Corneal surgery in keratoconus: which type, which technique, which outcomes?

Correlation between Corneal Volume and Corneal Biomechanics and Corneal Volume Significance in Staging and Diagnosing Keratoconus

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.

Causal Links Between Systemic Disorders and Keratoconus in European Population

PURPOSE

To establish the presence of a causal linkage between prevalent systemic diseases and keratoconus (KC).

DESIGN

Mendelian randomization (MR) analysis.

METHODS

After an exhaustive screening process, genetic variants linked to various systemic diseases were identified as instrumental variables at the genome-wide significance level. Subsequently, MR analyses were conducted to elucidate their potential causal connection with KC (N = 26,742). The encompassed systemic ailments comprise diabetes, hay fever/allergic rhinitis/eczema, obstructive sleep apnea, thyroid dysfunction, aortic aneurysm, major depressive disorder, inflammatory bowel disease (including Crohn's disease and ulcerative colitis), and mitral valve prolapse. Our study adheres to the principles of Strengthening the Reporting of Observational Studies in Epidemiology Using MR guidelines.

RESULTS

Using inverse variance weighting as the primary MR analysis method, our findings revealed that hay fever/allergic rhinitis/eczema (odds ratio, 10.144; 95% CI, 2.441-42.149; P = .001) and ulcerative colitis (odds ratio, 1.147; 95% CI, 1.054-1.248; P = .002) were associated with an increased risk of KC within the largest population under scrutiny. Conversely, the prolonged hyperglycemic state did not exhibit a potentially protective effect in delaying the pathogenesis of KC, and no correlation was observed between the two (odds ratio, 0.320; 95% CI, 0.029-3.549; P = .353). Also, obstructive sleep apnea, thyroid function, aortic aneurysm, major depressive disorder, Crohn's disease, and mitral valve prolapse did not exhibit a causal association with KC (P > .05 for all comparisons).

CONCLUSIONS

This study indicates an increased risk of KC related to hay fever/allergic rhinitis/eczema and ulcerative colitis, with diabetes not providing a protective effect. These findings may potentially contribute some insights to inform clinical interventions.

Regenerative treatment of ophthalmic diseases with stem cells: Principles, progress, and challenges

Background

Degenerate eye disorders, such as glaucoma, cataracts and age-related macular degeneration (AMD), are prevalent causes of blindness and visual impairment worldwide. Other eye disorders, including limbal stem cell deficiency (LSCD), dry eye diseases (DED), and retinitis pigmentosa (RP), result in symptoms such as ocular discomfort and impaired visual function, significantly impacting quality of life. Traditional therapies are limited, primarily focus on delaying disease progression, while emerging stem cell therapy directly targets ocular tissues, aiming to restore ocular function by reconstructing ocular tissue.

Main text

The utilization of stem cells for the treatment of diverse degenerative ocular diseases is becoming increasingly significant, owing to the regenerative and malleable properties of stem cells and their functional cells. Currently, stem cell therapy for ophthalmopathy involves various cell types, such as embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), and retinal progenitor cells (RPCs). In the current article, we will review the current progress regarding the utilization of stem cells for the regeneration of ocular tissue covering key eye tissues from the cornea to the retina. These therapies aim to address the loss of functional cells, restore damaged ocular tissue and or in a paracrine-mediated manner. We also provide an overview of the ocular disorders that stem cell therapy is targeting, as well as the difficulties and opportunities in this field.

Conclusions

Stem cells can not only promote tissue regeneration but also release exosomes to mitigate inflammation and provide neuroprotection, making stem cell therapy emerge as a promising approach for treating a wide range of eye disorders through multiple mechanisms.

Artificial Neural Network for Automated Keratoconus Detection Using a Combined Placido Disc and Anterior Segment Optical Coherence Tomography Topographer

Purpose

To assess the efficacy of an automated program for keratoconus and keratoconus suspect detection based on corneal measurements provided by a combined Placido disc and anterior segment optical coherence tomography (OCT) topographer.

Methods

In a multicentric cross-sectional study, an artificial neural network (ANN) was created using 6677 eyes from an equal number of patients (classified as 2663 normal eyes, 1616 keratoconus eyes, 210 keratoconus suspect eyes, 1519 myopic postoperative eyes, and 669 abnormal eyes). Each group was randomly divided into a training set (70% of the dataset) and a validation set (the remaining 30%). A multilayer perceptron network with a backpropagation learning algorithm was developed for the study. Indexes used to train the ANN were based on curvature and elevation of both the anterior and posterior corneal surfaces and the new corneal OCT indexes-based on corneal, stromal, and epithelial thicknesses.

Results

For keratoconus detection, our ANN showed an accuracy of 98.6%, precision of 96%, recall of 97.9%, and F1-score of 96.9%. For keratoconus suspect detection, our ANN showed an accuracy of 98.5%, precision of 83.6%, recall of 69.7%, and F1-score of 76%.

Conclusions

Compared to previous literature, the addition of new OCT-based epithelial and stromal thickness indexes improves ANN detection capacity of keratoconus suspect eyes. For already stablished keratoconus our ANN detection capacity is excellent, but equivalent to previous evidence without incorporating such new OCT-based indexes.

Translational Relevance

OCT-based epithelial and stromal thickness indexes improve ANN detection capacity of keratoconus on its early stages.

Corneal biomechanics in early diagnosis of keratoconus using artificial intelligence

Keratoconus is a blinding eye disease that affects activities of daily living; therefore, early diagnosis is crucial. Great efforts have been made toward an early diagnosis of keratoconus. Recent studies have shown that corneal biomechanics is associated with the occurrence and progression of keratoconus. Hence, detecting changes in corneal biomechanics may provide a novel strategy for early diagnosis. However, an early keratoconus diagnosis remains challenging due to the subtle and localized nature of its lesions. Artificial intelligence has been used to help address this problem. Herein, we reviewed the literature regarding three aspects of keratoconus (keratoconus, early keratoconus, and keratoconus grading) based on corneal biomechanical properties using artificial intelligence. Furthermore, we summarized the current research progress, limitations, and possible prospects.

Development of a Web-Based Algorithm for Understanding the Intraocular Lens-Based Surgery in Stable and Progressing Keratoconus for Non-Specialist Ophthalmologists

PURPOSE

To propose an algorithm to facilitate lens-based surgery in keratoconus.

METHODS

A literature review was performed to prepare a software algorithm based on cone location, stability, best spectacle-corrected distance visual acuity (BSCVA) level and whether there is a clear or cataractous lens. The software usability was assessed through a 10-question questionnaire and two hypothetical keratoconus case histories (moderately simple and moderately complex) given to 15 trainees. The usability questionnaires were graded on a Likert scale (1 = strongly disagree to 5 = strongly agree) and two case histories (1 = very difficult to 7 = very easy).

RESULTS

The algorithm can be found at https://www.sussexeyelaserclinic.co.uk/keratoconus/. Thirteen trainees completed the questionnaire. 91.9% would frequently use it; for 100%, it was easy to use independently without technical support; for 63.7%, it was strongly integrated; for 100%, it was consistent; 100% thought that most people would learn to use it quickly, 91.9% found the system not cumbersome to use, felt very confident to use it and need not learn a lot to use it. The first case was found easy by 63.7% and the second by 45%.

CONCLUSION

We present an algorithm as a guide for lens-based surgery in stable and progressing keratoconus, which is classified based on cone location. This algorithm will help trainee and "non-specialist" ophthalmic surgeons understand the pre-operative planning for the surgery and referral to the "specialist" corneal surgeon, considering factors such as progression, BSCVA, keratometry, topography and apex location of the cone in keratoconus patients.

A Comparison of Black and Non-Black Patients in the Presentation and Treatment of Keratoconus

Purpose

Patients with advanced keratoconus (KCN) are less likely to benefit from corneal cross-linking and may require a partial or full thickness keratoplasty. This study aimed to determine whether racial disparities exist in the clinical presentation and initial treatment recommendations for patients evaluated for KCN.

Methods

A single-center retrospective review was conducted on all patients who presented to the cornea department for initial evaluation of KCN between 2018 and 2020. Patients who had undergone prior corneal procedures or surgeries were excluded. Baseline sociodemographic and clinical information was collected and stratified according to black versus non-black race. Generalized estimating equations were used to examine the association between black race and presenting corrected distance visual acuity (CDVA), presence of corneal scarring, keratometry values, Belin ABCD score, and treatment recommendations. Multivariate models were adjusted for patient demographics.

Results

A total of 128 patients (251 eyes) were included in this study. In fully adjusted models, black individuals presented with significantly worse CDVA (p < 0.0001) and worse tomographic KCN staging according to the Belin ABCD criteria (p = 0.002) compared to non-blacks. Blacks were also more than four times as likely to present with a thinnest pachymetry <400 µm (p < 0.0001) and more than three times as likely to have corneal scarring (p = 0.001). Blacks were more than seven times more likely to have keratoplasty recommended as treatment than conservative management such as corneal cross-linking or contact lenses (p = 0.004).

Conclusion

Compared with their non-black counterparts, blacks presented with significantly more advanced KCN, which placed them at risk of requiring more invasive treatment plans. Future studies should investigate reasons for such late presentations and aim to mitigate disparities in the presentation and management of KCN.

Comparison of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty in Keratoconic Eyes With Previous Hydrops-Related Corneal Scar

PURPOSE

This study aimed to compare the outcomes of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) procedures in keratoconic eyes with a previous hydrops-related corneal scar.

METHODS

In this retrospective study, the medical records of patients who had hydrops-related corneal scarring and underwent keratoplasty surgery were reviewed. Patients treated with DALK were classified as group 1, and patients treated with PK as group 2. Preoperative and postoperative best-corrected visual acuity, central corneal thickness, keratometry (K), and refractive error values of each group were recorded and compared.

RESULTS

Seventy-eight eyes (41 in group 1 and 37 in group 2) were included in this study. The mean follow-up period of the patients was 37.7 ± 30.0 months in group 1 and 51.2 ± 29.4 months in group 2 ( P = 0.06). The preoperative and postoperative best-corrected visual acuity and central corneal thickness values were statistically similar in both groups (each P value >0.05). Keratometry values (K1 and mean keratometry) were significantly steeper in group 1 ( P1 = 0.02 and P2 = 0.03, respectively). Descemet membrane perforation was experienced in 7 (4 macroperforation and 3 microperforation; 15.6%) of 45 eyes that planned to perform DALK. These 4 eyes with macroperforation underwent PK and were excluded from the study. When all postoperative complications were assessed, although the total complication rate was 21% after DALK, it was 43% after PK ( P = 0.04).

CONCLUSIONS

DALK with a big-bubble technique is a feasible surgery in eyes with corneal scarring due to previous hydrops and is comparable with PK in terms of visual and refractive outcomes. This study suggests that DALK, which is safer than PK with less postoperative complication rates, should be the primary surgical option to avoid serious complications in keratoconic eyes with hydrops-related corneal scarring.

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Unravelling the Impact of Cyclic Mechanical Stretch in Keratoconus-A Transcriptomic Profiling Study

Biomechanical and molecular stresses may contribute to the pathogenesis of keratoconus (KC). We aimed to profile the transcriptomic changes in healthy primary human corneal (HCF) and KC-derived cells (HKC) combined with TGFβ1 treatment and cyclic mechanical stretch (CMS), mimicking the pathophysiological condition in KC. HCFs (n = 4) and HKCs (n = 4) were cultured in flexible-bottom collagen-coated 6-well plates treated with 0, 5, and 10 ng/mL of TGFβ1 with or without 15% CMS (1 cycle/s, 24 h) using a computer-controlled Flexcell FX-6000T Tension system. We used stranded total RNA-Seq to profile expression changes in 48 HCF/HKC samples (100 bp PE, 70-90 million reads per sample), followed by bioinformatics analysis using an established pipeline with Partek Flow software. A multi-factor ANOVA model, including KC, TGFβ1 treatment, and CMS, was used to identify differentially expressed genes (DEGs, |fold change| ≥ 1.5, FDR ≤ 0.1, CPM ≥ 10 in ≥1 sample) in HKCs (n = 24) vs. HCFs (n = 24) and those responsive to TGFβ1 and/or CMS. PANTHER classification system and the DAVID bioinformatics resources were used to identify significantly enriched pathways (FDR ≤ 0.05). Using multi-factorial ANOVA analyses, 479 DEGs were identified in HKCs vs. HCFs including TGFβ1 treatment and CMS as cofactors. Among these DEGs, 199 KC-altered genes were responsive to TGFβ1, thirteen were responsive to CMS, and six were responsive to TGFβ1 and CMS. Pathway analyses using PANTHER and DAVID indicated the enrichment of genes involved in numerous KC-relevant functions, including but not limited to degradation of extracellular matrix, inflammatory response, apoptotic processes, WNT signaling, collagen fibril organization, and cytoskeletal structure organization. TGFβ1-responsive KC DEGs were also enriched in these. CMS-responsive KC-altered genes such as OBSCN, CLU, HDAC5, AK4, ITGA10, and F2RL1 were identified. Some KC-altered genes, such as CLU and F2RL1, were identified to be responsive to both TGFβ1 and CMS. For the first time, our multi-factorial RNA-Seq study has identified many KC-relevant genes and pathways in HKCs with TGFβ1 treatment under CMS, suggesting a potential role of TGFβ1 and biomechanical stretch in KC development.

Corneal Stromal Densitometry Evolution in a Clinical Model of Cellular Therapy for Advanced Keratoconus

PURPOSE

The aim of this study was to report the corneal densitometry (CD) evolution studied by Scheimpflug tomography, anterior segment optical coherence tomography (AS-OCT), and confocal microscopy changes, in patients with advanced keratoconus included in a clinical experience of advanced cell therapy using autologous humans adipose-derived adult stem cells (ADASCs) and corneal decellularized and ADASCs-recellularized human donor corneal laminas.

METHODS

This study is an interventional prospective, consecutive, randomized, comparative series of cases. Fourteen patients with keratoconus were randomly distributed into 3 groups for 3 types of surgical interventions: group 1 (G-1), autologous ADASC implantation (n = 5); group 2 (G-2), decellularized human corneal stroma (n = 5); and group 3 (G-3), autologous ADASCs + decellularized human corneal stroma (n = 4). Participants were assessed with Scheimpflug-based Oculus Pentacam CD module, AS-OCT (Visante; Carl Zeiss), and confocal microscopy (HRT3 RCM Heidelberg).

RESULTS

A significant improvement of 1 to 2 logMAR lines in all visual parameters in the 3 groups was obtained. The central and total CD were statistically significantly higher in G-2 compared with G-1 and G-3 compared with G-1 at the studied annular zones centered on the corneal apex (0-2, 2-6, and 6-10 mm). There was statistical significance higher in G-3 compared with G-2 at the central corneal stroma at 0-2 and 2-6 mm. The confocal microscopy findings and the AS-OCT reflected the densitometry changes.

CONCLUSIONS

The intrastromal implantation of ADASCs produced very subtle changes in CD at the level of the central corneal stroma. However, the intrastromal implantation of decellularized corneal laminas increases it slightly, but with lower values than the implantation of recellularized laminas with ADASCs.

Comparison of visual outcomes, keratometric parameters and biomechanical profiles between deep anterior lamellar keratoplasty with big-bubble technique vs. Melles technique for keratoconus: a retrospective study

OBJECTIVE

Comparing results of two different DALK surgery techniques (big bubble vs. Melles) in patients with advanced keratoconus.

DESIGN

a retrospective comparative clinical study.

PARTICIPANTS

This study conducted on 72 eyes of 72 participants.

INTRODUCTION

This study designed to compare the results of two different DALK surgery techniques (big bubble vs. Melles) in patients with advanced keratoconus.

METHOD

Thirty-seven eyes were treated using the big bubble DALK method, while 35 eyes were treated using the Melles approach. Uncorrected visual acuity (UCVA), best corrected spectacle visual acuity (BCSVA), manifest refraction, keratometric characteristics, contrast sensitivity, corneal aberrations, corneal biomechanical characteristics, and endothelial cell profile are the outcome measurements.

RESULTS

Mean UCVA in big bubble group was 0.61 ± 25 LogMAR and in Melles group was 0.89 ± 0.41 LogMAR (p-value 0.043). Mean BCSVA in big bubble group (0.18 ± 0.12 Log MAR) was significantly better than Melles group (0.35 ± 0.16 Log MAR). Mean of sphere and cylinder refraction showed no significant difference between two groups. Comparing the endothelial cell profile, corneal aberrations, corneal biomechanical properties and keratometry had no significantdifferences. Contrast sensitivity reported as modulation transfer function (MTF) showed higher values in big bubble group and differences with Melles group weresignificant. Results of point spread function (PSF) in big bubble group had superiority to Melles group with considerable statistical P value of 0.023.

CONCLUSION

When opposed to the Melles approach, the big bubble technique generates a smooth interface with less stromal residue, which results in higher visual quality and contrast sensitivity.

Long-Term Outcomes of Excimer Laser-Assisted Penetrating Keratoplasty Using a Commercially Available Laser System - A Retrospective Case Series

BACKGROUND

Favorable functional outcomes have been reported after excimer laser-assisted penetrating keratoplasty (EXL PKP). But this technique has not been widely adopted, and there are reports on EXL PKP from only a very limited number of institutions. Some of these results refer to operations carried out with laser systems that are not commercially available. In this retrospective case series, we report the long-term outcome of EXL PKP using the Schwind Amaris 500E laser system.

MATERIAL AND METHODS

This retrospective consecutive case series included 30 eyes of 29 patients who had undergone EXL PKP between 2010 and 2013. Primary outcome measures were topographic astigmatism and visual acuity. Secondary outcome measures were the rates of graft rejection and graft failure, and the rate of grafts with an endothelial cell density below 500 cells/mm². Survival analyses were carried out for the following endpoints: visual acuity, rate of graft rejection, and rate of grafts with endothelial cell densities higher than 500 cells/mm².

RESULTS

The median interquartile range (IQR) duration of follow-up was 45 (36) months. The indications for PKP were keratoconus (n = 21), corneal scarring (n = 6), Fuchs endothelial dystrophy (n = 1), and corneal dystrophy other than Fuchs endothelial dystrophy (n = 2). The median (IQR) topographic astigmatism at the end of the follow-up period was 5.3 (2.9) D. Forty-five months after surgery, 73% of all eyes had a visual acuity better than 0.3 LogMAR. The rate of graft rejection after 45 months of follow-up was 32%. All eyes maintained endothelial cell densities higher than 500 cells/mm². There was no graft failure.

CONCLUSIONS

EXL PKP is a safe and effective surgical procedure. No general conclusions can be drawn on the refractive outcome of EXL PKP. Potential advantages, such as a higher degree of graft-host congruity, that could possibly improve the refractive outcome should be weighed against the higher costs of EXL PKP.

Current approaches in the management of patients with keratoconus

Keratoconus is a relatively frequent eye disease, especially in young patients, in which the cornea gradually thins and deforms in a cone shape. In the past, it could be treated only with glasses, rigid contact lenses or, for advanced cases, penetrating corneal transplant. Nowadays, corneal cross-linking, intracorneal ring segments implantation or deep anterior lamellar keratoplasty are available options of treatment, along with the above mentioned ones. Several studies focused on this disease and its management attempted to establish the applicability of these treatment methods in current practice. In the early stages, glasses or soft toric contact lenses are able to correct the astigmatism, but, as the disease progresses, rigid contact lenses are indicated. Corneal cross-linking is done in order to slow down or even stop the progression of the disease. Implanting intracorneal ring segments helps improve visual acuity in patients with low vision that cannot be corrected otherwise. Advanced stages need corneal transplant, either penetrating or anterior lamellar, depending on each patient's ocular characteristics. Thus, keratoconus treatment is individualized for every patient, according to the stage of the disease. Moreover, because of the new developed technology, keratoconus patients can benefit from efficient treatment, in much safer conditions.

Comparing the natural progression and clinical features of keratoconus between pediatric and adult patients

To present the natural course of keratoconus (KC) and compare pediatric and adult patients. Design A retrospective cohort study. Setting Hospital-based. Patient Population In total, 152 patients (288 eyes) diagnosed with KC at Chang Gung Memorial Hospital, Taiwan, were included. Previously managed patients and those with missing optical data were excluded. Observation Procedures Patients were divided into pediatric (≤ 18 years) and adult (> 18 years) groups. Demographics, clinical data, and optical variables were collected, including corrected distance visual acuity (CDVA), refractive error, and keratometric readings (K). Main Outcome Measure Optical variables at the final follow-up before aggressive treatment. Results In total, 20 pediatric (37 eyes) and 132 adults (251 eyes) patients were eligible for this study. The mean follow-up time was 2.98 years. Male predominance was observed in both groups. Both groups had similar clinical characteristics and optical variables at the initial diagnosis. Pediatric patients progressed significantly more rapidly in refractive errors, including spheres and cylinders, spherical equivalence, steep K, and flat K during the follow-up. However, significant change between the two study groups was only seen in sphere refractive error spherical equivalence. Conclusion Pediatric patients had more rapidly progressive KC than adult patients, so early detection and frequent follow-up for prompt interventions are necessary for these patients.

Long-Term Clinical Outcomes of Small-Incision Femtosecond Laser-Assisted Intracorneal Concave Lenticule Implantation in Patients with Keratoconus

Purpose

The purpose of this study was to evaluate the long-term prognosis of small-incision femtosecond laser-assisted intracorneal concave lenticule implantation (SFII) in correction of human keratoconus.

Methods

This was a prospective study for 11 patients who received SFII after being diagnosed as progressive keratoconus based on the Amsler–Krumeich classification system. Clinical assessment was performed for all the patients prior to and postsurgically at different time points for 5 years. These included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), biomechanically corrected intraocular pressure (bIOP), corneal topography, anterior segment optical coherence tomography (AS-OCT), confocal microscopy, and biomechanical assessment with Corvis ST.

Results

Comparison of preoperative and 60-month postoperative UDVA and CDVA (P_60months=0.081 and 0.001, respectively), all eyes showed an improvement in CDVA. Corneal topography showed no significant changes in corneal anterior K1, K2, posterior K1, K2, posterior elevation, or corneal densitometry compared with preoperative levels (P > 0.05). Corvis ST showed that central corneal thickness (CCT) and stiffness at applanation 1 (SP-A1) were significantly greater 1 week postsurgically when compared to the baseline (P < 0.05) and remained stable thereafter. The lenticule under the AS-OCT remained transparent throughout the entire postsurgical period. Under confocal microscopy, corneal edema and an increase in cell activation and reflectivity were observed at the lenticule-stromal interface within 1 week postoperatively. These reactions gradually subsided with time within 6 months.

Conclusion

SFII is an effective procedure to prevent the progression of keratoconus due to its minimal invasiveness and capability of maintaining a steady biometry of the cornea.

Optometric practices and attitudes in keratoconus patient management in Latin America

CLINICAL RELEVANCE

To explore optometric practices and attitudes in the management of keratoconus patients in LatinAmerica and how they are influenced by eye-care technology will help to minimise disease progression and their impact on patients' quality of life in Latin America.

BACKGROUND

Keratoconus is a progressive, bilateral and asymmetric corneal disorder that requires a multidisciplinary approach, the use of different eye assessment technology, and different management approaches; mainly contact lenses and surgery.

METHODS

Self-reported answers to an online survey (adapted to primary eye care) distributed via a newsletter emailed by various professional organisations across 15 Latin American countries were assessed and compared with those previously reported in three European countries.

RESULTS

Answers from 977 eye care practitioners (60%) with >10 years of experience (396 in Latin America and 581 in Europe) were assessed. A total of 65.9% of Latin American responders prescribed rigid corneal lenses (RCL), although more than half of the respondents (54.0%) would fit more RCL if they underwent further training in RCL fitting. A majority of Latin American practitioners (74.0%) considered that RCL fitting is more difficult in keratoconus, requiring more diagnostic lenses (4.6 ± 2.7; median 4; range 1-10) than are necessary for healthy eyes. Low availability of corneal topography was reported in Latin America (23%), although practitioners with topographers are more likely to prescribe RCL (92.3%) and detect more new patients with keratoconus per year (83.5%). A minority of respondents referred keratoconus patients to another optometrist (25.8%) or (40.4%) participated in comanagement with ophthalmologists.

CONCLUSION

This study provides initial evidence regarding keratoconus management in Latin America and suggests that actions are necessary to improve RCL training, facilitate eye-care technology accessibility and encourage comanagement between eye care practitioners to minimise disease progression and their impact on patients' quality of life in Latin America.

Evaluation of the effectiveness of combined staged surgical treatment in patients with keratoconus

Purpose

This study performs comparative assessment of the results of different types of two-stage surgical treatment in patients with keratoconus, including combination of corneal collagen cross-linking with intrastromal corneal ring segments followed by topography-guided photorefractive keratectomy.

Materials and methods

Prospective review of 101 patients (101 eyes) with keratoconus was performed. Patients underwent corneal collagen cross-linking (32 patients), intrastromal corneal ring segments (48 patients), and a combination of these two procedures (21 patients). Transepithelial topography-guided photorefractive keratectomy was performed as the second stage of treatment in all patients with obtained stable refractive results at 8 months after first stage. Main outcome measures were visual acuity (uncorrected distance and corrected distance) and corneal topographic indices.

Results

Comparison of the studied parameters after first stage surgical treatment between non-combined CXL and combined groups demonstrated a statistically significant difference for uncorrected distance visual acuity, corrected distance visual acuity, and cylindrical refraction values (p<0.05). We observed significant improvement of visual acuity and key corneal topographic indices after topography-guided photorefractive keratectomy in all study groups (p<0.05). In 50 (49.5%) patients customized excimer laser ablation gave the possibility of full spherical and cylindrical corrections. Ten eyes (10%) had delayed epithelial healing, no corneal stromal opacities developed.

Conclusions

This study shows that combined two-stage surgical treatment of keratoconus, consisting of intrastromal corneal ring segment implantation with corneal collagen cross-linking followed by topography-guided photorefractive keratectomy, is clinically more effective to prevent keratectasia progression and increase visual acuity than the use of non-combined two-stage techniques.

Keratoconus: An updated review

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.

Evaluation of changes in corneal volume, volume and angle of anterior chamber in keratoconus patients using Pentacam after CXL

Introduction and Objective:

Corneal collagen cross-linking (CXL) with riboflavin and ultraviolet-A (UVA) is a new technique of mechanical stability of the cornea and prevention of keratoconus progression. The present study aimed at the evaluation of the changes in the corneal volume (CV), volume, and the angle of anterior chamber in keratoconus patients using the Pentacam after CXL.

Methods:

This prospective study was performed on 48 eyes of 24 patients (including 12 men, 17–33 years old) with progressive keratoconus undergoing CXL treatment at collagen cross-linking Imam Khomeini Hospital in Ahvaz in 2019. The CV (CV) and anterior chamber parameters such as anterior chamber volume (ACV) and anterior chamber angle (ACA) were measured using the Pentacam before CXL and at 6 and 12 months after CXL. Also, all of the patients were evaluated in terms of best-corrected visual acuity (BCVA), during the follow-up.

Results:

The pre-CXL values of BCVA was significantly lower than the post-CXL values in 6 and 12 months (0.18 ± 0.11, 0.15 ± 0.10, and 0.11 ± 0.10, respectively, P < 0.0001). In general, there was a significant improvement in the BCVA (P < 0.0001), a significant decrease in the CV (P = 0.001), and a significant increase in the ACV (P < 0.0001), and angle (P < 0.0001) 6 and 12 months after CXL.

Conclusion:

It seems that CXL has a positive effect on the anterior chamber parameters (ACV and ACA) and CV after 6 months and 1 year in the treatment of keratoconus patients. In addition, the visual acuity improves after CXL. Finally, further studies with a higher sample size and longer follow-up periods are recommended.

Referral pattern and co-management of keratoconus patients in primary eye care: A survey of three European countries

PURPOSE

To explore current primary care practices in keratoconus management in Portugal and compare with previous reported results in two European countries (the UK and Spain), with a special focus on interdisciplinary collaboration and referral practice patterns.

METHODS

An online survey adapted to European professional practice was distributed (via newsletters) by the Portuguese Optometrist Association to explore keratoconus patient management and referral practice patterns among Portuguese practitioners.

RESULTS

Responses of 119 optometrists were compared with previous reported of 464 eye-care practitioners (126 in the UK and 338 in Spain). Most respondents (79% in Portugal, 71% in the UK and 76% in Spain; p = 0.31) had < 5 new keratoconus patients each year. No accepted referral criterion was found (p < 0.01) because small number of the respondents (14%) in Portugal referred out at initial diagnosis (50% in the UK and Spain); 32% referred out when progression was detected (17% in the UK and 30% in Spain); and a minority (10% in Portugal, 9% in the UK, and 6% in Spain) referred out when visual acuity was affected. A majority of respondents (83%) in Portugal reported no co-management with ophthalmologists (60% in the UK and 73% in Spain; p < 0.01).

CONCLUSION

The results of this study suggest that it is necessary to encourage interdisciplinary collaboration between practitioners to improve referral of patients with suspected keratoconus to an ophthalmology specialist to change the course of this disease, to reduce keratoconus progression and visual acuity impairment and to minimize the impact of this disease on patients' quality of life.

Customized eye modeling for optical quality assessment in myopic femto-LASIK surgery

Refractive surgery is recognized as an effective method for myopia treatment, but it can induce night vision disturbances such as glare. We present an eye modeling method for the optical quality assessment in response to the structural changes in the eyes by femto-LASIK surgery. Customized eye models were built from the measurements of 134 right eyes pre- and post-operatively. Optical performance was evaluated using spot diagrams, point spread functions (PSFs), modulation transfer functions (MTFs), and chromatic aberrations at various fields (0°-30°), different pupil diameters (2-6 mm), and initial myopias (- 1.25 to - 10.5 D). Pupil size and initial myopia are the two major factors that affect visual performance of post-operative eyes. The results of spot diagrams, PSFs, and MTFs indicated that post-operative visual performance deteriorated as the visual field and pupil size increased, and it was significantly influenced by initial myopia. Post-operative chromatic aberrations were also affected by initial myopia. As pupil size increased, the post-operative longitudinal chromatic aberrations tended to decrease slightly, while the transverse chromatic aberrations remained similar. The use of eye modeling for refractive surgery assessment could possibly provide a more personalized surgical approach, could improve the prediction accuracy of refractive surgery outcomes, and promote the invention and development of better surgical methods.

Endothelial cell loss rate after penetrating keratoplasty: optical versus therapeutic grafts

Background

This study aimed to compare the rate of endothelial cell loss (ECL) after penetrating keratoplasty (PKP) for optical versus therapeutic grafts at 3-, 6-, and 12-month postoperatively. Furthermore, the study aimed to investigate postoperative graft viability and the rate of graft rejection during the first year of follow-up for both indications.

Methods

This was a prospective, observational, comparative study that included patients who sought medical advice at the cornea outpatient clinic of Ain Shams University Hospitals, Cairo, Egypt. The study recruited 60 patients: group 1 included 30 transplanted corneas of 30 patients who underwent optical PKP for various indications, while group 2 included 30 transplanted corneas of 30 patients who underwent therapeutic PKP for unhealed, resistant infectious keratitis. Specular microscopy was performed for all patients at the 3-, 6-, and 12-month follow-up visits using Nidek CEM-530 specular microscopy. Postoperative clinical examinations were performed at the same follow-up visits to detect graft rejection.

Results

There were no statistically significant differences between the groups concerning the postoperative timing of graft clarity or the rate of ECL at 3- and 6-months postoperatively; however, the rate of ECL was significantly greater in group 2 than in group 1 at 12-months postoperatively (P = 0.03), although the difference was small from a clinical point of view. Moreover, there was no statistically significant difference between the groups in terms of the graft rejection rate.

Conclusions

Therapeutic PKP results were comparable to optical PKP with respect to graft viability, the rate of ECL, and the rate of graft rejection 1 year after grafting.

Customized Stromal Lenticule Implantation for Keratoconus

PURPOSE

To investigate the potential benefit of keratoconus surgery using customized corneal stromal donor lenticules obtained from myopic small incision lenticule extraction (SMILE) surgery by femtosecond laser.

METHODS

In this prospective, consecutive, non-comparative series of cases, 22 lenticules were obtained from 22 myopic patients who had SMILE with a lenticule central thickness of greater than 110 µm. The lenticules were implanted in 22 eyes with advanced keratoconus. The lenticules were customized for the purpose of the implantation with either a simple necklace or necklace-with-ring shape (compound form) depending on the corneal thickness and corneal topography configuration of the implanted keratoconic eyes. The lenticules were implanted into a 9.5-mm corneal lamellar pocket created by the femtosecond laser. Changes in densitometry, thickness, confocal microscopy, corrected distance visual acuity (CDVA), and endothelial cell density were investigated.

RESULTS

Intrastromal lenticule implantation was successfully performed in all cases without any complication. Corneal thickness showed a mean enhancement of 100.4 µm at the thinnest point. On biomicroscopy, all corneas were clear at 1 year postoperatively and there was a significant improvement in corneal densitometry during the entire follow-up period. Confocal biomicroscopy showed collagen reactivation without any inflammatory features caused by the implanted fresh lenticules. CDVA improved from 0.70 to 0.49 logMAR (P = .001) and keratometry decreased from 54.68 ± 2.77 to 51.95 ± 2.21 diopters (P = .006).

CONCLUSIONS

Customized SMILE lenticule implantation by femtosecond laser proved to be feasible, resulting in an improvement in vision, topography, and refraction in the implanted eyes. [J Refract Surg. 2020;36(12):786-794.].

Clinical Outcomes of a New Type of Continuous Intrastromal Corneal Ring for Treatment of Keratoconus

PURPOSE

The purpose of this study was to evaluate the efficacy and safety of implantation of a new continuous corneal ring in keratoconic corneas of an Iranian population.

METHODS

This study was conducted on 95 contact lens-intolerant keratoconic eyes with clear central corneas. A continuous corneal ring, annular intrastromal corneal inlay (AICI), was inserted using femtosecond laser in all cases. Patients were followed up for 1, 3, and 12 months postsurgery. Visual and subjective refractive outcomes were evaluated in each examination. Besides, keratometry and aberrometric values were recorded before and 12 months after surgery. Finally, vector analysis of refractive astigmatism was performed using the Alpins method.

RESULTS

The uncorrected and corrected distance visual acuities improved significantly 12 months after surgery from 0.91 ± 0.39 to 0.38 ± 0.22 (P < 0 0.001) and 0.33 ± 0.21 to 0.13 ± 0.11 logMAR (P < 0.001), respectively. Moreover, spherical and cylindrical refractive components reduced from -2.52 ± 2.62 to -0.76 ± 1.78 D (P < 0.001) and -4.14 ± 1.64 to -1.91 ± 1.18 D (P < 0.001), respectively. The mean anterior keratometry had a significant reduction 12 months after AICI insertion (P< 0.001). Primary coma and spherical aberration values showed a significant increase (both, P < 0.05). Our results showed 100% safety (safety index: 1.8) and 45% efficacy (efficacy index: 1).

CONCLUSIONS

AICI implantation seemed to be a safe and effective procedure for improving visual acuity and refractive outcomes in subjects with keratoconus.

In Vivo Confocal Microscopy of Stromal Lenticule Addition Keratoplasty for Advanced Keratoconus

PURPOSE

To investigate the in vivo corneal microscopic changes after femtosecond laser-assisted stromal lenticule addition keratoplasty in keratoconus by means of in vivo confocal microscopy.

METHODS

Patients affected by advanced keratoconus were included in the study. Negative meniscus-shaped stromal lenticules, produced with a femtosecond laser (VisuMax; Carl Zeiss Meditec) from eye bank corneas were transplanted into a stromal pocket dissected in the recipient cornea at a depth of 120 µm. In vivo confocal microscopy was performed during the 12-month follow-up to investigate changes of the corneal and lenticule structure.

RESULTS

Ten patients were enrolled in the study. No changes of the dendritic cell population were documented during the follow-up period. Mild edema and stromal keratocyte activation gradually decreased during the first month. Subbasal nerve density returned to preoperative values after 6 months. Donor-recipient interfaces appeared hyperreflective but gradually improved over time with significantly reduced reflectivity after 3 months. No evidence of stromal inflammatory cell migration or matrix opacification was observed. Endothelial and keratocyte density remained stable over time. A variable degree of stromal radially distributed folds, not visible on biomicroscopy, was observed in the lenticule and in the posterior recipient stroma.

CONCLUSIONS

Stromal lenticule addition keratoplasty produces transitory nerve plexus density reduction and minor inflammatory reaction that rapidly decreases during the first month. Donor-recipient interface reflectivity is comparable to a femtosecond laser refractive procedure with no sign of stromal opacification or stromal rejection in 1 year of follow-up. [J Refract Surg. 2020;36(8):544-550.].

Corneal Stromal Regeneration Therapy for Advanced Keratoconus: Long-term Outcomes at 3 Years

PURPOSE

To report the 3-year clinical outcomes of corneal stromal cell therapy consisting of the intrastromal implantation with autologous adipose-derived adult stem cells (ADASCs), and decellularized or ADASC-recellularized human donor corneal laminas in advanced keratoconus.

METHODS

Fourteen patients were enrolled in 3 experimental groups. Group 1 (G-1) patients underwent implantation of ADASCs alone (3 × 10⁶ cells/1 mL) (n = 5). Group 2 (G-2) patients received a 120-μm decellularized corneal stroma lamina (n = 5). Group 3 (G-3) patients received a 120-μm lamina recellularized with ADASCs (1 × 10⁶ cells/1 mL) (n = 4). ADASCs were obtained by elective liposuction. Implantation was performed into a femtosecond pocket under topical anesthesia.

RESULTS

At 3 years, a significant improvement of 1 to 2 logMAR lines in uncorrected distance visual acuity was observed in all groups. A statistically significant decrease in corrected distance visual acuity was obtained in G-2 and G-3 (P < 0.001) when compared with that of G-1. Rigid contact lens distance visual acuity showed a statistically significant worsening in G-2 (P < 0.001) compared with that of G-1. A statistically significant increase in central corneal thickness was observed in G-2 (P = 0.012) and G-3 (P < 0.001); in the Scheimpflug corneal topography, the thinnest point was observed in G-2 (P = 0.007) and G-3 (P = 0.001) when compared with that of G-1.

CONCLUSIONS

Intrastromal implantation of ADASCs and decellularized or ADASC-recellularized human corneal stroma laminas did not have complications at 3 years. The technique showed a moderate improvement in (uncorrected distance visual acuity) and (corrected distance visual acuity) in advanced keratoconus.

Femtosecond laser-assisted implantation of corneal stroma lenticule for keratoconus

Purpose

To review recent progress, challenges, and future perspectives of stromal keratophakia for the treatment of advanced keratoconus.

Methods

We systematically reviewed the literature in the PubMed database, last update June 30, 2020. No language restriction was applied. The authors checked the reference lists of the retrieved articles to identify any additional study of interest.

Results

Several techniques have been proposed for the treatment of keratoconus in order to avoid or delay keratoplasty. This was primarily due to the lack of accessibility to donor corneas in many countries. The ease and predictability of the more advanced femtosecond lasers used to correct ametropias by stromal lenticule extraction lead to hypothesize that generated refractive lenticules could be implanted into corneal stromal layers to restore volume and alter the refractive properties of the cornea in patients with corneal ectasias. At the same time, new techniques for preservation, customization, and cellular therapy of the corneal stromal have been developed, directing to the valorization of otherwise discarded byproducts such as donor corneas unsuitable for either lamellar of penetrating keratoplasty.

Conclusions

Femtosecond laser-assisted stromal keratophakia could be a suitable therapeutic option for the treatment of corneal ectasias, especially in patients with advanced keratoconus, providing biomechanical support recovering the pachimetry to nearly normal value at the same time. The accuracy and predictability of the refractive outcome are yet a critical issue and the patient eligible for the procedure still has to be characterized.

Corneal Stromal Regeneration: A Review of Human Clinical Studies in Keratoconus Treatment

The use of advanced therapies with stem cells to reconstruct the complex tissue of corneal stroma has gained interest in recent years. Besides, collagen-based scaffolds bioengineering has been offered as another alternative over the last decade. The outcomes of the first clinical experience with stem cells therapy on corneal stroma regeneration in patients with advanced keratoconus were recently reported. Patients were distributed into three experimental groups: Group 1 (G-1) patients underwent implantation of autologous adipose-derived adult stem cells (ADASCs) alone, Group 2 (G-2) received a 120 μm decellularized donor corneal stromal laminas, and Group 3 (G-3) received a 120 μm recellularized donor laminas with ADASCs. A follow up of 36 months of clinical data, and 12 months of confocal microscopy study was performed, the authors found significant clinical improvement in almost all studied mean values of primary and secondary outcomes. Corneal confocal microscopy demonstrated an increase in cell density in the host stroma, as well as in the implanted tissue. Using different approaches, allogenic small incision lenticule extraction (SMILE) implantation was applied in cases with advanced keratoconus. Some authors reported the implantation of SMILE intrastromal lenticules combined with accelerated collagen cross-linking. Others performed intrastromal implantation of negative meniscus-shaped corneal stroma lenticules. Others have compared the outcomes of penetrating keratoplasty (PKP) vs. small-incision Intralase femtosecond (IFS) intracorneal concave lenticule implantation (SFII). Femtosecond laser-assisted small incision sutureless intrasotromal lamellar keratoplasty (SILK) has been also investigated. The published evidence shows that the implantation of autologous ADASCs, decellularized or recellularized human corneal stroma, allogenic SMILE lenticules corneal inlay, and recombinant cross-linked collagen have shown initially to be potentially effective for the treatment of advanced keratoconus. In light of the present evidence available, it can be said that the era of corneal stromal regeneration therapy has been already started.

Femtosecond laser-assisted stromal keratophakia for keratoconus: A systemic review and meta-analysis

PURPOSE

Femtosecond lasers have revived the possibility of stromal keratophakia or tissue additive keratoplasty, a technique originally introduced by Prof. Jose Ignacio Barraquer in the 1960s. The surgical technique offers a unique solution to treat keratoconus. In the current study, we reviewed and performed a meta-analysis of the clinical outcomes of the femtosecond laser-assisted stromal keratophakia in the treatment of keratoconus.

METHODS

This is a systematic review and meta-analysis of the estimated outcome difference between pre- and post-lenticule implantations.

RESULTS

A total of related 10 studies were found in the literature. No studies reported adverse events, such as persistent haze or graft rejection, at last patients' visits. We further narrowed down the article selection in accordance to our inclusion criteria to report the composite outcomes (9 studies) and meta-analysis (4 studies). In the composite analysis, we demonstrated that lenticule implantation in keratoconus and post-LASIK ectasia patients appeared to expand the stromal volume of the thin corneas, flattened the cones, and significantly improved uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and spherical equivalent (SE). The meta-analysis showed that the random estimated UCVA, BCVA, SE and mean keratometry (K_m) differences following the lenticule implantation was -0.214 (95% CI: -0.367 to 0.060; p = 0.006), -0.169 (-0.246 to 0.091; p < 0.001), -2.294 D (-3.750 to -0.839 D; p = 0.002), and 2.909 D (0.805 to 5.012 D; p = 0.007), respectively.

CONCLUSIONS

Femtosecond laser-assisted stromal keratophakia is a feasible technique to correct the refractive aberrations, expand corneal volume and regularize corneal curvature in patients with keratoconus. However, there is a need to standardize the technique (e.g., whether to crosslink or not or to use convex or concave lenticules) and to formulate a mathematical model that accounts for the long-term epithelial thickness changes and stromal remodeling to determine the shape or profile of the lenticules, in order to improve the efficacy of the keratophakia further.

Epithelial and stromal remodelling following femtosecond laser-assisted stromal lenticule addition keratoplasty (SLAK) for keratoconus

The purpose of this study was to evaluate corneal epithelium and stromal remodelling with anterior segment optical coherence tomography in patients who have undergone stromal lenticule addition keratoplasty (SLAK) for advanced keratoconus. This was a prospective non-comparative observational study. Fifteen eyes of 15 patients with advanced keratoconus underwent implantation with a cadaveric, donor negative meniscus-shaped intrastromal lenticule, produced with a femtosecond laser, into a stromal pocket dissected in the recipient cornea at a depth of 120 μm. Simulated keratometry, central corneal thickness (CTT), corneal thinnest point (CTP), central epithelial thickness (CET), central and peripheral lenticule thickness, anterior and posterior stromal thickness were measured. Regional central corneal epithelial thickness (CET) and variations in the inner annular area (IAT) and outer annular area (OAT) were also analysed. All parameters were measured preoperatively and 1, 3, and 6 months postoperatively. The average anterior Sim-k decreased from 59.63 ± 7.58 preoperatively to 57.19 ± 6.33 D 6 months postoperatively. CCT, CTP, CET, and OAT increased and IAT decreased significantly after 1 month. All parameters appeared unchanged at 6-months except that of OAT that further increased. Lenticule thickness was stable. In conclusion we observed that SLAK reshapes the cornea by central flattening with stromal thickening and epithelial thickness restoration.

Corneal cross-linking versus conventional management for keratoconus: a lifetime economic model

AIMS

To assess the cost-effectiveness of corneal collagen cross-linking (CXL) versus no CXL for keratoconus in the United States (US).

METHODS

A discrete-event microsimulation was developed to assess the cost-effectiveness of corneal cross-linking (CXL, Photrexa + KXL combination product) versus no CXL for patients with keratoconus. The lifetime model was conducted from a US payor perspective. The source for CXL efficacy and safety data was a 12-month randomized, open-label, sham-controlled, multi-center, pivotal trial comparing CXL versus no CXL. Other inputs were sourced from the literature. The primary outcome was the incremental cost per quality-adjusted life year gained. Costs (2019 USD) and effects were discounted 3% annually. The impacts of underlying uncertainty were evaluated by scenario, univariate, and probabilistic analyses.

RESULTS

Starting at a mean baseline age of 31 years and considering a mixed population consisting of 80% slow-progressors and 20% fast-progressors, the CXL group was 25.9% less likely to undergo penetrating keratoplasty (PK) and spent 27.9 fewer years in advanced disease stages. CXL was dominant with lower total direct medical costs (-$8,677; $30,994 versus $39,671) and more QALYs (1.88; 21.80 versus 19.93) compared to no CXL. Considering the impact of reduced productivity loss in an exploratory scenario, CXL was associated with a lifetime cost-savings of $43,759 per patient. CXL was cost-effective within 2 years and cost-saving within 4.5 years.

LIMITATIONS

Limitations include those that are common to similar pharmacoeconomic models that rely on disparate sources for inputs and extrapolation on short-term outcomes to a long-term analytical horizon.

CONCLUSIONS

Keratoconus is a progressive and life-altering disease with substantial clinical, economic, and humanistic consequences. The economic value of cross-linking is maximized when applied earlier in the disease process and/or younger age, and extends to improved work productivity, out-of-pocket costs, and quality of life.

Surgeon Preference for Keratoplasty Techniques and Barriers to Performing Deep Anterior Lamellar Keratoplasty

PURPOSE

To identify barriers and facilitators to adopting deep anterior lamellar keratoplasty (DALK) for nonendothelial corneal pathology.

METHODS

An anonymous survey consisting of 22 multiple choice and free text questions was designed to gather information on demographic factors of surgeons and DALK surgical practices. The survey was emailed to members of the kera-net, a global online corneal surgeon/surgery platform.

RESULTS

A total of 100 surgeons completed the survey, most of whom practice in the United States (73%). Most surgeons (89%) reported performing DALK. Surgeons who did not learn DALK during fellowship (34%) tended to be in practice for higher numbers of years (P < 0.001). Surgeons in private practice are more likely to perform DALK versus those in other settings (92.7% vs. 80.8%, P = 0.087). Surgeons performing more corneal surgeries (at least 100 per year) are more likely to perform DALK than those who perform fewer than 100 per year (52% vs. 14%, P = 0.01). Surgeons who perform Descemet membrane endothelial keratoplasty are more likely to perform DALK than those who do not (81.7% vs. 18.3%, P = 0.014). There was also a positive correlation between PK and DALK surgical volumes (Spearman rank correlation coefficient = 0.57, P < 0.001). The main reasons for surgeon preference for DALK over PK were a desire to preserve the endothelium, intraoperative safety, and decreased complications. Longer surgical time and low patient volume were cited as barriers to adoption of DALK.

CONCLUSIONS

Alterations in DALK technique that reduce surgical time and providing more learning opportunities for DALK might improve adoption.

Long-term refractive outcomes in patients with cataracts and keratoconus after phacoemulsification with toric intraocular lens implant

PURPOSE

To determine the refractive stability of patients with keratoconus and cataracts after the implantation of a toric intraocular lens.

METHODS

This is a cross-sectional, retrospectivestudy. Clinical records from patients with non-progressive keratoconus and cataracts that underwent non-complicated phacoemulsification with toric IOL implantation were reviewed. Mean keratometry (Km), refractive cylinder (RC), spherical equivalent (SE), steeper keratometry (K), and axis were evaluated at the 1-month, 6-month, 12-month, and 24-month follow-up visits.

RESULTS

Fifty-four eyes from 41 patients were included. Thirty-seven (68.5%) female and 17 (31.5%) male patients, with a mean age of 67.52 ± 8.22. Refractive cylinder at postoperative 30 days was -1.61 ± 1.23, 6-month -1.22 ± 0.80, 12-month -1.10 ± 0.83 and 24-month visit after surgery was -1.37 ± 0.77(p = 0.290). SE at the 30-day visit was -0.82 ± 1.90, 6-month -0.64 ± 1.23, 12-month -0.78 ± 1.91 and at 24-month postoperative visit -1.02 ± 1.87 (p = 0.210). Km value at the 1-month visit was 47.23 ± 1.95, 6-month 47.87 ± 1.61, 12-month 46.39 ± 2.52 and 24-month postoperative visit 46.92 ± 1.26 (p = 0.877). The steeper K axis in the 30-day control was 78.53 ± 30.12, 6-month 77.29± 37.68, 1-year 93.13 ± 62.42, 24-month 67.31 ± 38.49 (p = 0.632).

CONCLUSIONS

Our findings suggest a low variation in the refractive outcome for patients with mild and moderate keratoconus and cataracts, without evident progression signals, a demonstrated keratoconus clinical stability. No statistically significant postoperative changes in the refractive cylinder, SE, mean K, and steeper K axis were observed, which suggests good predictability for toric IOL implant.

Corneal Stroma Cell Density Evolution in Keratoconus Corneas Following the Implantation of Adipose Mesenchymal Stem Cells and Corneal Laminas: An In Vivo Confocal Microscopy Study

Purpose

To report the corneal stroma cell density evolution identified by in vivo corneal confocal microscopy in humans using injected autologous adipose-derived adult stem cells (ADASCs) and corneal decellularized laminas in corneas with advanced keratoconus.

Methods

Interventional prospective, consecutive, randomized, comparative series of cases. A total of 14 keratoconic patients were randomly distributed into three groups for three types of surgical interventions: group 1 (G-1), autologous ADASC implantation (n = 5); group 2 (G-2), decellularized human corneal stroma (n = 5); and group 3 (G-3), autologous ADASCs + decellularized human corneal stroma (n = 4).

Results

A gradual and significant increase (P < 0.001) was observed in the cellularity in the anterior and posterior stroma of patients in G-1, G-2, and G-3 a year after the surgery in comparison with the preoperative density level. The same result was observed at the mid-corneal stroma in G-1 and at the anterior and posterior surfaces and within the laminas in G-2 and G-3. The cell density of patients receiving ADASC recellularized laminas (G-3) was statistically significantly higher (P = 0.011) at the anterior surface and within the lamina (P = 0.029) and at the posterior surface than in those implanted only with decellularized laminas (G-2).

Conclusions

A significant increase in cell density occurred up to 1 postoperative year at the corneal stroma following the implantation of ADASCs alone, as well as in those cases implanted with decellularized and recellularized laminas at the different levels of the analysis. However, this increase was significantly higher in the ADASC recellularized laminas.

Surgery for glaucoma in modern corneal graft procedures

Glaucoma is a common cause of vision loss after corneal transplantion and is considered a major risk factor for graft failure. Glaucoma may be present before corneal transplant surgery, or increased intraocular pressure may develop after keratoplasty in up to one-third of patients. Pre-existing glaucoma should be controlled before keratoplasty, either medically or surgically. For postkeratoplasty increase in intraocular pressure; identifying the risk factors allows appropiate follow-up and management. Patients undergoing anterior lamellar keratoplasty may take advantage of reduced rates of postkeratoplasty glaucoma. Glaucoma also complicates eyes with endothelial keratoplasties, mostly related to management of intraocular pressure spikes derived from anterior chamber air bubbles. Nevertheless, the severity is less, and the intraocular pressure is more easily controlled when compared with penetrating keratoplasty. Adequate management of glaucoma that develops before or after keratoplasty may save eyes from irreversible damage to the optic nerve and increase graft survival.

Combined corneal cross-linking and 320° intrastromal corneal ring segments in progressive keratoconus: one-year results

BACKGROUND

Intrastromal corneal ring segments (ICRS) attain regularization of corneal surface in keratoconus (KC), while collagen cross-linking (CXL) halts or slows its progression. The long-arc 320° rings combined with CXL may have a dual-benefit synergistic effect of surface regularity and progression halt.

METHODS

This was a prospective case series study including eyes with progressive KC. Femto-assisted 320° ICRS implantation and epi-off CXL 8 weeks later were carried out in all cases. Uncorrected (UCVA) and corrected distance visual acuity (CDVA) were assessed using Snellen's chart, while corneal tomography was evaluated using Scheimpflug imaging. Follow-up was carried out 3, 6, and 12 months after the CXL.

RESULTS

Thirty-two eyes of 32 patients with progressive KC were included, 18 males and 14 females, and the mean age was 23.1 years. According to the Amsler-Krumeich classification, four eyes had stage 1 KC, 20 had stage 2 KC, and eight had stage 3 KC, and UCVA and CDVA improved from 0.1 ± 0.15 and 0.2 ± 0.19 to 0.4 ± 0.2 (P>  0.01) and 0.5 ± 0.2 (P>  0.01) respectively at 12 months. Manifest refraction spherical equivalent was reduced from - 5.6 ± 2.3 to - 1.1 ± 1.3 D at 12 months after the procedure (P>  0.01). In addition, maximum keratometry was significantly reduced from 54.8 to 49.3 diopters (P>  0.01), while the asphericity index (Q value) has changed from - 1.4 to - 0.25 (P>  0.01) after 12 months. No significant differences were detected between central (n = 12) and eccentric (n = 20) KC in all outcomes.

CONCLUSION

The 320° ICRS-CXL protocol has improved the visual and the tomographic outcomes at 1 year in our patients with progressive KC. No differences were detected between central and eccentric cases. Further larger studies could ensure the safety profile of the combined protocol.

Alió del Barrio J, Cavas F, Alió JL. Changes in the 3D Corneal Structure and Morphogeometric Properties in Keratoconus after Corneal Collagen Crosslinking

Keratoconus is an ectatic disorder that is presently considered one of the most prevalent reasons for keratoplasty. Corneal collagen crosslinking (CXL) is the only proven treatment option available that is capable of halting the progression of the disease by stabilizing the cone in 90% of cases, and by also reducing refractive error and maximal keratometry. This study assesses, by means of a 3D morphogeometric analysis procedure developed by our research team, the corneal structure changes that occur immediately after CXL treatment and during a 6 month follow-up period. A total of 19 eyes from 19 patients diagnosed with keratoconus who underwent CXL were included, and several variables derived from the morphogeometric analysis were calculated and evaluated for the pre-operative, 3 month postoperative, and 6 month postoperative states. Significant reductions were detected in central corneal thickness and corneal spherical-like root mean square (RMS) 3 months after surgery, with non-significant regression of the effect afterward. Significant reductions in the total corneal area/volume were found, with some levels of regression after 6 months in certain volumetric parameters. In conclusion, the eyes with higher values for morphogeometric parameters—posterior apex deviation (PAD), anterior minimum thickness point deviation (AMTPD), and posterior minimum thickness point deviation (PMTPD)—seemed more likely to undergo aberrometric improvement as a result of CXL surgery.

Deep anterior lamellar keratoplasty outcomes in macular and granular corneal dystrophy - A comparative cross-sectional study

Purpose

To compare the functional and anatomical outcomes (in terms of graft uptake and rejection/failure) of deep anterior lamellar keratoplasty (DALK) in stromal corneal dystrophy (macular and granular).

Methods

Sixteen eyes with macular corneal dystrophy (MCD; group A) and 10 eyes with granular corneal dystrophy (GCD; group B) underwent successful DALK by big bubble technique or layer-by-layer dissection.

Results

Both groups showed significant improvement in their best-corrected visual acuity postoperatively (postoperative P value in MCD and GCD was 0.00001 and 0.0008, respectively) with no statistically significant differences between the two groups (P = 0.77) at 1 year. Postoperative endothelial count did not drop significantly in group A (MCD, P= 0.1553). Only in seven eyes preoperative endothelial count could be obtained (due to dense stromal corneal opacity), but there was a significant endothelial count difference between preoperative and postoperative count in group B (GCD, P= 0.0405) at the end of 1 year postoperatively which could be because of age and stage of disease (advanced granular dystrophy) and also because of small sample size of GCD compared with MCD. Intergroup comparison between the two groups showed no statistically significant difference (P = 0.6353) with good postoperative outcome in both groups.

Conclusion

DALK can be successfully done in both groups and results are comparable. However, long-term outcomes on a large scale need to be further evaluated.

Evaluation of a Tangential Map-Based Nomogram for Intrastromal Corneal Ring Segments' Implantation in Keratoconus: One Year Results

Purpose

To evaluate a new tangential map-based nomogram versus the axial map-based nomogram for ICRS in keratoconus.

Methods

A prospective case series study including 64 eyes of 64 patients who underwent ICRS implantation. Cone location was determined for each eye with two maps: the axial and the tangential. Appropriate ring selection was determined using two surgical nomograms: axial map-based and tangential map-based. Visual, refractive, and topographic outcomes were assessed before, as well as at 3, 6, and 12 months after ICRS implantation.

Results

The cone location, and consequently the ring selection, was significantly different in the two nomograms with a “centralization tendency” in the tangential map. In the axial group, UDVA and CDVA improved from 0.12 ± 0.04 and 0.24 ± 0.08 to 0.28 ± 0.08 and 0.4 ± 0.1, respectively. Similarly, MRSE substantially decreased from −6.7 ± 3.3 to −1.2 ± 1.1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1P=0.01^∗. Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months, P=0.01^∗. Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months,

Conclusion

The tangential map-based nomogram attained better visual and refractive outcomes at 1 year. In addition, the cone location was significantly different between both maps with a centralization tendency in the tangential one.

Combined corneal CXL and photorefractive keratectomy for treatment of keratoconus: a review

Keratoconus and iatrogenic keratectasia are the corneal ectatic disorders occurring due to biomechanical weakening of the cornea resulting in distorted images, myopia, and irregular astigmatism. Corneal collagen cross-linking (CXL) is performed to arrest keratoconus successfully. The main aim of this review is to discuss the safety and efficacy of the adjuvant therapies, such as the combination of CXL and photorefractive keratectomy (PRK) for the treatment of corneal ectatic disorders. A comprehensive literature search was performed using PubMed, MEDLINE, and Scopus using keywords 'collagen' 'keratoconus', 'keratectasia', 'collagen cross-linking', and 'photorefractive keratectomy'. Search results were restricted to clinical studies published in English. Corneal CXL effectively arrests the progression of keratoconus by enhancing corneal rigidity. However, functional vision is not improved by cross-linking. Combining CXL to refractive surgeries such as topography-guided PRK or transepithelial PRK is found to be a safe and effective method in providing corneal stability as well as significantly improving functional visual acuity with few minor complications. This combined technique also prevents regression of keratoconus and reduce the risk of keratectasia. CXL combined with PRK is a promising therapeutic approach in ophthalmology that can be successfully used to treat progressive keratoconus and other corneal ectatic disorders and to enhance visual acuity.

Regenerative Surgery of the Corneal Stroma for Advanced Keratoconus: 1-Year Outcomes

PURPOSE

This study evaluated 1-year safety and efficacy outcomes of corneal stroma cell therapy. Therapy consisted of implanting autologous adipose-derived adult stem cells (ADASc) with or without sheets of decellularized donor human corneal stroma within the stroma of patients with advanced keratoconus.

DESIGN

This was a prospective interventional non-randomized series of cases.

METHODS

Fourteen consecutive patients were selected and divided into 3 experimental groups. Group A patients underwent implantation of autologous ADASc alone (3 × 10⁶ cells/1 mL) (n = 5). Group B patients received decellularized donor 120-μm-thick corneal stroma lamina alone (n = 5). Group C patients had implantation of recellularized donor lamina with 1 × 10⁶ autologous ADASc plus another 1 × 10⁶ cells/1 mL at the time of the surgery (n = 4). Autologous ADASc were obtained by elective liposuction. Implantation was performed in the corneal stroma through a femtosecond-assisted 9.5-mm diameter lamellar dissection with the patient under topical anesthesia. Twelve months of follow-up data are presented.

RESULTS

No complications were observed during the 1-year follow-up, and full corneal transparency was recovered within 3 months in all patients. No patient lost lines of visual acuity. Corrected distance visual acuity improved 0.231, 0.264, and 0.094 Snellen lines in groups 1, 2, and 3, respectively. In group 1, refractive parameters showed an overall stability, whereas in groups 2 and 3, sphere improved 2.35 diopter (D) and 0.625 D, respectively. Anterior keratometry remained stable (group 1) and improved in groups 2 and 3 (mean improvement of 2D). Corneal aberrometry improved significantly. In optical coherence tomography scans, corneal thickness showed a mean improvement of 14.5 μm (group 1) and 116.4 μm (groups 2 and 3) in the central thickness, and new collagen production was observed at the surgical plane (group 1). Confocal biomicroscopy confirmed the host recellularization of the implanted laminas.

CONCLUSIONS

Intrastromal implantation of autologous ADASc and decellularized human corneal stroma did not show complications at 1 year of follow-up and were moderately effective for the treatment of advanced keratoconus. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Construction of a full-thickness human corneal substitute from anterior acellular porcine corneal matrix and human corneal cells

AIM

To construct functional human full-thickness corneal replacements.

METHODS

Acellular porcine corneal matrix (APCM) was developed from porcine cornea by decellulariztion. The biomechanical properties of anterior-APCM (AAPCM) and posterior-APCM (PAPCM) were checked using uniaxial tensile testing. Human corneal cells were obtained by cell culture. Suspending ring was designed by deformation of an acupuncture needle. MTT cytotoxicity assay was used to check the cytotoxicity of suspending ring soaking solutions. A new three-dimensional organ culture system was established by combination of suspending ring, 48-well plate and medium together. A human full-thickness corneal substitute was constructed from human corneal cells with AAPCM in an organ coculture system. Biochemical marker expression of the construct was measured by immunofluorescent staining and morphological structures were observed using scanning electron microscopy. Pump function and biophysical properties were examined by penetrating keratoplasty and follow-up clinical observations.

RESULTS

There were no cells in the AAPCM or PAPCM, whereas collagen fibers, Bowman's membrane, and Descemet's membrane were retained. The biomechanical property of AAPCM was better than PAPCM. Human corneal cells grew better on the AAPCM than on the PAPCM. There was no cytotoxicity for the suspending ring soaking solutions. For the constructed full-depth human corneal replacements keratocytes scattered uniformly throughout the AAPCM and expressed vimentin. The epithelial layer was located on the surface of Bowman's membrane and composed of three or four layers of epithelial cells expressing cytokeratin 3. One layer of endothelial cells covered the stromal surface of AAPCM, expressed Na⁺/K⁺ATPase and formed the endothelial layer. The construct was similar to normal human corneas, with many microvilli on the epithelial cell surface, stromal cells with a long shuttle shape, and zonula occludens on the interface of endothelial cells. The construct withstood surgical procedures during penetrating keratoplasty. The corneal transparency increased gradually and was almost completely restored 7d after surgery.

CONCLUSION

AAPCM is an ideal scaffold for constructing full-thickness corneal replacement, and functional human full-thickness corneal replacements are successfully constructed using AAPCM and human corneal cells.

Effect of Air Injection Depth on Big-bubble Formation in Lamellar Keratoplasty: an Ex Vivo Study

This study evaluated the effect of air injection depth in the big-bubble (BB) technique, which is used for corneal tissue preparation in lamellar keratoplasty. The BB technique was performed on ex vivo human corneoscleral buttons using a depth-sensing needle, based on optical coherence tomography (OCT) imaging technology. The needle tip, equipped with a miniaturized OCT depth-sensing probe, was inserted for air injection at a specified depth. Inside the corneal tissue, our needle obtained OCT line profiles, from which residual thickness below the needle tip was measured. Subjects were classified into Groups I, II, III, and IV based on injection depths of 75-80%, 80-85%, 85-90%, and >90% of the full corneal thickness, respectively. Both Type I and II BBs were produced when the mean residual thicknesses of air injection were 109.7 ± 38.0 µm and 52.4 ± 19.2 µm, respectively. Type II BB (4/5) was dominant in group IV. Bubble burst occurred in 1/16 cases of type I BB and 3/16 cases of type II BB, respectively. Injection depth was an important factor in determining the types of BBs produced. Deeper air injection could facilitate formation of Type II BBs, with an increased risk of bubble bursts.

Optical coherence tomography imaging in keratoconus

Optical coherence tomography (OCT) is being increasingly used as a tool in the diagnosis and management of keratoconus. While elevation-based topography remains essential, there is an expanding role for cross-sectional OCT imaging in the diagnosis of the disease. Images and measurements of corneal thickness, and in particular, epithelial thickness, may be important in diagnosing early cases, and following procedures such as intrastromal corneal ring segments, corneal transplants and corneal collagen cross-linking.

Outcome of deep anterior lamellar keratoplasty patients with intraoperative Descemet's membrane perforation: A retrospective cross-sectional study

PURPOSE

To evaluate functional and anatomical outcome in patients undergoing deep anterior lamellar keratoplasty (DALK) with intraoperative Descemet's membrane (DM) perforation (macro and micro).

METHODS

A retrospective cross sectional study (January 2009 to December 2015) of sixteen eyes of sixteen patients which included nine patients of advanced keratoconus (KC), two patients with paracentral DM scarring post hydrops, KC with Bowman's membrane scarring, macular corneal dystrophy and one patient of advanced Pellucid Marginal Degeneration (PMD). All underwent DALK with intraoperative DM perforation. Big bubble technique was attempted in all except in the two patients with post hydrops DM scar. Preoperative and postoperative best corrected visual acuity (BCVA), astigmatism and endothelial count (EC) were compared.

RESULTS

Postoperative BCVA and astigmatism were found to be better and statistically significant ('p value' 0.00 and 0.003 respectively). BCVA preoperative and postoperative was 1.07± 0.3 and 0.28 ± 0.09 in LogMAR respectively and astigmatism pre and postoperative 4.14 ± 1.5 D and 2.7 ± 0.97 D respectively. Percentage decrease in EC at sixth postoperative week was 7.48% and at sixth month and 1 year postoperative was 15.1%. Two patients developed postoperative double anterior chamber and two patients developed pupillary block glaucoma and all were successfully managed.

CONCLUSION

Not all patients of intraoperative DM perforation (including macro perforation) needs to be converted to penetrating keratoplasty. DALK can be successfully done if the perforation is identified early and managed adequately. This is the only known study which has shown a large series of successful DALK even with macro perforations.