Advances in the diagnosis and treatment of keratoconus

Harnessing Corneal Stromal Regeneration for Vision Restoration: A Comprehensive Review of the Emerging Treatment Techniques for Keratoconus

Keratoconus is a progressive corneal disorder characterized by thinning and conical protrusion, leading to visual impairment that often necessitates advanced treatment strategies. Traditional management options, including corrective lenses, corneal cross-linking (CXL), and surgical interventions such as corneal transplants and intracorneal ring segments (ICRS), address symptoms but have limitations, especially in progressive or advanced cases. Recent advancements in corneal stromal regeneration offer promising alternatives for enhancing vision restoration and halting disease progression. This review explores emerging techniques focused on corneal stromal regeneration, emphasizing cell-based therapies, tissue engineering, and gene therapy. Cell-based approaches, including corneal stromal stem cells and adipose-derived stem cells, are promising to promote tissue repair and functional recovery. Tissue engineering techniques, such as developing synthetic and biological scaffolds and 3D bioprinting, are being investigated for their ability to create viable corneal grafts and implants. Additionally, gene therapy and molecular strategies, including gene editing technologies and the application of growth factors, are advancing the potential for targeted treatment and regenerative medicine. Despite these advancements, challenges remain, including technical limitations, safety concerns, and ethical considerations. This review aims to provide a comprehensive overview of these innovative approaches, highlighting their current status, clinical outcomes, and future directions in keratoconus management.

Keratoconus: imaging modalities and management

Background

Keratoconus (KCN) is characterized by gradual thinning and steepening of the cornea, which can lead to significant vision problems owing to high astigmatism, corneal scarring, or even corneal perforation. The detection of KCN in its early stages is crucial for effective treatment. In this review, we describe current advances in the diagnosis and treatment of KCN.

Methods

This narrative review focuses on recent advancements in the diagnosis and treatment of KCN, especially evolving approaches and strategies. To ensure the inclusion of the most recent literature, relevant publications discussing advanced imaging techniques and treatment options for KCN were extensively gathered from the PubMed/MEDLINE and Google Scholar databases. The following index terms and keywords were used for the online search: keratoconus, diagnosis of keratoconus, advances in the diagnosis of keratoconus, topography or tomography, anterior segment optical coherence tomography, treatment of keratoconus, advances in the treatment of keratoconus, collagen crosslinking, intrastromal ring, keratoplasty, and new techniques in keratoconus.

Results

Various screening methods such as corneal topography, tomography, anterior segment optical coherence tomography, and assessment of corneal biomechanics have been developed to identify KCN in its early stages. After diagnosis, KCN management focuses on preventing disease progression. Corneal collagen crosslinking is a minimally invasive treatment that can slow or stop the progression of the condition. Recent research has also explored the use of copper sulfate eye drops (IVMED-80) as a noninvasive treatment to prevent the progression of KCN. Current treatment options for visual improvement include scleral lenses, intracorneal ring segments, corneal allogeneic intrastromal ring segments, and deep anterior lamellar keratoplasty. Recently, novel alternative procedures, such as isolated Bowman layer transplantation, either as a corneal stromal inlay or onlay, have demonstrated encouraging outcomes. Artificial intelligence has gained acceptance for providing best practices for the diagnosis and management of KCN, and the science of its application is contentiously debated; however, it may not have been sufficiently developed.

Conclusions

Early detection and advancements in screening methods using current imaging modalities have improved diagnosis of KCN. Improvement in the accuracy of current screening or diagnostic tests and comparison of their validities are achievable by well-designed, large-scale, prospective studies. The safety and effectiveness of emerging treatments for KCN are currently being investigated. There is an ongoing need for studies to track progress and evaluate clinicians' knowledge and practices in treating patients with KCN. Artificial intelligence capabilities in management approach considering the currently available imaging modalities and treatment options would best benefit the patient.

Artificial intelligence as diagnostic modality for keratoconus: A systematic review and meta-analysis

Objectives

The challenges in diagnosing keratoconus (KC) have led researchers to explore the use of artificial intelligence (AI) as a diagnostic tool. AI has emerged as a new way to improve the efficiency of KC diagnosis. This study analyzed the use of AI as a diagnostic modality for KC.

Methods

This study used a systematic review and meta-analysis following the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched selected databases using a combination of search terms: "((Artificial Intelligence) OR (Diagnostic Modality)) AND (Keratoconus)" from PubMed, Medline, and ScienceDirect within the last 5 years (2018-2023). Following a systematic review protocol, we selected 11 articles and 6 articles were eligible for final analysis. The relevant data were analyzed with Review Manager 5.4 software and the final output was presented in a forest plot.

Results

This research found neural networks as the most used AI model in diagnosing KC. Neural networks and naïve bayes showed the highest accuracy of AI in diagnosing KC with a sensitivity of 1.00, while random forests were >0.90. All studies in each group have proven high sensitivity and specificity over 0.90.

Conclusions

AI potentially makes a better diagnosis of the KC with its high performance, particularly on sensitivity and specificity, which can help clinicians make medical decisions about an individual patient.

Mini review: human clinical studies of stem cell therapy in keratoconus

Treatment of keratoconus is one of the most interesting research fields for researchers in the world. Regenerative medicine based on human stem cells in the treatment of keratoconus has recently received attention. Despite extensive laboratory and animal studies in regenerative medicine of cornea, there are limited clinical studies in keratoconus. These studies showed promising results of stem cell therapy. In initial studies, the transplantation of these cells into stroma was associated with increased vision and improved corneal parameters without side effects. In this article, we tried to review different aspects of keratoconus stem cell therapy, including cell extraction and culture, surgical procedure, effectiveness and safety of this method in human clinical studies.

Analysis of the correlation between biomechanical properties and corneal densitometry in myopic eyes

Background: To investigate the correlation between corneal biomechanical characteristics (in vitro and in vivo) and corneal densitometry in myopia. Methods: The Pentacam (Oculus, Wetzlar, Germany) corneal densitometry (CD) and Corvis ST (Oculus, Wetzlar, Germany) exams were conducted prior to surgery for myopic patients who were intended to undergo small-incision lenticule extraction (SMILE). CD values (grayscale units, GSUs), and in vivo biomechanical parameters were obtained. The stromal lenticule was subjected to a uniaxial tensile test to obtain the elastic modulus E in vitro. We exam the correlations among in vivo, in vitro biomechanical characteristics and CD values. Results: In this study, 37 myopic patients (63 eyes) were included. The mean age of participants was 25.14 ± 6.74 years (range:16-39 years). The mean CD values of the total cornea, anterior layer, intermediate layer, posterior layer, 0-2 mm region and 2-6 mm region were 15.03 ± 1.23 GSU, 20.35 ± 1.98 GSU, 11.76 ± 1.01 GSU, 10.95 ± 0.83 GSU, 15.57 ± 1.12 GSU and 11.94 ± 1.77 GSU, respectively. Elastic modulus E (in vitro biomechanical indicator) was negatively correlated with intermediate layer CD (r = -0.35, p = 0.01) and 2-6 mm region CD (r = -0.39, p = 0.00). A negative correlation was also found between 0-2 mm central region CD and in vivo biomechanical indicator SP-HC (r = -0.29, p = 0.02). Conclusion: In myopic patients, densitometry is negatively correlated with biomechanical properties both in vivo and in vitro. With an increase in CD, the cornea deformed more easily.

Corneal Biomechanics Losses Caused by Refractive Surgery

Recent advances, specifically in the understanding of the biomechanical properties of the cornea and its response to diseases and surgical interventions, have significantly improved the safety and surgical outcomes of corneal refractive surgery, whose popularity and demand continue to grow worldwide. However, iatrogenic keratectasia resulting from the deterioration in corneal biomechanics caused by surgical interventions, although rare, remains a global concern. On one hand, in vivo biomechanical evaluation, enabled by clinical imaging systems such as the ORA and the Corvis ST, has significantly improved the risk profiling of patients for iatrogenic keratectasia. That is despite the fact the biomechanical metrics provided by these systems are considered indicators of the cornea's overall stiffness rather than its intrinsic material properties. On the other hand, new surgical modalities including SMILE were introduced to offer superior biomechanical performance to LASIK, but this superiority could not be proven clinically, creating more myths than answers. The literature also includes sound evidence that tPRK provided the highest preservation of corneal biomechanics when compared to both LASIK and SMILE. The aim of this review is twofold; to discuss the importance of corneal biomechanical evaluation prior to refractive surgery, and to assess the current understanding of cornea's biomechanical deterioration caused by mainstream corneal refractive surgeries. The review has led to an observation that new imaging techniques, parameters and evaluation systems may be needed to reflect the true advantages of specific refractive techniques and when these advantages are significant enough to offer better protection against post-surgery complications.

MicroRNA Profiling in the Aqueous Humor of Keratoconus Eyes

Purpose

To identify differentially expressed (DE) microRNAs (miRNAs) in the aqueous humor (AH) of keratoconus (KC) eyes using next-generation sequencing and to explore whether DE miRNAs might play roles in KC pathophysiology.

Methods

The small RNAs in the AH of 15 KC eyes and 15 myopia eyes (the control group) were sequenced on an Illumina NovaSeq 6000 platform. Gene Oncology and Kyoto Encyclopedia of Genes and Genome enrichment analyses were performed. Receiver operating characteristic curves were used to identify potential KC biomarkers.

Results

We identified 204 miRNAs in the AH of the KC group and 200 in the AH of the control group. Fourteen miRNAs were differentially expressed between the two groups; four miRNAs were upregulated and 10 downregulated in KC AH. The possible pathways regulated by the DE miRNAs included antigen processing and presentation, endocytosis, mismatch repair, and Hippo signaling. The AH concentrations of miR-222-3p, miR-363-3p, and miR-423-5p exhibited areas under the curves of 1.

Conclusions

We profiled the DE miRNAs of the AH of KC eyes. These miRNAs may be associated with KC pathogenesis and could serve as KC biomarkers.

Translational Relevance

Data on aberrantly expressed miRNAs in KC combined with bioinformatics analyses suggest possible roles for specific miRNAs. The DE miRNAs may serve as diagnostic KC biomarkers.

A Review of Corneal Blindness: Causes and Management

Corneal blindness refers to a group of eye disorders that change the corneal transparency, causing corneal scarring and blindness. The leading causes of corneal blindness include infectious causes, i.e., due to bacteria, viruses, fungi, and protozoa. The most common predisposing factors are trauma, contact lens usage, or the use of steroid medications. The various other diseases included are trachoma, dry eye disease, keratoconus, ophthalmia neonatorum, and non-infectious uveitis. Various clinical modalities are used for treating corneal blindness, including organ transplantation. Organ donation is cumbersome as various ethical and other factors are involved. Hence the concept of eye banking was introduced to meet the increasing demand for donors of the cornea. The eye bank's role is harvesting, processing, and keeping a record of the cornea being transplanted and donated. Furthermore, various recent advancements have been made for lamellar keratoplasty surgeries, including bioengineered corneas to fulfil the need for the unavailability of donors for the cornea. Various specific health interventions have been implemented to reduce the prevalence of corneal blindness globally. For proper management of corneal blindness, we have three components that are needed to be taken care of: prevention of corneal blindness, appropriate treatment modalities, and providing adequate rehabilitation services to the patients. This review encompasses the main reasons for corneal blindness and the management and treatment modalities available for the patients. The terms cornea, corneal blindness, treatment, management, causes, and complications were used for the review article on PubMed.

Clinical performance of a custom-designed soft contact lens in patients with keratoconus and intolerance to rigid contact lenses

PURPOSE

This study evaluated the efficacy and safety of YOUSOFT^® soft contact lens (CL) (TOMEY-CL) in patients with keratoconus and intolerance to rigid CLs.

STUDY DESIGN

Retrospective observational study.

METHODS

Thirty-six eyes of 20 patients (14 men and 6 women) with keratoconus and rigid CL intolerance were included in the study. Four patients were unilateral. The mean age was 33.1 ± 11.7 (± standard deviation) years, the mean spherical refractive error was - 4.99 ± 3.97 D, and the mean cylindrical refractive error was - 3.39 ± 2.13 D. The following examinations were performed at baseline and were repeated at every visit; refractometry, visual acuity, corneal topography and pachymetry with an anterior OCT system. Corneal endothelial cell density was evaluated at baseline and every 6 months. Slit-lamp examination was also performed to confirm the CL condition and ocular health at every visit.

RESULTS

Seventeen patients (85%) were able to continue using the Yousoft. Among 3 patients (15%) who dropped out, 2 were dissatisfied with their visual outcomes and one had trouble with lens handling. Uncorrected visual acuity was 1.08 ± 0.43 (range: 0.22 to 2.00) logMAR at baseline, and best CL-corrected visual acuity was 0.01 ± 0.15 (range: - 0.18 to 0.40) logMAR, showing a significant improvement after wearing Yousoft (P < 0.0001). The endothelial cell density did not change significantly, with 2373 ± 482 at baseline and 2402 ± 464 cells/mm² at the latest visit after lens prescription (P = 0.351). There were no severe complications such as corneal infiltrates or infectious keratitis throughout the study period.

CONCLUSIONS

This study showed the efficacy and acceptable safety of Yousoft for patients with keratoconus and intolerance to rigid CLs.

Belin ABCD Progression Display Identifies Keratoconus Progression Earlier Than Conventional Metrics

PURPOSE

To compare the progression rate and time to progression determined using the Belin ABCD Progression Display (BAPD) with conventional metrics in patients with keratoconus (KC).

DESIGN

Retrospective comparison of progression assessment.

METHODS

Patients 18 years and older and 35 years and younger with at least 1 year of follow-up and 3 Pentacam (Oculus, Inc) visits were included in the study. Progression was evaluated by selecting either the first visit or the first 2 visits individually as the baseline on the BAPD, and the red gate was used to determine progression (variability in any A, B, and C parameters ≥95% CI or any 2 parameters ≥80% CI). An increase of ≥1 diopter in corneal astigmatism and curvature parameters and a ≥2% reduction in thickness parameters constituted progressive disease.

RESULTS

Two hundred seventy-seven eyes of 155 patients were included. The 2 baseline visit criteria identified the highest progression (n = 186 [67.2%]), followed by the single baseline visit (n = 158 [57%]), minimum corneal thickness (n = 114 [41.2%]), central corneal thickness (n = 111 [40.1%]), maximum keratometry (n = 76 [27.4%]), corneal astigmatism (n = 55 [19.9%]), back mean keratometry (n = 50 [18.1%]), and front mean keratometry (n = 31 [11.2%]) criteria. The median time to progression was shortest using the single baseline visit criterion (11 months), followed by the 2 baseline visits (11.6 months), minimum corneal thickness (12.1 months), maximum keratometry (12.3 months), corneal astigmatism (14.8 months), central corneal thickness (16.6 months), back mean keratometry (18.4 months), and front mean keratometry (24.4 months) criteria. In a subgroup analysis, progression could be identified 4 to 7 months earlier with the BAPD in eyes that were also progressive for maximum keratometry and central corneal thickness.

CONCLUSIONS

BAPD detects progression at a higher rate and earlier than conventional parameters.