Summary
Summary Opthalmology Revision Posters
- Module
- Medicine
- Institution
- The University Of Sheffield (TUOS)
Revision posters for Ophthalmology Diseases
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By: physician786 • 6 year ago
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Anatomy of the EyeAverage length of human eye: 24mm
Essen6ally made up of 2 segments: Anterior, smaller segment: transparent; coated by cornea; radius 8mm;
Posterior, larger segment: coated by opaque sclera; 12mm radius
Cornea and sclera give the mechanical strength and shape to exposed surface of eye.
Cornea occupies central aspect of globe; one of most richly innervated 6ssues in body. Cornea = clear,
transparent, avascular structure, 12mm horizontally and 11mm ver6cally; gives 78% focusing power of the eye.
Anatomically, cornea made up of 5 layers: 1) Epithelium; 2) Bowman’s layer (membrane); 3) Stroma; 4)
Descernet’s membrane; 5) Endothelium: Endothelial cells lining inner surface of cornea = maintains clarity of the
cornea, by con6nuously pumping fluid out of the 6ssue. Any factor which alters func6on of these cells à
corneal oedema à blurred vision
Eyelids: prevent cornea drying and becoming irregular surface, by distribu6ng tear film over surface of globe
with each blink. History and Examina8on
Sclera: white opaque structure, covers 80% globe; con6nuous with cornea at limbus. 6 extraocular muscles Eye has limited mechanisms by which it can convey a dise
responsible for eye movements are aWached to sclera, and op6c nerve perforates it posteriorly. Common symptoms: visual acuity, redness, pain, discharg
Conjunc8va: covers anterior surface of sclera. Richly vascularized and innervated mucous membrane stretches trauma, pain/irrita6on, loss of vision, paWern and speed o
from limbus over anterior sclera (aka the bulbar conjunc6va); is then reflected onto undersurface of the upper Visual Acuity: clarity/sharpness of vision; use Snellen’s ch
and lower lids (tarsal conjunc6va). Area of conjunc6val reflec6on under lids makes up upper and lower fornix. Visual Field: area that can be seen with both eyes withou
Anterior Chamber: space between cornea and iris; filled with aqueous humour. AH is produced by ciliary body smaller than the binocular field. Qs to ask: does defect aff
(2μL/min) and provides nutrients and oxygen to avascular cornea. Ou_low of AH = though trabecular meshwork boundaries to defect? Does boundary lie in ver6cal/horiz
and canal of Schlemm adjacent to limbus. Any factor impeding ou_low will inc intraocular pressure. Upper range Extraocular movements: vital to examine extra-ocular m
of normal for intraocular pressure= 21mmHg which movement produces double vision
Uveal tract: made up of iris anteriorly, ciliary body and the choroid: Iris: coloured part of eye, under transparent Ophthalmoscopy: helps detect pathology in lens, vitreou
cornea. Muscles of iris diaphragm regulate size of pupil and control amount of light entering eye. Muscles of (red glow from choroid): Red reflexes are absent with de
ciliary body control accommoda6on of lens and secretory epithelium produces AH. Highly vascularized choroid bleeding. Any lens opacity (cataract) seen as black paWer
lines the inner aspect of the sclera; upon this = re6na loose floaters in vitreous seen as black floaters. Op6c disc
Lens: lies immediately posterior to pupil and anteriorly to vitreous humour. Transparent biconvex structure; and a central cup. Pale disc: op6c atrophy (e.g. chronic gl
responsible for 22% refrac6ve power of eye. By changing its shape: alter refrac6ve power and help focus objects excavated appearance (glaucoma)
at different distances from eye. By 40 years, ability to change shape starts to decline + lens starts to become less Examine radia6ng vessels and macula (ask pa6ent to look
transparent with 6me à cataracts. Slit lamp examina8on: bright light source, and horizonta
Vitreous humour: fills cavity between re6na and lens structures of living eye. Light source can be converted to
Re8na: mul6-layered structure. Two types of photoreceptor in re6na – rods + cones. 6million cones mainly allow intraocular pressure measurement.
confined to macula: responsible for central vision and color. Peripheral re6na: 125million rods: responsible for Indirect ophthalmoscope: Bright light source mounted o
peripheral vision. Axons of ganglion cells à op6c nerve (or disc) of the eye. binocular view of eye. Pt lies down; examiner holds conve
Blood supply to eye: ophthalmic A; central re6nal A responsible for supplying inner re6nal layers. Venous return re6na. Sclera is indented using blunt instrument to view w
through central re6nal and ophthalmic veins. Local lympha6c drainage to the perauricular and submental nodes. of re6nal examina6on- iden6fying re6nal tears/detachme
Sensory innerva8on of eye: through trigeminal (V) nerves. 6 extraocular muscles supplied by different nerves: External eye
• Oculomotor (III) nerve: medial, superior, inferior rectus and inferior oblique. Also supplies upper lid and Lids: symmetrical? Normal retrac6on on upward gaze (ab
indirectly the pupil (parasympathe6c fibres are aWached to it) spasm, inflamma6on or swellings?
• Trochlear (IV) nerve: Superior oblique Conjunc8va: inflamma6on (if circumcorneal, suspect ant
• Abduents (VI) nerve: lateral rectus fornix, and tarsal surfaces suggests conjunc6vi6s; focal in
• Facial (VII) nerve supplies orbicularis and other muscles of facial expression. problem on cornea). Discharge, follicles or upper lid cobb
conjunc6val haemorrhage?
Cornea: use a torch; any opacity, abrasion/ulcer, or oede
Anterior Chamber: Clear AH can be cloudy in anterior uv
Refrac8ve Errors (hypopyon) with corneal ulcer, or blood (hyphaema) aje
Eye projects sharp, focused image onto the re6na. Refrac6ve errors = abnormality in focusing mechanism of eye Lens: with a normal lens a pupil is black. Cataract may ma
As8gma8sm: present if cornea/lens doesn’t have same degree of curvature in horizontal and ver6cal planes à Pupils: should be equal and react to light and accommod
image is distorted either longitudinally/ ver6cally. Correc6ng lenses compensate accordingly. Can occur alone, irregular in anterior uvei6s (dilated, oval and fixed in acut
or may occur with myopia/ hypermetropia. Refrac6ve error of eye in which there is a different degree of
refrac6on in different meridians of curvature. May be myopic in one plane, and hypermetropic or emmetropic in
the other plane. Front surface of eye is more rugby ball shaped than normal football shape
Presbyopia: ciliary muscle reduces tension in lens, allowing it to get more convex, for close focusing. Young
lenses can go from far to near in 0.4sec. With age, lens s6ffens (presbyopia) à req glasses for reading. Changes Visual Acuity
start in lens at 40years and are complete by 60y. Normal ageing of lens leads to a change in refrac6ve state of Acuity = measure of clarity/sharpness of vision. Vital that
the eye. As lens ages, it becomes less able to alter its curvature à difficulty with near vision, esp reading. with eye problems
Treatment Snellen eye chart most commonly used; cover one eye w
Errors of refrac6on can be corrected by glasses/ contacts. occlude visual axis and read Snellen chart with the other
Contacts ojen results in beWer quality vision; risk of infxn; may be only op6on in some refrac6ve states e.g. LogMAR (logarithm of Minimum Angle of Resolu6on) incr
keratoconus (degen disorder of the eye: structural changes within cornea cause it to become thin and become a (unlike Snellen and other VA charts) has equal gradua6on
more conical shape than its normal gradual curve). space between lines. Fixed number of leWers (5) on each
Numerous surgical techniques can correct errors of refrac6on, with varying degrees of accuracy. Most popular The visual acuity of each eye is recorded in 2 ways:
method: use an excimer laser to re-profile corneal curvature (PRK, LASIK, LASEK). Laser either removes corneal 1) Distance visual acuity: Measured in Snellen leWers/ Log
6ssue centrally to flaWen cornea in myopia, or removes 6ssue from peripheral cornea to steepen it in sizes, constructed to subtend 5min (5’) of arc at nodal po
hypermetropia. Recording given as expression of line of leWers which can
Refrac6ve errors arise from disorders of shape and size of the eye. distance, usually 6m/ 20feet. E.g. 6/60: 6=distance (6m) o
Correct refrac6on depends upon distance between the cornea and re6na, and curvatures of lens and cornea. distance at which the leWer subtends 5’ at the nodal poin
Myopia (short sight): The eyeball is too long. In any eye, nearer objects focus on re6na (short sightedness) 2) Near visual acuity
unless concave spectacle (or contact) lenses are used. Lines on the Snellen Chart + Distance glasses to use:
Causes: Gene6c: chromosome 18P and 12Q. V close work in early decades (not just at school) may à changes in - 6: Able to read at 6m what can normally be read at 6
synthesis of mRNA and concentra6on of matrix metalloproteinase, à myopaia. - 9: Able to read at 6m what can normally be read at 9
ACh, DA, and glucagon are triggers for eye growth. In normal growth, changes in eyeball and lens curvature - 12: Able to read at 6m what can normally be read at
compensate for eye geung longer as it grows, but in myopic children, e.g. compensa6ons may not be occurring, - 18: Able to read at 6m what can normally be read at
so myopia worsens with age. Most do not become myopic un6l age of 6y (few are born myopic). Myopia will - 24: Able to read at 6m what can normally be read at
then usually con6nue to worsen un6l late teens, when changes stop below 6 dioptres in most people. It is thus - 36: Able to read at 6m what can normally be read at
important for children with myopia to have eyes regularly checked, as spectacle changes to be expected (maybe - 60: Able to read at 6m what can normally be read at
even every 6 months).Avoid over-correc6on: this may worsen myopia. In later life, increasing myopia may - Counts fingers; counts fingers held 1/2m distance: ‘C
indicate developing cataracts. - Hand movement; perceives hand moving 1/4m dista
Pathological myopia: rarely (<3%), myopia progresses >6 dioptres (some6mes up to >20 dioptres); serious - Perceives light; can see a torchlight when shone into
consequences later in life because secondary degenera6on of vitreous and re6na can à re6nal detachment, - No light percep6on, abbreviated to ‘no PL’, i.e. blind
choroidore6nal atrophy and macular bleeding.
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