AIMS: To investigate the concordance between the corneal power determined by various approaches with two tomographers (MS-39® and Galilei G6®) and the clinical history method (CHM) in patients undergoing photorefractive surgery with excimer laser for myopic errors. MATERIAL AND METHODS: Prospective cohort study. Patients undergoing keratorefractive surgery, and having pre- and postoperative keratometries, and tomographies, were included. RESULTS: In 90 eyes, the differences in the power estimated by the CHM and the one determined by four approaches with the corneal tomographers, which included measurements of the posterior cornea, did not show statistically significant differences in their averages. However, the 95% limits of agreement were very wide. After obtaining regression formulas to adjust the values of these four variables, the results of the agreement analysis were similar. CONCLUSION: Although certain values either directly determined or derived from measurements with the Galilei® and MS-39®corneal tomographers, approximated the estimated value of postoperative corneal power according to the CHM, due to the amplitude of their limits of agreement, these calculations must be taken with care, because they may not be accurate in a given eye.
- Klíčová slova
- corneal power, corneal tomography, clinical history method, refractive surgery,
- MeSH
- dospělí MeSH
- fotorefrakční keratektomie MeSH
- lasery excimerové terapeutické užití MeSH
- lidé MeSH
- mladý dospělý MeSH
- myopie * chirurgie patofyziologie diagnostické zobrazování MeSH
- prospektivní studie MeSH
- refrakce oka MeSH
- rohovka * diagnostické zobrazování chirurgie patologie patofyziologie MeSH
- rohovková topografie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Refractive surgery with excimer laser has been a very common surgical procedure worldwide during the last decades. Currently, patients who underwent refractive surgery years ago are older, with a growing number of them now needing cataract surgery. To establish the power of the intraocular lens to be implanted in these patients, it is essential to define the true corneal power. However, since the refractive surgery modified the anterior, but not the posterior surface of the cornea, the determination of the corneal power in this group of patients is challenging. This article reviews the different sources of error in finding the true corneal power in these cases, and comments on several approaches, including the clinical history method as described originally by Holladay, and a modified version of it, as well as new alternatives based on corneal tomography, using devices that are able to measure the actual anterior and posterior corneal curvatures, which have emerged in recent years to address this issue.
- Klíčová slova
- corneal power, Refractive surgery, clinical history method, corneal tomography, refractive surgery,
- MeSH
- laserová modelace rohovky pod rohovkovou lamelou * MeSH
- lasery excimerové * terapeutické užití MeSH
- lidé MeSH
- refrakce oka MeSH
- rohovka chirurgie MeSH
- rohovková topografie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
PURPOSE: To evaluate changes in corneal refractive parameters after implantation of a stromal lenticule of different thickness. We assume that the refractive outcome depends on the optical power of the used lenticule. METHODS: We conducted an ex-vivo non-human study on 33 normotonic porcine eyeballs divided into two groups, for 4D and 8D human lenticule implantation. Corneal stromal lenticules were obtained as a by-product from a laser procedure ReLEx SMILE. We evaluated corneal refractive parameters measured on Oculus Pentacam© device before and immediately after the intrastromal lenticule implantation. RESULTS: There was no statistically significant difference in corneal refractive parameters between the eyeball groups before lenticule implantation. In both groups, the intrastromal implantation in the depth of 300um led to a significant increase of central corneal pachymetry and corneal anterior steepening. In the 4D group the average central corneal pachymetry increased from 903 ± 124.59 to 1230 ± 148.99 (p = 0.0022) and in 8D group from 733.35 ± 69.60 to 1109 ± 161.64 (p = 0.0008). Induced changes in other studied parameters were not statistically significant, Kmax changed from 45.57 ± 2.78 to 72.07 ± 16.83 (p = 0.0094) and Km front from 40.72 ± 1.60 to 48.87 ± 5.83 (p = 0.0037) in 4D group and in the 8D group average Kmax increased from 42.22 ± 1.54 to 62.95 ± 12.67 (p = 0.0001) and K2 front 40.46 ± 1.64 to 51.51 ± 9.63 (p = 0.0037). There were no significant differences in refractive changes between the 4D and 8D groups after lenticule implantation. CONCLUSION: Intrastromal corneal lenticule implantation induces changes in corneal refractive parameters. In both groups, the implantation induced a significant increase of an anterior corneal steepening without any significant influence on posterior corneal flattening. Corneal lenticule implantation did not lead to any significant change of corneal astigmatism. However, in order to have more precise data for future clinical applications we need to continue with the experiments and verify the results on human corneas.
- Klíčová slova
- Corneal lenticule implantation, corneal topography after lenticule implantation, ex-vivo corneal lenticule implantation,
- MeSH
- laserová chirurgie rohovky * metody MeSH
- lasery excimerové terapeutické užití MeSH
- lidé MeSH
- nemoci rohovky * MeSH
- prasata MeSH
- refrakce oka MeSH
- rohovka MeSH
- rohovková topografie MeSH
- stroma rohovky chirurgie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Excimer laser refractive surgery is a procedure performed worldwide to solve refractive errors and reduce dependence on glasses or contact lenses. There has been an increase in the number of procedures performed around the world. Myopia is the most common indication for corneal photorefractive surgery. Myopic patients have a higher risk of developing some type of glaucoma in their lifetime, such as primary open-angle glaucoma and others. Refractive surgery ablates central corneal stromal tissue, altering its thickness and biomechanics, which in turn makes it difficult to accurately measure intraocular pressure (IOP), since it underestimates it. This underestimation of IOP may delay the diagnosis of de novo glaucoma in patients with a history of refractive surgery. Each patient who wishes to undergo corneal refractive surgery should undergo a thorough glaucoma examination in order to monitor and detect the possible development and / or progression of glaucoma. A very useful practical approach is to perform a series of IOP measurements before and after surgery, when the eye is already stable, and the difference between the averages of the two sets of readings can then be used as a personalised correction factor for postoperative IOP monitoring in that eye. Also, if there is any suspicion of a possible glaucoma, paraclinical tests, such as coherent optical tomography of the retinal nerve fibre layer (RNFL), visual fields and photos of the optic nerve should be requested. All this data prior to refractive surgery should be provided to these patients, so that they can save it and give it to their treating ophthalmologists in the future.
- Klíčová slova
- LASIK, SMILE, excimer laser, glaucoma, refractive surgery,
- MeSH
- glaukom s otevřeným úhlem * MeSH
- glaukom * MeSH
- laserová modelace rohovky pod rohovkovou lamelou * MeSH
- lasery excimerové terapeutické užití MeSH
- lidé MeSH
- následné studie MeSH
- nitrooční tlak MeSH
- refrakční chirurgické výkony * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
PURPOSE: To analyze and compare visual acuity, refractive outcomes and higher-order aberrations after standard and wavefront-guided Femto-LASIK at 1, 3, and 12 months postoperatively. METHODS: Study of 95 consecutive eyes of myopic patients (-0.5 to -7.0 D), who underwent Femto-LASIK with standard ablation profile (STA) (49 eyes) or wavefront-guided ablation (WFG) (46 eyes) using femtosecond laser LDV Ziemer and excimer laser MEL 80 Zeiss with iris registration. Primary outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction and higher-order ocular aberrations (HOAs). HOAs were measured with Hartmann-Shack wavefront aberrometer WASCA, HOAs analyzed at 6 mm pupil, assessed total HOAs root mean square (RMS HOAs) and individual Zernike coefficients. RESULTS: Preoperatively, there were no significant differences between STA and WFG groups in UDVA, CDVA, manifest refraction or HOAs. As compared with preoperative values, spherical aberration Z(4,0) increased by 0.24 µm in both groups and it is the main increasing factor of RMS HOAs (0.05 µm in STA group and 0.08 µm in WFG group). Safety and efficacy index is 1.0 in both ablation profiles. Postoperatively, median UDVA and CDVA achieved 1.2. No patient lost line of CDVA at 12 month postoperatively. All patients were within ± 0,5 D of emmetropia at 12 months. Significant differences were not found between STA and WFG in UDVA, CDVA, manifest refraction or HOAs at 1, 3 and 12 month. CONCLUSIONS: Both wavefront-guided and standard Femto-LASIK with LDV and MEL 80 platform have shown very good efficacy and safety. Myopic Femto-LASIK only slightly increases RMS HOAs, especially by induction of spherical aberration. Both methods have equivalent postoperative aberration score one year postoperatively.Key words: femtosecond LASIK, higher-order aberrations, wavefront-guided, visual accuity.
- MeSH
- časové faktory MeSH
- laserová modelace rohovky pod rohovkovou lamelou metody MeSH
- lasery excimerové terapeutické užití MeSH
- lidé MeSH
- myopie patofyziologie chirurgie MeSH
- následné studie MeSH
- pooperační komplikace * MeSH
- refrakce oka MeSH
- rohovkové aberace diagnóza etiologie patofyziologie MeSH
- výsledek terapie MeSH
- zraková ostrost * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
