Michael Kalloniatis and Charles Luu
Stereopsis refers to our ability to appreciate depth, that is the ability to distinguish the relative distance of objects with an apparent physical displacement between the objects. It is possible to appreciate the relative location of objects using one eye (monocular cues). However, it is the lateral displacement of the eyes that provides two slightly different views of the same object (disparate images) and allow acute stereoscopic depth discrimination.
Several strong monocular cues allow relative distance and depth to be judged. These monocular cues include:
Relative Size: Retinal image size allow us to judge distance based on our past and present experience and familiarity with similar objects. As the car drives away, the retinal image becomes smaller and smaller. We interpret this as the car getting further and further away. This is referred to as size constancy. A retinal image of a small car is also interpreted as a distant car (figure 1).
Figure 1. Relative size. A retinal image of a small car is considered to be distant
Interposition: Interposition cues occur when there is overlapping of objects. The overlapped object is considered further away (figure 2).
Figure 2. Interposition. The blue circle is reported to be closer since it overlaps the red circle
Linear Perspective: When objects of known distance subtend a smaller and smaller angle, it is interpreted as being further away. Parallel lines converge with increasing distance such as roads, railway lines, electric wires, etc (figure 3).
Figure 3. Linear perspective. Parallel lines such as railway lines converge with increasing distance
Aerial Perspective: Relative colour of objects give us some clues to their distance. Due to the scattering of blue light in the atmosphere, creating wall of blue light, distance objects appear more blue (figure 4). Thus distant mountains appear blue. Contrast of objects also provide clues to their distance. When the scattering of light blurs the outlines of objects, the object is perceived as distant. Mountains are perceived to be closer when the atmosphere is clear.
Figure 4. Aerial perspective. Mountains in the distance appear more blue
Light And Shade: Highlights and shadows can provide information about an objects dimensions and depth (figure 5). Because our visual system assumes the light comes from above, a totally different perception is obtained if the image is viewed upside down.
Figure 5. Highlights and shadows provide information about depth
Monocular Movement Parallax: When our heads move from side to side, objects at different distances move at a different relative velocity. Closer objects move against the direction of head movement and farther objects move with the direction of head movement.
Stereopsis is an important binocular cue to depth perception. Stereopsis cannot occur monocularly and is due to binocular retinal disparity within Panums fusional space. Stereopsis is the perception of depth produced by binocular retinal disparity. Therefore, two objects stimulates disparate (non-corresponding) retinal points within Panums fusional area.
Fusion describes the neural process that brings the retinal images in the two eyes to form one single image. Fusion occurs to allow single binocular vision. Fusion takes place when the objects are the same. When the objects are different, suppression, superimposition or binocular (retinal) rivalry may occurs. Suppression occurs to eliminate one image to prevent confusion. Superimposition results in one image presented on top of the other image. Binocular rivalry describes alternating suppression of the two eyes resulting in alternating perception of the two images. This usually occurs when lines are presented to the two eyes differ in orientation, length or thickness. An example of binocular rivalry occurs when one eye is presented with a horizontal line and the other eye is presented with a vertical line. Binocular rivalry occurs at the intersection of the lines and some suppression also exists (figure 6)
Figure 6. (a) Binocular rivalry can be demonstrated by placing a pen between yourself and the screen. Keep you eye on the tip of the pen and notice the two bars merge. You may need to slowly move the pen from the screen towards you. (b) Result of (a)
Panums fusional area is the region of binocular single vision. Outside Panums fusional area, physiological diplopia occurs. Using the haplopic method of determining the horopter, Panums area can be determined (figure 7).
Figure 7. Haplopic method of determining the horopter involves locating the region of single binocular vision at a distance of 40cm.Panums fusional area lies between the outer and inner limits of the region of single binocular vision
Retinal disparity: Retinal disparate points are retinal points that give rise to different principal visual direction and diplopia. However, retinal disparity within Panums fusional area (zone of single binocular vision) can be fused resulting in single vision. Retinal disparity is essential for stereoscopic depth perception as stereoscopic depth perception results from fusion of slightly dissimilar images. Due to the lateral displacement of our eyes, slightly dissimilar retinal images result from the different perception of the same object from each eye.
Clinical Tests used to measure Stereopsis
There are two groups of clinical tests used to measure stereopsis. These are the contour stereotests and the random-dot stereotest. Random-dot stereograms were first used by Julesz (1960) to eliminate monocular cues. As there are no contours, depth perception (stereopsis) can only be appreciated when binocular fusion occurs. Two process of stereopsis are used and these are local and global stereopsis. Local stereopsis exists to evaluate the two horizontally disparate stimuli. This process is sufficient for contour stereotests. Global stereopsis is required in random-dot stereogram when the evaluation and correlation of corresponding points and disparate points are needed over a large retinal area.
An example of a contour stereotest used in the clinic is the Titmus Fly Stereotest. In the Titmus Fly Stereotest, horizontal disparity is presented via the vectographic technique (Fricke and Siderov, 1997). When tested a 40 cm the fly has a disparity of 3,600 sec of arc; the disparity of the animals range from 400 100 sec of arc and the disparity of the Wirt rings range from 800 40 sec of arc (figure 8).
Figure 8. Titmus Fly Stereotest
Examples of random-dot stereotests used in the clinic are the Frisby Stereotest, the Randot Stereotest, the Random-dot E Stereotest and the Lang Stereotest. The Frisby Stereotest (figure 9) uses real depth to determine stereoacuity. Three perspex of different thicknesses are used. Four squares of geometric shapes are painted on one side of the perspex. In one of the squares, a circle of these geometric shape is painted on the other side of the perspex. Both the Randot (figure 10) and the Random-dot E uses crossed polarised filters. Disparity is also constructed vectographically. The Randot Stereotest uses modified animals and ring designs with random dot backgrounds to eliminate monocular cues. The Lang Stereotest uses a panographic technique (Fricke and Siderov, 1997) to present disparity, therefore, no filters are required. Patients are required to identify pictures on the Lang Stereotest. The Lang II Stereotest has a monocularly visible shape on it (figure 11).
Figure 11. The Lang II
All the tests provides a measure of stereoacuity by asking the patient to identify the correct target that has stereoscoptic depth (target with disparity). The working distance and interpupillary distance will need to be taken into consideration when calculating stereoacuity. Patients with disturbed binocular vision or different refractive error in one eye, will perform poorly on depth discrimination tests.
We like to thank Tim Fricke for providing Figures 8-11.
Fricke TR and Siderov J (1997) Stereopsis, stereotest and their relation to vision screening and clinical practice.Clin Exp Optom. 80: 165-172.
Julesz B. Binocular depth perception of computer generated patterns.Bell Syst Tech J.1960;39:11251162.2.
Moses RA and Hart WM (1987)Adlers Physiology of the eye, Clinical Application, 8th ed. St. Louis: The C. V. Mosby Company.
Ogle KN (1950)Researches in Binocular Vision. London: Saunders. 1950
Schwartz SH (1999)Visual Perception, 2nd ed. Connecticut: Appleton and Lange.
Last Update: June 6, 2007.
Michael Kalloniatiswas born in Athens Greece in 1958. He received his optometry degree and Masters degree from the University of Melbourne. His PhD was awarded from the University of Houston, College of Optometry, for studies investigating colour vision processing in the monkey visual system. Post-doctoral training continued at the University of Texas in Houston with Dr Robert Marc. It was during this period that he developed a keen interest in retinal neurochemistry, but he also maintains an active research laboratory in visual psychophysics focussing on colour vision and visual adaptation. He was a faculty member of the Department of Optometry and Vision Sciences at the University of Melbourne until his recent move to New Zealand. Dr. Kalloniatis is now the Robert G. Leitl Professor of Optometry, Department of Optometry and Vision Science, University of Auckland.e-mail:email@example.com
Charles Luuwas born in Can Tho, Vietnam in 1974. He was educated in Melbourne and received his optometry degree from the University of Melbourne in 1996 and proceeded to undertake a clinical residency within the Victorian College of Optometry. During this period, he completed post-graduate training and was awarded the post-graduate diploma in clinical optometry. His areas of expertise include low vision and contact lenses. During his tenure as a staff optometrist, he undertook teaching of optometry students as well as putting together the Cyclopean Eye, in collaboration with Dr Michael Kalloniatis. The Cyclopean Eye is a Web based interactive unit used in undergraduate teaching of vision science to optometry students. He is currently in private optometric practice as well as a visiting clinician within the Department of Optometry and Vision Science, University of Melbourne.
Read more from the original source:
Perception of Depth by Michael Kalloniatis and Charles Luu ...
- The Architecture of the Human Fovea Webvision - November 8th, 2021
- The Role of Reproductive Hormones in Postpartum Depression - November 8th, 2021
- 'Limb vs. Tail' lecture articulates variations of axolotl regeneration during research development The Maine Campus - The Maine Campus - November 8th, 2021
- Century Therapeutics to Present at the 63rd American Society of Hematology Annual Meeting and Host Virtual Research & Development Update -... - November 8th, 2021
- Clade Therapeutics Raises $87 Million Series A Financing to - GlobeNewswire - November 8th, 2021
- Orchard Therapeutics Reports Third Quarter 2021 Financial Results and Highlights Recent ... - The Bakersfield Californian - November 8th, 2021
- NextCure Reports Third Quarter 2021 Financial Results and Provides Business Update - Yahoo Finance - November 8th, 2021
- Bristol Myers Squibb to Highlight More than 80 Abstracts at ASH 2021 Demonstrating Strength of Innovative Therapeutic Platforms Improving Outcomes for... - November 8th, 2021
- Atara Biotherapeutics to Present Eight Abstracts at the 63rd American Society of Hematology (ASH) Annual Meeting, Including First Presentation of... - November 8th, 2021
- CRISPR Therapeutics Provides Business Update and Reports Third Quarter 2021 Financial Results - GlobeNewswire - November 8th, 2021
- UVA Science and Engineering Faculty Win 12 NSF Career Awards - University of Virginia - November 8th, 2021
- MAGENTA THERAPEUTICS, INC. Management's Discussion and Analysis of Financial Condition and Results of Operations. (form 10-Q) - marketscreener.com - November 8th, 2021
- Ronawk using stem cell tech developed at Olathe lab to advance liver cancer research in Turkey - Startland News - October 5th, 2021
- StemExpress Partners with the Alliance for Regenerative Medicine to Provide COVID-19 Testing for the Cell and Gene Meeting on the Mesa - WSAW - October 5th, 2021
- Researching the Safety and Effectiveness of Stem Cells to Treat 'Long Covid' - Entrepreneur - October 5th, 2021
- Global Hemoglobinopathies Markets, 2021-2028 - High Unmet Needs / Increasing R&D Investment / Initiatives to Improve Disease Awareness -... - October 5th, 2021
- Faster healing of wounds can decrease pain and suffering and save lives - KY3 - October 5th, 2021
- Stanford neuroscientist's 'assembloids' pave the way for innovative brain research - Scope - October 5th, 2021
- Exosome therapeutic Market 2021 is Showing Impressive Growth by 2028 | Trends, Share, Size, Top Key Players Analysis and Forecast Research EcoChunk -... - October 5th, 2021
- BrainStorm to Present at the 2021 Cell & Gene Meeting on the Mesa - WWNY - October 5th, 2021
- Cell Based Assay & High Content Screening Market Report 2021: The Workhorse of the Pharmaceutical Industry is Becoming a Central Player in... - October 5th, 2021
- Advancing the Development of Innovative Veterinary Products - FDA.gov - October 5th, 2021
- Pharmaxis Cleared To Progress To Phase 2 Bone Marrow Cancer Trial - WBKO - October 5th, 2021
- $500K Grant Supports Research on Muscle Growth in Pigs, With Broader Health Implications - Maryland Today - July 22nd, 2021
- EU approves bluebird bio's CALD gene therapy Skysona - PMLiVE - July 22nd, 2021
- Secrets and pies: the battle to get lab-grown meat on the menu - The Guardian - July 22nd, 2021
- Biomedical Warming and Thawing Devices Market Revenue to Cross USD 308 Mn by 2027: Global Market Insights Inc. - Markets Insider - July 22nd, 2021
- A Recovery for All Of Us: New York City Invests $1 Billion in Life Sciences - Brooklyn Daily Eagle - July 22nd, 2021
- The growing global "infodemic" around stem cell therapies - Axios - June 25th, 2021
- NanoString Launches nCounter Stem Cell Characterization Panel to Advance the Development of Stem Cell Therapy - Yahoo Finance - June 25th, 2021
- Catalent to Acquire RheinCell Therapeutics, Strengthening a Path Towards Industrialization of Induced Pluripotent Stem Cell-based Therapies - Yahoo... - June 25th, 2021
- Immusoft Announces Formation of Scientific Advisory Board - Business Wire - June 25th, 2021
- Jasper Therapeutics and Aruvant Announce Research Collaboration to Study JSP191, an Antibody-Based Conditioning Agent, with ARU-1801, a Novel Gene... - June 25th, 2021
- Gamida Cell Announces Publication in Blood, the Journal of the American Society of Hematology, of the First Pivotal Trial to Evaluate a Cell Therapy... - June 25th, 2021
- More than 800 medicines are in development for diseases that disproportionately affect racial and ethnic communities - PRNewswire - June 25th, 2021
- Andrs Garca Receives Distinguished Professor Award | Research - Research Horizons - June 25th, 2021
- Local foundation awards $1.25 million to MIND Institute to study rare genetic condition - UC Davis Health - June 25th, 2021
- MeCP2 is a microsatellite binding protein that protects CA repeats from nucleosome invasion - Science Magazine - June 25th, 2021
- The Stem Cell Manufacturing market is projected to reach USD 18.0 billion by 2026 from USD - GlobeNewswire - May 28th, 2021
- Jasper Therapeutics Announces New Clinical Trial with the National Institute of Allergy and Infectious Diseases to Evaluate JSP191 in Chronic... - May 28th, 2021
- Global Flow Cytometry Market (2020 to 2026) - by Technology, Product and Service, Application, End-user and Geography - ResearchAndMarkets.com -... - May 28th, 2021
- Meso-Brain project explores 3D printed stem cells to treat neurological conditions - 3D Printing Industry - May 28th, 2021
- Moderna Highlights Advances in Platform Science and Innovative Vaccine Research at Fourth Annual Science Day - Business Wire - May 28th, 2021
- GPB Scientific Announces Additional Growth Financing to Support Commercialization of Curate Cell Processing System for Next-Generation Cell & Gene... - May 28th, 2021
- TScan Therapeutics Adds to Executive Leadership Team and Board of Directors - BioSpace - May 28th, 2021
- Bone Therapeutics Provides First Quarter 2021 Business Update - GlobeNewswire - May 28th, 2021
- Merakris Therapeutics, Inc. Announces FDA Clearance for - GlobeNewswire - May 28th, 2021
- Stem Cell Manufacturing Market 2021 | Research With Size, Growth, Manufacturers, Key Segment, Analysis, Development Status, Segments and 2027... - February 19th, 2021
- Tissue regeneration: Reserve or reverse? - Science Magazine - February 19th, 2021
- Global Scaffold Technology Market Is Expected to Reach USD 2.16 billion by 2028 : Fior Markets - GlobeNewswire - February 19th, 2021
- Recombinant Growth Factors to Account for Over 45% of Overall Demand through 2031: Persistence Market Research - PRNewswire - February 19th, 2021
- The Untapped Potential of Cell and Gene Therapy - AJMC.com Managed Markets Network - February 19th, 2021
- Century Therapeutics Significantly Expands Capabilities with New Operational, Laboratory and Manufacturing Facilities in Pennsylvania and New Jersey -... - February 19th, 2021
- Cell Therapy Processing Market To Grow Value $12062 Million By 2026 | Latest Research Report - PharmiWeb.com - February 19th, 2021
- Global Stem Cell Therapy Market 2020 | Demand and Scope with Outlook, Business Strategies, Challenges and Forecasts to 2025 KSU | The Sentinel... - February 19th, 2021
- Humanized Mouse and Rat Model Market: Increased development of monoclonal antibodies and improved healthcare to drive the market - BioSpace - February 19th, 2021
- Iterion Therapeutics Secures $17 Million to Advance Development of Tegavivint in Multiple Tumor Settings - PRNewswire - February 19th, 2021
- Global Apoptosis Assays Market Estimated To Expand At A Robust CAGR By 2027||Promega, Abcam plc, Research And Diagnostic Systems, Inc., Sartorius AG,... - February 19th, 2021
- Tibidabo Scientific Industries Strengthens its Core Executive Team with the Appointment of Industry Veteran, John LaViola as Chief Technology Officer... - February 19th, 2021
- Global Cell Expansion Market Value Projected to Expand by 2021-2026 | Thermo Fisher Scientific, Inc., GE Healthcare, Lonza Group Ltd., Becton,... - February 19th, 2021
- How Irish medtech came to thrive - Med-Tech Innovation - February 19th, 2021
- Translational Regenerative Medicine Market: Immunotherapy is projected to be the fastest growing segment during the forecast period - BioSpace - February 11th, 2021
- Ensoma Launches to Pioneer Next-Generation In Vivo Approach to Deliver First Off-the-shelf Genomic Medicines - Business Wire - February 11th, 2021
- Notch Therapeutics Closes $85 Million Series A Financing to Develop Pipeline of Renewable Stem Cell-Derived Cancer Immunotherapies - PRNewswire - February 11th, 2021
- Global Biopreservation Market Is Expected to Reach USD 7.67 Billion by 2028 : Fior Markets - GlobeNewswire - February 11th, 2021
- Apollomics, Inc. and Iterion Therapeutics Announce Exclusive Collaboration and License Agreement to Develop and Commercialize Tegavivint in Greater... - February 11th, 2021
- Stem Cell Therapy Market Revenue, Key Players, Supply-Demand, Investment Feasibility and Forecast By 2029: Osiris Therapeutics, NuVasive, Chiesi... - February 11th, 2021
- 2020 Outlook on the Global Singlecell Technology Industry - Market Size was Over $800 Million in 2019 - ResearchAndMarkets.com - Business Wire - February 11th, 2021
- Stem Cell Cryopreservation Equipments Market Size Report: Strategies of Key Manufacturers, Project Investment of New Industries: Chart, Worthington... - February 11th, 2021
- Seattle Cancer Care Alliance Celebrates 20 Years of Innovation in Cancer Treatment and Care - Business Wire - February 11th, 2021
- Outlook on the CRISPR Gene Editing Global Market to 2030 - Analysis and Forecasts - GlobeNewswire - February 11th, 2021
- Researchers curb local immune response in horses receiving stem cell injury therapy - Horsetalk - February 7th, 2021
- Biobanking Market Report Research and Global Outlook 2021 to 2025 KSU | The Sentinel Newspaper - KSU | The Sentinel Newspaper - February 7th, 2021
- Animal Stem Cell Therapy Market By Product Type (Dogs, Horses) And By End-Users/Application (Veterinary Hospitals, Research Organizations) Market... - February 6th, 2021
- Stem Cell Assay Market Share, Demand, Manufacturers and Forecast till 2027 | Merck & Co., Thermo Fisher Scientific, GE Healthcare, Agilent... - February 6th, 2021
- Global Apoptosis Assays Market Set To Grow At Healthy CAGR Of 11.10% By 2027||Abcam plc, Research And Diagnostic Systems, Inc., Sartorius AG, Biotium,... - February 6th, 2021
- Jill Biden signals White House resolve on cancer research: This is the fight of our lives - The Cancer Letter - February 6th, 2021
- Tiny sensor technique reveals cellular forces involved in tissue generation - Brown University - February 6th, 2021
- Global Stem Cell Partnering Terms and Agreements Directory 2020: Company AZ, Headline Value, Stage of Development at Signing, Deal Component Type,... - February 6th, 2021
- Perales Examines the Impact of COVID-19 on Recipients of Cellular Therapies for Cancer - OncLive - February 6th, 2021