OPB201 Summary

Foundations of Optometric Practice

Learning Outcomes

After completing this topic, students should understand:

1. Optometry’s role in Australia’s health system and team-based healthcare.

2. The scope of optometric practice.

3. Professional identity within optometry.

4. What it means to be a reflective practitioner.

Health and Eye Health Discussion

• Reflect on your beliefs about health and eye health.

• Share influences shaping your beliefs about eye health.

Concepts of Health

What is Health?

• Various definitions:

  • Oxford Dictionary: Free from illness or injury.

  • WHO: Complete physical, mental, and social well-being.

  • Australian Gov't: Highest attainable standard of health is a fundamental human right.

Influences on Health

• A range of factors including socioeconomic characteristics, culture, education, and individual behaviors.

• Important determinants: tobacco use, diet, physical activity, access to services, etc.

Eye Health

Influences on Eye Health

Factors affecting eye health include:

• Genetics

• Age

• Diet (e.g., omega-3 fatty acids, vitamins A, C, E)

• Environmental factors

• Trauma

Eye Care Definition

• Prevention and treatment of conditions that threaten eye integrity.

• Primary eye care is essential in primary health care contexts.

Eye Health in Australia

National Eye Health Survey 2016

• Conducted to assess vision impairment and blindness prevalence.

• Over 453,000 Australians impacted by vision impairment or blindness.

• Main causes include uncorrected refractive error and cataracts.

Eye Health Services

• Australia has comprehensive eye health services and highly qualified specialists.

• Responsibility for eye health programs distributed across sectors.

Role and Scope of Optometry

Optometry in Healthcare

• Involves prescription of spectacles, contact lens fitting, and diagnosis of eye diseases.

• Optometrists are primary health care specialists.

Team-based Approach

• Optometrists work alongside dispensers, reception staff, and other health professionals.

• Emphasis on inter-professional practice to improve patient outcomes.

Reflective Practice

Being a Reflective Practitioner

• Reflective practice involves:

  1. Learning from experiences.

  2. Thinking critically about professional practice.

• Utilize the 4R model: Reporting, Relating, Reasoning, Reconstructing.

Key Employability Skills

• Skills necessary for professional effectiveness include:

  • Communication

  • Teamwork

  • Problem-solving

  • Initiative

  • Self-management

  • Technology adaptability.

Online Activities

• Required activities include mental health awareness and teamwork skills development.

• Focus on positive experiences in team assignments.

What is Health Information?

• Critical tool for decision making in health.

• In Optometry: Collecting patient information, making diagnoses, guiding treatment decisions.

Types of Health Information

• Symptoms, diagnoses, treatments

• Specialist reports, test results

• Appointment and billing details

• Prescriptions and pharmaceutical records

• Genetic, dental records, other personal information (race, sexuality)

Importance of Health Information

• Drives healthcare delivery

• Informs better health decisions

• Facilitates effective treatment based on evidence.

My Health Record

• Nationwide scheme in Australia, default enrollment unless opted out.

• Secure online summary of key health information.

• Accessible to healthcare providers, improving healthcare efficiency.

• Allows tracking over time, especially during crises.

Dimensions of Health Information

1. Patient Dimension: Information derived from patients.

2. Professional Dimension: Supports evidence-based clinical decisions.

3. Management Dimension: Administrative information for health service managers.

Evidence-Based Practice (EBP)

• Integration of clinical expertise, patient values, and best available evidence from research.

• Importance: Better patient outcomes through research-based treatments.

EBP Process

1. Ask: Formulate clinical questions.

2. Acquire: Search research literature for answers.

3. Appraise: Evaluate quality of evidence.

4. Apply: Implement findings in patient care.

5. Audit: Assess the use of evidence in practice.

PICO Framework

• Helps formulate clinical questions:

  • Patient/Problem

  • Intervention

  • Comparison/Control

  • Outcome

Types of Research

• Ranges from opinion-based guidelines to systematic reviews.

• Stronger evidence includes Randomised Controlled Trials (RCTs), systematic reviews.

Literature Review

• Critical analysis of existing research on a topic.

• Identifies gaps, strengths, and weaknesses within literature.

Systematic Review

• Addresses specific research questions using predefined criteria.

• Involves summarising and critiquing research findings.

Core Competencies for Health Professionals

• Be able to:

  • Critically appraise various types of studies.

  • Recognise limitations and biases in studies.

  • Engage in patient-centered care through shared decision-making.

Clinical Guidelines

• Developed using high-quality research evidence to aid decision-making in clinical practice.

• Important for standardized patient care across various conditions and procedures.

Cultural Safety and Communication

Acknowledgement of Traditional Owners

• QUT acknowledges Turrbal and Yugara as First Nations owners of the lands.

• Recognition of Elders, customs, and the role of Aboriginal and Torres Strait Islander peoples at QUT.

Assessment Task

• Mid-Semester Assessment: 30% of unit.

  • Divided into two parts (15% each):

    • Part 1: MCQs and short answer questions on Cultural Safety and Communication.

    • Part 2: Extended answer essay detailing culturally safe health care in a case scenario.

• Assessment emphasizes effective communication and referencing course content.

Cultural Safety

• Developed by Māori nurse Irihapeti Ramsden in Aotearoa/New Zealand.

• Focuses on the health provider's role and the impact of personal and organizational culture on patient care.

• Governed by new codes of conduct from Ahpra and other organizations effective June 29, 2022.

Key Principles of Cultural Safety

• Self-awareness: Understand personal culture and biases.

• Power Relationships: Identify dynamics in health care settings.

• Decolonization: Acknowledge history and effects of colonization.

• Patient Experience: Culturally safe care is determined by the patient's experience, not the provider's definition.

• Ahpra's Definition: Focus on culturally safe health care, free of racism, informed by Indigenous communities' perspectives.

Importance of Communication

• Good Communication: Essential for effective patient education and care delivery.

• Communication Models:

  • Simple model (Sender, Message, Receiver).

  • Expanded model includes context, channels, feedback, and noise.

Barriers to Effective Communication

• Various barriers may hinder communication, including language, environmental factors, and biases.

Building Rapport

• Rapport: Establishing a good relationship with patients is critical for effective care.

  • Characteristics include respect, concern, understanding, trust, empathy, sensitivity, and sincerity.

• Patients are more likely to change providers due to poor rapport than clinical incompetence.

Listening Skills

• Active Listening: Requires integration of verbal and nonverbal cues, demonstrating empathy.

• Poor listening can stem from bias, concentration issues, or assumptions.

Nonverbal Communication

• Involves cues such as body language, paralanguage, personal space, and professional appearance, all impacting patient perceptions and trust.

Ethical Practice in Optometry

Academic Honesty and Plagiarism

• Definition of Academic Honesty:

  • Academic honesty is the commitment to producing original and authentic work.

  • It involves completing coursework with only the assistance allowed by the institution's guidelines.

• QUT Policies on Academic Honesty:

  • The university has specific policies outlined in the Manual of Policies and Procedures (MOPP).

  • MOPP emphasizes the significance of academic integrity, ethical assessment, and maintaining high academic standards.

Importance of Integrity and Misconduct

• Benefits of Integrity:

  • Development of professional capabilities and reputation.

  • Encourages a culture of ethical practice in academic settings.

• Types of Academic Misconduct:

  • Cheating: Seeking unfair advantages in exams.

  • Plagiarism: Copying someone else’s work or submitting your own work again as if it were new (self-plagiarism).

  • Contract Cheating: Outsourcing your work to others for completion.

  • Collusion: Collaborating with others on an assignment without permission.

Understanding Plagiarism

• Definition of Plagiarism:

  • Plagiarism is defined as representing another's ideas or expressions as your own. This includes:

    • Direct copying or summarizing without acknowledgment.

    • Using another's ideas or research results without proper credit.

• Common Forms of Plagiarism:

  • Copied diagrams, plans, or any non-textual material without attribution.

  • Reusing elements of previous work without acknowledgment.

Case Studies in Plagiarism

• Case Study 1:

  • Jack and Jill create a rough draft together.

  • Jack, unable to complete his own work, slightly alters Jill's work and submits it.

• Case Study 2:

  • Group lab work leads to individual reports.

  • Weng creates graphs but other group members submit them without acknowledgment.

• Case Study 3:

  • Mary finds uncredited information online and assumes it's free to use without citation.

Tips for Avoiding Plagiarism

• Planning and Note-taking:

  • Manage time effectively and familiarize yourself with the material.

  • Take concise notes instead of copying directly.

• Citing and Referencing:

  • Keep a running bibliography.

  • Use quotation marks for exact phrases and reference non-common knowledge.

Professional Ethics in Optometry

Definition of Ethics

• Understanding Ethics:

  • Ethics delineates the standards of right and wrong, emphasizing rights, obligations, and fairness.

  • Professional ethics is a code of conduct adopted by various professions.

Optometry Professional Ethics

• Hippocratic Oath Principles:

  1. Beneficence: Striving to do good for each patient.

  2. Non-maleficence: Avoiding harm; weighing risks and benefits.

  3. Respect for Autonomy: Honoring patients' choices about their health.

  4. Justice: Fair treatment of all patients regarding resources and time.

Regulatory Framework

• Ahpra & National Boards Code of Conduct (June 2022):

  • Establishes ethical guidelines for Health Practitioners in various domains, including optometry.

Patient Rights Charter

Core Rights of Patients

• Right to Respect and Care:

  • Patients should be treated respectfully and without exploitation in safe environments.

• Informed Decisions:

  • Patients have the right to clear information on their condition and treatment options.

• Confidentiality:

  • Assurance of privacy in all care-related matters.

• Right to Complain:

  • Patients can voice grievances and seek resolution for any dissatisfaction.

Introductory Ocular Anatomy and Physiology

Instructor Information

• AProf Katrina Schmid

• Email: k.schmid@qut.edu.au

• Suggested Reference: Lee Ann Remington, Clinical Anatomy of the Visual System (2012) - ebook available.

Module Overview

• Aim: To introduce foundational knowledge in ocular anatomy and physiology.

• Learning Outcomes:

  • Understand basic ocular anatomy of the eye.

  • Identify key structures and comprehend main physiological processes.

  • Begin to understand how structural abnormalities precipitate eye disease.

Lecture 1 Summary

• Topics Covered:

  • Terminology and Definitions (Anatomy, Ocular Anatomy, Physiology, Ocular Physiology)

  • Gross Anatomy of the Eye (Visible structures)

  • Comparison to a Camera

  • Refractive Errors

  • External and Internal Ocular Structures

Terminology and Definitions

• Anatomy: Identification and description of structures.

• Ocular Anatomy: Identification and description of eye structures.

• Physiology: Processes involved in how the body functions.

• Ocular Physiology: Specific to the functioning of the eyes.

• Inner vs Outer: Terms describing locations within the eye.

Abbreviations in Optometry

• Acronyms play a critical role in optometry. Examples include:

  • AC: Anterior Chamber

  • ACD: Anterior Chamber Depth

  • BCVA: Best Corrected Visual Acuity

  • IOP: Intraocular Pressure

• Numerous abbreviations exist beyond those listed here.

Basic Ocular Structure

• The eye is vital for vision and is a unique organ.

• The retina develops from the brain and is specialized for vision.

• Ocular components are critical for focusing light and forming images on the retina.

How the Eye Works

• The eye functions analogously to a camera, utilizing components such as:

  • Diaphragm (Iris): Controls light entry.

  • Lens: Focuses light onto the retina.

  • Retina: Receives the image and transmits signals to the brain.

Eyeball Anatomy

• Shape & Size:

  • The adult eyeball is approximately 24mm in diameter.

  • Eye size influences refractive state (Emmetropia, Myopia, Hyperopia).

• Myopia: Light focuses in front of the retina, affecting distant vision.

• Hyperopia: Light focuses behind the retina, affecting near vision.

• Astigmatism: Causes blurred vision due to uneven curvature of the cornea.

Eye Structure in Cross Section

• Key components include:

  • Zonular Fibres, Iris, Pupil, Lens, Cornea, Retina, Fovea, Optic Nerve, Sclera, Choroid, Ciliary Body, Vitreous Chamber, Anterior Chamber.

Layers of the Eye

1. Outer Fibrous Layer: Cornea and Sclera.

2. Middle Vascular Layer: Uveal tract (Iris, Ciliary Body, Choroid).

3. Inner Neural Layer: Retina.

Eye Protective Mechanisms

• Protective components:

  • Eyebrows and Eyelids (superior and inferior).

  • Bony orbit and surrounding soft tissue.

• Importance: Protection from environmental damage.

External Ocular Structures

• Eyebrow: Helps in dust protection.

• Eyelids: Spread tears and provide protection.

• Eyelashes: Trap debris.

• Palpebral Fissure: Space between open eyelids.

Lacrimal System

• Responsible for tear production and drainage:

  • Lacrimal Gland: Produces tears.

  • Drainage via nasolacrimal system into the nose.

Tear Film

• Functions:

  • Lubricates the cornea.

  • Provides nutrients and antimicrobial factors.

  • Composed of lipid, aqueous, and mucin layers.

Specific Eye Structures

• Cornea: Outer layer, transparent, provides optical power.

• Sclera: Opaque, tough outer coat; protects eye contents.

• Conjunctiva: Mucous membrane; aids lubrication and immunity.

Anterior Chamber

• Space between cornea and lens filled with aqueous humor.

• Supplies nutrients and oxygen to cornea and lens.

Crystalline Lens

• Biconvex, transparent; aids in accommodation for focusing.

Vitreous Chamber

• Space filled with vitreous humor, helps maintain eye shape.

Uveal Tract

• Consists of the pigmented, vascular layers (Iris, Ciliary Body, Choroid).

Retina Structure

• Multi-layered, light-sensitive tissue responsible for phototransduction.

• Contains photoreceptors (Cones and Rods) that send visual signals.

Phototransduction

• Process of converting light energy into electrical signals in the eye.

Optic Nerve

• Carries visual signals from the retina to the brain; origin of the "blind spot" due to absence of photoreceptors.

Lecture Topics

• Visual Pathway

• Eye Movements

• Ocular Transparency

• Oxygen and Blood Supply

• Intraocular Pressure

• Effect of Aging

Visual Pathway

Definition

• The visual pathway transmits visual sensations from the retina to the brain.

Process

1. Light absorbed by photoreceptor cells.

2. Impulse travels through retinal layers.

3. Information is sent via optic nerve.

Pathway Details

• Pathway sequence:

  • Retina

  • Optic nerve

  • Optic chiasma

  • Optic tracts

  • Lateral geniculate nucleus

  • Optic radiations

  • Primary visual cortex

Signal Processing

• At Lateral Geniculate Body (LGB) and visual cortex, information is modified before reaching perception.

Visual Field Defects

Types of Defects

• Central Scotoma: Damage in the retina affecting central vision.

• Monocular Vision Loss: Loss in one eye due to optic nerve damage.

• Bitemporal Hemianopia: Loss of lateral vision due to optic chiasma involvement.

• Contralateral Homonymous Hemianopia: Loss of the same side visual field in both eyes due to optic tract damage.

Visual Field Testing

• Screening Tests: Includes Amsler grid and confrontation tests.

• Threshold Testing: Automated perimetry.

Eye Movements

Mechanism

• Extraocular Muscles: Six muscles provide control over eye movements.

Types of Eye Movements

• Ductions: Monocular eye movements.

  • Abduction(lateral) and Adduction(medial).

  • Supraduction (upward) and Infraduction (downward).

  • Rotation: Incycloduction (intorsion) and Excycloduction (extorsion).

Types of Binocular Movements (Versions)

• Dextroversion: Both eyes turn right

• Laevoversion: Both eyes turn left

• Supraversion: Eyes look up

• Infraversion: Eyes look down

Vergence Movements

• Convergence: Both eyes move inward

• Divergence: Both eyes move outward

Ocular Transparency

Transparent Structures in the Eye

• Types:

  • Cornea

  • Aqueous humour

  • Lens

  • Vitreous humour

  • Inner retina

Transparency Maintenance

• Achieved by lack of blood vessels, nerve fibers, and structured arrangement of components.

Specific Structures and Transparency Mechanisms

• Cornea: Collagen fibrils arrangement.

• Aqueous: Blood-aqueous barrier prevents large molecular entry.

• Lens: Lack of blood vessels and regulated fiber arrangement.

• Vitreous: Collagen matrix helps in maintaining transparency.

Aging and Eye Health

Age-Related Changes

• Decreased blood flow and tear quality.

• Lens becomes larger and clarity reduces leading to presbyopia.

• Vitreous liquefaction affecting vision.

Common Eye Diseases With Age

• Increased prevalence of refractive errors, cataracts, age-related maculopathy, glaucoma, diabetic retinopathy, and dry eye.

Activities to Enhance Learning

• Blind Spot Demonstration: Observe the blind spot of the eye.

• Blood Vessel Patterns: Light test to see retinal blood vessels.

• Eye Movement Simulation: Use simulators to see impacts of muscle palsy.

• Create EOM Model: Hands-on activity to understand extraocular muscle functions.

• Utilize Anatomy TV Database: Explore 3D eye anatomy for interactive learning.

Introduction to Ophthalmic and Visual Optics

• Instructor: Professor David AtchisonEmail: d.atchison@qut.edu.au

• Reference Books:

  • Jalie M (2021). Principles of ophthalmic lenses, 6th ed., Association of Dispensing Opticians.

  • Atchison DA, Smith G (2000). Optics of the human eye, Butterworth-Heinemann.

• Module Overview:

  • Focus on foundation knowledge in ophthalmic optics and visual optics: lenses, prisms, and image formation in the eye.

• Learning Outcomes:

  • Understand lenses and prisms, ocular components, and image formation in the eye.

Lecture 1: Ophthalmic Optics – Lenses and Prisms

Definition of Ophthalmic Optics

• Application of optics to the field of vision,

  • Includes the eye's optics and corrective devices.

• Focus on the corrective devices aspect.

• Relation to refractive anomalies and correcting lenses in visual optics section.

Key Topics Covered

• Sign Conventions:

  • Light travels from left to right.

  • Object/image distances, focal lengths, and radii of curvature are measured from optical surfaces.

  • Distances in the direction of light are positive.

• Units:

  • Basic metric unit is metre (m).

  • Derived units include lens power in dioptres (D) and prism power in prism dioptres.

Lenses

• Equations for Lenses:

  1. Surface Power:

     • F = (n' – n)/r

  2. Refraction Equations:

     • L = n/l

     • L' = n'/l'

     • n'/l' – n/l = F

     • L' – L = F

• Example Problems:

  • Applications of the above equations demonstrated through examples with calculated surface powers and distances.

• Types of Lenses:

  • Spherical (spherical and astigmatic lenses).

  • Positive (thickest in the middle) vs Negative (thinnest in the middle).

Prisms

• Introduction to Prisms:

  • Solid pieces of glass or plastic with two plane surfaces inclined at an angle.

• Prism Characteristics:

  • Prism angle, deviation, and power defined with equations.

  • Use in correcting ocular muscle defects.

Lecture 2: Visual Optics – Biometry and Refractive Anomalies

Definition of Visual Optics

• Examines how the optics of the eye interact with physiological processes and affect visual performance.

• Overlap with ophthalmic optics, including the positioning of the eye's optical components.

Optical Elements of the Eye

• Components:

  • Tear film, cornea, anterior chamber, iris, lens, vitreous chamber, optic nerve.

• Detailed characteristics of each component:

  • Cornea: Mean power ~ +43 D, anterior and posterior radii of curvature, aspheric nature.

  • Lens: Maintains power through shape and gradient index; power changes with accommodation.

• Refraction in Eyes: Types of ametropia explained:

  • Myopia (shortsightedness), hyperopia (farsightedness), and astigmatism.

Addressing Refractive Anomalies

• Myopic and hyperopic corrections through appropriate lenses.

• Addressing presbyopia with positive lenses.

• Explanation of astigmatic corrections using different powers for principal meridians.

Relevant Equations to Note

• Surface Power: F = (n' – n)/r

• Refraction: L = n/l , L' = n'/l', n'/l' – n/l = F

• Prism Power: P = 100 tan(d)

• Deviation Relation: d = (n – 1)a

• Effectivity/Transfer: L+ = L/(1 – (d/n)L]

Practical Applications

• Assignments:

  • Students are tasked with solving complex optics problems to reinforce understanding.

  • Example problems offer scenarios such as lens measurements, refractive index calculations, and neutralization techniques.

Introduction to Visual Science

• Instructor: Professor Joanne Wood

• Dept: Optometry & Vision Science, Centre for Vision and Eye Research

• Contact: j.wood@qut.edu.au; Ph: 3138 5701

Course Overview

• Module covers the fundamental principles of vision:

  • Visible light

  • Duplex retina characteristics (rods vs. cones)

  • Eye's response to light and visual stimulation

  • Dark and light adaptation

  • Spatial vision (visual acuity & contrast sensitivity)

  • Motion sensitivity

  • Perceptual constancies

  • Binocular and colour vision

Introduction: Visible Light

• Definition: Light as electromagnetic radiation (wave/photons)

• Wavelength Range: Human visible light: 400-700 nm

  • Colour Spectrum: violet (400 nm) to red (700 nm)

• Nature of Light: Light waves are not coloured; perception arises from visual system interpretation.

Properties of Light

• White Light: Mixture of visible wavelengths

• Light Interaction:

  • Absorption: E.g., absorbing dust and water vapor

  • Reflection: Light-coloured surfaces reflect, dark-coloured absorb

  • Transmission: Light passing through surfaces

  • Refraction: Light bending when passing through materials (e.g., glass)

Ocular Structures and Functions

• Key Structures: Cornea, pupil, retina, lens, photoreceptors (rods & cones), optic nerve, macula.

• Light Interaction in the Eye: Reflection, absorption, scattering, transmission, refraction.

Light Absorption by Ocular Media

• Aging Effects:

  • Lens yellows with age, reducing transmission of shorter wavelengths

  • Macular pigment and blood vessels absorb shorter wavelengths.

Visual Pathways

• Pathway from retina to:

  • Optic nerve → Optic chiasm → Optic tracts → LGN → Visual cortex

• Projection: Visual information is upside down and laterally reversed on the retina.

Duplex Retina

• Photoreceptors: Two types, rods (for low light) and cones (for bright light).

  • Operational Range: ~10 log units of light levels

• Retinal Types:

  • Photopic: Cones (daylight vision)

  • Mesopic: Combination of both

  • Scotopic: Rods (night vision)

Differences between Rods and Cones

• Visual Systems:

  • Scotopic (rods): High sensitivity, poor resolution

  • Photopic (cones): Poor sensitivity, excellent resolution

• Key Characteristics Table:

  • Receptor Types: Rods vs. Cones

  • Morphology: Free-floating vs. discs attached to membranes

  • Sensitivity & resolution metrics (Weber’s fraction).

Rod Vision Characteristics

• Distribution: ~120 million, absent at fovea.

• Function: Scotopic vision, high sensitivity, colorblind.

• Response Rate: Slower, detects dim lights through linking across retina.

Cone Vision Characteristics

• Distribution: ~6 million, packed at fovea

• Function: Photopic vision, quicker response, ability for color perception.

• Types of Cones: Three (differing peak sensitivities).

Visual Photopigments

• Composition: Rods contain rhodopsin; cones have three pigments with distinct spectral sensitivity.

• Chromophore: Retinal derived from Vitamin A, essential for color vision.

Dark Adaptation (DA)

• Concept: Slow recovery of sensitivity in reduced light, divided into two phases:

  • First Phase: 5-10 mins, rapid cone adaptation.

  • Second Phase: 10-45 mins, rod adaptation.

• Effects of Aging: DA reduces with age and certain diseases.

Visual Acuity and Contrast Sensitivity

• Visual Acuity: Ability to resolve fine details; measured using standard charts (Snellen & logMAR).

• Contrast Sensitivity: Alternative approach assessing spatial vision using sine wave gratings, sensitive to spatial frequency changes.

Factors Affecting Visual Functions

• Visual Acuity Factors: Optical blur, luminance, retinal eccentricity, age.

• Contrast Sensitivity Factors: Age, luminance, and retinal eccentricity.

Measurement Methods

• Visual Acuity Measurement: Snellen and logMAR charts

• Contrast Sensitivity Functions: Generated via sine wave gratings for varying spatial frequencies.

Motion Perception

• Definition: Ability to detect moving targets.

• Importance:

  • Navigation and survival.

  • Provides basic contextual information:

    • Attracting attention.

    • Understanding 3D form.

    • Figure and ground perception (camouflage effects).

    • Interaction with environment during activities such as walking and driving.

Types of Motion

• Real Motion: Physical movement of an object.

• Apparent Motion: Perceived when objects are presented sequentially and separated in space.

• Induced Motion: Perceived motion of a stationary object due to surrounding movements.

• Autokinetic Effects: Illusions of motion in stationary objects in a dark environment.

• Movement After-effects: Illusory motion after adaptation to actual motion.

Biological Motion

• Definition: The ability of the visual system to recognize motion of living creatures from minimal input.

  • Patterns of motion for living creatures differ from inanimate objects.

  • Related concepts:

    • Shapes or types of biological motion can reflect gender and emotions (e.g., heavy/light, nervous/relaxed).

Perceptual Constancies

• Definition: Perception that object properties (e.g., color, size, shape) remain stable despite changes in visual conditions.

  • Types:

    • Lightness Constancy: Perceived reflectance remains constant regardless of illumination.

    • Shape Constancy: Shape perception is stable despite varying viewpoints, dependent on depth information.

    • Size Constancy: Physical size appears consistent despite changes in distance.

Visual Illusions

• Definition: Instances where perception diverges from actual stimuli.

• Often arise from breakdowns of size and shape constancies.

• Common Examples:

  • Moon Illusion: Moon appears larger on the horizon than at zenith but is actually the same size.

  • Ames Room: People of equal height appear different due to distorted room geometry.

  • Müller-Lyer Illusion: Lines of the same angle appear different in length.

Binocular Vision

• Definition: Utilization of both eyes to create a cohesive image of the visual world.

• Advantages:

  • Enhanced depth perception and larger visual fields.

  • Redundant visual input in cases of injury or disease.

Process of Seeing in Depth

• Stereopsis: Depth perception arising from the slight differences in images received by each eye due to eye separation.

• Requirements for Effective Binocular Vision:

  • Two eyes with separation and overlapping fields.

  • Ability to merge images from both eyes into one percept.

• Motor Alignment Capacity: Refers to accurate eye movements in response to retinal disparities.

Corresponding Retinal Points & Retinal Disparity

• Corresponding Points: Points in each eye that correspond visually, leading to image fusion.

• Retinal Disparity: Small differences between eye images contribute to depth perception,

  • Types:

    • Crossed disparity: Sensation of nearness.

    • Uncrossed disparity: Sensation of farness.

    • Too much disparity can lead to double vision.

Physiological Diplopia

• Occurs when objects fall on non-corresponding retinal points, causing a double vision effect, typically felt in peripheral vision.

• Example demonstration of crossed vs. uncrossed diplopia by focusing on distant vs. near objects.

Binocular Vision Testing

• Various assessments for binocular vision:

  • TNO random dot stereograms using colored glasses.

  • Randot stereo tests utilizing polarized light.

Colour Vision

• Definition: Related to light properties and the interaction with observer perception.

• Light Sources:

  • Natural sources emit a broad range of wavelengths, while artificial sources may have narrow spectrums.

• Surface Reflectance: The perceived color is dependent on both light wavelengths that reach and reflect off of surfaces.

Colour Mixing

• Additive Colour Mixing: Combining different lights (RGB) creates new colors.

• Subtractive Colour Mixing: Mixing pigments (CMY) results in colors based on absorption properties of pigments.

• Example: Mixing red and green may result in varying hues based on absorption.

Summary: Additive and Subtractive Colour Mixing

• Human colour vision operates as a trichromatic system (three cone types - S,M,L).

Current Colour Vision Theory

• Colour perception is influenced by the integration of cone types into color-opponent pathways within the visual system.

Colour Vision Defects

• Congenital defects often involve missing or altered cone pigments, affecting color perception.

  • Types:

    • Dichromats: Absence of one cone type.

    • Protanopia, Deuteranopia, Tritanopia: Specific cone deficiencies leading to impaired color resolution.

Colour Vision Testing Techniques

• Tests:

  • Pseudoisochromatic plates (Ishihara).

  • Hue discrimination tests (D-15).