Trends in corneal transplantation at the University Eye Hospital in Tübingen, Germany over the last 12 years: 2004 - 2015

Estimated prevalence of keratoconus in the largest metropolitan area of Italy

PURPOSE

To estimate the prevalence of keratoconus in a population of subjects undergoing first eye examination in an eye clinic in Italy.

METHODS

A single-center, cross-sectional, study was conducted involving patients who underwent first eye examination at an eye clinic in Rome between September 2021 and June 2022. The prevalence of keratoconus was determined by Placido-disk corneal topography using the maximum keratometry (Kmax) value and the Cone Magnitude and Location Index (CLMI) for keratoconus screening. Subjective analysis was performed by two experienced corneal specialists, who classified the outcome into two groups: normal and keratoconus. Risk factors, including family history of keratoconus, allergy or atopy, thyroid disease, eye rubbing habit and gender were also examined.

RESULTS

A total of 512 subjects between 7 and 81 years old were evaluated. The inter-observer agreement to classify subjects in normal or keratoconus group was excellent (k = 1.0); the estimated prevalence in the specific population was 2.1%. Presence of positive family history (9% of keratoconus vs 5% normal), concomitant allergy or atopy (27% vs 9%) and eye rubbing habit (18% vs 4%) were associated with a higher risk of disease.

CONCLUSION

This study reported a high estimated prevalence of keratoconus in a metropolitan area of Italy, as found in recent studies in the Mediterranean and Middle East countries. Screening for keratoconus is highly recommendable and easily feasible with corneal topography under expert supervision and may be indicated primarily in young population to improve early detection and prompt therapeutic management for halting disease progression.

Artificial intelligence for detecting keratoconus

BACKGROUND

Keratoconus remains difficult to diagnose, especially in the early stages. It is a progressive disorder of the cornea that starts at a young age. Diagnosis is based on clinical examination and corneal imaging; though in the early stages, when there are no clinical signs, diagnosis depends on the interpretation of corneal imaging (e.g. topography and tomography) by trained cornea specialists. Using artificial intelligence (AI) to analyse the corneal images and detect cases of keratoconus could help prevent visual acuity loss and even corneal transplantation. However, a missed diagnosis in people seeking refractive surgery could lead to weakening of the cornea and keratoconus-like ectasia. There is a need for a reliable overview of the accuracy of AI for detecting keratoconus and the applicability of this automated method to the clinical setting.

OBJECTIVES

To assess the diagnostic accuracy of artificial intelligence (AI) algorithms for detecting keratoconus in people presenting with refractive errors, especially those whose vision can no longer be fully corrected with glasses, those seeking corneal refractive surgery, and those suspected of having keratoconus. AI could help ophthalmologists, optometrists, and other eye care professionals to make decisions on referral to cornea specialists. Secondary objectives To assess the following potential causes of heterogeneity in diagnostic performance across studies. • Different AI algorithms (e.g. neural networks, decision trees, support vector machines) • Index test methodology (preprocessing techniques, core AI method, and postprocessing techniques) • Sources of input to train algorithms (topography and tomography images from Placido disc system, Scheimpflug system, slit-scanning system, or optical coherence tomography (OCT); number of training and testing cases/images; label/endpoint variable used for training) • Study setting • Study design • Ethnicity, or geographic area as its proxy • Different index test positivity criteria provided by the topography or tomography device • Reference standard, topography or tomography, one or two cornea specialists • Definition of keratoconus • Mean age of participants • Recruitment of participants • Severity of keratoconus (clinically manifest or subclinical) SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register), Ovid MEDLINE, Ovid Embase, OpenGrey, the ISRCTN registry, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP). There were no date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 29 November 2022.

SELECTION CRITERIA

We included cross-sectional and diagnostic case-control studies that investigated AI for the diagnosis of keratoconus using topography, tomography, or both. We included studies that diagnosed manifest keratoconus, subclinical keratoconus, or both. The reference standard was the interpretation of topography or tomography images by at least two cornea specialists.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the study data and assessed the quality of studies using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. When an article contained multiple AI algorithms, we selected the algorithm with the highest Youden's index. We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

We included 63 studies, published between 1994 and 2022, that developed and investigated the accuracy of AI for the diagnosis of keratoconus. There were three different units of analysis in the studies: eyes, participants, and images. Forty-four studies analysed 23,771 eyes, four studies analysed 3843 participants, and 15 studies analysed 38,832 images. Fifty-four articles evaluated the detection of manifest keratoconus, defined as a cornea that showed any clinical sign of keratoconus. The accuracy of AI seems almost perfect, with a summary sensitivity of 98.6% (95% confidence interval (CI) 97.6% to 99.1%) and a summary specificity of 98.3% (95% CI 97.4% to 98.9%). However, accuracy varied across studies and the certainty of the evidence was low. Twenty-eight articles evaluated the detection of subclinical keratoconus, although the definition of subclinical varied. We grouped subclinical keratoconus, forme fruste, and very asymmetrical eyes together. The tests showed good accuracy, with a summary sensitivity of 90.0% (95% CI 84.5% to 93.8%) and a summary specificity of 95.5% (95% CI 91.9% to 97.5%). However, the certainty of the evidence was very low for sensitivity and low for specificity. In both groups, we graded most studies at high risk of bias, with high applicability concerns, in the domain of patient selection, since most were case-control studies. Moreover, we graded the certainty of evidence as low to very low due to selection bias, inconsistency, and imprecision. We could not explain the heterogeneity between the studies. The sensitivity analyses based on study design, AI algorithm, imaging technique (topography versus tomography), and data source (parameters versus images) showed no differences in the results.

AUTHORS' CONCLUSIONS

AI appears to be a promising triage tool in ophthalmologic practice for diagnosing keratoconus. Test accuracy was very high for manifest keratoconus and slightly lower for subclinical keratoconus, indicating a higher chance of missing a diagnosis in people without clinical signs. This could lead to progression of keratoconus or an erroneous indication for refractive surgery, which would worsen the disease. We are unable to draw clear and reliable conclusions due to the high risk of bias, the unexplained heterogeneity of the results, and high applicability concerns, all of which reduced our confidence in the evidence. Greater standardization in future research would increase the quality of studies and improve comparability between studies.

Ocular condition prognosis in Keratoconus patients after corneal ring implantation using artificial neural networks

The common disorder, Keratoconus (KC), is distinguished by cumulative corneal slimming and steepening. The corneal ring implantation has become a successful surgical procedure to correct the KC patient's vision. The determination of suitable patients for the surgery alternative is among the paramount concerns of ophthalmologists. To reduce the burden on them and enhance the treatment, this research aims to previse the ocular condition of KC patients after the corneal ring implantation. It focuses on predicting post-surgical corneal topographic indices and visual characteristics. This study applied an efficacious artificial neural network approach to foretell the aforementioned ocular features of KC subjects 6 and 12 months after implanting KeraRing and MyoRing based on the accumulated data. The datasets are composed of sufficient numbers of corneal topographic maps and visual characteristics recorded from KC patients before and after implanting the rings. The visual characteristics under study are uncorrected visual acuity (UCVA), sphere (SPH), astigmatism (Ast), astigmatism orientation (Axe), and best corrected visual acuity (BCVA). In addition, the statistical data of multiple KC subjects were registered, including three effective indices of corneal topography (i.e., Ast, K-reading, and pachymetry) pre- and post-ring embedding. The outcomes represent the contribution of practical training of the introduced models to the estimation of ocular features of KC subjects following the implantation. The corneal topographic indices and visual characteristics were estimated with mean errors of 7.29% and 8.60%, respectively. Further, the errors of 6.82% and 7.65% were respectively realized for the visual characteristics and corneal topographic indices while assessing the predictions by the leave-one-out cross-validation (LOOCV) procedure. The results confirm the great potential of neural networks to guide ophthalmologists in choosing appropriate surgical candidates and their specific intracorneal rings by predicting post-implantation ocular features.

Trends in Keratoplasty Procedures During 2 Decades in a Major Tertiary Referral Center in Finland: 1995 to 2015

PURPOSE

The purpose of this study was to analyze trends in number, age-adjusted frequency, and type of keratoplasty in a major tertiary referral center, relative to patient and graft characteristics.

METHODS

A retrospective registry study of 1574 patients who in 1995 to 2015 underwent keratoplasty in the Helsinki University Eye Hospital (HUEH). Graft type and sequence, patient characteristics, and date of surgery were recorded. Main outcome measures were annual number, type, and age-adjusted frequency of keratoplasty; patient and graft characteristics; graft procurement; and national population-adjusted frequency of keratoplasty.

RESULTS

In HUEH, from 1995 to 2015, a total of 2191 keratoplasties were performed with 48% of the grafts procured intramurally; 76% were primary and 24% regrafts. The age-adjusted frequency of primary penetrating keratoplasty decreased by 52% from 0.96 to 0.46 per 100,000. The corresponding frequency of primary Descemet stripping automated endothelial keratoplasty increased by 367% from 0.3 to 1.4 after 2006, finally accounting for 68% of primary grafts. Men underwent primary penetrating keratoplasty (median 48 vs. 67 yrs, P = 0.0001) and anterior lamellar keratoplasty (median 37 vs. 46 yrs, P = 0.0015) at a younger age than women. Interval to the first regraft was comparable between sexes (median 2.2 vs. 1.9 yrs, respectively, P = 0.17). The national median population-adjusted frequency of keratoplasties was 3.2 per 100,000 from 2009 to 2015, and HUEH accounted for a median of 69% of them.

CONCLUSIONS

The increased frequency of keratoplasty in HUEH resulted from rapid adoption of Descemet stripping automated endothelial keratoplasty after 2006 and was facilitated by centralizing graft procurement to HUEH and the National Cell and Tissue Center Regea.

Advances in artificial intelligence models and algorithms in the field of optometry

The rapid development of computer science over the past few decades has led to unprecedented progress in the field of artificial intelligence (AI). Its wide application in ophthalmology, especially image processing and data analysis, is particularly extensive and its performance excellent. In recent years, AI has been increasingly applied in optometry with remarkable results. This review is a summary of the application progress of different AI models and algorithms used in optometry (for problems such as myopia, strabismus, amblyopia, keratoconus, and intraocular lens) and includes a discussion of the limitations and challenges associated with its application in this field.

Indications and techniques of corneal transplants performed in one center in Southern Poland, in the years 2001–2020

Purpose

The study aimed to evaluate changes over a period of time in techniques and indications for corneal transplantation in a single center in Poland.

Methods

Retrospective analysis of corneal transplants performed at the Ophthalmology Department of the District Railway Hospital in Katowice in 2001–2020. Data on indications and surgical technique were collected.

Results

A total of 3021 corneal transplantations were performed in the years 2000–2020. The most common technique was penetrating keratoplasty (69,54%), then lamellar grafts—both anterior and posterior (19,63%), and limbal grafts (10,82%). Only in 2007 the number of lamellar keratoplasties exceeded the number of penetrating grafts and accounted for 108 (54,55%), including 85 (42,93%) of Descemet Stripping Automated Endothelial Keratoplasty. The only noticeable trend in changing techniques was a decrease in the number of performed deep anterior lamellar keratoplasties (r 2 = -0.21) over the last seven years. Main indications included bullous keratopathy (23,22%), following keratoconus (18,59%), leukoma (14,67%), keratitis and perforation (14,3%), Fuchs dystrophy (11,4%), and regrafts (7,22%). Leukoma and bullous keratopathy as an indications for corneal transplant have been declining over the years (r2 = 0.60 and r2 = 0.30 respectively). Consecutively, indications such as fuchs dystrophy, regraft and keratitis perforation have increased (r2 = 0.05, r2 = 0.50, r2 = 0.33)

Conclusions

The number of keratoplasties gradually increased from 2001 to 2020. It could be possible that the development and spread of new therapeutic alternatives, like corneal cross-linking and scleral lenses, have contributed to the decrease in deep anterior lamellar keratoplasty performed. There was an increasing trend in the percentage of penetrating keratoplasties for failed grafts, Fuchs dystrophy and infectious keratitis.

Impact of keratoconus stage on outcome after corneal crosslinking

BACKGROUND

This study aimed to analyze if the outcome after corneal crosslinking (CXL) in progressive keratoconus patients depends on the stage at which the procedure is performed. This knowledge would help to improve success of CXL and to define surgery indications in those patients.

METHODS

In this retrospective study, 124 consecutive eyes of 100 patients with progressive keratoconus undergoing corneal CXL at the University Eye Hospital Tübingen were included. The eyes were graded according to modified Krumeich stages depending on induced myopia or astigmatism, corneal radii, minimum corneal thickness, and morphological changes. The observation period covered November 2008 to September 2018. Preoperatively, 12 and 24 months after CXL, the best corrected visual acuity (BCVA) was determined and astigmatism as well as tomographic parameters (Kmax, Kmin, central corneal thickness (CCT), minimum corneal thickness (MCT)) were measured by means of a Scheimpflug camera system.

RESULTS

BCVA results showed significant differences between the modified Krumeich stages at 12 months (p = 0.014) and at 24 months postoperatively (p = 0.032). Also, astigmatism differed significantly among the stages at 24 months after CXL (p = 0.023). However, no significant differences regarding astigmatism were detectable after 12 months. In terms of Kmax, Kmin, CCT, and MCT, no significant differences between the Krumeich stages were observed.

CONCLUSIONS

BCVA showed a significantly higher improvement after CXL in the early stage of keratoconus compared to a higher stage. However, the postinterventional tomographic values did not differ significantly between the different modified Krumeich stages. The significantly higher improvement in BCVA after CXL in the early stage might indicate that earlier intervention provides a higher subjective benefit to the individual. Further studies with larger sample sizes are needed to confirm these findings.

Accuracy of Machine Learning Assisted Detection of Keratoconus: A Systematic Review and Meta-Analysis

(1) Background: The objective of this review was to synthesize available data on the use of machine learning to evaluate its accuracy (as determined by pooled sensitivity and specificity) in detecting keratoconus (KC), and measure reporting completeness of machine learning models in KC based on TRIPOD (the transparent reporting of multivariable prediction models for individual prognosis or diagnosis) statement. (2) Methods: Two independent reviewers searched the electronic databases for all potential articles on machine learning and KC published prior to 2021. The TRIPOD 29-item checklist was used to evaluate the adherence to reporting guidelines of the studies, and the adherence rate to each item was computed. We conducted a meta-analysis to determine the pooled sensitivity and specificity of machine learning models for detecting KC. (3) Results: Thirty-five studies were included in this review. Thirty studies evaluated machine learning models for detecting KC eyes from controls and 14 studies evaluated machine learning models for detecting early KC eyes from controls. The pooled sensitivity for detecting KC was 0.970 (95% CI 0.949–0.982), with a pooled specificity of 0.985 (95% CI 0.971–0.993), whereas the pooled sensitivity of detecting early KC was 0.882 (95% CI 0.822–0.923), with a pooled specificity of 0.947 (95% CI 0.914–0.967). Between 3% and 48% of TRIPOD items were adhered to in studies, and the average (median) adherence rate for a single TRIPOD item was 23% across all studies. (4) Conclusions: Application of machine learning model has the potential to make the diagnosis and monitoring of KC more efficient, resulting in reduced vision loss to the patients. This review provides current information on the machine learning models that have been developed for detecting KC and early KC. Presently, the machine learning models performed poorly in identifying early KC from control eyes and many of these research studies did not follow established reporting standards, thus resulting in the failure of these clinical translation of these machine learning models. We present possible approaches for future studies for improvement in studies related to both KC and early KC models to more efficiently and widely utilize machine learning models for diagnostic process.

Recent indications of endothelial keratoplasty at a tertiary eye care center in South India

PURPOSE

To describe the patient demographics and recent clinical indications of endothelial keratoplasty (EK) in patients presenting to a tertiary eye care center in India.

METHODS

This cross-sectional hospital-based study included 2,182 patients who underwent EK between Jan 2016 and Dec 2019 (4 years period). The data were collected using an electronic medical record system.

RESULTS

Overall, 2,632 eyes of 2,182 patients underwent EK during the study period. Median age was 62 (IQR: 48-70) years and adults (94.45%) comprised most of the cohort. More commonly, the patients were male (55.59%) and from the higher socioeconomic strata (67.51%). The corneal signs included corneal edema (70.93%), corneal scarring (29.60%), corneal vascularization (16%) and guttae (12.88%). The major indications of EK were post-cataract surgery corneal edema in 1331 (50.57%) patients, endothelial dystrophy in 537 (20.4%) patients, failed graft in 535 (20.33%) patients causing a vision impairment of > 20/400-20/1200 in about a half (45.55%) of the patients. Descemet stripping endothelial keratoplasty (DSEK) and Descemet membrane endothelial keratoplasty (DMEK) were performed in 2075 (78.84%) and 557(21.16%) patients, respectively.

CONCLUSION

EK is commonly performed during the sixth decade of life and in males. The most performed procedure is DSEK. The commonest indication was post-cataract surgery corneal edema.

Changing Indications for Penetrating Keratoplasty in Bahrain in a Tertiary Referral Centre

PURPOSE

To study the changing indications for Penetrating keratoplasty in Bahrain and to compare them with published data.

PATIENTS AND METHODS

A Retrospective review of available records of patients who underwent penetrating keratoplasty at a tertiary center in Bahrain (1996-2015). The trend of each indication was analyzed. The study was subdivided into three periods for correlation purposes. Pearson Coefficient r and the p values were used for interpretation of data. The results were compared with similar studies.

RESULTS

A total of 298 patients underwent keratoplasty in the study period, which is from 1996 until 2015 (missing data 2009-2011). Keratoconus was found to be the leading indication, accounting for 33% of the total cases, followed by trachoma 27%, followed by aphakic and pseudophakic bullous keratopathies 13%. Trachoma showed a statistically significant decreasing trend (p < 0.001), Keratoconus had an increasing trend (p<0.001). Bullous keratopathy showed an increasing trend (p = 0.001) with an abrupt rise after 2012.

CONCLUSION

Corneal scarring due to old trachoma was the leading indication for keratoplasty 20 years ago in Bahrain. However, due to improvement of health awareness, hygiene, and the socioeconomic status, this has regressed with keratoconus becoming the leading indication from 2002 onwards. A surge of bullous keratopathy was noted after 2012, placing it as the second commonest indication. This may be due to the introduction of phacoemulsification technique for cataract surgery, and perhaps because the nature of the institute being a teaching hospital. Keratoconus is the leading indication and showed an increasing trend. It is recommended to perform a keratoconus screening program for early detection and prevention.

Successful Regression in Patients with Progressive Keratoconus by Corneal Crosslinking

BACKGROUND

Since 2019, corneal collagen crosslinking (CXL) is included in the catalog of procedures covered by statutory health insurance in Germany. CXL is an established ophthalmological procedure for the last 20 years. The aim of this investigation was the measurement of progression before and after CXL.

MATERIAL UND METHODS

65 consecutive eyes with progressive keratoconus from 53 patients were included in the retrospective study, which were observed at the University Eye Hospital Tübingen at least two years before and at least two years after CXL. The time of observation took place from October 2009 until March 2018. Parameters of interest had been the best corrected visual acuity (BCVA) and the keratometric values from the elevation maps measured by a Scheimpflug camera.

RESULTS

65 eyes of 53 patients had been documented. The study population included 46 (86.8%) male and 7 (13.2%) female subjects. The mean age was 24 ± 8 years. The averaged observation time between the primary consultation and CXL showed 25 ± 15 months. Preoperatively the mean BCVA pointed out in a significant increase (0.13 ± 0.17 [first visit] vs. 0.23 ± 0.22 [preOP], p < 0.0001) while the mean Kmax resulted in a statistically significant increase (46.34 ± 3.33 dpt [first visit] vs. 48.78 ± 4.17 dpt [preOP], p < 0.0001). The mean thinnest point of the cornea showed a significant decrease (490.48 ± 34.23 µm [first visit] vs. 468.62 ± 29.84 µm [preop], p < 0.0001). Postoperatively the mean BCVA resulted in a significant improvement at the 12th postoperative month in comparison to the preoperative measurement (0.23 ± 0.22 [preOP] vs. 0.16 ± 0.14 [12 months], p = 0.04 respectively 0.17 ± 0.17 [24 months], p = 0.0006). The mean Kmax demonstrated in the 12th postoperative month a significant reduction (48.78 ± 4.17 dpt [preOP] vs. 47.91 ± 3.41 dpt [12 months], p = 0.0009 respectively 48 ± 4.56 dpt [24 months], p = 0.0051). The mean thinnest point of the cornea indicated a decrease at the 12th postoperative month (468.62 ± 29.84 µm [preOP] vs. 459.82 ± 35.88 µm [12 months], p = 0.0078 respectively 453.47 ± 43.39 µm [24 months], p = 0.0227).

CONCLUSION

CXL is a successful procedure for the therapy of progressive keratoconus.

Extracellular matrix changes in corneal opacification vary depending on etiology

Purpose

The purpose of this study is to examine the expression of tenascin-C and matrilin-2 in three different disorders, which frequently require corneal transplantation. These pathological conditions include bullous keratopathy (BK), Fuchs' endothelial corneal dystrophy (FECD), and corneal scarring in herpetic keratitis.

Methods

Histological sections of corneal buttons removed during keratoplasty were analyzed in BK (n = 20), FECD (n = 9), herpetic keratitis (n = 12), and cadaveric control (n = 10) groups with light microscopy following chromogenic immunohistochemistry. The sections were evaluated by three investigators, and semiquantitative scoring (0 to 3+) was applied according to standardized methods at 400X magnification. Each layer of the cornea was investigated; moreover, the stroma was subdivided into subepithelial, middle, and pre-Descemet's membrane areas for more detailed analysis.

Results

Excessive epithelial and stromal expression of tenascin-C was identified in all investigated conditions; the results were most pronounced in the pre-Descemet's membrane. Regarding matrilin-2, when examined in BK, there was increased labeling intensity in the epithelium (p<0.001) and stromal layers (p<0.05), and a decrease in the endothelium (p<0.001). In the other investigated conditions, only a low degree of stromal localization (p<0.05) of matrilin-2 was detected.

Conclusions

The expression of tenascin-C and matrilin-2 differs when examined in various corneal pathologies resulting in opacification. Both molecules seem to be involved in regeneration and wound healing of the corneal matrix in these diseases.

Changing trends in penetrating keratoplasty indications at a tertiary eye care center in Budapest, Hungary between 2006 and 2017

AIM

To analyze the changing trends in penetrating keratoplasty (PKP) indications.

METHODS

This retrospective study included all patients with PKP between 2006 and 2017. Patients were classified using histological diagnoses. Our groups were as the following: pseudophakic or aphakic bullous keratopathy, regraft, acute necrotizing and ulcerative keratitis, keratoconus, Fuchs' dystrophy, corneal dystrophy other than Fuchs', corneal scar, other diagnoses and failed endothelial keratoplasty graft. Additionally, two different time-periods (2006-2012 and 2013-2017) were analysed.

RESULTS

Totally 1721 histological analyses of 1214 patients were available for review. The diagnoses were pseudophakic or aphakic bullous keratopathy in 487 (28.3%), regraft in 443 (25.7%), acute necrotizing and ulcerative keratitis in 313 (18.2%), corneal scar in 153 (8.9%), keratoconus in 140 (8.1%). Fuchs' dystrophy in 61 (3.5%), corneal dystrophy other than Fuchs' in 46 (2.7%), other diagnoses in 44 (2.6%) and failed endothelial keratoplasty graft in 34 (2.0%) cases. From the first to the second analysed time-period, incidence of acute necrotizing and ulcerative keratitis, corneal scar, Fuchs' dystrophy increased (P≤0.032 for all) and incidence of keratoconus significantly decreased (P=0.015).

CONCLUSION

Pseudophakic or aphakic bullous keratopathy is the leading indication for PKP, followed by regraft and acute necrotizing and ulcerative keratitis.

A 5-year analysis of endothelial vs penetrating keratoplasty graft survival in Chinese patients

AIM

To determine if there is any difference in long term graft survival between Descemet's stripping endothelial keratoplasty (DSEK) and penetrating keratoplasty (PK).

METHODS

A retrospective 5-year cases analysis of bullous keratopathy secondary to Fuchs' endothelial dystrophy or pseudophakic bullous keratopathy, receiving either DSEK or PK. A total of 42 DSEK cases and 25 PK cases were included in the analysis.

RESULTS

In the 5-year analysis, graft survival rates were very similar in the two groups (DSEK 77.1% vs PK 76.0%, P=0.918, 95%CI: -6.3 to 33.4). Sub-analyses at 1y (DSEK 81% vs PK 95%, P=0.085, 95%CI: -29 to 3.6) and 2y (DSEK 81% vs PK 88%, P=0.381, 95%CI: -25.9 to 11.8) show a trend towards lower survival rates of DSEK vs PK, but the results were not statistically significant.

CONCLUSION

Long term 5-year graft survival is similar between the DSEK and PK methods of corneal transplant in Chinese patients with bullous keratopathy.

Corneae from body donors in anatomy department: valuable use for clinical transplantation and experimental research

Background

Explanted corneae are highly needed for the surgical management of patients with severe corneal diseases. The aim of this study was to determine whether the body donors from the Institute of Anatomy are a suitable source of donor corneae.

Methods

At the Institute of Anatomy at Saarland University Medical Center in Homburg, corneae are prelevated from body donors who had consented to the removal of tissues for transplantation purposes during their lifetime. Following the report of death, the LIONS Eye Bank is informed and the contraindications of corneal explantation are clarified. Obtaining a blood sample within 24 h postmortem is mandatory.

Results

The Institute of Anatomy had 150 body donors in the time period from January 2018 to June 2019. Out of these, 68 (45.3%) were reported to the Eye Bank. The age of the donors (median 82 years (range: 57–96)) is not critical since the quality of the corneae depends on the number of endothelial cells (mean: 2109 ± 67 cells/mm² (range: 511–2944 cells/mm²)). Contraindications were present in 19 (12.6%) cases. The corneae were extracted from 49 (32.7%) body donors. Out of these 98 corneae, 46 (46.9%) were successfully transplanted. Of all non-transplanted corneae, 6 (6.1%) were microbiologically contaminated, 10 (10.2%) had a positive serology, 22 (22.5%) had an endothelial cell count < 2000 cells/mm² and 6 (6.1%) are at time of this analysis still in culture medium. The non-transplanted tissues were used for research.

Conclusions

Explanted corneae from the Institute of Anatomy are a valuable option in obtaining grafts for corneal transplantation, which is why we are working toward on expanding cooperation with this department.

Evaluating the Performance of Various Machine Learning Algorithms to Detect Subclinical Keratoconus

Purpose

Keratoconus (KC) represents one of the leading causes of corneal transplantation worldwide. Detecting subclinical KC would lead to better management to avoid the need for corneal grafts, but the condition is clinically challenging to diagnose. We wished to compare eight commonly used machine learning algorithms using a range of parameter combinations by applying them to our KC dataset and build models to better differentiate subclinical KC from non-KC eyes.

Methods

Oculus Pentacam was used to obtain corneal parameters on 49 subclinical KC and 39 control eyes, along with clinical and demographic parameters. Eight machine learning methods were applied to build models to differentiate subclinical KC from control eyes. Dominant algorithms were trained with all combinations of the considered parameters to select important parameter combinations. The performance of each model was evaluated and compared.

Results

Using a total of eleven parameters, random forest, support vector machine and k-nearest neighbors had better performance in detecting subclinical KC. The highest area under the curve of 0.97 for detecting subclinical KC was achieved using five parameters by the random forest method. The highest sensitivity (0.94) and specificity (0.90) were obtained by the support vector machine and the k-nearest neighbor model, respectively.

Conclusions

This study showed machine learning algorithms can be applied to identify subclinical KC using a minimal parameter set that are routinely collected during clinical eye examination.

Translational Relevance

Machine learning algorithms can be built using routinely collected clinical parameters that will assist in the objective detection of subclinical KC.

A 27-Year Report from the Central Eye Bank of Iran

Purpose

To report the 27-year statistical data from the Central Eye Bank of Iran (CEBI) and its activity.

Methods

All CEBI records regarding procured eyes, tissue utilizations, corneal transplants per capita, and indications for keratoplasty from 1991 to 2017 were analyzed.

Results

In total, 115,743 whole eyes were donated during the 27-year period. Out of the 114,169 eyes donated between 1994 and 2017, 95,314 eyes were distributed for transplantation, and 95,057 corneas were actually transplanted. The mean annual rate of corneal transplants per capita was 55.10 - 6 ± 27.10 - 6 . Although penetrating keratoplasty (PKP, 70%) was the most common technique of corneal transplantation during the study period, it exhibited a decreasing trend between 2006 and 2017 (P = 0.048). It was in contrast to Descemet stripping automated endothelial keratoplasty (DSAEK) that demonstrated an increasing trend during the same period (P < 0.001). Keratoconus (KCN, 39.70%) was the most leading indication for keratoplasty over the last three decades followed by bullous keratopathy (BK, 18.5%), corneal scar and opacities (15.7%), and graft failure (GF, 7.5%), with an increasing trend for BK, GF, and KCN. A majority of scleral tissues (83.7%) were utilized for orbital implant protection.

Conclusion

An increasing trend in the number of procured eyes was observed over the past 27 years in Iran. The most leading indications for corneal transplantation were KCN and BK. While PKP was the most common keratoplasty technique, DSAEK showed an increasing trend over the last 12 years.

[Long-term experiences with corneal crosslinking in patients with progressive keratoconus at the University Eye Hospital in Tübingen, Germany]

BACKGROUND AND PURPOSE

The corneal collagen crosslinking procedure has been clinically performed worldwide for approximately 20 years. The aim of the study was to analyze the long-term outcomes of corneal crosslinking at the University Eye Hospital in Tübingen.

METHODS

In this retrospective study 136 consecutive eyes with progressive keratoconus from 107 patients were included. The observational period was from December 2008 to March 2018. The parameters analyzed were best corrected visual acuity (BCVA) and the keratometry values from elevation maps measured using a Scheimpflug camera.

RESULTS

The study population of 107 patients included 96 (90%) male and 11 (10%) female subjects and the mean age was 23 ± 8 years. The mean observation time between corneal collagen crosslinking and the last follow-up examination was 42 ± 29 months. The mean postoperative BCVA showed a significant improvement from baseline at each point of postoperative measurement. The mean astigmatism and the mean Kmax showed a statistically significant reduction in the first 6 postoperative months. The mean thinnest point of the cornea showed a significant reduction in the first 6 months, after which the cornea thickness stabilized. No serious adverse events relating to the treatment were registered.

CONCLUSION

Long-term outcomes after corneal collagen crosslinking showed a significant reduction of the keratometry values and the BCVA was significantly higher compared to the preoperative value at all times of observation. In conclusion, corneal collagen crosslinking was shown to be an effective and safe treatment for progressive keratoconus.

Fuchs endothelial corneal dystrophy and corneal endothelial diseases: East meets West

Fuchs endothelial corneal dystrophy (FECD) is amongst one of the most common indications for endothelial keratoplasty worldwide. Despite being originally described among Caucasians, it is now known to be prevalent among a large number of populations, including Asians. While the FECD phenotype is classically described as that of central guttate and pigment deposits associated with corneal endothelial dysfunction, there are subtle yet important differences in how FECD and its phenocopies may present in Caucasians vs Asians. Such differences are paralled by genotypic variations and disease management preferences which appear to be geographically and ethnically delineated. This article provides a succinct review of such differences, with a focus on diagnostic and management issues which may be encountered by ophthalmologists practicing in the different geographic regions, when evaluating a patient with FECD.