The Characteristics of Backscattering With Depth in the Progression of Keratoconus

Study Overview
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Brief Summary
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To investigate the variation in backscattering with depth between forme fruste keratoconus (FFKC), keratoconus, and normal eyes; to determine the backscattering changes in the characteristics of keratoconus progression; and to explore the diagnostic value of backscattering in FFKC.

Detailed Description
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To investigate the variation in backscattering with depth between forme fruste keratoconus (FFKC), keratoconus, and normal eyes; to determine the backscattering changes in the characteristics of keratoconus progression; and to explore the diagnostic value of backscattering in FFKC. A Scheimpflug corneal tomography image and caliper tool were used to obtain backscatter at every 2% depth at the thinnest point of the cornea, with the measured values expressed in grayscale units (GSU).

Official Title
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The Characteristics of Backscattering With Depth in the Progression of Keratoconus and Its Role in Forme Fruste Keratoconus Detection

Conditions
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Elasticum, Incomplete Pseudoxanthoma

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BCVA <20/20 and a history of myopia or astigmatism; presence of any of the following positive signs on slit lamp examination: corneal stromal thinning, cone-shaped anterior protrusions, Fleischer's ring, Vogt's striae, epithelial or subepithelial scarring; abnormal corneal topography (maximum keratometry (K) value of >47.2 diopters (D), bow-tie pattern with skewed radial axes, or inferior-superior asymmetry(3-mm I-S keratometric difference >1.4 D). Exclusion Criteria: 1. Patients with severe corneal scarring that affected light scattering and density maps showing black holes 2.Participatients with other corneal diseases 3. Eyes that have undergone surgery or trauma 4. Eyes with corneal dystrophy -
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| forme fruste keratoconus<br>1) no other eye abnormalities except myopia and astigmatism; 2) transparent cornea; 3) no positive signs of keratoconus on slit lamp examination or morphology examination (excluding the appearance of keratoconus as described above, and simultaneously satisfying A0B0C0D0, Index of Surface variance (ISV) < 30, and Keratoconus Index (KI) < 1.07); and 4) Belin/Ambrósio enhanced ectasia total derivation value(BAD-D)≤1.6 | |
| Clinical keratoconus<br>46.5 D ≤ Mean K <52 D; 55≤ ISV<200; and 1.10 ≤ KI <1.50 | |
| severe keratoconus<br>Mean K ≥ 52D; ISV≥ 200; and KI≥ 1.50 | |
| normal eye<br>one eye of healthy participants before refractive surgery were randomly selected. Comprehensive ophthalmic examinations were performed before surgery, which confirmed that the cornea was clear and normal in shape. For this group, there was no family history of keratoconus, no other diseases except ametropia, and no corneal dilatation one year after surgery. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| backscattering | Standard measurements were performed using a Pentacam (Pentacam HR; Oculus, Wetzlar, Germany);The average brightness of a predetermined area of the cornea was calculated, shown as densitometry, and recorded in GSU ranging from 0 to 100 (0, cornea is transparent without opacity; 100, cornea is completely opaque). | through study completion, an average of 1 year |