The Evolution of Diagnostics for Keratoconus: From Ophthalmometry to Biomechanics

Strategies for Early Keratoconus Diagnosis: A Narrative Review of Evaluating Affordable and Effective Detection Techniques

Keratoconus is a progressive corneal disorder that can lead to irreversible visual impairment if not detected early. Despite its high prevalence, early diagnosis is often delayed, especially in low-to-middle-income countries due to limited awareness and restricted access to advanced diagnostic tools such as corneal topography, tomography, optical coherence tomography, and corneal biomechanical assessments. These technologies are essential for identifying early-stage keratoconus, yet their high cost limits accessibility in resource-limited settings. While cost and portability are important for accessibility, the sensitivity and specificity of diagnostic tools must be considered as primary metrics to ensure accurate and effective detection of early keratoconus. This review examines both traditional and advanced diagnostic techniques, including the use of machine learning and artificial intelligence, to enhance early diagnosis. Artificial intelligence-based approaches show significant potential for transforming keratoconus diagnosis by improving the accuracy and sensitivity of early diagnosis, especially when combined with imaging devices. Notable innovations include tools such as SmartKC, a smartphone-based machine-learning application, mobile corneal topography through the null-screen test, and the Smartphone-based Keratograph, providing affordable and portable solutions. Additionally, contrast sensitivity testing demonstrates potential for keratoconus detection, although a precise platform for routine clinical use has yet to be established. The review emphasizes the need for increased awareness among clinicians, particularly in underserved regions, and advocates for the development of accessible, low-cost diagnostic tools. Further research is needed to validate the effectiveness of these emerging technologies in detecting early keratoconus.

Prevalence and demographic profile of keratoconus among high school students in Kenya

PURPOSE

To determine the prevalence and demographic profile of keratoconus (KC) among high school students in Nairobi County, Kenya.

METHODS

In this population-based, prospective, cross-sectional study, multistage cluster sampling was used to select the participants. All students underwent visual acuity measurement, auto-refraction, retinoscopy and corneal topography. Students with a scissors reflex on retinoscopy or corneal topography patterns suspicious of KC were referred for corneal tomography.

RESULTS

A total of 3051 students from 29 schools, with a mean age of 17.4 ± 1.6 years (range: 13-25 years) were screened. The prevalence of KC was 1.7% (n = 51) (95% CI, 1.2-2.2) and of KC suspects was 3.8% (n = 117) (95% CI, 3.2-4.6). There were no significant associations between the prevalence of KC and gender, age or ethnicity (all p > 0.05). In the KC group, 88.2% (n = 45) were unaware of their condition, 52.9% (n = 27) were treated for allergic conjunctivitis, 45.1% (n = 23) required spectacles, 11.8% (n = 6) were recommended contact lenses in at least one eye and 49.0% (n = 25) were recommended corneal cross-linking.

CONCLUSIONS

Among adolescents, the results of this study indicate a higher prevalence of KC compared to that reported in South Korea, Norway, Brazil and Caucasians in New Zealand, but less than that reported in some countries in the Middle East. Given the high prevalence revealed in this study, a national school screening program and clinical guidelines for screening, diagnosis and management of KC is recommended.

Effect of corneal diameter on preoperative screening results for corneal refractive surgery

AIMS

To investigate the impact of different corneal diameters on corneal morphology and biomechanical outcome during preoperative screening for corneal refractive surgery.

METHODS

A retrospective analysis was conducted on 300 patients who underwent corneal refractive surgery at Eye and ENT Hospital, Fudan University between October 2023 and December 2023. All patients had no history of keratoconus or previous corneal surgery. Patients were categorized into two groups based on corneal topography measurements: (1) normal corneal diameter group (n=159), those with corneal diameter ranging from 11.5 mm to 12.0 mm; (2) abnormal corneal diameter group (n=141), those with corneal diameter smaller than 10.0 mm or larger than 12.5 mm. Corneal thickness, morphologic data, and biomechanical data were measured using Pentacam corneal topography. Correlation analysis was conducted to explore the relationship between corneal diameter and various corneal topography and biomechanical data.

RESULTS

Significant differences were observed in corneal topography data including BFSf (F=43.21), BFSb (F=30.24), Df (F=15.32), Dp (F=32.36), Da (F=9.66), D (F=58.36), PPIavg (F=32.64), and ARTmax (F=12.06) between the groups (P<0.05). Additionally, BFSf, BFSb, Db, Dp, D, and PPIavg exhibited statistically significant differences between any two groups (P<0.05). Significant differences were also found in Df, Da, and ARTmax between small and large corneas, as well as between normal-sized and large corneas (P<0.05). Correlation analysis indicated negative correlations between corneal diameter and A1V (r=-0.12), HCdArcLength (r=-0.17), CBI (r=-0.27), bIOP (r=-0.13), Df (r=-0.025), PPIavg (r=-0.028), and TBI (r=-0.27). Conversely, BFSf (r=0.009), BFSb (r=0.001), PD (r=0.15), and ARTH (r=0.37) displayed positive correlations with corneal diameter.

CONCLUSIONS

Corneal diameter significantly affects preoperative screening for corneal refractive surgery. Smaller corneal diameters exhibit a greater influence on the corneal topography BAD analysis system.

Topographic Keratoconus Incidence in Greece Diagnosed in Routine Consecutive Cataract Procedures: A Consecutive Case Series of 1250 Cases over 5 Years

Background: Scheimpflug tomography has for many years been an integral part of our pre-operative assessment in cataract extraction. We retrospectively reviewed the incidence of topographic keratoconus and keratoconus suspicion in our routine cataract surgery population over 5 years. Setting: The Laservision Clinical and Research Institute, Athens, Greece. Methods: In 1250 consecutive cataract surgery cases in otherwise naïve eyes, accounting for years 2017 to 2021, we retrospectively evaluated preoperative Pentacam HR imaging. The cases already classified as keratoconus were included in group A. The residual cases were assessed by five different experienced evaluators (two ophthalmic surgeons and three optometrists) for topographic and tomographic keratoconus suspicion based on irregular pachymetry distribution, astigmatism truncation, and/or astigmatic imaging irregularity and included in group B. Regular corneas, by this assessment, were included in group C; irregular corneas, as determined by the evaluators but unrelated to keratoconus, were included in group D. Results: Based on the above, 138 cases (11.08%) were classified by Pentacam tomography as keratoconus and by default were included in group A. Of the residual cases, 314 or 25.12% were classified as suspect keratoconus and included in group B; 725 cases (58%) were classified as normal and non-keratoconus and included in group C; and 73 cases or 5.84% were placed in group D as non-keratoconus but abnormal. There was no disagreement between the five evaluators over any of the cases in groups C and D, and little variance among them for cases included in group B (less than 5% by ANOVA). Conclusions: The incidence of keratoconus and corneas suspicious for keratoconus in Greece appears to be much higher than respective reports from other regions: one in ten Greeks appear to have topographic keratoconus, most not diagnosed even by the age of cataract surgery, and almost an additional one in four may have suspicious corneal imaging for keratoconus. These data strongly imply that routine screening for disease should be promoted among Greeks, especially during puberty, to halt possible progression; moreover, careful screening should be performed when laser vision correction is being considered.

Prevalence of Keratoconus in the Young Eastern Population of Saudi Arabia

BACKGROUND

Keratoconus (KCN) is a progressive corneal ectasia that manifests at a young age and significantly impacts vision and quality of life. Early diagnosis allows for effective treatment with corneal collagen crosslinking, yet there is a lack of screening methods. This research aims to screen adolescents and young adults for this sight-threatening disease using quick corneal tomography mapping.

METHODS

This prospective cross-sectional study is being conducted at Johns Hopkins Aramco Healthcare in Saudi Arabia, focusing on subjects aged 13-23. We are presenting the data from our study as internal pilot study data. Bilateral corneal imaging with Pentacam HR (Oculus, Wetzlar, Germany), utilizing Scheimpflug corneal tomography, was performed. Historical data on allergies, eye rubbing, KCN, family history, previous eye surgery, and contact lens use were collected. The Belin Ambrosio Enhanced Ectasia Display total D value served as an objective criterion for suspect KCN (SKCN) diagnosis.

RESULTS

In this study with 110 participants, KCN was identified in 2.75% of participants and SKCN in 11.93%. Systemic allergies or eczema were reported by 2.80%, with no cases in the KCN or SKCN groups. Eye rubbing behavior was observed in 5.50%, with the highest prevalence (33.30%) in the KCN group. A family history of KCN was found in 21.10%, with SKCN having the highest prevalence (30.80%).

CONCLUSION

This restricted population study reveals a significant KCN rate of 2.75%. The condition, easily detected and treatable with corneal collagen crosslinking, highlights the need for larger population studies to determine the disease's true prevalence. Efficient screening programs tailored to regional data are essential for early detection and intervention.

Medmont Meridia™: Much More Than a Corneal Topographer

In recent years, advanced diagnostic instruments have become widely available in optometric practices, offering various functions that optimize clinical information gathering. This article focuses on the Medmont Meridia™, a state-of-the-art multipurpose diagnostic device with corneal topography and cutting-edge features. Corneal topography is pivotal in the early diagnosis of corneal disorders, determining baseline ocular surface assessment, helping in contact lens fitting, and monitoring ocular health over time. The Medmont Meridia boasts Placido-disc-based imaging with extensive corneal coverage. Furthermore, the Meridia accurately measures the horizontal visible iris diameter, pupil diameter, and palpebral fissure width, which assists in making contact lens parameter decisions. Additionally, it offers sagittal height data for scleral lens design and first lens selection, streamlining the fitting process. Beyond its topography capabilities, the Meridia excels as a comprehensive dry eye assessment tool. With features like tear meniscus height, tear film surface quality, and meibography capabilities, it aids in diagnosing dry eye and monitoring its progression. The device also provides customizable dry eye reports with integrated grading scales and questionnaires, making dry eye management, patient education, and compliance more accessible. In conclusion, the Medmont Meridia consolidates a multitude of examination tools in a single instrument, enhancing practice efficiency and elevating patient care and communication. Its versatility and accuracy make it an invaluable asset in optometric practices worldwide.

The impact of UV cross-linking on corneal stromal cell migration, differentiation and patterning

Previous studies have demonstrated that UV cross-linking (CXL) increases stromal stiffness and produces alterations in extracellular matrix (ECM) microstructure. In order to investigate how CXL impacts both keratocyte differentiation and patterning within the stroma, and fibroblast migration and myofibroblast differentiation on top of the stroma, we combined CXL with superficial phototherapeutic keratectomy (PTK) in a rabbit model. Twenty-six rabbits underwent a 6 mm diameter, 70 μm deep phototherapeutic keratectomy (PTK) with an excimer laser to remove the epithelium and anterior basement membrane. In 14 rabbits, standard CXL was performed in the same eye immediately after PTK. Contralateral eyes served as controls. In vivo confocal microscopy through focusing (CMTF) was used to analyze corneal epithelial and stromal thickness, as well as stromal keratocyte activation and corneal haze. CMTF scans were collected pre-operatively, and from 7 to 120 days after the procedure. A subset of rabbits was sacrificed at each time point, and corneas were fixed and labeled in situ for multiphoton fluorescence microscopy and second harmonic generation imaging. In vivo and in situ imaging demonstrated that haze after PTK was primarily derived from a layer of myofibroblasts that formed on top of the native stroma. Over time, this fibrotic layer was remodeled into more transparent stromal lamellae, and quiescent cells replaced myofibroblasts. Migrating cells within the native stroma underneath the photoablated area were elongated, co-aligned with collagen, and lacked stress fibers. In contrast, following PTK + CXL, haze was derived primarily from highly reflective necrotic "ghost cells" in the anterior stroma, and fibrosis on top of the photoablated stroma was not observed at any time point evaluated. Cells formed clusters as they migrated into the cross-linked stromal tissue and expressed stress fibers; some cells at the edge of the CXL area also expressed α-SM actin, suggesting myofibroblast transformation. Stromal thickness increased significantly between 21 and 90 days after PTK + CXL (P < 0.001) and was over 35 μm higher than baseline at Day 90 (P < 0.05). Overall, these data suggest that cross-linking inhibits interlamellar cell movement, and that these changes lead to a disruption of normal keratocyte patterning and increased activation during stromal repopulation. Interestingly, CXL also prevents PTK-induced fibrosis on top of the stroma, and results in long term increases in stromal thickness in the rabbit model.