This 60 year-old woman complained of decreased vision in the right eye. The above imaging was performed on the macula.

What is this imaging called?

Answer
Optical coherence tomography

Do you know the principle of this technique?

Answer
OCT is a non-invasive, non-contact imaging system which produces 
micron-resolution retinal images in vivo. It is analogous to B-scan
ultrasound except that it uses light instead of sound. The use of light 
offers the inherent advantage of increased resolution and speed of 
acquisition compared to sound. Unlike ultrasound, contact between the
probe and the eye is not required so that slit-lamp biomicroscopy of the retina can occur simultaneously with image acquisition.

The light used is near-infrared light (830-850 nm)which is directed as 

a beam into the tissue and using the principle of low coherence 
interferometry to measure the time delay of reflected or backscattered
light from the microstructures within the tissue. Computerized image processing then calculates optical reflectivity, and the images are displayed
in false-colors where bright colors (red to white) represent areas of high optical reflectivity and dark colors (blue to black) correspond to regions
of low or no relative reflectivity.

What abnormalites are visible?

Answer
There is a break in the retina with an overlying operculum.
As the imaging is performed over the macula and the patient 
has decreased vision. The diagnosis is macular hole.

What physical sign may be elicited?

Answer
A positive Watzke's sign ie interruption of a fine vertical line focused on the hole.