric index of 1.3375.7 http://dx.doi.org/10.1016/j.jcrs.2015.11.036 217 0886-3350 Recent studies have suggested that the posterior corneal surface also contributes to total corneal astigmatism.7–13 Koch et al.9 proposed that the effect of the posterior cornea astigmatism power in toric IOL selection should be taken into account, and they developed the Baylor toric nomogram as a solution....
[...]
...4 diopter (D).(9) However, the role of the posterior cornea in determining the IOL axis alignment was not addressed....
[...]
...The following methods of calculating preoperative corneal astigmatism and toric IOLs were compared: (1) anterior corneal measurements with the OLCR device, (2) application of the Baylor toric nomogram for the adjustment of posterior astigmatism power as described by Koch et al.,9 (3) integration of posterior corneal surface astigmatism measured by the Scheimpflug camera with the anterior corneal astigmatism measured by the OLCR device using vector summation (vector analysis) as described byHolladay et al.,15,16 (4) Scheimpflug camera–derived true net power calculated by the device using the radii of the anterior and posterior corneal curvatures, and (5) total corneal refractive power calculated using ray tracing by the Scheimpflug camera....
[...]
...Koch et al.(9) proposed that the effect of the posterior cornea astigmatism power in toric IOL selection should be taken into account, and they developed the Baylor toric nomogram as a solution....
[...]
...Koch et al.7 reported that anterior corneal measurements underestimated total corneal astigmatism by a mean vector of 0.22 D. Savini and Næser12 recently found a reduction in the error of refractive astigmatism ranging from 0.25 D (ATR) to 0.46 D (WTR) when total corneal astigmatism was used instead of anterior keratometric astigmatism....
[...]
95 citations
Cites background or methods or result from "Correcting astigmatism with toric i..."
...Intraocular lens tilt, IOL rotational misalignment,(6) and unexpected surgically induced astigmatism (SIA)(2,7) all contribute to prediction errors; however, correcting for these factors does not always explain the postoperative astigmatic outcome.(4,8) Accurate correction of astigmatism requires accurate measurements....
[...]
...Methods of Calculation The online toric calculator by Alcon and the Holladay toric calculator were evaluated without and with the Baylor toric IOL nomogram adjustment.(8) The online Barrett toric calculator was evaluated without adjustment....
[...]
...The Baylor nomogram for the adjustment of toric IOL power to account for posterior corneal astigmatism is based on regression analysis.(8) The predicted net corneal astigmatism assessment for the Baylor nomogram was calculated using the published regression equations by subtracting (0....
[...]
...The predicted residual astigmatism at the corneal planewas calculated by the sum of the assumed toric IOL cylinder power at the corneal plane and the measured corneal astigmatism taken by each device with or without adjustments for the Baylor nomogram.(8) The error in the predicted residual astigmatism was calculated by subtracting the predicted residual astigmatism at the corneal plane from the postoperative subjective refraction at the corneal plane....
[...]
...These results correlate well with findings by Koch et al.(8) for WTR astigmatism and partially for ATR astigmatism....
[...]
91 citations
References
431 citations
365 citations
293 citations
246 citations
"Correcting astigmatism with toric i..." refers methods in this paper
...Prospectively, patients who were willing to participate in this study and met the following inclusion criteria were enrolled from July 2011 to September 2012: (1) good quality scans with all 5 devices, (2) no previous ocular trauma or surgery, (3) no corneal or other ocular disease, (4) no contact lens wear within 2 weeks before the corneal measurements, and (5) Acrysof toric IOL (models SN6AT3 to SN6AT8, Alcon Laboratories, Inc....
[...]