Effect of Anterior Corneal Higher-Order Aberration Ablation Depth on Primary Topography-Guided LASIK Outcomes

Retrospective Study Comparing Topography-Guided and Wavefront-Optimized LASIK Procedures in a Single Center

Purpose

To compare visual outcomes of eyes that had laser refractive surgery with the Contoura Phorcides treatment plan and eyes that had laser refractive surgery with the wavefront-optimized treatment plan using the same laser.

Methods

Retrospective chart review of clinical outcomes of eyes that had either Contoura with Phorcides (CP) or wavefront-optimized (WFO) corneal refractive procedures using the Wavelight EX500 (Alcon Vision, LLC). Data were collected and compared for uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, change in postoperative UDVA compared to preoperative CDVA, and change in postoperative CDVA compared to preoperative CDVA.

Results

Total eyes included were 348, with 227 in the CP Group and 121 in the WFO Group. Post-operatively, there was a significantly higher percentage of eyes in the CP Group that were 20/16 or better compared to the WFO Group (57%, 129 eyes, and 17%, 21 eyes, respectively; p < 0.001). The percentage of eyes that gained 1 or more Snellen lines of UDVA compared to preoperative CDVA was higher in the CP Group (47%; 107 eyes) compared to the WFO Group (12%; 14 eyes), which was statistically significant (p < 0.001). Differences in refraction were statistically significant.

Conclusion

Topography-guided and wavefront-optimized treatment profiles both provided excellent refractive results. A higher percentage of eyes that were treated using Contoura with Phorcides achieved 20/16 or better unaided distance vision compared to eyes receiving a wavefront-optimized treatment plan.

Differences in ocular high order aberrations before and after small incision lenticule extraction for correction of myopia: a systematic review and meta-analysis

Objective

To examine the causes and factors that lead to high order aberration (HOA) during the treatment of myopia using small incision lenticule extraction (SMILE), as well as the differences between SMILE and other corneal refractive surgeries through a systematic review and meta-analysis.

Methods

A systematic search was conducted from January 2015 to February 2023 in Pubmed, Embase, Web of Science, and Google Scholar databases to gather relevant studies on SMILE and HOA. Studies meeting specific criteria were chosen, and clinical data was retrieved for analysis.

Results

This meta-analysis resulted in the inclusion of 19 studies involving 1,503 eyes. Pooled results showed significant induction of total HOA (tHOA, d = -0.21, p < 0.001), spherical aberration (SA, d = -0.11, p < 0.001) and coma aberration (CA, d = -0.18, p < 0.001) after SMILE compared to pre-SMILE, while no significant change in trefoil aberration (TA) was observed (d = -0.00, p = 0.91). There was a significantly lower induction of tHOA after SMILE compared to femtosecond laser-assisted in situ keratomileusis (FS-LASIK, d = 0.04, p < 0.001), and no significant difference was observed compared to wavefront aberration-guided (WFG) refractive surgery (d = 0.00, p = 0.75). There was also a significant association between different levels of myopia and astigmatism, duration of follow-up, lenticule thickness, and preoperative central corneal thickness (CCT) on the induction of tHOA after SMILE (p < 0.05), while the higher preoperative myopia group (sphere > -5D), lower preoperative astigmatism group (cylinder ≤ -1D), larger lenticule thickness group (lenticule thickness > 100 μm), shorter follow-up group (follow-up 1 month postoperatively) and the thicker CCT group (CCT > 550 μm) brought a significant induction of tHOA compared to the opposite comparison group (p < 0.001).

Conclusion

While SMILE can induce HOA significantly, it induces less HOA than FS-LASIK. Postoperative HOA following SMILE can be affected by factors such as myopia, astigmatism, lenticule thickness, CCT, and duration of follow-up. Future research should continue to explore techniques to decrease the induction of HOA by using this methodology.

Systematic review registration

https://www.crd.york.ac.uk/prospero/.

Characterization of postoperative LASIK ectasia features on higher-order aberration excimer ablation maps

BACKGROUND

To characterize anterior corneal higher-order aberration (HOA) excimer ablation map patterns in postoperative LASIK ectasia (POE) and to examine correlations between newly identified corneal HOA ablation map features of POE and known topographic indices.

METHODS

Prospective multicenter non-interventional descriptive study. A total of 28 eyes from 22 POE patients were enrolled. The postoperative HOA ablation map was derived from Topolyzer Vario corneal imaging at the time of POE diagnosis. Features that recurred were identified and then analyzed. Correlations to Orbscan indices were studied.

RESULTS

An arrangement of two elliptical paracentral ablation islands, deep inferior and shallow superior, in direct mirror-like opposition to each other, were identified on all HOA maps. The paracentral islands were accompanied by peripheral ablation crescents. The deep paracentral inferior island 'hot spot' coincided with the topographical apical POE cone and was highly reproducible in angular position (249.3 ± 17.3°). There was significant variation in ablation depth (shallow superior island: 11.5 ± 6.9 μm and deep inferior island: 32.5 ± 18.8 μm). The superior crescents had high variability in depth (34.8 ± 18.9 μm). Strong correlations were found between the corneal irregularity index and the ablation depth difference between the deep and shallow paracentral islands (R = 0.96; P < 0.0001).

CONCLUSION

The corneal HOA excimer ablation map revealed a recurring, distinct, easily recognizable pattern in POE eyes. Validated Orbscan POE indices and HOA ablation map islands showed a strong correlation. It is possible to extract useful information from the corneal HOA ablation map, potentially making it suitable for diagnosing and monitoring POE although more studies are needed.

Topography-Guided LASIK: A Prospective Study Evaluating Patient-Reported Outcomes

Purpose

To evaluate patient-reported outcomes with a validated patient questionnaire following topography-guided LASIK (TG-LASIK).

Methods

Patients undergoing TG-LASIK using Phorcides analytic software were prospectively enrolled to receive an adapted Patient-Reported Outcomes with LASIK Symptoms and Satisfaction (PROWL) questionnaire before and 26-weeks after treatment. The main study outcome was the change in the Global Vision Satisfaction Index from the PROWL questionnaire.

Results

Forty-six patients underwent treatment and completed the modified PROWL questionnaire before and 26-weeks after TG-LASIK. The Global Vision Satisfaction Index from the modified PROWL questionnaire improved from 4.07 (3.87-4.26) to 5.00 (4.81-5.19) after the TG-LASIK treatment (p < 0.0001). The study population's binocular uncorrected distance visual acuity was 20/16, 20/12.5, and 20/10 or better in 100%, 87.0%, and 15.2% at 26 weeks post TG-LASIK, respectively.

Conclusion

Patient satisfaction as assessed with the modified PROWL questionnaire is very high after undergoing TG-LASIK using Phorcides analytic software. Patient-reported outcomes add another dimension when assessing treatment efficacy beyond change in visual acuity and corneal architecture, and specialists may consider incorporating such assessments into the consenting process and patient education at large.

Topography-guided excimer laser ablation

PURPOSE OF REVIEW

Currently, the most commonly performed corneal refractive surgery is laser-assisted in-situ keratomileusis (LASIK). Customized forms of LASIK have been developed, which have allowed for improved outcomes and the enhanced correction of higher order aberrations (HOAs). This review discusses one form of custom LASIK, topography-guided LASIK, including factors involved in preoperative planning, and advantages and disadvantages compared with other forms of keratorefractive surgery.

RECENT FINDINGS

Various treatment-planning approaches addressing discrepancies between the refractive and topographic astigmatic magnitude and axis have been used successfully, although there is debate regarding a superior method in the literature.

SUMMARY

There are many forms of custom LASIK, which provide excellent outcomes. Topography-guided LASIK may be of particular use in highly aberrated corneas and may also provide outstanding outcomes in healthy eyes given its emphasis on treating the primary refractive surface of the eye.

Corneal higher order aberrations by Sirius topography and their relation to different refractive errors

PURPOSE

To compare the root mean square (RMS) of anterior corneal higher-order aberrations (HOAs) in ametropic and emmetropic eyes.

METHODS

This retrospective observational study was conducted at the Department of Ophthalmology, Tishreen University Hospital, Latakia, Syria. Study eyes were divided into four groups based on refractive error: mild-to-moderate myopia, hypermetropia, myopic astigmatism, and emmetropic eyes as controls. The following anterior corneal HOAs were evaluated using the Scheimpflug-Placido Sirius (CSO, Italy) tomographer over 6 mm pupil: Root mean square (RMS) total corneal HOAs, RMS trefoil, RMS coma and RMS spherical aberrations.

RESULTS

RMS values of total HOAs, trefoil and coma showed statistically significant differences in all four groups (P < 0.05, all). HOAs were noted to be lowest in the control group (0.18 ± 0.09, 011 ± 0.08 and 0.09 ± 0.08 μm, respectively) and highest in the myopic astigmatism group (0.31 ± 0.16, 0.15 ± 0.12, 0.17 ± 0.14 μm, respectively). RMS spherical aberration was lowest in the astigmatism group (0.00 ± 0.16 μm) with a statistically significant difference from that in the control group (0.05 ± 0.07 μm, P = 0.049).

CONCLUSION

The mean RMS values of total HOAs, trefoil and coma were highest in the astigmatism group and lowest in the control group. However, spherical aberration was minimal in the astigmatism group. A better understanding and targeted treatment of higher-order aberrations in ametropic human eyes, and in particular eyes with astigmatism, may enhance visual quality and performance in the treatment of refractive errors. Recognising atypical HOAs may also assist in the early detection of pathological conditions such as keratoconus.

Does Adjunctive Under-flap CXL Reduce Regression for Hyperopic LASIK?

PURPOSE

To investigate whether adding accelerated under-flap corneal cross-linking to hyperopic laser in situ keratomileusis (LASIK-ufCXL) affects postoperative stability and regression, visual and refractive outcomes, and subjective quality of vision.

METHODS

This prospective comparative contralateral eye study included 51 patients with hyperopia (102 eyes) who received LASIK-ufCXL in the eye with highest defocus equivalent (DEQ) or randomized when DEQ equal, with the contralateral control eye receiving LASIK alone. After excimer ablation, 0.25% riboflavin was instilled on the stromal bed for 3 minutes. The flap was repositioned, followed by a total irradiation dose of 3.24 J ultraviolet A (UV-A) light administered to the corneal surface, using 18 mW/cm² UV-A for 3 minutes. Postoperative hyperopic regression (stability) was the primary outcome measure, defined by the difference in spherical equivalent (SEQ) at 1 week and 24 months postoperatively. Secondary measures reported uncorrected distance visual acuity, corrected distance visual acuity, cylinder vector analysis, subjective quality of vision, subjective night vision disturbances, and corneal haze.

RESULTS

At 24 months, the SEQ stability (P = .4273) and the magnitude of hyperopic regression (P = .5613) did not significantly differ between groups, with a small trend showing hyper-opic regression of 0.50 diopters or greater being less frequent in LASIK-ufCXL eyes. There were no significant differences in accuracy, efficacy, and safety (P > .05), with a small trend of more residual refractive astigmatism in the LASIK-ufCXL group (P = .3216, Cohen's d: -0.29). Subjective quality of vision trended inferior in LASIK-ufCXL eyes (P = .2237, Cohen's d: -0.25), with a greater haze grading (P = .0466, Cohen's d: 0.41).

CONCLUSIONS

Postoperative regression and stability were statistically equivalent between hyperopic LASIK vs LASIK-ufCXL, with identical safety. There were small clinical trends of lower efficacy, accuracy, and subjective quality of vision in LASIK-ufCXL eyes. [J Refract Surg. 2022;38(12):770-779.].

Posterior Corneal Astigmatism Does Not Influence Manifest-Treated Topography-guided LASIK Outcomes

PURPOSE

To investigate whether the magnitude of posterior corneal astigmatism (PCA) impacts refractive and visual outcomes of primary topography-guided laser in situ keratomileusis (LASIK) and to provide guidance on treating eyes with high PCA.

METHODS

Comparative retrospective analysis of 4,541 consecutive eyes treated with Contoura (Alcon Laboratories, Inc) on the manifest refractive astigmatism. Standard outcomes of the 1,514 eyes with the lowest PCA (first tercile; low PCA group) were compared to the 1,514 eyes with the highest PCA (last tercile; high PCA group). Pearson correlation coefficient was used to assess relationships between variables.

RESULTS

Preoperatively, 20.9% of eyes presented with PCA of 0.50 diopters (D) or greater. The mean PCA was 0.18 ± 0.07 D in eyes with low PCA, and 0.50 ± 0.11 D in eyes with high PCA. An equivalent number of eyes achieved a cumulative postoperative unilateral uncorrected distance visual acuity of 20/20 in both the low PCA and high PCA groups (95.3% vs 94.7%; P = .4489). The efficacy index of both low and high PCA eyes was identical (0.99 ± 0.06 vs 0.99 ± 0.08; P = .3192), as was the safety index (1.00 ± 0.02 vs 1.00 ± 0.03; P = .0110). The magnitude of preoperative PCA was weakly correlated with postoperative refractive astigmatism (R = 0.1323), but not with postoperative defocus equivalent (R = -0.0414) or spherical equivalent (R = -0.0128).

CONCLUSIONS

PCA does not negatively impact the outcomes of topography-guided LASIK targeting the manifest refraction, having identical accuracy, efficacy, and safety in eyes with both low and high PCA. There is no scientific basis to measure and consider PCA in topography-guided LASIK planning software or nomograms if the excimer laser treatment input targets the manifest refraction. [J Refract Surg. 2022;38(12):780-790.].

Large Axis Difference Between Topographic Anterior Corneal Astigmatism and Manifest Refractive Astigmatism: Can Topography-Guided LASIK Target the Manifest Axis?

PURPOSE

To investigate whether the degree of astigmatism axis discrepancy between preoperative manifest refractive astigmatism and anterior corneal astigmatism impacts refractive and visual outcomes of primary topography-guided laser in situ keratomileusis (LASIK) targeting the refractive astigmatism, and to provide guidance on treating eyes with very large axis discrepancy.

METHODS

Comparative retrospective analysis of 25,396 consecutive eyes treated with topography-guided LASIK on the manifest refractive astigmatism. Standard outcomes of the 14,534 eyes with small axis discrepancy (SAD) (Δ in axis ⩽ 10°) were compared to the 2,222 eyes with very large axis discrepancy (VLAD) (Δ in axis ⩾ 45°). Pearson correlation coefficient was used to assess relationships between selected variables.

RESULTS

The mean axis discrepancy was 4.47 ± 2.92° in SAD eyes, and 65.0 ± 13.4° in VLAD eyes. An equivalent number of eyes achieved a cumulative postoperative unilateral uncorrected distance visual acuity of 20/20 in both the SAD and VLAD groups (93.02% vs 93.42%; P = .4892). The efficacy index (0.98 ± 0.13 vs 0.98 ± 0.07; P = .3931) and the safety index (1.00 ± 0.11 vs 1.00 ± 0.03; P = .4757) were identical between groups. There was no clinically meaningful correlation between the preoperative axis discrepancy and preoperative total root mean square anterior corneal coma, postoperative refractive astigmatism, defocus equivalent, spherical equivalent, and angle of error, all with weak correlation coefficients (R = -0.02, -0.03, -0.02, 0.01, and 0.05).

CONCLUSIONS

Large preoperative axis discrepancy (45° to 90°) between refractive astigmatism and topography-measured anterior corneal astigmatism does not negatively impact topography-guided LASIK, having identical refractive and visual outcomes compared to eyes with small (0° to 10°) discrepancy. There is no basis to exclude eyes with large axis discrepancy from topography-guided LASIK, and these eyes should be treated on the manifest refractive astigmatism. [J Refract Surg. 2021;37(10):662-673.].

The Relationship Between Preoperative Anterior Corneal Higher Order Aberrations and Topography-Guided Excimer Ablation Depth

PURPOSE

To determine the correlation and relative contribution of preoperative anterior corneal Zernike coefficients to higher order aberration ablation depth (HOA-AD) with topography-guided excimer laser correction.

METHODS

Retrospective study of 46,271 consecutive preoperative virgin eyes. Anterior corneal Zernike coefficients (C6 to C27) and HOA-AD data on a 6.5-mm optical zone were analyzed from the Contoura (Alcon Laboratories, Inc) treatment software. Pearson correlations were performed to assess the relationship between Zernike coefficients and HOA-AD.

RESULTS

A strong direct relationship was found between the total root mean square (RMS) anterior corneal HOA and HOA-AD (R = 0.84; P < .001). The 3rd order HOAs (C6 to C9) accounted for most of the HOA-AD (R = 0.83; P < .001). Zernike orders 4, 5, and 6 had significantly weaker correlations (4th order: R = 0.30; 5th order: R = 0.38; 6th order: R = 0.29). Vertical coma was the individual HOA with the highest correlation (R = 0.59; P < .001). Combining vertical and horizontal coma as total RMS coma increased the correlation significantly (R = 0.76; P < .001). The average HOA-AD increased by 1.5 µm for each additional 0.1-µm increment of total RMS coma.

CONCLUSIONS

Anterior corneal Zernike coefficients directly and strongly correlate to the HOA-AD, with anterior corneal coma having the greatest contribution to HOA-AD. [J Refract Surg. 2020;36(8):506-510.].

Keratoconus Features on Corneal Higher-Order Aberration Ablation Maps: Proof-of-Concept of a New Diagnostic Modality

PURPOSE

To assess the potential application of corneal higher-order aberration (HOA) excimer ablation map imaging in identifying reproducible keratoconus (KC) features and to explore if newly derived map metrics correlate to Pentacam KC indices.

METHODS

Case series of 12 eyes with KC ≥ grade 2. Topolyzer Vario corneal imaging with its resultant HOA ablation map islands were analyzed for their centroid, distance from center, angular position, orientation, sphericity, diameter, area, and maximal ablation depth. Correlations to Pentacam indices were studied.

RESULTS

All eyes showed recurrent features with an arrangement of two elliptical paracentral ablation islands, one deep inferotemporal and one shallow superonasal, in direct mirror-like opposition to each other. These were always accompanied by superior peripheral ablation crescents. The two paracentral islands had highly reproducible distance from center (1.2 ± 0.1 mm and 1.3 ± 0. 2 mm) and angular positions (246.8 ± 15.9° and 76.7 ± 7.7°), with greater variation in ablation depth (68.3 ± 33.2 µm and 17.6 ± 12.1 µm). Distance from center of the peripheral superior crescents was highly reproducible (3.3 ± 0.1 mm), with a larger range of depth (74.5 ± 37.2 µm). The deep paracentral inferotemporal island "hot spot" was coincident with the topographical apical cone. Strong correlations were found between the depth of the inferotemporal island and Pentacam indices of posterior radius curvature (PRC: R = -0.74) and Belin/Ambrosio enhanced ectasia total deviation (BAD-D: R = 0.71).

CONCLUSION

The corneal HOA ablation map revealed a recurring, distinct, easily recognizable pattern in KC eyes. There was a strong correlation between the depth of novel HOA ablation map metrics and validated Pentacam KC indices. Novel information can be extracted from the corneal HOA ablation map giving it the potential to be a new modality to diagnose and grade KC.

The Impact of Image Registration for Ablation Orientation on Clinical Outcomes After Wavefront-Optimized Refractive Surgery in Eyes with Myopia and Astigmatism

Purpose

To compare the clinical outcomes from laser refractive surgery performed with the same laser with and without incorporating iris registration technology to compensate for ocular cyclotorsion.

Design

Single-site, two-arm, retrospective chart review.

Methods

Clinical outcomes at a single site after wavefront-optimized LASIK using the Wavelight excimer laser with and without the Vario imaging system for iris registration (IR) were evaluated. Eligible subjects were those that received on-label wavefront-optimized treatment of myopia with astigmatism >1.5 D. Measures of interest were the amount of residual refractive cylinder after surgery, the refractive error, and the best-corrected (BCVA) and uncorrected (UCVA) visual acuities, with a target follow-up of around 90 days.

Results

A total of 112 eligible eyes that were treated with IR and 126 similar eyes treated without IR (NO IR) were included. The refractive sphere and spherical equivalent refractions were statistically significantly different between groups (p < 0.05), but the mean differences were <0.1 D in both cases. Refractive cylinder averaged around 0.12 D and was not statistically significantly different between groups. The number of eyes with residual cylinder >0.50 D was higher in the NO IR group vs the IR group (6% vs 1%, respectively, p = 0.04). The mean logMAR UCVA and BCVA were statistically significantly better in the IR group, with a difference of 1.5 letters for UCVA and 1.0 letters for BCVA (p < 0.001 for both). Significantly more eyes in the IR group had a UCVA (p = 0.01) and a BCVA of 20/15 or better (p = 0.003). Overall, 96% of eyes in the IR group and 91% of eyes in the NO IR group had uncorrected visual acuity of 20/20 or better.

Conclusion

Iris registration with the VARIO imaging device demonstrably reduced the overall variability in clinical outcomes.

Refractive, visual, and subjective quality of vision outcomes for very high myopia LASIK from - 10.00 to - 13.50 diopters

Background

To evaluate laser-assisted in situ keratomileusis (LASIK) outcomes, subjective quality of vision (QoV) and patient satisfaction in eyes with very high myopia (VHM) above − 10.00 diopters (D).

Methods

Consecutive myopic and myopic-astigmatism eyes with spherical equivalent (SEQ) ranging between − 10.00 to − 13.50 D underwent LASIK with the WaveLight® Allegretto Wave® Eye-Q 400 Hz excimer laser. Treatment accuracy, efficacy, safety, stability, cylinder vectors, and higher-order aberrations were evaluated, together with subjective QoV and night vision disturbances (NVDs).

Results

114 eyes had a preoperative SEQ of − 11.02 ± 0.81 D, with a median follow-up of 24 months. A total of 72, 84, and 94% of eyes were within ± 0.50, ± 0.75 and ± 1.00 D of intended SEQ (R² = 0.71). The efficacy index was 0.93 ± 0.20, with 51 and 81% of eyes achieving 20/20 and 20/25. The astigmatism correction index was 0.95 ± 0.33. The safety index was 1.05 ± 0.12. The average myopic regression was − 0.51 ± 0.38 D. Preoperative QoV scores improved significantly postoperatively (7.5 ± 0.8 vs. 9.1 ± 0.7; P <  0.001), with less NVDs (P <  0.001). Total, spherical and coma root mean square (RMS) postoperative ocular higher-order aberrations were 1.07 ± 0.34, 0.67 ± 0.25, and 0.70 ± 0.40 μm.

Conclusions

Very high myopia LASIK between − 10.00 to − 13.50 D is safe and results in good visual outcomes, with high patient satisfaction and a significant improvement in patient-reported QoV after surgery. Appropriately selected patients within this very high myopia group can be included as LASIK candidates.

Outcomes Comparison Between Wavefront-Optimized and Topography-Guided PRK in Contralateral Eyes With Myopia and Myopic Astigmatism

PURPOSE

To compare clinical outcomes between topography-guided customized ablation treatment (TCAT) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in fellow eyes of myopic patients.

METHODS

Forty-six eyes of 23 patients who underwent PRK were included. WFO ablation was performed in one eye (WFO group) and TCAT in the fellow eye (TCAT group). The customized treatment plan was based on the Topolyzer Vario topography system (Alcon Laboratories, Inc) data. The patients were observed for 12 months after the procedure.

RESULTS

One year after the surgery, there was no significant difference in the manifest refraction spherical equivalent, sphere, or cylinder variables between the two groups (P > .05). In both groups, 96% of eyes achieved an uncorrected distance visual acuity of 20/20 or better at 12 months postoperatively. Accuracy, safety, and efficacy of the refractive and visual outcomes were similar in the two groups. The postoperative higher order aberrations magnitude was lower in the TCAT group, but this was not statistically significant (P > .05). During the 12-month follow-up, no patient described any symptoms related to glare, halos, or starbursts in either eye. Other postoperative complications, such as infection or cor-neal infiltrates, did not occur in either group.

CONCLUSIONS

TCAT and WFO ablations provided similar outcomes after PRK for myopia and myopic astigmatism correction. There were no statistically significant differences in postoperative corneal wavefront analysis. [J Refract Surg. 2020;36(6):358-365.].