CASE 3 :MYOPIA

MODUL 1 : OPHTHALMOL

OGY

GROUP 7 WULAN-FADZELY-ARIF

AMRI-SAFUAN ARIF-NADIAH-

INSYIRA-FATIMAH-ANDI

ABSHARINA

CASE • A young female patient, 15 years old, was diagnosed of moderate

myopia ODS, based on the following: • History : blurry vision on both eyes, especially if she needs to see

in a distance (far sight). It occurred for the past 7 years. History of spectacle prescription(+) since she was on 3rd grade and has been changed once a year, the last prescription was S-5.0 D for both eyes. Red eyes (-), tearing (-), discharge (-), photophobia (-), pain (-), foreign body sensation (-), systemic disease (-), history of using spectacles (-). There is a history in the family of using spectacles, and her brother is currently using (+) spherical glasses.

• Physical finding : general state: Mild/Good nutrition/Conscious• Vital sign : BP=120/80mmHg, Pulse=80x/min,

Breathing=20x/min, Temp=37.1⁰C• Ophthalmology findings :

• Visual acuity: OD:6/60; corrected S-5.75D →6/6

OS:6/60; corrected S-5.75D →6/6

• Intraocular pressure: OD:Tn OS:Tn• Anterior

Eye OD OS

Palpebra Normal Normal

Cilia Normal Normal

Bulbar conjunctiva / palpebral conjunctiva

Normal/hyperemic (-)

Normal/hyperemic (-)

Cornea Clear Clear

COA Normal Normal

Iris Dark brown, crypt (+)

Dark brown, crypt (+)

Pupil Round, central, light reflex(+)

Round, central, light reflex(+)

Lens Transparent Transparent

MYOPIA

ANATOMY &

PHYSIOLOGY OF EYE

GEOMETRICAL OPTICS

DEFINITION

ETIOLOGYPATHO

GENESIS

CM

TREATMENT

PROGNOSIS COMPLICATIONS

DD

ANATOMY OF EYE

REFRACTIVE MEDIA • Cornea• Aqueous humor• Lens• Vitreous humor

Segments & Chambers of Eyeball

SEGMENTS

Anterior segment

(→lens)

Anterior chamber -anterior border : post cornea

-posterior border : ante iris

Posterior chamber -anterior border : post iris-posterior border : lens +

zonules-lateral border : ciliary body

Posterior segment (from lens

backwards)

PHYSIOLOGY OF VISION

• Involve photoreceptors

PHOTOTRANSDUCTION

• Photoreceptors → ganglion cells→ lateral geniculate body→ primary visual cortex

PROCESSING & TRANSMISSION

OF VISUAL SENSATION

• Integration of light sense, form sense, sense of contrast and colour sense

VISUAL PERCEPTION

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GEOMETRICAL OPTICSG

EO

METR

ICA

L O

PTIC

S REFLECTION

Change in path of light rays without any change in the

medium

REFRACTION

Change in path of light rays travelling from 1 medium to

another of different density

Reflection

• Laws of reflection: •The incident ray, the reflected ray and the normal at the point of incident, all lie in the same plane.•Angle of incidence (Ɵ2) = angle of reflection (Ɵ1)

Ɵ1 Ɵ2

Refraction• Laws of refraction: • The incident and refracted rays are on opposite sides of the normal and all the three are in the same plane. • The ratio of sine of angle of incidence(i) to the sine of angle of refraction(r) is constant(=refractive index, n)

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MYOPIA

DEFINITION• A type of refractive error in which parallel rays of

light coming from infinity are focused in front of the retina when accommodation is at rest

• = short-sightedness

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ETIOLOGY• ↑ anteroposterior length of eyeball• ↑ curvature of cornea/lens• ↑ refractive index of lens

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CLASSIFICATIONS

1. According to amount of Diopters• <3D : mild myopia• 3-5D : moderate myopia• >5D : high myopia

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PATHOGENESIS• ↑ AP length of eyeball → AXIAL TYPE MYOPIA

• Underdevelopment of cornea → ↑ curvature of cornea → CURVATURAL TYPE MYOPIA

• ↑ thickness of cornea/lens → ↑ refractive index of lens → INDEX TYPE MYOPIA

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CLINICAL MANIFESTATIONS• Poor vision for distance• Squinting of eyes• Eye appear larger• Deep Anterior Chamber (AC)• Large, sluggishly reacting pupils• Opthalmoscopy : myopic cresent

Pathomechanism of Blurred Vision & Squinting of Eyes• The light coming into the eye from distant objects

focuses in front of the retina which makes vision blurry. → Squinting eyes.

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MANAGEMENT & TREATMENT• Optical concave spheris lens

SpectaclesContact lens

• SurgicalRadial keratotomyPhotorefractive keratectomyLaser in situ keratomileusisPhakic IOL’s

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PROGNOSIS• Early onset and high myopia have a worse

prognosis for long term visual acuity.• Tend to have a higher rate of myopic progression

with longer axial lengths.• Greater risk for developing myopic retinal

degeneration.

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COMPLICATIONS • Cataract complicated• Glaucoma• Retinal detachment• Choroidal haemorrhage• Strabismus convergens

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DIFFERENTIAL DIAGNOSIS

Myopia

Focal point of parallelincident

lightrays

Causes Vision Possible complications

Optical correction

Anterior to theretina

•Eyeball too long(axial myopia).•Excessive refractivepower(refractivemyopia).

•Very good nearvision.•Poor distancevision.

•Increased risk ofretinal detachment.•See p. 434 forcomplicationsspecific to pathologicmyopia.

Diverging lenses(minus or concavelenses).

HyperopiaFocal

point of parallelincident

lightrays

Causes Vision Possible complications

Optical correction

Posterior to theRetina

•Eyeball too short(axial hyperopia).•Insufficientrefractive power(refractive hyperopia

•Poor near vision.•Accommodationusually permitsnormal distancevision (in youngpatients and inslight to moderatehyperopia).

•Disposition toacute angle closureglaucoma(shallow anteriorchamber). Cautionis advisedwith diagnosticand therapeuticmydriasis.•Esotropia

•Converging lenses(plus or convexlenses).

Astigmatism

Focal point of parallelincident

lightrays

Causes Vision Possible complicatio

ns

Optical correction

Lack of a focalpoint

Anomalies in thecurvature of thenormally sphericalsurfaces of therefractive media(cornea and lens).

Patients see everythingdistorted.

Risk of refractiveamblyopia.

Cylindrical lenses;eyeglass correctionis only possiblewhere astigmatismis regular.

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