Toward Cold-Light CAIRS: Ultraviolet Laser Engraving for Thermally Neutral Preparation of Corneal Allogenic Intrastromal Ring Segments – An Ex Vivo Proof-of-Concept

Toward Cold-Light CAIRS: Ultraviolet Laser Engraving for Thermally Neutral Preparation of Corneal Allogenic Intrastromal Ring Segments – An Ex Vivo Proof-of-Concept | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Short Report Toward Cold-Light CAIRS: Ultraviolet Laser Engraving for Thermally Neutral Preparation of Corneal Allogenic Intrastromal Ring Segments – An Ex Vivo Proof-of-Concept Omar Alabbasi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7895925/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Building on our previously published diode engraving laser method for low-cost preparation of corneal allogenic intrastromal ring segments (CAIRS), we introduce a next-generation approach employing an ultraviolet (UV) laser for “cold-light” photoablation of donor corneal tissue applicable not only to CAIRS fabrication but also to lamellar keratoplasty. Unlike continuous-wave visible diode lasers that generate a narrow peripheral thermal rim, short-wavelength UV irradiation enables precise stromal dissection through predominantly photochemical mechanisms with minimal heat diffusion. CAIRS ultraviolet laser cold-light photoablation lamellar keratoplasty corneal surgery Introduction Corneal allogenic intrastromal ring segments (CAIRS) have emerged as a biocompatible alternative to synthetic polymethylmethacrylate (PMMA) rings for the management of keratoconus and ectatic disorders.[ 1 ] Lamellar keratoplasty remains essential for advanced cases requiring selective stromal replacement. .[ 2 ] This communication extends our diode-based approach with UV cold-light engraving, preserving full stromal architecture. [ 4 ] Methods Donor tissue and preparation Human donor corneal buttons unsuitable for optical transplantation were obtained from the local eye bank, stored in Optisol-GS, and equilibrated to room temperature. Epithelium and Descemet’s membrane were gently removed to expose the stromal bed. Tissue dehydration (~ 10–15 minutes) was performed to facilitate laser penetration and handling, following our prior diode-laser protocol. [ 4 ] Laser setup and procedure A digitally guided ultraviolet laser system (wavelength 355 nm, pulsed nanosecond regime) was configured to deliver line-by-line surface engraving with adjustable arc geometry, depth, and width. The laser head was mounted at a fixed working distance. Energy and dwell time were kept below corneal photocoagulation thresholds to achieve photoablative cold dissection. Segment designs were programmed to yield inner diameters of 6.5 mm, outer diameters of 8.0 mm, and 1.0 mm width. Stromal rings were then bisected to form semicircular CAIRS segments. The process was fully computer-guided and completed within 10–15 seconds per pass. Similarly, for lamellar keratoplasty applications, circular stromal discs with a target diameter of approximately 8.0 mm were trephined using the same UV cold-light photoablation workflow, allowing precise depth-controlled dissection while preserving collagen lamellar architecture without thermal collateral effects. Imaging and analysis Gross examination under oblique illumination evaluated edge sharpness and any evidence of discoloration or charring. Comparative evaluation Findings were compared qualitatively to previously reported diode engraving results (LaserPecker 450 nm, continuous-wave). [ 4 ] No live or clinical implantation was performed in this preliminary stage. Results UV laser engraving successfully generated uniform stromal ring segments from all donor corneas without mechanical tearing or edge irregularities. no evidence of subsurface heat-induced coagulation zones. In contrast to the mild brown discoloration occasionally observed at the margins of blue-diode laser cuts, the UV-engraved segments showed no visible pigmentation or tissue shrinkage. The engraved edges maintained a translucent appearance with sharply preserved lamellar structure. The workflow was comparable to the diode method in setup and duration, yet achieving cleaner tissue margins. Segments were semi-rigid and easily handled following mild air-drying. Discussion In addition to its application in CAIRS, the UV cold-light engraving approach holds strong potential for precise lamellar keratoplasty, where thermally neutral stromal dissection and preservation of collagen architecture are essential. [ 1 , 3 ] Conclusion This technique not only advances CAIRS fabrication but may also be adapted as a low-cost, cold-light platform for lamellar keratoplasty, offering highly controlled stromal layer separation with minimal thermal damage. Declarations Funding Declaration No funding was received for this work. Conflict of Interest The authors declare no conflicts of interest related to this work. Ethical Approval This ex vivo study utilized human donor corneal tissue obtained from an accredited eye bank under standard consent protocols for research use. No live human or animal subjects were involved. Author Contribution The main author developed the UV laser concept and drafted and revised the manuscript References Jacob S, Agarwal A et al (2018) Corneal allogenic intrastromal ring segments (CAIRS) combined with cross-linking for keratoconus. J Refract Surg 34:296–303 Parker JS, Dockery PW et al (2021) Manual method for CAIRS implantation. J Cataract Refract Surg 47:e31–e33 Levy I, Mukhija R, Nanavaty MA (2025) Corneal allogenic intrastromal ring segments: review. J Clin Med 14:1340 Alabbasi OM, AlBalawi HB (2025) Novel application of diode engraving laser for preparing corneal allogenic intrastromal ring segments: a comparative study with femtosecond laser and manual trephine. Lasers Med Sci 40:438 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7895925","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Short Report","associatedPublications":[],"authors":[{"id":575819044,"identity":"4585c3f4-ba74-4621-91f4-4e580c1417c0","order_by":0,"name":"Omar Alabbasi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYLCCBB4JOX4JMFNChjgtD2RsjCVnMDA2ALXwEKWD8YFNWuKGG2AtDIS1GFw7/IAhIedw4ubbzccf3aix4GFgP3x0A14tt9MMGBLOHDbedudYYnPOMaDDeNLSbuDXkmD+I7HnsOy2GzmGzTlsQC0SPGYEtKR/YEj8d5hx8wyQln9EackBOownTXGDBFBLbhsRWiRv5xQAtdgYS9xIS5yd2yfBw0bIL3y30zcw/gBF5YzkA59zvtXJ8bMfPoZXCyZgI035KBgFo2AUjAJsAAABJEmEYrxHXQAAAABJRU5ErkJggg==","orcid":"","institution":"King Salman Bin Abdulaziz Medical City, Saudi Arabia","correspondingAuthor":true,"prefix":"","firstName":"Omar","middleName":"","lastName":"Alabbasi","suffix":""}],"badges":[],"createdAt":"2025-10-19 01:53:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7895925/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7895925/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":100601716,"identity":"816b83be-3735-4925-b585-e85427927fd3","added_by":"auto","created_at":"2026-01-19 15:07:08","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":30455,"visible":true,"origin":"","legend":"","description":"","filename":"manuscriptOM1.docx","url":"https://assets-eu.researchsquare.com/files/rs-7895925/v1/590c4f43d659c8361064d5f1.docx"},{"id":100601675,"identity":"117b53cc-1b85-40e7-b068-a5ce9f3186a7","added_by":"auto","created_at":"2026-01-19 15:06:32","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":3327,"visible":true,"origin":"","legend":"","description":"","filename":"826f698fc3c142308cbc1e4584a5fbbd.json","url":"https://assets-eu.researchsquare.com/files/rs-7895925/v1/17b85964c6178e0c18cb75b8.json"},{"id":100601765,"identity":"e5ffd0c3-f421-4ea3-8160-a34a2d3fa0b7","added_by":"auto","created_at":"2026-01-19 15:08:13","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":12154,"visible":true,"origin":"","legend":"","description":"","filename":"826f698fc3c142308cbc1e4584a5fbbd1enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7895925/v1/226f6b6bd2cc771280c406a1.xml"},{"id":100601719,"identity":"552afa85-0d34-401d-9ae6-29c32d05b997","added_by":"auto","created_at":"2026-01-19 15:07:10","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11481,"visible":true,"origin":"","legend":"","description":"","filename":"826f698fc3c142308cbc1e4584a5fbbd1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7895925/v1/cba81387767fff0b682a0ff1.xml"},{"id":100601697,"identity":"de72ccb5-be13-4f03-b7a5-a3bfb129a51f","added_by":"auto","created_at":"2026-01-19 15:06:51","extension":"html","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":14309,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7895925/v1/7481935d094598ffcbfe8e67.html"},{"id":101399788,"identity":"13b78b8f-3ef8-4bc0-be67-87e15e00c292","added_by":"auto","created_at":"2026-01-29 09:55:05","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":248252,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7895925/v1/7b5fe46e-abf2-4cf7-a571-4b82720c0052.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Toward Cold-Light CAIRS: Ultraviolet Laser Engraving for Thermally Neutral Preparation of Corneal Allogenic Intrastromal Ring Segments – An Ex Vivo Proof-of-Concept","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCorneal allogenic intrastromal ring segments (CAIRS) have emerged as a biocompatible alternative to synthetic polymethylmethacrylate (PMMA) rings for the management of keratoconus and ectatic disorders.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] Lamellar keratoplasty remains essential for advanced cases requiring selective stromal replacement. .[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] This communication extends our diode-based approach with UV cold-light engraving, preserving full stromal architecture. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003eDonor tissue and preparation\u003c/p\u003e \u003cp\u003eHuman donor corneal buttons unsuitable for optical transplantation were obtained from the local eye bank, stored in Optisol-GS, and equilibrated to room temperature. Epithelium and Descemet\u0026rsquo;s membrane were gently removed to expose the stromal bed. Tissue dehydration (~\u0026thinsp;10\u0026ndash;15 minutes) was performed to facilitate laser penetration and handling, following our prior diode-laser protocol. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eLaser setup and procedure\u003c/p\u003e \u003cp\u003eA digitally guided ultraviolet laser system (wavelength 355 nm, pulsed nanosecond regime) was configured to deliver line-by-line surface engraving with adjustable arc geometry, depth, and width. The laser head was mounted at a fixed working distance. Energy and dwell time were kept below corneal photocoagulation thresholds to achieve photoablative cold dissection.\u003c/p\u003e \u003cp\u003eSegment designs were programmed to yield inner diameters of 6.5 mm, outer diameters of 8.0 mm, and 1.0 mm width. Stromal rings were then bisected to form semicircular CAIRS segments. The process was fully computer-guided and completed within 10\u0026ndash;15 seconds per pass. Similarly, for lamellar keratoplasty applications, circular stromal discs with a target diameter of approximately 8.0 mm were trephined using the same UV cold-light photoablation workflow, allowing precise depth-controlled dissection while preserving collagen lamellar architecture without thermal collateral effects.\u003c/p\u003e \u003cp\u003eImaging and analysis\u003c/p\u003e \u003cp\u003eGross examination under oblique illumination evaluated edge sharpness and any evidence of discoloration or charring.\u003c/p\u003e \u003cp\u003eComparative evaluation\u003c/p\u003e \u003cp\u003eFindings were compared qualitatively to previously reported diode engraving results (LaserPecker 450 nm, continuous-wave). [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] No live or clinical implantation was performed in this preliminary stage.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eUV laser engraving successfully generated uniform stromal ring segments from all donor corneas without mechanical tearing or edge irregularities. no evidence of subsurface heat-induced coagulation zones.\u003c/p\u003e \u003cp\u003eIn contrast to the mild brown discoloration occasionally observed at the margins of blue-diode laser cuts, the UV-engraved segments showed no visible pigmentation or tissue shrinkage. The engraved edges maintained a translucent appearance with sharply preserved lamellar structure.\u003c/p\u003e \u003cp\u003eThe workflow was comparable to the diode method in setup and duration, yet achieving cleaner tissue margins. Segments were semi-rigid and easily handled following mild air-drying.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn addition to its application in CAIRS, the UV cold-light engraving approach holds strong potential for precise lamellar keratoplasty, where thermally neutral stromal dissection and preservation of collagen architecture are essential. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis technique not only advances CAIRS fabrication but may also be adapted as a low-cost, cold-light platform for lamellar keratoplasty, offering highly controlled stromal layer separation with minimal thermal damage.\u003c/p\u003e "},{"header":"Declarations","content":"\u003ch2\u003eFunding Declaration\u003c/h2\u003e\n\u003cp\u003eNo funding was received for this work.\u003c/p\u003e\n\u003ch2\u003eConflict of Interest\u003c/h2\u003e\n\u003cp\u003eThe authors declare no conflicts of interest related to this work.\u003c/p\u003e\n\u003ch2\u003eEthical Approval\u003c/h2\u003e\n\u003cp\u003eThis ex vivo study utilized human donor corneal tissue obtained from an accredited eye bank under standard consent protocols for research use. No live human or animal subjects were involved.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe main author developed the UV laser concept and drafted and revised the manuscript\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJacob S, Agarwal A et al (2018) Corneal allogenic intrastromal ring segments (CAIRS) combined with cross-linking for keratoconus. J Refract Surg 34:296\u0026ndash;303\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParker JS, Dockery PW et al (2021) Manual method for CAIRS implantation. J Cataract Refract Surg 47:e31\u0026ndash;e33\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLevy I, Mukhija R, Nanavaty MA (2025) Corneal allogenic intrastromal ring segments: review. J Clin Med 14:1340\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlabbasi OM, AlBalawi HB (2025) Novel application of diode engraving laser for preparing corneal allogenic intrastromal ring segments: a comparative study with femtosecond laser and manual trephine. Lasers Med Sci 40:438\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"CAIRS, ultraviolet laser, cold-light photoablation, lamellar keratoplasty, corneal surgery","lastPublishedDoi":"10.21203/rs.3.rs-7895925/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7895925/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBuilding on our previously published diode engraving laser method for low-cost preparation of corneal allogenic intrastromal ring segments (CAIRS), we introduce a next-generation approach employing an ultraviolet (UV) laser for “cold-light” photoablation of donor corneal tissue applicable not only to CAIRS fabrication but also to lamellar keratoplasty. 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