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Nurfitri Bustamam 2  Introduction  Lens  cornea  Aperture of the camera  pupil diameter  Film  retina  More sophisticated  Protect...

Nurfitri Bustamam 2  Introduction  Lens  cornea  Aperture of the camera  pupil diameter  Film  retina  More sophisticated  Protective casing  Nervous system Nurfitri Bustamam 3 Nurfitri Bustamam 4  Learning Objectives  Describe the various parts of the eye and list the functions of each  Explain how light rays are brought to a focus on the retina  Explain common defects of the optical system of the eye  Define and explain visual acuity Nurfitri Bustamam 5  Anatomy of the Eye Nurfitri Bustamam 6 Nurfitri Bustamam 7 Nurfitri Bustamam 8 The tears dilute and wash away the irritating substance. Watery eyes  also occurs when inflammation of the nasal mucosa, such as occurs with a cold, obstructs the nasolacrimal ducts and blocks drainage of tears. Only humans express emotions, both happiness and sadness, by crying Nurfitri Bustamam 10   Lapisan mata:  Sklera (protektif, putih, tidak dpt dilewati cahaya) & cornea (di anterior, transparan). Sklera dilapisi membran mucosa yg jernih (conjuctiva)  Choroid (jaringan pembuluh darah)  Retina; melapisi 2/3 bag dlm choroid, berupa jar. saraf yg mengandung fotoreseptor  Lensa kristal; disangga oleh lens ligamen (zonula) yg terhubung dg badan ciliaris Nurfitri Bustamam 11  Iris (= rainbow) berada di depan lensa, terdiri dari melanosit, serat otot sirkular dan serat otot radial.  The amount of melanin in the iris determines the eye color. The eyes appear brown to black when the iris contains a large amount of melanin, blue when its melanin concentration is very low, and green when its melanin concentration is moderate. Nurfitri Bustamam 12 Nurfitri Bustamam 13   Aqueous humor: cairan jernih, dibuat oleh corpus cilaris dg cara difusi dan transpor aktif mengalir melalui pupil utk mengisi ruang anterior bola mata. Aqueous humor direabsorpsi oleh Canal of Schlemm yaitu vena- vena antara iris dan cornea.  Vitreous humor: materi gelatinosa jernih. Nurfitri Bustamam 14   Aqueous humor dibentuk rata-rata 2-3 l/menit Nurfitri Bustamam 16 Nurfitri Bustamam 17  Glaucoma: peningkatan tekanan intraokuler akibat obstruksi pada Canal of Schlemm. Hal itu dapat merusak retina. Tekanan normal bola mata: 10-20 mmHg.  Penyebab glaucoma: infeksi, perdarahan  akumulasi debris di Canal of Schlemm.  Terapi:  obat topikal  konstriksi pupil & menegangkan ujung iris  lebih permeabel utk aqueous humor.  obat utk mengurangi sekresi atau meningkatkan absorpsi aqueous humor atau dioperasi. Nurfitri Bustamam 18 Nurfitri Bustamam 19   Rods & cones (fotoreseptor).  Interneuron (inhibisi/eksitasi): sel bipolar, sel horisontal, sel amacrine, dan keluar mata via sel ganglion yg aksonnya membentuk serat n. opticus.  Pigmen epitel berperan utk mengabsorpsi cahaya agar tdk mengalami pemantulan/refleksi kembali shg bayangan tdk kabur. Nurfitri Bustamam 20   N. opticus meninggalkan bola mata mll optic disk (karena tdk ada reseptor maka bagian ini merupakan bintik buta).  Macula lutea (pigmen kuning) – pusatnya disebut fovea centralis yg tdk mengandung rods tetapi hanya cones yg sangat padat dan berperan dalam ketajaman penglihatan (acuity).  Age-related macular degeneration.  Gerakan bola mata bertujuan untuk menempatkan bayangan tepat di fovea centralis. Nurfitri Bustamam 21 Oftalmoskopi- melihat permukaan interior di belakang lensa (fundus) tdd retina, optic disc, macula, fovea, arteriole & vein in superficial layers of retina Nurfitri Bustamam 22   Pada fovea, setiap cone berhub. dg satu sel bipolar dan langsung ke n. opticus (penting utk ketajaman penglihatan).  Di luar fovea byk tdpt rods.  Rods : cones = 120 juta : 6 juta  N opticus tdd 1,2 juta serat  Rasio sel bipolar : sel ganglion = 105 : 1 (ada konvergensi) Nurfitri Bustamam 23  Comparison of Photoreceptors Characteristic Rods Cone Photopigment Rhodopsin Blue, green & red sensitive pigmen (cone pigment) Acuity Low High Threshold illumination Low High Type of vision Black/white Color Most concentrated Peripheral Central (fovea centralis) Wave peak sensitivity 505 nm Blue (445 nm), Green (535 nm), Red (570 nm) Estimated total 120 milion 7 milion number Nurfitri Bustamam 24 Nurfitri Bustamam 25  Prinsip Optik & Pembentukan Bayangan di Retina  Berkas sinar yg melewati pusat lensa tdk dibiaskan/refraksi  Besarnya bayangan ditentukan oleh sudut visual (visual angle)  Bayangan di retina terbalik (terbiasa sejak lahir) Nurfitri Bustamam 26 Nurfitri Bustamam 27  Inverted Glasess Experiment George Malcolm Stratton (1865 – 1957) was a psychologist who pioneered the study of perception in vision by wearing special glasses which inverted images up and down and left and right. Nurfitri Bustamam 28 Nurfitri Bustamam 29  Sea Walker in Bali Nurfitri Bustamam 30 Nurfitri Bustamam 31  Titik fokus lensa bergantung radius. Kekuatan refraksi = 1/jarak fokus dalam meter (Dioptri) Jarak fokus = 0,5 m kekuatan refraksi = 1/0,5 = 2 Dioptri Nurfitri Bustamam 32   M. ciliaris relaksasi jika melihat jauh ( > 6 meter)  Jika melihat dekat terjadi refleks akomodasi/near response (lensa mata mencembung karena kontraksi m. ciliaris, pupil konstriksi, & konvergensi mata).  Pada umur 40-45 th daya akomodasi mulai menurun (presbyopia) karena lensa mata mulai mengeras & melemahnya m. ciliaris akibat proses menua. Nurfitri Bustamam 33  Akomodasi  Refleks Stimulus: titik potong sinar di belakang retina Reseptor: cone & rod (bayangan kabur) Aferen: n. opticus Eferen: n. oculomotor  Proses: ciliary muscle kontraksi diameter mengecil ligamen mengendor lensa mencembung. Nurfitri Bustamam 34 Nurfitri Bustamam 35  Near point: titik jelas terdekat, pada usia 10 tahun 9 cm, 60 tahun 83 cm. Nurfitri Bustamam 38 Nurfitri Bustamam 39  Emmetropia; mata normal Myopia; rabun jauh Hyperopia; rabun dekat Nurfitri Bustamam 40  KLASIFIKASI (ETIOLOGI) Kelainan refraksi akibat bola mata yang Aksial/Sumbu pendek atau sumbu anteroposterior yang pendek/panjang Kelengkungan kornea atau atau Kurvatur lensa kurang/lebih sehingga bayangan tidak difokuskan di retina Terdapat indeks bias yang Refraktif kurang/lebih pada sistem optik mata  Astigmatism: 90% karena curvatura cornea & 10% karena curvatura lensa tdk uniform bayangan di retina kabur. Nurfitri Bustamam 42  Pengihatan jauh dan dekat akan kabur Melihat ganda dengan satu atau dua mata Melihat benda bulat menjadi lonjong Sakit kepala Mata pegal dan Lelah Nurfitri Bustamam 43  LASIK (laser-assisted in-situ keratomileusis) to correct the curvature of the cornea for conditions such as farsightedness, nearsightedness, & astigmatism. Nurfitri Bustamam 44  Angka berapakah yang anda lihat? Nurfitri Bustamam 45  Etiologi kelainan refraksi  Genetik  Perilaku Nurfitri Bustamam 46 Nurfitri Bustamam 47  Visual Acuity  Visual acuity: distinctness or discrimination of objects  All assessments of acuity depend on some estimation of the angle subtended at the eye by two line which can just be seen to be separated from each other.  The greater that angle, the less acuity  The standard of reference used is the best possible discrimination made by normal young subjects in bright light; this requires that the distinguishable line subtend an angle of 1 minute at the eye.  The commonest way of measuring a person’s acuity is to display rows of letters or symbols of different sizes (Snellen’s chart) at standard distance. The components of “6” or “20” row of letters are of a width each subtend an angle of 1 minute at the observer’s eye when he is 6 m (20 feet) away. Nurfitri Bustamam 48  A person whose vision rated 20/20 is seeing details at a distance of 20 feet as clearly as a normal individual could.  Vision noted as 20/15 is better than average, for at 20 feet the person is able to see details that would be clear to normal eye only at a distance of 15 feet.  Conversely, a person with 20/30 vision must be 20 feet from an object to discern details that a person with normal vision could make out at a distance of 30 feet. Nurfitri Bustamam 49 Uji Ketajaman Penglihatan: Snellen Chart  jarak jauh Jaeger Card  jarak dekat Nurfitri Bustamam 50  Visus V = 6/6 V < 6/6 Emetropia/hipermetropia miopia Lensa + Lebih Visus jelas mengecil hipermetropia emetropia Nurfitri Bustamam 52 Nurfitri Bustamam 53