title: Long-term follow-up of two patients with oligocone trichromacy.
abstract: BACKGROUND
  Oligocone trichromacy (OT) is an uncommon cone dysfunction disorder, the mechanism of which remains poorly understood. OT has been thought to be non-progressive, but its long-term visual outcome has been seldom reported in the literature. Our aim was to present two OT patients followed at our institution over 18 years.
  
  
  METHODS
  Complete ocular examination, color vision, visual fields, and full-field electroretinography (ERG) were performed at initial presentation and follow-up. Spectral-domain optical coherence tomography (OCT) was performed during follow-up when available at our institution.
  
  
  RESULTS
  Initial ocular examination showed satisfactory visual acuities with normal fundus examination and near-to-normal color vision. However, computerized perimetry demonstrated a ring-shaped scotoma around fixation, and ERG showed a profound cone dysfunction. The discrepancy between preserved color vision and profound cone dysfunction leads to the diagnosis of OT. Subsequent follow-ups over 18 years showed subtle degradation of visual acuities along with progression of the myopia in both patients and slight worsening of color vision in one patient. Initial OCT revealed a focal interruption of the ellipsoid line along with decreased thickness of the perifoveal macula. Subsequent OCT imaging performed 2 years later did not show any macular changes.
  
  
  CONCLUSIONS
  Although OT is known to be a non-progressive cone dysfunction, our results suggest that subtle degradation of the visual function might happen over time.
authors.affiliation: Exploration of Visual Function and Neuro-Ophthalmology Department, Lille University Hospital, Rue Emilie Laine, 59037, Lille Cedex, France. vasily.smirnov@univ-lille2.fr.
authors.forename: Vasily
authors.identifier: http://orcid.org/0000-0003-1629-4579
authors.initials: V
authors.lastname: Smirnov
authors.affiliation: Exploration of Visual Function and Neuro-Ophthalmology Department, Lille University Hospital, Rue Emilie Laine, 59037, Lille Cedex, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Drumare
authors.affiliation: Exploration of Visual Function and Neuro-Ophthalmology Department, Lille University Hospital, Rue Emilie Laine, 59037, Lille Cedex, France.
authors.forename: Ikram
authors.initials: I
authors.lastname: Bouacha
authors.affiliation: Exploration of Visual Function and Neuro-Ophthalmology Department, Lille University Hospital, Rue Emilie Laine, 59037, Lille Cedex, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Puech
authors.affiliation: Exploration of Visual Function and Neuro-Ophthalmology Department, Lille University Hospital, Rue Emilie Laine, 59037, Lille Cedex, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Defoort-Dhellemmes
mesh_terms: D000293:Adolescent; D002648:Child; D003117:Color Vision Defects / Q000175:diagnosis* / Q000503:physiopathology; D004596:Electroretinography; D005260:Female; D005451:Fluorescein Angiography; D005500:Follow-Up Studies; D006801:Humans; D010375:Pedigree; D017949:Retinal Cone Photoreceptor Cells / Q000473:pathology*; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods; D014792:Visual Acuity / Q000502:physiology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology
keywords: Achromatopsia; Bradyopsia; ERG; Electroretinography; OCT; Oligocone trichromacy