Revised Calculation of the Prevalence of Keratoconus Based on Updated Scheimpflug Corneal Tomography Metrics in a Pediatric Population From a Chicago-Based School Age Vision Clinic

Eye & Contact Lens Science & Clinical Practice · 2026-01-05

To the Editor: We report an important update to the paper, Harthan JS, Gelles JD, Block SS, et al., Prevalence of Keratoconus Based on Scheimpflug Corneal Tomography Metrics in a Pediatric Population From a Chicago-Based School Age Vision Clinic. Published in Eye and Contact Lens in 2024.1 The original paper studied school age children ages 3 to 18 years and is significant in that the diagnosis of keratoconus was made using modern tomographic parameters and stressed the importance of early diagnosis. Earlier papers on the prevalence of disease commonly used anterior surface topography, which while specific, lacks sensitivity as it identifies disease in the later stages when anterior surface changes occur. This often underestimates the prevalence and does not allow identification of early or subclinical disease where intervention (e.g., corneal crosslinking) can prevent vision loss. The paper initially reported a prevalence of 1:334 for keratoconus and a prevalence of 1:223 when keratoconus suspects were included. Tomographic criteria for keratoconus included a final “D” from the Belin/Ambrósio display (Pentacam, OCULUS GmbH, Wetzlar, Germany) ≥3.02 and a posterior elevation at the corneal thinnest point ≥18 μm for myopic individuals and ≥28 μm for hyperopic patients. Prevalence rates were reported by subject if one or both eyes met criteria. The same analysis was used in the revised tabulation. The Belin/Ambrósio display was initially developed to screen patients for refractive surgery, and the final “D” represents variance from normal, but, in itself, is not specific for ectatic disease (e.g., corneal edema will result in an elevated final “D”). Typically, additional tomographic parameters, in addition to the final “D,” are included to improve specificity for keratoconus. These additional parameters may include an abnormal pachymetric progression and/or posterior elevation at the thinnest point (as in this study). Most of the confounding conditions, such as endothelial dysfunction, occur in adults and confounding conditions in children (e.g., congenital hereditary endothelial dystrophy) would be readily apparent. The goal of adding additional parameters is to improve specificity but should not be so restrictive as to decrease sensitivity. The values for the posterior elevation at the thinnest point chosen by the authors represent values 3.0 SD from the norm, which when added to the final “D” ≥3.0 become overly restrictive.3 In collaboration with the original authors and after the original publication, it was agreed that the results should be retabulated using the same final “D” (≥3.0), but with values for the posterior elevation at the thinnest point of 13 and 23 μm (myopic/hyperopic) roughly corresponding to 2 SD.4,5 This change should not significantly alter the overall specificity but should decrease false negatives. Prior studies showed that a final “D” ≥2.69 had a 100% specificity for keratoconus in an adult population when other known pathologies were excluded. How this compares to a pediatric population is not known as most studies dealt with a refractive surgery population.4 The revised parameters defined keratoconus as a final “D” ≥3.0 with a posterior elevation at the thinnest point ≥13/23 μm for myopic and hyperopic eyes, respectively. Suspect included eyes with a final “D” ≥2.0 but <3.0 with the same posterior elevation parameters. Normal eyes had a final “D” <2.0. With these adjusted parameters, the revised prevalence of keratoconus in the study population of 2007 individuals is 1:251 (an increase from six to eight classified as keratoconus), the prevalence of keratoconus suspect is 1:100 (an increase from 3 to 20), and the prevalence when combining keratoconus and keratoconus suspects is 1:72 (an increase from 9 to 28). Keratoconus is a visually disabling disorder that if left untreated or if treated late can lead to permanent, life-long debility. Using modern corneal imaging, the old historical teaching of keratoconus as a rare disease no longer applies. Early diagnosis is paramount if one wishes to intervene before significant visual loss. Since keratoconus typically first becomes evident in the pediatric age group knowledge of the disease, its diagnosis and treatment options need to be known not only by ophthalmologist and optometrists but by pediatricians, family practitioners, and school health screeners. The paper cited above, along with the even higher prevalence rates presented here, stresses the importance of keratoconus screening using modern diagnostic modalities. In addition to the use of Scheimpflug corneal tomography, advances in optical coherence tomography and biomechanical assessment may further enhance sensitivity and specificity in the detection of keratoconus and keratoconus suspects. We hope to increase awareness of the prevalence of the disease along with the goal of identifying disease early to limit future vision loss.

Patient Perspectives on Keratoconus Treatment: A Subjective Sentiment Analysis From Reddit

Eye & Contact Lens Science & Clinical Practice · 2025-04-24 · 1 citations

OBJECTIVE: Patient sentiments of keratoconus treatment discussions on Reddit were evaluated to enhance understanding of factors affecting the subjective patient experience. METHODS: Posts were extracted from the r/keratoconus on Reddit, an anonymous social media platform. The top 200 posts from each Reddit flair were included: "contact lenses," "crosslinking," "corneal transplant," and "corneal implants," and "other laser procedures." Posts were stratified by author and topic, and Valence Aware Dictionary and Sentiment Reasoner was used to generate a compound postsentiment score. Word frequency analysis was also conducted. RESULTS: Of the 717 posts analyzed, most were classified as positive (60.5%). "Other Laser Procedures" posts had the highest mean score, whereas "Corneal Implant" posts had the lowest (0.47 vs 0.06; P =0.045). Lifestyle and Preoperative question posts were most positive, whereas Noncompliance and Treatment Anxieties/Validation seeking posts were the most negative (0.41 vs 0.066; P =0.02). Word frequency analysis found high use of "pain" (n=230), "insurance" (n=34), and "years" (n=35). CONCLUSIONS: Subjective patient sentiment toward keratoconus treatment was overall positive. However, there was frequent discussion of timeline, pain, and contact lens instructions. These data suggest that addressing specific concerns, such as pain management and treatment anxieties, may improve satisfaction in keratoconus care.

Prevalence of Keratoconus Based on Scheimpflug Corneal Tomography Metrics in a Pediatric Population From a Chicago-Based School Age Vision Clinic

Eye & Contact Lens Science & Clinical Practice · 2024-02-07 · 13 citations

PURPOSE: Determine the pediatric prevalence of keratoconus (KC) using Scheimpflug corneal tomography. METHODS: A prospective observational study was done on subjects aged 3 to 18 years at the Princeton Vision Clinic, Chicago, IL. Scheimpflug tomography (Pentacam HR, OCULUS Optikgerate GmbH) scans (Belin/Ambrósio Enhanced Ectasia BAD3) yielded BAD Final D (Final D) and Back Elevation at the Thinnest Point (BETP) measurements. Criteria differentiating non-KC from KC suspects & KC were, Non-KC -Final D <2.00 in both eyes; KC suspect -Final D ≥2.00 and <3.00 in combination with BETP ≥18 μm for myopia and ≥28 μm for hyperopia/mixed astigmatism in at least one eye; and KC -Final D of ≥3.00 with BETP ≥18 μm for myopia or ≥28 μm for hyperopia/mixed astigmatism in at least one eye. Two thousand two hundred and six subjects were recorded, removing duplicate and poor-quality scans leaving 2007 subjects. RESULTS: Of 2007 subjects, six were classified as KC -prevalence of 1:334, three subjects were KC suspects -prevalence of 1:669, and total prevalence of KC suspects and KC was 1:223. CONCLUSION: The prevalence of KC in children is higher than previously reported, emphasizing the importance of sensitive screening for KC at its earliest manifestation as standard in pediatric comprehensive eye examinations.

The Pathophysiology of Keratoconus

Cornea · 2024-05-30 · 22 citations

PURPOSE: Keratoconus is a progressive disease characterized by changes in corneal shape, resulting in loss of visual function. There remains a lack of comprehensive understanding regarding its underlying pathophysiology. This review aims to bridge this gap by exploring structural failures and inflammatory processes involved in the etiology and progression of keratoconus. METHODS: A literature review was conducted using PubMed and Google Scholar databases, screening for articles published in English using the keyword combinations of "keratoconus" with "pathophysiology," "pathology," "metabolism," "inflammatory," "oxidative stress," "cytokines," "enzymes," "collagen," and "cornea." Articles published between January 1, 1970, and June 1, 2023, were queried and reviewed, with greater emphasis placed on more recent data. Fifty-six relevant studies were examined to develop a thorough review of the pathophysiological mechanisms at play in keratoconus. RESULTS: Biomechanical structural failures in the cornea seem to be the primary militating factors in keratoconus etiology and progression. These include disruptions in the arrangement in the collagen lamellae, a decrease in collagen levels, a decrease in natural collagen crosslinking, and changes in lysosomal enzyme activity. Immunologic changes have also been identified in keratoconus, challenging the traditional view of the condition as noninflammatory. Elevated levels of proinflammatory cytokines like IL-1b, IL-6, IL-17, and TNF-α have been observed, along with increased apoptosis of keratocytes. Increased oxidative stress leads to the activation of collagenase and gelatinase enzymes. CONCLUSIONS: Keratoconus is a complex condition influenced by both structural defects and inflammatory processes. Understanding these mechanisms can inform clinical management and potentially lead to more effective treatments.

Update on corneal crosslinking for keratoconus and corneal ectasia

Current Opinion in Ophthalmology · 2024-04-30 · 8 citations

PURPOSE OF REVIEW: To review corneal crosslinking for keratoconus and corneal ectasia, and recent developments in the field. This study will review the mechanism of crosslinking, clinical approaches, current results, and potential future innovations. RECENT FINDINGS: Corneal crosslinking for keratoconus was first approved by U.S. FDA in 2016. Recent studies have confirmed the general long-term efficacy of the procedure in decreasing progression of keratoconus and corneal ectasia. New types of crosslinking protocols, such as transepithelial treatments, are under investigation. In addition, adjunctive procedures have been developed to improve corneal contour and visual function in these patients. SUMMARY: Crosslinking has been found to be well tolerated and effective with the goal of decreasing progression of ectatic corneal diseases, keratoconus and corneal ectasia after refractive surgery. Studies have shown its long-term efficacy. New techniques of crosslinking and adjunctive procedures may further improve treatments and results.

Visual Improvement With Wavefront-Guided Scleral Lenses for Irregular Corneal Astigmatism

Eye & Contact Lens Science & Clinical Practice · 2024-12-10 · 10 citations

PURPOSE: To report interim results of a single center, randomized, double-blind, crossover-controlled clinical trial comparing wavefront-guided (wfg) scleral lenses (SLs) to traditional scleral lenses (tSLs) for patients with a history of irregular corneal astigmatism (ICA). METHODS: Thirty-one ICA eyes of 18 participants were reviewed, 23 with keratoconus, six postcorneal refractive ectasia, and two postpenetrating keratoplasty. Patients with corneal or lens opacities were not excluded from participating. Participants underwent a diagnostic lens-based fitting with a tSL with standard spherocylindrical optics. Once the tSL was finalized, a comprehensive wavefront aberrometer-based system was used to capture the residual aberration of the tSL under scotopic conditions without pharmacologic dilation, and these data were used to create a wfgSL. Once the tSL and wgfSL were finalized, a double-blinded, randomized, crossover was conducted where the participants received lens A (tSL or wgfSL) or lens B (the alternative), each worn for a 4±1 week interval. Measurements of the visual acuity (VA) and total higher-order root mean squared (HORMS) were recorded at each interval under controlled lighting conditions. At the final visit, patient subjective preference for lens A or lens B was recorded. RESULTS: The average HORMS for a fixed 5-mm pupil was 0.68±0.31 μm for tSL and 0.29±0.18 μm for wfgSL. Wavefront-guided SL provided an average HORMS improvement of 56% ( P <0.001). All eyes showed a reduction in HORMS, ranging from 18% to 83%. Wavefront-guided SL provided an average VA improvement of 0.12±0.11 logMAR ( P <0.01). Seventy-one percent of eyes showed one line or greater improvement, 26% showed no improvement, and 3% showed a reduction of VA with the wfgSL. The average VA with tSL was 0.14±0.16 logMAR and 0.03±0.11 logMAR for wfgSL. Seventeen of 18 patients subjectively preferred wfgSL. CONCLUSION: In eyes with ICA, wfgSL reduced HORMS and improved VA when compared with tSL. Patients subjectively preferred wfgSL to tSL. These interim results demonstrate the feasibility and generalizability of wfgSL in a typical clinical practice environment.

Long-Term Outcomes After Corneal Cross-linking for Progressive Keratoconus and Corneal Ectasia: A 10-Year Follow-Up of the Pivotal Study

Eye & Contact Lens Science & Clinical Practice · 2023-08-08 · 13 citations

OBJECTIVES: To report on the topographic and visual outcomes 10 years after corneal cross-linking in patients with progressive keratoconus and corneal ectasia after refractive surgery. METHODS: Cross-sectional cohort study of an original, prospective, randomized, clinical trial. Patients treated in a single center cornea and refractive surgery practice as part of the U.S. pivotal trials, which led to the Food and Drug Administration approval of corneal cross-linking, were recruited for a 10-year follow-up examination. LogMar lines (LL) of uncorrected visual acuity (UCVA) and best spectacle--corrected visual acuity (BSCVA), maximum keratometry, and thinnest pachymetry were evaluated. In addition, the Belin ABCD progression display was used to determine progression (95% confidence interval) of the anterior curvature, posterior curvature, and corneal thickness of each individual eye included. RESULTS: Nineteen eyes of 13 patients treated with standard cross-linking returned for a 10-year follow-up examination. Mean maximum keratometry changed from 58.2±12.0 diopters (D) to 58.3±10.1 D, thinnest pachymetry changed from 440.6±51.6 µm to 442.3±54.4 μm, UCVA changed from 0.79±0.42 LL to 0.86±0.46 LL, and BSCVA changed from 0.38±0.26 LL to 0.33±0.34 LL, 10 years after cross-linking. Individually, 68.5% of the entire cohort, 81.8% of keratoconus eyes, and 50% of eyes with corneal ectasia remained topographically stable 10 years after standard cross-linking. CONCLUSIONS: In the entire cohort, visual acuity and topography remained stable 10 years after cross-linking. Over the long-term, eyes with keratoconus seem to be more stable than those with corneal ectasia.

Correlation of Manifest Refraction and Simulated Keratometry to Tomography Characteristics in Patients With Keratoconus

Eye & Contact Lens Science & Clinical Practice · 2023-08-28 · 1 citations

OBJECTIVES: To report on baseline refractive and keratometric values and their correlation with tomographic characteristics of eyes with keratoconus (KC). METHODS: Retrospective chart review of patients treated in a single-center cornea and refractive surgery practice. Baseline topographic measurements were reviewed for 1,012 keratoconic eyes of 586 patients between 2008 and 2018. The manifest refraction, thinnest pachymetry (P thin ), corneal astigmatism (K astig ), and the maximum (K max ), steep (K steep ), flat (K flat ), and mean (K mean ) keratometry were analyzed. The location of K max (x, y) was used to determine central (<1 mm), paracentral (1-3 mm), pericentral (3-5 mm), or peripheral (>5 mm) cone locations. RESULTS: In the entire cohort, the mean manifest sphere was -2.2±4.4 diopters (D) and the cylinder was -3.2±2.3 D. In total, 48.6% of patients had against the rule (ATR) manifest astigmatism (M astig ). The average K astig was 3.8±2.7 D, and unlike the manifest axis, 50.2% of patients had with the rule (WTR) K astig . Patients with a K max less than 50 D had an M astig of -1.9±1.6 D, 45.9% of which was ATR M astig . With respect to baseline tomography measurements, K max , K steep , K flat , and K mean were 58.0±9.4, 50.6±6.5, 46.8±5.9, and 48.6±6.1 D, respectively. There was a weak correlation between K max and simulated keratometry (K steep , K flat , and K mean ) for patients with a K max less than 60 D. CONCLUSIONS: Simulated keratometry is poorly correlated with KC severity until the disease is more severe. M astig ≥2 D and ATR M astig were correlated with KC at all levels of severity. M astig ≥2 D and ATR M astig may serve as a simple, inexpensive, and widely available indicator for topographic analysis to identify possible KC and suggest further workup; however, further prospective studies are needed to confirm its utility.

Topography-Guided Photorefractive Keratectomy After Intacs Corneal Implantation for Keratoconus and Ectasia

Journal of Refractive Surgery Case Reports · 2023-04-01

Purpose: To evaluate outcomes of topography-guided photorefractive keratectomy (TG-PRK) after Intacs (Addition Technology) implantation for eyes with keratoconus or ectasia. Methods: Three eyes of 3 patients with keratoconus or ectasia after laser in situ keratomileusis were treated with TG-PRK 6 months after simultaneous Intacs implantation and standard corneal cross-linking (CXL) was performed. Results: After Intacs implantation/CXL, uncorrected distance visual acuity improved four lines in 1 eye and did not change significantly in the other eyes. At 1 year of follow-up after TG-PRK, uncorrected distance visual acuity further improved more than two lines in all eyes. After Intacs implantation/CXL, corrected distance visual acuity did not change significantly in all eyes. One year after TG-PRK, corrected distance visual acuity improved more than two lines in all eyes. After both procedures, the inferior-superior value decreased and maximum keratometry flattened significantly in all eyes. The change in thinnest pachymetry was less than 32 µm. Conclusions: TG-PRK appears promising as a treatment modality to improve visual acuity and corneal topography in patients with keratoconus and ectasia with prior Intacs placement who may have previously required segment explantation after poor refractive outcomes. [ Journal of Refractive Surgery Case Reports. 2023;3(2):e10–e13.]

Less Complex Contact Lens Required for a Patient With Keratoconus After Topography-Guided Photorefractive Keratectomy

Eye & Contact Lens Science & Clinical Practice · 2023-08-25

ABSTRACT: In this report, we discuss contact lens (CL) fitting in a patient with a history of keratoconus (KC), before and after undergoing topography-guided photorefractive keratectomy (TG PRK). Before TG PRK, the patient failed multiple CL modalities and reported difficulty with his habitual CLs and inadequate spectacle-corrected visual acuity to perform his activities of daily living. In this case, a collaborative, comprehensive approach to visual management in a patient with KC was used, and after TG PRK was performed to improve his corneal contour and symmetry, our patient was fit with a standard soft CL and additionally had improved spectacle-corrected visual acuity.