Eye and vision Flashcards
What meninge are the sclera and cornea derived from?
Dura mater
What meninge is the choroid of the eye derived from?
Arachnoid mater
What is the retina derived from?
Extension of the brain
What are the symptoms of Horner’s syndrome?
Ptosis
Miosis
Anhidrosis of forehead
Flushing
What forms the outer fibrous layer of the eye?
Cornea
Sclera
What forms the middle vascular layer of the eye?
Choroid
Contains ciliary body and iris
What forms the inner layer of the eye?
Retina
Contains sphincter and dilator pupillae
What are the layers of the retina from internal to external?
Inner limiting membrane
Nerve fiber layer
Ganglion cell layer
Inner plexiform layer
Inner nuclear layer
Outer plexiform layer
Outer nuclear layer
Outer limiting membrane
Photoreceptor outer segment
Retinal pigment epithelium
What separates the choroid from the retina?
Bruch’s membrane
What are rods and cones?
Photoreceptors
What composes the outer segments of the rods and cones?
Modified cilia made of stacks of flattened saccules or membranous disks
Where is the photosensitive compound in rods and cones located?
Outer segment in the saccules and disks
What part of the retina renews the rods and cones?
Pigment epithelium
What prevent the reflection of rays back through the retina?
Extra melanin in the pigment epithelium absorbs extra light
What is the likely inheritance of retinitis pigmentosa?
Autosomal recessive
What is retinitis pigmentosa?
Phagocytic process is defective leading to a build up of debris causing blindness
What is the blood supply of the receptors in the retina?
Mostly from capillary plexus in the choroid
What is the fovea?
In center of macula
Densely filled cones and without rods
What photoreceptor is more effective in low light intensity?
Rods
What photoreceptor can detect a broader range of wavelengths?
Rods
What photoreceptor passes information as a group to a single nerve fiber?
Rods
What photoreceptor is more sensitive to movement?
Rods
What photoreceptor responds more slowly to light?
Rods
What is the pigment found in rods called?
Rhodopsin
What photoreceptor is more numerous?
Rods
What photoreceptor is more effective in high light intensity?
Cones
What photoreceptor is sensitive to a specific color/wavelength?
Cones
What photoreceptor acts individually on a single nerve fiber?
Cones
What photoreceptor is for sharpness, gives a higher visual acuity?
Cones
What photoreceptor responds more rapidly to light?
Cones
What pigment is contained in cones?
Iodopsin
What retinal layer does convergence mostly occur in?
Inner synaptic/plexiform layer
What is the response of bipolar cells in the eye?
Generate relatively steady hyperpolarization or depolarization
What is the response of horizontal cells in the retina?
Enhances brightness contrast to produce a sharper image
What is the function of amacrine cells in the retina?
Record changes in illumination
What vitamin is needed in the retina?
Vitamin A
What is a deficiency in vit A cause?
Night blindness
Follicular hyperkeratinosis
Susceptibility to infection
Cancer
Anemia
What pathway is vit A used for in the eye?
Regeneration of rhodopsin
What is xerophthalmia?
Progressive keratinization of cornea leading to deterioration of eye tissue
What causes xerophthalmia and keratomalacia?
Prolonged deficiency of vit A
What is keratomalacia?
Wrinkling, progressive cloudiness, and increasing softening and ulceration of the corneas
What are bitot spots?
Dry, silver-gray, triangular deposits on conjunctiva
What photoreceptor is for color vision?
Cones
What is scotopic vision?
Dark-adapted system that operates at low levels of illumination
What is photopic vision?
Light-adapted system that operates at high levels of illumination
What is the Purkinje shift?
Shifting from photopic to scotopic vision
What is the inheritance for color blindness?
X-linked recessive
What are the three types of cones?
S - blue
M - green
L - red
What is the pupillodilator reflex?
Pupil dilates in response to emotion that activates the SyNS
What is the course of the pupillodilator reflex?
Through posterior hypothalamus through brainstem to preganglionic sympathetic neurons in the lateral horn of spinal cord at T1 and then to the superior cervical ganglion at the base of the skull and then to the ophthalmic division of CN V
What are the afferent components of the pupillary light reflex?
Photoreceptors
Optic N
Optic chiasma
Optic tract
Pretectal nucleus in midbrain
What is the efferent pathway of the pupillary light reflex?
Edinger-Westphal nucleus
Oculomotor N
Ciliary ganglion
Short ciliary N
Sphincter pupillae
What is accommodation as it relates to vision?
Process by which the eye adjusts the shape of the lens to keep objects in focus
What is presbyopia?
Normal distance vision, but accommodation is reduced with age
What is Marcus Gunn pupil?
Consensual light response normal in unaffected eye
Eye dilates in when light is shown in affected eye
What is Argyll Robertson Pupil?
Accommodation reflex present
Pupillary light reflex absent
Caused by neurosyphilis
What are the afferents and efferents of the corneal reflex?
Aff - CN V
Eff - CN VII
What is the reason for macular sparing?
Larger representation for macula in the visual cortex
What extra-ocular muscle is innervated by the abducens N?
Lateral rectus
What extraocular muscle is innervated by the trochlear N?
Superior oblique
What extraocular muscles are innervated by the oculomotor N?
Medial rectus
Superior rectus
Inferior rectus
Inferior oblique
Where is the horizontal gaze center?
Paramedian pontine reticular formation in the pons
Where is the vertical gaze center located?
Rostral midbrain reticular formation
What are the conjugate eye movements?
Saccades
Smooth pursuit movements
Vestibulo-ocular movements
Optokinetic nystagmus
What are the disconjugate eye movements?
Convergence
Divergence
What are saccades?
Rapid, ballistic movements of the eyes that abruptly change the point of fixation
What controls saccades?
Frontal eye field
What is internuclear ophthalmoplegia/ophthalmoparesis?
Inability to perform conjugate lateral gaze due to damage of interneuron between CN VI and CN III (medial longitudinal fasciculus)
What are signs of internuclear ophthalmoplegia?
Abducting eye displays nystagmus
Convergence is normal