The anterior corneal surface holds many answers for patients with keratoconus, but eye care providers should look more toward contrast sensitivity than acuity for a better determination of visual quality. A recent study reports that contrast sensitivity is more strongly correlated with corneal shape parameters than is acuity in keratoconus.
The cohort included 77 keratoconic eyes of 44 patients with various stages of the condition, tested to assess corneal elevation centrally and peripherally. The team found that contrast sensitivity and visual acuity displayed the strongest correlation with slope in the central part of the cornea (within a radius of 1mm). For contrast sensitivity, this finding held true for keratoconic eyes with peripheral or central apexes. However, central apexes did not demonstrate a statistically significant correlation between the shape of the cornea and visual acuity at any distance.
“The most important region that determines the visual quality is the region above the corneal center within a 1mm radius in the opposite direction of the keratoconus apex,” the study authors concluded in their paper.
Liduma S, Luguzis A, Krumina G. The impact of irregular corneal shape parameters on visual acuity and contrast sensitivity. BMC Ophthalmol. November 26, 2020. [Epub ahead of print].