Ocular Exam Tech/DX Flashcards
General concepts for exams
Examine at room lighting - palpate, retropulse globes
Examine under focal lighting - dim/darker conditions
Anterior segment exam tools
Trans Illuminator
Magnification
- head loupe
- direct ophthalmoscope - setting depends on goal
- otoscope w/out cone: 2-3x mag
Transilluminator use
Oblique illumination - apply at various angles NOT directly into the eye
Can highlight subtle corneal opacities, depth, contours of ocular structures
Coaxial illumination
Light aligned w observers line of sight, can highlight obstructing opacities in eye - set at 0 diopters
Work at arms length from patient
Difference between coaxial and oblique illumination
Co axial - light and line of sight are on the same axis
Oblique - any angle that’s not oblique, are on separate axis
Nuclear sclerosis vs cataract
Cataracts obstruct light - depends on degree
Nuclear sclerosis does not
Magnified ocular surface exam
Set diopter setting at 15 – 20D
• Move in towards area, like hand until lesion comes into focus
• Limitation is small surface area that can be visualized in
this manner - not great screening tool
Fundus exam
Determining cause of vision loss
- retinal degeneration
- retinal detachment
- optic nerve disease
Fundus exam - systemic disease
Can see affects on retina
- hypertension
- infectious disease
- neoplasia
Challenges of ocular exam
Takes time for developed technique
Wide variation within species and individuals
Requirement for pupillary dilation in learning stages
Tools and knowing how to use them
Direct vs indirect techniques
Direct - easy exam
Indirect - difficult exam but best screening field, image is upside down
Direct ophthalmoscope fundic exam
Set lens to 0, set focus on retina, adjust diopter focus as needed. Stay 2-3cm away from cornea
Use same side eye to examine the same eye - R/R, L/L
Easiest to perform with dilated eye
Image from direct ophthalmoscope
Highly magnified - Best opportunity for fine detail
– Significant magnification is usually unnecessary
• Difficult to evaluate entirety of fundus
– Especially the peripheral fundus
• Hard to isolate/localize lesions due to eye movements
Real image
• Image is in anatomical orientation
• Example: Direct gaze downwards to find lesion in lower retina
Indirect ophthalmoscope tools
Monocular indirect ophthalmoscopy
Employs handheld light source
Finoff transilluminator held adjacent to observers eye
Direct ophthalmoscope (look through at 0 Diopters)
Binocular indirect ophthalmoscope
Employs specialized headset
– Allows for stereoscopic image (better depth perception and evaluation of raised or depressed lesions)
– Frees both hands for manipulating lens and patient
Basic indirect technique
Use low level of illumination
1. Obtain tapetal reflection
2. Position indirect lens into path of light in front of patient’s eye to obtain fundic image
Lens distance from cornea depends on lens strength
- move towards /away form eye until fundus imagine fills entire lens. If iris or eyelids enters view = incorrect distance
Indirect image
Wide field of view - virtual imagine = upside down & reverse
Tapetum is dorsal but appears ventral in image
To track lesion that appears dorsal lateral in image, adjust to look ventral/medial = opposite direction
Rules for indirect ophthalmoscope
Always work at arms distance from patient
• Direct light beam in line (coaxial) with your eye - With monocular technique, hold light source beside your eye
• Hold lens perpendicular to light beam - Must maintain this when looking at different areas of retina
• Hold lens at proper distance from patient’s eye - Distance varies by lens diopter strength. Maintain hand contact with patient for stability of lens position
Indirect lens alignement
Lens should be help perpendicular to light beam - maintain this alignment when looking at different areas of retina
Indirect lens power
Field of view and magnification are inversely correlated
As mag goes up the field of view gets smaller
As mag goes down the field of view gets bigger
Tips for all forms of ophthalmoscopy
Retina is best viewed in a dark room
• Use lowest practical light intensity
• Appropriate restraint is very helpful
• Pharmacologic dilation whenever possible
– Use short acting agents such as 1% tropicamide
– Dilation is contraindicated if concerned about glaucoma /lens instability
Ophthalmic diagnostics
Schirmer tear test
Tonometry
Fluorescein stain
Schirmer tear test
Measures tear production • Insert in lower eyelid up to notch on strip (can pre-bend if desired)
• Leave in place 1 minute • Read immediately following
removal
- Measurements in mm/min
• Normal values vary by species
Topical fluorescein stain
By directly touching pre-moistened fluorescein strip to
conjunctiva
– create fluorescein solution in syringe and apply drop to ocular surface
• Useful if applying frequently during course of day
Use for topical fluorescein stain
Corneal ulcer detection** ulcer will highlight w stain
Evaluation nasolacrimal duct patency - dropper
Fluorescein stain light
Fluoresces under cobalt blue light - increases sensitivity to detect stain uptake
Tonometry
Measures Intraocular pressure
Measures in mmHg
Acceptable methods
- rebound (Tonovet)
- applanation (tonopet)
- indentation (schiotz)
Practice tips for Tonometry
Topical anesthetic for TonoPen and Schiotz, not for TonoVet – Minimize animal stress
– NO PRESSURE ON GLOBE
– Minimize jugular pressure
– Always measure both eyes
