Allogenic Lenticular Implantation for Correction of Refractive Error and Ectasia: Narrative Review

Lenticule Intrastromal Keratoplasty for the Correction of Iatrogenic High Hyperopia

PURPOSE

The aim of this study was to evaluate the safety, efficacy, and predictability of lenticule intrastromal keratoplasty (LIKE) for the correction of iatrogenic high hyperopia.

METHODS

Three patients (4 eyes) were referred to our department because of overcorrection of myopia induced by femtosecond laser-assisted in situ keratomileusis. All eyes exhibited hyperopia (between +4.00 and +8.00 D) and thin corneas ranging from 307 to 378 μm. Because of the regression of the use of laser ablation to correct high hyperopia and thin corneas, we initially adopted LIKE to correct iatrogenic high hyperopia in all 4 eyes. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, and anterior segment optical coherence tomography findings were recorded during each follow-up evaluation.

RESULTS

No postoperative complications, such as interface haze and opacification, were observed in the 4 eyes during each follow-up evaluation, with an average follow-up of 9.50 months. All eyes had significantly improved UDVA postoperatively. A total of 3 eyes achieved an UDVA of 20/25 or better while the other 1 eye had an UDVA of 20/40 postoperatively. In addition, 2 of the 4 eyes had a postoperative UDVA equal to or better than preoperative CDVA. No eyes lost any CDVA lines. All 4 eyes were within ±0.50 D of the spherical power (intended target of 0). The central corneal thickness and curvature of the anterior corneal surface in all 4 eyes increased postoperatively. Anterior segment optical coherence tomography revealed that the lenticule was transparent, with no wrinkles or offsets, during each follow-up evaluation.

CONCLUSIONS

LIKE for the correction of iatrogenic hyperopia has good efficacy and safety. Although an extremely thin cornea after overcorrection may not be suitable for hyperopic laser enhancement, LIKE is a good choice because of its good predictability and ability to restore the normal corneal structure.

Biomechanical changes in keratoconus after customized stromal augmentation

PURPOSE

To verify corneal biomechanical changes, poststromal augmentation using myopic small-incision lenticule extraction's (SMILEs) lenticules in advanced keratoconus (KCN) through Corvis ST (Oculus, Wetzlar, Germany).

MATERIALS AND METHODS

A clinical trial enrolled 22 advanced KCN patients. We implanted lenticules exceeding 100 μ according to a nomogram and evaluated biomechanical factors through Corvis ST at 3-, 6-, and 24-month postimplantation. We examined parameters during the first applanation (A1), second applanation (A2), highest concavity (HC)/max concavity events, and Vinciguerra screening parameters, as recently established criteria derived from the ideal blend of diverse biomechanical and ocular factors and formulated through the application of logistic regression. Regression analyses explored relationships with age, mean keratometry value, thickness, sphere, cylinder, and best-corrected visual acuity.

RESULTS

Patients were well matched for age, intraocular pressure, and central corneal thickness (CCT). The mean spherical equivalent decreased from -13.48 ± 2.86 Diopters (D) to -8.59 ± 2.17 D (P < 0.007), and mean keratometry decreased from 54.68 ± 2.77 D to 51.95 ± 2.21 D (P < 0.006). Significant increases were observed in HC time (HCT), Radius-central curvature radius at the HC state-, peak distance (PD) during HC state, CCT, first applanation time, and stiffness parameter (A1T and SP-A1), whereas HC deformation amplitude, maximum deformation amplitude ratio at 2 mm, Corvis Biomechanical Index (CBI), integrated radius (IR), second applanation deformation amplitude (A2DA), first applanation velocity and deflection amplitude (A1V and A1DeflA) significantly decreased postlenticule implantation. Multivariable regression revealed age positively correlated with SP-A1 (P = 0.003) and negatively with HC delta Arc length (P = 0.007). Mean K positively correlated with CCT (P = 0.05) and negatively with CBI (P = 0.032). Best-corrected visual acuity positively correlated with HCT (P = 0.044), and the cylinder positively correlated with PD (P = 0.05) and CCT (P = 0.05) whereas negatively with IR (P = 0.025).

CONCLUSIONS

Stromal augmentation using myopic SMILE lenticules induces significant corneal biomechanical changes in KCN.

Visual Outcomes and Safety of a Refractive Corneal Inlay for Presbyopia: One-Year Results

PURPOSE

To determine the visual outcomes and safety 12 months after implantation of the Presbia Flexivue Microlens refractive corneal inlay.

METHODS

In this prospective, non-randomized trial, 22 patients with a mean age of 52.54 ± 2.86 years were implanted with the Flexivue Microlens refractive corneal inlay in the non-dominant eye at the Department of Ophthalmology, Goethe University, Frankfurt, Germany. Corrected near, intermediate, and distance (CNVA, CIVA, and CDVA) visual acuity and uncorrected near, intermediate, and distance (UNVA, UIVA, and UDVA) visual acuity, manifest refraction, subjective quality of vision, endothelial cell count, and contrast sensitivity were measured 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively.

RESULTS

For binocular CDVA, no patient lost two or more lines and 30% lost only one line at the 12-month visit. In the eye that had surgery, 85% of the patients lost two or more lines of UDVA, which was statistically significant. Sixty-five percent of the patients gained one or more lines in binocular UIVA, and 80% achieved 20/40 or better in DCIVA. UNVA showed a statistically significant improvement, with 90% of the patients achieving 20/40 or better 12 months after implantation. A total of 85% gained two or more lines in binocular UNVA.

CONCLUSIONS

This refractive corneal inlay showed an improvement in binocular UNVA, UIVA, CNVA, and CIVA, whereas binocular CDVA and UDVA were not statistically affected. [J Refract Surg. 2024;40(1):e1-e9.].