Transcript 1-Constrictor pupillae ms.

VISÃO
MEIOS REFRATIVOS DO OLHO
Dr. Nisreen Abo-elmaaty
Physiology Department
Dr. Nisreen Mansour
LUZ VISÍVEL
• A LUZ VISÍVEL (OU COMPRIMENTO DE ONDA ENTRE 400-700 NM) SÓ
PODE EXCITAR OS FOTORRECEPTORES
•OS RAIOS INFRA VERMELHOS NÃO PODEM EXCITAR, SÃO
PERCEBIDOS APENAS COMO CALOR.
•OS RAIOS ULTRAVIOLETA SÃO FILTRADOS PELO CRISTALINO.
Dr. Nisreen Mansour
CONCEITOS BÁSICOS
REFRAÇÃO :
• It is the bending of light rays when they travel in 2
transparent media with 2 different refractive
indices, provided that they travel at angulated
interface.
 INDICE DE REFRAÇÃO (IR) DE UM MEIO
=
velocidade da luz no ar
velocidade da luz no meio
•
e.x. O IR da cornea é 1.38 significa
= velocidade da luz no ar / velocidade da luz na
cornea = 1.38
Dr. Nisreen Mansour
• Raios paralelos (vindos
de > 6 m) alteram o seu
curso nas bordas de
uma lente convexa
• Num ponto
determinado da lente,
os raios passarão
através de um ponto;
Ponto Focal.
• Distância Focal : é a
distancia entre o
centro da lente e o
Ponto Focal.
PONTO FOCAL
DISTÂNCIA FOCAL
Poder Dioptrico da lente é a medida de sua capacidade de refratar
os raios luminosos.
Poder Refrativo = 1 metro / distância focal = ? Dioptrias.
O Poder Dióptrico é inversamente
relacionado
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Mansour com a Distância focal
O GLOBO OCULAR
• 24 mm em diâmetro
Dr. Nisreen Mansour
• 3 camadas + fluidos
intraoculares & câmaras
CÂMARAS OCULARES & FLUIDOS
O CRISTALINO DIVIDE A CAVIDADE OCULAR EM 2
CÂMARAS PREENCHIDAS DE FLUIDOS
INTRAOCULARES :
CÂMARA ANTERIOR
•Anterior ao cristalino
•Dividida pela iris em:
câmaras anterior &
posterior.
•Preenchida com
Humor Aquoso (fluido
aquoso incolor)
CÂMARA VITREA
•Posterior ao cristalino
•Preenchido com
Humor Vitreo (fluido
incolor gelatinoso)
Dr. Nisreen Mansour
HUMOR AQUOSO
• Clear transparent fluid filling ant. & post.
chambers.
• Formed by the epithelial lining of ciliary
processes of ciliary body at a rate of 1-3 μl
/min.
• Composition
Relative to plasma, Aqueous H is:
- alkaline, nearly protein-free fluid
- Higher Na+ & HCO3 content
- Higher vit. C, pyruvic & lactic acids
- Lower glucose
Dr. Nisreen Mansour
CIRCULAÇÃO & DRENAGEM DO HUMOR AQUOSO
cristalino
H. Aquoso sai dos processessos ciliares→ flui entre os ligamentos
suspensores→ câmara posterior → através da pupila→ Câmara
ant. → através do ângulo iridocorneal (angulo de filtração)
→espaço de Fontana → canal de Schlemm → veias aquosas →
veias episclerais → veias sistêmicas
Dr. Nisreen Mansour
FUNÇÕES DO HUMOR AQUOSO
• One of refractory media of the eye
• Supply of O2 & nutrients for avascular
cornea & lens.
• Buffering & removal of acid products of
anaerobic metabolism of cornea & lens.
• Keeping intraocular pressure (IOP)
constant by the balance between its
formation & drainage.
Dr. Nisreen Mansour
HUMOR VITREO
• Transparent gelatinous mass held together by
fibrillar network. (little flow of fluid; Vitreous body).
• Filling the space between lens & retina.
• Separated from lens by a very narrow Retrolental
space.
• Enclosed in a thin hyaloid membrane, firmly
adherent to retina around optic disc.
• Functions:
- one of the refractive media of the eye.
- support of intracocular structures (lens & retina).
- Maintenance of spherical shape of eye.
Dr. Nisreen Mansour
MEIOS REFRATIVOS DO OLHO
MEIO
INDICE DE
REFRAÇÃO
(IR)
Ar
1
Cornea
1.38
Humor Aquoso
1.33
Cristalino
Humor Vítreo
1.40
1.34
PODER
REFRATIVO
+39 Dioptrias
+20 Dioptrias
• The refractive power of cornea is mainly due to its anterior
• The Lens: half of bending occurs at its ant. surface & half
at its posterior surface.
Dr. Nisreen Mansour
O SISTEMA ÓPTICO DO OLHO
The divergent light rays must pass through an optical system
that brings them back intoDr.focus.
The cornea & lens is the
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optical system of the eye that focus light rays onto the retina
CORNEA
• It is the transparent anterior 1/6 of outer layer.
• Its thickness is 1mm at the periphery & 0.5 mm at
centre.
• Richly supplied by sensory nerve endings (branches
of ophthalmic division of V cranial n).
• The cornea itself is avascular, but the corneoscleral
junction is richly supplied by capillaries.
• Derives its nutrition from aqueous humour
(glucose), tear film (O2) & corneoscleral capillaries.
Dr. Nisreen Mansour
FUNÇÕES DA CÓRNEA
1- The most powerful refractive medium of
eye; 39 dioptres (2/3 of refractive power of
eye) → formation of sharp clear image.
2- Protective for sensitive intraocular
structures:
- tough.
- absorbs UV rays.
- initiator of Corneal reflex which is a
protective reflex.
Dr. Nisreen Mansour
O QUE CAUSA A TRANSPARÊNCIA CORNEANA ?
1- ESTRUTURA ANATÔMICA
• Non-vascularity
• Regular arrangement of collagen fibres of substantia
propria & of corneal epithelium.
• Non-myelinated nerve fibres running parallel to
collagen fibres.
2- DETURGÊNCIA CORNEANA
Achieved by an active endothelial pump → maintenance
of corneal fibres packed together.
Dr. Nisreen Mansour
ANORMALIDADES DA CÓRNEA
1. OPACIFICAÇÃO CORNEANA ;
- is partial loss of corneal transparency.
- is a complication of corneal ulcer.
- ttt: corneal grafting.
2. ASTIGMATISMO;
- the corneal curvature is not equal in all
planes.
- ttt: cylinderical or contact lens.
3. CERATOCONE (CORNEA CÔNICA );
- congenital condition characterised by
conical protrusion of cornea.
- usually bilateral & appears at puberty.
- ttt: contact lens or corneal grafting.
Dr. Nisreen Mansour
O CRISTALINO
 Is a biconvex lens composed of a strong elastic capsule filled with
viscous transparent proteinaceous fluid.
 Lens diameter ~ 10 mm, its thickness ~ 4 mm.
 The capsule is attached to ciliary body by suspensory ligaments (70), the
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tension of these ligaments is controlled
by ciliary ms.
The Lens
• Its transparency
is caused by
 uniform
arrangement of
its fibres,
 no blood vessels,
dehydration
 normal lens
metabolism.
• Is avascular;
derives its
nutrition & O2
supply from
aqueous humour.
Dr. Nisreen Mansour
Dr. Nisreen Mansour
FUNÇÃO DO CRISTALINO
• The 2nd major refractive medium of the eye;
Its refractive power (20 dioptres) represents
~ 30% of total refractive power of the eye.
• The important is that the lens is the only
player responsible for adjustment for
distance;
It can increase its refractive power, in
response to nerve signals from the brain,
providing the important mechanism of
Accommodation.Dr. Nisreen Mansour
REFLEX O DE ACOMODAÇÃO (RESPOSTA DE PERTO)
• Accommodation is the ability of the eye to keep
the image of an object focused on the retina as the
distance between the object & retina varies
• Accommodation Reflex (Near Response) is the
changes occurring in the eye as a result of retinal
blurred image of the near object.
• Response:
1- Constriction of the pupils.
2- ↑ Thickness of the lens (more spherical;
becomes very convex (instead of moderate
convexity).
3- Medial convergence of the eyes.
Dr. Nisreen Mansour
Dr. Nisreen Mansour
The lens becomes more spherical during near
vision (contraction of ciliary muscle)
Dr. Nisreen Mansour
• VIA DO REFLEXO DE ACOMODAÇÃO :
Blurred retinal image → retinal nervous elements →
optic nerve → optic chiasma → optic tract →LGB
(thalamus) → optic radiation → primary visual
area; 17; occipital lobe & association visual area;
18, 19
Area 8, Frontal eye field area
Somatic III n. supplying medial recti
Superior Colliculus, midbrain
Edinger-Westphall n. of III n.
Convergence
The image falls on fovea centralis
Ciliary ganglion
+ Ciliary ms.
+Constrictor pupillae ms.
↑ curvature of lens
↑ depth of focus
↑ its refractive powerDr. Nisreen Mansour ↓ excess light
Prevents aberrations
VIA REFLEXA DA ACOMODAÇÃO
Dr. Nisreen Mansour
• AMPLITUDE DE ACOMODAÇÃO
 Is the difference between refractive power
of the lens on maximum accommodation &
in far vision when the lens is fully relaxed.
It decreases gradually with age due to loss
of lens elasticity & weakness of ciliary ms.
• PONTO PRÓXIMO
 The nearest point is the minimal distance from
the eye at which an object can be brought into
focus
 recedes with age (same reasons above).
Dr. Nisreen Mansour
Age
Nearest point
(years)
(cm)
Amplitude of
Accommodation
(dioptres)
10
10
14
20
14
10
30
20
7
40
50
5
60
100
1
Dr. Nisreen Mansour
PRESBIOPIA


is the physiological progressive loss of the
accommodation with age due to loss of
elasticity of the lens (partly because of
denaturation of lens proteins), until the lens
becomes totally non-accommodating at the
age of 70 years.
Corrected by wearing convex lens for near
vision (e.g. reading).
Dr. Nisreen Mansour
• VÍCIOS DE REFRAÇÃO
 In normal eye (emmetropic), parallel rays
from distant objects converge to a focus on
the retina, provided that the ciliary ms. is
completely relaxed.
 If this does not occur → an error of
refraction
• VÍCIOS DE REFRAÇÃO
1. Hipermetropia (olho curto).
2. Miopia (olho longo).
3. Astigmatismo. Dr. Nisreen Mansour
MIOPIA (OLHO LONGO)
Dr. Nisreen Mansour
HIPERMETROPIA (OLHO CURTO)
Dr. Nisreen Mansour
VÍCIOS DE REFRAÇÃO
NORMAL - EMÉTROPE
MIOPIA
MIOPIA CORRIGIDA
HIPERMETROPIA
HIPERMETROPIA
CORRIGIDA
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Myopia
Hypermetropia
Defect
Focus in
Focus behind
front of retina retina
Cause
-long eye ball -short eye ball
-Strong lens - Weak lens
ttt
Biconcave
Biconvex lens
lens (diverge) (↑refractive
power)
Dr. Nisreen Mansour
Astigmatism
Focus of rays in
one plane is at
different
distance from
that of rays in
another plane.
- Unequal
curvature of
cornea or lens.
Cylindrical lens
in suitable plane
Contact lens.
•
a)
b)
c)
d)
During near vision, which of the following is
false?
The tension in the suspensory ligaments is
increased
The tension in the lens capsule is decreased
The lens becomes more round
There is an increased signal to ciliary
muscle
Dr. Nisreen Mansour
Dr. Nisreen Mansour
CONTROLE DO DIÂMETRO PUPILAR
The diameter of the pupil
varies between 1.5 mm (bright
light) – 8 mm (darkness).
This achieved by the presence
of 2 smooth muscles;
1-Constrictor pupillae ms.; its
fibres arranged in a circular
manner around pupil. Receives
motor postgang.parasympathetic supply along short
Ciliary nerves (pregang.from
EW n of III relay in ciliary
ganglion).
2- Dilator pupillae ms.; its fibres
arranged radially around pupil.
Receives post gang. sympathetic
from SCG (pregang. arise in 1, 2
Thoracic segments.
Dr. Nisreen Mansour
CONTROL E DO DIÂMETRO PUPILAR
The diameter of the pupil
varies between 1.5 mm (bright
light) – 8 mm (darkness).
This achieved by the presence
of 2 smooth muscles;
1-Constrictor pupillae ms.; its
fibres arranged in a circular
manner around pupil. Receives
motor postgang.parasympathetic supply along short
Ciliary nerves (pregang.from
EW n of III relay in ciliary
ganglion).
2- Dilator pupillae ms.; its fibres
arranged radially around pupil.
Receives post gang. sympathetic
from SCG (pregang. arise in 1, 2
Thoracic segments.
Dr. Nisreen Mansour
Dr. Nisreen Mansour
REFLEXO A LUZ



Stimulus: exposure of one eye to light.
Response: Ipsilateral constriction of pupil (Direct
Light Reflex) & Contralateral pupillary
constriction (Indirect or consensual Light Reflex).
Pathway: light → retinal nervous elements →
optic nerve →optic chiasma → optic tract →
ipsilateral pretectal nucleus in midbrain → along
tectonuclear tract around aqueduct of Sylvius →
to EW nuclei (parasymp n of III) of both sides →
motor pregang. to ciliary ganglion → post
ganglionic along short ciliary nerves → + bilateral
constrictor pupillae ms. → bilateral constriction of
pupils.
Dr. Nisreen Mansour
LUZ
MESENCÉFALO
REFLEXO A LUZ
Dr. Nisreen Mansour






PUPILA DE ARGYLL-ROBERTSON
NÃO-REATIVA À LUZ MAS REATIVA À
ACOMODAÇÃO.
DEVIDO A LESÃO DO TRACTO TECTONUCLEAR
(POR SIFILIS OU SIRINGOMIELIA DO AQUEDUTO
DE SILVIO).
PUPILA REVERSA ARGYLL-ROBERTSON
NÃO-REATIVA A ACCOMODAÇÃO MAS REATIVA
À LUZ.
DEVIDO A LESÃO NO TRACTO
OCCIPITOTECTAL.
Dr. Nisreen Mansour
O CAMPO VISUAL
CAMPO BINOCULAR
CAMPO D
CAMPO E
Dr. Nisreen Mansour
VIAS ÓPTICAS E DEFEITOS DE CAMPO
a. CEGUEIRA DO OLHO
IPSILATERAL
ANOPIA DE O.E.
b→ HEMIANOPIA BITEMPORAL
HEMIANOPIA HETERÔNIMA
C → HEMIANOPIA HOMÔNIMA
LESÃO DA AREA 17 (D) →
HEMIANOPIA HOMÔNIMA
DO LADO OPOSTO COM
LIVRAMENTO MACULAR
Dr. Nisreen Mansour
BOA SORTE
Dr. Nisreen Mansour