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Clinical Outcomes of a New Type of Continuous Intrastromal Corneal Ring for Treatment of Keratoconus

PURPOSE

The purpose of this study was to evaluate the efficacy and safety of implantation of a new continuous corneal ring in keratoconic corneas of an Iranian population.

METHODS

This study was conducted on 95 contact lens-intolerant keratoconic eyes with clear central corneas. A continuous corneal ring, annular intrastromal corneal inlay (AICI), was inserted using femtosecond laser in all cases. Patients were followed up for 1, 3, and 12 months postsurgery. Visual and subjective refractive outcomes were evaluated in each examination. Besides, keratometry and aberrometric values were recorded before and 12 months after surgery. Finally, vector analysis of refractive astigmatism was performed using the Alpins method.

RESULTS

The uncorrected and corrected distance visual acuities improved significantly 12 months after surgery from 0.91 ± 0.39 to 0.38 ± 0.22 (P < 0 0.001) and 0.33 ± 0.21 to 0.13 ± 0.11 logMAR (P < 0.001), respectively. Moreover, spherical and cylindrical refractive components reduced from -2.52 ± 2.62 to -0.76 ± 1.78 D (P < 0.001) and -4.14 ± 1.64 to -1.91 ± 1.18 D (P < 0.001), respectively. The mean anterior keratometry had a significant reduction 12 months after AICI insertion (P< 0.001). Primary coma and spherical aberration values showed a significant increase (both, P < 0.05). Our results showed 100% safety (safety index: 1.8) and 45% efficacy (efficacy index: 1).

CONCLUSIONS

AICI implantation seemed to be a safe and effective procedure for improving visual acuity and refractive outcomes in subjects with keratoconus.

Centration of myopic refractive ablation: should we center treatment on the pupil or the visual axis?

The purpose of this study is to compare pupil versus corneal vertex-centered ablation for myopic laser refractive surgery. This study is a retrospective case series of right eyes of consecutive myopic patients undergoing either photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) with pupil or corneal vertex-centered ablation from January 2018 to April 2018. Overall 258 eyes of 258 patients were included. Of the 104 that underwent LASIK, 52 were treated centered on the corneal vertex (50%), and of the 154 that underwent PRK, 77 were treated centered on the corneal vertex (50%). There were no significant differences in baseline age, gender, spherical equivalence, sphere, cylinder, or angle kappa between both groups in either LASIK or PRK. There were no significant differences between the corneal vertex-centered and pupil-centered groups in terms of efficacy index (LASIK: 1.02 ± 0.14 vs 1.01 ± 0.13, p = 0.86; PRK: 1.00 ± 0.13 vs 0.99 ± 0.15, p = 0.61), safety index (LASIK: 1.02 ± 0.12 vs 1.01 ± 0.13, p = 0.70; PRK:1.02 ± 0.12 vs 1.02 ± 0.09, p = 0.97), and residual astigmatism (LASIK: 0.26 ± 0.25 vs 0.23 ± 0.28, p = 0.65; PRK:0.37 ± 0.41 vs 0.39 ± 0.31, p = 0.78). In mixed effect models, there were no significant differences between the corneal vertex-centered and pupil-centered groups when accounting for angle kappa (p > 0.05). Patients with large angle kappa (> 300 μm) eyes yielded similar results (p > 0.05). For conclusion, in myopic refractive surgery, performing ablation centered on the corneal vertex or on the pupil leads to similar outcomes regardless of the amount of angle kappa.

Factors Predicting the Need for Re-treatment After Laser Refractive Surgery in Patients With High Astigmatism: A Large Database Analysis

PURPOSE

To identify the potential risk factors that increase the likelihood of requiring re-treatment following refractive surgery in patients with high astigmatism (3.00 diopters or greater).

METHODS

This retrospective study included patients who underwent laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between January 2005 and December 2019 at the Care-Vision Laser Centers, Tel-Aviv, Israel. Patients with high astigmatism (3.00 diopters or greater) were included and divided into two groups according to whether or not they underwent additional refractive surgery (re-treatment) during the study period.

RESULTS

Overall, 2,024 eyes (2,024 patients) were included in the final analysis of this study. In total, 3.1% of the eyes (n = 63) underwent re-treatment. Throughout the study period, there was a significant reduction in the 2-year annual re-treatment rates, with a decline from 7.0% for primary surgeries performed in 2005 to 0.0% for primary surgeries performed in 2017 (r =-0.65, P = .015). The re-treatment group had significantly older preoperative age. They were also more likely to be male and have preoperative against-the-rule astigmatism and preoperative mixed astigmatism. Binary logistic regression analysis demonstrated that preoperative age, male gender, mixed astigmatism, and earlier year of surgery were all associated with higher re-treatment rates.

CONCLUSIONS

The following factors are associated with higher rates of re-treatment in patients with high astigmatism: older preoperative age, male gender, and mixed astigmatism. These factors may be incorporated into nomograms to reduce future re-treatment rates in this population. [J Refract Surg. 2021;37(6):366-371.].

Evaluation of Astigmatic Correction Using Vector Analysis after Combined Femtosecond Laser-Assisted Phacoemulsification and Intrastromal Arcuate Keratotomy

The aim of this study was to evaluate astigmatic correction in patients with mild to moderate astigmatism after combined femtosecond laser-assisted cataract surgery (FLACS) and intrastromal arcuate keratotomy (ISAK), using vector analysis. This retrospective study included patients with corneal astigmatism of 0.5–3.0 diopters (D) who underwent FLACS and ISAK. Vector analyses of astigmatism were performed using the Alpins method, considering three vectors: target-induced astigmatism (TIA), surgically induced astigmatism (SIA), and difference vector (DV). Magnitude of error (ME), angle of error (AE), correction index (CI), and coefficient of adjustment (CA) were calculated. Subgroup analysis according to the axis of astigmatism, patient age, and white to white (WTW) diameter was conducted. In total, for the 79 eyes of 79 patients, the TIA was 1.21 ± 0.52 D, the SIA was 0.76 ± 0.53 D, and the DV was 0.86 ± 0.50 D. The ME (difference between SIA and TIA) was −0.46 ± 0.45 D, and the CI (ratio of SIA and TIA) was 0.62 ± 0.34; both these parameters demonstrated slight undercorrection. The CA (inverse of the CI) was 2.48 ± 2.61. The AE was 4.02° ± 28.7°, and the absolute AE was 21.7° ± 19.0°. In the univariate regression analyses to identify factors that affected the CI, there was a negative correlation between age and the CI (P=0.022). In conclusion, vector analysis after the combined FLACS and ISAK revealed slight undercorrection, regardless of the astigmatism meridian. The precision of the nomogram should be improved through long-term vector analysis for the results of arcuate keratotomy and through further research on the relationship between patient demographics and CI. Overall, this study has shown that FLACS and ISAK could reduce postoperative corneal astigmatism effectively and safely.

Factors Associated With Improvement in Vision Following Femtosecond Astigmatic Keratotomy in Post-Keratoplasty Keratoconus Patients

PURPOSE

To evaluate factors associated with improvement in vision following femtosecond astigmatic keratotomy (FSAK) in patients with keratoconus post-keratoplasty.

DESIGN

Retrospective, interventional case series.

METHODS

The study took place in an institutional setting. This was a retrospective study that included patients with keratoconus who underwent FSAK for astigmatism following penetrating (PKP) or deep anterior lamellar keratoplasty (DALK). Success was defined as improvement in 3 Early Treatment Diabetic Retinopathy Study lines (doubling of the visual angle) of uncorrected distance visual acuity (UDVA) or best spectacle-corrected visual acuity (BSCVA).

RESULTS

A total of 56 eyes in 56 patients with keratoconus were included. Following FSAK, there was a significant improvement in UDVA (1.30 ± 0.49 to 0.87 ± 0.58 logarithm of minimal angle of resolution [logMAR]; P < .001), BSCVA (0.40 ± 0.26 to 0.27 ± 0.29 logMAR; P <.001), and corneal astigmatism (8.69 ± 2.72 to 3.92 ± 2.13 diopter [D]; P < .001). Success was achieved in 60.7% (34/56) of cases, and this group had a higher proportion of previous PKP (73.5% vs 45.5%; P = .03), worse preoperative UDVA (1.42 ± 0.47 vs 1.11 ± 0.47 logMAR; P = .03), and a greater preoperative manifest cylinder (7.56 ± 2.26 vs 5.72 ± 2.12 D; P = .01). In multiple regression analysis, PKP (vs DALK) (odds ratio [OR]: 8.52; P = .009), worse preoperative UDVA (OR: 9.08, P = .02), and greater preoperative cylinder (OR: 1.51; P = .04) were independently associated with success, and, when combined, led to a sensitivity and specificity of 84.6% and 93.8%, respectively, in predicting success. The optimal cutoff predicting success with a preoperative cylinder was a cylinder >6.75 D.

CONCLUSION

Approximately 60% of patients with keratoconus post-keratoplasty experience doubling of the visual angle following FSAK. Patients with previous PKP and a greater cylinder are more likely to benefit from this procedure. Separate nomograms for DALK and PKP patients may be warranted.