A retinal pigment epithelium window defect is a specific fluorescein angiography finding, not a diagnosis in itself, and understanding exactly what it represents, missing or attenuated pigment simply allowing background choroidal fluorescence to shine through more visibly, is essential for correctly interpreting angiograms and avoiding confusion with the other, more clinically active causes of hyperfluorescence that this pattern must be distinguished from.
What a Window Defect Actually Represents
The retinal pigment epithelium normally contains melanin pigment that partially blocks and masks the fluorescence of dye within the underlying choroidal circulation during fluorescein angiography, and when this pigment epithelium becomes thinned, atrophic, or entirely absent, this normal masking effect is lost, allowing the underlying choroidal fluorescence to become more visible, a phenomenon termed a window defect.
The Key Distinguishing Angiographic Behavior
Window defects have a characteristic and diagnostically essential temporal pattern that separates them from other causes of hyperfluorescence: they appear early in the angiogram, corresponding to the timing of the underlying choroidal fluorescence itself, remain sharply demarcated with well-defined borders corresponding exactly to the area of pigment epithelial loss, and, critically, do not increase in size or intensity, and do not leak or pool, as the angiogram progresses through its later frames.
This lack of leakage or progressive change over the course of the angiogram is what distinguishes a window defect from other causes of hyperfluorescence, including active leakage from choroidal neovascularization or staining of an anatomic structure, both of which characteristically increase in size, intensity, or extent in later angiogram frames.
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From Choroida — the team behind this siteCauses of Window Defects
- Geographic atrophy in advanced age-related macular degeneration, one of the most common causes, where areas of retinal pigment epithelial atrophy produce well-demarcated window defects corresponding precisely to the atrophic areas
- Pattern dystrophies and other inherited retinal pigment epithelial conditions producing focal areas of pigment epithelial thinning
- Resolved chorioretinitis or other inflammatory or infectious processes leaving behind an area of pigment epithelial atrophy or scarring
- Any other cause of focal or diffuse retinal pigment epithelial atrophy or attenuation, including some inherited retinal degenerations
Distinguishing From Other Angiographic Patterns
- Leakage from choroidal neovascularization shows progressively increasing hyperfluorescence with indistinct, blurring borders in later frames, in clear contrast to the static, sharply demarcated appearance of a window defect
- Pooling, as seen with subretinal fluid in central serous chorioretinopathy or other conditions, shows fluorescence accumulating within a defined anatomic space, typically increasing in intensity and sometimes changing shape over the course of the angiogram
- Staining, as seen with drusen or scar tissue, shows a gradual increase in fluorescence intensity within the fixed boundaries of the anatomic structure, without the leakage pattern of active neovascularization but also without the fully static behavior of a pure window defect
Clinical Use
Recognizing a window defect for what it is, simple absence of normal pigment masking rather than any form of active leakage or abnormal fluid accumulation, prevents misinterpreting a benign or stable atrophic process as active neovascular or inflammatory disease requiring urgent treatment.
Correctly identifying window defects is particularly important when evaluating a patient with age-related macular degeneration for choroidal neovascularization, since correctly distinguishing pure geographic atrophy (producing window defects) from neovascular disease (producing progressive leakage) directly determines whether anti-VEGF treatment is indicated.
Correlation With Other Imaging
Optical coherence tomography, showing direct structural evidence of retinal pigment epithelial thinning or loss corresponding to the angiographic window defect, provides complementary structural confirmation and is now often used alongside or even in place of fluorescein angiography for characterizing geographic atrophy in routine clinical practice.
Clinical Significance
Understanding the window defect pattern is fundamental angiographic literacy, since correctly distinguishing this benign, non-leaking pattern from the various forms of pathologic leakage and staining directly shapes treatment decisions across a wide range of retinal conditions, from age-related macular degeneration to inflammatory chorioretinal disease.
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From Choroida — the team behind this siteReferences
- Gass JD. Stereoscopic Atlas of Macular Diseases: Diagnosis and Treatment. 4th ed. St. Louis: Mosby; 1997.
- Yannuzzi LA. The Retinal Atlas. 2nd ed. Edinburgh: Elsevier; 2017.
- Bird AC, Bressler NM, Bressler SB, et al. An international classification and grading system for age-related maculopathy and age-related macular degeneration. Surv Ophthalmol. 1995;39:367-374.
- Holz FG, Bindewald-Wittich A, Fleckenstein M, et al. Progression of geographic atrophy and impact of fundus autofluorescence patterns in age-related macular degeneration. Am J Ophthalmol. 2007;143:463-472.
Test yourself
A few questions straight from this article.
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A retinal pigment epithelium window defect on fluorescein angiography results from what?
Melanin in the pigment epithelium normally masks fluorescence from the choroidal circulation; when the epithelium is thinned, atrophic or absent, that masking is lost and the choroidal fluorescence shows through. -
When does a retinal pigment epithelium window defect first become visible on fluorescein angiography?
A window defect appears early in the angiogram, timed to the underlying choroidal fluorescence it is unmasking, with sharply defined borders matching the area of pigment epithelial loss. -
How does a window defect behave in the later frames of a fluorescein angiogram?
The defining behaviour is a static one: the defect neither enlarges nor intensifies, and it does not leak or pool as the angiogram progresses. -
Which angiographic behaviour indicates choroidal neovascular leakage rather than a window defect?
Leakage from choroidal neovascularization grows in extent and intensity with indistinct, blurring borders on later frames, in clear contrast to the static, sharply bordered window defect. -
Which angiographic pattern describes pooling, as seen with subretinal fluid in central serous chorioretinopathy?
Pooling collects dye inside a defined anatomic space, typically increasing in intensity and sometimes changing shape as the angiogram runs. -
Which angiographic pattern is characteristic of staining, as seen with drusen or scar tissue?
Staining brightens gradually within the fixed boundaries of the anatomic structure, lacking the spread of active leakage but also lacking the fully static behaviour of a pure window defect. -
Which condition is one of the most common causes of retinal pigment epithelium window defects?
Areas of pigment epithelial atrophy in geographic atrophy produce well-demarcated window defects corresponding precisely to the atrophic areas. -
Which inherited group of disorders produces focal pigment epithelial thinning seen as window defects?
Pattern dystrophies and other inherited pigment epithelial conditions create focal areas of epithelial thinning that behave as window defects on angiography. -
In age-related macular degeneration, correctly identifying window defects directly determines what?
Separating pure geographic atrophy, which produces window defects, from neovascular disease, which produces progressive leakage, is what decides whether anti-VEGF treatment is indicated. -
What role does optical coherence tomography play alongside an angiographic window defect?
Optical coherence tomography shows the pigment epithelial thinning or loss directly, and is now often used alongside or even in place of angiography for characterizing geographic atrophy.
