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Refractive Surgery and Binocularity
Published in Jan-Tjeerd de Faber, 28th European Strabismological Association Meeting, 2020
A. Dickmann, P. Valente, M.T. Rebecchi, G. Savino, A. Salerni, L. Buzzonetti
Two patients, showing a risk to develop a postoperative diplopia, were not treated. Eight patients (fourteen eyes) performed uncomplicated LASIK (Bausch & Lomb Technolas 217C excimer laser; Hansatome microkeratome). We planned monocular LASIK (the second eye treated two weeks after the first one).
Laser refractive surgery
Published in Pablo Artal, Handbook of Visual Optics, 2017
Jorge L. Alió, Mohamed El Bahrawy
Barraquer’s law of thicknesses in 1964 described the corneal flatness with central tissue removal and steepness with peripheral tissue removal.11 He then made trials of some other techniques to improve his methods as the keratophakia, which involves suturing a donor stromal disc under the initial cap, and then came the trials of Kaufman and Werblin in 1979, describing epikeratophakia, both aiming at overcoming the need to use the cryolathe, but the described techniques were reported to be neither predictable nor safe. Students of Barraquer raised the keratomileusis to its highest state of precision; the first was Swinger with the help of Krumeich, when they described the Barraquer–Krumeich–Swinger nonfreeze technique (Figure 15.3), a method of changing the shape of the cornea without freezing it, using a dye then a second pass of the microkeratome, with the aim of reducing surgical trauma and visual recovery time. The second was Luis Ruiz, who modified the principles of microkeratome by using an automated form called the automated lamellar keratoplasty (ALK), to correct high levels of myopia and hyperopia while avoiding irregular sections through a constant and reproducible speed of this automated microkeratome. It was Ruiz also who came up with the idea of passing the microkeratome a second time with the patient on table but with different suction setting, a procedure to be called in situ keratomileusis, and later demonstrated that by stopping the microkeratome before the end of the pass, it is possible to create a flap with a hinge that can be replaced again with no need for the previously required suture of the disc securing it with overnight patching.12
Lasers in Medicine: Healing with Light
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
Excimer lasers produce ultraviolet wavelengths that are absorbed well in general by water and proteins. This means their power can be absorbed by the transparent structures of the eye, allowing surgery on the lens and cornea. One of the newer uses of lasers involves sculpting the cornea to correct problems in vision. The most common example is myopia (or nearsightedness), in which a steeply curved cornea results in images being focused in front of, rather than on, the retina itself. In one form of this operation, called photorefractive keratectomy (PRK), an excimer laser is used to directly remove material from the surface of the cornea to flatten it out. A different technique, called LASIK (for laser-assisted in-situ keratomileusis), uses a thin knife called a microkeratome (or sometimes another laser) to slice a flap off the top of the cornea first, after which an excimer laser is used to reshape and flatten the cornea. The flap is replaced, and a flatter cornea overall results after healing. While these procedures are typically used to correct nearsightedness, in some cases they can also be used to correct for farsightedness due to an overly flat cornea. In wavefront-guided LASIK, the excimer laser is used to sculpt the cornea to attempt to correct subtler visual errors. While many have benefited greatly from PRK and LASIK, the utility of laser surgery for refractive corrections remains limited. Not everyone is a good candidate for LASIK, and ophthalmologists now assess potential recipients for various risk factors, such as a rapidly changing refractive error, overly thin corneas, and a tendency toward dry eyes. In a small percentage of cases, patients report serious side effects from LASIK, such as light sensitivity, glare, dry eyes, and problems with night vision.
Predicted and Measured Changes in Posterior Corneal Astigmatism after Uncomplicated Femtosecond Assisted LASIK (FsLASIK) and Microkeratome LASIK Correction for Myopia and Low Astigmatism
Published in Seminars in Ophthalmology, 2021
Maja Bohac, Alma Biscevic, Ivan Gabric, Kresimir Gabric, Violeta Shijakova, Sudi Patel
Changes at the posterior corneal surface do occur after LASIK, but these are small and of questionable importance.8–14 A preliminary investigation revealed inconsistencies between measured and estimated changes at the posterior corneal surface after LASIK when the flap was created with either a femtosecond laser (FsLASIK) or manual microkeratome. This anecdotal evidence suggests the changes observed at the anterior and posterior corneal surfaces within the central region of the cornea do not completely match the corresponding surgically induced change in astigmatism observed by refraction (SIAR). These discrepancies could be attributed to torsion at one corneal surface relative to the other alongside changes in other optical components of the cornea. On the other hand, the combined errors in measuring corneal surface powers and refraction could be the true source of such discrepancies. If any surgically induced changes of astigmatism at the posterior surface (SIABact) significantly contribute to any unexpected SIAR then, estimated changes at this surface (SIABest) should be supported by empirical evidence. The magnitude of SIABact and SIABest should exceed, or at least be comparable with, the repeatability of the clinical measurement of corneal astigmatism. Values of, and differences between, SIABact and SIABest less than the repeatability would be clinically irrelevant.
Long-term results of MyoRing implantation in patients with keratoconus
Published in Clinical and Experimental Optometry, 2021
Mostafa Naderi, Farshid Karimi, Khosrow Jadidi, Seyed Aliasghar Mosavi, Mohadeseh Ghobadi, Hossein Tireh, Masoud Khorrami-Nejad
The implants that were used in all eyes were the MyoRing (Dioptex, GmbH, Linz, Austria). The dimensions of the MyoRing were selected based on the theoretical and experimental model of corneal biomechanics.26,27 This pattern was measured based on the information from the average central corneal keratometry and the corneal thickness at its thinnest point.20 All surgeries were performed by two experienced surgeons (KJ and MN) with a single method and under local anaesthesia. After topical anaesthesia, a closed intracorneal pocket was created via a small incision tunnel in the temporal area with the self-sealing method by means of the Pocket Maker microkeratome (Dioptex, GmbH, Linz, Austria). A detailed description of the creation of the corneal pocket using a microkeratome was described by Daxer.7
Predictors of Myopic Regression for Laser-assisted Subepithelial Keratomileusis and Laser-assisted in Situ Keratomileusis Flap Creation with Mechanical Microkeratome and Femtosecond Laser in Low and Moderate Myopia
Published in Ophthalmic Epidemiology, 2020
Jihong Zhou, Yan Gao, Shaowei Li, Wei Gu, Lijuan Wu, Xiuhua Guo
These risk factors and mechanisms could guide the development of a better design for laser ablation to correct myopia and to instruct patients on the possibility of myopic regression in accordance with their status in each period, as well as the relative risks of the different flap-creating methods. We have been performing laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) with flaps created using a mechanical microkeratome (MM-LASIK) and LASIK with flaps created using a femtosecond (FS-LASIK) laser for several years. This has established a database of postoperative follow-ups for use in investigations of to investigate the predictors of myopic regression in these three groups. The aim of this study was therefore to compare the different results of myopic regression in patients who have undergone LASEK, FS-LASIK, and MM-LASIK surgeries to identify significant predictors and to prevent the risk of myopic regression during follow-up.