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Patil RP, Shetty R, Khamar P, Patel YG, Narasimhan RR, Bhatkal AA, Hitzenberger CK, Pircher M, Nuijts RMMR, Sinha Roy A. Insights into atypical segmental layer thicknesses and phase retardation in thick corneas using ultrahigh-resolution polarization-sensitive optical coherence tomography. EYE AND VISION (LONDON, ENGLAND) 2024; 11:30. [PMID: 39004731 PMCID: PMC11247896 DOI: 10.1186/s40662-024-00391-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 06/05/2024] [Indexed: 07/16/2024]
Abstract
BACKGROUND Accurately assessing corneal structural status is challenging when thickness deviates from the average. Polarization-sensitive optical coherence tomography (PS-OCT) measures tissue-specific polarization changes, providing additional contrast for accurate segmentations and aids in phase retardation (PR) measurements. Previous studies have shown PR's effectiveness in identifying sub-clinical keratoconus (KC) in asymmetric cases. Thus, this study aims to assess PR distribution in thick corneas with and without KC. METHODS In this retrospective and cross-sectional study, 45 thick corneas from 30 Asian-Indian subjects, categorized into healthy (n = 26) and KC (n = 19) groups were analyzed. All eyes underwent standard clinical evaluations, tomographic assessments, and corneal biomechanics measurements. PR and individual layer thicknesses were measured using custom-designed ultrahigh-resolution PS-OCT. PR en-face maps were generated. Individual layer thicknesses and PR analysis was conducted across multiple zones, extending up to 8-10 mm in diameter. All eyes in the study had not undergone interventions, received topical medications, or had previous corneal disease history. RESULTS Significant differences were found in spherical and cylindrical powers, keratometry, pachymetry, and biomechanical indices (all P < 0.01). Thickness profiles from PS-OCT showed significant differences in the 4-8 mm zones only. Bowman's layer thickness significantly differed only in the central 2 mm zone (P = 0.02). The median PR values showed marginal differences in the central 2 mm zone (P = 0.0565). Additionally, there were significant differences observed in the 2-4 mm and 4-6 mm zones (P = 0.0274 and P = 0.0456, respectively). KC eyes exhibited an atypical PR distribution and corneal thinning, while normal eyes maintained a uniform Bowman's layer thickness and PR maps with larger areas of higher PR. CONCLUSION The study revealed distinctive PR distribution in thick corneas among healthy and KC groups. Using an ultrahigh-resolution PS-OCT the significance of Bowman's layer thickness in these groups was also emphasized. The study offered potential improvements in clinical diagnostics by enhancing our understanding of corneal structure and its altered function.
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Affiliation(s)
- Rahul P Patil
- Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India
- University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Rohit Shetty
- Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India
| | - Pooja Khamar
- Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India
| | - Yash G Patel
- Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India
| | - Raghav R Narasimhan
- Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India
| | - Anushree A Bhatkal
- Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India
| | | | - Michael Pircher
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Rudy M M R Nuijts
- University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Abhijit Sinha Roy
- Imaging, Biomechanics and Mathematical Modelling Solutions Lab, Narayana Nethralaya Foundation, Narayana Nethralaya, Bangalore, India.
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Chittajallu SNSH, Gururani H, Jakati S, Basu S, Vaddavalli PK, Tse KM, Chinthapenta V. Investigation of mechanical strength and structure of corneal graft-host junction. Heliyon 2024; 10:e30871. [PMID: 38784531 PMCID: PMC11112333 DOI: 10.1016/j.heliyon.2024.e30871] [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: 01/20/2024] [Accepted: 05/07/2024] [Indexed: 05/25/2024] Open
Abstract
Dehiscence is a common complication of corneal transplant surgery involving separating the graft from the host eye. The present article aims to investigate fundamental insights into the mechanical and structural aspects of the graft-host junction (GHJ) of a graft that survived in a patient for 13 years after penetrating keratoplasty (PK). Additionally, it adopts the sutur retention strength (SRS) test procedure defined in ISO:7198-2016 and aims to provide a comprehensive test protocol to study the biomechanics of the GHJ in extracted PK buttons. A 9 mm corneal button with GHJ was extracted from a 46-year-old patient who underwent PK 13 years back. The strength of the GHJ was quantified using the SRS test. Corresponding control results were obtained from the SRS tests of a corneoscleral button with no history of any refractive procedure. Birefringence, histological, and scanning electron microscopy (SEM) imaging were used to visualize the microstructural details of the GHJ. The strength of the GHJ was observed to be ten times lower than the native cornea. Histopathological features, such as fragmented Bowman's layer, and fibrosis with a clear demarcation line between host and graft tissue, were observed at the GHJ, suggesting a weak bond across the GHJ. The low strength of the GHJ in PK indicates the high susceptibility of the GHJ towards wound dehiscence.
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Affiliation(s)
- Sai Naga Sri Harsha Chittajallu
- Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India
- Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Melbourne, Australia
- Centre for Technology Innovation, L V Prasad Eye Institute, Hyderabad, India
| | - Himanshu Gururani
- Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India
| | - Saumya Jakati
- Ophthalmic Pathology Laboratory, LV Prasad Eye Institute, Hyderabad, India
| | - Sayan Basu
- Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, LV Prasad Eye Institute, Hyderabad, India
| | | | - Kwong Ming Tse
- Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Melbourne, Australia
| | - Viswanath Chinthapenta
- Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Hyderabad, India
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Manumuraleekrishna, Asif MI, Maharana PK, Nagpal R, Agarwal T, Sinha R, Titiyal JS, Sharma N. Comparative evaluation of biomechanical changes and aberration profile following accelerated collagen cross-linking using hypo-osmolar and iso-osmolar riboflavin: A prospective study. Indian J Ophthalmol 2024; 72:712-717. [PMID: 38648433 PMCID: PMC11168534 DOI: 10.4103/ijo.ijo_1387_23] [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: 05/28/2023] [Revised: 09/30/2023] [Accepted: 10/26/2023] [Indexed: 04/25/2024] Open
Abstract
PURPOSE To compare the changes encountered in corneal biomechanics and aberration profile following accelerated corneal collagen cross-linking (CXL) using hypo-osmolar and iso-osmolar riboflavin in corneal thicknesses of <400 and >400 microns, respectively. METHODS This is a prospective, interventional, comparative study involving 100 eyes of 75 patients with progressive keratoconus. Eyes were divided into two groups based on corneal thickness: group 1 included eyes with a corneal thickness of <400 microns who underwent hypo-osmolar CXL, and group 2 included eyes with a corneal thickness of >400 microns who underwent iso-osmolar CXL. Corneal biomechanical and aberration profiles were evaluated and compared between groups. RESULTS In group 1, all higher-order aberrations (HOA) except secondary astigmatism significantly decreased from baseline; however, in group 2, only coma and trefoil decreased. The corneal resistance factor and corneal hysteresis significantly improved in both groups, which was significantly greater in group 2 than in group 1. The change in inverse radius, deformation amplitude, and tomographic biomechanical index was significantly improved in group 2 as compared to group 1. CONCLUSION Improvement in corrected distance visual acuity and decrease in HOA were significantly better in the hypo-osmolar CXL group; however, the improvement in biomechanical strength of the cornea was significantly better in the iso-osmolar group.
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Affiliation(s)
- Manumuraleekrishna
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Mohamed Ibrahime Asif
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Prafulla Kumar Maharana
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Ritu Nagpal
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Tushar Agarwal
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Rajesh Sinha
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Jeewan Singh Titiyal
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Namrata Sharma
- Department of Ophthalmology, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
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Gururani H, Chittajallu SNSH, Doulatramani M, Manoharan R, Basu S, Chinthapenta V. Intraoperative collagen imaging of sutured cornea: A way towards managing post-penetrating keratoplasty astigmatism. Med Eng Phys 2024; 123:104076. [PMID: 38365329 DOI: 10.1016/j.medengphy.2023.104076] [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: 04/10/2023] [Revised: 11/28/2023] [Accepted: 12/03/2023] [Indexed: 02/18/2024]
Abstract
The birefringent nature of the human cornea plays an important role in comprehending its structural behavior in both diseased and surgical conditions. During corneal transplantation, irregular astigmatism is a common post-surgical complication that depends on the characteristics of suturing. Four human cadaver corneas are subjected to an in-vitro model of a typical full-thickness penetrating keratoplasty (PK) procedure using 16 simple interrupted 10-0 vicyrl sutures. The birefringence of these four corneas is analyzed using digital photoelasticity and compared with the control cornea (without PK). It is found that the sutures and their mutual interaction influence the morphology of the peripheral birefringence of the cornea. The findings of the present investigation are pertinent to intraoperative suture management during PK. Results suggest conserving the typical diamond-shaped morphology of peripheral birefringence would ensure uniform distribution of sutures. Therefore, birefringence imaging could be useful in suture management to ensure proper apposition of the graft-host junction, thus minimizing the risk of irregular astigmatism.
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Affiliation(s)
| | - Sai Naga Sri Harsha Chittajallu
- Micro-Mechanics Lab, IIT Hyderabad, Kandi, Sangareddy 502284, India; Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad 500034, India
| | | | - Ramji Manoharan
- Engineering Optics Lab, IIT Hyderabad, Kandi, Sangareddy 502284, India
| | - Sayan Basu
- Prof. Brien Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad 500034, India; The Cornea Institute, LV Prasad Eye Institute, Hyderabad 500034, India
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Francis M, Matalia H, John AA, Matalia J, Chinnappaiah N, Bhandary P, Shetty R, Nuijts RMMA, Sinha Roy A. Minimum Corneal Diameter and Anterior Steep Axis Curvature Share the Same Meridian: A Novel Finding. Am J Ophthalmol 2023; 256:175-185. [PMID: 37669730 DOI: 10.1016/j.ajo.2023.08.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/25/2023] [Accepted: 08/25/2023] [Indexed: 09/07/2023]
Abstract
PURPOSE To define the external scleral sulcus (ESS) on a Scheimpflug image and use it for a morphometric analysis of corneal diameter (CD). DESIGN Retrospective, cross-sectional study of pediatric Asian-Indian eyes. METHODS One random eye of 353 subjects between 5 and 18 years underwent 25-scan Pentacam HR imaging. For all scans, densitometry values along the anterior corneal edge were recorded and differentiated. The peaks on the differentiated curve were chosen as the ESS points, and this distance between them was called CD. Vertical (vCD), maximum (maxCD), minimum (minCD) CD and their meridians were defined. Multiple regression models (MRMs) with CD and other Pentacam parameters were built to predict astigmatism and its axis, mean keratometry (Kmean), and Belin/Ambrósio enhanced ectasia display deviation (BAD-D). MRMs were validated using intraclass correlation coefficient (ICC). Estimated horizontal CD (hCD) was validated against digital caliper measurement using ICC. RESULTS The ICC (95% CI) between caliper and hCD was 0.96 (0.93, 0.97). MRM predictions (P < .001) used CD parameters, anterior chamber depth, corneal volume and distance from the corneal thinnest location to apex. These predictions achieved an ICC of 0.34 (0.18, 0.46), 0.82 (0.78, 0.86), 0.87 (0.84, 0.89), and 0.81 (0.76, 0.84), respectively. The astigmatism axis prediction depended on the minCD and maxCD meridians. Its within-subject SD (4.97°) was less than 2 consecutive Pentacam scan angles (7.2°). CONCLUSIONS The CD metric strongly correlated with the astigmatism axis, keratometry, and BAD-D. Its spatial description may be significant in corneal treatment planning and disease diagnoses.
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Affiliation(s)
- Mathew Francis
- From the Imaging, Biomechanics and Mathematical Modelling Solutions, Narayana Nethralaya Foundation (M.F., A.S.R.), Bangalore, India; Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India
| | - Himanshu Matalia
- Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India
| | - Ansu Ann John
- Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India
| | - Jyoti Matalia
- Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India
| | - Nandini Chinnappaiah
- Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India
| | - Prarthana Bhandary
- Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India
| | - Rohit Shetty
- Department of Corneal and Refractive Surgery, Narayana Nethralaya (H.M., A.A.J., J.M., N.C., P.B., R.S.), Bangalore, India; University Eye Clinic Maastricht, Maastricht University Medical Center (MUMC+) (M.F., R.S., R.M.M.A.N.), Maastricht, Netherlands
| | - Rudy M M A Nuijts
- University Eye Clinic Maastricht, Maastricht University Medical Center (MUMC+) (M.F., R.S., R.M.M.A.N.), Maastricht, Netherlands
| | - Abhijit Sinha Roy
- From the Imaging, Biomechanics and Mathematical Modelling Solutions, Narayana Nethralaya Foundation (M.F., A.S.R.), Bangalore, India.
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Francis M, Shetty R, Padmanabhan P, Vinciguerra R, Vinciguerra P, Lippera M, Matalia H, Khamar P, Chinnappaiah N, Mukundan D, Nuijts RMMA, Sinha Roy A. New simulation software to predict postoperative corneal stiffness before laser vision correction. J Cataract Refract Surg 2023; 49:620-627. [PMID: 36791274 DOI: 10.1097/j.jcrs.0000000000001169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 02/09/2023] [Indexed: 02/17/2023]
Abstract
PURPOSE To develop a new virtual surgery simulation platform to predict postoperative corneal stiffness (Kc mean ) after laser vision correction (LVC) surgery. SETTING Narayana Nethralaya Eye Hospital and Sankara Nethralaya, India; Humanitas Clinical and Research Center, Italy. DESIGN Retrospective observational case series. METHODS 529 eyes from 529 patients from 3 eye centers and 10 post-small-incision lenticule extraction (SMILE) ectasia eyes were included. The software (called AcuSimX) derived the anisotropic, fibril, and extracellular matrix biomechanical properties (using finite element calculation) of the cornea using the preoperative Corvis-ST, Pentacam measurement, and inverse finite element method assuming published healthy collagen fibril orientations. Then, the software-computed postoperative Kc mean was adjusted with an artificial intelligence (AI) model (Orange AI) for measurement uncertainties. A decision tree was developed to classify ectasia from normal eyes using the software-computed and preoperative parameters. RESULTS In the training cohort (n = 371 eyes from 371 patients), the mean absolute error and intraclass correlation coefficient were 6.24 N/m and 0.84 (95% CI, 0.80-0.87), respectively. Similarly, in the test cohort (n = 158 eyes from 158 patients), these were 6.47 N/m and 0.84 (0.78-0.89), respectively. In the 10 ectasia eyes, the measured in vivo (74.01 [70.01-78.01]) and software-computed (74.1 [69.03-79.17]) Kc mean were not statistically different ( P = .96). Although no statistically significant differences in these values were observed between the stable and ectasia groups ( P ≥ .14), the decision tree classification had an area under the receiver operating characteristic curve of 1.0. CONCLUSIONS The new software provided an easy-to-use virtual surgery simulation platform for post-LVC corneal stiffness prediction by clinicians and was assessed in post-SMILE ectasia eyes. Further assessments with ectasia after surgeries are required.
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Affiliation(s)
- Mathew Francis
- From the Imaging, Biomechanics and Mathematical Modelling Solutions, Narayana Nethralaya Foundation, Bangalore, India (Francis, Sinha Roy); Department of Corneal and Refractive surgery, Narayana Nethralaya, Bangalore, India (Shetty, Matalia, Khamar, Chinnappaiah); Medical Research Foundation, Sankara Nethralaya, Chennai, Tamil Nadu, India (Padmanabhan, Mukundan); Humanitas San Pio X Hospital, Milan, Italy (R. Vinciguerra); The School of Engineering, University of Liverpool, Liverpool, United Kingdom (R. Vinciguerra); Humanitas Clinical and Research Center-IRCCS, Milan, Italy (P. Vinciguerra, Lippera); Department of Biomedical Sciences, Humanitas University, Milan, Italy (P. Vinciguerra, Lippera); Department of Ophthalmology, Maastricht University Medical Centre, Maastricht, the Netherlands (Nuijts)
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Phase retardation and corneal sublayer thickness repeatability using ultrahigh-resolution polarization-sensitive OCT. J Cataract Refract Surg 2023; 49:76-83. [PMID: 36026712 DOI: 10.1097/j.jcrs.0000000000001033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 07/25/2022] [Indexed: 12/31/2022]
Abstract
PURPOSE To assess phase retardation and corneal sublayer thickness repeatability using ultrahigh-resolution polarization-sensitive optical coherence tomography (PS-OCT). SETTING Narayana Nethralaya Eye Hospital, Bangalore. DESIGN Observational. METHODS In this study, all eyes were imaged using a custom-built ultrahigh-resolution PS-OCT and high-resolution hybrid OCT (MS-39). The repeatability of phase retardation en face maps and corneal sublayer thickness profiles was evaluated. The reflectivity and phase retardation were calculated from the 2 orthogonal polarization channels to generate en face maps of phase retardation and corneal sublayer thicknesses. 3 consecutive measurements of all participants were acquired for each eye. For each measurement, the participant was asked to sit back and was realigned again. The repeatability was assessed using the intraclass correlation coefficient (ICC). RESULTS The study included 20 healthy eyes of 20 participants. The phase retardation en face maps showed preferential arrangement of collagen fibrils with least retardation in the apex and maximum retardation in the periphery. The phase retardation showed excellent repeatability (ICC >0.95) in all zones. The Bowman layer and stromal layer thicknesses were measured with excellent repeatability (ICC >0.93 and >0.99, respectively). Significant differences ( P < .05) in stromal layer thickness were observed between MS-39 and PS-OCT. The repeatability of epithelial thickness measurements was better with PS-OCT than MS-39. CONCLUSIONS The combinational assessment of corneal birefringence and sublayer thicknesses shows the advanced potential of ultrahigh-resolution PS-OCT in routine clinical practice over current OCT devices.
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Lalgudi VG, Qazi S, Baig K, Shetty R. Commentary: Predictors of outcomes after corneal collagen cross linking: Present, and future directions. Indian J Ophthalmol 2022; 70:2937-2938. [PMID: 35918948 PMCID: PMC9672744 DOI: 10.4103/ijo.ijo_882_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- Vaitheeswaran Ganesan Lalgudi
- Department of Cornea, Precision Cornea Centre, Ottawa; Department of Cornea, External Disease and Refractive Surgery, The Ottawa Hospital (TOH), University of Ottawa Eye Institute, The Ottawa Hospital, Ontario, Canada
| | - Shakeel Qazi
- Department of Cornea, Precision Cornea Centre, Ottawa, Ontario, Canada
| | - Kashif Baig
- Department of Cornea, Precision Cornea Centre, Ottawa, Ontario, Canada
| | - Rohit Shetty
- Department of Cornea and Refractive Surgery, Narayana Nethralaya Eye Hospital, Bangalore, Karnataka, India
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Lalgudi VG, Shetty R, Nischal KK, Ziai S, Koaik M, Sethu S. Biochemical and molecular alterations and potential clinical applications of biomarkers in keratoconus. Saudi J Ophthalmol 2022; 36:7-16. [PMID: 35971485 PMCID: PMC9375466 DOI: 10.4103/sjopt.sjopt_203_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 12/05/2021] [Accepted: 02/19/2022] [Indexed: 11/06/2022] Open
Abstract
Keratoconus (KC) is a complex multifactorial corneal ectatic disorder, with disease onset commonly in the second-third decades significantly affecting quantity, quality of vision, and quality of life. Several pathways and factors such as eye rubbing, inflammatory, oxidative, metabolic, genetic, and hormonal among others have been studied in the last two decades. However, the management of KC is still based on a few "one-size fits all" approaches and is predominantly guided by topo/tomographic parameters. Consideration of the several novel factors which have the potential to be biomarkers in addressing several unanswered questions in the disease process could help in the better predictive ability of progression or vision loss and customization of treatment options. This article delves into the understanding of these novel factors or biomarkers based on the pathogenesis of KC and features a special focus on their potential clinical applications and their future role in personalized medicine.
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Affiliation(s)
- Vaitheeswaran G. Lalgudi
- Department of Cornea, External Disease and Refractive Surgery, University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, Canada,Address for correspondence: Dr. Vaitheeswaran G. Lalgudi, Department of Cornea, External Disease and Refractive Surgery, University of Ottawa Eye Institute, The Ottawa Hospital, 501, Smyth Road, Ottawa, ON, Canada. E-mail:
| | - Rohit Shetty
- Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bengaluru, Karnataka, India
| | - Kanwal K. Nischal
- UPMC Eye Centre, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA,Department of Pediatric Ophthalmology and Strabismus, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Setareh Ziai
- Department of Cornea, External Disease and Refractive Surgery, University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, Canada,Department of Ophthalmology, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada
| | - Mona Koaik
- Department of Cornea, External Disease and Refractive Surgery, University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, Canada,Department of Ophthalmology, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada
| | - Swaminathan Sethu
- Molecular and Genetic Research, GROW Laboratories, Narayana Nethralaya Foundation, Bengaluru, Karnataka, India
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Mapping of corneal birefringence in thin and asymmetric keratoconus corneas with ultrahigh resolution polarization sensitive OCT. J Cataract Refract Surg 2022; 48:929-936. [PMID: 35082233 DOI: 10.1097/j.jcrs.0000000000000898] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 01/21/2022] [Indexed: 11/26/2022]
Abstract
PURPOSE To evaluate phase retardation (PR) across healthy, thin corneas (< 500 µm), asymmetric and bilateral KC. SETTING Narayana Nethralaya, Bangalore. DESIGN Observational, cross-sectional. METHODS There were four eye groups: healthy (group 1; n=10 eyes), thin corneas with no clinical disease (group 2; n=10 eyes), asymmetric KC (group 3; n=5 eyes) and clinical KC (group 4; n=15 eyes). All eyes were imaged with polarization sensitive OCT (PS-OCT), MS-39 and Corvis-ST. Using PS-OCT, the phase retardation (PR) was analysed in annular regions. The anterior (A-E) and Bowman's (E-B) wavefront aberrations, Epithelium Zernike indices (EZI), total corneal thickness, Corvis biomechanical index (CBI), total biomechanical index (TBI) and Belin-Ambrosio overall deviation index (BAD-D) were analysed. RESULTS Only the CBI, TBI, BAD-D, the A-E and E-B aberrations, EZI and total corneal thickness distributions of groups 1, 2 and 3 were similar (p>0.05) but not CCT (p<0.05). The PR distributions clearly showed that the eyes in groups 1, 2 and 3 had a normal corneal birefringence unlike group 4 eyes (p<0.05). The PR map was similar to the preferred orientations of collagen fibers seen in X-ray diffraction ex vivo studies of corneal stroma. CONCLUSION The PR distributions may eliminate the uncertainty associated with the stromal status of thin and asymmetric KC corneas. The group 2 and 3 eyes appeared as healthy due to normal corneal birefringence at the time of imaging and longitudinal follow-up of these eyes with PS-OCT may assist in early detection of onset of disease.
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Lalgudi VG. Commentary: Corneal biomechanical assessment following refractive surgery: Past, present, and future. Indian J Ophthalmol 2021; 69:2656-2657. [PMID: 34571608 PMCID: PMC8597506 DOI: 10.4103/ijo.ijo_1569_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Vaitheeswaran G Lalgudi
- Department of Cornea and Refractive Surgery, University of Ottawa Eye Institute, Ontario, Canada
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12
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Ringel MJ, Tang EM, Tao YK. Advances in multimodal imaging in ophthalmology. Ther Adv Ophthalmol 2021; 13:25158414211002400. [PMID: 35187398 PMCID: PMC8855415 DOI: 10.1177/25158414211002400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 02/23/2021] [Indexed: 12/12/2022] Open
Abstract
Multimodality ophthalmic imaging systems aim to enhance the contrast, resolution, and functionality of existing technologies to improve disease diagnostics and therapeutic guidance. These systems include advanced acquisition and post-processing methods using optical coherence tomography (OCT), combined scanning laser ophthalmoscopy and OCT systems, adaptive optics, surgical guidance, and photoacoustic technologies. Here, we provide an overview of these ophthalmic imaging systems and their clinical and basic science applications.
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Affiliation(s)
- Morgan J. Ringel
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Eric M. Tang
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Yuankai K. Tao
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37235, USA
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Webb JN, Zhang H, Sinha Roy A, Randleman JB, Scarcelli G. Detecting Mechanical Anisotropy of the Cornea Using Brillouin Microscopy. Transl Vis Sci Technol 2020; 9:26. [PMID: 32832232 PMCID: PMC7414627 DOI: 10.1167/tvst.9.7.26] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/28/2020] [Indexed: 12/12/2022] Open
Abstract
Purpose The purpose of this study was to detect the mechanical anisotropy of the cornea using Brillouin microscopy along different perturbation directions. Methods Brillouin frequency shift of both whole globes (n = 10) and cornea punches (n = 10) were measured at different angles to the incident laser, thereby probing corneal longitudinal modulus of elasticity along different directions. Frequency shift of virgin (n = 26) versus cross-linked corneas (n = 15) over a large range of hydration conditions were compared in order to differentiate the contributions to Brillouin shift due to hydration from those due to stromal tissue. Results We detected mechanical anisotropy of corneas, with an average frequency shift increase of 53 MHz and 96 MHz when the instrument probed from 0° to 15° and 30° along the direction of the stromal fibers. Brillouin microscopy did not lose sensitivity to mechanical anisotropy up to 96% water content. We experimentally measured and theoretically modeled how mechanical changes independent of hydration affect frequency shift as a result of corneal cross-linking by isolating an approximately 100 MHz increase in frequency shift following a cross-linking procedure purely due to changes of stromal tissue mechanics. Conclusions Brillouin microscopy is sensitive to mechanical anisotropy of the stroma even in highly hydrated corneas. The agreement between model and experimental data suggested a quantitative relationship between Brillouin frequency shift, hydration state of the cornea, and stromal tissue stiffness. Translational Relevance The protocol and model validated throughout this study offer a path for comprehensive measurements of corneal mechanics within the clinic; allowing for improved evaluation of the long-term mechanical efficacy of cross-linking procedures.
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Affiliation(s)
- Joshua N Webb
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA
| | - Hongyuan Zhang
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA.,Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | | | | | - Giuliano Scarcelli
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA
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