Visual outcomes of topography-guided excimer laser surgery for treatment of patients with irregular astigmatism

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.

Topography-Guided Transepithelial Photorefractive Keratectomy for the Treatment of Persistent and Visually-Significant Adenoviral Corneal Infiltrates

Purpose

To evaluate visual and refractive outcomes of customized photorefractive keratectomy (PRK) in subjects with persistent subepithelial corneal opacities secondary to adenoviral epidemic keratoconjunctivitis (EKC).

Patients and Methods

Prospective study, which recruited patients with persistent and visually-significant post-EKC corneal opacities unresponsive to prolonged topical therapy (6 months or more). Outcome measures: uncorrected and best-corrected distance visual acuity, subjective refractive astigmatism, keratometric astigmatism, spherical equivalent, minimum corneal thickness, and corneal morphological irregularity index. Subjects were followed for 12 months post-treatment.

Results

Eighteen eyes of 18 patients aged between 32 and 75 years treated with topography-guided transepithelial PRK with iRes excimer laser (iVIS Technologies, Taranto, Italy) from June 2020 to July 2021. After 12 months, the mean UDVA improved from 1.0±0.00LogMAR pre-op to 0.15±0.154LogMAR, and the mean CDVA improved from 0.4±0.41LogMAR pre-op to 0.0±0.00LogMAR. With respect to UDVA, all treated eyes (100%) showed an improvement of 6 ETDRS lines or more and with respect to CDVA, 9 out of 18 eyes (50%) showed an improvement of 6 ETDRS lines or more. The mean ablation depth was 54.7±5.9μm. A statistically significant improvement was observed in all topographic indices. No infiltrate recurrence, post-treatment corneal haze, ocular hypertension or other side effects were observed throughout the follow-up period.

Conclusion

Topography-guided PRK could be considered an effective and safe treatment option to improve visual acuity in patients affected by persistent and visually-significant subepithelial corneal infiltrates caused by EKC.

A Comparison of Three Cylindrical Treatment Strategies for Topography-Guided LASIK: Manifest, Topographic, and ZZ VR Cylinders

Purpose

This study was designed to compare the clinical outcomes of three cylindrical treatment strategies using manifest, topographic, and Zhang & Zheng vector-compensated refraction (ZZ VR) cylinders, for topography-guided laser-assisted in situ keratomileusis (LASIK) and to identify the laser programming strategy that optimizes refractive astigmatism outcomes and visual acuity.

Methods

Consecutive patients referred for therapeutic refractive surgery between March and September 2018 at a single center were prospectively analyzed. Using double-masked simple randomization, patients were randomly assigned to undergo treatment based on manifest cylinder, topographic cylinder, and ZZ VR cylinder strategies. Uncorrected distance visual acuity and astigmatic refraction were analyzed preoperatively and 6 months postoperatively.

Results

A total of 138 eyes from 71 patients met the inclusion criteria. The manifest group consisted of 46 eyes in 24 patients, the topographic group consisted of 43 eyes in 22 patients, and the ZZ VR group consisted of 49 eyes in 25 patients. The absolute residual cylindrical refractions at 6 months postoperatively in these three groups were 0.69 ± 0.32 D, 0.58 ± 0.31 D, and 0.42 ± 0.19 D, respectively (P < 0.001; adjusted P < 0.01 for manifest vs ZZ VR, adjusted P = 0.08 for topographic vs ZZ VR). The percentages of postoperative absolute residual cylindrical power within 0.50 D in the manifest, topographic, and ZZ VR groups were 30.4%, 55.8%, and 59.2%, respectively (P = 0.01; adjusted P = 0.06 for manifest vs topographic, adjusted P = 0.02 for manifest vs ZZ VR).

Conclusion

The ZZ VR strategy may achieve better outcomes, as determined by cylindrical correction and visual activity, during topography-guided LASIK.

Clinical Trial Registration Number

ChiCTR1900025779.

Clinical and Refractive Outcomes after Topography-guided Refractive Surgery Planned Using Phorcides Surgery Planning Software

PURPOSE

To evaluate prospectively the clinical outcomes of topography-guided laser in situ keratomileusis (LASIK) surgery performed with Contoura® Vision using the Wavelight® excimer laser and planned with the Phorcides Analytical Engine.

SETTING

Four clinical practices in the USA.

DESIGN

Prospective, single-arm interventional study.

METHODS

130 eyes of 65 patients with myopia and/or myopic astigmatism were enrolled in a prospective study of visual and refractive outcomes following treatment with Contoura® Vision using the Wavelight® EX500 excimer laser to achieve optimal distance vision. At 3 months postoperatively, uncorrected distance vision (UDVA), manifest refraction (MR), and corrected distance vision (CDVA) were measured and compared to historical controls.

RESULTS

At 3 months after surgery, 100%, 89% and 28% of eyes achieved UDVA of 20/20, 20/15/ and 20/10 or better, respectively. Ninety-two percent of eyes had postoperative UDVA equal to or better than their preoperative CDVA. Postoperative CDVA was equal to, 1 line better, or 2 lines better than the preoperative CDVA in 53%, 40%, and 6% of eyes, respectively. Only 1 eye lost 1 line of CDVA, and no eyes lost more than 1 line of CDVA. There was a significant decrease in subjective visual complaints, including glare, halos, difficulty driving at night, reading difficulty, starbursts, fluctuation in vision, and light sensitivity.

CONCLUSION

The Phorcides Analytical Engine can be used to optimize visual outcomes for the correction of myopia and myopic astigmatism.

Topography-guided corneal surface laser ablation combined with simultaneous accelerated corneal collagen cross-linking for treatment of keratoconus

Background

to study the outcomes of topography-guided customized excimer laser subepithelial ablation combined with accelerated CXL for progressive keratoconus.

Methods

Thirty-one eyes of 30 patients with progressive keratoconus were included in this prospective study. Topography-guided excimer laser ablation without refractive correction was performed. Simultaneous accelerated collagen cross-linking with ultraviolet light of 30 mW/cm² for 4 min was followed. Uncorrected distance visual acuity (UCVA), manifest refraction, corrected distance visual acuity (CDVA), tomograghy were examined at postoperative 1, 6, and 12 months.

Results

UDVA improved slightly after surgery (P > 0.05). BSCDVA improved significantly from 0.32 ± 0.20 logMAR to 0.15 ± 0.14 logMAR at postoperative 12 months (P < 0.05). During 12-month follow-ups, there were no significant differences in manifest refraction and corneal keratometry except for maximal keratometry value of the anterior surface (K_apex), which decreased significantly from 57.23 ± 5.09D to 53.13 ± 4.47D (P < 0.05). Even though the thinnest corneal thickness decreased from 465 ± 24 μm to 414 ± 35 μm (P < 0.05), curvature asymmetry index front (SIf), keratoconus vertex front (KVf) and Baiocchi Calossi Versaci index front (BCVf) decreased significantly till postoperative 12 months (P < 0.05). Corneal higher-order aberrations and coma also decreased significantly till 12 months after surgery (P < 0.05).

Conclusions

Topography-guided surface ablation without refractive correction combined with simultaneous accelerated collagen cross-linking provided good stability in refraction and corneal curvature, and also showed significant improvement in BSCDVA, corneal regularity and corneal optical quality.

Visual rehabilitation by using corneal wavefront-guided transepithelial photorefractive keratectomy for corneal opacities after epidemic keratoconjunctivitis

PURPOSE

To evaluate long-term visual and refractive outcomes of corneal wavefront-guided transepithelial photorefractive keratectomy (t-PRK) with mitomycin C for the treatment of corneal opacities secondary to adenoviral epidemic keratoconjunctivitis.

METHODS

Records of patients who underwent corneal wavefront-guided t-PRK with excimer laser from January 2012 to December 2018 were retrospectively reviewed. Preoperative and postoperative uncorrected visual acuity, best-spectacle corrected visual acuity, slit-lamp biomicroscopic examination findings, manifest refraction, and corneal aberrations and fundus examination findings were evaluated.

RESULTS

Twenty-two eyes of 22 patients comprising 12 male (55%) and 10 female (45%) were treated. The mean age was 34.5 ± 10.8 years (range 19-55). The mean follow-up time was 34.4 ± 17.50 months (range 13-61 months). There was a statistically significant improvement in UCVA and BSCVA (p < 0.001 and p = 0.02), and there was a significant decrease in total higher-order aberrations, spherical, coma and trefoil aberration at postoperative first year (p < 0.001 in each). In two eyes of two patients, minimal haze formation was observed after the procedure, and both eyes were treated with topical steroid. No recurrence was observed in subepithelial infiltrates in any patient during long-term follow-up.

CONCLUSION

In long-term clinical follow-up, corneal wavefront-guided t-PRK treatment is an effective and reliable treatment method for rehabilitation of visual impairment due to corneal scars following adenoviral infections, in properly selected patients.

Correction of Myopic Astigmatism with Topography-Guided Laser In Situ Keratomileusis (TOPOLINK)

We aim to assess the feasibility of topography-guided laser in situ keratomileusis (TOPOLINK) for correcting pre-existing and surgical-induced astigmatism. A retrospective, single center cohort study was conducted. Patients with pre-existing irregular myopic astigmatism were recruited into the primary group and those with irregular myopic astigmatism following laser in situ keratomileusis (LASIK) were recruited into the enhancement group. The changes in uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), maximum astigmatism, spherical equivalent (SE) and patient satisfaction were recorded. The Chi-square test, Mann-Whitney U test and Generalized Linear Mixed Model were utilized for the analysis in the current study. A total of 18 eyes were studied in the primary group and 14 eyes were examined in the enhancement group. One year postoperatively, the UCVA, BCVA, maximum astigmatism and SE improved significantly in both the primary and the enhancement groups (all p < 0.05). The UCVA (p = 0.046) and SE (p = 0.003) were worse in the primary group preoperatively but became similar in both groups postoperatively, while the BCVA and maximum astigmatism remained identical between groups throughout the study period (all p < 0.05). In addition, the rate of high and moderate satisfaction reached 90.0% in the primary and the enhancement groups, without significant differences (p = 0.871). In conclusion, the TOPOLINK showed high predictability and will contribute to similar outcomes between primary and postoperative irregular myopic astigmatism concerning visual acuity, refractive status and subject satisfaction.

Topography-Guided Refractive Astigmatism Outcomes: Predictions Comparing Three Different Programming Methods

Purpose

To identify the laser programming strategy that will achieve optimal refractive outcomes of LASIK with a topography-guided laser for eyes with a disparity between cylinder measured by manifest refraction and cylinder measured by topography.

Setting

Six surgeons at 5 clinical sites in the USA.

Design

Retrospective data review.

Methods

Preoperative, treatment, and postoperative data on 52 eyes that underwent topography-guided LASIK with the WaveLight EX500 Contoura^® Vision excimer laser ablation profile in which the vectors representing the preoperative refractive cylinder and the cylinder measured by the WaveLight^® Topolyzer™ VARIO Diagnostic Device (Vario cylinder) differed by >/= 0.50D and/or >/= 10 degrees of orientation were analyzed retrospectively. Data were contributed by six surgeons using the laser at 5 different clinical sites. Vector analysis of postoperative cylindrical refractive error and the actual laser programming strategy was used to calculate the cylindrical correction that would, theoretically, have completely eliminated postoperative refractive cylinder. This was compared to expected results using the preoperative manifest cylinder, the topographic cylinder, and the Phorcides Analytic Engine (Phorcides LLC, North Oaks MN; Phorcides). For analysis, subjects were stratified on the basis of the vector difference between Manifest and Topo cylinder (High, >0.75 D; and Low, ≤0.75 D).

Results

The poorest calculated theoretical outcomes were obtained with the manifest refraction (centroid: −0.43, 0.22; mean calculated error vector: 0.56 ± 0.42 D; p=ns). Better outcomes were obtained with the topographically measured refraction (centroid: 0.37, 0.02; mean calculated error vector: 0.47 ± 0.33 D; p=ns). The best outcomes were obtained with Phorcides (centroid: −0.15, 0.06; mean calculated error vector: 0.39 ± 0.28 D; p=ns). The mean error vector magnitude in the Phorcides Low group was significantly lower than for the Manifest and Topo Low groups (0.26 D vs 0.48 D and 0.33 D; p<0.01). The mean error magnitude in the Phorcides High group was nearly 0.25 D lower than for the Manifest High group (0.48 D vs 0.70 D; p<0.01), but was the same as for the Topo High group (0.48 D vs 0.48 D).

Conclusion

Our study suggests that using the topographically measured cylinder or the cylinder selected by Phorcides will produce more desirable refractive outcomes than entry of the preoperative refractive cylinder as the basis for correction of myopia and myopic astigmatism with the WaveLight Contoura Vision excimer laser.

Main Complications of Photorefractive Keratectomy and their Management

Photorefractive keratectomy (PRK) was the first surface ablation procedure introduced for the treatment of refractive errors and has been proven to be effective and safe. In some cases, however, the patient may not be totally satisfied with the final result and retreatment may be necessary. We performed a literature review to describe the main conditions that may arise following PRK that may require retreatment and new promising techniques to allow customized and effective treatments for patients. There is currently no gold standard for retreatment of residual refractive error after PRK. The surgeon must take into account the patient's history and type of problem when choosing the most appropriate technique. LASIK and PRK are the main options. Haze can be treated with good results with phototherapeutic keratectomy and mytomicin C. High order aberrations and decentration may be addressed with topographically-guided excimer photoablation or with wavefront-guided PRK.

Femtosecond laser-assisted astigmatic keratotomy: a review

Background

Astigmatic keratotomy (AK) remains an accessible means to correct surgically induced or naturally occurring astigmatism. The advantages of femtosecond laser-assisted astigmatic keratotomy (FSAK) over conventional methods have been recognized recently.

Main text

This review evaluates the efficacy, complications, and different methods of FSAK for correction of astigmatism in native eyes and those that underwent previous penetrating keratoplasty (PKP).

The penetrating and intrastromal FSAK (IFSAK) techniques can reduce post-keratoplasty astigmatism by 35.4% to 84.77% and 23.53% to 89.42%, respectively. In native eyes, the penetrating and IFSAK techniques reduce astigmatism by 26.8% to 58.62% and 36.3% to 58% respectively, implying that the magnitude of the astigmatic reduction is comparable between the two FSAK procedures. Nonetheless, IFSAK offers the additional advantages of almost no risk of infection, wound gape, and epithelial ingrowth. The use of nomograms, anterior-segment optical coherence tomography, and consideration of posterior cornea and corneal biomechanics are helpful to enhance the efficacy and safety of FSAK. The complications of FSAK in eyes that underwent PKP include overcorrection, visual loss, microperforations, infectious keratitis, allograft rejection, and endophthalmitis. The reported difficulties in native eyes include overcorrection, anterior gas breakthrough, and suction loss.

Conclusions

In eyes that underwent PKP, FSAK effectively reduces high regular or irregular astigmatism, with rare and manageable complications. Nevertheless, the drawbacks of the procedure include the potential loss of visual acuity and low predictability. For native eyes undergoing femtosecond laser-assisted cataract surgery, IFSAK is a good choice to correct low astigmatism (< 1.5 diopters). The refractive effect of astigmatism from the posterior cornea needs to be considered in the nomograms for native eyes undergoing refractive cataract surgery. To further improve the efficacy of FSAK, more large-scale randomized studies with longer follow-up are needed.