3.The clarity of the signal transferred can affect interpretation of the intended visual communication

Explain how the production of two different images of a view can result in depth perception Some animals have forward facing eyes Each eyes sees an image of an object in the light path There is overlap b/w the 2 views.

Death perception vision of objects as they exist in 3D space Due to focusing of objects at different distances from the eye. When these images from both eyes ( +both visual fields) are fused object will appear in 3D. Stereoscopic vision: each eye is separated horizontally so they have slightly different views. Fusion = putting together 2 images from left + right visual fields + from 2 eyes as they reach the brain.

HSC Questions:

Process and analyse information from secondary sources to describe cataracts and the technology that can be used to prevent blindness from cataracts and discuss the implications of this technology for society

Cataracts = visual defect caused by clouding of lens Loss of lens transparency Interferes with ability for eye to transmit clear signal by obstructing path of light through the eye. Total blindness can result if not treated

Cause Natural consequence of aging Present at birth (CONGENITAL) Develop form disease (diabetes, thyroid disorders) Excessive use of certain drugs Excessive exposure to UV rays.SYMPTOMS

Clouding of the pupil Vision become blurred Double vision Halos around images Loss of colour vision Impaired night vision

Statistics: African American + Caribbean people most likely to get this In Aus : Overall = 11% 90+ 60-70% 50-59- 4% Infants 1 in 4500 Indigenous Aus 3x more likely.

Surgical procedure Local anaesthetic, sometimes general Eye drops given to dilate pupil In most cataract surgeries, removed lens is replaced by intra ocular lens which can be made of plastic, silicon or acrylic compound.

Intra capsular surgery Involves surgically removing entire lens + capsule ( outer covering of lens)

Extra capsular surgery Removing lens but leaving intact half of capsule Slightly longer incision on side of cornea Hard centre of lends removed in one piece Remainder of lens ( softer lens cortex) removed by suction

Phacoemulsification Most advanced = small incision, no stitch Tint probe inserted into eye Probe emits ultrasonic waves that soften+ break up lens Debris is removed by a syringe Artificial lens inserted into space left in existing lens capsule SOCIAL IMPLICATION Cost of surgery is minimal Tremendous contribution to self-esteem of patients1. Prevent loss of vision2. Contributes to a better quality of life3. Happy person = happy society Economic benefits:1. People can continue working life + pay tax2. Less welfare payments3. Gov can allocate funds to other areas

Eliminates need carers:1. Loss of jobs

Australian scientists in field of microsurgical replacement of lenses

Dr Fred Hollows 1. Developed cheap corneal replacements to cure certain types of blindness that are common in developing countries.2. Work is being carried through Fred Hollows Foundation

4. The light signal reaching the retina is transformed into an electrical impulse.

Identify photoreceptor cells as those containing light sensitive pigments and explain that these cells convert light images into electrochemical signals that the brain can interpret.

Varies among species but is able to absorb light and convert them into electrical impulses that can be interpreted by the brain. Humans Complex single lens eye: capable of accommodation to produce image on retina Rods : sensitive to low intensity of lights Cones: colour vision

Flatworms Only detect presence of light no colour. For direction

Bees Ommatidium:

Describe the differences in distribution, structure and function of the photoreceptor cells in the human eye

Outline the role of rhodopsin in rods Made up of protein opsin + derivative of vitamin A retinal ( if this is lacking, vision is affected + condition night blindness can result)

Absorb light and undergoes photo-excitation

Separates into 2 parts: opsin + retinal

Generates nerve impulse that travels to the brain via optic nerve.

Allow new image to be received

Identify that there are three types of cones, each containing a separate pigment sensitive to either blue, red or green light

Explain that colour blindness in humans results from the lack of one or more of the colour-sensitive pigments in the cones.

Red Green colour blindness Sex linked Caused by defect in red-green decoder Red + green are confused as redness is taken out of red light + greenness is taken out of green light both will appear brownish Red colour shifted towards green + green shifted towards red Incidence = 1/12 males 8%

Blue Yellow colour blindness Autosomal Caused by defect in blue-yellow decoder Blue + yellow are confused Both are perceived as greyish Incidence = rare