PSIKOLOGI FAALINDERA PENGLIHATAN 1 & 2

Matrissya Hermita

RESEPTOR dan PENGINDERAAN

Reseptor : struktur yang menerima stimulus/rangsangan.Terbagi atas :

EksteroreseptorReseptor yang menerima rangsang/impuls dari

luar tubuh. Umum/biasa : suhu, tekanan. Khusus : reseptor indera

pengelihatan : retinapenghidu : bulbus olfactoriuspengecap : gema gustatoriaPendengaran : cocchleaTaktil : paccini, meissner

InteroseptorReseptor yang menerima

rangsang/impuls yang berkaitan/berasal dari organ dalam tubuh

eg. Lapar, haus, rasa sakit dalam

PropioseptorReseptor menerima rangsang/impuls

berkaitan dengan bagian anggota gerakan tubuh

eg. Posisi dan pergerakan tubuh

INDERA PENGLIHATAN

Anatomi MATATerdiri atas bulbus occuli (bola mata), struktur pelindung : cavum orbita (rongga mata), palpebrea (kelopak mata), conjunctiva, glandula lacrimalis (kelenjar air mata), dan penggerak bola mata (otot ekstrinsik penggerak bola mata : 4 mm. rectus, 2 mm. Obliquus) → melekat jadi 1 dsb capsula tenon.

BOLA MATABola mata mempunyai bentuk hampir “bulat” (D ± 23mm), dengan bagian anterior yang lebih cembung,disebut cornea.

Pada kutub posterior, N II keluar menuju otak pada bagian medial dari axis bola mata, dimana fovea centralis yang merupakan titik tempat bayangan jatuh berada lebih lateral.

Dindingnya terdiri atas 3 lapisan Lapisan terluar (tunica fibrosa) → sclera &

cornea Lapisan tengah (tunica vasculosa) →

choroid, corpus cilliaris, iris Lapisan terdalam (tunica interna) →

retina, sel epithel pigmen retina

Terbagi menjadi 2 ruangan yaitu COA (camera occuli anterior) dan COP (posterior) oleh iris.

Media refrakta → cornea, aquos humor, lensa, corpus vitreum

Apparatus akomodasi → lensa, zonula, otot cilliaris

ScleraThe sclera, which is white in adults, consists of packed lamellae of collagen fibers covering the posterior 5/6 of the eye. At the corneal limbus it becomes the substantia propria corneae (stroma).

CorneaThe cornea has a diameter of about 12 mm in adults. The outside of the cornea consists of stratified nonkeratinized squamous epithelium, which changes to the epithelium of the bulbar conjunctiva at the corneal limbus. The inside is formed by a single layer of flat endothelialcells. The refractive power of the cornea is about 42 diopters (Db). The central thickness is approximately 500 μm.

LensThe lens, with a horizontal diameter of about 10 mm, is situated in the posterior chamber of the eye. It is about 3–4 mm thick at the center.It is a biconvex lens, with the anterior surface less curved than the posterior surface. The lens shell, which surrounds the nucleus concentrically,lies beneath the lens capsule.

Vitreous BodyThe vitreous body, which is 95 % water, fills the vitreous space situated behind the lens. Its gelatinous consistency is due to the presence ofhyaluronic acid, mucopolysaccharides, and collagenfibrils.

ChoroidThe choroid occupies the major part of the middle layer of the eye. In addition to arteries and veins, it also carries approximately 15–20 ciliary nerves. It is separated from the retina by Bruch’s membrane, which is 2 μm thick.

Iris and PupilThe iris, like a diaphragm, forms the pupil. The iris is thinnest at the margin of the pupil and allows the bilaminar pigmented epithelium on the back to be seen. The pupil is surrounded by the sphincter pupillae muscle (parasympathetic innervation via the oculomotor nerve), the innervation of which produces contraction of the pupil (miosis). At the margin of the pupil, the iris is widely connected with the ciliary body. The muscle fibers of the dilatator pupillae muscle (cervical sympathetic) run here, contraction of which leads to pupil dilatation (mydriasis).

RetinaThe retina forms the inner layer of the eye. Divided into a nonsensory (anterior) part and an opticpart.The macula lutea (yellow spot) is lateral to this with the fovea centralis at its center, the site of maximum visual acuity.

The inner retina includes the photoreceptor cells and nine further identifiable layers of the cerebral layer. Primary sensory epithelial cells → 120 million rods and 6–7 million cones.

There are only cones in the fovea centralis, with no other layers of the cerebral layer. Rods and cones constitute the retina’s receptors.fovea centralis consists exclusively of cones, which are responsible for color vision in good lighting (photopic vision).

The rods are responsible for vision in poor light (scotopic vision); their greatest density is around the fovea centralis but they are also distributed over the entire retina.

The photoreceptors are absent in the region of the optic disc → blind spot

Optic Nerve and Optic Tract

The optic nerve is about 45 mm in length, twothirds of which is inside the orbit. At the lamina cribrosa 1 million nerve fibers leave the eyeball and from this point are surrounded by a medullary sheath of oligodenroglia, duramater and pia mater.

After passing through the optic canal, it reaches the optic chiasm on the floor of the third ventricle after running about 10 mm in the middle cranial fossa. Here the nasal fibers of the retina cross to the opposite side. The optic nerve fibers run as the optic tract as far as the lateral geniculate body.

The optic radiation (Gratiolet’s radiating fibers) runs from here through the posterior crus of the internal capsule to the primary optic visual cortex, the area striata, area 17.

AccommodationAccommodation signifies the ability of the eye to focus the rays from objects to form a clear image on the retinal plane in relation to the objects’ distance from the eye.Accommodation is based in particular on the ability of the elastic lens to change from a more spherical shape with high converging power (near focus) to a more elliptical shape with low converging power (distant focus).

Visual acuity means the resolving ability of the eye with an optimally correcting lens, i.e. the ability of the retina barely to distinguish two points from one another (resolution threshold). A normal eye can just differentiate two points when the rays emerging from them form an angle at the eye of one minute of arc (1/60 degree).Visual acuity is calculated from the actual distance of the points from the eye divided by the distance at which the normal eye can resolve the points, and in the normal eye it is therefore 1ßq = 1.0. Optotypes projected into the distance

Visus sangat dipengaruhi oleh sifat fisis mata (aberasi mata = kegagalan memfokuskan bayangan tepat di fovea centralis), besarnya pupil, komposisi cahaya, kemampuan akomodasi, elastisitas otot, intensitas cahaya, faktor retina

V = d/D

AdaptationAdaptation (A) signifies the adjustment of the eye to different light levels. This is a complex process, which comprises a change in pupil size, a change between rod and cone vision, and a change in the sensitivity of the retina.

According to the duplicity theory of vision, daytime and color vision (photopic vision) is a function of the cone apparatus, while vision in dim light and night vision (scotopic vision) are provided by the rod apparatus.

Light adaptation means the transition to photopic vision and is based on pupil constriction and the transition from rod to cone vision with the breakdown of rhodopsin.

GERAK BOLA MATA

N III → m rectus superior, m.rectus inferior, m. rectus medial,m.obliquus inferior

N IV → m obliquus superiorN VI → m. rectus lateral

BUTA WARNA

AKROMATISME/AKROMATOPSIA/Total → tidak dapat membedakan warna dasar, terlihat hitam dan abu-abu

DIAKROMATISME/Partial → bisa mbedakan warna tertentu Deutrinophia : sel kerucut hijau (-) Protanophia : sel kerucut merah (-) Tritanophia : sel kerucut biru/kuning (-)

Menurut Hering ada 3 macam fotokhemis yang mempunyai 6 macam kualitas yang memberikan 6 macam sensasi → substansi putih-hitam, merah-hijau, biru-kuning. Test Buta warna → Uji Holmgren, Uji Stiling-Isihara.

Mata manusia dapat mendeteksi hampir semua gradasi warna bila cahaya monokromatik merah, hijau dan biru dicampur secara tepat dalam berbagai kombinasi tergantung persentase campuran warna-warna dasar tersebut.

Young & Helmholtz → Sel kerucut dapat menerima warna merah, hijau dan biru.

Ke tiga macam sel kerucut mengandung fotokhemis yang dapat diurai oleh sinar matahari, bila ketiga macam sel kerucut itu mendapat stimulus yang bersamaan maka akan terlihat warna putih. Warna-warna lain merupakan kombinasi dari ketiga macam warna dasar.

Thank You!!!!!