Stereoscopic Amblymeter  (SAM)

          Based upon the Hofeldt Bridge, U.S. Patent Applications 61/627,815 and 13/655,283.

Pediatric Version

1.     Self-Test Game Algorithm (to be released in 2016)

2.     Hand-held Stereoscope Available, $1295.00

Adult Version

1.    Brightness Matching Algorithm

2.    Hand-held Stereoscope, Available, $1295.00

Hofeldt Bridge diagram Link

Hofeldt Bridge

Albert J. Hofeldt, MD was the first to described the rivalrous interplay between the right and left sides visual system for measuring the relative brightness sense in U.S. Applications 61/627,815 and 13/655,283.  The Hofeldt Bridge consists of two rivalrous image pairs where the brightness of each pair is diametrically opposed, the pairs are aligned vertically, and the brighter images of the two pairs are reciprocally positioned.  When the rivalrous pairs are fused, the subject sees a top and a bottom image and by directly comparing the brightness of these vertically aligned images, the relative function of the right and left sides of the visual system is determined.  In a balanced visual system, the brightness of the top and bottom images appears of equal brightness.  When the top and bottom images appear of different brightness, the right and left sides of the visual system are not of equal function.  By reducing the brightness of the brighter image of the rivalrous pair being viewed by the better eye to the endpoint of brightness equality of the top and bottom fused images, the right and left sides of the visual system are brought into balance and the defect is quantified.     

For balancing two sides of a system, the Hofeldt Bridge is analogous to the Wheatstone Bridge.  The Wheatstone Bridge was first described by Samuel Hunter Christie in 1833 and became popularized by Charles Wheatstone in 1843.  The Wheatstone Bridge connects two sides of an electrical system for the purpose of determining neutrality of the resistance between the two sides of an electrical circuit and by so doing the resistance of an unknown resistor can be precisely measured.  In comparison and in distinction, the Hofeldt Bridge utilizes two rivalrous image pairs to measure the equality of the function of the two sides of the visual system.  In 1852 Wheatstone invented the stereoscope which visually combines images from the two sides of visual system, but there is no evidence that Charles Wheatstone conceived of applying principles of the Wheatstone Bridge to measure the relative function of the two sides of the visual system as does the Hofeldt Bridge.

It is well documented that a number of diseases cause an imbalance in the right-left relative brightness sense.  For example the brightness sense is diminished in (1) optic nerve diseases such as glaucoma, optic neuritis, compressive lesion of the optic nerve, in (2) ischemic retinal diseases, and in (3) amblyopia.

The brightness sense is also important in synchronizing the apparent speed of a moving object, such as a baseball.  In an article (ARCH OPHTHALMOLOGY 114, DEC 1996) entitled, Baseball Hitting, Binocular Vision, and the Pulfrich Phenomenon by Albert Hofeldt, MD; Frank Hoefle, MD; and Ben Bonafede showed that by simply dimming the brightness of one eye with a filter severely reduced the hitting ability of baseball players.

In Poster #443 presented at the American Academy of Ophthalmology meeting in 2011, Steven A. Kane, MD, PhD. and Albert Hofeldt, MD reported using an Amblymeter based upon the Hofeldt Bridge for detecting and quantifying Amblyopic and other relative afferent defects in children.  The Amblymeter was reported to have a sensitivity of 100% and a specificity of 88%.