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Song C, Li L, Liu C, Hu L, Bai J, Liang W, Zhao L, Song W, Li S. Whole-exome sequencing screening for candidate genes and variants associated with primary sporadic keratoconus in Chinese patients. Exp Eye Res 2024; 245:109978. [PMID: 38908538 DOI: 10.1016/j.exer.2024.109978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 04/29/2024] [Accepted: 06/19/2024] [Indexed: 06/24/2024]
Abstract
The pathogenesis of keratoconus (KC) is complex, and genetic factors play an important role. The purpose of this study was to screen and analyse candidate genes and variants in Chinese patients with primary sporadic KC. Whole-exome sequencing (WES) was performed to identify candidate genes and variants in 105 unrelated Chinese patients with primary sporadic KC. Through a series of screening processes, 54 candidate variants in 26 KC candidate genes were identified in 53 KC patients (53/105, 50.5%). These 54 candidate variants included 10 previously identified variants in 9 KC candidate genes and 44 novel variants in 20 KC candidate genes. The previously identified variants occurred in 25.7% (27/105) of patients. Of these, 4 variants (COL6A5, c.5014T > G; CAST, c.1814G > A; ZNF469, c.946G > A; and MPDZ, c.3836A > G) were identified for the first time in Chinese KC patients. The novel variants occurred in 33.3% (35/105) of patients. Of the 26 screened KC candidate genes, 11 KC candidate genes (CAT, COL12A1, FLG, HKDC1, HSPG2, PLOD1, ITGA2, TFAP2B, USH2A, WNT10A, and COL6A5) were found to be potentially pathogenic in Chinese KC patients for the first time. Gene Ontology (GO) biological process (BP) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the 26 KC candidate genes using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The results showed that the KC candidate genes were significantly enriched in biological processes such as collagen fibril organization and extracellular matrix (ECM) organization and in ECM-receptor interaction and protein digestion and absorption pathways. The results further expand the spectrum of KC candidate variants and provide a basis for further KC gene studies.
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Affiliation(s)
- Chunyuan Song
- Aier Eye Hospital, Jinan University, Guangzhou, 510071, China
| | - Ling Li
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China; Aier Corneal Institute, Beijing, 100021, China
| | - Chang Liu
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China; Aier Corneal Institute, Beijing, 100021, China
| | - Luping Hu
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China
| | - Jie Bai
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China; Aier Corneal Institute, Beijing, 100021, China
| | - Weiyan Liang
- Aier Eye Hospital of Anhui Medical University, Anhui, 230031, China; Tianjin Aier Eye Hospital, Tianjin, 300000, China
| | - Lin Zhao
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China; Aier Corneal Institute, Beijing, 100021, China
| | - Wenxiu Song
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China; Aier Corneal Institute, Beijing, 100021, China
| | - Shaowei Li
- Aier Eye Hospital, Jinan University, Guangzhou, 510071, China; Beijing Aier-Intech Eye Hospital, Beijing, 100021, China; Aier Corneal Institute, Beijing, 100021, China; Aier Eye Hospital of Anhui Medical University, Anhui, 230031, China; Tianjin University, Tianjin, 300072, China.
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Bergmanson JPG, Burns AR, Walker MK. Central versus peripheral thickness in the human cornea explained. Cont Lens Anterior Eye 2024; 47:102165. [PMID: 38589268 DOI: 10.1016/j.clae.2024.102165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 03/29/2024] [Accepted: 04/03/2024] [Indexed: 04/10/2024]
Abstract
PURPOSE The human cornea is thicker in the periphery than the center and it has been suggested that this must be due to greater numbers of lamellae in the peripheral corneal stroma. The purpose of this study was to use high-resolution ultrastructural imaging to determine if the greater thickness of the peripheral cornea is due to the presence of more lamellae or if there is some other anatomical explanation. METHODS In this study, full thickness corneas from three human donors were processed for light microscopy (LM) and transmission electron microscopy (TEM). Images were taken in three distinct stromal regions (anterior, middle, and posterior) from the central and peripheral cornea. Stromal thickness was evaluated by LM while TEM was used to evaluate numbers and thicknesses of lamellae, mean collagen fibril diameter, and mean collagen fibril density. RESULTS Mean stromal thickness was significantly thinner in the central (415 ± 34 µm) compared to the peripheral (536 ± 29 µm) cornea (P = 0.009). Numbers of lamellae were not significantly different between central (246 ± 14) and peripheral (251 ± 14) cornea. Average lamellar thickness was not different across all regions of the cornea, except for the peripheral posterior where the lamellae were approximately 50 % thicker (P < 0.05). Collagen fibril diameters were larger in the peripheral cornea by approximately 30 % when compared to the central cornea, in all regions (P < 0.01). CONCLUSIONS This study shows that it is an increase peripheral posterior lamellar thickness, rather than an increase in the number of lamellae, that accounts for the increase in corneal stromal thickness in the periphery of the human cornea. While collagen fibril diameters are greater throughout the peripheral stroma, the lamellae in the mid and anterior peripheral stroma are not thicker than centrally.
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Affiliation(s)
- Jan P G Bergmanson
- University of Houston, College of Optometry, Texas Eye Research & Technology Center, 4401 Martin Luther King Boulevard, Houston, TX 77204-2020, United States.
| | - Alan R Burns
- University of Houston, College of Optometry, Texas Eye Research & Technology Center, 4401 Martin Luther King Boulevard, Houston, TX 77204-2020, United States
| | - Maria K Walker
- University of Houston, College of Optometry, Texas Eye Research & Technology Center, 4401 Martin Luther King Boulevard, Houston, TX 77204-2020, United States
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Wu Z, Zhang Y, Li Y, Yang F, Su X, Gao Y, Wei S, Li J. Correlation between Corneal Volume and Corneal Biomechanics and Corneal Volume Significance in Staging and Diagnosing Keratoconus. J Ophthalmol 2024; 2024:8422747. [PMID: 38841207 PMCID: PMC11152760 DOI: 10.1155/2024/8422747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 05/09/2024] [Accepted: 05/18/2024] [Indexed: 06/07/2024] Open
Abstract
Purpose To investigate the relationship between corneal volume (CV) at different zones and corneal biomechanics in keratoconus (KC) along with the significance of CV in diagnosing and staging KC. Methods This prospective clinical study included 456 keratoconic eyes (Group B) and 198 normal eyes (Group A). Using the topographic KC classification method, Group B was divided into subgroups based on severity (mild, moderate, and severe). The CVs of the 3 mm, 5 mm, and 7 mm zones and biomechanical parameters were obtained by Pentacam and Corvis ST. The diagnostic utility of multirange CVs at different disease stages and severity was determined using a receiver operating characteristic (ROC) curve analysis. Results The CV of the 7-mm zone had the strongest correlation with A1V, A2T, PD, DA ratio max (2 mm), DA ratio max (1 mm), ARTh, integrated radius, SPA1, and CBI (p < 0.01). The CVs of the Group B subgroups were significantly lower than those of Group A for each diameter range (p < 0.05). There were significant differences between the severe, mild, and moderate subgroups for the 3 mm zone (p < 0.05, all). The 3 mm zone CV exhibited better diagnostic ability in each group for distinguishing KC from the normal cornea (Groups A vs. B: area under the ROC curve (AUC) = 0.926, Groups A vs. B1: AUC = 0.894, Groups A vs. B2: AUC = 0.925, Groups A vs. B3: AUC = 0.953). Conclusion The CV significantly decreased in keratoconic eyes. Progressive thinning in the 3 mm zone may be a valuable measurement for detecting and staging KC. Combining the CV examination with corneal biomechanical information may effectively enhance the ability to detect KC.
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Affiliation(s)
- Zhiqing Wu
- Department of Ophthalmology, Hospital of Shaanxi Normal University, Xi'an 710004, China
| | - Yaohua Zhang
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xi'an 710004, China
| | - Yong Li
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xi'an 710004, China
| | - Fang Yang
- Department of Ophthalmology, Renmin Hospital, Hubei University of Medicine, Shiyan 442000, Hubei, China
| | - Xirui Su
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xi'an 710004, China
| | - Yan Gao
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xi'an 710004, China
| | - Shengsheng Wei
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xi'an 710004, China
| | - Jing Li
- Shaanxi Eye Hospital, Xi'an People's Hospital (Xi'an Fourth Hospital), Affiliated People's Hospital of Northwest University, Xi'an 710004, China
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Heidari Z, Mohammadpour M, Hajizadeh F, Fotouhi A, Hashemi H. Corneal layer thickness in keratoconus using optical coherence tomography. Clin Exp Optom 2024; 107:32-39. [PMID: 37121670 DOI: 10.1080/08164622.2023.2201369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 04/05/2023] [Indexed: 05/02/2023] Open
Abstract
CLINICAL RELEVANCE Accurate thickness measurement of corneal layers using anterior segment OCT can be used to improve visual outcomes. Understanding its applications is essential for optometric practices to enhance eye care procedures. BACKGROUND To evaluate the thicknesses of different corneal layers for identifying keratoconus (KCN) and subclinical keratoconus (SKCN) using spectral-domain optical coherence tomography (SD-OCT). METHODS This prospective study analyzed 60 eyes with KCN, 48 eyes with SKCN, and 53 normal eyes. The central corneal thickness (CCT) and thicknesses of the epithelium, Bowman, stroma, and Descemet-endothelium layers were measured using SD-OCT. One way analysis of variance and the area under the curve (AUC) were used to evaluate the parameters. The Delong method was used to compare AUCs. RESULTS In KCN, CCT and thicknesses of epithelium, Bowman, stroma, and Descemet-endothelium layers were 495.5 ± 41.7, 52.6 ± 6.4,11.5 ± 1.4, 415.5 ± 38.9, and 12.3 ± 1.7 µm, respectively. These thickness values were respectively 524.5 ± 33.3, 56.8 ± 6.8, 11.5 ± 1.6, 439.8 ± 30.6, and 12.4 ± 1.7 µm in SKCN and 563.8 ± 37.9, 57.7 ± 6.9, 12.2 ± 1.6, 469.5 ± 33.7, and 12.8 ± 2.1µm in normal group. Total cornea and stroma in KCN and SKCN, and epithelium in KCN were significantly thinner compared to the normal group (P < 0.001). The highest AUC values were observed for CCT in KCN (AUC 0.90) and SKCN (AUC 0.782). The diagnostic accuracy was significantly higher for stromal thickness in KCN (sensitivity 81.7%, specificity 73.6%, AUC 0.871) and SKCN (sensitivity 80.0%, specificity 56.6%, AUC 0.751) than other individual corneal layers (Delong, P < 0.001) . CONCLUSION CCT can accurately distinguish keratoconus from normal eyes. However, central corneal stromal thinning was the most sensitive diagnostic index for early detection of SKCN. Developing standardized stromal maps may be helpful for detecting SKCN.
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Affiliation(s)
- Zahra Heidari
- Department of Ophthalmology, Bu-Ali Sina Hospital, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Mehrdad Mohammadpour
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
- Department of Ophthalmology, Farabi Eye Hospital and Eye Research Center, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Fedra Hajizadeh
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Akbar Fotouhi
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
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Nabil KM, Elmassry AAK, Ntakarusho S, Said AA. Intraocular pressure after combined photorefractive keratectomy and corneal collagen cross-linking for keratoconus. Int Ophthalmol 2023; 43:4837-4849. [PMID: 37861937 PMCID: PMC10724307 DOI: 10.1007/s10792-023-02886-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 09/27/2023] [Indexed: 10/21/2023]
Abstract
PURPOSE The purpose of this prospective study was to evaluate the effect of combined photorefractive keratectomy (PRK) and corneal collagen cross-linking (CXL) on intraocular pressure (IOP) in patients with keratoconus (KC). METHODS We included 64 eyes of 34 patients (19 males and 15 females; age: 19-40y) with stages 1-2 keratoconus which had undergone combined wavefront-optimized photorefractive keratectomy and corneal collagen cross linking. Two other groups of patients were added as controls: the PRK group including 110 eyes of 57 patients (23 males and 34 females; age: 18-44y) which had undergone wavefront-optimized photorefractive keratectomy for myopic refractive errors, and the CXL group including 36 eyes of 23 patients (14 males and 9 females; age: 12-38y) with keratoconus, not filling the inclusion criteria for combined PRK and CXL, which had undergone corneal collagen cross-linking. IOP was recorded preoperatively and postoperatively at 3, 6 and 12 months follow-up visits. RESULTS Preoperative IOP in both CXL (12.1 ± 2.53 mmHg) and PRK + CXL (13.2 ± 2.50 mmHg) groups was significantly lower than PRK group (15.8 ± 3.10 mmHg) (F = 30.505, p < 0.001). At 3 months postoperatively, IOP showed no statistically significant difference between the three studied groups (F = 1.821, p = 0.164). At 6 months postoperatively, IOP in the CXL group (14.6 ± 2.64 mmHg) was significantly higher than both PRK (13.4 ± 2.27 mmHg) and PRK + CXL (13.3 ± 2.62 mmHg) groups (F = 3.721, p = 0.026). At 12 months postoperatively, IOP in the CXL group (14.3 ± 2.69 mmHg) was significantly higher than the PRK group (13.2 ± 2.23 mmHg) and was higher than PRK + CXL group (13.3 ± 2.59 mmHg) although not statistically significant (F = 3.393, p = 0.035). Regarding the percent of change from preoperative IOP, a statistically significant difference between the three studied groups was detected at 3, 6 and 12 months postoperatively (H = 117.459, 109.303, 122.694 respectively, p < 0.001). The median percent of change from preoperative IOP in the PRK group was -16.7%, -15%, and -16.7%, in the CXL group was + 14.3%, + 19.4%, and + 19.1%, while in PRK + CXL group was 0% at 3, 6 and 12 months postoperatively. (Post-hoc power analysis 75%). CONCLUSIONS Combined PRK and CXL in patients with KC shows no significant effect on IOP, in contrast to either procedure performed separately.
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Affiliation(s)
- Karim Mahmoud Nabil
- Department of Ophthalmology, Faculty of Medicine, University of Alexandria, Postal Code 21523, 19 Amin Fekry Street, Raml Station, Alexandria, Egypt.
| | - Ahmed Abdel Karim Elmassry
- Department of Ophthalmology, Faculty of Medicine, University of Alexandria, Postal Code 21523, 19 Amin Fekry Street, Raml Station, Alexandria, Egypt
| | - Silas Ntakarusho
- Department of Ophthalmology, University of Ngozi, Ngozi, Burundi
| | - Amr Ahmed Said
- Department of Ophthalmology, Faculty of Medicine, University of Alexandria, Postal Code 21523, 19 Amin Fekry Street, Raml Station, Alexandria, Egypt
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Lan G, Twa MD, Song C, Feng J, Huang Y, Xu J, Qin J, An L, Wei X. In vivo corneal elastography: A topical review of challenges and opportunities. Comput Struct Biotechnol J 2023; 21:2664-2687. [PMID: 37181662 PMCID: PMC10173410 DOI: 10.1016/j.csbj.2023.04.009] [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: 02/14/2023] [Revised: 04/07/2023] [Accepted: 04/12/2023] [Indexed: 05/16/2023] Open
Abstract
Clinical measurement of corneal biomechanics can aid in the early diagnosis, progression tracking, and treatment evaluation of ocular diseases. Over the past two decades, interdisciplinary collaborations between investigators in optical engineering, analytical biomechanical modeling, and clinical research has expanded our knowledge of corneal biomechanics. These advances have led to innovations in testing methods (ex vivo, and recently, in vivo) across multiple spatial and strain scales. However, in vivo measurement of corneal biomechanics remains a long-standing challenge and is currently an active area of research. Here, we review the existing and emerging approaches for in vivo corneal biomechanics evaluation, which include corneal applanation methods, such as ocular response analyzer (ORA) and corneal visualization Scheimpflug technology (Corvis ST), Brillouin microscopy, and elastography methods, and the emerging field of optical coherence elastography (OCE). We describe the fundamental concepts, analytical methods, and current clinical status for each of these methods. Finally, we discuss open questions for the current state of in vivo biomechanics assessment techniques and requirements for wider use that will further broaden our understanding of corneal biomechanics for the detection and management of ocular diseases, and improve the safety and efficacy of future clinical practice.
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Affiliation(s)
- Gongpu Lan
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Michael D Twa
- College of Optometry, University of Houston, Houston, TX 77204, United States
| | - Chengjin Song
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
| | - JinPing Feng
- Institute of Engineering and Technology, Hubei University of Science and Technology, Xianning, Hubei 437100, China
| | - Yanping Huang
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jingjiang Xu
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jia Qin
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Lin An
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Xunbin Wei
- Biomedical Engineering Department, Peking University, Beijing 100081, China
- International Cancer Institute, Peking University, Beijing 100191, China
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
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Biomechanics of keratoconus: Two numerical studies. PLoS One 2023; 18:e0278455. [PMID: 36730305 PMCID: PMC9894483 DOI: 10.1371/journal.pone.0278455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 11/16/2022] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND The steep cornea in keratoconus can greatly impair eyesight. The etiology of keratoconus remains unclear but early injury that weakens the corneal stromal architecture has been implicated. To explore keratoconus mechanics, we conducted two numerical simulation studies. METHODS A finite-element model describing the five corneal layers and the heterogeneous mechanical behaviors of the ground substance and lamellar collagen-fiber architecture in the anterior and posterior stroma was developed using the Holzapfel-Gasser-Ogden constitutive model. The geometry was from a healthy subject. Its stroma was divided into anterior, middle, and posterior layers to assess the effect of changing regional mechanical parameters on corneal displacement and maximum principal stress under intraocular pressure. Specifically, the effect of softening an inferocentral corneal button, the collagen-based tissues throughout the whole cornea, or specific stromal layers in the button was examined. The effect of simply disorganizing the orthogonally-oriented posterior stromal fibers in the button was also assessed. The healthy cornea was also subjected to eye rubbing-like loading to identify the corneal layer(s) that experienced the most tensional stress. RESULTS Conical deformation and corneal thinning emerged when the corneal button or the mid-posterior stroma of the button underwent gradual softening or when the collagen fibers in the mid-posterior stroma of the button were dispersed. Softening the anterior layers of the button or the whole cornea did not evoke conical deformation. Button softening greatly increased and disrupted the stress on Bowman's membrane while mid-posterior stromal softening increased stress in the anterior layers. Eye rubbing profoundly stressed the deep posterior stroma while other layers were negligibly affected. DISCUSSION These observations suggest that keratoconus could be initiated, at least partly, by mechanical instability/damage in the mid-posterior stroma that then imposes stress on the anterior layers. This may explain why subclinical keratoconus is marked by posterior but not anterior elevation on videokeratoscopy.
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Santodomingo-Rubido J, Carracedo G, Suzaki A, Villa-Collar C, Vincent SJ, Wolffsohn JS. Keratoconus: An updated review. Cont Lens Anterior Eye 2022; 45:101559. [PMID: 34991971 DOI: 10.1016/j.clae.2021.101559] [Citation(s) in RCA: 162] [Impact Index Per Article: 81.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 11/23/2021] [Accepted: 12/12/2021] [Indexed: 02/06/2023]
Abstract
Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Keratoconus normally develops in the second and third decades of life and progresses until the fourth decade. The condition affects all ethnicities and both sexes. The prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 cases per 100,000 persons/year, respectively, with highest rates typically occurring in 20- to 30-year-olds and Middle Eastern and Asian ethnicities. Progressive stromal thinning, rupture of the anterior limiting membrane, and subsequent ectasia of the central/paracentral cornea are the most commonly observed histopathological findings. A family history of keratoconus, eye rubbing, eczema, asthma, and allergy are risk factors for developing keratoconus. Detecting keratoconus in its earliest stages remains a challenge. Corneal topography is the primary diagnostic tool for keratoconus detection. In incipient cases, however, the use of a single parameter to diagnose keratoconus is insufficient, and in addition to corneal topography, corneal pachymetry and higher order aberration data are now commonly used. Keratoconus severity and progression may be classified based on morphological features and disease evolution, ocular signs, and index-based systems. Keratoconus treatment varies depending on disease severity and progression. Mild cases are typically treated with spectacles, moderate cases with contact lenses, while severe cases that cannot be managed with scleral contact lenses may require corneal surgery. Mild to moderate cases of progressive keratoconus may also be treated surgically, most commonly with corneal cross-linking. This article provides an updated review on the definition, epidemiology, histopathology, aetiology and pathogenesis, clinical features, detection, classification, and management and treatment strategies for keratoconus.
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Affiliation(s)
| | - Gonzalo Carracedo
- Department of Optometry and Vision, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Asaki Suzaki
- Clinical Research and Development Center, Menicon Co., Ltd., Nagoya, Japan
| | - Cesar Villa-Collar
- Department of Pharmacy, Biotechnology, Nutrition, Optics and Optometry, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, Madrid, Spain
| | - Stephen J Vincent
- Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Centre for Vision and Eye Research, Queensland University of Technology, Brisbane, Australia
| | - James S Wolffsohn
- School of optometry, Health and Life Sciences, Aston University, Birmingham B4 7ET, United Kingdom
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[Histological changes in keratoconus and wound healing after corneal cross-linking]. Ophthalmologe 2021; 119:342-349. [PMID: 34874483 DOI: 10.1007/s00347-021-01537-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2021] [Indexed: 10/19/2022]
Abstract
BACKGROUND Keratoconus is classified as a corneal ectasia and is a multifactorial disease. In those affected, mostly adolescent patients visual deterioration occurs due to the development of irregular astigmatism. Treatment by corneal cross-linking (CXL) has been indicated in progressive disease for several years. OBJECTIVE To present the pathophysiology and histological changes in keratoconus as well as wound healing processes after CXL and their potential complications. MATERIAL AND METHODS Histological changes in keratoconus as well as wound healing processes after CXL and their potential complications are presented based on histological examination of corneal specimens with keratoconus with and without a condition after CXL. Relevant literature and own data are analyzed and discussed. RESULTS Besides inflammatory processes, atopic and genetic dispositions play a role in the development of keratoconus. The histological characteristics of keratoconus include changes in the epithelium, Bowman's layer and stroma. Wound healing processes after CXL include healing of the surface epithelium and transient loss of keratocytes and nerve fibers. CONCLUSION Keratoconus shows characteristic histopathological changes, such as epithelial irregularities, stromal thinning and breaks of Bowman's layer, whereas the endothelium and Descemet's membrane remain unchanged (apart from cases of corneal hydrops). After CXL wound healing processes can be followed primarily in vivo by confocal microscopy. Complications after CXL are rare. Persistent loss of keratocytes can be clinically manifested as a visually relevant scar.
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Chameettachal S, Puranik CJ, Veluthedathu MN, Chalil NB, John R, Pati F. Thickening of Ectatic Cornea through Regeneration Using Decellularized Corneal Matrix Injectable Hydrogel: A Strategic Advancement to Mitigate Corneal Ectasia. ACS APPLIED BIO MATERIALS 2021; 4:7300-7313. [PMID: 35006959 DOI: 10.1021/acsabm.1c00821] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ectatic corneal diseases are a group of eye disorders characterized by progressive thinning and outward bulging of the cornea, resulting in vision impairment. A few attempts have been made to use cornea-derived extracellular matrix hydrogels for corneal tissue engineering; however, no studies have investigated its application in corneal ectasia. In this study, we have first developed an animal surgical model that mimics a few specific phenotypes of ectatic cornea. Later, we investigated the potential of decellularized cornea matrix hydrogels (dCMH) from both human and bovine sources in increasing the thickness of the cornea in the developed surgical model. Our data advocate that surgical stromal depletion can be followed to establish ectatic models and can also provide information on the biocompatibility of materials, its integration with native stroma, degradation over time, and tissue remodeling. We observed that dCMH from both sources could integrate with ectatic thin corneal stroma and helps in regaining the thickness by regenerating a reasonably functional and transparent stroma; however, no significant difference was spotted between the dCMH made from human and bovine corneal tissue sources. Hence, this study is a promising step toward developing a non-invasive technique for the treatment of corneal ectasia by using dCMH.
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Affiliation(s)
- Shibu Chameettachal
- Department of Biomedical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy Hyderabad, Telangana 502284, India
| | - Charuta J Puranik
- Oculus Regenerus Eye Care and Research Center, Nanalnagar, Hyderabad, Telangana 500008, India
| | - Mohamed Nijas Veluthedathu
- Department of Biomedical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy Hyderabad, Telangana 502284, India
| | - Najathulla Bhagavathi Chalil
- Department of Materials Science and Metallurgical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy , Hyderabad, Telangana 502284, India
| | - Renu John
- Department of Biomedical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy Hyderabad, Telangana 502284, India
| | - Falguni Pati
- Department of Biomedical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy Hyderabad, Telangana 502284, India
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11
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Bergmanson JPG, Burns AR, Naroo SA. Central versus peripheral corneal thickness - A White spot on the corneal (anatomy) map. Cont Lens Anterior Eye 2021; 44:101473. [PMID: 34099389 DOI: 10.1016/j.clae.2021.101473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Jan P G Bergmanson
- Texas Eye Research and Technology Center, University of Houston College of Optometry, Houston, TX, USA
| | - Alan R Burns
- Texas Eye Research and Technology Center, University of Houston College of Optometry, Houston, TX, USA
| | - Shehzad A Naroo
- College of Health and Life Sciences, Aston University, B4 7 ET, UK.
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12
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Evaluation of topographic, tomographic, topometric, densitometric, and aberrometric features of cornea with pentacam HR system in subclinical keratoconus. Int Ophthalmol 2021; 41:1729-1741. [PMID: 33772701 DOI: 10.1007/s10792-021-01732-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 01/30/2021] [Indexed: 12/27/2022]
Abstract
PURPOSE To investigate topographic, tomographic, topometric, densitometric, and aberrometric parameters in subclinical keratoconus with the Pentacam HR imaging system. METHODS Data of 3128 patients were evaluated, finding in 108 patients clinical keratoconus in one eye and subclinical keratoconus in the other. Corneal topographic, tomographic, topometric, densitometric, and aberrometric values obtained using the Pentacam HR imaging system were compared between clinical keratoconus, subclinical keratoconus, and normal eyes. RESULTS Comparing eyes with subclinical keratoconus and the control group, while flat K, horizontal coma, horizontal trefoil, and vertical trefoil values were similar (p > 0.05 for each), all other parameters were significantly different (p < 0.05 for each). Densitometry values of eyes with subclinical keratoconus were significantly higher in all layers of the 0-2 mm annular area and in the anterior and central layers of the 2-6 mm annular area compared to the control group (p < 0.05 for each). According to the receiver operating characteristic curve analysis, the densitometry region with the largest area under the curve was the anterior layer of the 0-2 mm annular area. The sensitivity in this region was 79.4% and the specificity 73.2% in distinguishing eyes with subclinical keratoconus from normal eyes when 19.3 GSU was considered the threshold. CONCLUSION Corneal densitometry values in the 0-2 and 2-6 mm annular areas, especially in the anterior layers, are parameters that can be used to predict and distinguish subclinical keratoconus from normal eyes.
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Zhou D, Abass A, Lopes B, Eliasy A, Hayes S, Boote C, Meek KM, Movchan A, Movchan N, Elsheikh A. Fibril density reduction in keratoconic corneas. J R Soc Interface 2021; 18:20200900. [PMID: 33622146 DOI: 10.1098/rsif.2020.0900] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
This study aims to estimate the reduction in collagen fibril density within the central 6 mm radius of keratoconic corneas through the processing of microstructure and videokeratography data. Collagen fibril distribution maps and topography maps were obtained for seven keratoconic and six healthy corneas, and topographic features were assessed to detect and calculate the area of the cone in each keratoconic eye. The reduction in collagen fibril density within the cone area was estimated with reference to the same region in the characteristic collagen fibril maps of healthy corneas. Together with minimum thickness and mean central corneal refractive power, the cone area was correlated with the reduction in the cone collagen fibrils. For the corneas considered, the mean area of keratoconic cones was 3.30 ± 1.90 mm2. Compared with healthy corneas, fibril density in the cones of keratoconic corneas was lower by as much as 35%, and the mean reduction was 17 ± 10%. A linear approximation was developed to relate the magnitude of reduction to the refractive power, minimum corneal thickness and cone area (R2 = 0.95, p < 0.001). Outside the cone area, there was no significant difference between fibril arrangement in healthy and keratoconic corneas. The presented method can predict the mean fibril density in the keratoconic eye's cone area. The technique can be applied in microstructure-based finite-element models of the eye to regulate its stiffness level and the stiffness distribution within the areas affected by keratoconus.
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Affiliation(s)
- Dong Zhou
- Department of Mathematical Sciences, School of Physical Sciences, University of Liverpool, Liverpool, UK
| | - Ahmed Abass
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, UK.,Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Egypt
| | - Bernardo Lopes
- Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool, UK.,Department of Ophthalmology, Federal University of Sao Paulo, Brazil
| | - Ashkan Eliasy
- Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool, UK
| | - Sally Hayes
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Craig Boote
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Keith M Meek
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Alexander Movchan
- Department of Mathematical Sciences, School of Physical Sciences, University of Liverpool, Liverpool, UK
| | - Natalia Movchan
- Department of Mathematical Sciences, School of Physical Sciences, University of Liverpool, Liverpool, UK
| | - Ahmed Elsheikh
- Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool, UK.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing 100083, People's Republic of China.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
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14
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Anterior Segment Findings in Patients With Osteogenesis Imperfecta: A Case-Control Study. Cornea 2020; 39:935-939. [DOI: 10.1097/ico.0000000000002345] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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15
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Karolak JA, Gambin T, Rydzanicz M, Polakowski P, Ploski R, Szaflik JP, Gajecka M. Accumulation of sequence variants in genes of Wnt signaling and focal adhesion pathways in human corneas further explains their involvement in keratoconus. PeerJ 2020; 8:e8982. [PMID: 32328353 PMCID: PMC7164425 DOI: 10.7717/peerj.8982] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 03/25/2020] [Indexed: 12/16/2022] Open
Abstract
Background Keratoconus (KTCN) is a protrusion and thinning of the cornea, resulting in loss of visual acuity. The etiology of KTCN remains unclear. The purpose of this study was to assess the potential involvement of new genetic variants in KTCN etiology based on both the genomic and transcriptomic findings recognized in the same corneal tissues. Methods Corneal tissues derived from five unrelated Polish individuals with KTCN were examined using exome sequencing (ES), followed by enrichment analyses. For comparison purposes, the datasets comprising ES data of five randomly selected Polish individuals without ocular abnormalities and five Polish patients with high myopia were used. Expression levels of selected genes from the overrepresented pathways were obtained from the previous RNA-Seq study. Results Exome capture discovered 117 potentially relevant variants that were further narrowed by gene overrepresentation analyses. In each of five patients, the assessment of functional interactions revealed rare (MAF ≤ 0.01) DNA variants in at least one gene from Wnt signaling (VANGL1, WNT1, PPP3CC, LRP6, FZD2) and focal adhesion (BIRC2, PAK6, COL4A4, PPP1R12A, PTK6) pathways. No genes involved in pathways enriched in KTCN corneas were overrepresented in our control sample sets. Conclusions The results of this first pilot ES profiling of human KTCN corneas emphasized that accumulation of sequence variants in several genes from Wnt signaling and/or focal adhesion pathways might cause the phenotypic effect and further points to a complex etiology of KTCN.
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Affiliation(s)
- Justyna A Karolak
- Chair and Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland
| | - Tomasz Gambin
- Institute of Computer Science, Warsaw University of Technology, Warsaw, Poland
| | | | - Piotr Polakowski
- Department of Ophthalmology, Medical University of Warsaw, Warsaw, Poland
| | - Rafal Ploski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Jacek P Szaflik
- Department of Ophthalmology, Medical University of Warsaw, Warsaw, Poland
| | - Marzena Gajecka
- Chair and Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland
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16
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McKay TB, Priyadarsini S, Karamichos D. Mechanisms of Collagen Crosslinking in Diabetes and Keratoconus. Cells 2019; 8:cells8101239. [PMID: 31614631 PMCID: PMC6830090 DOI: 10.3390/cells8101239] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/09/2019] [Accepted: 10/10/2019] [Indexed: 12/14/2022] Open
Abstract
Collagen crosslinking provides the mechanical strength required for physiological maintenance of the extracellular matrix in most tissues in the human body, including the cornea. Aging and diabetes mellitus (DM) are processes that are both associated with increased collagen crosslinking that leads to increased corneal rigidity. By contrast, keratoconus (KC) is a corneal thinning disease associated with decreased mechanical stiffness leading to ectasia of the central cornea. Studies have suggested that crosslinking mediated by reactive advanced glycation end products during DM may protect the cornea from KC development. Parallel to this hypothesis, riboflavin-mediated photoreactive corneal crosslinking has been proposed as a therapeutic option to halt the progression of corneal thinning by inducing intra- and intermolecular crosslink formation within the collagen fibrils of the stroma, leading to stabilization of the disease. Here, we review the pathobiology of DM and KC in the context of corneal structure, the epidemiology behind the inverse correlation of DM and KC development, and the chemical mechanisms of lysyl oxidase-mediated crosslinking, advanced glycation end product-mediated crosslinking, and photoreactive riboflavin-mediated corneal crosslinking. The goal of this review is to define the biological and chemical pathways important in physiological and pathological processes related to collagen crosslinking in DM and KC.
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Affiliation(s)
- Tina B McKay
- Schepens Eye Research Institute/Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
| | - Shrestha Priyadarsini
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Science Center, Oklahoma City, OK 73104, USA.
| | - Dimitrios Karamichos
- Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Science Center, Oklahoma City, OK 73104, USA.
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17
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Sharif R, Bak-Nielsen S, Hjortdal J, Karamichos D. Pathogenesis of Keratoconus: The intriguing therapeutic potential of Prolactin-inducible protein. Prog Retin Eye Res 2018; 67:150-167. [PMID: 29758268 PMCID: PMC6235698 DOI: 10.1016/j.preteyeres.2018.05.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 04/25/2018] [Accepted: 05/08/2018] [Indexed: 12/15/2022]
Abstract
Keratoconus (KC) is the most common ectatic corneal disease, with clinical findings that include discomfort, visual disturbance and possible blindness if left untreated. KC affects approximately 1:400 to 1:2000 people worldwide, including both males and females. The aetiology and onset of KC remains a puzzle and as a result, the ability to treat or reverse the disease is hampered. Sex hormones are known to play a role in the maintenance of the structure and integrity of the human cornea. Hormone levels have been reported to alter corneal thickness, curvature, and sensitivity during different times of menstrual cycle. Surprisingly, the role of sex hormones in corneal diseases and KC has been largely neglected. Prolactin-induced protein, known to be regulated by sex hormones, is a new KC biomarker that has been recently proposed. Studies herein discuss the role of sex hormones as a control mechanism for KC onset and progression and evidence supporting the view that prolactin-induced protein is an important hormonally regulated biomarker in KC is discussed.
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Affiliation(s)
- Rabab Sharif
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, United States
| | - Sashia Bak-Nielsen
- Department of Ophthalmology, Aarhus University Hospital, Aarhus DK-8200, Denmark
| | - Jesper Hjortdal
- Department of Ophthalmology, Aarhus University Hospital, Aarhus DK-8200, Denmark
| | - Dimitrios Karamichos
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 975 NE 10th Street, Oklahoma City, OK 73104, United States; Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Science Center, 608 Stanton L. Young Blvd, Oklahoma City, OK 73104, United States.
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18
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19
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Koc M, Tekin K, Inanc M, Kosekahya P, Yilmazbas P. Crab claw pattern on corneal topography: pellucid marginal degeneration or inferior keratoconus? Eye (Lond) 2017; 32:11-18. [PMID: 28937143 DOI: 10.1038/eye.2017.198] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 08/01/2017] [Indexed: 11/09/2022] Open
Abstract
PurposeTo evaluate the topographic, tomographic, and densitometric properties of patients with pellucid marginal degeneration (PMD) and inferior keratoconus.Patients and methodsRetrospective, comparative case series. Forty-seven eyes of 32 patients with crab claw patterns were identified from 2751 patients with corneal ectasia. They were divided into two groups, inferior keratoconus and PMD, based on clinical findings. The topographic, tomographic, and densitometric measurements were analyzed.ResultsPMD was detected in 11 eyes of eight patients (mean age 50.2±11.1 years), and inferior keratoconus was detected in 36 eyes of 24 patients (mean age 34.7±10.1 years). The control group consisted of 40 patients (33.1±4.6 years). The thinnest corneal point and maximum anterior and posterior elevation points were located lower in the PMD than in the inferior keratoconus (P<0.01). In the PMD, all deviation indices were higher than the controls (P<0.01), whereas the deviation indices, except Dt (P=0.960), were lower than the inferior keratoconus (P<0.01). The densitometry values of PMD were significantly higher than those of the controls in all zones and layers (P<0.01) and significantly higher than the densitometry values of inferior keratoconus in the 6-10 and 10-12 mm zones (P<0.05).ConclusionThere is a higher probability of a patient with crab claw pattern on the topography of having inferior keratoconus than having PMD. Therefore, analyzing only the anterior corneal surface is not sufficient in differential diagnosis. Tomographic and densitometric evaluations may facilitate the differential diagnosis.
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Affiliation(s)
- M Koc
- Department of Ophthalmology, Ulucanlar Eye Training and Research Hospital, Ankara, Turkey
| | - K Tekin
- Department of Ophthalmology, Ulucanlar Eye Training and Research Hospital, Ankara, Turkey
| | - M Inanc
- Department of Ophthalmology, Ulucanlar Eye Training and Research Hospital, Ankara, Turkey
| | - P Kosekahya
- Department of Ophthalmology, Ulucanlar Eye Training and Research Hospital, Ankara, Turkey
| | - P Yilmazbas
- Department of Ophthalmology, Ulucanlar Eye Training and Research Hospital, Ankara, Turkey
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20
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White TL, Lewis PN, Young RD, Kitazawa K, Inatomi T, Kinoshita S, Meek KM. Elastic microfibril distribution in the cornea: Differences between normal and keratoconic stroma. Exp Eye Res 2017; 159:40-48. [PMID: 28315339 PMCID: PMC5451143 DOI: 10.1016/j.exer.2017.03.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 02/15/2017] [Accepted: 03/12/2017] [Indexed: 11/28/2022]
Abstract
The optical and biomechanical properties of the cornea are largely governed by the collagen-rich stroma, a layer that represents approximately 90% of the total thickness. Within the stroma, the specific arrangement of superimposed lamellae provides the tissue with tensile strength, whilst the spatial arrangement of individual collagen fibrils within the lamellae confers transparency. In keratoconus, this precise stromal arrangement is lost, resulting in ectasia and visual impairment. In the normal cornea, we previously characterised the three-dimensional arrangement of an elastic fiber network spanning the posterior stroma from limbus-to-limbus. In the peripheral cornea/limbus there are elastin-containing sheets or broad fibers, most of which become microfibril bundles (MBs) with little or no elastin component when reaching the central cornea. The purpose of the current study was to compare this network with the elastic fiber distribution in post-surgical keratoconic corneal buttons, using serial block face scanning electron microscopy and transmission electron microscopy. We have demonstrated that the MB distribution is very different in keratoconus. MBs are absent from a region of stroma anterior to Descemet's membrane, an area that is densely populated in normal cornea, whilst being concentrated below the epithelium, an area in which they are absent in normal cornea. We contend that these latter microfibrils are produced as a biomechanical response to provide additional strength to the anterior stroma in order to prevent tissue rupture at the apex of the cone. A lack of MBs anterior to Descemet's membrane in keratoconus would alter the biomechanical properties of the tissue, potentially contributing to the pathogenesis of the disease.
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Affiliation(s)
- Tomas L White
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - Philip N Lewis
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - Robert D Young
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - Koji Kitazawa
- Department of Ophthalmology, Kyoto Prefectural University, Kyoto, Japan; Department of Frontier Medical Science and Technology for Ophthalmology, Kyoto Prefectural University, Kyoto, Japan
| | - Tsutomu Inatomi
- Department of Ophthalmology, Kyoto Prefectural University, Kyoto, Japan
| | - Shigeru Kinoshita
- Department of Frontier Medical Science and Technology for Ophthalmology, Kyoto Prefectural University, Kyoto, Japan
| | - Keith M Meek
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK.
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21
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Alkanaan A, Barsotti R, Kirat O, Almubrad T, Khan A, Akhtar S. Ultrastructural study of peripheral and central stroma of keratoconus cornea. Br J Ophthalmol 2017; 101:845-850. [PMID: 28416495 DOI: 10.1136/bjophthalmol-2016-309834] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/02/2017] [Accepted: 02/28/2017] [Indexed: 11/03/2022]
Abstract
PURPOSE Assess the lamellar organisation of the peripheral and central stroma of the keratoconus (KC) and normal cornea. METHODS Five normal and three KC corneas were fixed in 2.5% glutaraldehyde and processed for electron microscopy. The ultrathin sections were observed under JEOL 1400 TEM, and digital images were taken with a bottom-mounted 11-megapixel Quamisa camera, using the iTEM software. Measurements of the lamellae were carried out using the iTEM software. Statistical analysis was performed using the SPSS software. RESULTS The lamellar organisation at the centre and periphery of the KC cornea was disrupted by the presence of multiple undulations, which were more aggressive at the posterior stroma. Among the KC cornea, the mean lamellar thickness of the peripheral middle (1030.32±86.25 nm) and posterior (615.68±30.94 nm) stroma was also significantly (p<0.05) thinner than their corresponding areas of the central KC cornea (1151.1±48 nm; 783.57±31.10 nm). At the periphery of KC cornea, just above the Descemet's membrane (DM), small undulations appeared to emerge out from the DM. Furthermore, the anterior stroma of the peripheral cornea contained several lamellar sutures. The mean lamellar thickness of the peripheral and central KC cornea was significantly (p<0.0001) thinner than the corresponding areas of the normal cornea. CONCLUSION The present study reveals the involvement of lamellae in the peripheral stroma in the pathogenicity of the KC cornea. The emergence of small undulations in the DM suggests that the formation of undulation might be starting from the DM.
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Affiliation(s)
- Aljoharah Alkanaan
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Robert Barsotti
- Department of Biomedical Science, Salus University, Philadelphia, Pennsylvania, USA
| | - Omar Kirat
- Department of Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
| | - Turki Almubrad
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Adnan Khan
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Saeed Akhtar
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
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Kabza M, Karolak JA, Rydzanicz M, Szcześniak MW, Nowak DM, Ginter-Matuszewska B, Polakowski P, Ploski R, Szaflik JP, Gajecka M. Collagen synthesis disruption and downregulation of core elements of TGF-β, Hippo, and Wnt pathways in keratoconus corneas. Eur J Hum Genet 2017; 25:582-590. [PMID: 28145428 DOI: 10.1038/ejhg.2017.4] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 11/16/2016] [Accepted: 12/24/2016] [Indexed: 12/13/2022] Open
Abstract
To understand better the factors contributing to keratoconus (KTCN), we performed comprehensive transcriptome profiling of human KTCN corneas for the first time using an RNA-Seq approach. Twenty-five KTCN and 25 non-KTCN corneas were enrolled in this study. After RNA extraction, total RNA libraries were prepared and sequenced. The discovery RNA-Seq analysis (in eight KTCN and eight non-KTCN corneas) was conducted first, after which the replication RNA-Seq experiment was performed on a second set of samples (17 KTCN and 17 non-KTCN corneas). Over 82% of the genes and almost 75% of the transcripts detected as differentially expressed in KTCN and non-KTCN corneas were confirmed in the replication study using another set of samples. We used these differentially expressed genes to generate a network of KTCN-deregulated genes. We found an extensive disruption of collagen synthesis and maturation pathways, as well as downregulation of the core elements of the TGF-β, Hippo, and Wnt signaling pathways influencing corneal organization. This first comprehensive transcriptome profiling of human KTCN corneas points further to a complex etiology of KTCN.
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Affiliation(s)
- Michal Kabza
- Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Department of Bioinformatics, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University in Poznan, Poznan, Poland
| | - Justyna A Karolak
- Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland
| | | | - Michał W Szcześniak
- Department of Bioinformatics, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University in Poznan, Poznan, Poland
| | - Dorota M Nowak
- Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland
| | - Barbara Ginter-Matuszewska
- Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland
| | - Piotr Polakowski
- Department of Ophthalmology, Medical University of Warsaw, Warsaw, Poland
| | - Rafal Ploski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Jacek P Szaflik
- Department of Ophthalmology, Medical University of Warsaw, Warsaw, Poland
| | - Marzena Gajecka
- Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Poznan, Poland.,Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland
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Molecular and Histopathological Changes Associated with Keratoconus. BIOMED RESEARCH INTERNATIONAL 2017; 2017:7803029. [PMID: 28251158 PMCID: PMC5303843 DOI: 10.1155/2017/7803029] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 12/16/2016] [Accepted: 01/04/2017] [Indexed: 12/13/2022]
Abstract
Keratoconus (KC) is a corneal thinning disorder that leads to loss of visual acuity through ectasia, opacity, and irregular astigmatism. It is one of the leading indicators for corneal transplantation in the Western countries. KC usually starts at puberty and progresses until the third or fourth decade; however its progression differs among patients. In the keratoconic cornea, all layers except the endothelium have been shown to have histopathological structural changes. Despite numerous studies in the last several decades, the mechanisms of KC development and progression remain unclear. Both genetic and environmental factors may contribute to the pathogenesis of KC. Many previous articles have reviewed the genetic aspects of KC, but in this review we summarize the histopathological features of different layers of cornea and discuss the differentially expressed proteins in the KC-affected cornea. This summary will help emphasize the major molecular defects in KC and identify additional research areas related to KC, potentially opening up possibilities for novel methods of KC prevention and therapeutic intervention.
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Puell MC, Carballo-Álvarez J. Forward light scatter and visual acuity before and after intrastromal corneal ring segment implantation at different stages of keratoconus. Acta Ophthalmol 2016; 94:e738-e743. [PMID: 27129433 DOI: 10.1111/aos.13056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 02/15/2016] [Indexed: 12/01/2022]
Abstract
PURPOSE To assess forward light scatter (stray light) before and after intrastromal corneal ring segment (ICRS) implantation at different stages of keratoconus and to examine correlation between postoperative stray light and visual acuity (VA). METHODS In 27 eyes of 27 subjects with keratoconus, stray light was determined using the compensation comparison technique before and 6 months after ICRS implantation. Monocular corrected distance VA (CDVA) was measured using a high-contrast logMAR letter chart. Corneal higher-order aberrations (HOAs), contrast sensitivity (CS) and minimum corneal thickness (CT) were also measured. RESULTS Mean CDVA was 0.42 ± 0.28 preoperatively and 0.24 ± 0.15 logMAR postoperatively (p < 0.01). Mean corneal coma-like aberration decreased postoperatively (RMS 0.55 ± 1.18 μm, p < 0.01). Minimum CT increased 25.31 ± 18.59 μm (p < 0.01). Mean preoperative and postoperative stray light were 1.36 ± 0.31 and 1.48 ± 0.32 log units, respectively (p < 0.01). Mean changes produced in stray light (worsening) were 0.03 ± 0.21 (p > 0.05) for stage I, 0.13 ± 0.14 (p = 0.013) for stage II and 0.18 ± 0.21 (p = 0.023) for stage III. Significant positive correlation (r = 0.47, p = 0.01) was detected between postoperative stray light and postoperative CDVA such that as stray light increased, CDVA worsened (higher logMAR values). Postoperative stray light was neither associated with HOAs, CS nor minimum CT. CONCLUSIONS Stray light values in these patients with keratoconus were higher than normal preoperatively. In eyes with stage II and III keratoconus, stray light increased 6 months after ICRS placement. Higher postoperative stray light was correlated with a worse visual acuity outcome.
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Affiliation(s)
- María Cinta Puell
- Applied Vision Research Group; Faculty of Optics and Optometry; Complutense University of Madrid; Madrid Spain
| | - Jesús Carballo-Álvarez
- Applied Vision Research Group; Faculty of Optics and Optometry; Complutense University of Madrid; Madrid Spain
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Godefrooij DA, Gans R, Imhof SM, Wisse RP. Trends in penetrating and anterior lamellar corneal grafting techniques for keratoconus: a national registry study. Acta Ophthalmol 2016; 94:489-93. [PMID: 27061780 DOI: 10.1111/aos.13041] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 02/04/2016] [Indexed: 11/27/2022]
Abstract
PURPOSE Keratoconus is a progressive disorder and one of the primary indications for corneal transplantation. Anterior lamellar keratoplasty offers several advantages over other techniques, including endothelial preservation and longer graft survival. In this study, we examined the recent trend of using lamellar techniques for keratoconus at a national level. METHODS Data were obtained from the Dutch national organ transplant database regarding corneal transplants for keratoconus performed in 2005 through 2014. Baseline characteristics for patients undergoing various techniques were obtained, and temporal trends were analysed. RESULTS A total of 1041 operations were performed, including 736 penetrating keratoplasties (PKPs) and 297 anterior lamellar keratoplasties (ALKs). The mean age of the total surgical group was 37.4 ± 13.4 years, and 68% of patients were male (p = 0.0001). Preoperative patient characteristics were reported in all 1041 cases. The relative proportion of ALKs increased from 2005 (19% of cases) to 2010 (39% of cases) and remained approximately 30-40% thereafter. Descemet baring or deep anterior lamellar keratoplasty (DALK) was increasingly applied and was the predominant anterior lamellar technique performed from 2009 onwards. CONCLUSIONS The number of corneal transplantations performed annually for keratoconus decreased during the past 10 years. Lamellar techniques were increasingly performed, accounting for approximately 35% of keratoplasties in 2010 and thereafter. Among ALK techniques, maximal depth DALK is the most prevalent keratoplasty performed for keratoconus in most recent years. Penetrating keratoplasty (PKP) is still common, with a stable frequency from 2010 onwards.
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Affiliation(s)
- Daniel A. Godefrooij
- Utrecht Cornea Research Group; Department of Ophthalmology; University Medical Center Utrecht; Utrecht The Netherlands
| | - Renze Gans
- Utrecht Cornea Research Group; Department of Ophthalmology; University Medical Center Utrecht; Utrecht The Netherlands
| | - Saskia M. Imhof
- Utrecht Cornea Research Group; Department of Ophthalmology; University Medical Center Utrecht; Utrecht The Netherlands
| | - Robert P.L. Wisse
- Utrecht Cornea Research Group; Department of Ophthalmology; University Medical Center Utrecht; Utrecht The Netherlands
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