eye content specific topic

What is the retina and what is its primary function in the eye?

The retina is the innermost layer of the eye, responsible for absorbing light rays and converting them into nerve signals for transmission to the brain.

What is the alternative anatomical name for the retina?

The retina is also referred to as the internal or neural tunic.

How many distinct layers does the retina consist of and what are they called?

The retina consists of two distinct layers: the outer pigmented layer (retinal pigment epithelium – RPE) and the inner neural layer (neural retina).

Where is the retinal pigment epithelium (RPE) located?

Immediately internal to the choroid and attached to it.

What role does the retinal pigment epithelium play in Vitamin A metabolism?

Provides Vitamin A to photoreceptors.

How does the retinal pigment epithelium contribute to light absorption within the eye?

Contains melanin to absorb extraneous light, preventing it from scattering inside the eye (a function shared with the choroid).

What barrier function does the retinal pigment epithelium provide?

Blood-retinal barrier: facilitates the diffusion of nutrients and oxygen from the choroid to the neural layer while protecting it. to photoreceptors

What phagocytic role does the retinal pigment epithelium perform?

Removes old, worn-out discs from the tips of photoreceptor outer segments.

What structures are housed within the neural retina?

The outer layer houses the photoreceptors and inner neural layer associated neurons responsible for vision.i.e ganglion cells

What is the ora serrata and what does it separate?

The jagged margin separating the photosensitive posterior retina from the non-photosensitive anterior region (which covers the ciliary body and iris).

How many primary neuronal layers are involved in visual processing in the neural retina?

Three primary layers of neurons process visual information.

What is the function of photoreceptor cells in the retina?

Convert light energy into electrical energy and absorb light photon by their pigment (rhodopsins and photopsins) (transduction )enabling vision . reduced dark current as light hit them,.

Where are photoreceptor cells located within the neural retina?

Photoreceptor cells are located in the outermost layer.

What is the role of bipolar cells in retinal signal transmission?

Their dendrites synapse with photoreceptors, and their axons synapse with ganglion cells. They relay signals to ganglion cells

Bipolar cells respond to changes in glutamate release from photoreceptors. OFF bipolar depolarise when gluatamate is release in dark current, while ON bipolar depolarise when glutamate levels decrease/inhibited in light conditions.

Where are bipolar cells located within the retinal neuronal layers?

Bipolar cells form the middle neuronal layer.

What is the role of ganglion cells in the retina?

The axons of these cells converge to form the Optic Nerve (CN II). to process and send visual information to the brain

Which retinal cells are capable of generating action potentials?

ganglion cells are only cells in the retina to generate action potentials. other cells use graded potential,accumulative small local membrane voltage once threshold is reached , action potential generated

What are horizontal cells and where are they located?

Horizontal cells are located between photoreceptors and bipolar cells; they regulate and integrate signals.

What are amacrine cells and where are they located?

Amacrine cells are located between bipolar and ganglion cells. regulate and integrate signals

What is the general function of integration cells in the retina?

They regulate and integrate signals.

Which retinal neurons synapse directly with photoreceptors?

Bipolar cells.

Which retinal neurons synapse directly with ganglion cells?

Bipolar cells.

Which retinal layer and which cellsis responsible for forming the optic nerve?

Ganglion cells in inner neural layer ; the axons of these cells converge to form the Optic Nerve (CN II).

What is the functional significance of the neural retina?

Responsible for vision. and visual info to brain

Which part of the retina is non-photosensitive and what structures does it cover?

The non-photosensitive anterior region covers the ciliary body and iris.

What are the two types of photoreceptor cells found in the retina?

Rods and cones.

What is the primary function of rod cells?

Rods are responsible for scotopic (low-light) vision.

What type of vision do rods mediate and what is its functional significance?

Black and white vision in dim light.

Where are rods most densely distributed in the retina?

Rods are concentrated in the peripheral retina.

What is the primary function of cone cells?

Cones are responsible for photopic (daylight) vision.

What visual capabilities are mediated by cone cells?

Colour vision and high visual acuity.

Where are cones most densely concentrated in the retina?

In the fovea centralis.

How do rods and cones differ in their sensitivity to light?

Rods are more sensitive to light than cones.

Which photoreceptor type is responsible for detecting motion in low light conditions?

Rods.

What structural feature allows rods to be more sensitive to light than cones?

Rods contain more photopigment.

What photopigment is found in rod cells?

Rhodopsin.

What photopigments are found in cone cells?

Photopsins.

How many types of cone cells are present in the human retina?

Three types of cones.

What wavelengths of light do the three cone types respond to?

Short (blue), medium (green), and long (red) wavelengths.

What is colour vision dependent on at the cellular level?

Differential stimulation of the three cone types.

What is the macula lutea?

A yellowish pigmented area near the centre of the retina.

What is the functional significance of the macula lutea?

Responsible for detailed central vision.

What pigment gives the macula lutea its yellow colour and what is its function?

Xanthophyll pigments, which absorb damaging blue light.

What is the fovea centralis?

A small depression in the centre of the macula lutea.

What photoreceptors are found in the fovea centralis?

Only cones.

Why is visual acuity highest at the fovea centralis?

Each cone connects to a single bipolar cell and a single ganglion cell.

What structural adaptations reduce light scattering at the fovea centralis?

Other retinal layers are displaced to the side.

What is the optic disc?

The point where the optic nerve exits the eye.

Why is the optic disc referred to as the blind spot?

It contains no photoreceptors.

What vascular structures enter and leave the eye at the optic disc?

The central retinal artery and vein.

How does the distribution of rods and cones relate to peripheral versus central vision?

Cones dominate central vision, while rods dominate peripheral vision.

What visual deficit would result from damage to the macula lutea?

Loss of detailed central vision.

What visual deficit would result from widespread rod degeneration?

Impaired night vision.

What condition is associated with degeneration of photoreceptors in the macula?

Macular degeneration.

Why is the fovea centralis poorly suited for low-light vision?

It contains no rods.

How do rods and cones differ in neural convergence?

Many rods converge onto a single bipolar cell, whereas cones have minimal convergence.

What is the consequence of high convergence in rod pathways?

Increased sensitivity but reduced visual acuity.

What is the consequence of low convergence in cone pathways?

High visual acuity.

Which region of the retina provides the sharpest visual discrimination?

Fovea centralis.

Which region of the retina is specialised for motion detection in dim light?

Peripheral retina.

What is phototransduction?

The process by which photoreceptors convert light energy into electrical signals.

What happens to photoreceptors in darkness?

Sodium channels remain open, allowing Na⁺ to enter the cell, maintaining depolarisation (dark current).

What neurotransmitter do photoreceptors release in darkness?

Glutamate.

What effect does light have on photopigments in photoreceptors?

Light activates photopigments causing a conformational change.

What happens to sodium channels in photoreceptors when light is absorbed?

Sodium channels close.

What electrical change occurs in photoreceptors in response to light?

The cell becomes hyperpolarised.

How does neurotransmitter release change when photoreceptors are exposed to light?

Glutamate release decreases.

How does phototransduction differ from typical neuronal signalling?

Photoreceptors are depolarised in darkness and hyperpolarised in light.

What is the role of retinal bipolar cells during phototransduction?

Bipolar cells respond to changes in glutamate release from photoreceptors.

What is the role of retinal ganglion cells in visual signal transmission?

They generate action potentials that transmit visual information to the brain.

What are the two sources of blood supply to the retina?

The choroid and the central retinal artery.

Which retinal layers are supplied by the choroid?

The outer retinal layers including the photoreceptors.

Which retinal layers are supplied by the central retinal artery?

The inner retinal layers.

Why is the retinal blood supply considered functionally important?

Because photoreceptors have a high metabolic demand.

What is retinal detachment?

Separation of the neural retina from the retinal pigment epithelium.

Why does retinal detachment impair vision?

The neural retina loses its blood supply from the choroid.

What visual symptom is commonly associated with retinal detachment?

Sudden appearance of flashes of light and floaters.

Why is retinal detachment considered a medical emergency?

Prolonged separation leads to irreversible photoreceptor damage.

What is colour vision dependent on?

The presence of three types of cones sensitive to different wavelengths of light.

What is colour blindness?

A condition caused by the absence or malfunction of one or more cone types.

What is the most common form of colour blindness?

Red–green colour blindness.

What is the genetic basis of most colour blindness?

X-linked inheritance.

Why are males more commonly affected by colour blindness?

Because they possess only one X chromosome.

What visual capability remains intact in individuals with colour blindness?

Visual acuity.

What term describes complete absence of colour vision?

Achromatopsia.

What photoreceptors are affected in achromatopsia?

Cones.

What visual consequence results from cone dysfunction?

Reduced colour perception and reduced visual acuity.

What region of the retina is most affected in colour vision disorders?

The fovea centralis.

What clinical test is commonly used to assess colour vision?

Ishihara plates.

Why does rod function remain intact in most colour vision disorders?

Rods are not involved in colour vision.

What is the visual pathway from the retina to the brain?

Retina → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus → Optic radiation → Visual cortex.

Where do nasal retinal fibres decussate in the visual pathway?

At the optic chiasm.

What is the functional significance of decussation at the optic chiasm?

Allows information from each visual field to be processed in the contralateral hemisphere.

What visual defect results from damage to the optic nerve?

Complete loss of vision in the affected eye.

What visual defect results from a lesion at the optic chiasm?

Bitemporal hemianopia.

Why does a pituitary tumour commonly affect vision?

It compresses the optic chiasm.

What visual defect results from damage to the optic tract?

Homonymous hemianopia.

What is the lateral geniculate nucleus?

A relay nucleus in the thalamus.

What is the function of optic radiations?

Carry visual information from the lateral geniculate nucleus to the visual cortex.

Where is the primary visual cortex located?

Occipital lobe.