Unit 5 Flashcards
What is Schirmer’s test
To assess tear production
normal range of Schirmers test with or without anaesthetic
No anaesthetic: 15 mm (reflex tears)
Anaesthetic: 10 mm (basal tears)
What is exophthalmometry
Measuring the protrusion of the eye from the orbit (protopsis)
Why do Exophthalmometry
-Check for thyroid issues
-Trauma
-Orbital tumours
Normal range of exophthalmometry
12-20 mm
Normal Difference between both eyes is less than 2 mm
What is potential acuity testing for
Predicting a patient’s vision after cataract surgery
Two ways to test potential acuity
PAP: Potential acuity pinhole
PAM: Potential acuity meter (tiny snellen chart)
What is biometrics
“The measurement (as by ultrasound or MRI) of living tissue or bodily structures”
Systems used to produce measurements of structures within the eye
-Ultrasound
-Low coherence interferometry
-Optical laser interferometry
What can we measure with biometrics
-Axial length
-Corneal curvature
-Lens thickness
-Anterior chamber depth
-Anterior chamber angle
-Retinal thickness
-Corneal diameter
What is an A-scan
-Amplitude modulated
-One dimensional linear image with peaks
-A single beam at 10 to 12 MHz
-Measures the length of the eye and can be useful in diagnosing common sight disorders
-Determination of the power of intraocular lens needed for implant
Methods of a-scan
-Contact
-Immersion
What is a B-scan
-Brightness modulated
-2D image represented by a series of dots or multiple a-scans
-Uses multiple sound waves at either 10 MHz or 35 to 100 MHz
-For evaluating diseases in the posterior segment and orbit
What is low coherence interferometry
Uses near infrared light waves instead of sound to create a cross-section image of that eye
-non-contact
What is optical coherence tomography
Allows us to see the retina the optic nerve and the anterior segment
Tomography= Imaging by sections using some kind of penetrating wave
