Ophthalmic Imaging and Photography Flashcards

During fluorescein angiography, a patient develops early hyperfluorescence that increases in intensity and size throughout the study but does not leak beyond the lesion boundary in the late frames. This pattern is most consistent with which finding?

Answer: Window defect from RPE atrophy

A window defect caused by RPE atrophy transmits background choroidal fluorescence, producing hyperfluorescence that brightens as the choroidal flush intensifies but fades symmetrically with the background and does not enlarge or leak beyond the lesion margin in late frames. Classic CNV leaks and expands; occult CNV shows late stippled leakage; macroaneurysms often show hypofluorescent halos or wall staining.

When performing optical coherence tomography angiography (OCTA) on a patient with diabetic macular edema, the en face slab most likely to reveal the earliest signs of deep capillary plexus dropout is:

Answer: Deep capillary plexus slab (IPL to OPL)

The deep capillary plexus (DCP), located at the level of the inner nuclear and outer plexiform layers, is disproportionately affected early in diabetic retinopathy compared to the superficial plexus. OCTA studies have shown that DCP flow deficits and nonperfusion precede clinical microaneurysm detection and superficial plexus changes. The outer retina and choriocapillaris are not involved in the primary diabetic microangiopathy of the inner retina.

A photographer captures a fundus image in which the optic nerve appears temporally displaced toward the center of the frame, but the macula is not visible. The most likely cause, assuming the patient is cooperative and the pupil is adequately dilated, is:

Answer: The patient is fixating too nasally during the image capture

When a patient fixates nasally (toward their nose) instead of straight ahead or slightly temporally, the fundus camera captures the optic nerve prominently while the macula moves out of frame temporally. Proper fixation instructions are critical. Vertical camera tilt would displace structures superiorly or inferiorly; corneal astigmatism affects image clarity but not gross anatomical positioning; flash intensity affects exposure, not field position.

On a Heidelberg Spectralis OCT, a technician notices that the automatic layer segmentation places the ILM boundary several microns into the vitreous above an area of epiretinal membrane. The most appropriate action before saving the report for the physician is:

Answer: Manually correct the ILM segmentation layer using the correction tool to follow the actual retinal surface

Automated segmentation algorithms can misidentify the ILM boundary when an epiretinal membrane is present, treating the ERM surface as the inner retinal boundary and causing erroneous thickness measurements. The standard of care is to manually correct the segmentation in the software before the report is finalized, ensuring accurate retinal thickness maps. Accepting the error without correction yields misleading quantitative data for the physician. Rescanning will not resolve an inherent segmentation algorithm limitation caused by the ERM reflectivity.

Indocyanine green angiography (ICGA) is preferred over fluorescein angiography for imaging which of the following conditions, specifically because ICG molecules are nearly entirely protein-bound and remain within the choriocapillaris fenestrations longer?

Answer: Polypoidal choroidal vasculopathy

ICG dye is approximately 98% protein-bound to plasma albumin, making it ideal for choroidal imaging because it does not leak rapidly through the fenestrated choriocapillaris as fluorescein does. Polypoidal choroidal vasculopathy (PCV) involves abnormal choroidal vessels beneath the RPE, and ICGA is the gold-standard imaging modality for identifying the characteristic polypoidal lesions and branching vascular networks that are invisible or poorly defined on FA. The other listed conditions involve primarily retinal or inner ocular structures better assessed with FA.

A COT is asked to acquire an ultra-widefield fundus image (200°) on a patient with a high myopic refractive error of −14.00 D. Compared to an emmetropic patient, the technician should anticipate which specific imaging challenge unique to high myopia on this platform?

Answer: Image minification will compress peripheral pathology and require careful attention to the far periphery for lesion detection

In high myopia, the significantly elongated axial length causes the ultra-widefield system to capture a larger physical area of retina. This results in image minification — the retinal structures appear smaller within the image frame. Peripheral pathology such as lattice degeneration, atrophic holes, and early tears can appear compressed and subtle, demanding careful inspection. Image magnification (the opposite) would occur in hyperopia. Contact lens use is not required for modern non-contact UWF systems. The image does not split — it remains a single composite capture.