Intraocular lens power calculation using standard formulas and ray tracing after DMEK in patients with Fuchs endothelial dystrophy

Accuracy of formulas for intraocular lens power for eyes undergoing descemet stripping automated endothelial keratoplasty and cataract surgery

BACKGROUND

To compare accuracy in intraocular lens (IOL) power calculation in eyes undergoing combined cataract and Descemet stripping and automated endothelial keratoplasty (C-DSAEK) surgery of the following formulas: Barrett Universal II, EVO, Haigis, Hoffer Q, Holladay 2, Kane and SRK/T.

METHODS

72 eyes from 72 patients (38 males, (53%)) with a mean age 68.08 ± 8.69 years (from 44 to 88 years old) underwent combined C-DSAEK were included. The IOL powers to implant were calculated with Barrett Universal II formula targeting -1 D refraction. Preoperative and postoperative data were used to obtain the median of absolute prediction errors (MAE) targeting emmetropia with every tested formula.

RESULTS

Means of MAE calculated were +1.45 D for Barrett Universal II, +1.37 D for EVO, +1.48 D for Haigis, +1.38 D for Hoffer Q, +1.37 D for Holladay 2, +1.39 D for Kane and +1.31 D for SRK/T. SRK/T MAE showed major significant (p < 0.01) differences compared to the other formulas.

DISCUSSION

Even if tested formulas are not able to accurately target emmetropia, SRK/T seems to be able to provide closer results in eyes undergoing C-DSAEK.

Refractive outcomes after DMEK: meta-analysis

In this meta-analysis and systematic literature review of refractive outcomes after Descemet membrane endothelial keratoplasty (DMEK), the extent of the refractive shift and an overview of reasons for refractive shift after DMEK are provided. The PubMed library was screened for articles containing the terms "Descemet membrane endothelial keratoplasty," "DMEK," "Descemet membrane endothelial keratoplasty combined with cataract surgery," "triple-DMEK" combined with "refractive outcomes," "refractive shift," and "hyperopic shift." The refractive outcomes after DMEK were analyzed and compared using a fixed and random effects model. The overall mean change of the spherical equivalent outcome when compared with the preoperative value in cases of DMEK or when compared with the preoperative target refraction in cases of DMEK combined with cataract surgery was +0.43 diopters (D) (95% CI, 0.31-0.55). When DMEK is combined with cataract surgery, a target refraction of -0.5 D is recommended to achieve emmetropia. Changes in the posterior corneal curvature are identified as the main cause of the refractive hyperopic shift.

Descemet Membrane Endothelial Keratoplasty-Induced Refractive Shift and Descemet Membrane Endothelial Keratoplasty-Induced Intraocular Lens Calculation Error

PURPOSE

The aim of this study was to determine the mechanisms leading to the refractive shift and intraocular lens calculation error induced by Descemet membrane endothelial keratoplasty (DMEK), using ocular biometry and corneal elevation tomography data.

METHODS

This is a retrospective, monocentric cohort study. Eyes which underwent uncomplicated DMEK surgery with available pre-DMEK and post-DMEK Scheimpflug rotating camera data (Pentacam, Oculus, Wetzlar, Germany) were considered for inclusion with an age-matched control group of healthy corneas. Cataract surgery data were collected for triple-DMEK cases. DMEK-induced refractive shift (DIRS) and intraocular lens calculation error (DICE) were calculated. Pearson r correlation coefficient was calculated between each corneal parameter variation and both DIRS and DICE.

RESULTS

DIRS was calculable for 49 eyes from 43 patients. It was 30.61% neutral, 53.06% hyperopic (36.73% > 1D), and 16.32% myopic (6.12% > 1 D). DICE was calculable for 30 eyes of 26 patients: It was 46.67% neutral, 40.00% hyperopic (10.00% > 1D), and 13.33% myopic (3.33% > 1D). DIRS and DICE were mainly associated with variations in PRC/ARC ratio, anterior average radii of curvature (ARC), posterior average radii of curvature (PRC), and posterior Q.

CONCLUSIONS

Our results suggest that ARC variations, PRC/ARC ratio variations, PRC variations, and posterior Q variations are the most influential parameters for both DIRS and DICE. We suggest that a distinction between those different phenomenons, both currently described as "hyperopic shift" in the literature, should be made by researchers and clinicians.

Cataract surgery and intraocular lens placement in patients with Fuchs corneal dystrophy: a review of the current literature

PURPOSE OF REVIEW

Late-onset Fuchs endothelial corneal dystrophy (FECD) is seen in approximately 4% of individuals over the age of 40. With the growing population of adults over the age of 65, ophthalmologists need to be aware of the preoperative, perioperative, and postoperative considerations involved in cataract surgery in Fuchs patients.

RECENT FINDINGS

Management of cataract patients with FECD requires preoperative assessment of endothelial cell size, density, and morphology. Considerations for perioperative endothelial cell loss include patients with hyperopia and shallow anterior chambers, phacoemulsification technique, transfer of ultrasonic energy to the cornea, corneal-protective perioperative agents, as well as thermal and mechanical damage.

SUMMARY

Ophthalmologists performing cataract surgery on patients with FECD must carefully consider the risks of endothelial cell loss during surgery and minimize the risk of corneal decompensation after surgery. Preoperative management should evaluate the severity of the FECD as well as individual factors such as cataract density, the health and thickness of the cornea, and the anterior chamber depth. Perioperative techniques, adjustments to biometry calculations, and intraocular lens (IOL) selection may help optimize visual outcomes and recovery time.

Refractive outcome and tomographic changes after Descemet membrane endothelial keratoplasty in pseudophakic eyes with Fuchs' endothelial dystrophy

Purpose

To analyze refractive and topographic changes secondary to Descemet membrane endothelial keratoplasty (DMEK) in pseudophakic eyes with Fuchs’ endothelial dystrophy (FED).

Methods

Eighty-seven pseudophakic eyes of 74 patients who underwent subsequent DMEK surgery for corneal endothelial decompensation and associated visual impairment were included. Median post-operative follow-up time was 12 months (range: 3–26 months). Main outcome measures were pre- and post-operative manifest refraction, anterior and posterior corneal astigmatism, simulated keratometry (CA_SimK) and Q value obtained by Scheimpflug imaging. Secondary outcome measures included corrected distance visual acuity (CDVA), central corneal densitometry, central corneal thickness, corneal volume (CV), anterior chamber volume (ACV) and anterior chamber depth (ACD).

Results

After DMEK surgery, mean pre-operative spherical equivalent (± SD) changed from + 0.04 ± 1.73 D to + 0.37 ± 1.30 D post-operatively (p = 0.06). CDVA, proportion of emmetropic eyes, ACV and ACD increased significantly during follow-up. There was also a significant decrease in posterior corneal astigmatism, central corneal densitometry, central corneal thickness and corneal volume over time (p = 0.001). Only anterior corneal astigmatism and simulated keratometry (CA_SimK) remained fairly stable after DMEK.

Conclusion

Despite tendencies toward a hyperopic shift, changes in SE were not significant and refraction remained overall stable in pseudophakic patients undergoing DMEK for FED. Analysis of corneal parameters by Scheimpflug imaging mainly revealed changes in posterior corneal astigmatism pointing out the relevance of posterior corneal profile changes during edema resolution after DMEK.

[Change of corneal radii after Descemet membrane endothelial keratoplasty measured by optical coherence tomography and Scheimpflug tomography]

BACKGROUND

The aim of the study was to compare the measurement of corneal radii using Scheimpflug tomography (Pentacam®, Oculus, Wetzlar, Germany) and optical coherence tomography (OCT, Optovue® XR-Avanti, Fremont, CA, USA) in eyes of patients with Fuchs' endothelial dystrophy (FED) before and after Descemet membrane endothelial keratoplasty (DMEK).

MATERIAL AND METHODS

In a retrospective analysis 35 eyes with (FED) that underwent DMEK were included. Pentacam® and Optovue® corneal measurements were performed preoperatively and at least 3 months postoperatively. The four primary objectives were the radii of the anterior and posterior corneal surfaces, the corneal thickness and the posterior to anterior corneal curvature radii ratio. The change in the primary targets after DMEK was analyzed and the measurement results of both methods were compared. A Bland-Altman plot was created to graphically illustrate the correlation between the two measuring methods.

RESULTS

A significant decrease in corneal thickness was observed after DMEK with both methods. The radii of the anterior corneal surface, measured with Scheimpflug as well as with OCT showed no significant changes after surgery, while the radii of the posterior corneal surface significantly decreased (Pentacam®: preoperative = 7.24 mm ± 0.99 mm; postoperative = 6.38 mm ± 0.40 mm, P < 0.001; Optovue®: preoperative = 7.63 mm ± 1.43 mm; postoperative = 6.57 mm ± 0.43 mm, P < 0.001). The Bland-Altman plots of all primary objectives showed a better agreement postoperatively compared to the preoperative measurements.

CONCLUSION

Both Scheimpflug and OCT showed a significant decrease in the radius of the posterior corneal surface after DMEK. The postoperative measurements showed a higher agreement between the devices than those performed preoperatively.

Characteristics of preoperative and postoperative astigmatism in patients having Descemet membrane endothelial keratoplasty

PURPOSE

To evaluate the characteristics of preoperative and postoperative astigmatism in patients having Descemet membrane endothelial keratoplasty (DMEK).

SETTING

Department of Ophthalmology, Goethe University, Frankfurt, Germany.

DESIGN

Retrospective case series.

METHODS

Measurements were obtained using a Scheimpflug camera (Pentacam AXL) preoperatively and 3 months and 12 months postoperatively. Values of front and back astigmatism and total astigmatism in the central 4.0 mm diameter zone (TCA4) were analyzed.

RESULTS

Fifty-three eyes of 45 patients were included. The prevalence of TCA4 above 1.0 diopter (D) was considerably higher (79%) and with-the-rule astigmatism was less frequent in this cohort of European patients with Fuchs endothelial dystrophy (mean age 65 years) than that reported in a meta-analysis of healthy European eyes. The TCA4 values correlated with anterior astigmatism preoperatively and postoperatively (P < .001) and with posterior astigmatism at the 1-year follow-up (P < .01). Although, no correlation was found between the preoperative and 1-year results for anterior astigmatism (P = .12), posterior astigmatism (P = .35), or total corneal astigmatism (P = .47), the difference in vector analysis between the two measurements was only 0.01 at 109 degrees, 0.03 at 98 degrees, and 0.02 at 157 degrees, respectively. However, the greater the difference between the preoperative TCA3 and preoperative TCA5 values, the greater the decrease in corneal astigmatism (P < .001).

CONCLUSIONS

The percentage of eyes with corneal astigmatism above 1.0 D was higher preoperatively and postoperatively in patients with Fuchs endothelial dystrophy than in a healthy population. Predicting postoperative astigmatism based on preoperative results is not possible; however, in eyes with a high difference between TCA3 and TCA5, a reduction in corneal astigmatism after DMEK is likely.

Refractive Outcomes of Descemet Membrane Endothelial Keratoplasty Combined With Cataract Surgery in Fuchs Endothelial Dystrophy

PURPOSE

To evaluate the refractive outcomes of Descemet membrane endothelial keratoplasty combined with cataract surgery (DMEK triple) in patients with Fuchs endothelial dystrophy.

METHODS

A retrospective analysis of 68 eyes of 68 patients with Fuchs endothelial dystrophy who underwent DMEK triple between 2014 and 2018.

RESULTS

The mean age of patients was 66.5 ± 8.6 years, and 65% (44 of 68) were female. Mean target refraction was -0.69 diopters (D) (interquartile range: -0.80 to -0.50 D). At 6 months, 47% (32 of 68) and 63% (43 of 68) of eyes were within ±0.50 and ±1.00 D of target refraction, respectively. Among eyes greater than 0.50 D from target, 78% (28 of 36) were hyperopic surprises. Mean spherical equivalent at 6 months was -0.14 ± 1.26 D, representing a mean hyperopic shift of 0.55 D from target. Preoperative pachymetry was higher in eyes with greater than 0.50 D of hyperopic surprise (648 ± 60 vs 613 ± 49 µm, P = .04). Refractive shift was greater in eyes with a preoperative central corneal thickness of 640 µm or greater versus eyes with a central corneal thickness of less than 640 µm (+1.20 ± 0.92 vs +0.40 ± 0.99 D, P = .02). None of the eyes with a preoperative central corneal thickness of 640 µm or greater shifted myopically compared to target (range: -0.09 to +2.89 D).

CONCLUSIONS

A mean hyperopic shift of 0.55 D from target refraction occurred after DMEK triple, and 47% of eyes were within 0.50 D of target refraction at 6 months postoperatively. Thicker corneas preoperatively had greater hyperopic shift. A greater myopic target refraction may be warranted in eyes with a preoperative central corneal thickness of 640 µm or greater. [J Refract Surg. 2020;36(10):661-666.].

Using the posterior to anterior corneal curvature radii ratio to minimize the risk of a postoperative hyperopic shift after Descemet membrane endothelial keratoplasty

PURPOSE

To evaluate different corneal parameters in identifying patients at risk of a hyperopic shift after (DMEK).

METHODS

This retrospective study included 92 eyes of patients with FECD after DMEK surgery. Pachymetry parameters, various tomographic parameters and densitometry values before and after DMEK were determined using a rotating Scheimpflug system (Pentacam HR, Oculus). For assessing the posterior to anterior corneal curvature relationship, we calculated the R_PA (posterior to anterior corneal curvature radii ratio).

RESULTS

The average keratometry reading of the posterior corneal surface (Km^B) increased and the total corneal refractive power (TCRP) decreased significantly after surgery (P < .001). There was a significant difference between the preoperative and postoperative R_PA (P < .001) and the posterior Q value (P < .001). The strongest correlation was found between the change in the Km^B and the preoperative R_PA (Spearman's correlation coefficient = 0.872, P < .001). In the receiver operating characteristic (ROC) analysis, the highest AUC values (for ∆Km^B) among the different preoperative parameters tested were obtained for R_PA and posterior Q value (Asph. Q^B) with AUROC (area under the ROC) values of 0.95 and 0.89, respectively.

CONCLUSIONS

The Q value and the R_PA showed the highest correlation with the change in corneal refractive power and the greatest AUC. These parameters could be used as surrogate markers to identify eyes that might be at risk of a greater postoperative hyperopic shift, which would allow more accurate setting of refractive goals.

Corneal Tomography Changes and Refractive Outcomes After Descemet Stripping Without Endothelial Keratoplasty

PURPOSE

To investigate corneal tomography changes and refractive outcomes after Descemetorhexis without endothelial keratoplasty (DWEK).

METHODS

Retrospective chart review of 25 eyes from 16 patients with Fuchs corneal endothelial dystrophy that underwent successful DWEK combined with cataract surgery.

RESULTS

There was no significant change in anterior corneal curvature on tomography maps. However, all tomography maps demonstrated an increase in central posterior float and all but one demonstrated a decrease in pachymetry after DWEK. Only 7 of 25 eyes had increased irregular astigmatism on tomography after DWEK, of which 57% had preexisting irregular astigmatism before the procedure. The mean difference between the targeted and outcome refraction was +0.65 diopters (D) at the time of corneal clearance, but this improved to +0.38 D 1 month after corneal clearance. Postoperative refraction was within 1 D of target refraction for 92% of cases (23 eyes) but within 0.5 D of target refraction for only 48% of cases (12 eyes). The differences between expected and actual refractive outcomes were correlated with change in posterior corneal curvature and pachymetry.

CONCLUSIONS

DWEK induces an increased central posterior float localized to the site of Descemet membrane stripping, confirming the need for centralized stripping. Irregular astigmatism can occur after DWEK but is typically minimal and occurs more commonly in the setting of preoperative irregular astigmatism. DWEK induces about a 0.5 D hyperopic shift, which should be considered when determining intraocular lens power with simultaneous surgery.

Avoiding Hyperopic Surprises After Descemet Membrane Endothelial Keratoplasty in Fuchs Dystrophy Eyes by Assessing Corneal Shape

PURPOSE

It is unclear which patients unexpectedly have a hyperopic refractive outcome after combined Descemet membrane endothelial keratoplasty and cataract surgery (triple DMEK). We assessed how corneal shape predicts hyperopia after triple DMEK.

DESIGN

Retrospective cohort study.

METHODS

Patients with Fuchs endothelial corneal dystrophy (FECD) with Scheimpflug examinations before uncomplicated triple DMEK at a tertiary referral center were included. The arithmetic error was calculated (stable postoperative refraction minus predicted refraction). Using multinomial logistic regression, risk ratios of > +0.5 diopter (D) hyperopic and > 0.5 D myopic arithmetic errors were calculated.

RESULTS

In 112 eyes, the median predicted refraction was -0.43 D (interquartile range [IQR], -0.47 to -0.17) with an achieved refraction of -0.63 to 0.56 (IQR). The arithmetic error was 0.34 D (IQR, -0.22 to 0.81). A hyperopic arithmetic error was present in 46% of eyes. FECD eyes with an oblate posterior cornea (Q value >0) had a 3.0 times higher risk of hyperopic shift after triple DMEK (95% confidence interval [CI], 1.3-7.0; P = .011), compared to spherical or prolate corneas (Q value ≤ 0). In eyes with posterior Q > 0, the mean prediction error was +0.50 D higher than in eyes with negative Q values (95% CI, 0.19-0.82; P = .002), independent of corneal thickness.

CONCLUSIONS

Hyperopic surprises after triple DMEK particularly occur in corneas that are flatter centrally than the periphery because of edematous changes (oblate posterior profile). Eyes with a positive Q value on Scheimpflug imaging should be considered for additional power at the intraocular lens level.

Can we predict the refractive outcome after triple Descemet membrane endothelial keratoplasty?

Purpose:

To analyze and correlate corneal parameters with refractive shift after Descemet membrane endothelial keratoplasty combined with cataract surgery (triple Descemet membrane endothelial keratoplasty).

Methods:

This single-center retrospective observational case series included 152 eyes of 152 consecutive patients undergoing triple Descemet membrane endothelial keratoplasty in the first eye for Fuchs endothelial corneal dystrophy. Patients were examined preoperatively, as well as at 3, 6, and 12 months after surgery. The main outcome measures were: refractive shift (predicted refractive outcome based on intraocular lens calculation compared to actual postoperative refractive outcome), central corneal thickness, corneal volume, anterior and posterior corneal curvature, and corneal densitometry. These parameters were analyzed and correlated with the refractive shift after surgery.

Results:

After 3 months from surgery, a mean refractive shift of +1.12 ± 1.10 D was observed and remained stable until the last follow-up at 12 months (+1.24 ± 1.07 D). Correlation analysis showed a weak but significant positive correlation between refractive shift and preoperative posterior curvature (rho = 0.314; p = 0.002) or preoperative posterior densitometry (rho = 0.227; p = 0.008). No correlation was found between refractive shift and preoperative central corneal thickness, corneal volume, anterior curvature, or anterior/mid-cornea densitometry.

Conclusion:

Changes of the posterior cornea may have an influence on the refractive shift. Patients with flatter posterior corneal curvature or higher posterior corneal density seem to exhibit a higher hyperopic shift. The weak correlations indicate a poor predictive value of any preoperative parameter used in our study.