The document summarizes a study that investigated colour vision performance through visual acuity and colour arrangement tests. 8 participants had their visual acuity measured using Snellen letters and were then asked to arrange 42 colour targets into groups based on colour and saturation. Most participants were able to correctly arrange the colours, though a few made minor mistakes by interchanging targets within colour groups. The results confirmed that good visual acuity is necessary but not sufficient for good colour vision performance.
Analysis of the Difference between the Normal Vision and the Experiencing Cat...IJERA Editor
The optical instruments design for binocular vision has become an earnest demand towards the arrival of an
ageing society. It is necessary to measure how color difference between left and right images by elderly people,
which the color rivalry occurs. In this study, we measured the limit of binocular color fusion in the normal vision
and the cataract experiencing vision which is aiming to simulate the elderly vision. The result shows that the
color fusion limit curve in cataract experiencing vision are very similar with those in normal vision. Compared
with the binocular color fusion limit in normal vision Δλdn, the binocular color fusion limit in cataract
experiencing vision Δλdc is approximately 3~39nm increased on the central vision, 4~22nm on the retinal
eccentricity of 3°, 5~23nm on the retinal eccentricity of 6°, and 5~24nm on the retinal eccentricity of 9°. The
results also reveal that a similar limit is observed in the range of 520~560nm in both normal and cataract
experiencing visions, which might give some potential evidences for designing 3D equipment. In addition, the
minimum value of the binocular color fusion limit exists at 590nm either in the normal vision or the cataract
experiencing vision during all retinal eccentricities.
Color vision physiology, defects and different testing ProceduresRaju Kaiti
Color vision Physiology, Different types of Color vision defects, different testing procedures, trichromatic theory, color opponent theory, inheritance of color vision defect, management of color vision defect
Presented by our respected teacher
Mohammad Siddique (Optometrist)
thank u sir
Final Year Student Of Optometry at ISRA School Of Optometry
All Rights Reserved
A special property of the cone system is color vision.
Perceiving color allows humans (and many other animals) to discriminate objects on the basis of the distribution of the wavelengths of light that they reflect to the eye.
The perception of color is a response to electromagnetic energy at wavelengths between 400 and 700 nm, which is absorbed by cone outer segment visual pigments.
Dogs and horses are only able to sec images in black and white. Give .pdfshahidqamar17
Dogs and horses are only able to sec images in black and white. Give a reason why this might be
the case. Explain the scientific basis for the saying \"All cats are gray in the dark.\" Which
photoreceptors are primarily responsible for dark adaptation? Explain how dark adaptation
works. How does the retina of a person who is red-green color-blind differ from the retina of a
person with normal color vision? Explain why older people complain that their arms seem to be
getting shorter when they pick up something to read.
Solution
4.
5.
The phrase all cats are grey in the dark means that in the dark, physical appearance is
unimportant.
6.
7.
· The retina of the eye has two types of light-sensitive cells called rods and cones. Both are
found in the retina which is the layer at the back of the eye which processes images.
· Rods work in low light conditions to help night vision, but cones work in daylight and are
responsible for colour discrimination.
· There are three types of cone cells and each type has a different sensitivity to light
wavelengths. One type of cone perceives blue light, another perceives green and the third
perceives red. When one looks at an object, light enters the eye and stimulates the cone cells. The
brain then interprets the signals from the cones cells so that one can see the colour of the object.
The red, green and blue cones all work together allowing to see the whole spectrum of colours.
· That colour blindness is usually caused by faulty cones but sometimes by a fault in the
pathway from the cone to the brain.
· People with normal colour vision have all three types of cone/pathway working correctly
but colour blindness occurs when one or more of the cone types are faulty.For example, if the red
cone is faulty you won’t be able to see colours containing red clearly..
The presentation is the continued part of Color Theory section. In this part you can learn about the history of the color, how color theory established & evaluation of color theory, Physiological Principles of color, or Emotional Response of Colors.
Analysis of the Difference between the Normal Vision and the Experiencing Cat...IJERA Editor
The optical instruments design for binocular vision has become an earnest demand towards the arrival of an
ageing society. It is necessary to measure how color difference between left and right images by elderly people,
which the color rivalry occurs. In this study, we measured the limit of binocular color fusion in the normal vision
and the cataract experiencing vision which is aiming to simulate the elderly vision. The result shows that the
color fusion limit curve in cataract experiencing vision are very similar with those in normal vision. Compared
with the binocular color fusion limit in normal vision Δλdn, the binocular color fusion limit in cataract
experiencing vision Δλdc is approximately 3~39nm increased on the central vision, 4~22nm on the retinal
eccentricity of 3°, 5~23nm on the retinal eccentricity of 6°, and 5~24nm on the retinal eccentricity of 9°. The
results also reveal that a similar limit is observed in the range of 520~560nm in both normal and cataract
experiencing visions, which might give some potential evidences for designing 3D equipment. In addition, the
minimum value of the binocular color fusion limit exists at 590nm either in the normal vision or the cataract
experiencing vision during all retinal eccentricities.
Color vision physiology, defects and different testing ProceduresRaju Kaiti
Color vision Physiology, Different types of Color vision defects, different testing procedures, trichromatic theory, color opponent theory, inheritance of color vision defect, management of color vision defect
Presented by our respected teacher
Mohammad Siddique (Optometrist)
thank u sir
Final Year Student Of Optometry at ISRA School Of Optometry
All Rights Reserved
A special property of the cone system is color vision.
Perceiving color allows humans (and many other animals) to discriminate objects on the basis of the distribution of the wavelengths of light that they reflect to the eye.
The perception of color is a response to electromagnetic energy at wavelengths between 400 and 700 nm, which is absorbed by cone outer segment visual pigments.
Dogs and horses are only able to sec images in black and white. Give .pdfshahidqamar17
Dogs and horses are only able to sec images in black and white. Give a reason why this might be
the case. Explain the scientific basis for the saying \"All cats are gray in the dark.\" Which
photoreceptors are primarily responsible for dark adaptation? Explain how dark adaptation
works. How does the retina of a person who is red-green color-blind differ from the retina of a
person with normal color vision? Explain why older people complain that their arms seem to be
getting shorter when they pick up something to read.
Solution
4.
5.
The phrase all cats are grey in the dark means that in the dark, physical appearance is
unimportant.
6.
7.
· The retina of the eye has two types of light-sensitive cells called rods and cones. Both are
found in the retina which is the layer at the back of the eye which processes images.
· Rods work in low light conditions to help night vision, but cones work in daylight and are
responsible for colour discrimination.
· There are three types of cone cells and each type has a different sensitivity to light
wavelengths. One type of cone perceives blue light, another perceives green and the third
perceives red. When one looks at an object, light enters the eye and stimulates the cone cells. The
brain then interprets the signals from the cones cells so that one can see the colour of the object.
The red, green and blue cones all work together allowing to see the whole spectrum of colours.
· That colour blindness is usually caused by faulty cones but sometimes by a fault in the
pathway from the cone to the brain.
· People with normal colour vision have all three types of cone/pathway working correctly
but colour blindness occurs when one or more of the cone types are faulty.For example, if the red
cone is faulty you won’t be able to see colours containing red clearly..
The presentation is the continued part of Color Theory section. In this part you can learn about the history of the color, how color theory established & evaluation of color theory, Physiological Principles of color, or Emotional Response of Colors.
Brief report on using neuropsychological computerized battery to measure the ...inventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
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Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
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Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
Atrioventricular conduction blocks ( AV blocks ) are classified into 3 types.
This document describes the acute management of AV block.
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Are There Any Natural Remedies To Treat Syphilis.pdf
Colour vision performance test
1. Journal of Natural Sciences Research
ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online)
Vol.3, No.11, 2013
www.iiste.org
Colour Vision Performance Test
Stephen Songden* Emeka Ike
Department of Physics, University of Jos, PMB 2084 Jos, Nigeria.
* E-mail of the corresponding author:songdenstephen@gmail.com
Abstract
Colour vision is important in everyday life and colour vision deficiency generally lowers the quality of life. The
objective of the study was to investigate colour vision performance through tests and measurements. The visual
acuity tests were obtained using the Snellen letters while the Colour vision measurements were achieved through
designed colour targets. A total number of 8 participants were tested. The results of the measurements further
confirmed that having good visual acuity is necessary but not sufficient for good colour vision performance.
Keywords: Colour Vision, Visual Acuity, Snellen Letters, Ishihara, Dvorine Colour Test, Performance
1. Introduction
The importance of colour vision cannot be overemphasized and it is hypothesized that colour vision in the visual
system evolved as a means of overcoming the extremely unfavourable lighting conditions in the natural
environment of early vertebrates (Maximov 2000). Colours are the basic information carriers of any natural
scene (Khan et al 1994). Daily life depends on colour to an enormous extent in education, packaging, medicine,
sport, horticulture, transport, and many industrial activities (Fletcher and Voke 1985). Minor frustrations for the
colour abnormal individual include weather forecast (because of the colour coding on the legends), light
emitting diodes, traffic lights, purchasing clothing, bank tellers (normally in triplicate, each for a specified box)
e.t.c. According to Lennie (1984), colour vision has attracted scientific attention for at least 275 years, though it
was not until the nineteenth century that we began to understand it properly. Since then, Scientists have provided
very precise descriptions of the phenomena of colour vision and provided much new information on the
mechanisms of colour vision. The loss of information due to inadequate colour decoding prevents or slows down
comprehension, increases reaction time and generally lowers the quality of life. 8% of men and 0.5% of women
have colour deficiency or colour blindness in the civilized world. It is more prevalent among the whites than
other racial groups (Kilborn and Beh 1934; Shuey 1936) and colour vision tests are necessary for different
professions(Squire et al, 2005). In order for colour to be seen, electromagnetic energy has to reach the eye. An
object is seen when light is reflected from it. If it looks green in daylight, then this must imply that it is only
reflecting the green part of the light back to our eyes. The remainder of the spectrum is absorbed.
With regard to cost-effectiveness, labour planning always opts for the minimum amount of workers needed
Colour vision deficiency is a condition in which certain colours cannot be distinguished, and is mostly due to an
inherited condition. Red-Green colour deficiency (blindness) is by far the most common form, about 99%, and
causes problems in distinguishing reds and greens. Another colour deficiency, Blue-Green also exits, but is rare
and there are no commonly available tests for it. Abnormal colour vision interests a wide range of people,
including the millions who realize that their appreciation of colour is ‘defective’, their families and many more
who are responsible for the dangers and other consequences of their condition, including industrial and
professional implications. The objective of this study was to perform tests and measurements to investigate the
colour vision performance.
2. Theoretical Background
The optics of the eye bear a general resemblance to a camera system, but the way in which the retina image is
processed into a mental image and stored for later use in the memory is almost infinitely complicated. The
human eye’s key features include: a highly-corrected optical design, repeatable geometry of materials, control by
the brain, processing of retina information, interfacing with the brain from six different levels of sensor cells in
the retina, colour vision, compression of data going to the brain, and the highly specific make up and orientation
which enable each eye to function and memory of scenes to take place (Deckert 2008). The visual acuity of the
eye is an important measure of its ability to function well.
2.1 Visual Acuity
Standard visual acuity is defined as the ability to see an object so small that the angle subtended at the eye is
only one minute of arc or one sixtieth of a degree. Visual acuity is also defined as the reciprocal of the visual
angle expressed in minutes of arc. Acuity is said to be normal if details in an object can be resolved with a visual
angle of one minute of arc (Beynon 1985). Many factors affect visual acuity, which could be psychological,
retinal location, target orientation, pupil size, state of mind, photoreceptor size, refractive error, eye movement,
shape, distance, illumination conditions, age, hue, and background (Glezer et al 1974; Levi 1980; Longhurst
1973; Ike and Jwanbot 2002 and Kelton et al 1978). Visual acuity measurements are generally carried out using
19
2. Journal of Natural Sciences Research
ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online)
Vol.3, No.11, 2013
www.iiste.org
the Snellen letters which are the most widely used clinically. This is a primary test normally done to ascertain
whether the person has normal or abnormal visual response. The black targets (Snellen letters) are normally
presented at a standard reading distance of 6 meters. At each acuity level, different Snellen letters are presented
for the subject or participant to identify the letter. Someone with 6/6 vision (visual acuity) is just able to
decipher a letter that subtends a visual angle of 5 minutes of arc (written 5') at the eye. (5' of arc is 5/60 of a
degree, because there are 60' of arc in 1 degree.) What this means is that if you draw a line from the top of a 6/6
letter to the eye and another line from the bottom of the letter to the eye, the size of the angle at the intersection
of these two lines at the eye is 5' of arc. (Also, the individual parts of the letter subtend a visual angle of 1' of arc
at the eye.) It does not matter how far away something is from the eye; if it subtends an angle of 5' of arc at the
eye, then a person with 6/6visual acuity will just be able to determine what it is. Now, someone with 6/6 visual
acuity does not have “perfect” vision, since it is quite possible to see better than 6/6. The less the denominator in
the visual acuity ratio, the better the acuity; and the greater the denominator, the worse the acuity. Therefore, 6/5
acuity is better than 6/6 acuity, and 6/9 acuity is worse than 6/6 acuity. Although 6/6 is "normal" visual acuity
for most people, it is possible (and, in fact, very common) to be able to see better than that.
2.2 Colour Vision Theory
Colour processing begins at a very early level in the visual system (within the retina) through initial color
opponent mechanisms. Opponent mechanisms refer to the opposing colour effect of red-green, blue-yellow, and
light-dark in the X and Y cells of the retina. Visual information is then sent back via the optic nerve to the optic
chiasm: a point where the two optic nerves meet and information from the temporal (contralateral) visual field
crosses to the other side of the brain. After the optic chiasm the visual fiber tracts are referred to as the optic
tracts, which enter the thalamus to synapse at the lateral geniculate nucleus (LGN). There are three categories of
colour vision theory or model; three-components theory, opponent-colour theory and stage theory.
2.2.1 Three Components Theory:
This theory was briefly stated in 1807 by Thomas Young and was elaborated by Helmholtz about 50 years later.
It is also known as the trichromatic theory of colour vision. It assumes the existence of three independent
response mechanisms in the normal eye: one predominantly sensitive to long-wave light and yielding the
response red; a second predominantly sensitive to middle-wave light and yielding the response green; and a third
sensitive to short-wave light and yielding the response violet (Judd, 1966). The theory assumes that yellow is
produced by the sum of red and green responses and that white is produced by the sum of equal amounts of red,
green and violet responses. The theory fails to explain the way some colour stimuli appear to an observer. Colour
vision is possible with two receptor types. However, not all colors can be seen.
2.2.2 Opponent-Colours Theory:
This theory was proposed and explained in detail by E. Hering in 1878. It is based on an analysis of sensations of
colour rather than of the stimuli required to evoke them. It assumes that there are six independent unitary colours
(red, yellow, green, blue, white and black), no one of which partakes of any other; that is for example, yellow is
a basic colour in its own right, not a product of combining red and green. The Hering theory assumes that light is
absorbed in the receptors by photopigments, that this absoption starts activity in the rest of the visual system and
that this activity is directly responsible for the colours we see. This activity is not found in six separate systems,
but in three opposing pairs of processes: black-white, yellow-blue and red-green. Black and white blend to
produce gray but equal amounts of yellow and blue and of red and green cancel to zero (Judd 1966 and
Goldstein 1989). The theory fails to explain certain types of “colour blindness” or deficiencies.
2.2.3 Stage –theory:
This is also called the zone theory of colour vision. According to Fletcher and Voke (1985). The rival theories of
trichromatism and colour opponency competed until the stage theory was introduced principally by Muller,
which incorporated the two views. The stage theory separates colour vision processing into a series of three
stages or zones namely: photopigment stage, cone-response stage and optic-nerve stage. Signals resulting from
the reception of light by the photoreceptors are modified at each successive zone often associated with a
physiological level. The photopigment stage follows the three components theory based on the Young primaries.
The cone-response stage follows an opponent-colours form and the optic-nerve stage is the opponent-colours
formulation of Hering with red opposing green and blue opposing yellow. The two-stage theory is based on the
retinal photopigment stage and the cone-response stage. There has been a considerable uncertainty as to
precisely at what stage of the visual process the signals from the receptors can be said to be organized in
opponent colours, whether this is in the retina, the optic nerve, or the occipital lobe of the cortex (Judd 1966).
3. Materials And Method
The investigations were carried out in two parts: Visual Acuity Measurements (Songden and Ike 2004; Beynon
1985) and Colour arrangement Test. All sessions were done under normal natural lighting room condition,
which was good for near and distance acuity measurements. All subjects on glasses were tested without their
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glasses on to avoid any effect of such on the measurements. Since the focus of the work is on the colour
performance, details of the visual acuity measurements are described in an earlier paper (Songden and Ike 2010).
3.1 Visual Acuity Measurements
Visual acuity measurements of the participants were carried out using the Snellen letters. The black targets were
designed on the computer following established method (Songden and Ike 2004; Beynon 1985) and presented
using power point on the computer screen. The standard reading distance of 6 meters was used. This was carried
ower
out in a spacious room in the Physics Laboratory of the University of Jos. At each acuity level, the different
Snellen letters were presented one at a time.
3.2 Colour Arrangement Test
Another test given to the participants was that of arranging different colour targets into colour groups according
to their saturation. The targets were squares of dimensions 1.27 cm each and a total of 42 of them random
randomly
scattered. They were designed using microsoft power point and each participant was told to group same or
similar colour targets and then arrange them according to their saturation in decreasing order. They were not told
the number of colour groups.
4. Results
Figure 1 and Table 1 show the results of the arrangements of the 8 participants. Figure 1(a) was the target
designed and presented on power point for the arrangement according to the colour groups and saturation. Figure
1(b) was arranged by participant A, who missed two targets (interchanged the first two) in the red group. Figure
pant
1(c) was arranged by participant B who got everything correctly and this was the case for C, D and H. Figure 1(d)
was arranged by participant E who missed two targets (interchanged the first two) in the blue group. Figure 1(e)
(interchanged
was arranged by participant F who missed thirty seven targets and figure 1(f) was by participant G who missed
thirty three targets.
(a)
(b)
(b)
(d)
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(e)
(f)
Figure 1: Colour Arrangements by the Participants. Where (a) was the target presented for arrangement,(b) was
arranged by A, (c) by B,C,D &H, (d) by E, (e) by F and (f) by G.
d)
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Table 1: Results of Colour Arrangement.
Age(yrs)
VA
Missed
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
A
35
6/5
2
1
2
3
4
5
6
8
7
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
B
22
6/5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
38
37
39
40
41
42
C
42
6/6
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
D
40
6/6
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
E
43
6/6
2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
26
25
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
F
25
6/6
37
1
2
3
4
5
21
11
6
23
36
7
8
9
19
20
10
39
41
40
42
37
38
13
14
15
16
18
17
26
34
28
29
22
12
30
31
25
32
33
27
35
24
G
41
6/5
33
1
2
3
5
4
6
7
8
19
10
9
21
37
13
14
15
16
17
18
11
12
42
22
23
24
20
40
39
38
41
31
32
25
33
26
34
27
28
35
29
36
30
H
38
6/6
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
5. Discussion And Conclusion
The results obtained indicated all the participants having good visual acuity. Four of the participants (B,C,D & H)
arranged all the targets correctly. Participant A missed 2 only, which are the first two targets of the red group.
This is not a serious problem and therefore negligible. The case of participant E is similar to that of A, missing
only 2, in the blue group. Again this is negligible and not an indication of a colour deficiency. However, this is
not the case with the participants F and G whose arrangements were clear indication of colour vision deficiencies.
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6. Journal of Natural Sciences Research
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Vol.3, No.11, 2013
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This is a confirmation that having a good visual acuity is necessary but not sufficient for good colour vision. The
participant F mixed up red and green and was able to group all the yellow targets though not all in the order of
saturation. Participant G was also able to arrange all the yellow targets in one group and in the right order of
saturation but grouped all the blue and purple targets together. The colour deficiencies of the two participants are
closely related though that of F is worse. These results also confirmed those obtained in an earlier study
(Songden and Ike 2010) using the Ishihara (1995) and Dvorine (1963) test plates and that colour targets
arrangements could be used in colour vision determination.
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24
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