Purpose:
To compare the ability to discriminate depth using 2 dimensional (2–D) still images, 2–D videography and 3 dimensional (3–D) stereo videography captured through a slit lamp camera system.
Methods:
Ten subjects were tested. All subjects had visual acuity of 20/20 or better in each eye, stereo acuity of 40 seconds of arc or better and correctly identified 8 of 8 misaligned bars with the Verhoeff stereoptor. Eight pairs of vertical bars on the Verhoeff stereoptor were imaged through a Haag–Streit BQ 900 slit lamp, captured via Sony DXC–390 video camera and presented to each subject on a Sony high resolution video monitor. Each subject viewed the pairs displayed as 2–D still images, 2–D video and 3–D stereo video. The video images were displayed dynamically with the subject able to control the slit lamp joystick and therefore the video image. In each setting subjects were asked to state which vertical bar was in front and the number correct recorded.
Results:
Depth discrimination was poor based solely on 2–D still images alone, but tripled with 3–D dynamic stereo video imaging. (Figure 1)
Conclusions:
3–D dynamic stereo video imaging enhances discrimination of depth compared to 2–D still images when subjects are presented Verhoeff stereoptor bars captured through a slit lamp camera system. 2–D dynamic video imaging also appears to improve the perception of depth verses still imaging. Although improved diagnostic capability must be balanced in the short term versus technology development costs and bandwidth constraints, a real time dynamic stereoscopic slit lamp examination remains the ultimate goal for teleophthalmology.
Keywords: binocular vision/stereopsis • depth • imaging/image analysis: clinical