Intrastromal Corneal Ring Segment in Moderate to Severe Keratoconus: Refractive, Topographic and Aberrometric Changes

In as omal Co neal Ring Segmen in Mode a e o Se e e Ke a oconus: Re ac i e, Topog aphic and Abe ome ic Changes Ja ie González-Pé ez1*, Jacobo Ga cía Quei uga1, Rosa io Tou iño Pe alba2, Lau a Ma ínez-Pé ez2 and Mª Te esa Rod íguez A es2,3 1Depa men o Applied Physics (Op ome y), Uni e si y o San iago de Compos ela, Spain 2Oph halmology Se ice, Uni e si y Hospi al Complex o San iago de Compos ela, Spain 3Depa men o Su ge y (Oph halmology), Uni e si y o San iago de Compos ela, Spain In oduc ion Ke a oconus (KC) is a common, p og essi e co neal disease esul ing in ch onic hinning and p o usion o he pa a-cen al co nea associa ed wi h myopia, i egula as igma ism and high o de abe a ion inc ease [1]. The ea men di e s depending on he s age o he diso de . Visual acui y can be imp o ed wi h spec acles in he ea ly s age o his condi ion o wea ing con ac lenses also e ec i e o p o ide a good ision in mode a e KC [2]. When an op ical co ec ion is no longe e ec i e, o no con ac lenses a e well ole a ed, se e al su gical ea men s a e used o he ea men o KC, including In aco neal Co neal Ring Segmen s (ICRS) and co neal collagen c oss-linking (CXL) [3,4]. Howe e , KC may e en ually equi e co neal g a ing as hei se e e condi ion p og esses, ep esen ing he mos common indica ion o ke a oplas y in he de eloped wo ld [4]. Nowadays, he e is a g owing in e es in ea men op ions ha may delay o de e co neal g a ing, including ICRS implan a ion, o iginally used o co ec mode a e- o-se e e myopia, by exe ion o a e-modelling e ec C imson Publishe s Wings o he Resea ch Resea ch A icle *Co esponding au ho : Ja ie González- Pé ez, Depa men o Applied Physics (Op ome y), Uni e si y o San iago de Compos ela, Spain Submission: No embe 11, 2023 Published: Janua y 29, 2024 Volume 3 - Issue 3 How o ci e his a icle: Ja ie González- Pé ez*, Jacobo Ga cía Quei uga, Rosa io Tou iño Pe alba, Lau a Ma ínez- Pé ez and Mª Te esa Rod íguez A es. In as omal Co neal Ring Segmen in Mode a e o Se e e Ke a oconus: Re ac i e, Topog aphic and Abe ome ic Changes. Med Su g Oph hal Res. 3(3). MSOR. 000565. 2024. DOI: 10.31031/MSOR.2024.03.000565 Copy igh @ Ja ie González-Pé ez, This a icle is dis ibu ed unde he e ms o he C ea i e Commons A ibu ion 4.0 In e na ional License, which pe mi s un es ic ed use and edis ibu ion p o ided ha he o iginal au ho and sou ce a e c edi ed. ISSN : 2578-0360 1 Medical & Su gical Oph halmology Resea ch Abs ac Aim: This s udy e alua es he opog aphic and abe ome ic changes induced by ICRS in pa ien s wi h mode a e and se e e ke a oconus and analyzes p e-ope a i e ac o s a ec ing he e ac i e and isual ou comes. Me hods: This e ospec i e, obse a ional, non andomized, and single-cen e case se ies, included 21 ke a oconic eyes o 21 pa ien s implan ed wi h Ke a ing ICRS (Mediphacos, Belo Ho izon e, B azil), using he manual unneliza ion echnique and acuum de ice. All subjec s we e examined a e 6 mon hs ollowing su ge y, including he measu emen o unco ec ed isual acui y (UCVA), bes -Co ec ed Dis ance Visual Acui y (CDVA), e ac i e da a, pachyme y, co neal opog aphy, and abe ome y. Resul s: The mean age o 21 pa ien s was 31.14±10.65 yea s, ele en (52%) we e male. Ke a ings we e success ully implan ed in all eyes. A e 6-mon h om implan a ion, signi ican inc ease was ound in mean UCVA (P<0.01) and CDVA (P<0.01). The e was a s a is ically signi ican educ ion in e ac i e cylinde (P<0.01), co neal cylinde (P=0.020), Kmax (P<0.01) and BFS (P=0.02). S a is ically signi ican di e ences we e ound in se e al abe ome ic pa ame e s o 6-mm pupil, RMS HOA (P=0.045), oblique as igma ism (P=0.009), e ical coma (P=0.02), and oblique e oil (P=0.018). Conclusion: Analysis o he isual ou comes a e Ke a ing ICRS implan a ion showed a signi ican pos ope a i e co neal la ening wi h a subsequen inc ease in UCVA and CDVA. Visual, e ac i e, opog aphic and abe ome ic pa ame e s ema kably change in he 6-mon h pe iod a e Ke a ings implan a ion. Ke a ings in his sample ha e shown o p o ide a mild isual ehabili a ion be ween 2 and 3 lines, pa icula ly in mo e ad anced cases. Fu he mo e, la ening o he an e io segmen induced by he su ge y migh be bene icial o con ac lens i ing. Keywo ds: Ke a oconus; In as omal co neal ing segmen s; Ke a ing; Vacuum sys em; K as igma ism; Sphe ical abe a ion; Coma; Co neal hickness 2 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 on he co neal s oma [5-7]. The implan a ion means he addi ion o ex a ma e ial a he mid-pe iphe al co nea and subsequen ly educing s eepening o he cen al a ea. This e-modelling is in ended o dec ease e ac i e e o magni ude, imp o e cen al co neal su ace egula i y and, mo eo e , o inc ease co neal s abili y and delay he p og ession o KC [8]. I has been epo ed ha changes in he co neal s oma induced by ICRS a e di ec ly p opo ional o he hickness and in e sely p opo ional o i s diame e and dep h o implan a ion [9,10]. The e a e se e al comme cially a ailable ICRS ha di e in hei sec ion shape, diame e , a c leng h, hickness, and zone o implan a ion. The Ke a ing ICRS (Mediphacos, Belo Ho izon e, B azil), is a small, a c-like segmen made o polyme hyl me hac yla e cha ac e ized by a 5 o 6mm diame e and unique p isma ic design a ailable in di e en a c leng hs (90º, 120º,160º,210º and 355º), wi h a iable hickness anging om 150 o 350mm (in 50mm inc emen s). In he las 10 yea s, se e al clinical s udies ha e a emp ed o demons a e hei e icacy o imp o e isual unc ion, educing he magni ude o co neal as igma ism, and la ening he cen al co nea [11-14]. I has been p oposed ha he p eope a i e mani es e ac ion o bes co ec ed isual acui y a e p edic i e ac o s wi h a limi ed abili y o p edic he pos ope a i e isual ou come, while abe ome y has been ound o ha e a be e p edic i e po en ial [15]. The assessmen o isual and mo phological ea u es should p o ide aluable insigh s in o he de e minan s o he co ela ion be ween co neal su ace p ope ies and he imp o emen o isual acui y ollowing ICRS su ge y. Al hough his subjec has al eady been s udied, he e is s ill a lack o publica ions conce ning he mo phome ic and isual ou comes a e Ke a ing ICRS implan a ion using he manual echnique, especially in he ecen pe iod. Despi e new app oaches using he inc easingly equen em osecond echniques, hose a e no a ailable o many su geons a ound he wo ld. In addi ion, he e is s ill a lack o in o ma ion conce ning he ou comes on se e e ke a oconus pa ien s. The aim o his s udy was o con ibu e o de e mine how ICRS su ge y a ec o mo phome ic co neal pa ame e s and iden i y ac o s a ec ing he opog aphic and isual ou comes ollowing Ke a ing ICRS implan a ion in a no h- wes o Spain sample. Subjec s and Me hods To e alua e he impac and implica ions o ICRS implan a ion on he co neal su ace, we conduc ed a e ospec i e, obse a ional, non andomized, and single-cen e case se ies o pa ien s implan ed wi h Ke a ing segmen s (Mediphacos, Belo Ho izon e, B azil) using he manual echnique. Sample and inclusion c i e ia The s udy was conduc ed a he An e io Segmen Uni om Hospi al de Conxo-Complejo Hospi ala io de San iago de Compos ela (A Co uña, Spain), and comp ises a o al o 21 mode a e and se e e KC subjec s acco ding o he Amsle -K umeich classi ica ion, aged 31.14±10.65 yea s. The s udy p o ocol was app o ed by he E hic and Scien i ic Commi ees o he Uni e si y o San iago de Compos ela (Spain) and ollowed he ene s o he Decla a ion o Helsinki. Eligibili y c i e ia included KC subjec s, 18 yea s o age o olde , showing educed spec acle/con ac lens bes co ec ed dis ance isual acui y o con ac lens in ole ance and maximum co neal powe (Kmax) be ween 49 o 70 D. Diagnosis and g ading o he disease was based on co neal opog aphy and sli lamp examina ion. Ocula assessmen All pa ien s unde wen a comple e p eope a i e examina ion, including ou ine e alua ion o Snellen Unco ec ed Dis ance Visual Acui y (UDVA), Snellen Bes -Co ec ed Dis ance Visual Acui y (CDVA), e ac i e e o , undus examina ion, sli lamp biomic oscopy, co neal opog aphy and pachime y wi h pa icula a en ion o he occu ence o ocula ad e se e en s. Topog aphic analysis was pe o med using Pen acam (Oculus GmbH, We zla , Ge many), which include 3mm-a ea ke a ome ic eadings, co neal as igma ism, kmax, eccen ici y, co neal hickness (minimum, apex and cen al), and se e al abe ome ic pa ame e s. The same p o ocol was applied p eope a i e and 6-mon hs a e ICRS implan a ion. Su ge y and pos ope a i e p ocedu es All su ge ies we e pe o med by he same su geon unde s e ile condi ions wi h opical anes hesia 0.5% p opa acaine hyd ochlo ide solu ion (Alcaine, Alcon). The app op ia e Ke a ing segmen s diame e (6-mm diame e ), hickness and leng h (deg ees) we e selec ed in acco dance wi h nomog am p oposed by he manu ac u es, and hen implan ed in o he eye. The incisions we e always made in he s eepes co neal me idian. Co neal unneliza ion o ing segmen inse ion was pe o med by mechanical echnique dissec ion and a Ke a ing acuum de ice (Mediphacos, Belo Ho izon e, B azil) was employed o s abilize he globe and o keep he plane o dissec ion o he unnel by suc ion. A e ma king he geome ical cen e o he co nea, a 1.2mm adial incision was pe o med using a calib a ed diamond blade (Sinskey hook), a he dep h o 80% co neal hickness a he s eepes me idian. An in as omal pocke was c ea ed using a small incision wi h a semici cula mic o-dissec o ha ope a es unde suc ion, un il inishing he unnels in he desi ed di ec ions (clockwise and coun e clockwise dissec ion) and 6mm in diame e . Once his s ep was comple ed, he su geon emo es he suc ion and he Ke a ing implan was placed in o he pocke using implan a ion o ceps. The pocke was sel -sealing and did no equi e su u ing. Subsequen ly, a Pu eVision silicone hyd ogel bandage con ac lens (Bausch & Lomb) was placed on he co nea and hen emo ed 1 day a e he su ge y. No in aope a i e complica ions occu ed. Pos ope a i e ea men comp ised be ame hasone d ops ou imes a day, opical ob amycin 0.3% (Tob ex, Alcon) ou imes a day, and p ese a i e- ee a i icial ea s (A elac Rebalance, Bausch & Lomb, Inc., No h B idgewa e , NJ, USA) six imes a day. The ob amycin d ops we e discon inued 1 week a e he su ge y, while he be ame hasone dosage was ape ed o e a pe iod o 4 o 6 weeks. Da a Analysis The Shapi o-Wilk no mali y es was implemen ed o assess all da a se s o no mal dis ibu ion. The ca ego ical a iables (sex and 3 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 numbe o igh and le eyes) a e exp essed as equencies. The con inuous a iables (age and he p e- and pos ope a i e UDVA, CDVA, sphe e, cylinde , sphe ical equi alen , K1, K2, Kmean, Kmax, co neal pachome y and abe ome ic measu emen s) a e exp essed as means wi h S anda d De ia ions (SD) o easie compa isons and in e p e a ion wi h he exis ing li e a u e. The di e ences be ween he p eope a i e and pos ope a i e measu emen s we e compa ed using pai ed - es s when pa ame ic s a is ical analysis was possible, and he Wilcoxon Signed anks es o non-pa ame ic e alua ion. Pea son o Spea man co ela ion coe icien s we e used o e alua e co ela ion be ween di e en a iables, depending on whe he no mal dis ibu ions o da a we e obse ed. Fo s a is ical pu poses, P alue less han 0.05 was conside ed s a is ically signi ican . SPSS .24.0.0.0 (IBM Co po a ion, A monk NY) and Excel .15.0 (Mic oso Co po a ion, Redmond WA) so wa e we e used o all s a is ical analysis and g aphs. Resul s Visual and e ac i e pa ame e s A summa y o he isual and e ac i e changes in eyes implan ed wi h ke a ing segmen s a e shown in Table 1. Bo h, mean UDVA and CDVA we e signi ican ly inc eased ollowing 6-mon hs a e ICRS implan a ion. Mean p eope a i e sphe e, co neal cylinde and mani es sphe ical equi alen we e signi ican ly dec eased a 6-mon hs a e su ge y. Howe e , when ec o decomposi ion o e ac ion was pe o med J0 and J45 ec o s changes we e no s a is ically signi ican . Table 1: Re ac i e changes da a be o e and 6-mon hs a e su ge y. UDVA (unco ec ed dis ance isual acui y); CDVA (co ec ed dis ance isual acui y); MRSE (mani es e ac i e sphe ical equi alen ); J0 (Humph ey ec o c oss cylinde compound ixed a 0º/90º); J45 (Humph ey ec o c oss cylinde compound ixed a 45º/135º); D (diop e) aPai ed samples - es ; bWilcoxon signed ank es Va iable P eope a i e Pos ope a i e Change P UDVA (Snellen) 0.12±0.15 0.35±0.19 0.23±0.09 <0.001b CDVA (Snellen) 0.47±0.21 0.68±0.17 0.21±0.18 0.005a Sphe e (D) -3.43±2.21 -2.27±2.55 1.16±2.36 0.023b Cylinde (D) -5.42±1.94 -2.08±1.48 3.33±1.53 0.002a MRSE (D) -5.14±2.69 -3.32±2.50 1.82±2.58 0.004a J0 (D) 0.18±1.97 -0.07±1.07 -0.24±2.01 0.584a J45 (D) -0.02±2.17 -0.10±0.73 -0.08±2.05 0.867a Topog aphic pa ame e s and pos ope a i e ou comes Table 2 summa izes opog aphic and pachome ic da a p eope a i e and 6-mon hs a e Ke a ings implan a ion. As shown in Figu e 1, he Ke a ings la ening e ec was mo e e iden in he s eepes 3-mm a ea (P=0.05) when compa ed wi h he mean 3-mm ke a ome y eadings wi h a 1.94 D dec ease e ec on he an e io co neal as igma ism (P<0.001). The s onge la ening e ec was obse ed on he maximum ke a ome y eadings when compa ed p e- and pos ope a i e alues (P<0.001). A simila end was obse ed in he adius o an e io Bes Fi Sphe e (BFS) p eope a i e and 6-mon h a e su ge y (P=0.020). Mean Cen al Co neal Thickness (CCT) showed a sligh ly highe inc ease (2.0%), al hough non-clinically signi ican a e 6-mon hs o ICRS implan . A simila end was obse ed o apex (P=0.186) and minimum co neal hickness (P=0.067). As expec ed, signi ican co ela ions we e ound be ween pos ope a i e ou comes and p eope a i e opog aphic co neal pa ame e s, as well as segmen pa ame e s (Table 3). Using he nomog ams o ICRS implan a ion ecommended by he manu ac u e, we ound a mode a e co ela ion be ween he hicke Ke a ing segmen s and changes in mani es cylinde ( =0.491; P=0.023) and changes in BFS ( =0.440; P=0.046). Table 2: Summa y o he opog aphic and pachome ic da a a e 6-mon hs Ke a ing implan a ion. K1 (co neal powe in he la es 3-mm a ea); K2 (co neal powe in he s eepes 3-mm a ea); k2-k1 (mean co neal as igma ism in he 3-mm a ea); Km (mean co neal powe in he 3-mm a ea); Kmax (maximum co neal powe in he 8-mm a ea); BFS (bes - i sphe e); CCT (cen al co neal hickness); D (diop e); µm (mic ons) aPai ed samples - es ; bWilcoxon signed ank es Va iable Mean±SD P P eope a i e Pos ope a i e Change K1 (D) 46.02±3.47 46.01±3.15 -0.01±2.18 0.992a K2 (D) 51.34±4.55 49.41±3.25 -1.93±3.39 0.050b K2-K1 (D) 05.32±2.37 03.38±2.41 -1.94±3.50 0.020a Km (D) 48.49±3.70 47.71±2.97 -0.78±1.98 0.095a Kmax (D) 57.40±6.44 51.97±4.01 -5.43±5.16 <0.001a 4 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 An e io BFS (D) 43.55±3.05 42.40±2.24 -1.05±2.56 0.020b Eccen ici y 0.88±0.32 0.75±0.33 -0.13±0.36 0.079b CCT (mm) 478±39 487±58 9.10±49.73 0.412a CTapex (mm) 462±41 478±62 15.95±53.41 0.186a CTmin (mm) 448±40 461±47 12.90±30.57 0.067a Figu e 1: Humph ey ec o cylinde compound o he e ac ion showing a ema kable less dispe sion o pos ope a i e alues. Table 3: S a is ically signi ican co ela ions o he 6-mon h pos ope a i e ou comes wi h p eope a i e opog aphic, abe ome ic and Ke a ing segmen pa ame e s. UDVA (unco ec ed dis ance isual acui y); CDVA (co ec ed dis ance isual acui y); MRSE (mani es e ac i e sphe ical equi alen ); TKS ( hicke Ke a ing segmen ); K2 (co neal powe in he s eepes 3-mm a ea); K2-K1 (mean co neal as igma ism in he 3-mm a ea); Km (mean co neal powe in he 3-mm a ea); Kmax (maximum co neal powe in he 8-mm a ea); BFS (bes - i sphe e); CA (co neal as igma ism); RMS ( oo mean squa e); HOA (highe o de abe a ion); D (diop e); µm (mic ons); Ze nike e ms (Zo de mode) aPea son co ela ion; bRho Spea man Va iable Co ela iona,b Co ela ion Coe icien P Change in CDVA (Snellen) P eop K2 0.51 0.018a P eop Km 0.507 0.019a P eop Kmax 0.502 0.021a P eop CTapex -0.641 0.002a P eop CTmin -0.65 0.001a P eop P ima y Ve ical CA Z2 2-0.78 <0.001a P eop 4 h-o de sphe ical abe a ion Z4 0-0.54 0.011a Change in mani es Cylinde (D) P eop Cylinde -0.657 0.001a P eop MRSE -0.437 0.047a P eop K2 0.482 0.027a P eop kmax 0.582 0.006a P eop P ima y Oblique CA Z2 -2 -0.444 0.044a P eop Ho izon al Coma Z2 2-0.574 0.006a TKS 0.491 0.023a 5 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 Change in MRSE (D) P eop Sphe e -0.612 0.003b P eop Cylinde -0.475 0.029b P eop MRSE -0.668 0.001b P eop Ve ical Coma Z3 -1 -0.622 0.003b Change in Mean Kmax (D) P eop K2 -0.687 0.001a P eop K2-K1 -0.643 0.002a P eop Kmax -0.782 <0.001a P eop Eccen ici y -0.483 0.027a P eop 4 h-o de sphe ical abe a ion Z4 00.574 0.007a Change in Mean K2-K1 (D) P eop K2 -0.545 0.011a P eop K2-K1 -0.498 0.022a P eop Kmax -0.728 <0.001a Change in Mean BFS (D) P eop Kmax -0.634 0.002b P eop 4 h-o de sphe ical abe a ion Z4 00.466 0.033b P eop RMS HOA -0.437 0.048b TKS 0.44 0.046b Change in Ve ical Coma Z3 -1 (mm) P eop P ima y Oblique CA Z2 -2 0.461 0.035a P eop Ve ical Coma Z3 -1 0.871 <0.001a TKS 0.588 0.005a Change in Oblique T e oil (mm) P eop Sphe e -0.636 0.026a P eop MRSE -0.583 0.046a Abe ome ic pa ame e s and pos ope a i e ou comes Table 4 summa izes abe ome ic da a be o e and 6-mon hs a e su ge y. A signi ican dec ease was obse ed in he mean RMS high o de abe a ions alues (P=0.045). The e ical coma, oblique e oil and oblique co neal as igma ism became, on a e age, less posi i e a e su ge y (P=0.020, P=0.018 and P<0.01 espec i ely). No signi ican changes we e obse ed in o al RMS o o he esidual abe a ions. Nega i e signi ican co ela ions we e ound be ween pos ope a i e change in bes CDVA and se e al p eope a i e abe ome ic co neal pa ame e s (Table 3), such as p ima y e ical co neal as igma ism ( =-0.780; P<0.001), and sphe ical abe a ion ( =-0.540; P=0.011). Figu e 2 shows he nega i e ela ionship be ween change CDVA and he signi ican co ela ed abe ome ic ac o s. Simila ly, nega i e co ela ions we e ound be ween MRSE o change in mani es cylinde and di e en p eope a i e abe ome ic co neal pa ame e s. Sca e g ams showing he nega i e ela ionship be ween change in MRSE o mani es cylinde and p eope a i e coma can be seen in Figu e 3. Figu e 2: Sca e g ams showing he ela ionship be ween he change in he bes co ec ed dis ance isual acui y and: A) P eope a i e p ima y e ical co neal as igma ism; B) Sphe ical abe a ion. 6 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 Table 4: Summa y o he co neal abe ome ic da a a e 6-mon hs Ke a ing implan a ion. RMS ( oo mean squa e); HOA (highe o de abe a ion); µm (mic ons); Ze nike e ms (Zo de mode) aPai ed samples - es Va iable Mean±SD P P eope a i e Pos ope a i e Change RMS HOA (mm) 5.20±1.92 3.98±2.08 -1.22±2.63 0.045a Ve ical coma Z3 -1 (mm) 3.15±2.50 1.30±1.31 -1.85±1.83 0.020a Ho izon al coma Z3 1 (mm) 4.99±1.91 4.07±2.92 -0.92±1.16 0.111a P ima y sphe ical abe a ion Z4 0 (mm) 1.76±2.00 1.54±1.59 -0.22±1.73 0.657a P ima y Ve ical CA Z2 2 (mm) 4.72±3.81 3.31±4.03 -1.41±1.56 0.171a P ima y Oblique CA Z2 -2 (mm) 3.02±3.12 0.63±2.54 -2.39±1.86 0.009a Oblique T e oil Z3 3 (mm) 0.72±1.28 0.14±1.37 -0.58±0.91 0.018a Figu e 3: Sca e g ams showing he ela ionship be ween: A) The change in mani es e ac i e sphe ical equi alen and p eope a i e e ical coma; B) The change in mani es cylinde and p eope a i e ho izon al coma. Discussion The dec ease in isual quali y in subjec s wi h ke a oconus is no only due o low-o de abe a ions (sphe o-cylind ical e ac i e e o ) esul ing om co neal p o usion bu is also due o high- o de ones. This is p ac ically explained by he ac ha spec acles in mos cases a e no able o p o ide ull co ec ion. This s udy e alua ed he e ec o Ke a ings (mechanical implan a ion wi h a acuum de ice) on isual, e ac i e, opog aphic and abe ome ic ou comes in pa ien s wi h KC and high myopia 6-mon hs a e ICRS su ge y. Visual acui y and e ac i e pa ame e s The cu en s udy showed a signi ican educ ion in mani es sphe e, cylinde and sphe ical equi alen which a e in ag eemen wi h p e ious au ho s [15-20]. Consis en wi h he signi ican educ ion in e ac ion, ou s udy showed a signi ican imp o emen om 2 o 3 lines in UCVA and CDVA, which is consis en wi h o he s udies epo ing g ea e inc ease in UDVA han in CDVA, [16] while o he au ho s ha e obse ed be e esul s in CDVA han UDVA [17]. Fac o s jus i ying hese di e ences could be a ibu ed o a ia ions in he s uc u e and hickness o he segmen s, dis ance om he cen e , as well as o ien a ion and symme y in he inse ion o he ings [18]. In ac , baseline disease se e i y and he pa e n o ec asia a e so he e ogeneous in ke a oconic eyes, ha gene aliza ions a e no possible o may ha e no sense. A signi ican inding in his s udy is ha isual acui y changes ha e been highe o hose pa ien s wi h mo e se e e s ages o he disease. This inding ag ees wi h he cu en app oaches o sequen ial KC ea men ha assumes o he ea men s o ea ly o ms o KC including co neal c oss-linking and con ac lenses, lea ing ICRS when he disease is al eady s able and e en ually mo e ad anced [19]. An imp o emen in UDVA is a ibu able mos ly o a educ ion in lowe o de abe a ions (MRSE, sphe e o cylinde ), while an imp o emen in CDVA is a ibu ed o educ ion in co neal abe a ions (p ima y sphe ical abe a ion, co neal as igma ism, o coma). Topog aphic pa ame e s and pos ope a i e ou comes In he majo i y o s udies, ICRS implan a ion induces a signi ica i e educ ion in Km and Kmax eadings be ween 2 o 5 7 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 D, wi h a signi ican as igma ic educ ion be ween 1.5 o 2.75 D, allowing an imp o emen o isual acui y anging o 1 o 7 lines in CDVA [9-10,19-21]. This high a ia ion in isual pe o mance depends on KC s age, cone loca ion, as igma ism cha ac e iza ion and ICRS ype [19-22]. The p esen in es iga ion shows a no signi ican Km educ ion by 0.78 D, bu a signi ican Kmax educ ion by 5.43 D wi h a dec eased co neal as igma ism by close o 2.00 D associa ed wi h as igma ic educ ion by 3.33 D. Associa ed wi h hose changes, in his s udy, we ound an imp o emen o 0.21 Snellen uni s be ween p e-ope a i e and pos -ope a i e UDVA which is in ag eemen wi h mos o he e iewed li e a u e [19- 21]. Howe e , Km change in his s udy seems o be lowe han ha ound by o he au ho s, p obably because we ha e mo e se e e cases, wi h highe p eope a i e co neal as igma ism and poo e p e-ope a i e co ec ed and unco ec ed isual acui y, so he ac o s in ela ion o he cha ac e is ics o he subjec s wi h KC may be behind hese di e ences. The p esen s udy shows ha educ ion o co neal as igma ism is he main ac o jus i ying he imp o emen in isual acui y. This educ ion has been ound in mos o he eyes (19 ou o 21) excep one eye wi hou measu able changes and ano he eye wi h a signi ican inc ease in as igma ism. Reduc ion anged om 0 o 10 D o cylinde . In line wi h a gumen s o di e en indica ions o di e en s ages o KC, he ole o ICRS in co neal s abiliza ion has also been objec o in e es by he oph halmological communi y and has been p oposed ha maximum cu a u e and hinnes co neal hickness migh be used as indica o s o KC s abiliza ion/p og ession [23]. In he p esen s udy, we obse ed a educ ion in Kmax and an inc ease in he co neal hickness pa ame e s. Howe e , as we did only make a single measu emen a e su ge y, he p esen s udy canno e i y he e ec o ICRS in co neal s abili y o e ime due o he ela i ely sho ollow-up pe iod. Se e al s udies in es iga ing he po en ial ole o ICRS in disease s abiliza ion ound ha implan a ion o ICRS does no signi ican ly in luence p og essi e ke a oconus in young pa ien s wi h con i med p og ession o he disease [24-26]. Since o he au ho s ound ICRS implan a ion o be a s able p ocedu e o es o ing ision in pa ien s wi h KC, his ma e should be u he in es iga ed [27]. Finally, because o he la ening induced by his echnique, he e is ano he impo an bene icial ou come. Conside ing he limi ed imp o emen in UDVA and CDVA ob ained by he ICRS implan a ion, con ac lenses a e usually necessa y o complemen he ehabili a ion. This s a egy has p o ed o be success ul in p e ious publica ions, using di e en ma e ials and i ing app oaches [28-29]. The opog aphic indings om his s udy migh be also ele an on his ega d as we ha e ound a educ ion in maximum ke a ome ic eading and educ ion in an e io co neal as igma ism. This migh ha e implica ions in con ac lens i ing a di e en le els. Fi s , he la ening e ec obse ed in he la ening o he s eepes me idian by 1.90 D and by o e 5.50 D in he Kmax pa ame e . This la ening is also obse ed in he BFS pa ame e wi h a educ ion o nea ly 1.00 D. This ep esen s a la ening o he o e all co neal cu a u e ha migh imp o e he i ing o a co neal igid gas pe meable con ac lens. Second, educ ion o an e io co neal as igma ism nea ly 2.00 D migh also imp o e he i ing o he con ac lens as i is usual o ind a s eep i ing along he la es me idian. F om he i ing poin o iew, we hypo hesize ha a educ ion o nea ly 0.20 mm in he s eepes cu a u e, 0.40 mm in co neal as igma ism migh imp o e co neal lens i ing. Howe e , we acknowledge ha he p esence o he ICRS, hickening he mid-pe iphe al co nea, migh also p esen a challenge o he i ing as he loca ion o hese segmen s migh c ea e a mechanical con lic wi h he unde lying co neal issue. Howe e , his migh be o e come using la ge diame e lenses suppo ed by he pe iphe al co nea ou side he 5-6 mm o he ICRS unnel. Abe ome ic pa ame e s and pos ope a i e ou comes When co neal abe a ions we e analyzed, e ical coma, p ima y oblique co neal as igma ism and e oil dec eased 6-mon hs a e su ge y, as he main abe ome ic changes ound in his s udy. In addi ion, we ound a signi ican pos ope a i e RMS HOA a 6 mm imp o emen while no changes we e obse ed in o he esidual abe a ions which suppo s he indings o some au ho s and con adic s o he s [15,20]. The p edominan abe ome ic de ec in KC is he coma abe a ion, pa icula ly i s e ical componen , such is he case ha Alió and Shabayek used his pa ame e o modi y he classic Amsle -K umeich classi ica ion o KC, in oducing coma abe a ion as one o he indica o s [30]. Coma has been ound o be dec eased in he sho - e m and he long- e m pe iods a e ICRS implan a ion [8,17,21]. Since di e en au ho s ha e demons a e ha coma has a nega i e e ec on isual acui y [24], he educ ion in coma abe a ion, especially in e ical coma, migh also explain he imp o emen in CDVA ound in his in es iga ion, which is in ag eemen wi h o he au ho s [20,23,25]. Howe e , he e a e o he s udies epo ing no signi ican changes in any co neal abe ome ic pa ame e a e ICRS implan a ion by mechanical unneliza ion, which is con adic o y o he indings o he p esen s udy [15]. Tha s udy ound ha mechanical unneliza ion speci ically o In acs implan a ion in eyes wi h ea ly o mode a e KC has limi ed he po en ial abe ome ic co ec ion because he p ocedu e i sel gene a ed new abe a ions, pa icula ly nega i e p ima y sphe ical abe a ion, and p ima y coma, bu his end was no speci ically con i med o Ke a ings because he limi a ions o he s udy o his segmen ype. O he ac o s could explain hese di e ences, o example, we may ha e included mo e mode a e and se e e cases and obse ed less complica ions compa ed wi h p e ious s udies. Ano he possible explana ion, as men ioned abo e, could be he cha ac e is ics o he segmen s as well as o ien a ion and symme y in he ICRS inse ion [18,26]. Limi a ions A limi a ion o his s udy is he educed sample size. Howe e , based on ou ini ial es ima ions, he sample was powe ed o obse e a leas 1 line o imp o emen in isual acui y wi h 18 eyes en olled. A u he limi a ion migh be conside ed he ac ha he implan a ion mode has been manual while em osecond lase -assis ed echnology migh be conside ed he e e ence o ICRS implan a ion. In ac , em osecond lase can assis in a be e p edic ion o he dep h and a ea o implan a ion, minimizes p ocedu e du a ion, and educes he isk o in lamma ion, bu 8 Med Su g Oph hal Res Copy igh © Ja ie González-Pé ez MSOR.000565. 3(3).2024 p e ious esea ch has ailed o demons a e supe io i y in isual ou comes when compa ed wi h manual implan a ion [15]. In addi ion, an al e na i e o he manual app oach is o use a acuum de ice, such as he employed in his s udy o s abilize he globe du ing c ea ion o he co neal unnel o ob ain be e isual acui y and mo e con olled co neal shape, howe e mo e esea ch is equi ed in his a ea o e alua e and compa e he clinical ou comes. Fu he mo e, we bea in mind ha s ill nowadays mos o he implan a ions a e made wi h manual echnique including many e ia y e e ence hospi als as is ou case. 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