Small Animal Ophthalmology (Self-Assessment Color Review)

243 Pages·2011·27.3 MB·English

by  Don A. Samuelson

Self-Assessment Color Review
Small Animal
Ophthalmology
Don A Samuelson
MS, PhD
Professor of Histology and Ophthalmology
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Florida, Gainesville, Florida, USA
Dennis E Brooks
DVM, PhD, Diplomate ACVO
Professor of Ophthalmology
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Florida, Gainesville, Florida, USA
MANSON PUBLISHING/THE VETERINARY PRESS
Dedication
We dedicate this work to ollr loved ones, who supported liS during the process of its
development. We especially dedicate it to our mothers, Laura Katrina Samuelson and
Betty Jane Brooks, who both passed on during that time.
Acknowledgements
The creation of this book is a test:lment, in part, to the sllccessful ophthalmology
program that was dl'veloped by Kirk N Gclatt well over 30 years ago at the University
of Florida. We, both, have been very fortunate to have been mentored by Kirk and to
have worked by his side along with many faculty, residents, and graduate students, who
have joined this program and been a part of our c\'cr growing ophthalmology family.
Speci;)1 thanks are extended to Pat Lewis, who prepared much of tht:' histology llsed in
the book, and to Ashley Beattie and Suzanna Lewis for their reviewing and editing of
this text.
Copyright 0 20 II Manson Publishing Ltd
ISBN: 978-1-84076-145-0
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Color reproo",·tion: Tenon & Polert Colollr Scanning Ltd, Hong Kong
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Preface
We have tried to create a book that provides a general review of small animal
ophthalmology in a case-based manner. To that end we have illustrated sevt"ral
examples for each of the mOTt" frequent ophthalmic conditions of dogs and cats that
arC' commonly presented to general veterinary practitioners. The differential diagnoses,
examination techniques, and therapies for these ocular conditions are discussed within
specific cases as well as separ:nely. While ophthalmic problems relate to dogs and cats
in similar and sometimes identical ways, there are a number of instances where this
does not occur. For that reason, we hav!." distinguished thl." canine cases from the feline
ones in our listing of the 'Classification of cases'. For more in-depth information on
differential diagnoses, examination techniques, and therapies offered in our work we
encourage the reader to refer to the latest edition of Kirk Gelau's Veterillary
Ophthalmology (see Suggested Further Reading List).
Don A Samuelson
Dennis E Brooks
Contributors
Kathleen P Barrie DVM, Diplomate ACVO
Gil Ben-Shlomo DVM, PhD
Sarah E Blackwood DVM
Dennis E Brooks DVM, PhD, Diplomate ACVO
Catherine M Nunnery DVM, Diplomate ACVO
Caryn E Plummer DVM, Diplol11at(> ACVO
Don A Samuelson MS, PhD
Avery A Woodworth DVM
Department of Sillall Animal Clinical Sciences, College of Veterinary Medicine
University of Florida, Gainesville, Florida, USA
Abbreviations
CT computed tomography
DNA deoxyribonucleic acid
EDTA ethylenediamine terra-acetic acid
MRI magnetic resonance imaging
NSAID nonstt'roidal anti-inflammatory drug
PCR polymer chain reaction
RNA ribonucleic acid
3
Suggested further reading
Gelate KN (2007) (cd) Veterillary Miller PE (CollSulting Editor), Tilley
Ophthalmology, 4th edn. Blackwell LP (Co-Editor), Smith FWK (Co
Publishing, Ames. Editor) (2005) The 5-Minllfe
Maggs OJ, Miller PE, Ofri R (2008) Veterillary COllslllt Canille alld
(cds) Slatter's Fundamentals of Felille Specialty Halldbook:
Veterinary Ophthalmology, 4th Ophthalmology. Wiley-Blackwell,
eda. Saunders Elsevier, St Louis. Hoboken.
Martin CL (2005) Ophthalmic Disease Stades FC, Wyman M, Boeve MH et
ill Veterillary Medicille, revised and al. (2007) Ophthalmology for the
updated edn 2010. Manson, Veterillary Practitioller, 2nd revised
London. and expanded edn. SchHitersche,
Hanover.
Classification of cases
Ciliary body 20, 40,47,48,83, 102, 191,195,202,205,214,216,242,
123,135,180,214 245,246,247
Conjunctivae 1,2,3,25,29,41,45,51, Lens 28,3 1,70,71,11O,11 1,131A,
6 1,68,80,92,94,101,107,108,112, 1318,132,137,142,143, 145,148,
114,121,181,187,204,227,223, 170,174,175, 197,239, 240,241,242
234,235 Miscellaneous 17, 44,52,119,138,139,
Cornea 2,8,10,12,16,18,23,24, 29, 144, 146, 154,156,178,204,224,
33,39, 41, 45,48,50,55,56,63,64, 230,244,249,250
65,71,80,81,86,87,89,90,91,93, Niclil,uing membrane 1,68,82,84,92,
94,95,96,97,98,99, 100, \03, 109, 139,21 1,223,235,236
111,112,114, \JJ, 142, 168, 171, PeriorbilaVperiocuiar 11,15,53,66,67,
176, 188,196,199,210,212,213,238 119,120,123,125,126, 127,128,
Diagnostic resls I, 26, 30, 42, 94, 103, 129, 130, 186, 200, 201, 218, 220,
104, 105,106,113,120,127,128, 221,222,226,228
151,158,168,206,229,237 Pupil 9,37, 40,47,84,132, 140,147, 182
Eyelids 6,14,18,25,32,38,46,57,58, RCiinalfundus 9, 19,20, 22, 27, 34, 35,
59,60, 68,69,100,115,1 16,117, 36,43, 49,54,62,66,67,74, 75,76,
118, 121,139,167,172,190,207, 77,78,79, 85,121, 122,123,126,149,
212,2 17,2 18,220,231,232,243 150, 151,152, 153,154, 156,157, 158,
Globe 5,10,48,68,88, 110, 111,124, 159, 160,161, 162,163,164,166,177,
125,126,169,184,185,194,201, 179, 183, 189, 192,193, 198,202,203,
209,2 15,225,248 208,209,219,250,251
Iris 7,10, 13,16,37,40, 47,55,56,72, Sclera 4,81,83, 179
73, 102, 123,132,133,134,135,136, Surgicallcchniques 70,98, 165, 186, 243
138,140,141,144,169,173,182, Vilreous 21,71,84, 155, 164
4
1,2: Questions
1 A nine-year-old domestic shorthaired cat was brought to the clinic for a
complaint of the cat's left nictitating membrane. The third eyelid conjunctiva of
this cat exhibited protrusion, chemosis, and hyperemia (l). Rose bengal stain has
been applied to the eye.
i. What does rose bengal stain evaluate?
ii. What are the differential diagnoses for the conjunctivitis in this cat?
2 This 12-week-old Boston Terrier was presented for a puppy wellness exam
ination. The owners explained that they were able to acquire the puppy for free
because she had 'funny eyes' (2). They wanted to know what was wrong with the
puppy's eyes.
i. What do you tell the owners?
ii. Does this condition affect vision?
iii. What can be done to resolve the condition in this puppy?
5
1,2:Answers
1 i. Tear film stability. The inner mucin layer of the tear film normally blocks
staining of the surface epithelial cells and stroma. If the mucin layer is absent, rose
bengal staining occurs. While it stains living cells, dead and degenerating cells, and
mucus, this stain may have a ability react with normal corneal
dose~dependent [0
and conjunctival epithelial cells. Rose bengal (dichloro-rctra-iodo-fluorescein) is
available in solution form or impregnated paper strip. A lower concentration
(0.5%) is often used, as higher concentrations (1.0% and greater) can be irritating.
ii. Herpesvirus, Chlamydophila, Mycoplasma, and bacrerial infection. Con
junctivitis often accompanies viral respiratory diseases in cats. Herpesvirus is the
major cause of respiratory disease with conjunctivitis in cats. Cats with chronic
conjunctivitis may also be feline immunodeficiency virus positive. Often, more than
one cat in a multi-cat household will be affected. Chemical and mechanical irritants
may also cause conjunctivitis. Foreign bodies are frequently incriminated. Plant,
upholstery, and carpet irritants may cause chemosis and conjunctivitis in cats.
Household cleaners and soaps have been suspected as causes of conjunctivitis in
cats. Lack of tear production is also a caust: of conjunctivitis in cats. Other less
common causes include hypersensitivity to topical ophthalmic preparatlons,
parasites, and mycmic infections.
2 i. This puppy has congenital strabismus. Snabismus refers to a deviation in
alignment of one globe in relation the other globe. h may be constam or
[0
intermittem. The nvo eyes may be crossed (esotropia), out-turned (exmropia) as in
this puppy, deviated up vertically (hyperopia), or deviated down vertically
(hypotropia).
ii. Binocular vision is an acquired reflex that normally develops early in life. The
developmem of binocular vision requires both eyes to have visual capability and to
be properly aligned. Similar retinal images must project onto corresponding retinal
areas of both eyes during the period of binocular vision development. Puppies with
congenital or early-onset snabismlls do not receive the essential visual retinal
stimulation for development of binocular vision and rims lack true stereopsis. The
two eyes fail focus on the same image point, and the brain ignores the input from
[0
the deviated eye, resulting in a form of vision loss termed amblyopia.
iii. Surgical correction of the strabismus by rectus muscle transposition can be
performed. Muscles can be weakened by moving the muscle insertion posteriorly or
strengthened by shortening the muscle or advancing the insertion site anteriorly;
alternatively, muscle insertions can be transposed different locations in order
[0 [0
alter the functional pull of the muscles. Nothing but observation was done in this
puppy and the strabismus
se1f~corrected.
6
3,4: Questions
3 A seven-year-old female Husky is
presented with a two-day history of
blindness. Over the past month her iris
color had changed from blue to brown
(due to uveitis) (3a). She also has nasal
depigmentation (3b) and retinal scarring
(3c).
i. What is the most likely diagnosis?
ii. What breeds of dog are predisposed
to this condition?
iii. What are the treatment options?
4 The owner of a seven-year-old
Norwegian Forest cat had recently
noticed a change in the color of her eat's
right eye (4). The irides of both eyes had
been normally a light blue in this nearly
albinotic individual. The iris of the right
eye, however, had changed during the
past week to a greenish-orange. The
distinctly pigmented margin around the
pupil had faded considerably. What are
the two main differential diagnoses of
iris color change?
7
3,4:Answers
3 i. Uveodermarologic syndrome (UDS). This syndrome in the dog is similar ro
Vogt-Koyanagi-Harada (VKH) syndrome in humans. This immune-mediated
disease against melanin is characterized by severe, bilateral pan uveitis and
hyporony, with secondary cataracrs, glaucoma, retinal detachmems, and blindness.
Iris and reTinal depigmemation, and poliosis/vitiligo of the face and muzzle are onen
noticed. Diagnosis is made from elinicallesions and breed of dog. A skin biopsy can
help ro confirm the condiTion.
ii. Originally described in the Akita, UDS has also been diagnosed in the Australian
Shepherd Dog, Beagle, Brazilian Fila, Chow Chow, Dachshund, Golden Retriever,
Irish SeHer, Old English Sheepdog, Saint Bernard, Samoyed, Shedand Sheepdog,
and Siberian Husky.
iii. The initial Therapy for this condition is immunosuppressive doses of oral
prednisone plus azathioprine or cyclophosphamide. Afrer five weeks tapering, oral
prednisone can begin. MOST dogs require a low dose of both azathioprine and
prednisone ro control the disease. Topical anti-inflammarories and aTropine are
used ro Treat the uveitis (see case 12). The eye is carefully monirored for develop
ment of secondary glaucoma. In this case the nose repigmented and The uveiTis
quieted following Therapy (3d).
4 Anterior uveitis and intraocular neoplasia. Eyes with anterior uveitis may also
exhibit ocular hyporony, aqueous flare, miosis, chemosis, hypopyon, keraTic
precipiTates, and/or synechiae formaTion. A complete physical and ocular exam
ination is importam in order ro provide diagnostic clues ro the eTiology of the
inflammation. Imraocular melanomas and lymphoma are common in the cat and
may also cause iris color change.
8
5,6: Questions
5 A spayed female dog
nine~year-old
was presemed with this unilateral eye
problem (Sa).
i. Describe the clinical signs.
Ii. What is your diagnosis?
iii. What are the possible causes?
6 This nine-year-old Labrador Retriever
was presented because of difficulty
eating and an enlarged left eye (6a).
There was epiphora and redness asso
ciated with the eye, and a corneal ulcer
was present. The right eye appeared
normal. A depigmented mass was
present behind the last molar tooth of
the exophthalmic side (6b).
i. What are the differential diagnoses?
ii. You discover that there is also a mass
in the caudal aspect of the hard palate.
What is the most likely diagnosis?
iii. How would you treat this condition?
IV. What is the likely prognosis?
9