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Dolling M, Buhl L, Birngruber R, Hüttmann G, Schulz-Hildebrandt H. Algorithm and software for field distortion correction in a commercial SD-OCT for corneal curvature assessment. APPLIED OPTICS 2024; 63:2694-2703. [PMID: 38568554 DOI: 10.1364/ao.505107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 03/12/2024] [Indexed: 04/05/2024]
Abstract
Accurate assessment of corneal curvatures using frequency domain optical coherence tomography (OCT) with galvanometer scanners remains challenging due to the well-known scan field distortion. This paper presents an algorithm and software for correcting the distortion using only two simple measurements in which a readily available standard sphere is positioned in different depths in front of the OCT scanner. This offers a highly accessible and easily reproducible method for the field distortion correction (FDC). The correction was validated by measuring different spherical phantoms and conducting corneal curvature measurements of ex vivo porcine corneas using a commercial spectral-domain OCT system and a clinically approved swept-source OCT as a reference instrument. Thus, the error in radius measurements of spherical phantoms was reduced by >90% and astigmatism by >80% using FDC. In explanted porcine eyes, the error in astigmatism measurements with the Telesto was reduced by 75% for power and 70% for angle. The best fitting sphere radius was determined up to a deviation of 0.4% from the Anterion. This paper describes a correction algorithm for OCT immanent distortion that is applicable to any scanning OCT setup and enables precise corneal curvature measurements. The MATLAB software for the FDC is publicly available on GitHub.
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Freidank S, Vogel A, Linz N. Optical Vortex Beam for Gentle and Ultraprecise Intrastromal Corneal Dissection in Refractive Surgery. Transl Vis Sci Technol 2020; 9:22. [PMID: 33024615 PMCID: PMC7521178 DOI: 10.1167/tvst.9.10.22] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 08/20/2020] [Indexed: 11/24/2022] Open
Abstract
Purpose We introduce a novel focus shaping concept for intrastromal corneal dissection that facilitates cleavage along corneal lamellae, and we analyze laser-tissue interactions governing cutting effectiveness and mechanical side effects. Methods Focus shaping was achieved by a spiral phase plate that converts an incident Gaussian beam into a Laguerre-Gaussian beam with a helical phase. Such vortex beams have zero intensity at their center, are propagation invariant, and possess a ring focus equal in length to the Gaussian focus but with a larger diameter. Cutting precision and the required absorbed energy for flap dissection were compared for Gaussian and vortex beams on ex vivo porcine corneal specimens at pulse durations between 480 fs and 9 ps. Cutting quality and bubble formation were characterized by scanning electron microscopy and macro photography. Results With the vortex beam, the cuts were much smoother. Bubble formation was markedly reduced because cutting can be performed close to the bubble threshold, whereas with the Gaussian beam energies well above threshold are needed. Although the incident energy at the flap dissection threshold was slightly larger for the vortex beam, the absorbed energy was much smaller and contributed more effectively to cutting. This reduced plasma-induced pressure more than sevenfold. Conclusions The vortex beam approach for corneal dissection is a simple, versatile, and cost-effective way of improving the precision of refractive surgery while reducing bubble formation and pressure-related mechanical side effects. Translational Relevance Phase plates for propagation invariant vortex beams are easily implemented in the beam path of next-generation clinical devices.
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Affiliation(s)
| | - Alfred Vogel
- Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany
| | - Norbert Linz
- Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany
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Kassumeh S, Luther JK, Wertheimer CM, Brandt K, Schenk MS, Priglinger SG, Wartak A, Apiou-Sbirlea G, Anderson RR, Birngruber R. Corneal Stromal Filler Injection as a Novel Approach to Correct Presbyopia-An Ex Vivo Pilot Study. Transl Vis Sci Technol 2020; 9:30. [PMID: 32832235 PMCID: PMC7414620 DOI: 10.1167/tvst.9.7.30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Accepted: 05/10/2020] [Indexed: 11/24/2022] Open
Abstract
Purpose To evaluate the ex vivo feasibility of corneal stromal filler injection to create bifocality to correct presbyopia by flattening the central posterior corneal surface and thus increase refractive power. Methods Femtosecond laser-assisted corneal stromal pockets of varying diameters close to the posterior corneal curvature were cut into rabbit eyes ex vivo. Subsequently, hyaluronic acid was injected to flatten the central posterior curvature. Refractive parameters were determined using perioperatively acquired three-dimensional optical coherence tomography (OCT) scans. Using micrometer-resolution OCT, corneal endothelial cell morphology and density were evaluated. Results Following filler injection into the corneal stromal pockets, a fair volume-dependent increase of central refractive power up to 4 diopters (dpt) was observed. Unremarkable refractive changes of the peripheral posterior (3 mm, 0.20 ± 0.11 dpt; 2 mm, 0.11 ± 0.10 dpt) and the anterior corneal curvature (3 mm, 0.20 ± 0.34 dpt; 2 mm, 0.33 ± 0.31 dpt) occurred. Only negligible changes in astigmatism were observed. Different sizes of optical zones could be established. Furthermore, no alterations of corneal endothelial morphology or endothelial cell density (2831 ± 356 cells/mm2 vs. 2734 ± 292 cells/mm2; P = 0.552) due to the adjacent laser treatment were observed. Conclusions The ex vivo investigations proved the principle of injecting a filler material into femtosecond laser-created corneal stromal pockets close to the posterior corneal curvature as an efficacious, individually adjustable, and novel approach to correct presbyopia without ablating corneal tissue. Translational Relevance Due to the aging population worldwide, presbyopia is an increasing problem; thus, our study may encourage further exploration to extend the treatment spectrum of clinically used femtosecond laser systems to correct presbyopia.
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Affiliation(s)
- Stefan Kassumeh
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Department of Ophthalmology, University Hospital, LMU Munich, Munich, Germany
| | - Jannik K Luther
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany
| | | | - Katharina Brandt
- Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany
| | - Merle S Schenk
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Department of Ophthalmology, University Hospital, LMU Munich, Munich, Germany
| | | | - Andreas Wartak
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Gabriela Apiou-Sbirlea
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - R Rox Anderson
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Reginald Birngruber
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Institute of Biomedical Optics, University of Luebeck, Luebeck, Germany
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Wertheimer CM, Brandt K, Kaminsky S, Elhardt C, Kassumeh SA, Pham L, Schulz-Hildebrandt H, Priglinger S, Anderson RR, Birngruber R. Refractive Changes After Corneal Stromal Filler Injection for the Correction of Hyperopia. J Refract Surg 2020; 36:406-413. [DOI: 10.3928/1081597x-20200429-01] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 04/29/2020] [Indexed: 11/20/2022]
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