Choroidal thickness in retinal pigment epithelial tear as measured by spectral domain optical coherence tomography

Investigation of artifacts in retinal and choroidal OCT angiography with a contrast agent

Optical coherence tomography angiography (OCTA) has recently emerged for imaging vasculature in clinical ophthalmology. Yet, OCTA images contain artifacts that remain challenging to interpret. To help explain these artifacts, we perform contrast-enhanced OCTA with a custom-designed wide-field ophthalmoscope in rats in vivo. We choose an intravascular contrast agent (Intralipid) with particles that are more isotropically scattering and more symmetrically shaped than red blood cells (RBCs). Then, by examining how OCTA artifacts change after contrast agent injection, we attribute OCTA artifacts to RBC-specific properties. In this work, we investigate retinal and choroidal OCTA in rats with or without melanosomes, both before and after contrast agent injection, at a wavelength at which scattering dominates the image contrast (1300 nm). First, baseline images suggest that high backscattering of choroidal melanosomes accounts for the relatively dark appearance of choroidal vessel lumens in OCTA. Second, Intralipid injection tends to eliminate the hourglass pattern artifact in OCTA images of vessel lumens and highlights vertical capillaries that were previously faint in OCTA, showing that RBC orientation is important in determining OCTA signal. Third, Intralipid injection increases lumen signal without significantly affecting the tails, suggesting that projection artifacts, or tails, are due to RBC multiple scattering. Fourth, Intralipid injection increases the side-to-top signal ratio less in choroidal vessel lumens of pigmented rats, suggesting that melanosome multiple scattering makes the hourglass artifact less prominent. This study provides the first direct experimental in vivo evidence to explain light scattering-related artifacts in OCTA.

Retinal Pigment Epithelial Tear After Intravitreal Ranibizumab Treatment for Retinal Angiomatous Proliferation

PURPOSE

To evaluate the incidence and associated risk factors of retinal pigment epithelium (RPE) tears after intravitreal ranibizumab injection treatment for retinal angiomatous proliferation (RAP).

DESIGN

Retrospective, observational case series.

METHODS

Ninety-eight treatment-naïve RAP eyes (86 patients) that received intravitreal ranibizumab injections were included. All patients were treated with an initial series of 3 monthly loading injections, followed by further injections as required. Baseline characteristics and features were evaluated as potential risk factors for RPE tearing. The visual and anatomic outcomes after treatment were evaluated at 12 months from baseline.

RESULTS

RPE tears had developed in 8.2% (8) of the eyes by 12 months. Of these, all had pigment epithelium detachment (PED) at baseline, and the majority (7) had developed an RPE tear within 3 months. Multiple regression analysis showed that higher PED (odds ratio [OR] = 1.411, 95% confidence interval [CI] = 1.199-1.888, P = .011) and thinner choroid (OR = 0.815, 95% CI = 0.719-0.912, P = .023) were associated with a higher risk of RPE tearing. The mean best-corrected visual acuity of the patients with RPE tearing (0.56 ± 0.49 logarithm of the minimal angle of resolution [logMAR]) was significantly worse at 12 months than that of patients without RPE tearing (0.74 ± 0.55 logMAR, P = .009) after treatment.

CONCLUSIONS

RPE tears developed in 8.2% of eyes with RAP during the 12 months following ranibizumab injections. Higher PED height and thinner subfoveal choroidal thickness were associated with the development of RPE tears after ranibizumab treatment for RAP.