Association between Corneal Stiffness Parameter at the First Applanation and Keratoconus Severity

Area of Science:

• Ophthalmology
• Biomechanical Engineering
• Corneal Science

Background:

• Keratoconus is a progressive thinning disorder of the cornea.
• Accurate diagnosis and severity assessment are crucial for effective management.
• Corneal biomechanics offer potential insights into keratoconus pathophysiology.

Purpose of the Study:

• To evaluate the corneal stiffness parameter at first applanation (SP-A1) in normal and keratoconus eyes.
• To explore the association between SP-A1 and indicators of keratoconus severity.

Main Methods:

• A comparative study included 351 normal and 351 keratoconus eyes.
• Keratoconus diagnosis based on topography and slit-lamp examination.
• Corneal severity classified as mild, moderate, or severe based on steep keratometry (Ks).
• SP-A1 measured using Corvis ST software; correlation and ROC analyses performed.

Main Results:

• SP-A1 values were significantly lower in keratoconus eyes (72.11 mmHg/mm) compared to normal eyes (110.89 mmHg/mm).
• SP-A1 decreased progressively with increasing keratoconus severity (mild: 79.54, moderate: 65.11, severe: 47.59 mmHg/mm).
• SP-A1 showed a negative correlation with Ks and a positive correlation with thinnest corneal thickness (TCT).
• SP-A1 demonstrated significant associations with intraocular pressure (IOP), biomechanical IOP (bIOP), and various air-puff response parameters.
• Receiver Operating Characteristic (ROC) analysis showed high accuracy for SP-A1 in detecting keratoconus (AUC=0.952) and mild keratoconus (AUC=0.930).

Conclusions:

• SP-A1 is a valuable indicator of corneal biomechanical properties in keratoconus.
• Lower SP-A1 values correlate with increased keratoconus severity.
• SP-A1 demonstrates potential as a diagnostic tool for identifying keratoconus in clinical practice.