introductiontobasicophthalmology

7/27/2019 Introductiontobasicophthalmology

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Introduction to

ophthalmologyBy

Dr.Bakhtiar Q. Jaf



Objective of the lecture ►To give a simple introduction to clinical

anatomy, physiology & embryology ofthe eye

TO recognize clinical approach to the eyecomplaints



na omy o e eyeThe eyeball, or globe, sits in a protective bonystructure known as the orbit. Lined with muscle,

connective and adipose tissues.the orbit is about 4 cm in height, width, anddepth and is shaped roughly like a four-sided

pyramidsurrounded on three sides by the sinuses: Theethmoid (medially), the frontal (superiorly), and

the maxillary (inferiorly). The optic nerve and the ophthalmic artery enter the orbit at its apex through the optic

foramen.



Eyelids protect the anterior portion of theeye , composed of thin elastic skin that

covers striated and smooth muscles & thetarsal plates.Tears are vitally important to the health ofthe anterior segment of the eye. They areformed by the main lacrimal gland and the

accessory lacrimal glands. The conjunctiva, a mucous membrane,provides a barrier to the external

environment and nourishes the eye.



The sclera , commonly known as the "white of the

eye," is a dense fibrous structure that composesthe posterior five sixths of the eyeThe cornea a transparent avascular domelikestructure, forms the most anterior portion of theeyeball and is the main refracting surface of theeye. Behind the cornea lies the anterior chamber ,filled with a continually replenished supply of

clear aqueous humor, which nourishes thecornea.



The uvea consists of the iris, the ciliarybody, and the choroid. The iris, orcolored part of the eye, is a highly

vascularized, pigmented collection offibers surrounding the pupil. The pupil is a space that dilates and constricts in

response to light.



Directly behind the pupil and iris liesthe crystalline lens, a colorless and

almost completely transparent biconvexstructure held in position by zonularfibers. It is avascular and has no nerveor pain fibers. The lens is suspended behind the iris

by the zonules and is connected to theciliary body. The ciliary body controlsaccommodation through the zonular

fibers and the ciliary muscles.



The posterior chamber is a small space

between the vitreous and the iris. Aqueous fluid is

manufactured in the posterior chamber by theciliary body

The choroid is layered between the retina and

the sclera and is a highly vascularised tissue,supplying blood to the adjacent outer portion of

the retina.

The ocular fundus is the largest chamber of theeye and contains the vitreous humor, a clear

gelatinous substance, mostly water, encapsulated

by a hyaloid membrane, the vitreous humor .



visual pathway Good vision is not dependent solely

on a healthy functioning eyeball butalso on an intact visual pathway.This pathway is made up of theretina, optic nerve, optic chiasma,optic tracts,

lateral geniculate bodies, opticradiations &the visual cortex of the occipital

lobe.

The pathway is an extension of thecentral nervous system. The opticnerve is the second cranial nerve.Its function is to transmit visualimpulses from the retina to thehigher centers in the brain.



eyetheof Embryology

andectodermThe eye is formed from both

that is derivedneuroectoderm. Themesenchymefrom the neural tube gives rise to (the retina, thefibers of the optic nerve, and the smooth muscle

on the side ofsurface ectodermof the iris). Thethe head forms( the corneal and conjunctivalepithelium, the lens, and the lacrimal and tarsal

forms( the cornealmesenchymeglands). The

stroma, the sclera, the choroid, the iris, theciliary musculature, part of the vitreous body,and the cells lining the anterior chamber).



The rudimentary eyeball develops as anectodermal diverticulum from the lateral aspectof the forebrain. The diverticulum grows out

laterally toward the side of the head, and the endbecomes slightly dilated to form the optic vesicle ,while the proximal portion becomes constricted

to form the optic stalk .At the same time, a small area of surfaceectoderm overlying the optic vesicle thickens to

form the lens placode . The lens placodeinvaginates and sinks below the surface ectodermto become the lens vesicle , the optic vesiclebecomes invaginated to form the double-layeredoptic cup .



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► At end of 4th week of pregnancy; Optic Vesiclecontact with surface ectoderm & invaginate toform Optic cup & the lens vesicle



The optic nerveThe ganglion cells of the retina develop

axons that converge to a point wherethe optic stalk leaves the posteriorsurface of the optic cup. This site willlater become the optic disc .The axons now pass among the cells

that form the inner layer of the stalk.Gradually, the inner layer encroacheson the cavity of the stalk until the inner

and outer layers fuse.



The Ocular Examination Visual AcuityAfter the patient's chief complaint and history have

been established, visual acuity should be assessed.This is an essential part of the eye examination and ameasure against which all therapeutic outcomes arebased. Most health care providers are familiar with thestandard Snellen chart. This chart is composed of aseries of progressively smaller rows of letters and is

used to test distance vision. The fraction 6/6 is considered the standard of normalvision. Most people can see the letters on the linedesignated as 6/6 from a distance of 6 meters.



The External Eye Examination After the visual acuity has beenrecorded, an external eyeexamination is performedDIAGNOSTIC EVALUATIONDIRECT OPHTHALMOSCOPY Is a hand-held instrument with

varying plus and minus lenses.

The lenses can be rotated intoplace, enabling the examiner tobring the cornea, lens, and retinainto focus



Indirect Ophthalmoscopy

Is an instrument commonly used by theophthalmologist. It produces a bright andintense light. The light source is fixed with apair of binocular lenses, which are mounted onthe examiner's head. The ophthalmoscope isused in conjunction with a hand-held 20-dioptcrlens. This instrument enables the examiner to

see larger areas of the retina, although in anunmagnified state.



Slit-Lamp ExaminationIs a binocular microscope mounted on a table. This instrument enabls theuser to examine the eye with magnification of 10 to 40 times the real

image.Color Vision TestingBecause alteration in color vision is sometimes indicativeof optic nerve problems, color vision testing is oftenperformed in a neuro-ophthalmologic workup.

UltrasonographyLesions in the globe or the orbit may not be directlyvisible and are evaluated by ultrasound.Color Fundus Photography

Fundus photography is a technique used to detect anddocument retinal lesions. The patient's pupils are widelydilated during the procedure, and visual acuity isdiminished for about 30 minutes due to retinal"bleaching" by the intense flashing lights.



Tonometry

Tonometry is used to measure IOP by determining the amount of

force necessary to indent or flatten (applanate) a small anteriorarea of the globe of the eye.

Gonioscopy

Gonioscopy is used to visualize the angle of the anterior chamber

to identify abnormalities in appearance and measurements.

Perimetry Testing

Perimetry testing is used to evaluate the field of vision. A

visual field is the area or extent of physical space visible

to an eye in a given position. Its average extent is 65degrees upward, 75 degrees downward, 60 degrees

inward, and 95 degrees outward when the eye is in the

primary gaze.



IMPAIRED VISION REFRACTIVE ERRORS

In refractive errors, vision is impairedbecause a shortened or elongated eyeballprevents light rays from focusing sharply on

the retina. Blurred vision due to refractiveerror can be corrected with eyeglasses andcontact lenses.

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Those patients for whom the visual image focuses

precisely on the macula and who do not need eye glasses

or contact lenses are said to have emmetropia.



People with myopia have deeper eyeballs; the distant visual

image focuses in front of, or short of, the retina. These people

are nearsighted and are termed myopic and experience blurred

distance vision.



When people have a shorter depth to their eyes, the visual

image focuses beyond the retina; the eyes are more shallow and

are termed hyperopic. People who have hyperopia are

farsighted.



GLAUCOMA Glaucoma is the term used to describe a group of

ocular conditions characterized by optic nervedamage, high intraocular pressure and visualfield deffect. CLASSIFICATION OF GLAUCOMA

Glaucoma can be open angle or angle closure,depending on which mechanisms cause theimpairment of the aqueous outflow. Glaucoma

can also be primary or secondary, depending onwhether associated factors contribute to the risein IOP.



CATARCTA cataract is a lens opacity orcloudiness

Clinical Manifestations Painless blurring of vision ischaracteristic of cataracts.

C l U d O l M di i



Commonly Used Ocular MedicationsTopical AnestheticsOne to two drops of proparacaine hydrochlorideand tetracaine hydrochlorid are instilled before

diagnostic procedures such as tonometry andgonioscopy and in minor ocular procedures suchas removal of sutures or conjunctival or cornealscrapings.Mydriatics and Cycloplegics

Mydriasis, or pupil dilation, is the main objectiveof the administration of mydriatics andcycloplegics



Anti-lnfectivesAnti-infective medications include

antibiotics, antifungals, and antivirals.Most are available as drops, ointments, orsubconjunctival or intravitreal injections.

Antibiotics include penicillin, thecephalosporins, aminoglycosides, andfluoroquinolones. The main antifungalagent is amphotericin B. Antivirals includeacyclovir and ganciclovir.



Corticosteroids and Nonsteroidal Anti-

Inflammatory Drugs The topical preparations of corticosteroids

are commonly used in inflammatory

conditions of the eyelids, conjunctiva,cornea, anterior chamber, lens, and uvea. In

posterior segment diseases that involve the

posterior sclera, retina, and optic nerve, thetopical agents are less effective; hence, the

parenteral and oral routes are preferred.



References1. Lecture notes in

ophthalmology2. Parson’s disease

of the eye

introductiontobasicophthalmology

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