Download First ask yourself “where is it” not “what is it”. Ophthalmic

First ask yourself “where is it” not “what is it”. Ophthalmic Examination – PART 1
Elizabeth A. Giuliano DVM, MS, DACVO
Associate Professor, University of Missouri
Columbia, MO, USA
Overview of the Issue
Ocular examinations can sometimes be intimidating when the practitioner is unsure of
the diagnosis. The goal of this lecture will be to help review techniques useful in the
localization of an ocular lesion, thereby helping to narrow down the possible differential
diagnosis and further hone the diagnostic work-up. Emphasis will be placed on the anterior
segment examination.
Objectives of the Presentation
1.
Provide an overview to the basic instrumentation, supplies and diagnostic
pharmaceuticals required for a complete ophthalmic exam
2.
Discuss the key components of the “minimum ophthalmic data base”
3.
Provide helpful tips to ensure success in performing the complete ophthalmology exam
Key Clinical Diagnostic Points
 Minimal equipment is necessary to perform a complete ophthalmic exam
 Always strive to acquire the “minimum ophthalmic data base” to best diagnose and treat
your ophthalmic patients. Rarely, an aspect of the complete ophthalmic exam will be
forfeited (example: tonometry should not be performed on an eye with a descemetocele
due to risk of globe rupture).
 Components of the minimum ophthalmic data base include: menace response, direct
and consensual pupillary light reflex, palpebral reflex, Schirmer tear test, fluorescein
stain, and tonometry
 Additional diagnostics typically performed in an awake patient include: conjunctival /
corneal cytology and/or culture and sensitivity, conjunctival biopsy, and nasolacrimal
flush.
Basic Instrumentation
A thorough ophthalmic examination may be performed with a minimum of diagnostic
instrumentation. The most basic instruments/equipment necessary for the small animal
practitioner include:
- magnifying source – (e.g. Optivisor loupe)
- power source – (e.g. Welch-Allyn (W-A) 3.5V halogen handle)
- focused light source – (e.g. Welch-Allyn Finoff transilluminator)
- direct ophthalmoscope head - attaches to W-A 3.5V handle or PanOptic
- 28-20 diopter condensing lens
- tonometer (e.g.:Tonopen or Tonovet)
- nasolacrimal cannula (or small catheter with stylet removed can be used)
- thumb forceps
- Instruments for cytology: scraping blade - spatula or surgical blade (clip-on end) or
microbrushes
More Advanced Ophthalmic Equipment
-handheld slit lamp (e.g. SL-15)
-binocular indirect ophthalmoscope
-operating microscope
-high resolution ocular ultrasound
Supplies and Diagnostic Pharmaceuticals
Consumable materials that should be readily available are:
- Schirmer tear test (STT) strips
- sterile fluorescein strips
- culturette swabs (mini-tip)
- cotton swabs
- sterile eye wash irrigating fluid or sterile saline
- dilating agent - 1% tropicamide (Mydriacyl)
- topical anesthetic solution - 0.5% proparacaine (e.g.Alcaine)
Components of the Anterior Segment Ocular Exam
The eye is unique in that most of its structures can be visualized and clinicopathologic
diagnoses frequently are possible from the complete ophthalmic exam. You will need to have
a basic knowledge of gross and histologic anatomy of the eye and orbit in order to make a
diagnosis and provide a prognosis. Minimal equipment is necessary to perform a complete
ophthalmic exam. The practitioner is encouraged to always strive to acquire the “minimum
ophthalmic data base” to best diagnose and treat his/her ophthalmic patients. Rarely, an
aspect of the complete ophthalmic exam will be forfeited (example: tonometry should not be
performed on an eye with a descemetocele due to risk of globe rupture). Components of the
minimum ophthalmic data base include: menace response, direct and consensual pupillary
light reflex, palpebral reflex, Schirmer tear test, fluorescein stain, and tonometry. Additional
diagnostics typically performed in an awake patient include: conjunctival / corneal cytology
and/or culture and sensitivity, conjunctival biopsy, and nasolacrimal flush.
The adnexa and ocular anterior segment can be thoroughly examined in a lighted room
with the aid of an examining light and source of magnification, such as the Opti-Visor loupe
with dial adjustable headband. The ocular posterior segment can best be evaluated by
ophthalmoscopy in a darkened room. Always examine both eyes even if only one seems
abnormal. If the eye is painful to the patient and there is danger of injuring the eye during
examination, or if the eye cannot be thoroughly examined, judicious use of chemical restraint is
recommended.
As with any other problem, a history is important to properly interpret your physical
exam findings. This should include establishing how long the client has had the patient.
Establish when and under what circumstances vision became impaired or ocular problems
began. The appearance of the eye, as perceived by the client, may give valuable clues as to
what came first when dealing with an entity such as cataract. I frequently like to begin my
ophthalmic examination by asking the client simply “what first made you think your pet was
having an eye problem?” Other questions might include: Does the patient see better under
any particular lighting arrangement? What type of lifestyle does your pet have (e.g. indoor only,
agility performer, etc) Did the patient's vision loss correspond with rearrangement of household
items or visiting an unfamiliar environment? Has there been a change in the general health of
the patient? Additional questions should be tailored to fit the particular situation at hand.
I recommend examining all patients initially from a distance. This will help the
practitioner determine if the problem is unilateral or bilateral (if it is an externally visible
problem). Observe the relationship of the globe to the orbit and eyelids, and to the other globe.
Ask yourself the following questions:
 What is the size of the eye - small, normal or enlarged?
 What is the position of the eye - protruding or sunken into the orbit?
 Is there a difference between the axes of the two eyes?
 Any evidence of periorbital swelling?
 Is there any ocular discharge and if so, what is the character of the discharge (serous,
mucoid, sanguineous)?
Use of a Transilluminator
The transilluminator powered by a 3.5V handle is used to closely inspect extraocular
structures including the lacrimal caruncle, the nasolacrimal puncta, the leading edge of the
third eyelids, the meibomian glands, and the limbus of each eye. Conjunctival vessels are
differentiated from episcleral (ciliary) vessels. Translucency of the cornea is determined.
Intraocular structures in the anterior segment of the eye may also be examined. The light is
directed obliquely across the anterior portion of the globe and the depth and clarity of the
anterior chamber is noted. The color and surface contour of the iris and the size and
symmetry of the pupillary openings are observed. Direct and consensual pupillary responses
are tested. Recall that the use of dilating agents will invalidate pupillary responses for several
hours. You may localize intraocular opacities by considering the posterior area of the lens
nucleus as the center of rotation of the eye. If an opacity appears to move with or in the same
direction of eye movement, then it is rostral or in front of the posterior area of the lens nucleus.
If an opacity appears to move against or in the opposite direction of eye movement, then it is
caudal or behind the posterior area of the lens nucleus. If an opacity does not appear to move
when the eye moves, then it is in the nuclear area. Direct the light through the pupils and
observe the fundic reflexes. The presence and color of tapetum will determine the color of the
fundus reflex. The lenses are normally translucent and allow reflected light to fill the pupil
spaces. In most animals the tapetal reflection is gold or blue-green. In atapetal animals the
reflection is red or dull grayish-blue. Opacities are frequently detectable by this technique
which is referred to as retroillumination. A partial or complete absence of a fundus reflex
indicates opacification involving one or more portions of the normally transparent parts of the
eye.
Pupillary Light Reflex
The direct pupillary response is done by simply shining a bright light into each eye. I find
it best to perform this test under standard exam room lighting (i.e., not with the lights off) in
order to also evaluate symmetry of the pupils without the complication that darkness would
inject through reduction of parasympathetic tone. However, it may be difficult to determine the
response in the non-stimulated eye because exam room lighting reflects off the cornea
preventing adequate visualization of the pupil. You can overcome this by one of the following
methods: (1) Dim or extinguish the exam room lights and stand back far enough so that you
can see both pupils via the fundus reflection when you look through the direct ophthalmoscope
set at ‘0’ diopters. Have an assistant shine a light first in one then the other eye while you
observe the response in the non-illuminated eye. (2) A more simple method does not require
an assistant or extinguishing of exam room lights. First establish that each eye has a direct
response. Then shine your light in the right eye. When the pupil constricts (or after a second or
two, if the pupil does not constrict), quickly swing your light to the left eye. If there had been a
constriction on the left side, the left pupil should still be in a constricted state if you have swung
the light quickly enough to the left eye. (If you were not quite quick enough, the left pupil will be
slightly dilated and will, if normal, constrict directly in response to your light.) Repeat the
procedure for the left eye. This is termed the swinging flashlight test. It is useful in identifying
unilateral pupillomotor problems. For example, if you are going from the right pupil to the left
pupil and the left pupil dilates rather than remaining constricted, this indicates a defect in the
left eye’s afferent branch of the pupillary light response pathway.
Other “tips” when performing a PLR: allow the patient to relax as much as possible.
High sympathetic tone can alter normal PLR results. Secondly, remember that prolonged
bright light stimulation into an eye is uncomfortable. Perform this test quickly and give your
patients a few seconds “rest” between direct PLR testing.
Corneal/Palpebral Reflex
This reflex involves trigeminal (fifth; sensory) and facial (seventh; motor) nerves - any
painful stimulus to or touching of cornea or eyelids leads to reflex closure of palpebral fissure
through action of orbicularis oculi muscle.
Menace response
You may see this sometimes referred to as the “blink reflex” and it involves optic
(second; afferent) and facial (seventh; motor) nerves. It is a “learned response” such that the
patient responds to sudden stimulation of visual system (such as foreign body moving toward
eye) by closure of palpebral fissure and sometimes, turning of head away from the stimulus. It
is learned, and therefore more appropriately referred to as a response (not a reflex).
Schirmer Tear Test
The Schirmer tear test I (STT) is a method of measuring basal and reflex tear
production in animals when deficient tear volume (aqueous component) is suspected. It is
performed by inserting a sterile filter paper strip into the lower, middle conjunctival fornix of
each eye. The strip is inserted and left in place for 60 seconds, then removed and the length
of the filter paper that has been moistened by the tear fluid is measured on a mm scale.
Normal values for dogs are 15 mm/min or greater while normal values in cats may be
considerably less, possibly as low as 5 mm/min. STT measurements should be made at the
beginning of the examination prior to application of topical agents or to any manipulation of
ocular tissues.
Conjunctival-Corneal Cultures & Cytology
Cultures of the ocular surface are necessary for definitive diagnosis of severe, chronic,
or nonresponsive infections. For conjunctival culture, the lower eyelid is everted and a sterile
cotton or rayon-tipped swab in applied to the ventral fornix in front of the third eyelid. To insure
adequate tissue contact the swab tip is gently pressed against the conjunctiva and rotated so
as to slightly elevate the conjunctival tissue. The swab is then removed and inserted into the
transport tube which contains an ampule of transport media. The ampule is ruptured and the
sample is sent to the laboratory as soon as possible. Some specimens may be refrigerated
depending upon the type of culture, i.e., the organism suspected. For corneal cultures, the
swab is applied to the margin of the ulcerated or necrotic lesion. Ideally, cultures should be
taken prior to instillation of topical agents, including topical anesthetic. However, in cases of
corneal ulcers, one drop of topical anesthesia will aid patient compliance and has been shown
to have minimal effects on culture results. Contamination is avoided by being cautious not to
touch the skin or hair with the swab tip.
Cytologic evaluation of ocular surface cells may be quite helpful in making a definitive
diagnosis in cases of inflammatory or neoplastic lesions. For cytology, spatula collection or
use of cytologic microbrushes are two commonly used techniques for removal of surface cells
at affected sites. Samples for conjunctival or corneal cytology are collected after discharges
are cleansed from the eye and topical anesthetic has been instilled. Several drops of topical
anesthetic solution are instilled over a 2-minute period (e.g., 1 drop every 30 seconds).
Platinum spatulas are specifically designed for ocular use, however, less expensive spatulas,
such as pharmaceutical or chemical spatulas or the blunt, snap-on end of a surgical blade,
may also be used. Scrapings are collected by placing the spatula or blade (blunt end)
perpendicular to the surface, by pressing firmly against the tissue, and then pulling along the
surface. Samples collected from scrapings should be gently blotted onto glass slides and air
dried. A minimum of three slides should be prepared, one for a modified Wright's stain, one for
a Gram's stain, and the remaining one for special staining if needed. Cytologic findings of
greatest diagnostic interest are the presence of inflammatory or neoplastic cells or the
presence of microorganisms.
Fluorescein Staining
Fluorescein dye is used diagnostically in veterinary ophthalmology for a number of
reasons. The most common and important reason for placing fluorescein stain onto the eye is
to detect a corneal ulcer. Recall that the corneal stroma is hydrophilic and, therefore, the
water soluble fluorescein has a marked affinity for exposed stromal tissue. An area of positive
staining will be noted by a bright yellow-gold appearance under room light conditions or using
a focal white light. A cobalt blue filter on the tip of a hand-held transilluminator or an ultraviolet
(UV) light will excite the fluorescein and any area of positive staining will appear bright green.
Keep in mind that fluorescein does not stain epithelial surfaces or Descemet's membrane.
Fluorescein may also be used to determine patency of the nasolacrimal (NL) drainage ducts
(Jones test). Open the package of an individually wrapped, single, fluorescein strip and
withdraw the sterile strip. Place a drop of diluent (sterile eye wash or sterile saline) onto the
end of a sterile, individually packaged, fluorescein strip. As a bolus of stained fluid pools on
the end of the strip, instill one drop of stain into each eye. Do not allow the strip to touch the
surface of the cornea, or you may cause a corneal ulcer. Apply a cotton swab to the medial
canthus, lower the animal's head slightly and flush the eye with diluent. Gently blot the medial
canthus with a cotton swab to remove excess fluid. The eye is scanned with a focused light
(with or without a cobalt filter or UV light). A short time later, usually in 3-5 minutes, the nares
are inspected using the focused light to determine if fluorescein has passed through the
nasolacrimal ducts. If dye has not drained into the nostrils by 5-10 minutes after instillation,
obstruction of the duct is suspected and NL irrigation may be indicated.
Nasolacrimal Irrigation
An irrigating cannula, attached to a 3cc or 5cc syringe containing sterile eye wash or
saline, is inserted into the upper and then lower punctal openings of each eye following
administration of topical anesthesia. Shortly after fluid is injected into the ducts it should be
seen flowing from the nostrils indicating patency of the drainage system. If fluid flows without
resistance but is not observed exiting the nares, drainage into the nasopharynx is probable
and the animal is observed for swallowing. If resistance is encountered to attempts at
irrigation, an obstruction is probably present. Continued gentle pressure may flush out minor
obstructions. Excessive pressure should be avoided so that the duct system is not further
damaged. When the puncta are imperforate in dogs, retrograde irrigation may be attempted
from the nasal opening. However, this is difficult to achieve especially in small dogs or cats.
Tonometry
Intraocular pressure measurement, or tonometry, is important for diagnosing glaucoma
(elevated pressure) and uveitis (low pressure) and in assessing response to therapy when
treating these conditions. In small animals, the hand-held Schiotz tonometer provides an
effective and affordable means of measuring the intraocular pressure, however is rarely used
for various reasons. Applanation tonometry (Tonopen) provides accurate and reproducible
intraocular pressure readings in veterinary patients and is becoming increasingly used in
general practice. Applanation tonometers have several advantages over the Schiotz
tonometer. They are highly accurate, their readings are less affected by corneal disease, they
can be used to measure intraocular pressure in vertically as well as horizontally positioned
corneas, and are very easy to use, making them the instrument of choice for measuring
intraocular pressure in domestic animals. The TonoVet is a newer, handheld veterinary
tonometer which allows measurement typically without anesthetic. With TonoVet, a very light
probe is used to make momentary contact with the cornea.
Ophthalmoscopy – see also notes on Exam Part 2
Either direct or indirect ophthalmoscopy may be used to examine the posterior portion
of the eye, i.e., the vitreous and fundus. The monocular direct ophthalmoscope is routinely
available for use in general practice for examining the back of the eye. Pharmacologic pupillary
dilatation is needed to adequately examine all intraocular structures deep to the iris (recall,
pharmacologic dilation is contra-indicated in patients with glaucoma). Generally, 1%
tropicamide is used in in most species for routine mydriasis; it is a synthetic atropine derivative
and acts by blocking the use of acetylcholine, therefore blocks parasympathetic action and
pupil dilates due to sympathetic tone. The pupil dilates in about 15 minutes in small animals,
(20-25 minutes in large animals) and will remain dilated for approximately 4-8 hours.
There are dials on the direct ophthalmoscope head piece – one dial will control the size
and shape of the light beam and another will control the focal point of the light beam. The
horizontal dial is set to project a large circular white light beam and the vertical dial is adjusted
to focus on the structure(s) of interest, (e.g., start at 0 for viewing the fundus). By adjusting the
focusing distance of the direct ophthalmoscope, the examiner may use the instrument to
examine all visible intraocular structures. Its most common use is in examination of the
posterior portion of the globe. When the vertical dial is set on 0, subtracting diopters (i.e.,-1,2,-3, etc.) moves the focal point away from the viewer. Conversely, when diopters are added
(e.g., +1,+2,+3, etc.) the focal distance is brought closer to the viewer. The vitreous should be
in focus when the diopter dial is set between +6 to 0 for most animals and the fundus is in
focus between 0 and -2 diopters. Note: if the examiner normally wears corrective eyewear,
and removes his/her glasses when performing direct ophthalmoscopy, the refractive power of
the examiner will need to be adjusted for (thus, the diopter power needed to achieve focus for
various ocular structures may vary slightly from person to person).
Indirect ophthalmoscopy involves using a focused light and a condensing lens (typically
20-28 diopters in small animal) to view the fundus. A head-mounted light source combined
with a set of prisms may be used and provides the viewer with a binocular view. A hand-held
light may also be used. A Finoff transilluminator is recommended as a focal light source for
performing monocular indirect ophthalmoscopy. The vitreous is examined for congenital
remnants (retained hyaloid structures) and other opacities (degenerative materials,
hemorrhage or exudates).
Examination of the fundus involves studying the optic disc (papilla), retinal vessels,
tapetal fundus (tapetum), and nontapetal fundus (nontapetum). Fundus examination should
begin by identifying the optic disc and by evaluating its size and shape. In dogs and
ruminants, a beige, irregular, fluffy margin to the optic disc is a frequent finding indicating lipid
covering (myelination) of the nerve fibers (axons) entering the optic nerve. In cats, because of
less myelin, the disc margin is usually sharper and more distinct. The shape, location, and
vascular pattern of the optic disc and the appearance of the fundus vary considerably among
species and individual animals. In dogs the disc may be round or irregular and may occur in
the colored (tapetum), dark (nontapetal), or junctional area. Three or four veins return to the
disc in dogs and frequently join together (anastomose) in the central area of the nerve. In cats,
the disc is smaller than in dogs and is characteristically circular. The veins enter the disc at
the periphery and no anastomosis occurs in cats. Fewer retinal arterioles are seen in cats as
compared to dogs. The tapetum, the upper, brightly-colored portion of the fundus, is usually
triangular in dogs and cats. The color of the fundus is quite variable from animal to animal and
generally reflects the tapetal color with yellow, green, or blue-green most commonly noted.
The tapetum may be incomplete or totally absent in animals with light haircoat color (color
dilution or subalbinism). Affected animals may have a blue or blue-brown iris and may lack full
fundus pigmentation. Atapetal areas of the fundus may appear orange or red reflecting the
deeper vasculature of the eye. The nontapetum is usually brown or black, however, reddish,
or light gray nontapetal areas are often seen in color-dilute animals. Abnormal funduscopic
findings of the optic disc include a small disc (hypoplasia; micropapilla), elevation
(papilledema), depression (cupping), degeneration (atrophy), and vascular changes (e.g.,
congestion, attenuation, or hemorrhages). The tapetal fundus is evaluated for clarity,
coloration, pigmentation, and integrity of the retinal vessels. The nontapetal fundus is studied
primarily for uniformity of pigmentation. Both tapetal and nontapetal areas are assessed for
retinal elevations or detachments, hemorrhages, degenerations, disorganization (dysplasia), or
sclera defects (colobomata).
Summary Including 5 KEY “TAKE HOME” POINTS:
 When presented with any ophthalmic abnormality, concern for the patient’s vision and
ocular comfort should guide the practitioner’s diagnostic and therapeutic plan
 The patient should be examined first at a distance, and then at eye level.




A room with controlled lighting is ideal for the small animal ophthalmic exam. At a
minimum, a room that can be completely darkened to permit accurate examination of
intraocular structures is essential.
The complete ophthalmic exam with its “minimal ophthalmic data” should be acquired
during all ophthalmic examinations, almost without exception.
Components of the minimum ophthalmic data base include: menace response, direct
and consensual pupillary light reflex, palpebral reflex, Schirmer tear test, fluorescein
stain, and tonometry
Additional ocular diagnostic procedures routinely performed by the general practitioner
include nasolacrimal flushing, conjunctival/corneal swabs for cytology and culture, and
conjunctival biopsy.
Key Drug
Drug Class
Tropicamide
Parasympatho
-lytic,
short-acting
mydriatic
Proparacaine
Depolarizing
topical ocular
anesthetic
Dose
Range
N/A
Frequency Route
N/A
1 drop
References available upon request
1 drop
Indications
Topically to To achieve pupillary
corneal
dilation in a
surface
normotensive eye
for complete
posterior segment
examination
Topically to Prior to tonometry or
corneal
ocular cytology
surface