Diagnosis of keratoconus in a young male after the hint of electrophysiological test: A Case Report and Review of the Literature

Background: Keratoconus (KCN) is a bilateral and usually asymmetrical disease in which the ectatic cornea becomes conical. Diagnosis of unimproved visual acuity (VA) as KCN might sometimes be missed out due to lack of consideration. However, combination of the electrophysiology test and other common ophthalmological examinations could help to locate the lesion for the unimproved VA and realize the possibility of the existence of KCN, which could be diagnosed via corneal topography. The purpose of this report is to describe the diagnosis process of a case of KCN after the hint of lesion location by electrophysiological tests. Case presentation: A 23-year-old young male presented to our ophthalmology clinic complaining of decreased visual acuity in the left eye for 5 months. Clinical evaluation showed best corrected visual acuity of 1.0 OD, and 0.06 OS. The dilated fundus examination revealed no specific abnormality. Spectral-domain optical coherence tomography (SD-OCT) of macular revealed no obvious change on macular and the thickness of peripapillary nerve fiber layer on both eyes. No leakage of fluorecein was found under Fluorescein angiogram (FFA) of both eyes. Indocyanine green angiography (ICGA) did not showed abnormality. The full-field electroretinogram (ffERG) revealed no obvious changes of amplitudes in all responses. Pattern visual evoked potentials (PVEP) detected a reduced amplitude and delayed phase in P100-wave in both eyes. The amplitude and latency of P2-wave in Flash VEP (FVEP) were comparable in both eyes and were within normative ranges. Corneal topography was finally performed and KCN was diagnosed with the presence of asymmetrical bowtie pattern in both eyes, which was worse in the OS. Conclusions: The hint of lesion location by electrophysiological studies (ffERG, PVEP and FVEP) could be of favor to diagnose the conditions with unimproved VA, such as KCN. Consideration of KCN should be suspected in patients with unimproved VA and significant irregular stigmatism, while no obvious lesion exists in other parts of the eye.