Subclinical Keratoconus Research Articles

The role of corneal epithelial thickness map in detecting early keratoconus.

To detect subtle changes in early keratoconus by evaluating corneal epithelial thickness differences among patients with binocular very asymmetric ectasia (VAE) and normal subjects. Corneal epithelial thickness was measured using the Fourier-domain AS-OCT system RTVue® 100 (Optovue, Fremont, CA, USA). 152 eyes from 76 patients were divided into three groups: Very asymmetry ectasia-ectasia (VAE-E, n = 38), Very asymmetry ectasia-normal topography (VAE-NT, n = 38), and Normal control (NC, n = 76). Discrimination capacity was assessed using areas under the curve (AUC) of receiver operator characteristic (ROC) curves. In the keratoconus group, the epithelial Min (minimum), central, midperipheral I (inferior), midperipheral IT (inferior-temporal), peripheral IT, and midperipheral T (temporal) were thinner (all P < 0.05). The topography normal group had thinner midperipheral IN (inferior-nasal), peripheral IN, midperipheral T, and peripheral T, and larger Max-Min and Std. Dev (P < 0.05). For diagnosing typical keratoconus, Std. Dev (AUC = 0.982, sensitivity 97.4%, specificity 92.1%) had the highest diagnostic efficiency. Combining four variables (Minimum, Max-Min, Midperipheral IT, and Midperipheral I) performed well in distinguishing topography normal eyes (AUC = 0.896, sensitivity 76.3%, specificity 89.5%). Multivariable analysis using epithelial parameters combined with Pentacam random forest index (PRFI) yielded the best results (AUC = 0.951, sensitivity 90.6%, specificity 89.5%). The corneal epithelial parameters play an important auxiliary role in the diagnosis of keratoconus and the screening of subclinical keratoconus. Combination of epithelial parameters and tomographic parameters can improve the sensitivity of early stage keratoconus detection.

Comparison of the quantitative contrast sensitivity function between early keratoconus and normal eyes

PurposeTo compare the characteristics of the quantitative contrast sensitivity function (qCSF) in eyes with early keratoconus (Early-KC) and normal control (NC) eyes and investigate the associated factors.DesignA cross-sectional study.MethodsThis study included 43 eyes of 43 patients with Early-KC (including subclinical keratoconus [SKC] and forme fruste keratoconus [FFKC]) and 77 NC eyes of 77 participants with corrected distance visual acuity (CDVA) all ≥ 20/20. Contrast sensitivity (CS) was assessed using the qCSF tests. Subgroup analysis was performed according to keratoconus type(SKC and FFKC) and astigmatism(cylindrical refraction >-1.0D or ≤-1.0D).ResultsSex ratio, spherical refraction, and spherical equivalent (SE) varied significantly between the two groups (all P < 0.01). The area under log CSF (AULCSF), CSF Acuity, and CS at low (1.0 and 1.5 cycles per degree [cpd]) and high (12.0 and 18.0 cpd) spatial frequencies decreased significantly in the Early-KC group than that in the NC group (all P < 0.05). The subgroup analysis revealed a similar decrease in the SKC group (all P < 0.05). AULCSF, CSF Acuity, and CS at high spatial frequencies of patients with cylindrical refraction ≤-1.0D in the Early-KC group decreased significantly (all P < 0.05) than those in the NC group. The index of vertical asymmetry and index of height decentration correlated negatively with CS at 1.5 cpd (r= -0.321 and -0.306; both P < 0.05).ConclusionsCS decreased significantly at low and high spatial frequencies in Early-KC, though with normal CDVA. The qCSF test can sensitively reflect visual performance in early keratoconus.

The Role of Pentacam Random Forest Index in Detecting Subclinical Keratoconus in a Chinese Cohort.

Purpose: This study aimed to evaluate the diagnostic accuracy of a novel shape index, the Pentacam Random Forest Index (PRFI), in detecting keratoconus (KC), specifically subclinical keratoconus, in Chinese refractive surgery candidates. Methods: This prospective cohort study included 856 participants who were divided into four groups based on their tomographic outcomes: the KC group (n = 137), the very asymmetric ectasia (VAE) group (n = 73), the normal cornea group (n = 363) and the tomographically suspected KC (TSK) group (n = 283). The diagnostic performance of PRFI and other widely used indices, including the shape index BAD-D and the combined index TBI, was assessed using receiver operating characteristic (ROC) curve analysis and compared using DeLong's test. The area under the curve (AUC), best cutoff values, and Youden index for each parameter are reported. Additionally, the false-positive rates of BAD-D and PRFI were calculated and compared in "normal corneas". Results: All shape and biomechanical parameters collected in this study were found to be significantly different among the four groups (KC, VAE, TSK, and normal groups; p = 0.000). The AUC of PRFI was the highest in detecting any form of KC (including clinical KC eyes and VAE-NT eyes) in Chinese refractive surgery candidates, outperforming the widely used shape index BAD-D (0.919 vs. 0.890, p < 0.001). There was no significant difference in performance between the PRFI and the combined TBI index (0.919 vs. 0.916, p > 0.05). For detecting subclinical KC eyes (i.e., VAE-NT), the AUC of PRFI was 0.774, which was statistically comparable to TBI (0.774 vs. 0.776, p > 0.05), while outperforming BAD-D (0.774 vs. 0.684, p < 0.001). The best cutoff values of PRFI for detecting any KC and VAE-NT eyes were determined to be 0.37 and 0.27, respectively. Additionally, PRFI demonstrated a lower false-positive rate than BAD-D (13.8% vs. 43.8%, p < 0.001). Notably, the relatively high false-positive rate of BAD-D observed in this study might be attributed to the smaller horizontal corneal diameter in tomographically suspected eyes. Conclusions: The PRFI proved to be a superior shape index compared to BAD-D in detecting any form of keratoconus, including subclinical cases, in Chinese refractive surgery candidates. This finding may be attributed to the relatively small corneas commonly observed in Asians.

Relationship between Choroidal Thickness and Anterior Scleral Thickness in Patients with Keratoconus.

To evaluate the relationship between choroidal thickness (CT) and anterior scleral thickness (AST) in patients with subclinical keratoconus (SKC) and established keratoconus (KC). This single-center prospective case-control study included 97 eyes of 97 patients: 44 KC eyes, 14 SKC eyes, and 39 age- and axial length (AL)-matched healthy eyes. Using swept-source optical coherence tomography, the AST was manually measured in four directions and the CT was obtained automatically from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Principal component analysis (PCA) was used to linearly reduce the dimensionality of nine CT inputs to one significant component, CT1. A multivariate model was created to evaluate the association between CT1, AST, and several ocular parameters in SKC and KC patients. Partial correlation was then performed to adjust the confounding factors and to examine the effect of AST on CT1. The PCA showed that CT1 accounts for 86.54% of the total variance in the nine original CTs of the ETDRS grid. The CT1 model was associated with age, AL, and AST in the superior meridian in SKC eyes, whereas in KC eyes, it was correlated with gender, age, AL, and AST in the inferior meridian (p < 0.001). The partial correlation between CT1 and AST in the superior zone was found to be significant, positive, and strong in SKC eyes (r = 0.79, p = 0.019), whereas a significant, positive, and moderate correlation between CT1 and AST at the inferior zone (r = 0.41, p = 0.017) was observed in KC eyes. Choroidal tissue was significantly correlated with the anterior sclera across the vertical meridian. This relationship was observed over the superior sclera in SKC eyes, whereas in established KC, it was over the inferior sclera. These results reveal new insights regarding the interactions between the anterior and posterior structures of the KC eyes and confirm the enigma of the pathophysiology of KC.

Corneal Layer Thickness Mapping With Optical Coherence Tomography in Different Stages Reveals Pathologic Processes of Keratoconus.

The aim of this study was to characterize the corneal layer thickness profile in different stages of keratoconus (KC). Patients with clinical or subclinical KC without a history of contact lens use were retrospectively enrolled. We evaluated 164 eyes, including 69 clinical KC, 32 topographic KC (no clinical signs), 22 very asymmetric ectasia with normal topography and no clinical signs of ectasia (VAE-NT), and 41 control eyes. The corneal epithelial, stromal, and total thicknesses in a 10-mm diameter were evaluated using swept-source anterior segment optical coherence tomography. The epithelial thickness in the control and VAE-NT groups was thicker inferiorly than superiorly. While epithelial thickness parameters between the VAE-NT and control groups did not differ, significant stromal thinning was observed in the paracentral inferior and midperipheral temporal areas. The epithelium in the topographic and clinical KC groups was thinner than that in the control and VAE-NT groups, with focal thinning of the epithelium in the inferior-temporal area. In clinical KC, stromal thinning increased mainly in the central and paracentral inferior/temporal areas. With KC progression, the thinnest epithelial points tended to be placed temporally and inferiorly. Corneal layer thickness mapping using swept-source optical coherence tomography in a 10-mm diameter cornea across various severities of KC, from very mild to advanced, revealed that epithelial and stromal thicknesses changed with KC severity and was involved in the pathogenesis of KC progression. Pathological changes in the stroma may precede those in the epithelium. Epithelial compensatory mechanisms in clinical and topographic KC may not have fully emerged in VAE-NT.

Corneal biomechanics in patients with allergic conjunctivitis.

Allergic conjunctivitis (AC) comprises a group of conditions triggered by environmental allergens, substantially diminishing the quality of life, particularly among children and adolescents. The mechanical impact of eye rubbing in patients with AC is known to induce biomechanical alterations in the cornea. Modern instruments enable the detection and quantification of these corneal biomechanical changes. The ocular response analyzer and CorVis ST have become standard tools for assessing corneal biomechanical properties. We conducted a review of studies that have investigated corneal biomechanics in patients with AC using both devices to elucidate the association between corneal biomechanical changes and early ectasia development. Our analysis highlights significant findings regarding the tomographic biomechanical index parameter in corneal biomechanics among patients with AC. These findings underscore the importance of ocular screening for all patients to promptly detect subclinical keratoconus changes, thereby improving disease management and outcomes.

Insights into atypical segmental layer thicknesses and phase retardation in thick corneas using ultrahigh-resolution polarization-sensitive optical coherence tomography

BackgroundAccurately assessing corneal structural status is challenging when thickness deviates from the average. Polarization-sensitive optical coherence tomography (PS-OCT) measures tissue-specific polarization changes, providing additional contrast for accurate segmentations and aids in phase retardation (PR) measurements. Previous studies have shown PR's effectiveness in identifying sub-clinical keratoconus (KC) in asymmetric cases. Thus, this study aims to assess PR distribution in thick corneas with and without KC.MethodsIn this retrospective and cross-sectional study, 45 thick corneas from 30 Asian-Indian subjects, categorized into healthy (n = 26) and KC (n = 19) groups were analyzed. All eyes underwent standard clinical evaluations, tomographic assessments, and corneal biomechanics measurements. PR and individual layer thicknesses were measured using custom-designed ultrahigh-resolution PS-OCT. PR en-face maps were generated. Individual layer thicknesses and PR analysis was conducted across multiple zones, extending up to 8–10 mm in diameter. All eyes in the study had not undergone interventions, received topical medications, or had previous corneal disease history.ResultsSignificant differences were found in spherical and cylindrical powers, keratometry, pachymetry, and biomechanical indices (all P < 0.01). Thickness profiles from PS-OCT showed significant differences in the 4–8 mm zones only. Bowman's layer thickness significantly differed only in the central 2 mm zone (P = 0.02). The median PR values showed marginal differences in the central 2 mm zone (P = 0.0565). Additionally, there were significant differences observed in the 2–4 mm and 4–6 mm zones (P = 0.0274 and P = 0.0456, respectively). KC eyes exhibited an atypical PR distribution and corneal thinning, while normal eyes maintained a uniform Bowman’s layer thickness and PR maps with larger areas of higher PR.ConclusionThe study revealed distinctive PR distribution in thick corneas among healthy and KC groups. Using an ultrahigh-resolution PS-OCT the significance of Bowman's layer thickness in these groups was also emphasized. The study offered potential improvements in clinical diagnostics by enhancing our understanding of corneal structure and its altered function.

Combined corneal biomechanical and tomographical indices in subclinical and forme fruste keratoconus.

Evaluation of combined corneal tomographic and biomechanical parameters in subclinical/forme fruste keratoconus (ScKC/FFKC). Cross-sectional observational case-control study. Thirty-one eyes with ScKC (fellow eye of KC with any one sign: keratometry >47 diopters, cylinder >1.5 D, central corneal thickness <500 µm, with/without abnormal topography) or FFKC (fellow eye of KC with normal topography and slit lamp examination) >13 years (cases) and 44 eyes of age-matched 22 healthy subjects (controls). Clinically diagnosed KC, presence of corneal scars, and prior ocular surgery eyes. Sixteen Pentacam, 15 Corvis ST, and five Sirius parameters were analyzed using paired sample t -test, and a subsample found to be significantly different was used in receiver operating characteristic curve analysis. The Youden index was calculated, and Pearson's correlation analysis was done. Five Pentacam, three Corvis ST, and two Sirius parameters had an area under curve (AUC) >0.75. Tomographic and biomechanical index (TBI) (cutoff 0.59, 95% specificity, 77% sensitivity), Belin Ambrosio enhanced ecstasia display (cutoff 1.8, 81% specificity, 80% sensitivity), and symmetry index of posterior corneal curvature (cutoff 0.16, 97% specificity, 67% sensitivity) best identified early KC. TBI strongly correlated with maximum Pentacam parameters in both cases and controls. Corvis biomechanical index strongly correlated only in cases, and SP-A1-SD weakly correlated in cases. Upon combined analysis, the average sensitivity and specificity, respectively, of top three parameters (according to AUC) from Pentacam and Corvis ST were 74.1% and 95.4% for posterior elevation and TBI. The trial was registered in Clinical Trial Registry of India on January 28, 2022. The Trial Registration Number is REF/2022/01/050638.

Implantation of phakic intraocular lenses in patients with stabilized keratoconus

To date, extensive experience has been accumulated in the correction of high myopia and myopic astigmatism through the implantation of additional negative lenses (phakic intraocular lenses). However, the use of this method in patients with anatomically altered corneas due to keratoconus remains unresolved.Purpose: to assess the effectiveness and safety of correcting high myopia combined with myopic astigmatism by implanting phakic intraocular lenses in patients with stabilized keratoconus at stages 1–2.Materials and methods. The study encompassed results from 27 surgeries involving the implantation of phakic intraocular lenses in patients with high myopia and myopic astigmatism (12.63 ± 4.25 D). These patients had thin corneas and were diagnosed with stage 1–2 keratoconus after undergoing corneal collagen crosslinking treatment – this constituted the main group. The control group comprised 35 surgeries performed on patients with subclinical non-progressive keratoconus (Forme Fruste). All participants underwent evaluations for visual acuity dynamics and refractive stability of spherical and cylindrical components before surgery, immediately post-surgery, and then at 1, 6, and 12 months after implantation. Additional assessments included intraocular pressure measurements, gonioscopy, ultrasonic echobiometry, ultrasonic ophthalmoscopy, biomicroscopy, ophthalmoscopy, endothelial microscopy, vision character and stereopsis determination, ultrasound biomicroscopy, anterior segment optical coherence tomography, electrophysiological studies, and statistical analysis. An IPCL (a type of phakic intraocular lenses made from hydrophilic acrylic) was implanted, capable of correcting myopia up to 30 D and astigmatism up to 10 D.Results. All patients achieved high uncorrected visual acuity 0.86 ± 0.11. Astigmatism correction was successful in 96% of cases. The average postoperative vault – the distance from the back surface of the phakic intraocular lenses to the anterior lens capsule – was 527.5 ± 40.27 μm (range 460–600 μm), and the intraocular pressure was 11.7 ± 2.08 mm Hg. There was a minor decrease in corneal endothelial cell count from 2599 ± 157.3 to 2375 ± 125.3 cells/mm² in the first group and from 2614 ± 104.8 to 2375 ± 43.3 cells/mm² in the second group respectively (p &gt; 0.05), which falls within the acceptable loss range of 4–7% from preoperative values for both groups. Throughout the observation period, there were no cases of cataract development, pigmentary glaucoma, pupillary block, or other vision-threatening complications.Conclusions. Implantation of phakic intraocular lenses in patients with early-stage stabilized keratoconus and subclinical non-progressive keratoconus provides an effective and practically safe means of correcting high myopia and astigmatism.

Изучение вязкоэластичных свойств роговицы у пациентов с субклиническим кератоконусом

Abstrakt Corneal viscoelastic properties in patients with subclinical keratoconus I.V. Dutchin, E.L. Sorokin, Yu.V. Kutuzova, Ia.E. Pashentsev Fyodorov Eye Microsurgery Federal State Institution, Khabarovsk Branch, Khabarovsk, Russian Federation Far-Eastern State Medical University, Khabarovsk, Russian Federation Purpose. To evaluate corneal viscoelastic properties in subclinical keratoconus (SKC), analysis of its association with corneal thickness, and degree of risk of iatrogenic corneal ectasia. Material and methods. The main group consisted of 21 patients with signs SKC according to Pentacam (Oculus, Germany). The control group consisted of 21 patients without signs of subclinical SKC. In both groups, moderate myopia prevailed; groups were comparable in age and gender. A comparative statistical analysis of parameters of topography system Pentacam and corneal viscoelastic properties using the Corvis ST (Oculus, Germany) was carried out. Results. In the main group, the values: Corneal Applanation Velocity1, the Deformation Amplitude, and the Tomographic and Biomechanical Index (TBI) were statistically significantly higher compared to the control group. The values of the radius and the corneal central thickness, on the contrary, had statistically significantly lower values than in the control group. According to the values of the TBI (from 0 to 0.28), in the control group there was a «no obvious risk» of postoperative ectasia. In the main group, the average value of the TBI (0.43) was much higher than in the control group, which indicates weakened protective frames of cornea and risk of iatrogenic corneal ectasia in case of refractive surgery. There was no relationship between corneal thickness and TBI in the main group: r= –0.34 (p=0.13). Despite the signs of SKC in the main group, according to Pentacam, in 74% of eyes the corneal viscoelastic properties had sufficient rigidity for keratorefractive surgery. Conclusion. When selecting patients for keratorefractive surgery, along with assessing the parameters of corneal topography, it is also necessary to evaluate the corneal viscoelastic properties. Key words: subclinical keratoconus; fruste keratoconus; corneal viscoelastic properties, corneal biomechanical properties; iatrogenic corneal ectasia

Combined DSAEK With Cataract Surgery in a Patient With Fuchs Endothelial Corneal Dystrophy and Keratoconus After Corneal Crosslinking

Purpose: To report a combined Descemet stripping automated endothelial keratoplasty (DSAEK) with cataract surgery in a case of Fuchs endothelial corneal dystrophy (FECD) and keratoconus after corneal crosslinking combined with photorefractive keratectomy. Methods: We report a case of a 56-year-old woman with a history of subclinical keratoconus who underwent corneal crosslinking (CXL) plus 7 years ago. At presentation, the patient complained of blurry vision, which was more prominent in the morning over the past few years, and frequent changes of spectacle prescription ever since the initial treatment with CXL plus. Post-CXL plus corneal tomographies revealed progressive corneal flattening of 6.20 diopters (D) and 6.50 D in the right (OD) and left (OS) eye, respectively, in terms of mean keratometry values over a period of 7 years, which resulted in significant hyperopia. Corrected distance visual acuity (CDVA) at presentation was 20/50 in the OD and 20/200 in the OS. Slit-lamp examination revealed guttae (diagnosis of FECD) with associated posterior corneal edema and advanced nuclear sclerotic cataracts in both eyes. Combined DSAEK with cataract surgery was performed on the left eye. Results: One year after the combined procedure, CDVA improved to 20/25, with the correction of (−0.25, −4.25 × 25). Slit-lamp examination revealed a clear cornea without evidence of corneal edema or scarring. Corneal tomography indicated discontinuation of the corneal flattening in the left eye while the fellow eye continued to flatten. Conclusions: Combined DSAEK with cataract surgery provides an effective surgical option for patients with FECD after CXL plus procedures for keratoconus, offering fast visual rehabilitation and functional visual outcomes.

Utility of artificial intelligence in the diagnosis and management of keratoconus: a systematic review.

The application of artificial intelligence (AI) systems in ophthalmology is rapidly expanding. Early detection and management of keratoconus is important for preventing disease progression and the need for corneal transplant. We review studies regarding the utility of AI in the diagnosis and management of keratoconus and other corneal ectasias. We conducted a systematic search for relevant original, English-language research studies in the PubMed, Web of Science, Embase, and Cochrane databases from inception to October 31, 2023, using a combination of the following keywords: artificial intelligence, deep learning, machine learning, keratoconus, and corneal ectasia. Case reports, literature reviews, conference proceedings, and editorials were excluded. We extracted the following data from each eligible study: type of AI, input used for training, output, ground truth or reference, dataset size, availability of algorithm/model, availability of dataset, and major study findings. Ninety-three original research studies were included in this review, with the date of publication ranging from 1994 to 2023. The majority of studies were regarding the use of AI in detecting keratoconus or subclinical keratoconus (n=61). Among studies regarding keratoconus diagnosis, the most common inputs were corneal topography, Scheimpflug-based corneal tomography, and anterior segment-optical coherence tomography. This review also summarized 16 original research studies regarding AI-based assessment of severity and clinical features, 7 studies regarding the prediction of disease progression, and 6 studies regarding the characterization of treatment response. There were only three studies regarding the use of AI in identifying susceptibility genes involved in the etiology and pathogenesis of keratoconus. Algorithms trained on Scheimpflug-based tomography seem promising tools for the early diagnosis of keratoconus that can be particularly applied in low-resource communities. Future studies could investigate the application of AI models trained on multimodal patient information for staging keratoconus severity and tracking disease progression.

Longitudinal Analysis of Corneal Biomechanics of Suspect Keratoconus: A Prospective Case-Control Study.

To evaluate the corneal biomechanics of stable keratoconus suspects (Stable-KCS) at 1-year follow-up and compare them with those of subclinical keratoconus (SKC). This prospective case-control study included the eyes of 144 patients. Biomechanical and tomographic parameters were recorded (Corvis ST and Pentacam). Patients without clinical signs of keratoconus in both eyes but suspicious tomography findings were included in the Stable-KCS group (n = 72). Longitudinal follow-up was used to evaluate Stable-KCS changes. Unilateral keratoconus contralateral eyes with suspicious tomography were included in the SKC group (n = 72). T-tests and non-parametric tests were used for comparison. Multivariate general linear models were used to adjust for confounding factors for further analysis. Receiver operating characteristic (ROC) curves were used to analyze the distinguishability. The biomechanical and tomographic parameters of Stable-KCS showed no progression during the follow-up time (13.19 ± 2.41 months, p > 0.05). Fifteen biomechanical parameters and the Stress-Strain Index (SSI) differed between the two groups (p < 0.016). The A1 dArc length showed the strongest distinguishing ability (area under the ROC = 0.888) between Stable-KCS and SKC, with 90.28% sensitivity and 77.78% specificity at the cut-off value of -0.0175. The A1 dArc length could distinguish between Stable-KCS and SKC, indicating the need to focus on changes in the A1 dArc length for keratoconus suspects during the follow-up period. Although both have abnormalities on tomography, the corneal biomechanics and SSI of Stable-KCS were stronger than those of SKC, which may explain the lack of progression of Stable-KCS.

Alterations in Corneal Sensitivity, Staining and Biomechanics of Alopecia Areata Patients: Novel Findings in a Case-Control Study.

Background: A higher prevalence of ophthalmological alterations in systemic inflammatory diseases has been demonstrated. Objectives: Our objectives were to determine anterior segment findings and corneal properties in alopecia areata (AA). Methods: This is a case-control study. Severe AA patients (Severity of Alopecia Tool > 50%) and non-AA subjects underwent a general ophthalmological examination, a Pentacam and Corvis scheimpflug technology examination (Oculus Optikgeräte GmbH, Wetzlar, Germany). Visual acuity, refractive error, corneal aesthesiometry, and biomechanical and topographic variables were registered. Results: In total, 25 AA patients (50 eyes; 50.6 ± 8.1 years) and 29 controls (58 eyes; 49.4 ± 8.6 years) were included. AA patients had decreased corneal sensitivity, more corneal staining, and a more advanced cataract (p ≤ 0.004). The anterior topographic flat meridian, mean anterior keratometry, and maximum keratometric point were increased in AA (p ≤ 0.040), while pachymetry values were thinner (p ≤ 0.001). Keratoconus index and Belin/Ambrosio-enhanced ectasia total deviation display were increased (p ≤ 0.007). Two eyes with a topographic diagnosis of keratoconus and four eyes with subclinical keratoconus were detected in AA. Applanation lengths were smaller in AA (p ≤ 0.029). The Corvis Biomechanical Index was increased in AA (p = 0.022). Conclusions: AA patients have reduced corneal sensitivity and increased corneal staining. Topographic and biomechanical parameters are altered, and there could be a higher risk of keratoconus, thus possibly requiring routine ophthalmological examination.

Research hot spots and trends of keratoconus in China: a bibliometric analysis

Objective: To review the studies related to keratoconus in China, investigate research hotspots and development trends in this field, and provide reference for future research. Methods: This is a bibliometrics study. The relevant literature written in Chinese was retrieved from the WanFang DATA and the China National Knowledge Infrastructure, English articles were collected from the Web of Science Core Collection database. Searched for journal articles related to keratoconus VOSviewer software, CiteSpace, and Bibliometrix in the R language were employed to create the knowledge map. The analysis encompassed the distribution of published journals, research collaboration networks of countries/regions, institutions, and authors. Additionally, core authors, high-frequency keyword co-occurrence, keyword topic maps, and keyword emergence time ranking were examined. Results: The study ultimately included 1 100 Chinese articles and 668 English articles. Chinese literature and English literature began to increase in 1997 and 2009, respectively, indicating that the field is currently in a developmental stage. The publications involved 244 Chinese journals and 150 English journals, predominantly in the field of ophthalmology. The United States collaborated the most with China, contributing to 123 articles, followed by other countries such as the United Kingdom and Switzerland. Chinese literature and English literature involved 552 and 883 institutions, respectively. The institution with the highest number of Chinese literature publications was the Eye Institute of Shandong First Medical University (63 papers), while Wenzhou Medical University had the highest number of English literature publications (91 papers). Chinese literature involved 2 435 authors, and English literature involved 2 073 authors. The largest collaboration cluster in Chinese literature was formed by the teams of Xie Lixin and Shi Weiyun, while the Gao Hua team formed the largest cluster in English literature. However, collaboration between authors was primarily limited to within each team. A total of 622 and 1 611 keywords were extracted from Chinese and English literature, respectively. The node centrality of the four Chinese keywords, "keratoconus", "cornea", "corneal transplantation" and "myopia" as well as the three English keywords, "keratoconus", "collagen cross-linking" and "penetrating keratoplasty" was greater than 0.1. "Collagen", "riboflavin", "corneal transplantation" and "ultraviolet A" were identified as common core hotspots and important research topics in Chinese and English literature on keratoconus. Keyword emergence analysis indicated that the keywords with the highest intensity of emergence in Chinese and English literature were "myopia" (13.54) and "penetrating keratoplasty" (9.99), respectively. The longest emergence time was observed for "contact lenses" (1995-2006) and "penetrating keratoplasty" (2003-2014). Conclusions: At present, research on keratoconus in China is on the rise, with research hotspots including pathogenesis, various new surgical methods, and improvement in quality of life. The future research trend mainly focuses on early diagnosis and screening methods, artificial intelligence, biomechanical examination, subclinical keratoconus, and small incision lenticule extraction.

Subclinical Keratoconus in an Adult with Mitochondrial DNA Mutation m.3243A&gt;G

Subclinical Keratoconus in an Adult with Mitochondrial DNA Mutation m.3243A&gt;G

Corneal Biomechanical Properties to Predict Prognosis of Abnormal Tomographic Corneas: A Prospective Cohort Study

To analyze the corneal biomechanical properties in patients with abnormal corneal tomography (ACT) and predict their stability using the biomechanical stability index (BSI). Prospective cohort study. Setting: Multicenter study. This study included 385 eyes of 278 patients with stable ACT (n = 70), subclinical keratoconus (SKC, n = 65), keratoconus (n = 65), normal controls (NL, n = 142). Forty-three eyes with first-visit ACT were included in a separate cohort (follow-up ACT group). Tomographical and biomechanical parameters (Pentacam and Corvis ST) were recorded. Nonparametric tests were used for comparison. Logistic regression was employed to introduce BSI to separate stable ACT and SKC accurately. An independent dataset of 43 first-visit ACT eyes was followed up for 1 year to validate BSI's accuracy and positive and negative predictive values (PPV, NPV). The tomographical and biomechanical parameters in patients with Stable ACT remained stable over the follow-up period (12.73 ± 2.57 months, P > .05). Stable ACT had 12/14 biomechanical parameters different (P < .05) from SKC but not different from NL (P > .05). With a cut-off value of 0.585, BSI demonstrated the strongest ability to distinguish between stable ACT and SKC (area under the receiver operating characteristic curve = 0.991), with 93.85% sensitivity and 97.14% specificity. During the 1-year follow-up of 43 eyes (follow-up ACT group), 30 remained stable. The accuracy, PPV, and NPV of the BSI were 95.35%, 100%, and 93.75%, respectively. Biomechanical properties of patients with stable abnormal tomography corneas were stronger than SKC and close to normal corneas, which may explain the reason for tomographic stability. The BSI may be useful for predicting disease progression in patients with ACT and the possible management of corneal cross-linking at the first visit.

Comparison of waveform‐derived ORA parameters in clinical keratoconus, subclinical keratoconus and healthy subjects

Aims/Purpose: The aim of this study was to comparison of waveform‐derived Ocular Response Analyser (ORA) parameters in clinical keratoconus (KC), subclinical keratoconus (SKC) and healthy subjects.Methods: This retrospective comparative case series study included 24 eyes with SKC, 24 eyes with KC and 48 eyes of age‐ and sex‐matched healthy subjects. Keratoconus diagnosis was based on clinical examinations, and Scheimpflug corneal tomography. SKC was defined as the presence of the following: (1) normal biomicroscopic findings and topography; (2) anterior (≤7 μm) and posterior (≤16 μm) elevation difference map marked green or yellow; (3) mean keratometry &lt;47D; (4) BAD‐D value &lt;3 SD and (5) keratoconus in the fellow eye. Thirty‐seven parameters derived from the waveform signal obtained with ORA were analysed. The Kruskal‐Wallis H test with Bonferroni correction was used for comparisons. p &lt; 0.05 was considered statistically significant.Results: While the rate of females in all groups was 33.3%, the mean age was 25.6 ± 0.9, 25.8 ± 1.3 and 25.7 ± 0.8 years in KC, SKC and healthy subjects, respectively. Statistically significant differences between KC and healthy eyes were found in p1area (p = 0.005), p2area (p &lt; 0.001), w1 (p = 0.001), w2 (p = 0.002), path1 (p = 0.032), path2 (p &lt; 0.001), aplhf (p = 0.018), p1area1 (p = 0.021), p2area1 (p &lt; 0.001), w11 (p = 0.028), w21 (p = 0.001), and path21 (p &lt; 0.001). While there were significant differences in w2 (p = 0.016), w21 (p = 0.042), and path21 (p = 0.033) parameters between SKC and healthy eyes, no significant difference was found between SKC and KC eyes.Conclusions: Approximately one‐third of the waveform‐derived ORA parameters can be used to differentiate between KC and healthy subjects. Parameters derived from the second applanation signal of ORA were superior in distinguishing SKC from healthy subjects.

Detecting Keratoconus in Adolescents with Anterior Segment Optical Coherence Tomography.

Assessing the applicability of an algorithm developed for keratoconus detection in adolescents. This algorithm relies on optical coherence tomography (OCT) and incorporates features related to corneal pachymetric and epithelial thickness alterations. We retrospectively reviewed charts of patients under the age of 18 and divided them into four groups according to the Belin-Ambrosio display (Pentacam): normal, manifest, and subclinical keratoconus, as well as very asymmetric eye with normal topography and tomography (VAE-NTT). Corneal and epithelial thickness maps (Cirrus 5000 HD-OCT, Carl Zeiss Meditec, Germany) were evaluated by a human grader. In the first step, if at least one of four parameters (pachymetry minimum (pachy min), pachy minimum-median (min-med), pachy superonasal-inferotemporal (SN-IT), or epithelial (epi SN-IT)) exceeded its cut-off value, the eye was considered as suspect. In the second step, the combined presence of coincident thinning of total cornea and epithelium as well as concentric epithelial thinning lead to the diagnosis of keratoconus. Receiver operating characteristic (ROC) curves were generated to determine area under the curve (AUC), sensitivity, and specificity for the parameters. The study involved 19 pediatric patients diagnosed with keratoconus, comprising 29 manifest keratoconic eyes, 3 eyes with subclinical keratoconus, and 5 VAE-NTT eyes. In addition, 22 eyes from 11 normal adolescents were included in the analysis. The AUC values of parameters in step 1 were 0.889 for pachy min, 0.997 for pachy min-med, 0.893 for pachy SN-IT, and 0.998 for epi SN-IT. When both steps were performed, this algorithm captured all manifest and subclinical pediatric keratoconic eyes. When all eyes of the keratoconus patients were combined, step 1 had 97.3% sensitivity and step 2 had 100% specificity. Using this OCT-based approach in adolescents yielded a high level of agreement with the current gold standard, tomography. Using them together, potentially also with other examinations may improve the diagnostic accuracy of KC in the pediatric population. Integration of this approach into the software of the device to facilitate automated evaluations is desired.

Evaluation of Macular and Choroidal Thickness in Patients with Subclinical Keratoconus

Evaluation of Macular and Choroidal Thickness in Patients with Subclinical Keratoconus