Visante in Atypical Posterior Keratoconus

To report a case of posterior keratoconus with atypical ocular findings Case report : An 8-year-old boy was referred to our clinic with the chief complaint of blurred vision in his right eye. The patient had no history prior ocular surgery of trauma. Her family history was also unremarkable. Comprehensive ocular examination was performed. The patient's best spectacle corrected visual acuity (BSCVA) was 3/10 in the right eye and 8/10 in the left eye with refraction of +11.5-0.5×75 (OD) and +4-0.25×25 (OS). On slit-lamp examination of the right eye, normal anterior corneal surface with central posterior corneal depression, pigment deposition and diffuse stromal edema was noticed. Fundoscopic examination and intraocular pressure (IOP) measurements were normal in both eyes. Specular microscopy gave normal corneal endothelial cell count values. Axial topography revealed central flattening of the cornea that corresponded to the area of posterior keratoconus with peripheral steeping in the right eye and asymmetric bow-tie astigmatism in the left eye. Measurement of central corneal thickness with ultra-sound pachymetry showed corneal thickness in the right eye (OD=616 µm and OS=559 µm). Orbscan II demonstrated anterior and posterior Diff of 17 µm and 48 µm respectively, which were within normal limits. Simulated keratometry showed corneal flattening (OD and OS: 37×23 and 36.5×113, respectively). Also, Visante revealed normal anterior surface but the irregularity of posterior corneal surface was typically compatible with the diagnosis of posterior keratoconus. Atypical forms of posterior keratoconus can be presented with thick cornea and central corneal flattening. Although both Orbscan and Visante can reveal posterior corneal surface abnormalities, the latter is suggested for studying corneal architecture and excavation.