Weight & Thickness of Lenses Identify the plus and minus lenses Plus lenses are thickest in the centre and get thinner towards the edge Minus lenses are.

Slides:



Advertisements
Similar presentations
Introduction to Refractive Error and Prescription Writing Walter Huang, OD Yuanpei University Department of Optometry.
Advertisements

Theme 8: Astigmatism Concept of Astigmatism Formation of the retinal image Quantifying Astigmatism Classifying Astigmatism Retinal Image of the astigmatic.
L 31 Light and Optics-3 Images formed by mirrors
Visual Considerations for children with Down syndrome and Cerebral Palsy Julie-Anne Little VIEW conference, March 2013 Julie-Anne Little PhD MCOptom
Characteristics of Lenses Lens  Is a transparent object with at least one curved side that causes light to refract.  Have 2 sides  Either side could.
LENSES. LENSES A light ray bends as it enters glass and bends again as it leaves ◦This refraction is due to the difference in the average speed of light.
ARAVIND EYE CARE SYSTEM A R A V I N D E Y E H O S P I T A L & Postgraduate Institute of Ophthalmology Madurai, India ARAVIND EYE CARE SYSTEM A R A V I.
Chapter 23 Mirrors and Lenses.
Chapter 23 Mirrors and Lenses Conceptual questions: 4,5,10,14,15,17
Content Standard 5 – Contrast ways in which light rays are bent by concave and convex lenses.
Chapter 23 Mirrors and Lenses. Notation for Mirrors and Lenses The object distance is the distance from the object to the mirror or lens Denoted by p.
Physiological optics 9 th lecture Dr. Mohammad Shehadeh.
Chapter 23 Mirrors and Lenses.
Lecture 23 Mirrors Lens.
2 nd & 3 th N.U.T.S. Workshops Gulu University Naples FEDERICO II University 3 – Imaging (thin lenses and spherical mirrors)
Image Formation 2 Thin Lens Multi lens/mirror system
L 33 Light and Optics [3] images formed by mirrors
Types of Lenses If you have ever used a microscope, telescope, binoculars, or a camera, you have worked with one or more lenses. A lens is a curved transparent.
Optical Theory II ABERRATIONS Copyright Ellen Stoner, MALS, ABOM, NCLC.
 Gradually increase in power ◦ Upper portion = distance power ◦ Downward & inward = near power ◦ Inbetween is a progressive corridor where the lens power.
Homework Set 5: Due Wednesday, March, 17 From Chapter 5: P2, P8, P10, P11, From Chapter 6: P1, P2, P6, PM2,
Chapter 23 Mirrors and Lenses.
Rigid lens verification and evaluation
L 33 Light and Optics [3] images formed by mirrors –plane mirrors –curved mirrors Concave (converging) Convex (diverging) Images formed by lenses the human.
 Get out notes and practice from yesterday  Pick up ruler and finish practice from yesterday.
Refraction (bending light) Refraction is when light bends as it passes from one medium into another. When light traveling through air passes into the glass.
Walter Huang, OD Yuanpei University Department of Optometry
L 33 Light and Optics [3] Measurements of the speed of light  The bending of light – refraction  Total internal reflection  Dispersion Dispersion 
Refraction through a lens. we have seen people using spectacles for reading. The watchmakers use a small glass to see tiny parts. Pistol or rifle shooters.
WELCOME TO VIEW OUR PROJECT ON DEFECTS OF HUMAN EYE DUE TO LIGHT.
Refraction and Lens. Refraction Refraction: the change in direction of a wave as it crosses the boundary b/w 2 media in which a wave travels different.
CHAPTER - 15 LIGHT.
PRCTICAL DIFFICULTIES OF PROGRESSIVE LENS FITTING
Refractive Errors & methods of correction M. F. Al Fayez, MD, FRCS.
Optometry practices can be in various locations  Shopping centres  Medical centres  Individual buildings  People’s homes (domicillary)
OBJECTIVE IDENTIFY TYPES OF CORRECTIVE LENSES USED TO CORRECT SIGHT PROBLEMS [COS 5, SAT 10]
Notes on Chapter 30 Lenses
Lenses Chapter 30.
Chapter 34. Images What is Physics? Two Types of Image
 What is refraction?  Refraction is the bending of a light when it enters a medium where the speed of light is different. When a light ray passes from.
The Eye 5.SEEING LIGHT - THE EYE Cornea -does most of the focusing Iris - Pupil - has the eye color and controls light intensity Lens - the hole in.
Chapter 18 Mirrors and Lenses Lenses A. Types of Lenses A. Types of Lenses B. Convex Lenses B. Convex Lenses C. Concave Lenses C. Concave Lenses.
Chapter 23 Mirrors and Lenses.
Acceleration: Sinusoidal E/M field Sinusoidal Electromagnetic Radiation.
Chapter 34 Lecture Eight: Images: II. Image Formed by a Thin Lens A thin lens is one whose thickness is small compared to the radii of curvature For a.
Curved Lenses SNC2P – Optics. Lenses Lenses are thin pieces of glass or plastic that have at least one curved side. There are two basic types of lenses:
Function of the eye and terms to know! emmetropia: Normal focusing hypermetropia: farsightedness : the failure of the lens to bend the light rays enough.
1 Light Chapters 36 – 39 2 Wave or Particle? Newton -- particles. In the early 19 th century, Young, Fresnel, and others -- wave. In 1860 Maxwell --
Vision. Normal Vision light is focused directly on the retina - can see clearly both near & far.
Aldric Bek 3I301 Physics ACE  Refraction occurs because light travels in different speeds in different media. In [pic 1], the bottom part of.
Its now time to see the light…..  A lens is a curved transparent material that is smooth and regularly shaped so that when light strikes it, the light.
L 33 Light and Optics [3] images formed by mirrors
HUMAN EYE AND LENSES. INTRODUCTION Eye is the light-sensitive organ of vision in animals. The actual process of seeing is performed by the brain rather.
AREA 2: Fitting single-vision lenses
J.M. Gabrielse Geometric Optics. J.M. Gabrielse Outline Basics Reflection Mirrors Plane mirrors Spherical mirrors Concave mirrors Convex mirrors Refraction.
 A lens is a transparent object with at least one curved side that causes light to refract  Like mirrors, lenses have surfaces that are described as.
Chapter 20 Mirrors and Lenses
Analysis for Optics Lab  Choose 6 hypothesis/data sections and analyze the hypothesis and the data 1. Briefly summarize the experimental setup 2. Summarize.
Refraction and Lenses. The most common application of refraction in science and technology is lenses. The kind of lenses we typically think of are made.
Part 10 Optics --Mirrors and Lenses Chapter 24 Geometric Optics.
Refraction of light pg. 77.
Refraction. Refraction of Light When light waves pass from one medium to the next, its speed changes, causing it to bend. Going from lower to higher index.
Lecture 25-1 Locating Images Real images form on the side of a mirror where the objects are, and virtual images form on the opposite side. only using the.
Lenses: Drawings Lesson 9 November 23rd, 2010.
Optical Crosses I don’t get it.
Lenses.
Lenses Lesson 10.
WELCOME TO VIEW OUR PROJECT ON DEFECTS OF HUMAN EYE DUE TO LIGHT.
Association of British Dispensing Opticians
Thin Lenses.
Presentation transcript:

Weight & Thickness of Lenses Identify the plus and minus lenses Plus lenses are thickest in the centre and get thinner towards the edge Minus lenses are thin in the centre and get thicker towards the edge PLUS lenses MINUS lenses

Frames – fitting HCL Properties of a well fitting frame: Appears straight on face Well fitting on the nose A large enough size so that person does not aware of edges of frame Eyes fairly well centred – horizontally – vertically (usual for eyes to be a little higher in frame) Lenses frame not too far away from the eyes well fitting behind ears

Frames – fitting HCL Frame types Metal OR Plastic Full frame Rimless frame half-rimless frame

1.Too narrow for face, bending back at hinge to get to ears 2.Eye size of frame not big enough for this person, sitting quite high 3.Frame sitting slightly tilted on face 4.Coming up off the ear on second photo Frame too small 1 2 3

1.Pupils very high in this frame 2.Eye size of frame too big/deep for this person 3.Again, frame slightly tilted on face 4.Actually quite good width overall Frame too big 1 2 3

1.Frame good width and shape on bridge of nose 2.Eye size of frame quite deep, but person has varifocal lenses, and frame has enough height above pupils 3.Frame level Well fitting Frame 1 2 3

1.Frame good width on face 2.Frame eye size has sufficient depth & is good size over bridge of nose 3.Frame level – but facial asymmetry - Right eye higher than left 4.Good fit over ear & appropriate tilt of frame on second photo Well fitting Frame

#1 Spherical Part MyopiaShort-sightedMinus numbers e.g D, -6.25D Moderate values +/-2.00 to 4.00D High values Greater than +/-5.00 Hypermetropia or Hyperopia Long-sightedPlus numbers e.g D, +5.75D #2 Cylindrical part AstigmatismOval or ‘rugby ball’ shaped eye (cornea) Cylindrical or toric lenses Number & Axis written after ‘Spherical’ part Moderate value / -1.50DC *α High values greater than / -2.50DC *α R / * 180 L / * 170 SphericalCylindrical Spectacle Prescriptions Analysing a spectacle prescription 1.Is it a myopic, hyperopic and/or astigmatic prescription? 2.Is it a moderate/high prescription?

4 Spectacle Prescriptions Lens Materials Ideally we want a lens to be light, thin and clear with little reflectance and that they are robust Nowadays, lenses are mostly made from Plastic material. This is safer and lighter than glass Basic lens material is called CR39 Lenses can be made thinner and lighter if they are made out of denser materials. These are called ‘high-index’ materials. There are a variety of types. They have slightly different properties. If prescription is moderate/high, advantageous that lenses are made from high-index material. Lenses will be thinner and lighter.