01. dr. jannes frits tan - refraksi2009
DESCRIPTION
mata, sistem indraTRANSCRIPT
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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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