title: Structural grading of foveal hypoplasia using spectral-domain optical coherence tomography a predictor of visual acuity?
abstract: OBJECTIVE
  To characterize and grade the spectrum of foveal hypoplasia based on different stages of arrested development of the fovea. Grading was performed using morphologic findings obtained by ultra high-resolution spectral-domain optical coherence tomography. Best-corrected visual acuity (BCVA) was calculated for different grades.
  
  
  METHODS
  Observational case series.
  
  
  METHODS
  Sixty-nine patients with foveal hypoplasia (albinism, n = 34; PAX6 mutations, n = 10; isolated cases, n = 14; achromatopsia, n = 11) and 65 control subjects were examined.
  
  
  METHODS
  A 7×7-mm retinal area was sampled using a 3-dimensional scanning protocol (743×75, A scans×B scans) with ultra high-resolution spectral-domain optical coherence tomography (SOCT Copernicus HR; 3-μm axial resolution). Gross morphologic abnormalities were documented. B-scans at the fovea were segmented using a longitudinal reflectivity profile. Logarithm of the minimum angle of resolution BCVA was obtained.
  
  
  METHODS
  Grading was based on presence or absence of foveal pit and widening of the outer nuclear layer (ONL) and outer segment (OS) at the fovea. Quantitative measurements were obtained for comparing atypical foveal hypoplasia in achromatopsia. Best-corrected visual acuity was compared with the grade of foveal hypoplasia.
  
  
  RESULTS
  Four grades of foveal hypoplasia were distinguished: grade 1, shallow foveal pit, presence of ONL widening, presence of OS lengthening; grade 2, grade 1 but absence of foveal pit; grade 3, grade 2 but absence of OS lengthening; grade 4, grade 3 but absence of ONL widening. There was significant difference in visual acuity (VA) associated with each grade (P<0.0001). Grade 1 was associated with the best VA (median VA, 0.2), whereas grades 2, 3, and 4 were associated with progressively poorer VA with a median VA of 0.44, 0.60, and 0.78, respectively. The atypical features seen with foveal hypoplasia associated with achromatopsia were characterized by decreased retinal and ONL thickness and deeper foveal depth.
  
  
  CONCLUSIONS
  A structural grading system for foveal hypoplasia was developed based on the stage at which foveal development was arrested, which helps to provide a prognostic indicator for VA and is applicable in a range of disorders associated with foveal hypoplasia. Atypical foveal hypoplasia in achromatopsia shows different characteristics.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Ophthalmology Group, School of Medicine, University of Leicester, Leicester, UK.
authors.forename: Mervyn G
authors.initials: MG
authors.lastname: Thomas
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.forename: Sarim
authors.initials: S
authors.lastname: Mohammad
authors.forename: Frank A
authors.initials: FA
authors.lastname: Proudlock
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Engle
authors.forename: Caroline
authors.initials: C
authors.lastname: Andrews
authors.forename: Wai-Man
authors.initials: WM
authors.lastname: Chan
authors.forename: Shery
authors.initials: S
authors.lastname: Thomas
authors.forename: Irene
authors.initials: I
authors.lastname: Gottlob
mesh_terms: D000293:Adolescent; D000328:Adult; D016115:Albinism, Oculocutaneous / Q000145:classification* / Q000175:diagnosis / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003117:Color Vision Defects / Q000145:classification* / Q000175:diagnosis / Q000503:physiopathology; D005124:Eye Abnormalities / Q000145:classification* / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D005584:Fovea Centralis / Q000002:abnormalities*; D006801:Humans; D007499:Iris Diseases / Q000145:classification* / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D041623:Tomography, Optical Coherence; D014786:Vision Disorders / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology*