• Cornea has much greater refractive power than lens
• But cornea cannot be changed, whereas lens can, to focus objects
• Upper eyelid - softest skin texture in whole body
• Can harvest upper eyelid for grafts elsewhere (good texture, very vascular)
• Cornea usually transparent, can only be seen if diseased (eg. Corneal scarring)

• Can only see central part of retina with ophthalmoscope (need other instruments to see peripheral part of retina)
• Macula is temporal to optic disc

Histological structure of retina

• Optic nerve: nerve fibre from retina to optic nerve layer
• Photoreceptors - rods and cones
• Pigmented epithelium under retina: retinal epithelium
• Then choroid and sclera (outer part)

From in to out:

• Ganglion cell
• Nerve fibre
• Optic nerve: goes to brain
• Optic chiasm
• 2 optic nerves decussate at optic chiasm
• If pituitary tumour, presses on optic chiasm, causing visual field defects
• Pupillary pathway different from optic pathway

Optic tract

Lateral geniculate body

Optic radiation

Visual cortex

• Visual Acuity

1. Central part served by macula
2. Important parameter to be noted on Pt's chard

• External Examination

1. Lip position
2. Swelling

• Pupillary Reaction

1. Visual Field
2. Confrontation
3. Visual field machines

• Extraocular Movement

1. Nerve palsy which prevent ocular movt

• Cover & Uncover Test

1. Misalignment of eyes - squint

• IOP Measurement
• Direct Ophthalmoscopy

1. Not only eye Pt, also medical and surgical Pt
2. Fundal examination standard examination for all body systems

• Snellen eye chart
• Visual acuity
• Near visual acuity chard (Jaeger card)
• Penlight
• Occluder
• Direct ophthalmoscope

1. Visual Acuity
2. Pupillary Reaction
3. Direct Ophthalmoscopy
4. IOP measurement

What's 20/20 vision?

• Normal visual acuity
• Glaucoma: normal VA, but constricted visual field

• Pt distance from chart:
• Standard: 6m / 20 ft
• If not enough room: 3m with mirror
• 1st number (numerator): testing distance: 20 ft / 6m
• 2nd number (denominator): a normal eye can read the same letter from 20 ft / 6m
• Normal vision: VA: 20/20 (6/6)
• Weaker eye: shorter distance, larger letter size - VA 20/40 (6/12)
• For poor vision that can't even see the largest letter

1. Count finger (CF)
2. Hand movement (HM)
3. Light perception (LP)
4. No light perception (NLP)

• Reveal refractive errors against other pathologies including amblyopia
• Pinhole (1-3 mm diameter)allows only 1 ray from each point on an object to pass through
• Clear image is formed regardless of position of screen
• Clear retinal image produced up to high but not extreme refractive errors (3D)

• Important
• Reading
• Bedridden patient
• Convenient

• Different from adult
• Attractive targets
• Fixation: eg. On toy
• Picture card
• Matching (SG Test)
• Cover one eye: if child doesn't become angry, probable that other eye is OK
• Very small children: electrodiagnostic tests (they are usually uncooperative)

• Pupillary pathway
• Stimulate one pupil, both sides constrict (both direct and consensual/indirect response)
• Afferent goes to same side and crosses over
• Efferent is bilateral innervation
• Pupil muscles
• Dilator pupillae: sympathetic
• Constrictor pupillae: parasym.
• Pupil
• Size
• Shape: round; ruptured globe may have oval / peaked pupil (iris may have moved as well) - Pt can be blind within 24hr from infection entering the eye
• Reactivity

• 1mm difference in pupil size
• Pathological:
• Local: Trauma, Drugs
• Sympathetic: Horner's syndrome (small pupil)
• Parasympathetic: Third nerve palsy (dilated pupil)

• Light reflex (involuntary)

1. Direct
2. Indirect

• Near reflex (voluntary: Pt needs to fixate on near object - accommodation - pupil will constrict)

• Indirect light reflex: observe pupil constriction in fellow eye
• Near reflex: ask patient to look at near object

1. Eyes converge and look down a little
2. Pupil will constrict
3. Lens will accommodate

• Eg. Pt has normal near reflex but abnormal light reflex: light-near dissociation - eg. Neurosyphillis (affects Edinger-Westphal nucleus)
• Eg. Chronic glaucoma (optic nerve disease): advanced cupping (normal ratio 0.3, in this Pt 0.9); abnormal light reflex due to optic nerve damage
• Eg. Optic neuritis
• Eg. Orbital tumour: optic nerve tumour: optic nerve glioma (increased in neurofibromatosis) or meningioma
• Eg. Sub-total Retinal Detachment: retina normally red, detached: becomes hypoxic and retina becomes opaque, therefore appears white

DIAG

• Red reflex
• Red colour due to choroid
• Choroidal BV are larger than retinal BV

• Astigmatism: 2 diopters, negligible (cannot be corrected by opthalmoscope)
• Magnification: 15 x (emmetrope: refractive error less than 5D)
• Field: 1.5 disc diameters (emmetrope)
• Myopic: increased magnification, decreased field

Environment

• Dim room light: less pupil constriction
• Unobstructed distant fixation target at eye level (or else eye will wander and pupil size will vary)
• Chairs

Patient

• Age: younger (pupil larger, no disease like cataract), older (may dilate pupil; must tell nurse)
• Lens - cataract
• Sit upright comfortably
• Distant fixation
• Well informed of the procedure

Ophthalmoscope

• Filters: yellow (more comfortable for Pt) or white light
• Intensity of light: 50% (don't use maximum power; otherwise uncomfortable for Pt, pupil will constrict)
• Light beam width same as pupil size

Examiner

• Clear instruction: patient fixation
• Start arm's length from patient eye
• 30 degree temporally
• Ophthalmoscope close to examiner's eye (remove glasses and adjust refractive error in opthalmoscope; or continue wearing glasses and don't adjust)
• Same level as patient
• Stand right side to examine right eye of patient
• Examiner R side to patient's R side (or else you will kiss!)
• +4 diopter lens
• Find the red (orange) reflex: gentle side to side movement if don't see red reflex - then follow red reflex in
• Note anterior part of eye - eg. Vitreous opacity
• Slowly approach patient 30 degree temporally
• Slowly decrease + power of lens
• Hand holding ophthalmoscope may touch patient's cheek finally for stabilisation
• Disc : trace major vessel
• Macular centre : 2 disc-diameter from disc

DIAG of Retina

• Optic disc / optic nerve head
• Macula
• Vasculature

Color

Cup disc ratio

Circumference

Circulation

• Retinal periphery: ask patient to look into corresponding direction

• Neovascularisation
• Retinal large vein occlusion - fan-shaped haemorrhage
• Age-related macular degeneration
• Retinal detachment
• Laser treatment: decreased risk of retinal detachment

• Useful tool in general practice
• Medium clarity
• Red reflex against white reflex
• Optic disc
• Macula
• Vascular & perivascular abnormality
• Torch: can use in light reflex
• Magnifying instrument

• Normal < 21 mmHg
• Measuring: (1) Contact (2) Non-contact (eg. Air puff)
• Contact - Applanation (bottom left) - gold standard
• Contact: Schiotz (bottom right) - put instrument on Pt's eye, read measurement, read against table
• Non-contact: air puff

CONTACT: Rm 703, Administrative block, 28553788, lill@ha.org.hk