Abstract:  Objective To study the clinical characteristics of patients with keratoconus who were misdiagnosed as optic neuropathy due to short-term vision loss. Design Retrospective case series. Participants 26 patients (33 eyes) were initially misdiagnosed as optic neuropathy, but finally diagnosed as keratoconus after relevant examinations from 2010 to 2020 in Beijing Tongren Eye Center. Methods The patients' medical records and auxiliary ophthalmic examination results, including corneal topography, visual evoked potentials (VEP), visual field and etc were reviewed. Main Outcome Measures Visual acuity, refraction, corneal curvature, ocular signs. Results Among all 26 cases, 20 patients were male (76.9%), and mean age was (27.8±8.2) years. 19 patients (73.1%) were affected unilaterally, and 7 patients (26.9%) were affected bilaterally. The corrected visual acuity was from 0.02 to 1.0 when diagnosed as neuropathy. The average sphere refraction of affected eyes was (-7.18 ± 3.63) D, cylinder refraction was (-2.09±1.86) D. The corneal curvature K1 and K2 was (52.83±3.89) D and (47.55±3.64) D respectively in affected eyes. Among 19 monocular patients, the sphere and cylinder refraction was (-6.51±2.99) D and (-2.27±1.60) D in affected eyes, significantly higher than the lateral eyes (-3.06±2.09) D and (-1.11±1.03) D (P<0.001 and P=0.048). The color fundus images of 28/33 eyes (84.8%) were slightly blurred. The corneal morphology with slit lamp microscopy was normal in 18/33 eyes (54.6%), and only 15/33 eyes (45.4%) were found slight corneal cone-like protrusion and mild stromal opacity. The relative afferent pupillary defect (RAPD) of all patients were negative. No abnormalities were observed in the posterior fundus, VEP and electroretinogram. Conclusion Keratoconus patients misdiagnosed as optic neuropathy due to decreased vision often have a short-term increased myopia and astigmatism, ignoring the signs of optic neuropathy. Corneal topography examination is beneficial to the diagnosis of keratoconus. （Ophthalmol CHN, 2022, 31: 94-98）

Key words:  keratoconus, optic neuropathy, misdiagnosis