Dataset Information

Corneal Biomechanical Properties after FS-LASIK with Residual Bed Thickness Less Than 50% of the Original Corneal Thickness.

ABSTRACT: The changes in corneal biomechanical properties after LASIK remain an unknown but important topic for surgical design and prognostic evaluation. This study aims to observe the postoperative corneal biomechanical properties one month after LASIK with amount of corneal cutting (ACC) greater than 50% of the central corneal thickness (CCT).FS-LASIK was performed in 10 left rabbit eyes with ACC being 60% (L60) and 65% (L65) of the CCT, while the right eyes (R) were the control. After 4 weeks, rabbits were executed and corneal strip samples were prepared for uniaxial tensile tests.At the same strain, the stresses of L65 and L60 were larger than those of R. The elastic moduli of L60 and L65 were larger than those of R when the stress was 0.02 MPa, while they began to be less than those of R when stress exceeds the low-stress region. After 10 s relaxation, the stress of specimens L65, L60, and R increased in turn.The elastic moduli of the cornea after FS-LASIK with ACC greater than 50% of the CCT do not become less under normal rabbit IOP. The limit stress grows with the rise of ACC when relaxation becomes stable.

SUBMITTER: Zhang H

PROVIDER: S-EPMC5821977 | biostudies-other | 2018

REPOSITORIES: biostudies-other

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Corneal Biomechanical Properties after FS-LASIK with Residual Bed Thickness Less Than 50% of the Original Corneal Thickness.

Zhang Haixia H Khan Muhammad Ahmad MA Zhang Di D Qin Xiao X Lin Ding D Li Lin L

Journal of ophthalmology 20180111

<h4>Background</h4>The changes in corneal biomechanical properties after LASIK remain an unknown but important topic for surgical design and prognostic evaluation. This study aims to observe the postoperative corneal biomechanical properties one month after LASIK with amount of corneal cutting (ACC) greater than 50% of the central corneal thickness (CCT).<h4>Methods</h4>FS-LASIK was performed in 10 left rabbit eyes with ACC being 60% (L60) and 65% (L65) of the CCT, while the right eyes (R) were ...[more]

PMID: 29576876

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Project description:BackgroundTo compare the corneal biomechanical changes after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) with the same programmed optical zone (POZ) and similar refractive correction in patients with high myopia.MethodsIn this prospective comparative study of the contralateral eye, 50 patients with high myopia with the same POZ and similar refractive correction who underwent SMILE in one eye and FS-LASIK in the other eye. Corneal biomechanical parameters and central corneal thickness (CCT) were measured using a Corvis ST II. All the patients were evaluated during follow-up visits beyond one year. Additionally, the corneal volume (CV) of the 10-mm diameter region was measured using a Pentacam.ResultsAmbrosio relational thickness to the horizontal profile (ARTh) and stiffness parameter A1 (SP-A1) decreased significantly after SMILE and FS-LASIK, whereas deformation amplitude ratio 2.0 mm (DA ratio 2.0 mm) and integrated radius (IR) increased significantly in both groups. The ARTh and SP-A1 were greater after SMILE than those after FS-LASIK at all the follow-up visits. In addition, there were greater amounts of CCT and CV after SMILE compared with that after FS-LASIK. Moreover, a positive correlation was found between ARTh and SP-A1 and postoperative CCT, while a negative correlation was found between IR and DA ratio 2.0 mm and postoperative CCT. A moderate correlation was observed between SP-A1 and CV after both SMILE and FS-LASIK, whereas there were no relationships between CV and ARTh, IR, or DA ratio 2.0 mm.ConclusionsSMILE had greater CCT, CV, ARTh, and SP-A1 than FS-LASIK in high myopia with the same POZ and similar refractive correction. Our results demonstrated that SMILE had lesser effect on corneal biomechanics than FS-LASIK in high myopia.KeywordsCorneal biomechanics; Corvis ST II; small incision lenticule extraction (SMILE); femtosecond laser-assisted in situ keratomileusis (FS-LASIK); high myopia.

Project description:SIGNIFICANCE:Measured corneal biomechanical properties are driven by intraocular pressure, tissue thickness, and inherent material properties. We demonstrate tissue thickness as an important factor in the measurement of corneal biomechanics that can confound short-term effects due to UV riboflavin cross-linking (CXL) treatment. PURPOSE:We isolate the effects of tissue thickness on the measured corneal biomechanical properties using optical coherence elastography by experimentally altering the tissue hydration state and stiffness. METHODS:Dynamic optical coherence elastography was performed using phase-sensitive optical coherence tomography imaging to quantify the tissue deformation dynamics resulting from a spatially discrete, low-force air pulse (150-?m spot size; 0.8-millisecond duration; <10 Pa [<0.08 mmHg]). The time-dependent surface deformation is characterized by a viscoelastic tissue recovery response, quantified by an exponential decay constant-relaxation rate. Ex vivo rabbit globes (n = 10) with fixed intraocular pressure (15 mmHg) were topically instilled every 5 minutes with 0.9% saline for 60 minutes and 20% dextran for another 60 minutes. Measurements were made after every 20 minutes to determine the central corneal thickness (CCT) and the relaxation rates. Cross-linking treatment was performed on another 13 eyes, applying isotonic riboflavin (n = 6) and hypertonic riboflavin (n = 7) every 5 minutes for 30 minutes, followed by UV irradiation (365 nm, 3 mW/cm) for 30 minutes while instilling riboflavin. Central corneal thickness and relaxation rates were obtained before and after CXL treatment. RESULTS:Corneal thickness was positively correlated (R = 0.9) with relaxation rates. In the CXL-treated eyes, isotonic riboflavin did not affect CCT and showed a significant increase in relaxation rates (+10%; P = .01) from 2.29 ms to 2.53 ms. Hypertonic riboflavin showed a significant CCT decrease (-31%; P = .01) from 618 ?m to 429 ?m but showed little change in relaxation rates after CXL treatment. CONCLUSIONS:Corneal thickness and stiffness are correlated positively. A higher relaxation rate implied stiffer material properties after isotonic CXL treatment. Hypertonic CXL treatment results in a stiffness decrease that offsets the stiffness increase with CXL treatment.

Dataset Information

Corneal Biomechanical Properties after FS-LASIK with Residual Bed Thickness Less Than 50% of the Original Corneal Thickness.

Publications

Corneal Biomechanical Properties after FS-LASIK with Residual Bed Thickness Less Than 50% of the Original Corneal Thickness.

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