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Bending LightBending Light

• Prism – A triangular piece of glass, plastic, etc with an Apex & a Base– Light is bent (refracted) toward the base of the

prism

Apex

Base

Apex

Base

Apex

Base

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Refractive LensesRefractive Lenses

• Refractive lenses are combinations of different shaped prisms

Convex LensConvergent

Concave LensDivergent

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Optics TerminologyOptics Terminology

• Parallel Light Rays – Assumed to be parallel if they emanate from a distance source

• Divergent Light Rays – Appear to be spreading apart in relationship to their close proximity to the eye

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Refractive Lens ConfigurationsRefractive Lens Configurations

Biconvex Plano-Convex Convex-Meniscus

ConvergentLenses

Biconcave Plano-Concave Concave-Meniscus

DivergentLenses

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Focal LengthFocal Length

• The distance from the center of the lens at which light rays Converge– The power of the lens is measured in Diopters (D)– Higher power lens move the focal point closer to

the lens

FocalPoint

Paraxial Rays

Axial RayNo Refraction

1.0 D Lens = Focal length of 1 meter

1.0 D Lens = Focal length of 1 meter

4.0 D Lens = 0.025 meter4.0 D Lens = 0.025 meter

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External Eye AnatomyExternal Eye Anatomy

MedialCanthus

LateralCanthus

LachrymalPapillae

CorneaLimbus

Sclera(Conjunctiva)

PupilIris

Caruncle

SemilunarFold

Superior Tarsal Lid

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Internal Eye AnatomyInternal Eye Anatomy

SuperiorFornix

InferiorFornix

CiliaryMuscle

VitreousBody

Cornea

OpticNerve

Macula(Fovea)

VitreousFace

Pupil

Iris

Lens

Limbus {

AnteriorChamber

PosteriorChamber

ZonularFibers Ocular

Muscles

SensoryRetinalLayer

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Corneal MorphologyCorneal Morphology

{

IntraocularPressure

13-19 mm Hg

500 - 550 µ

{700

- 900

µ

Corneal Diameter11 - 13 mm

Central CornealDiameter5 - 7 mm

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Corneal CurvatureCorneal CurvatureAverage Cornea44.00 Diopters

Steep Cornea47.00 Diopters

Flap Cornea40.00 Diopters

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Index of RefractionIndex of Refraction

• As light travels through glass, water or tissue, it slows down

• Light is bent as it strikes a material at an oblique angle– A higher Index yields greater refraction

Index of RefractionIndex of

Refraction

Air 1.00 (186,000 miles/sec)

Water 1.33 (146,000 miles/sec)

Aqueous 1.336Cornea 1.37 (136,765 miles/sec)

Lens Cortex 1.38Lens Nucleus 1.40PMMA Plastic 1.49 (124,832 miles/sec)

Crown Glass 1.52Flint Glass 1.65

SubstanceSubstance

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Tajam penglihatan dapat diperiksa dengan menggunakan :

Kartu SnellenHitung jariSenter

AV : NLP/ No Light Perception1/~ proyeksi …1/3001/605/606/406/156/66/6 E

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EmmetropiaEmmetropiaDistance Vision

Parallel (distant images)light is refracted by the Cornea & the Lens

Light is focused on the Fovea & images are clear

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EmmetropiaEmmetropiaNear Vision

Divergent (near images) light rays focus behind the retina

The lens changes shape (more convex) to focus near images on the retina (accommodation)

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PresbyopiaPresbyopiaDecreasing Accommodation

The lens can not accommodate enough to focus near images

The aging eye starts to lose it’s ability to accommodate

Bifocals or reading glasses are required

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MyopiaMyopiaNearsightedness

Parallel (distant images) rays are focused in front of the fovea

The Cornea is too Steep &/or the eye is too Long for it’s refractive capability

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Correcting MyopiaCorrecting MyopiaContact Lenses or Glasses

A CONCAVE lens diverges parallel light rays

The focal point moves back & distant images are clear

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Correcting MyopiaCorrecting MyopiaLaser Refractive Surgery

The cornea is reshaped, decreasing it’s convergent power

Parallel rays of light focus on the fovea

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MyopiaMyopiaNear Vision

Nearsighted people, without their glasses, can often focus near objects on the retina with little or no accommodation

The Divergent rays of objects near the eye are focused by the cornea & lens

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HyperopiaHyperopiaFarsightedness

The Cornea is too Flat &/or the eye is too Short

Light focuses in back of the Fovea

Both Distant & Near images are blurred

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HyperopiaHyperopiaLatent or Manifest Hyperopes

Young farsighted people can use accommodation to focus distant objects

Latent or Manifest Hyperopes will eventually need distance & reading glasses as their accommodative potential decreases with age

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Correcting HyperopiaCorrecting HyperopiaAbsolute Hyperopes

Full accommodation does not have enough power to focus distant images on the retina

A Convex lens is required to converge light rays on the fovea

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Correcting HyperopiaCorrecting HyperopiaLaser Vision Correction

The peripheral cornea is reshaped with the excimer laser

A Convex lens is required to converge light rays on the fovea

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HyperopiaHyperopiaNear Vision

Latent or Manifest Hyperopes usually need glasses to read because they have used all their accommodative potential to correct their distance vision

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AstigmatismAstigmatism

The Cornea is Steep in one axis & Flat in the other

Multiple focal points in the eye

Images are blurred &/or distorted

F1 F2

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AstigmatismAstigmatism

90°

180°

45 D45 D

42 D42 D

42.00 / 45.00 X090

With-The-RuleAstigmatism

Steep Axis Vertical90°

180°

42 D42 D

45 D45 D

42.00 / 45.00 X180

Against-The-RuleAstigmatism

Steep Axis Horizontal{Steep K & Axis

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Types of AstigmatismTypes of AstigmatismSimple Myopic

ƒ1ƒ1 ƒ2ƒ2

One focal point in front of retinaSecond focal point on retina

Simple Hyperopic

One focal point on retinaSecond focal point behind retinaMixed

One focal point in front of retinaSecond focal point behind retina

ƒ1ƒ1 ƒ2ƒ2

ƒ1ƒ1 ƒ2ƒ2

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Types of AstigmatismTypes of Astigmatism

ƒ1ƒ1 ƒ2ƒ2

Compound Myopic

Both focal points in front of retina

Compound Hyperopic

Both focal points behind retina

ƒ1ƒ1 ƒ2ƒ2

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• Astigmatisma: – with the rule - against the rule - irreguler astigmatism

• Anisometropia: – perbedaan sferis equivalen

• Aniseikonia: – beda ukuran dan bentuk bayangan

• Unilateral aphakia:– hiperopik anisometropia koreksi kacamata aniseikonia

25%; KL 7%• Akomodasi :

– amplitudo ( perobahan kuat lensa dpt) - range of amplitudo (jarak titik jauh dari titik dekat)

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Epidemiologi Epidemiologi

• Bayi – 3.0 dpt hiperopia 1 thn: 1.0 dpt– bayi – 6 thn panjang bulbus okuli > 5 mm

• Miopia:– 5-7 thn 3%; 8-10 thn 8%; 11-12 thn 14%; 12-17 thn 25%– Etnis cina miopia >>– Juvenil onset (7-16 thn) 0,5 dpt/thn 75% stabil 15-16 thn– Adult onset (20 thn) extensive near work

• Genetik - lingkungan• Edukasi tinggi prevalens miopia >>• Hiperopia: lower educational, 20% umur 40 an; 60%

umur 60an• Prevensi: tdk ada rekomendasi pasti

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Refraksi klinisRefraksi klinis

• Refraksi objektif: retinoskop• Refraksi subjektif

– sferis– Astigmat dial tehnik - Cross cylinder tehnik– Strongest plus - weakest minus maximum visual

acuity• Balans binokular• Sikloplegik - non• Overrefraksi

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Koreksi kacamata ametropiaKoreksi kacamata ametropia• Lensa sferis titik jauh, jarak vertex• Koreksi silinder

– Anak koreksi penuh– Dewasa coba penuh

• Kacamata anak: – bayangan jatuh pada retina– Balans optimal akkomodasi dan konvergens– Miopia: kongenital / developmental

• Sikloplegik refraksi• Koreksi penuh termasuk silinder• Orang tua informasi progresivitas alamiHiperopia: rendah (-), silinder koreksi; esotropia

koreksi penuh + sikloplegikAnisometropia: koreksi penuh; ambliopia th/ oklusi

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Problem akkomodasiProblem akkomodasi

• Presbyopia: respons akomodasi elastisitas lensa << mulai umur 40 thn

• Insufisiensi akomodasi asthenopik• Ekses akomodasi: spasmus siliaris sakit

kepala, sakit alis mata, kabur terutama dekat• Lensa multifokal:

– Penentuan kuat lensa tambahan:• Refraksi akurat• Amplitudo akomodasi• Pekerjaan (membaca, menjahit, komputer)

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Kontak lensaKontak lensa• Beda dari kacamata:

– Jarak vertex pendek– Perbatasan lensa - kornea: airmata bukan udara– Lapangan pandang: lebih besar– Besar bayangan: minus lebih besar; plus lebih kecil

• Anisometopia: lebih kecil• Akomodasi: miopia akomodasi >>; plus akomodasi

<<• Materi: HEMA,MMA,NVP• Jenis:

– soft KL, RGP KL, toric soft KL, bifokal KL, keratokonus / kornea abnormal KL, gas permeable scleral KL

• Therapeutic lens:– bullous keratopathy, erosi rekurrens, bell’s palsy, keratitis

(filamentary, posttrauma chemis), distrofi kornea, post operasi (KPL), nonhealing epithel defect, lid abnormalities, bleb leak posttrabeculectomy.

• Orthokeratology reshape cornea-hard KL

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Pemeriksaan pasien KLPemeriksaan pasien KL

• Palpebra, pergerakan palpebra, kedipan, film airmata, neovaskularisasi kornea, allergi

• Seleksi: soft-hard soft: adaptasi cepat, kenyamanan >>• Problem:

– Kornea: abrasi, keratitis pungtata, pewarnaan jam 9 & 3, infiltrat steril, keratokonjungtivitis superior limbik KL, keratitis dendritik, neovaskularisasi kornea, corneal warpage, ptosis.

– Mata merah: pengepasan kurang, hipoxia, deposit , KL rusak, toksik / alergi larutan KL, dry eye

• Transmisi HIV: desinfeksi trial lens:– Hard: hidrogen peroxid, desinfeksi panas (78*-80*/10 min)– RGP: idem kecuali desinfeksi panas– Soft: idem

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