Elsevier

Ophthalmology

Volume 118, Issue 8, August 2011, Pages 1653-1660
Ophthalmology

Original article
Structural Grading of Foveal Hypoplasia Using Spectral-Domain Optical Coherence Tomography: A Predictor of Visual Acuity?

https://doi.org/10.1016/j.ophtha.2011.01.028Get rights and content

Purpose

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.

Design

Observational case series.

Participants and Controls

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.

Main Outcome Measures

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.

Financial Disclosure(s)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Section snippets

Patients

The study population consisted of 69 patients with foveal hypoplasia (defined as incursion or continuation of inner retinal layers) and 65 controls with a mean age of 28.5 years (standard deviation, 15.7 years; range, 5–64 years) and 33.5 years (standard deviation, 14.3 years; range, 8–62 years), respectively. The patient cohort consisted of 58 white persons (84%) and 11 Asians (16%); similarly, the control cohort consisted of 48 white persons (74%) and 17 Asians (26%). In the patient group,

Gross Morphologic Features Associated with Foveal Hypoplasia

Examples of the gross features of foveal hypoplasia detectable on ultra high-resolution spectral-domain OCT are shown in Figure 2. The hallmark of foveal hypoplasia detectable on OCT is the incursion of the inner retinal layers posterior to the foveola. In addition to this, other features seen on OCT included: shallower or absent foveal pit, diminished ONL widening, decreased OS lengthening, and overall thickening of the retina. However, there is considerable phenotypic variability associated

Discussion

This study proposed a structural grading system for foveal hypoplasia based on loss of unique elements that form the normal fovea that likely have been arrested during early development. The proposed grading system has 3 advantages: (1) it gives insight into the degree of development of the fovea, (2) it provides a prognostic indicator from a morphologic OCT scan, and (3) it can be applied to most disorders associated with foveal hypoplasia. The study also showed that achromatopsia can be

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    Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

    Supported by the National Eye Research Centre, Bristol Eye Hospital, Bristol, UK (grant nos.: RM61G0124 and RM61G0216); and Ulverscroft Foundation, Anstey, Leicester, UK.

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