Corneal Tomography Research Articles

Corneal Biomechanical Changes in Patients with Inherited Retinal Diseases.

Inherited retinal diseases (IRDs) are a group of degenerative disorders of the retina, that can be potentially associated with changes in the anterior segment, but their prevalence and impact are not known. Exploring these concomitant ophthalmologic changes with biomechanical assessment may help identify other non-retina causes of vision loss in these patients, such as corneal ectasia or susceptibility to glaucoma. This study aimed to measure and compare corneal biomechanics in patients with and without IRDs. A total of 77 patients (154 eyes) with IRD were recruited as the study group. The control group consisted of 77healthy adults (154 eyes) with matched age and sphere equivalents. All participants underwent a comprehensive assessment including corneal tomography (Pentacam®) and biomechanical assessment (Corvis ST®). A total of 4 second-generation biomechanical parameters and 3 indexes were collected: Ambrosio Relational Thickness (ARTh), Deflection Amplitude Ratio Max (DARM), Integrated Radius (IR) and Stiffness Parameter at Applanation (SP-A1), the final deviation value D of the Belin/Ambrosio Enhanced Ectasia Display (BAD-D), Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI). For IRD patients, there was a higher DARM (p < 0.001), lower ARTh (p < 0.001), higher CBI (p < 0.001), higher TBI (p<0.001), and higher BAD-D (p < 0.001) compared to the control group. Regarding discrimination of healthy subjects and IRD patients, ARTh was the most sensitive parameter. The results showed that IRD patients tend to have softer corneal behaviour, compared to eyes without pathology, which may predispose patients to corneal ectasia or glaucoma development. ARTh could be used to screen IRD patients if a non-retina cause of vision loss is suspected.

Corneal epithelial ingrowth after small incision lenticule extraction surgery: Insights from a case series and mechanistic studies

AbstractCorneal epithelial ingrowth (EI) is a rare but significant complication following Small Incision Lenticule Extraction (SMILE) surgery. During the procedure, the opaque bubble layer (OBL) formation may create microchannels that disrupt Bowman's layer, providing a pathway for epithelial cells to migrate into the corneal stroma. In this study, we investigated the mechanisms behind EI development and proposed preventive strategies. We analyzed four cases of EI post‐SMILE surgery, utilizing anterior segment optical coherence tomography (AS‐OCT) and corneal tomography for diagnosis. Preventive measures, including careful anesthetic application and precise suction cone positioning, were employed to minimize OBL formation. Here, we show that subflap debris removal surgery led to significant clinical improvement, with no EI recurrence observed. Our findings suggest that the microchannels created by OBL during surgery may play a crucial role in EI development, challenging previous assumptions that EI is primarily due to trauma at the flap edges. This underscores the importance of precise surgical technique and effective postoperative management. Further research, including clinical studies and advanced imaging, is needed to confirm this proposed mechanism and improve outcomes in refractive surgery. The study highlights the necessity for ongoing advancements in surgical protocols and technology to prevent and manage EI effectively.

Anpassung von Skleral-Kontaktlinsen bei Terrien‘s marginaler Hornhautdegeneration

Purpose. This case report describes the possible visual rehabilitation with scleral lenses of a patient with Terrien’s marginal degeneration with different degrees of progression between the right and left eye. Material and Methods. Scleral contact lenses were fitted with the help of corneal tomography and by observing and assessing the fit of measuring lenses. A slit lamp with a corresponding camera helped to modify the diagnostic lenses. Results. In this case, the fitting of scleral contact lenses resulted in an improvement in distance vision in both the right and left eye. Near vision could not be evaluated at the time of writing. Conclusion. Scleral contact lenses can be a good alternative to glasses for complex corneas to improve visual performance. It is recommended to use a slit lamp with a camera to make it easier to discuss scleral contact lenses modifications with the manufacturer of the lenses. Keywords: TERRIEN’S MARGINAL CORNEAL DEGENERATION, PELLUCIDE MARGINAL CORNEAL DEGENERATION, SCLERAL LENSES

Pachychoroid pigment epitheliopathy in keratoconic eyes.

To report the association between keratoconus (KC) and pachychoroid pigment epitheliopathy (PPE). As secondary outcome, we explored the relation between subfoveal choroidal thickness (SFCT) and topometric indexes. Retrospective, observational, cross-sectional, case-control study. Multicentric study including patients with KC and healthy controls. Each subject underwent a complete ophthalmological visit, Placido-based corneal topography, Scheimpflug corneal tomography and spectral-domain OCT (SD-OCT) with the enhanced depth imaging (EDI) mode on. Linear mixed models (LMM) were employed for comparison between groups, and to examine the impact of different topometric factors on SFCT. KC stages were defined according to Belin grading. Overall, 56 eyes from 35 KC patients and 52 eyes from 27 healthy, age- and axial length-matched control subjects were included in the study. PPE was found in 10 (17.9%) eyes from 8 KC patients, whereas was absent in all healthy controls. SFCT was statistically significantly higher in keratoconic eyes (median: 390µm; interquartile range (IQR): 339 - 425µm) compared to healthy eyes (median: 240µm; IQR: 200 - 288µm) (p < 0.001). SFCT did not differ across different KC stages and between keratoconic eyes with and without PPE. PPE is a relatively frequent finding in eyes with KC, being present in about 1 out of 6 cases, regardless of disease stage. What is known: Keratoconus (KC) is a corneal disorder commonly associated with other chorioretinal abnormalities. It is well known that keratoconic eyes display increased choroidal thickness, and the rare association between KC and central serous chorioretinopathy (CSC) has already been reported in the literature. We identified an association between KC and pachychoroid pigment epitheliopathy (PPE), a precursor or forme fruste of pachychoroid diseases, such as CSC. PPE presence is independent from corneal parameters and is observed in about 1 out 6 KC eyes.

Surgical Strategies to Manage Stromal Interface Irregularity Following Deep Anterior Lamellar Keratoplasty.

The purpose of this study was to describe the various surgical approaches to manage stromal interface irregularity following deep anterior lamellar keratoplasty (DALK). This interventional case series included patients requiring repeat keratoplasty procedures for stromal interface opacity and/or irregularity following DALK. The following surgical techniques with the aim of restoring transparency and regularity of the central optical zone and improving visual acuity in eyes that underwent unsuccessful DALK were performed: 1) simple anterior lamellar graft exchange, 2) repeat DALK with pneumatic dissection, 3) repeat DALK with deepening of manual lamellar dissection, 4) small diameter stripping of the central stroma-endothelium-Descemet complex and its replacement with a new endothelial lamella, and 5) 2-piece microkeratome-assisted mushroom penetrating keratoplasty. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), slit-lamp examination, tonometry, and anterior corneal tomography were evaluated preoperatively, as well as 3, 6, and 12 months after surgery. Intraoperative and postoperative complications were recorded. Preoperative BCVA was less than 20/200 and improved to 20/40 or better in all cases, reaching 20/20 in 1 patient. Corneal clarity was restored in all eyes, and no recurrence of underlying disease was observed. No intraoperative or postoperative complications were reported. This case series describes several successful surgical approaches to improve the transparency and regularity of stromal interface obtained after a DALK procedure; the choice of the technique should be customized for the single eyes to still maintain the advantages of lamellar or minimally invasive grafts.

Screening Preadolescents for Keratoconus Risk Factors in a Low-Resource Setting.

Diagnosis of keratoconus (KC) involves the identification of corneal signs, refraction, and corneal imaging. The prevalence of KC ranges between 0.4 per 100,000 and 4,790, depending on geographical location and ethnicity. Diagnosis of KC should occur early for appropriate management with relatively affordable, accessible options to prevent visual impairment in low-income settings. Written consent and assent were obtained from subjects before a questionnaire was administered to collate demographics, general and ocular history of subjects, and keratoconus risk factors. A novel scoring system was applied to identify subjects at a higher risk of developing KC and document KC risk factors prevalent in Harare using an informed risk score calculation. Thousand one hundred fifty-three subjects aged between 6 and 12 years were seen. The prevalence of KC was found to be 626/100,000 in primary school children resident in Harare. Reduced visual acuity, vernal keratoconjunctivitis, itchy eyes, eye rubbing, and atopy are the most prevalent KC risk factors identified in this community. Informed risk score calculation proved valuable in the screening for KC. The prevalence of KC in primary school children in Harare is 626/100,000, which is relatively high. School-aged children stand to benefit from the early screening for KC based on evidence-based practices in the absence of advanced clinical instrumentation.

Machine Learning-Based Identification of Risk Factors of Keratoconus Progression Using Raw Corneal Tomography Data.

The purpose of this study was to identify early indicators of keratoconus progression in Pentacam data using machine learning (ML) techniques. A retrospective Pentacam tabular data set was created by retrieving 11,760 tomography tests performed in patients with keratoconus. Data for eyes labeled unstable based on their referral for cross-linking were differentiated from data for eyes labeled stable and not referred for follow-up procedures. A boosted decision tree was trained on the final data set using a cross-validation method. The final labeled data set included 1218 tomography tests. Training a ML model on a single test for each eye did not accurately predict disease progression, as indicated by the mean receiver-operating characteristic area under the curve of 0.59 ± 0.1, with precision of 0.27, recall of 0.3, and F1 score of 0.28. Training on serial tests for each eye included 819 tomography scans and yielded good prognostic abilities: a receiver-operating characteristic area under the curve of 0.75 ± 0.07, precision of 0.32, recall of 0.67, and F1 score of 0.43. In addition, 4 of the 55 Pentacam raw data parameters predominantly used the algorithm decision: age, central keratoconus index, Rs B, and D10 mm pachy. This study revealed specific dominant parameters attributing to the classification of stability, which are not routinely assessed in determining progression in common practice. Using ML techniques, keratoconus deterioration was evaluated algorithmically with training on multiple tests, yet was not predicted by a single tomography test. Hence, our study highlights novel factors to the current consideration of cross-linking referral and may serve as a supportive tool for clinicians.

The prevalence of refractive errors and corneal topographic changes in unilateral congenital ptosis versus the fellow eye- A cross-sectional study

The drooping upper eyelid in ptosis induces pressure on the eyelid and the same has been implicated to induce refractive errors. Very limited literature is available on the actual prevalence of corneal topographic changes and refractive errors seen in ptosis.Aim of this study was done to examine the effect of pressure of the upper eyelid on refractive errors and corneal topography in ptotic eyes and its comparison with fellow normal eyes. This was a cross-sectional observational study and included 83 patients with unilateral congenital ptosis. The study was conducted at NavJyoti Eye Hospital, Gorakhpur, Uttar Pradesh from Jul 2021- Feb 2023. Only unilateral cases of simple congenital ptosis were included in the study. Ptosis was evaluated to classify it into mild, moderate and severe. Retinoscopic refraction and corneal mapping for topography were done to get keratometric data, refractive errors, astigmatism and topographic patterns. The observations in ptotic eyes were compared with those in fellow normal eyes. Data was analyzed using the Statistical Package for Social Sciences (SPSS) version 20. P- value of &amp;#60; 0.05 was considered significant. Around 18 (21.69%) patients were found to have mild ptosis, 30 (36.14%) showed moderate and 35 (42.17) participants had severe ptosis. 16 (19.28%) ptotic eyes had myopia as compared to 10 (12.05%) non-ptotic eyes. 14 (16.86%) ptotic eyes were hyperopic as compared to 2 (2.41%) non-ptotic eyes. 38 (45.78%) ptotic eyes showed significant astigmatism (refractive) as compared to 5 (6.02%) non-ptotic eyes. 48 (57.83%) of ptotic eyes had significant Sim K (topographic) astigmatism as compared to 24 (28.92%) non-ptotic eyes. The prevalence of refractive errors was found to increase with the severity of ptosis. The majority of ptotic eyes 44 (53.01%) showed symmetrical bow tie pattern on corneal imaging (topography) whereas the most common pattern seen in non-ptotic eyes was round 33 (39.76%). Pressure from the upper eyelid in congenital ptosis induces significant corneal topographic changes and errors of refraction. Meticulous refraction and corneal topography should be done in all cases of congenital ptosis to timely detect astigmatism and suitable corrective measures should be instituted to prevent the development of amblyopia.

Duloxetine enhances PAX6 expression and suppresses innate immune responses in murine LPS-induced corneal inflammation

Background-aimPAX6 is a key regulator of eye development and epithelial homeostasis in the cornea. When deficient, chronic corneal inflammation, neovascularization and limbal stem cell deficiency can occur. Here we investigated the potential of duloxetine, a generic serotonin reuptake inhibitor that can upregulate PAX6 in vitro, for its in vivo activity in the context of corneal inflammation. MethodsDuloxetine tolerance was tested in a human limbal stem cell line and isogenic CRISPR-knockout PAX6+/− cells. C57BL/6-Wildtype mice were administered duloxetine eye drops at concentrations of 1 μM - 2 mM and tested for toxicity and corneal PAX6 expression. In LPS-induced corneal inflammation in mice, duloxetine's effect on PAX6 expression, corneal opacification and inflammatory responses were evaluated by in vivo corneal imaging, immunostaining, and whole-transcriptome microarray analysis. ResultsNo toxicity was observed in vitro for duloxetine concentrations up to 10μΜ. In vivo, duloxetine drops were well-tolerated up to 50 μM. Duloxetine drops at 10μΜ significantly upregulated PAX6 protein levels in the cornea by 30 % within 2 days. In the LPS model, duloxetine resulted in a sustained 33 % PAX6 protein upregulation in the cornea at 7 days, and in reduced opacity within 2 days, accompanied by a significant dampening of IL-17A signaling, neutrophil degranulation, microglial activation, macrophage markers, and MMP expression, despite non-significant changes in total inflammatory cell infiltration. ConclusionShort-term administration of a repurposed generic drug, duloxetine, upregulates PAX6 protein levels in the cornea of mice and exerts an anti-inflammatory activity by dampening innate immune responses.

Integrated line-field optical coherence tomography and scheimpflug imaging for corneal imaging

Previously we demonstrated a combined scanning-point optical coherence tomography (OCT) and Scheimpflug Imaging (SI) system, to provide cross-section images of the corneal layers and the whole anterior segment of the eye simultaneously. However, to fully realise the benefits of this dual imaging modality concept towards clinical practice, it is required that the OCT part of the system can achieve ultra-high axial resolution (<3 µm in air) and faster imaging speeds, without using prohibitively expensive components. To achieve this, a new imaging device integrating line-field OCT and SI, using a supercontinuum light source, is demonstrated. This line-field configuration enables both OCT and SI B-scan to be captured using the same light illumination in a single shot, which is the most significant improvement over single point scanning. This achieves an OCT axial resolution down to 2.1 µm in air (1.6 µm in corneal tissue) and an imaging speed up to 213 kA-Scans/s. Since the OCT and SI capture the identical corneal position and serve as cross-validation, this technique offers a great method for accurately determining the individual corneal thickness and refractive index, thereby minimizing individual variations, which can help determine the extent of cutting or correction needed in vision correction. Moreover, the precise measurement of corneal thickness provided by this technique allows for a better understanding of the biomechanical properties of the cornea. We demonstrate the efficacy of the proposed system by evaluating porcine and bovine eyes ex-vivo for determining the corneal refractive index and thickness.

The KERATO Biomechanics Study 1: A Comparative Evaluation Using Brillouin Microscopy and Dynamic Scheimpflug Imaging.

To assess the corneal biomechanical properties in normal individuals and patients with keratoconus using the Brillouin optical scanning system (Intelon Optics) (BOSS) and compare them with ultra-high-speed Scheimpflug imaging (Corvis ST; Oculus Optikgeräte GmbH). Sixty eyes from 60 patients (30 normal and 30 keratoconus) were included in this prospective, single-center, comparative, non-interventional study. Corneal biomechanics were evaluated using the Corvis ST and the BOSS. With the BOSS, each corneal image was acquired three times, measuring 10 locations within an 8-mm diameter. Parameters extracted included mean, maximum, and minimum Brillouin shift. These 10 points were also grouped into superior, central, and inferior regions. BOSS repeatability was assessed using the coefficient of repeatability and coefficient of variation. Furthermore, normal individuals and patients with keratoconus were compared using the Corvis ST and BOSS. The BOSS exhibited good repeatability, with coefficient of repeatability ranging from 0.098 to 0.138 GHz for single points in normal individuals and 0.096 to 0.149 GHz for patients with keratoconus. Statistical analysis revealed significant differences between normal individuals and patients with keratoconus, indicating softer corneas in keratoconus, observed with both the Corvis ST and BOSS. Specifically, the BOSS showed significant differences in mean, inferior, and superior mean, maximum, and minimum Brillouin frequency shift (all P < .05), whereas the Corvis ST displayed highly significant differences in stiffness parameter at first applanation, stress strain index, deformation amplitude ratio, and inverse integrated radius (all P < .001). Corneal biomechanical measurements proved highly repeatable and effectively demonstrated significant differences between normal individuals and patients with keratoconus using both the BOSS and the Corvis ST. [J Refract Surg. 2024;40(8):e569-e578.].

Multimodal Approach in Dry Eye Disease Combining In Vivo Confocal Microscopy and HLA-DR Expression.

The purpose of this study was to determine the association between corneal images provided by in vivo confocal microscopy (IVCM) with clinical parameters and conjunctival expression of HLA-DR antigen in patients with dry eye disease (DED). Two hundred fourteen eyes of 214 patients with DED were analyzed, consisting of 2 groups of patients - 63 with autoimmune dry eye disease (AIDED) and 151 with non-autoimmune dry eye disease (NAIDED). Patients underwent a full clinical examination, including symptom screening, using the Ocular Surface Disease Index (OSDI) questionnaire, and objective analysis of DED signs by Schirmer's testing, tear break-up time (TBUT), Oxford's test, and IVCM corneal imaging. The IVCM scoring criteria were based on corneal sub-basal nerve density (ND), nerve morphology (NM), and inflammatory cell (IC) density. Quantification of conjunctival HLA-DR antigen was performed by flow cytometry. The total IVCM score (T-IVCM) as well as the IVCM-IC subscore (sc) were positively correlated with HLA-DR levels with r = 0.3, P < 0.001 and r = 0.3, P < 0.01, respectively in the total population of patients with DED. The IVCM-NDsc was negatively correlated with TBUT in patients with AIDED (r = -0.2, P < 0.05) and with the Schirmer's test in patients with NAIDED (r = -0.24, P < 0.05). However, the IVCM-NMsc was positively correlated with the Oxford score only in patients with AIDED (r = 0.3, P < 0.05). The proposed IVCM scoring system showed significant correlations with clinical parameters along with conjunctival HLA-DR quantification in patients with DED. The IVCM grading score represents an interesting point of commonality among clinical parameters, imaging, and molecular investigation of the ocular surface.

Evaluation of the ocular surface with keratograph 5M analysis after scleral buckle surgery in patients with retinal detachment

ABSTRACT Background This study aims to evaluate the ocular surface health with oculus keratograph 5M (Oculus, Wetzlar, Germany) in patients, 4–6 weeks after the SB surgery. Research design and methods Adult patients with RRD who underwent SB surgery were enrolled. Subjects with the existence of any concomitant ophthalmologic diseases or topical medications that can affect the ocular surface were excluded. The ophthalmic examination and corneal imaging with oculus keratograph 5M were conducted 4–6 weeks after the surgery, following discontinuation of all topical medications. The ocular surface parameters were compared between the surgical and other eyes. Results The results showed a statistically significant difference in the ocular surface profile, including the tear meniscus height (TMH), Non-invasive keratograph breakup time (NIKBUT), Meibography, and Redness scores, between the surgical eye and the other eye four to six weeks after the procedure. Conclusion In this study, we showed convincing evidence of the role of keratography imaging in the objective evaluation of the ocular surface 4–6 weeks after SB surgery. We depicted that SB surgery disturbs the ocular surface homeostasis significantly, which can cause ocular discomfort as well as decrease visual function in patients in the post-up periods.

Inter-zonal epithelial thickness differences for early keratoconus detection using optical coherence tomography

PurposeTo develop and test a parameter for early keratoconus screening by quantifying the localized epithelial thickness differences in keratoconic eyes.MethodsThe cross-sectional study included 189 eyes of 116 subjects in total: 86 eyes of 54 keratoconus patients with bilateral ectasia and 40 eyes of 20 healthy subjects in the parameter-development dataset and 42 eyes of 21 keratoconus patients with asymmetric ectasia and 21 eyes of 21 healthy subjects in the parameter-validation dataset. Epithelial thickness maps were obtained using anterior segment optical coherence tomography and the inter-zonal epithelial thickness differences were calculated. The developed parameter was tested in keratoconus patients with asymmetric ectasia.ResultsCompared to healthy controls, the inferior-temporal and global inter-zonal epithelial thickness differences were higher not only in eyes with tomographically significant keratoconus (median [interquartile range] of 4.42 [3.13] µm vs. 0.78 [0.42] µm, p < 0.001, and 3.05 [1.51] µm vs. 1.07 [0.26] µm, p < 0.001, respectively), but also in tomographically normal keratoconus fellow eyes (1.36 [0.85] µm vs. 0.78 [0.42] µm, p = 0.005, and 1.31 [0.32] µm vs. 1.07 [0.26] µm, p = 0.01, respectively). The inferior-temporal inter-zonal epithelial thickness differences had an area under the receiver operating characteristic curve (95% confidence interval) of 0.991 (0.972–1) for detecting tomographically significant keratoconus and 0.749 (0.598–0.901) for differentiating between tomographically normal keratoconus fellow eyes and healthy controls.ConclusionsThe inter-zonal epithelial thickness differences are increased in keratoconus fellow eyes which still have a normal Scheimpflug corneal tomography, and therefore may serve as a useful parameter to detect early ectatic changes.

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.

Combined Rotating Ultra-High-Resolution Spectral Domain OCT and Scheimpflug Imaging for In Vivo Corneal Optical Biopsy.

This article introduces the Pentacam® Cornea OCT (optical coherence tomography). This advanced corneal imaging system combines rotating ultra-high-resolution spectral domain OCT with sub- 2-micron axial resolution and Scheimpflug photography. The purpose of this study is to present the first experience with the instrument and its potential for corneal diagnostics, including optical biopsy. In this prospective study, the Pentacam® Cornea OCT was used to image the corneas of seven patients. The novel wide-angle pericentric scan system enables optimal OCT imaging performance for the corneal layer structure over the entire width of the cornea, including the limbal regions. A detailed analysis of the resulting images assessed the synergism between the OCT and Scheimpflug photography. The Pentacam® Cornea OCT demonstrated significantly improved image resolution and ability to individualize corneal layers with high quality. There is a synergism between the OCT high-definition signal to individualize details on the cornea and Scheimpflug photography to detect and quantify corneal scattering. The noncontact exam was proven safe, user-friendly, and effective for enabling optical biopsy. Pentacam® Cornea OCT is an advancement in corneal imaging technology. The ultra-high-resolution spectral domain OCT and Scheimpflug photography provide unprecedented detail and resolution, enabling optical biopsy and improving the understanding of corneal pathology. Further studies are necessary to compare and analyze the tomographic reconstructions of the cornea with the different wavelengths, which may provide helpful information for diagnosing and managing corneal diseases.

Smart decision support system for keratoconus severity staging using corneal curvature and thinnest pachymetry indices

BackgroundThis study proposes a decision support system created in collaboration with machine learning experts and ophthalmologists for detecting keratoconus (KC) severity. The system employs an ensemble machine model and minimal corneal measurements.MethodsA clinical dataset is initially obtained from Pentacam corneal tomography imaging devices, which undergoes pre-processing and addresses imbalanced sampling through the application of an oversampling technique for minority classes. Subsequently, a combination of statistical methods, visual analysis, and expert input is employed to identify Pentacam indices most correlated with severity class labels. These selected features are then utilized to develop and validate three distinct machine learning models. The model exhibiting the most effective classification performance is integrated into a real-world web-based application and deployed on a web application server. This deployment facilitates evaluation of the proposed system, incorporating new data and considering relevant human factors related to the user experience.ResultsThe performance of the developed system is experimentally evaluated, and the results revealed an overall accuracy of 98.62%, precision of 98.70%, recall of 98.62%, F1-score of 98.66%, and F2-score of 98.64%. The application's deployment also demonstrated precise and smooth end-to-end functionality.ConclusionThe developed decision support system establishes a robust basis for subsequent assessment by ophthalmologists before potential deployment as a screening tool for keratoconus severity detection in a clinical setting.

Evaluation of Different Corneal Powers Measured by Corneal Tomography in Intraocular Lens Power Calculation

Abstract Background Corneal power measurement is essential for IOL power calculation. Conventional keratometry measures the anterior corneal surface using a standard keratometric index without measuring the posterior corneal surface. Schiempflug imaging have added the ability to measure posterior corneal surface which may affect IOL power calculation and postoperative refraction. Purpose To evaluate different keratometric measurements including Simulated keratometry (SimK), true net power (TNP), total corneal refractive power (TCRP) and equivalent K reading (EKR) obtained from corneal tomography in IOL power calculation and compare the predicted refraction of calculated IOL power with postoperative subjective refraction. Materials and Methods Sixty-five cataractous eyes were included in this prospective interventional case series. Four corneal power measurements using Pentacam AXL were analyzed: SimK over 3mm, TNP over 4mm, TCRP over 3mm and EKR over 4.5mm. The IOL power was calculated using Barrett Universal II formula. Results No statistically significant difference between SimK and EKR (p- value=1.000) while TNP and TCRP were statistically significantly higher than SimK (p-value&amp;lt;0.001) with mean difference 1.2+/-0.2D and 0.67+/-0.34D respectively. The mean prediction error of refractive outcome was -0.006+/-0.32D for SimK, -0.02+/- 0.5D for EKR, 1.08+/-0.4D for TNP and 0.56+/-0.46D for TCRP. Conclusion Corneal power measurements using SimK and EKR displayed comparable accuracy in IOL power calculation and postoperative refraction while TNP and TCRP were far away.

Early elastic and viscoelastic corneal biomechanical changes after photorefractive keratectomy and small incision lenticule extraction.

To compare early changes in the corneal biomechanical parameters after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) and their correlations with corneal shape parameters. One hundred twenty four eyes received myopic PRK and SMILE for similar amounts of myopia. Corneal tomography with Pentacam HR, biomechanical parameters using Corvis ST, and Ocular Response Analyzer (ORA) were evaluated before and 2weeks after surgery. The change in each parameter was compared between groups, while the difference in central corneal thickness and cornea-compensated intraocular pressure measured before and after surgery were considered as covariates. A significant reduction was seen in the corneal stiffness parameter at first applanation, and an increase in deformation amplitude ratio (DAR), and integrated inverse radius (IIR) in both groups after surgery (p < 0.001) Changes in DAR, and IIR were significantly greater in the SMILE than in the PRK group (p < 0.001) Corneal hysteresis (CH) and corneal resistance factor(CRF) decreased in both SMILE and PRK groups after surgery, (p < 0.001) with no statistically significant difference between groups (p > 0.05) Among new Corvis ST parameters, DAR showed a significant correlation with changes in Ambrosio relational thickness in both groups (p < 0.05). Both techniques caused significant changes in corneal biomechanics in the early postoperative period, with greater elastic changes in the SMILE group compared to the PRK group, likely due to lower tension in the SMILE cap and thinner residual stromal bed in SMILE. There were no differences in viscoelastic changes between them, so the lower CH may reflect the volume of tissue removed.

Three-Month Comprehensive Outcomes of Topography-Guided LASIK Versus Keratorefractive Lenticule Extraction (KLEx): A Prospective Contralateral Study.

The aim of this study was to compare outcomes of topography-guided laser-assisted in situ keratomileusis (TG-LASIK) and small incision lenticule extraction (SMILE®) for correcting myopia and myopic astigmatism. In this prospective, randomized contralateral study, 34 patients (68 eyes) received TG-LASIK in one eye, and SMILE in their fellow eye. Efficacy, safety, predictability, higher-order aberrations, corneal tomography, biomechanics, and patient-reported outcomes (PROs) were assessed preoperatively and up to 3months postoperatively. Both platforms showed comparable efficacy at 3months (TG-LASIK 1.08 ± 0.19; SMILE 0.98 ± 0.17, p = 0.055). However, TG-LASIK demonstrated quicker visual recovery, with 63% and 89% achieving uncorrected distance visual acuity (UDVA) of 20/16 or better at 1day and 1week, respectively, compared to SMILE (34% and 63%; p < 0.05). Safety index at 3months did not significantly differ between TG-LASIK and SMILE (p = 0.223). TG-LASIK and SMILE had 44% and 56% of eyes within 0.13D of spherical equivalent (SEQ) target, respectively. SMILE induced more total higher-order aberrations (HOAs), vertical coma, and oblique trefoil than TG-LASIK at 3months (p < 0.05). Both platforms showed similar increases in epithelial remodeling, but SMILE induced thicker epithelium than TG-LASIK at the 7.0-mm nasal zonal area. No significant differences were found in corneal hysteresis (CH) or corneal resistance factor (CRF) at 3months (p > 0.05). Reported symptoms of glare, halos, rings, starbursts, or dry eye did not significantly differ between groups at 3months (p > 0.05). Overall, 59% of patients preferred their TG-LASIK treated eye at 1month, but 65% of patients had no specific eye preference at 3months. TG-LASIK and SMILE demonstrate excellent and comparable efficacy, safety, and predictability at 3months, but TG-LASIK offers faster postoperative visual recovery at 1day and 1week. TG-LASIK induces fewer HOAs than SMILE, but both procedures affect corneal biomechanics similarly. ClincialTrials.gov identifier, NCT05611294.