PEG Flashcards
Posterior Eye and General Ophthalmology
What is an ophthalmoscope used for?
The examination of the fundus to detect ocular diseases and monitor eye health. It is a common handheld instrument used in practice.
What is incident light?
Any natural or artificial light that falls on an object. Incident light makes objects visible and is either absorbed or reflected by the object
Who invented the ophthalmoscope?
Hermann von Helmholtz in 1851
How does an Ophthalmoscope work?
A Light source from the batteries is focused onto a two-way mirror. The mirror is placed at a 45 degree angle causing the beam to be reflected at a 90 degree angle onto the patients fundus. The examiner looks through a hole in the mirror and the light that reflects off of the patients fundus is focused through a focusing lens onto the examiners retina. The image seen is only clear if both px and examiner are emmetropic (or corrected)
Why is it advantageous that an ophthalmoscope is handheld?
The instrument is portable and allows it to be used in domiciliary care to provide eye exams for those unable to leave the house/visit an optometrist
What are the main components of the ophthalmoscope?
- Aperture stops (different sized light beams) including slit beam
-Range of lenses (to ensure both px and examiner are emmetropic)
-Red free diagnostic filters (to see ocular structures like blood vessels more clearly/dyes can be used alongside this)
-fixation targets (for the px to focus on)
-Graticules (for measurement of ocular structures)
What does it mean that an ophthalmoscope image is erect?
The image is right side up
What are some advantages of ophthalmoscopy?
-Image is erect and real
-No dilation required
-Lack of light reflections leading to clearer image
What are some disadvantages of ophthalmoscopy
-Close working distance (some px may be uncomfortable, increased likelihood of transmitting infection/germs)
-Limited view (2 disc diameters can be seen so cant see all of retina)
-Monocular, one of examiners eye is used so cannot detect depth/3D structures)
What is a disc diameter?
the term “disc diameters” refers to the size of the optic disc in mm.
Why is it important that we use ophthalmoscopy for the examination of the ocular media, fundus and anterior segment?
-Assessment of the fundus is typically a legal requirement for any primary eyecare examination
-Allows us to screen for internal eye diseases such as: Cataracts.glaucoma.maculopathy
-Allows us to screen for systemic diseases such as diabetes and hypertension
What is maculopathy
A term used to describe any damage to to macula
What is hypertension?
also known as high blood pressure, occurs when the force of your blood pushing against the walls of your blood vessels is consistently too high
What are the conditions for a routine ophthalmoscopic examination?
-Dimly lit room
-use right eye to examine px right eye and left eye to examine the px left eye
-select appropriate aperture stop so that both examiner and px are emmetropic
-maintain close working distance
What is examined on the external eye using ophthalmoscopy?
eyelids, lashes and sclera
Explain how you would examine the ocular media using ophthalmoscopy
Firstly look for the fundus reflex (orange glow). Examine the opacity of the media for example by looking out for black spokes within the red reflex as this is a sign of a type of cataract.
What is examined during the ophthalmoscopy of the internal eye?
-optical disc colour
-clarity of the disk margin (is it blurred)
-Cup to disk ratio
-Neuroretinal Rim (ISNT rule)
-Arteries and veins (work along them and check for damage or bulging)
-Examine all 4 quadrants of the retina
-Assess macula and fovea
What is the ISNT rule
A way to remember the way the optic disk is meant to look in a healthy eye. Created after the assessment of optic disk photographs of 457 healthy eyes
Why is the ISNT rule important
Used in clinical practice to detect any glaucomatous optic neuropathy (damage to the optic nerve)
Describe the ISNT rule
The neuroretinal rim in normal eyes shows a similar configuration. It is usually
broadest in the inferior rim, followed by the superior and nasal rims, and thinnest in the
temporal rim. The ISNT rule is an order of rim width
What are some important variations to look for when using direct ophthalmoscopy on the internal eye
-Optic cup size
-ratio of cup to optic disc size (and ISNT rule)
-Myopic/scleral crescents (stretching of the optic disc)
-pigmented disc margins
-cilio-retinal vessels (hockey stick artery)
-tigroid/tessellated fundus (stripey)
-chorodial vessels
Why might there be difficulties is examining the fundus using direct ophthalmoscopy
-uncooperative patient
-high myope
-high astigmatism
-media opacity
-poor ophthalmoscope
-bright room
-small/constricted pupil (may require dilation)
Why does an ophthalmoscope have neutralising lenses
These ‘neutralise’ the refractive error of both the patient and the examiner so the fundus is visible to the examiner
