Patients with keratoconus who underwent manifest refraction vs. autorefraction achieved significantly better corrected distance visual acuity with spectacles.
Researchers examined 90 eyes with keratoconus with both autorefraction using the KR8800 keratorefractometer (Topcon) and manifest refraction done by the same optometrist under identical dim room conditions using the CV3000 automatic phoropter (Topcon). Eyes were examined in random order, 43 with autorefraction first and 47 with manifest refraction first.
Mean spectacle-corrected distance visual acuity improved with both methods, but was better when manifest refraction vs. autorefraction: 20/23 vs. 20/38 Snellen; P < .0001), with a mean dioptric difference of 4.83 D. Differences were greater between manifest refraction and autorefraction results with cornea steepening, with Kmax being the only variable in the multivariable analysis to significantly affect results.
“[I]f Kmax was steeper, the dioptric difference was also steeper, meaning that the discrepancy between the two refraction methods increases with keratoconus severity,” the study authors said. – by Robert Linnehan
Disclosures: The researchers report no relevant financial disclosures.