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Chiang JCB, Roy M, Kim J, Markoulli M, Krishnan AV. In-vivo corneal confocal microscopy: Imaging analysis, biological insights and future directions. Commun Biol 2023; 6:652. [PMID: 37336941 DOI: 10.1038/s42003-023-05005-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 05/31/2023] [Indexed: 06/21/2023] Open
Abstract
In-vivo corneal confocal microscopy is a powerful imaging technique which provides clinicians and researcher with the capabilities to observe microstructures at the ocular surfaces in significant detail. In this Mini Review, the optics and image analysis methods with the use of corneal confocal microscopy are discussed. While novel insights of neuroanatomy and biology of the eyes, particularly the ocular surface, have been provided by corneal confocal microscopy, some debatable elements observed using this technique remain and these are explored in this Mini Review. Potential improvements in imaging methodology and instrumentation are also suggested.
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Affiliation(s)
- Jeremy Chung Bo Chiang
- School of Optometry and Vision Science, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW, Australia
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, NSW, UK
| | - Maitreyee Roy
- School of Optometry and Vision Science, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW, Australia
| | - Juno Kim
- School of Optometry and Vision Science, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW, Australia
| | - Maria Markoulli
- School of Optometry and Vision Science, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW, Australia
| | - Arun V Krishnan
- School of Clinical Medicine, University of New South Wales, Sydney, NSW, Australia.
- Department of Neurology, Prince of Wales Hospital, Sydney, NSW, Australia.
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Posarelli M, Chirapapaisan C, Muller R, Abbouda A, Pondelis N, Cruzat A, Cavalcanti BM, Cox SM, Jamali A, Pavan-Langston D, Hamrah P. Corneal nerve regeneration is affected by scar location in herpes simplex keratitis: A longitudinal in vivo confocal microscopy study. Ocul Surf 2023; 28:42-52. [PMID: 36646165 DOI: 10.1016/j.jtos.2023.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 10/28/2022] [Accepted: 01/12/2023] [Indexed: 01/15/2023]
Abstract
PURPOSE To assess the effect of corneal scar location on corneal nerve regeneration in patients with herpes simplex virus (HSV) keratitis in their affected and contralateral eyes over a 1-year period by in vivo confocal microscopy (IVCM), and to correlate these findings to corneal sensation measured by Cochet-Bonnet Esthesiometer. METHODS Prospective, longitudinal, case-control study. Bilateral corneal nerve density and corneal sensation were analyzed centrally and peripherally in 24 healthy controls and 23 patients with unilateral HSV-related corneal scars using IVCM. RESULTS In the central scar (CS) group, total nerve density in the central cornea remained significantly lower compared to controls at follow-up (11.05 ± 1.97mm/mm2, p < 0.001), and no significant nerve regeneration was observed (p = 0.090). At follow-up, total nerve density was not significantly different from controls in the central and peripheral cornea of the peripheral scar (PS) group (all p > 0.05), but significant nerve regeneration was observed in central corneas (16.39 ± 2.39mm/mm2, p = 0.007) compared to baseline. In contralateral eyes, no significant corneal nerve regeneration was observed in central or peripheral corneas of patients with central scars or peripheral scars at 1-year follow-up, compared to baseline (p > 0.05). There was a positive correlation between corneal nerve density and sensation in both central (R = 0.53, p < 0.0001) and peripheral corneas (R = 0.27, p = 0.0004). In the CS group, the corneal sensitivity was <4 cm in 4 (30.8%) and 7 (53.8%) patients in the central and peripheral corneas at baseline, and in 5 (38.5%) and 2 subjects (15.4%) at follow-up, whereas in the PS group only 1 patient (10%) showed a corneal sensation < 4 cm in the central cornea at baseline, and only 1 (10.0%), 3 (30.0%) and 1 (10.0%) patients at follow-up in the central, affected and opposite area of the cornea, respectively. CONCLUSION The location of HSV scarring in the cornea affects the level of corneal nerve regeneration. Eyes with central corneal scar have a diminished capacity to regenerate nerves in central cornea, show a more severe reduction in corneal sensation in the central and peripheral corneas that persist at follow-up, and have a reduced capability to restore the corneal sensitivity above the cut-off of 4 cm. Thus, clinicians should be aware that CS patients would benefit from closer monitoring for potential complications associated with neurotrophic keratopathy, as they have a lower likelihood for nerve regeneration.
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Affiliation(s)
- Matteo Posarelli
- Center for Translational Ocular Immunology, USA; Cornea Service, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, USA
| | - Chareenun Chirapapaisan
- Ocular Surface Imaging Center, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Rodrigo Muller
- Center for Translational Ocular Immunology, USA; Cornea Service, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, USA; Ocular Surface Imaging Center, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Alessandro Abbouda
- Center for Translational Ocular Immunology, USA; Cornea Service, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, USA
| | | | - Andrea Cruzat
- Ocular Surface Imaging Center, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Department of Ophthalmology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Bernardo M Cavalcanti
- Ocular Surface Imaging Center, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | | | - Arsia Jamali
- Center for Translational Ocular Immunology, USA; Ocular Surface Imaging Center, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Deborah Pavan-Langston
- Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Pedram Hamrah
- Center for Translational Ocular Immunology, USA; Cornea Service, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, USA; Ocular Surface Imaging Center, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; Cornea Service, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
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Chirapapaisan C, Thongsuwan S, Chirapapaisan N, Chonpimai P, Veeraburinon A. Characteristics of Corneal Subbasal Nerves in Different Age Groups: An in vivo Confocal Microscopic Analysis. Clin Ophthalmol 2021; 15:3563-3572. [PMID: 34465977 PMCID: PMC8403225 DOI: 10.2147/opth.s324169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 08/11/2021] [Indexed: 01/03/2023] Open
Abstract
Purpose To determine the normative characteristics of corneal subbasal nerves in different age groups using laser scanning in vivo confocal microscopy (IVCM). Patients and Methods This descriptive observational study recruited healthy subjects (aged 20–60 years) from Siriraj Health-Screening Center. Excluded were individuals who had abnormal ocular symptoms, previous ocular surgery, a history of any diseases related to systemic and/or corneal neuropathy, or abnormal corneal sensitivity. Corneal IVCM (HRT3/Rostock Corneal Module) was performed at the central cornea to analyze the subbasal nerve plexus. The corneal nerve characteristics, comprising the number and density of nerves (main nerve trunks, branches, and total nerves) were analyzed using the NeuronJ program, and the corneal nerve tortuosity was graded. The correlations between the subbasal nerve density, tortuosity and age were then analyzed. Results Eighty subjects were enrolled, with twenty in each of four age groups (20–30, >30–40, >40–50, and >50–60 years). Overall, the mean number and density of main nerve trunks were 27.93±0.81/mm2 and 11.22±0.30 mm/mm2, respectively. As of the nerve branches, the average number and density were 103.56±2.37/mm2 and 9.15±0.30 mm/mm2, respectively. The total nerve density was 20.37±0.39 mm/mm2. There were no significant differences between subbasal nerve parameters of the four age groups. It is noteworthy that 65% of the subjects aged over 40 years revealed high-grade nerve tortuosity. Conclusion The corneal subbasal nerve numbers and densities were not significantly different among a healthy population aged 20–60 years. However, there was a trend towards high tortuosity of the corneal nerve in people aged over 40 years.
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Affiliation(s)
- Chareenun Chirapapaisan
- Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Sittiphong Thongsuwan
- Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Niphon Chirapapaisan
- Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Pratuangsri Chonpimai
- Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Anupong Veeraburinon
- Research Division, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailanda
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Herrera-Pereda R, Taboada Crispi A, Babin D, Philips W, Holsbach Costa M. A Review On digital image processing techniques for in-Vivo confocal images of the cornea. Med Image Anal 2021; 73:102188. [PMID: 34340102 DOI: 10.1016/j.media.2021.102188] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 06/12/2021] [Accepted: 07/16/2021] [Indexed: 12/27/2022]
Abstract
This work reviews the scientific literature regarding digital image processing for in vivo confocal microscopy images of the cornea. We present and discuss a selection of prominent techniques designed for semi- and automatic analysis of four areas of the cornea (epithelium, sub-basal nerve plexus, stroma and endothelium). The main context is image enhancement, detection of structures of interest, and quantification of clinical information. We have found that the preprocessing stage lacks of quantitative studies regarding the quality of the enhanced image, or its effects in subsequent steps of the image processing. Threshold values are widely used in the reviewed methods, although generally, they are selected empirically and manually. The image processing results are evaluated in many cases through comparison with gold standards not widely accepted. It is necessary to standardize values to be quantified in terms of sensitivity and specificity of methods. Most of the reviewed studies do not show an estimation of the computational cost of the image processing. We conclude that reliable, automatic, computer-assisted image analysis of the cornea is still an open issue, constituting an interesting and worthwhile area of research.
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Affiliation(s)
- Raidel Herrera-Pereda
- Departamento de Bioinformática, Facultad de Ciencias y Tecnologías Computacionales, Universidad de las Ciencias Informáticas (UCI), Carretera a San Antonio de los Baños Km 2 1/2, Torrens, Boyeros, La Habana, Cuba; TELIN-IPI, Ghent University - imec, Belgium.
| | - Alberto Taboada Crispi
- Centro de Investigaciones de la Informática, Universidad Central "Marta Abreu" de Las Villas (UCLV), Carretera a Camajuaní, km 5 1/2, Santa Clara, VC, CP 54830, Cuba
| | | | | | - Márcio Holsbach Costa
- Department of Electrical and Electronic Engineering, Federal University of Santa Catarina, Florianópolis, SC, Brazil
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Su P, Chen T, Xie J, Zheng Y, Qi H, Borroni D, Zhao Y, Liu J. Corneal nerve tortuosity grading via ordered weighted averaging-based feature extraction. Med Phys 2020; 47:4983-4996. [PMID: 32761618 DOI: 10.1002/mp.14431] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 01/26/2023] Open
Abstract
PURPOSE Tortuosity of corneal nerve fibers acquired by in vivo Confocal Microscopy (IVCM) are closely correlated to numerous diseases. While tortuosity assessment has conventionally been conducted through labor-intensive manual evaluation, this warrants an automated and objective tortuosity assessment of curvilinear structures. This paper proposes a method that extracts the image-level features for corneal nerve tortuosity grading. METHODS For an IVCM image, all corneal nerve fibers are first segmented and then, their tortuosity are calculated by morphological measures. The ordered weighted averaging (OWA) approach, and the k-Nearest-Neighbor guided dependent ordered weighted averaging (kNNDOWA) approach are proposed to aggregate the tortuosity values and form a set of extracted features. This is followed by running the Wrapper method, a supervised feature selection, with an aim to identify the most informative attributes for tortuosity grading. RESULTS Validated on a public and an in-house benchmark data sets, experimental results demonstrate superiority of the proposed method over the conventional averaging and length-weighted averaging methods with performance gain in accuracy (15.44% and 14.34%, respectively). CONCLUSIONS The simultaneous use of multiple aggregation operators could extract the image-level features that lead to more stable and robust results compared with that using average and length-weighted average. The OWA method could facilitate the explanation of derived aggregation behavior through stress functions. The kNNDOWA method could mitigate the effects of outliers in the image-level feature extraction.
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Affiliation(s)
- Pan Su
- Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315300, China.,School of Control and Computer Engineering, North China Electric Power University, Baoding, 071003, China
| | - Tianhua Chen
- School of Computing and Engineering, University of Huddersfield, Huddersfield, HD1 3DH, UK
| | - Jianyang Xie
- Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315300, China
| | - Yalin Zheng
- Department of Eye and Vision Science, University of Liverpool, Liverpool, L69 3BX, UK
| | - Hong Qi
- Department of Ophthalmology, Peking University Third Hospital, Beijing, 100191, China
| | - Davide Borroni
- St. Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, L69 3BX, UK
| | - Yitian Zhao
- Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315300, China
| | - Jiang Liu
- Department of Computer Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
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Tosi GM, Martone G, Bacci T, Tarantello A, Baiocchi S, Marigliani D, Cevenini G, Menicacci F, Virgili G, Massaro-Giordano G. Long-term evaluation of corneal sub-basal nerve recovery after photorefractive keratectomy and influence of pars plana vitrectomy. J Cell Physiol 2018; 234:7459-7466. [PMID: 30417371 DOI: 10.1002/jcp.27504] [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: 08/10/2018] [Accepted: 09/10/2018] [Indexed: 11/12/2022]
Abstract
The corneal sub-basal nerve (SBN) plexus is destroyed during photorefractive keratectomy (PRK) and its recovery is still a matter of debate. In vivo confocal microscopy (IVCM) was used to evaluate SBN plexus in 23 patients at a distance of 10-25 years (mean 15.6 years) from myopic PRK. Because 8 out of the 23 PRK patients underwent pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment, IVCM was also performed on those patients 6 months after PPV. Thirteen patients matched for age and myopia served as controls (non-PRK). SBN plexus was markedly reduced after PRK compared with non-PRK eyes and showed a slow, continuous but incomplete recovery up to the end of our follow-up (range 10-25 years). PRK and non-PRK eyes showed a marked reduction in SBN density 6 months after PPV, thus demonstrating a detrimental effect exerted by PPV on SBN plexus.
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Affiliation(s)
- Gian Marco Tosi
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Gianluca Martone
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Tommaso Bacci
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Antonio Tarantello
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Stefano Baiocchi
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Davide Marigliani
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Gabriele Cevenini
- Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Flavia Menicacci
- Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy
| | - Gianni Virgili
- Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - Giacomina Massaro-Giordano
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania
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Kim J, Markoulli M. Automatic analysis of corneal nerves imaged using in vivo confocal microscopy. Clin Exp Optom 2017; 101:147-161. [PMID: 29193361 DOI: 10.1111/cxo.12640] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/19/2017] [Accepted: 10/12/2017] [Indexed: 12/21/2022] Open
Abstract
Interest has grown over the past decade in using in vivo confocal microscopy to analyse the morphology of corneal nerves and their changes over time. Advances in computational modelling techniques have been applied to automate the estimation of sub-basal nerve structure. These objective methods have the potential to quantify nerve density (and length), tortuosity, variations in nerve thickness, as well as temporal changes in nerve fibres such as migration patterns. Different approaches to automated nerve analysis, methods proposed and how they were validated in previous literature are reviewed. Improved understanding of these approaches and their limitations will help improve the diagnostic leverage of emerging developments for monitoring the onset and progression of a broad class of systemic diseases, including diabetes.
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Affiliation(s)
- Juno Kim
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia
| | - Maria Markoulli
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia
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Harrison WW, Putnam NM, Shukis C, Nguyen E, Reinard K, Hundelt E, Vardanyan G, Gabai C, Yevseyenkov V. The corneal nerve density in the sub-basal plexus decreases with increasing myopia: a pilot study. Ophthalmic Physiol Opt 2017; 37:482-488. [PMID: 28656670 DOI: 10.1111/opo.12366] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 02/01/2017] [Indexed: 12/14/2022]
Abstract
PURPOSE Myopia can cause many changes in the health of the eye. As it becomes more prevalent worldwide, more patients seek correction in the form of glasses, contact lenses and refractive surgery. In this study we explore the impact that high myopia has on central corneal nerve density by comparing sub basal nerve plexus density measured by confocal microscopy in a variety of refractive errors. METHODS Seventy healthy adult subjects between the ages of 21-50 years participated in this study. The study took place in two phases with no overlapping subjects (n = 30 phase 1 and n = 40 phase 2). In both phases an autorefraction, keratometry reading, corneal thickness measure and confocal corneal scan of the sub basal nerve plexus were performed for both eyes. There were 11 hyperopes (+0.50 to +3.50DS), six emmetropes (-0.25 to +0.50DS), 30 low myopes (-5.50 to -0.50DS), and 23 high myopes (-5.50DS and above). In the second phase of the study additional tests were performed including an axial length, additional corneal scans, and a questionnaire that asked about age of first refractive correction and contact lens wear. Corneal nerves were imaged over the central cornea with a Nidek CS4 confocal microscope (460 × 345 μm field). Nerves were evaluated using the NeuronJ program for density calculation. One eye was selected for inclusion based on image quality and higher refractive error (more myopic or hyperopic). RESULTS As myopia increased, nerve density decreased (t1 = 3.86, p < 0.001). We also note a decrease in data scatter above -7 D. The relationship between axial length values and nerve density was also significant and the slope was not as robust as refractive error (t1 = 2.4, p < 0.04). As expected there was a significant difference between the four groups in axial length (F3 = 19.9, p < 0.001) and age of first refractive correction of the myopic groups (14.9 vs 11.5 years; t46 = 2.99 p < 0.01). There was no difference in keratometry readings or corneal thickness between the groups (F3 = 0.6, p = 0.66 and F3 = 1.2, p = 0.33 respectively). CONCLUSION Corneal nerve density in the sub-basal plexus decreased with increasing myopia. This could have implications for corneal surgery and contact lens wear in this patient population.
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Affiliation(s)
- Wendy W Harrison
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Nicole M Putnam
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Christine Shukis
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Evelyn Nguyen
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Kristen Reinard
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Elizabeth Hundelt
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Galina Vardanyan
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
| | - Celine Gabai
- Midwestern University Arizona College of Optometry, Glendale, Arizona, USA
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Cruzat A, Qazi Y, Hamrah P. In Vivo Confocal Microscopy of Corneal Nerves in Health and Disease. Ocul Surf 2017; 15:15-47. [PMID: 27771327 PMCID: PMC5512932 DOI: 10.1016/j.jtos.2016.09.004] [Citation(s) in RCA: 218] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Revised: 09/19/2016] [Accepted: 09/25/2016] [Indexed: 12/20/2022]
Abstract
In vivo confocal microscopy (IVCM) is becoming an indispensable tool for studying corneal physiology and disease. Enabling the dissection of corneal architecture at a cellular level, this technique offers fast and noninvasive in vivo imaging of the cornea with images comparable to those of ex vivo histochemical techniques. Corneal nerves bear substantial relevance to clinicians and scientists alike, given their pivotal roles in regulation of corneal sensation, maintenance of epithelial integrity, as well as proliferation and promotion of wound healing. Thus, IVCM offers a unique method to study corneal nerve alterations in a myriad of conditions, such as ocular and systemic diseases and following corneal surgery, without altering the tissue microenvironment. Of particular interest has been the correlation of corneal subbasal nerves to their function, which has been studied in normal eyes, contact lens wearers, and patients with keratoconus, infectious keratitis, corneal dystrophies, and neurotrophic keratopathy. Longitudinal studies have applied IVCM to investigate the effects of corneal surgery on nerves, demonstrating their regenerative capacity. IVCM is increasingly important in the diagnosis and management of systemic conditions such as peripheral diabetic neuropathy and, more recently, in ocular diseases. In this review, we outline the principles and applications of IVCM in the study of corneal nerves in various ocular and systemic diseases.
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Affiliation(s)
- Andrea Cruzat
- Cornea & Refractive Surgery Service, Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston, MA, USA; Department of Ophthalmology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Yureeda Qazi
- Cornea & Refractive Surgery Service, Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Pedram Hamrah
- Cornea & Refractive Surgery Service, Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston, MA, USA; Boston Image Reading Center, Tufts Medical Center, Tufts University School of Medicine, Boston, MA; Cornea Service, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA.
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Annunziata R, Trucco E. Accelerating Convolutional Sparse Coding for Curvilinear Structures Segmentation by Refining SCIRD-TS Filter Banks. IEEE TRANSACTIONS ON MEDICAL IMAGING 2016; 35:2381-2392. [PMID: 27214893 DOI: 10.1109/tmi.2016.2570123] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Deep learning has shown great potential for curvilinear structure (e.g., retinal blood vessels and neurites) segmentation as demonstrated by a recent auto-context regression architecture based on filter banks learned by convolutional sparse coding. However, learning such filter banks is very time-consuming, thus limiting the amount of filters employed and the adaptation to other data sets (i.e., slow re-training). We address this limitation by proposing a novel acceleration strategy to speed-up convolutional sparse coding filter learning for curvilinear structure segmentation. Our approach is based on a novel initialisation strategy (warm start), and therefore it is different from recent methods improving the optimisation itself. Our warm-start strategy is based on carefully designed hand-crafted filters (SCIRD-TS), modelling appearance properties of curvilinear structures which are then refined by convolutional sparse coding. Experiments on four diverse data sets, including retinal blood vessels and neurites, suggest that the proposed method reduces significantly the time taken to learn convolutional filter banks (i.e., up to -82%) compared to conventional initialisation strategies. Remarkably, this speed-up does not worsen performance; in fact, filters learned with the proposed strategy often achieve a much lower reconstruction error and match or exceed the segmentation performance of random and DCT-based initialisation, when used as input to a random forest classifier.
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