The relationship between air pressure and corneal deformation predicted the presence and severity of keratoconus with more sensitivity than keratometry and corneal pachymetry, a study found.
“These biomechanical metrics slightly improved the detection and severity prediction of keratoconus above traditional keratometric and pachymetric assessment of corneal shape,” the study authors said. “Future longitudinal studies with improved instrumentation to assess corneal anatomy, physiology, and biomechanics will be required to better understand the corneal changes that occur as keratoconus develops.”
The study included 70 eyes of 37 patients diagnosed with keratoconus who had an average age of 36 years. An age-matched control group comprised 70 healthy eyes of 37 patients.
Investigators used the Ocular Response Analyzer (Reichert) to measure the air pressure-corneal deformation relationship in all eyes.
The Orbscan II (Bausch + Lomb) was used to measure corneal topography and pachymetry. Keratoconus severity was graded based on anterior corneal curvatures, difference in astigmatism in each meridian, and anterior and posterior best-fit spheres.
Study results showed that most biomechanical properties of keratoconic eyes varied significantly from those of healthy eyes (P < .001). Thin cornea (P < .001), more rapid corneal concave deformation past applanation (P = .01) and lower tear film index (P = .01) correlated most significantly with increased keratoconus severity.
Corneal curvature and central corneal thickness, and biomechanical properties to a lesser extent, accounted for variations in keratoconus severity.
Corneal biomechanical data aided the detection of keratoconus with 15% higher sensitivity than keratometry alone and 5% more sensitivity than keratometry combined with pachymetry, the authors said.