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Volume 27 No 1, April 2009 A Publication of the Center for Equine Health, UC Davis School of Veterinary Medicine

The Equine Eye

INSIDE THIS ISSUE

Directors Message ..................2

Eye Problems in Horses ........... 4

Traumatic Injuries ...................5

Corneal Disorders ..................5Uveitis/Moon Blindness............ 6

Cancer ..................................7

Cataracts ................................7

Case Study from the VMTH .. ... 8

Handling Eye Injuries ...............9

Ophthalmology Service .. ...... 10

Tribute to Dr. Wheat .. ........... 10

Cataracts in Foals .. ............... 11

Dr. OBrien Honored .. .......... 11

Help for Unwanted Horses .. .. 12

Continued on page 3

An animal will always look for a persons intentions by looking themright in the eyes.

Rabbits run, possums playdead, chameleons changecolor and skunks spray.

Other animals have horns or claws

to fight off predators. Mobbingbehavior is common in birds and isusually done to protect the youngin social colonies. While survivaltechniques vary among animals,what many have in common arehighly developed senses of sight,smell, or hearing to detect dangerand escape.

Unlike other large prey species,

horses do not have antlers, horns orcloven hooves with which to defendthemselves. Instead, they have anexceptional ability to see and spotthe movement of any potential

predator. Horses havesurvived by using a standarddefense mechanism foranimals in open grasslands

and prairies: they frequentlyscan and monitor theirsurroundings to avoid attackby spotting a predatorbefore it reaches a criticaldistance.

While most horses todayare domesticated and donot have a constant need tosafeguard their survival, they

are expected to performin ways that require anunnatural demand on theirvisual system. It seems onlyfair then that we becomepartners in the effective useof their eyes and learn howtheir visual system can affectbehavior. For example, how doesthe lateral placement of a horseseyes affect its vision?

Visual perspective/field of view.The lateral placement of the eyes,more to the side of the head thanto the front, combined with ahorizontally elongated, roughlyrectangular pupil, provides thehorse with the ability to see a verybroad field of landscape, muchlike a cameras wide-angle lens. Infact, horses are capable of seeingalmost 360 degrees around with

monocular vision, where each eyeis used separately. This extensivevisual field makes it difficult fora predator or a human handler to

sneak up on a horse. The widerange, however, has two blindspots or areas where the horsecannot see. The first is directly infront of the face, in a cone-shapedarea that comes to a point about3 feet in front of the horse. Thesecond area is right behind thehead, in an area that extends overthe horses back and behind the


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Volume 27, Number 1 -April 2009

UC Davis Center for Equine Health

2 - The Horse Report

DIRECTORS MESSAGE Best Results Through Early Intervention

Dr. Gregory L. Ferraro

Few would argue theimportance of a pair ofhealthy, well-functioning

eyes to the well being andperformance of their horse.Indeed, unimpaired sight is asimportant to the horse as it isto any other animal, includinghuman. Yet few people have agood understanding of how thehorses eye functions or howtheir vision differs from that ofour own.

Infections of or injuries to thehorses eye always have thepotential to pose serious risk totheir visual capacity. Severeinsults can result in permanentdamage very quickly, and minorincidents left unattended canprogress swiftly into seriousthreats. Yet again, few horse

owners have the ability torecognize and properly respondto those minor problems.

Of all the illnesses and injuriesthat can befall our belovedhorses, we are generally theleast prepared to deal with thoserelated to the eye. While wecan recognize the signs of colic,

we are likely to not notice thedevelopment of a corneal ulcerin the eye until the conditionhas progressed to the stage ofsignificant pain and cornealdamage. Many experiencedhorse owners can treat and carefor minor cuts and abrasionsthemselves and have a good ideaof when those acute injuries aresevere enough to require theattention of a veterinarian, buttoo many will have trouble inassessing both the severity of aneye injury and when veterinary

intervention is required.

For that reason, this issue ofThe Horse Reportprovides someinformation intended to help youassess equine ophthalmologicproblems. It provides adescription of the basic anatomyand function of the horses eyeas well as some common butpotentially serious problems.We hope this will help youmore quickly recognize anyabnormalities that may appear inthe eye of your horse and provideguidance as to what type ofcondition you may be looking at.

You will notice that we areproviding very little informationabout how to treat theseconditions. There is a very goodreason for that. Basically, it is

because you are not qualifiedto treat them! As a long-timeequine practitioner, I can tell youin all honesty that if your horseseye has a problem that you areable to recognize with your ownnaked and untrained eyes, thenyou should call your veterinarianimmediately. If you follow thisone bit of advice, you will have

taken the correct course of action99% of the time.

If your horse has a painful andwatering eye, dont wait a coupleof days to see if it gets better onits own, and definitely do nottreat it with the contents of sometube of medication left over fromthe treatment of another horse,five years previously.

If you see something growingon the globe of your horses eyeor some foreign object sticking

out of the region of his eyesocket, dont be a hero. Callyour veterinarian. Remember,discretion is the better part ofvalor. Dont do somethingyou will regret later. In allconditions related to the eye andits surrounding structures, thebest results are always obtainedthrough early intervention bytrained and experienced equineveterinarians. Sunday-morningophthalmologists need not apply!

Trust me on this one, readwhat we have written here butuse it only as a means to knowwhen you are in trouble, not asa license to practice. We wantyou to be informed and educatedin all forms of equine healthcare, but part of that learningexperience is to recognize

your limitations. There is nomore appropriate arena for theteachings of Dirty Harry thanmedical ophthalmology.


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The Horse Report - 3Volume 27, Number 1 - April 2009


The Equine EyeContinued from page 1

Continued on page 4

tail. Thus, as a horse jumps anobstacle, the obstacle brieflydisappears from sight just beforethe horse takes off.

Depth perception. The tradeoffto having monocular vision isthat a horses depth perceptionis somewhat more limited thana humans. The placement ofthe horses eyes decreases thepossible range ofbinocular vision(using both eyes at the sametime). Horses use their binocularvision by looking straight at anobject, raising the head when

looking at a distant predator orfocusing on an obstacle to jump.To use binocular vision on acloser object near the ground,such as a snake or threat to itsfeet, a horse will drop its noseand look downward with theneck somewhat arched. Thus, ahorse will raise or lower its headto increase its range of binocularvision. Riders of jumpers allow

their horse to raise its head a fewstrides before a jump so it canassess the jump and the propertake-off spot.

Sensitivity to light. Horses, likehumans, must adapt to differentlight intensities varying from thedimmest star to bright sunlighton snow. One mechanism foradjusting to this wide rangeis to switch back and forth

between two different types ofphotoreceptors: the rods andcones located in the retina ofthe eye, each of which has beenoptimized to perform best atdifferent ends of the intensityspectrum. Rod receptors are theprimary receptors used when thelight levels range from virtuallycomplete darkness to those

found at dawn and twilight.Horses are well endowed witha high proportion of rod tocone photoreceptorsabout 20million rods to 1 million cones,which makes them sensitive tolight and gives them extremely

good night vision. Moreover, alayer of tissue in the eye of manyanimals, called the tapetumlucidum (see Anatomy of the Eye

below), is thought to function toreflect light back into the retina,thereby enhancing vision in low-light conditions such as at night.

In addition to these photo-receptors and other mechanismsfor adjusting to light, the horsehas one of the largest eyes

among land mammals, whichallows more light to enter theeye. Admission of light to theeye is further improved by thehorizontal elongation of thecornea and pupil and by thepupils ability to dilate to an areasix times larger than that of ahuman pupil.

Practically speaking, horsestend to have better vision onslightly cloudy days than onbright, sunny days. On the otherhand, they are less able to adjustto sudden changes of light, suchas when moving from a bright

day into a dark barn. This shouldbe taken into considerationduring training, because certaintasks such as loading into a trailermay frighten a horse simplybecause he cannot see. It is alsoimportant in riding, becausequickly moving from light to darkor vice versa will temporarilyblind the horse and make itdifficult for him to judge what isin front of him.

Sensitivity to motion. Horsesare very sensitive to motion,because motion is usuallythe first alert that a predatoris approaching. The horsesretinathe light-sensitivetissue at the back of the eyeisrichly endowed with motion-detecting cells known as rods,evidence that the horses eyes

are optimally constructed andpositioned for its survival.

Anatomy of the Eye

The equine eye is similar tothe eye of most mammalianspecies. Essentially a piece ofbrain tissuethe retinahasbeen brought outside thebrain and placed inside a tough,protective structure known as theglobe (the eyeball). The globe isconstructed in such a way thatan optically clear and focusablepathway is provided, wherebylight rays from the outside worldpass into the globe and reachthe light-sensitive retina. In turn,the retina transmits its perceived


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information via the optic nerve to the finalprocessing unit, the brain, where visual perceptionsare converted into images.

The eyeball is protected by eyelids, comprised oftwo folds of skin and muscle just like the humaneye. The skin has many blood vessels so thatabrasions and lacerations that are properly treatedheal well and are resistant to infection. The eyelidmuscles are quite strong and can be opened orclosed at will. Hence, examination of the equineeye often requires sedation and nerve blocks. Likemost other mammalian species, the horse has athird eyelid, which is a T-shaped cartilage coveredwith a transparent mucous membrane known as theconjunctiva.

As shown in the above illustration, the corneais part of the fibrous outer layer of the eye, whichserves to protect the intraocular contents. Thecornea is transparent and is involved in transmittingand refracting (bending) light into the eye.Although it is made up of living cells, the corneahas few or no blood vessels. The surface corneareceives its nutrition from tears, while the backportion is nourished by a clear fluid called the

aqueous humor, which is normally present in thefront chamber of the eye.

The sclera, like the cornea, is made up primarilyof collagen fibers. It is part of the outer fibrouslayer of the eye and functions to protect the interiorof the eye. The iris and ciliary body, part of themiddle vascular layer of the eye, perform a numberof functions. The iris contains muscles that controlthe size of the pupil, which in turn controls the


amount of light that enters the eye. The ciliarybody produces the clear aqueous humor thatnourishes the front chamber of the eye. It alsocontains the muscles that allow for focus on bothdistant and close objects. This function in horses isrelatively poorly developed.

The lens sits directly behind the iris and functionsto refract light in order to produce a focused imageon the retina. Like the cornea, it has no bloodsupply but is nourished by the aqueous humor.The choroid is part of the middle vascular layer ofthe eye and helps provide nutrition to the retina. Inthe innermost portion of the choroid is the tapetumlucidum, a layer of tissue that is thought to functionto enhance low-light vision by reflecting light backinto the retina.

The retina is made up of nervous tissue andfunctions to transform light into a neurologicimpulse. Axons that originate from the retinaaxons are a long fiber of a nerve cell (a neuron) thatact somewhat like fiber-optic cables carrying anoutgoing messagecome together at the optic disk,where they leave the eye as the optic nerve. Theoptic nerve takes the neurologic message from theretina to the brain.

Eye Problems in Horses

Horses respond to eye discomfort much the sameas people. The eyelids may become swollen, theeyes may become reddened, and there may beexcessive tearing. The horse may also squint orblink constantly. Excessive rubbing of the eye ona post or foreleg may also indicate an underlyingproblem. If any of these signs occur, a veterinarianshould be consulted for diagnosis and treatment.

One feature of eye disease is that relativelyminor problems initially present with the samesigns as more severe problems. Therefore, allcases of suspected eye problems should receivethe attention of a veterinarian. As with virtually allother disease processes, the chances of successfultreatment of these problems rely heavily on earlydetection. This principle is even more critical witheye disease.

The five most common eye problems in horsesseen at UC Davis are:

Tapetal area

Cornea

Iris

Lens

Sclera

Choroid

Optic disk

Optic nerve

Corpora nigra

Ciliary body

Retina


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Traumatic injuries Corneal disorders Inflammation inside the eye

(uveitis) Cancer on or around the eye Cataracts

Traumatic Injuries

Horses can sustain a widerange of traumatic injuries totheir eyes and related structures.These can vary in severity fromsimple abrasions of the eyelidsthat may be treated in a firstaid manner to full thicknesslacerations of the eyelids orcornea. This latter categoryusually presents with suddensquinting and discharge in theform of excess tearing, mucousor blood. All of these should beconsidered an emergency andrequire the immediate attentionof a veterinarian. The long-term prognosis depends on thestructures injured.

Eyelid lacerations arefrequently obvious because the

affected lid is often hanging looseand there is a moderate amountof blood on the face around theeyelid. Prompt and meticulousrepair by a veterinarian isessential in restoring eyelidfunction (including tear filmdistribution) and protecting theunderlying cornea from exposure.It is recommended that horsesreceive tetanus prophylaxis andtopical and systemic antibiotics

to prevent infection.

Corneal lacerations areoften less apparent becausethe only clinical sign may beintense squinting. Horses withcorneal lacerations will usuallyvigorously resist any attempt todetermine the cause of the pain.A veterinarian should assess the

extent of the damage by use ofsedation and nerve blocks ofthe eyelid muscles. Frequentlysuch injuries can be repairedby a veterinarian, althoughhe/she may advise referral to a

veterinary ophthalmologist.

Foreign objects such as plantmaterial, dust, sand or ash maybecome lodged under a horseseyelids. If the horse will allow it,flushing the debris with water orsaline solution may be helpful,but a veterinarian should stillexamine the eye for any furtherdamage since the debris canscratch the cornea and cause acorneal ulcer.

If a foreign object such as apiece of wood has pierced aneyelid and become embedded,you can remove it but followup with a full eye examinationwith a veterinarian to determinewhether further damage hasoccurred from splinters. Ifthe eyeball itself has a foreign

object embedded in it, DONOT REMOVE IT. Seekimmediate veterinary attentionas microsurgery may be requiredto remove the object and savethe eye. Ophthalmologists atUC Davis have successfullyremoved foreign objects fromeyes using very fine microsurgicalinstruments. Preventing infection

is another key element for savingan injured eye, and researchersat UC Davis have developedeffective ways to administereye medications and antibioticsevery few hours using indwellingmedicinal delivery systems.

Corneal Disorders

By far the most commoncorneal problem in horses iscorneal ulceration. This isa condition where the mostsuperficial cells of the corneaare abraded away. Likemost eye problems, this willinitially manifest as a suddenlypainful eye with excessivetearing. Corneal ulcers requireimmediate care by a veterinarianas they have the potential toworsen. Because the corneadoes not have blood vesselsrunning through it to help clearan infection, the eye is moresusceptible to infection frombacteria and fungus. Thesesecondary infections can causeserious problems and complicate

healing, which may result in amelting ulcer. Signs associatedwith an infected corneal ulcerinclude a creamy color or

This photo shows a severe lacera-tion of the upper eyelid. Eyelidlacerations usually heal well if theyare repaired soon after injury.

Superficial corneal ulcer. If caughtearly and treated correctly, these willusually heal quickly.

Continued on page 6


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melting appearance to the surfaceof the eye. Melting ulcers are aserious threat to eye survival andrequire intensive treatment by a

veterinarian.

A minor wound to the corneamay occur and appear to havehealed, but if an infection isintroduced into the deeper

layers of the cornea, a cornealabscess may develop. Again,this is a serious condition thatrequires immediate treatment bya veterinarian.

Less frequently, horses candevelop corneal inflammation,which tends to be intermittentand of variable severity. There

are many theories about thepossible causes of this typeof inflammation, includingautoimmune conditions andherpesvirus infection. UC Davisresearchers are currently studyingherpesvirus as a potential cause

of this type of unexplainedcorneal inflammation.

Inflammation Inside the Eye(Uveitis)

The most common cause ofblindness in horses is a diseaseknown to veterinarians as equinerecurrent uveitis (ERU). Othercommon names for this conditioninclude moon blindness andperiodic ophthalmia.

As the name suggests, ERUis characterized by recurrentepisodes of intraocularinflammation. Signs of anacute ERU attack includesquinting, redness, cloudinessand tearing. The severity of thesigns and the frequency of theattacks vary among individual

horses. Blindness results fromcataracts, glaucoma and retinaldegeneration. It is not one attack

that results in blindness, butthe cumulative effects of manyattacks.

The causes associated

with ERU are not completelyunderstood. The disease itselfis an autoimmune condition,but various other factors may beinvolved, such as leptospirosis,an infectious disease caused by aparticular type of bacteria calleda spirochete transmitted by ratsas well as by skunks, opossums,raccoons, foxes, and othervermin.

The therapeutic approach tomanaging ERU is to aggressivelytreat acute attacks and alsominimize the frequency andseverity of recurrences. Asmentioned above, any horsewith a suddenly painful, tearyeye should receive immediateattention from a veterinarianwho can then make a definitivediagnosis and initiate appropriate

treatment. New methods usedby veterinary ophthalmologistto treat ERU involve theimplantation of medicatedwafers or injections ofmedication into the back of theeye. These anti-inflammatorydrugs are then absorbed slowlyover the course of years.


Infected corneal ulcer. Noteaccumulation of white blood cellswithin the cornea.

Melting corneal ulcer. Notedegraded area. This ulcer couldperforate at any time and is a trueemergency.

Active episode of equine recurrentuveitis. Note the redness to theconjunctiva, excess tearing, and hazyappearance.

End stage equine recurrent uveitis.Note extensive corneal scarring.


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Cancer

By far the most commonocular/periocular cancer seenin horses is squamous cellcarcinoma. These tumorstypically occur in one of three

locations: on the surface of theeye, on the third eyelid, or withinthe eyelid. These masses areoften readily visible and have awart-like appearance.

Treatment of squamous cellcarcinoma on the surface of the

eye usually involves referral toan ophthalmologist. In additionto removing the mass, sometype of freezing (cryotherapy)or radiation treatment is usuallyperformed. If the carcinoma ison the third eyelid, it is usuallytreated by surgical removal ofthe entire third eyelid. Manygeneral practitioners perform thisprocedure.

Squamous cell carcinomawithin the eyelid itself is oftenthe most challenging locationbecause the tumors are often notnoticed in this location until theyare large. Treatment consistsof surgical removal and sometype of added treatment such aschemotherapy.

Other types of cancer suchas sarcoids and melanomas,which are common throughoutthe body, can also affect theeyes and interfere with eyefunction. In most instances, atumor may begin as a small area

of roughened eyelid or a smallbump. If diagnosed early, anumber of treatment methodsmay be used.

Note that when eyelid tumorsare found, it is important toexamine the rest of the body forthe presence of similar tumors.

Cataracts

The lens is a somewhatflattened, transparent, flexibledisc consisting of layers of lensfibers. The lens sits behind theiris and helps focus the imagesonto the retina. A diseased lensusually responds by becomingopaque; the opacity (or cataract)may be localized or diffuse.Cataracts are often progressive in

nature and result in serious visualloss over time. The affected lenscan be removed.

Cataracts can form secondaryto equine recurrent uveitis (ERU)as described above. They can

be treated with surgery, butbecause the cataract has formedas a result of months or years ofintraocular inflammation, thesuccess rates are usually not high.

Horses can be born withcataracts due to developmentalor heritable causes. Congenitalcataracts in newborn foals areespecially amenable to surgicalremoval. Veterinary attention

should be sought as soon aspossible. Signs include a milky-appearing pupil or evidence ofimpaired vision (the foal staysvery close to the mare, stumbles,or is reluctant to move). Oncethe lens is removed, the horsewill be far-sighted (not able to seethings up close), but many go onto live productive lives. v

Squamous cell carcinoma on theeye. Note the pink growth on the

left side of the photo.

The eye is an intricate and delicate organ. In all conditions related to the eyeand its surrounding structures, the best results are always obtained through acooperative effort of observant horse owner and experienced equine veteri-narian.


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Early Recognition of a Problem Saves Teeklas Eye

O

bservant owners and quick-acting referring veterinarians arevital elements to providing a successful outcome to a horse with

a serious problem affecting the eye. This principle was once againdemonstrated one morning last summer when the owner of Teekla, a9-year-old Friesian gelding, removed the horses fly mask and noticedhe was squinting and tearing out of his left eye. She immediately calledTeeklas veterinarian who realized the seriousness of Teeklas eyeproblem and referred him at once to the UC Davis Veterinary MedicalTeaching Hospital.

At UC Davis, Teekla was examined byophthalmologist Dr. Steven Hollingsworth,who determined that the horse had an

infected corneal ulcer characterized bya melting component. This meltingappearance is a particularly worrisome

clinical sign because it means that the cornea could rupture at any time,allowing the infectious organisms to invade the inside of the eye. Whileit is possible to save an eye that has ruptured, the prognosis is significantlymore grave.

Teekla was scheduled for emergency surgery and, within 5 or 6 hours of hisowners first noticing a problem, was on the operating table. The specificsurgical procedure performed on Teeklas melting corneal ulcer was apedicle conjunctival graft. This technique involves dissecting a finger-

shaped strip of the thin membrane that covers the conjunctiva (the whitepart of the eye). The degraded area of cornea is then trimmed off and thegraft is sutured directly onto the corneal defect. This procedure providesimmediate structural support to the weak area of the cornea as well as ablood supply to help fight the infection.

Before Teekla awoke from his anesthesia, a small tube was placed underhis lower eyelid. This is called a subpalpebral lavage and allows for topicalmedications to be applied without having to constantly pry the eyelids open.Samples taken from Teeklas left eye just before surgery revealed that theulcer was infected with a fungus called Aspergillus. Teekla remained in the

hospital for 4 days after surgery to ensure that everything was healing well.He then returned at 2 weeks, at 1 month, and at 2 months after the surgeryto check for progress. During this time, the medications he was receiving tofight the infection were slowly tapered down.

At his last recheck, the connecting portion of the graft was trimmed awayleaving only a small scar where the original ulcer had been. Teeklarecovered completely with no loss to his eye or vision because of thecoordinated efforts of his owner, veterinarian, and ophthalmologist.

Teeklas conjunctival pediclegraft immediately after surgery.

Melting ulcer on Teeklasleft eye immediately beforesurgery.

Teeklas conjunctival pediclegraft one month after sur-gery. Note how the grafthas shrunken to allow for arelatively large area of clearcornea.

A Case Study from the UC Davis Veterinary Medical Teaching Hospital


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Preventing and Handling Eye Injuries

E

ye injuries and infections are not uncommon in horses, but minor problems left untreated canquickly become serious and result in blindness if unattended. Here are some recommendations

for preventing problems and some guidelines to follow if your horse should sustain an eye injury.

One way to prevent problems is to ensure that your horses environment is safe. Make sure thatsharp edges on water troughs, metal buildings, pipes, hooks or other objects are covered, padded,or are inaccessible. Pound in or pull any old nails that may be protruding from fences and otherstructures.

Keep the horses environment as dust-free as possible.

If your horse sustains an eye injury or develops an eye infection, contact your veterinarianimmediately. (Read the section on Traumatic Injuries on page 5 of this Horse Report).

If the injury is a laceration to the eyelid, cleanthe area very gently with a saline solution whilewaiting for the veterinarian. If you dont have oneon hand (like the saline solution for contact lenses),you can make some. The ratio is about teaspoonof table salt to 1 cup of lukewarm water. It shouldtaste like tears.

If the injury consists of a foreign object such asa piece of wood that has pierced the eyelid andbecome embedded, you can remove it but followup with a full eye examination with a veterinarianto determine the extent of damage. Clean the area very gently with a saline solution while waitingfor the veterinarian. If the eyeball itself has a foreign object embedded in it, DO NOT REMOVE IT. Seek immediateveterinary attention as microsurgery may be required to remove the object and save the eye.

Put a fly mask on the horse to keep flies off the eye area.

If possible, keep your horse in subdued light, such as his stall, until the veterinarian arrives.

With all medications prescribed by your veterinarian, make sure that you follow the instructionsto the letter, including medicating your horse through the full course of treatment. Do not stopmedication because you see marked improvement. This can result in an infection flaring up again.Discard all medications at the end of the treatment course.

When working with a horse with an eye problem, be aware that he may have obscured visionand be a little more spooky than usual. Talk gently so you dont surprise him if you walk up on ablind side.


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The UC Davis Veterinary Medical Teaching Hospital has a completeOphthalmology Service for all species large and small, with an emphasis onhorses. The service comprises one of the largest veterinary ophthalmology centers

in the United States. It is completely equipped with sophisticated equipment forthe diagnosis and treatment of all eye diseases in horses, including an operatingmicroscope for microsurgery and a phacoemulsification unit for cataract surgery (asystem that uses ultrasound to break up, flush, and remove the affected lens material).The service also uses cryotherapy and beta irradiation for eye tumors.

Dr. Steven Hollingsworth is Chief of the Ophthalmology Service at UC Davis and Assistant Professorof Veterinary Ophthalmology in the UC Davis School of Veterinary Medicine. He obtained a DVMfrom Purdue University and was a veterinary ophthalmologist in private practice for nine years beforecoming to Davis. He completed a residency in comparative ophthalmology at UC Davis in 1992 andthen joined the faculty in 1994. In addition to his clinical duties, Dr. Hollingsworth teaches clinicalophthalmology to third- and fourth-year veterinary students. He also serves as Chair of the Examination

Committee of the American College of Veterinary Ophthalmologists and has been a reviewer for anumber of professional journals, including the American Journal of Veterinary Research, VeterinaryAnaesthesia and Analgesia, Veterinary Surgery, and Veterinary Ophthalmology.

The ophthalmology department is open to both referrals and the general public. To make anappointment, call the UC Davis Veterinary Medical Teaching Hospital at (530)752-0290.

Ophthalmology ServiceUC Davis Veterinary Medical Teaching Hospital

Dr. Hollingsworth

Dr. J. D. WheatApril 10, 1923 March 4, 2009

Dr. Don (J.D.) Wheat, world renowned equine surgeon and clinician andan integral part of the UC Davis School of Veterinary Medicine, passedaway on March 4, 2009. Dr. Wheat dedicated his career to the care andwelfare of the equine athlete and to the training of several generationsof equine practitioners. He was a role model for many students, interns,residents and graduate students, stimulating them to envision and explorenew ideas for improving the care of horses.

Dr. Wheat also left his legacy in the establishment of the J.D. WheatVeterinary Orthopedic Research Laboratory in 1988. The laboratoryconducts research on orthopedic diseases of animals, with an emphasis onmusculoskeletal disorders of racehorses. The laboratory provides an environment in which complex

problems presented by most musculoskeletal diseases can be addressed by using the collectiveexpertise of investigators from several different disciplines in the basic and clinical sciences of theSchool of Veterinary Medicine. Dr. Wheats interest, encouragement and continued curiosity tounderstand and discover better ways to treat musculoskeletal diseases provided the laboratory with afirm foundation on which to build the success it enjoys today.

Dr. Wheat was a charter diplomate of the American college of Veterinary Surgeons; recipient of theAmerican Association of Equine Pracititioners teaching award; member of the National Academiesof Practice; and an inductee in the International Equine Veterinary Hall of Fame. He will be sorelymissed.

Dr. Wheat


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Professor emeritus Timothy OBrien of the UC Davis School of Veterinary

Medicine was recently honored for significantly advancing the development andtraining of equine veterinarians. The distinguished educator award was presented

to Dr. OBrien by the American Association of Equine Practitioners during the

organizations annual meeting in San Diego. He was recognized for his efforts as

an educator and mentor to the many students and colleagues with whom he has

been affiliated. OBrien, a veterinary radiologist, specialized in characterizing

bone and joint problems of horses and spent much of his career at UC Davis. He

has trained approximately 120 large-animal and equine surgery residents.

Dr. Timothy OBrien Honored at AAEP Convention

Dr. OBrien

Cataracts in Foals

Horses can be born with cataracts due to developmental or heritable causesknown as congenitalcataracts. Foals with cataracts often present very early in life, usually at 1 to 2 months of age.Typically, the owners will notice the whiteness in the pupil of one eye almost immediately after

birth. This change is often followed closely by the other eye. Visual problems experienced by thefoal are noticed through behaviors such as hesitancy to go anywhere without the mare or outrightbumping into things. Otherwise, the foals are usually systemically healthy, and the eyes are notpainful.

Congenital cataracts in newborn foals are especially amenable tosurgical removal. Veterinary attention should be sought as soonas possible. Signs include a milky-appearing pupil or evidence ofimpaired vision as mentioned above. Immediately before and aftersurgery, the foal is given a number of medications including topicalantibiotics, topical anti-inflammatories (steroidal and nonsteroidal),

and systemic anti-inflammatories (usually Banamine).

The surgery is performed using a technology known as phaco-emulsification. This is the exact same technology and equipmentused in human cataract surgery. Most of the foals spend about 5 to7 days in the hospital after surgery. Rechecks are usually requiredat approximately 2 weeks and 2 months after surgery, although theinterval and frequency is determined bythe presence or absence of complications.

The most common post-operative problemis glaucoma. During the post-surgical

period, the medications are usuallyreduced. Cataract surgery will usually

result in the horse being far-sighted (not able to see things up close), butmany go on to live productive lives.

Complete cataract in a foal

less than 2 months old, im-mediately before surgery.

Typical healing two monthsafter cataract surgery.

One week after cataractsurgery. Note the incisionsutures on the right and thegree glow from the tapetum

at the back of the eye.


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