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OPHTHALMOLOGY

OCULAR COSMETIC AND PROSTHETIC DEVICES Ralph E. Hamor, DVM, Steven M. Roberts, DVM, MS, Glenn A. Severin, DVM, MS, William Randall Trawnik, BCO, and Walter J. Johnson, BCO

The equine eye is prone to injury and damaging effects of inflammation. Review of medical record data from the Colorado State University Veterinary Teaching Hospital identified 1183 horses with ocular disorders between 1972 and 1990. Of these horses, 304 (25.7%) had conditions originating from trauma to the ocular and periocular tissues. Trauma included laceration of adnexa and globe, blunt and sharp objects causing corneal ulceration, foreign body injuries, fracture of the orbital rim, and other blunt trauma to periocular and globe tissues. Intraocular inflammation was present in 347 (29.3%) of the cases, and included many trauma cases. Ocular inflammation included cases of equine recurrent uveitis and traumatic uveitis, most frequently involving the anterior or posterior segments. Despite attempts to treat the various problems, some degree of visual impairment, including blindness, occurred in 157 (13.3%) horses and a cosmetically disfigured eye resulted in 111 (9.4%). Most visually impaired and disfigured eyes consisted of atrophied globes, severe corneal scars from perforating injuries, retinal detachment and optic nerve atrophy following trauma or inflammation, and opaque globes due to leukoma and anterior segment opacities. The effects of injury and inflammation on the equine eye are frequently disastrous. Even with acute treatment, the tendency toward chronicity in many equine ocular diseases can lead to permanent cosmetic defects or blindness. The causes of traumatic and inflammatory From the Department of Clinical Sciences, Colorado State University College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado (REH, SMR, GAS); Dallas Eye Prosthetics, Dallas, Texas (WRT); and Denver Optic Company, Denver, Colorado

(WJD VETERINARY CLINICS OF NORTH AMERICA: EQUINE PRACTICE VOLUME 8 • NUMBER 3 • DECEMBER 1992

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ocular disease -are not easily controlled in view of the environment and behavior of horses. The cosmetic appearance of the eye following injury or inflammatory disease, although not of importance to the horse, is of grave concern to many owners. Acceptable cosmetic appearance is not simply a matter of owner anthropomorphism toward their horse, but also stems from a genuine desire to have the horse free of major blemishes. The disastrous outcome of many equine eye cases and the owner's desire for an acceptable appearance prompt veterinarians to explore various techniques for restoring cosmesis to unsighted, blind eyes. The following discussion addresses enucleation, evisceration and intraocular prosthesis implantation, corneoscleral prosthesis, tattoo, and tinted contact lenses as means of improving the animal's cosmetic appearance and comfort. ENUCLEATION

Indications for enucleation include irreparable trauma, malignant intraocular neoplasia, panophthalmitis, blind and painful eye secondary to chronic inflammation or glaucoma, histologic confirmation of a suspected diagnosis, and, possibly, cosmesis. 3, 8,10,13,19,23,25,31 Although this surgical procedure is effective in resolving painful ocular problems and providing tissue to aid in a diagnosis, it is frequently unacceptable to owners as a cosmetic procedure. The surgical procedure is similar to that described in small animals except that location and removal of the orbital lacrimal gland avoids potential complications due to secretion from the large equine lacrimal gland if left in the orbit. Either a transpalpebral or transconjunctival approach may be used and these procedures are well described in the literature. 3, 8, 10, 13, 19, 23, 25, 31

Enhancing Cosmetic Appearance

A significant consideration pertinent to the surgical procedure is whether to place an orbital implant. An orbital implant improves the cosmetic outcome after enucleation. Without an orbital implant, the skin over an enucleated socket gradually becomes concave and some owners are dissatisfied with the resultant appearance. If an owner is unconcerned with final cosmetic outcome, omit the implant. Offering the owner a choice, however, decreases potential criticism of the veterinarian. Literature evaluation of silicone and mesh implants deem both types highly successful and cosmetic by horse owners. One study evaluating seven implants 20 and 28 additional implants in horses (Hamor RE, Roberts SM, Severin GA: Orbital implants in dogs, horses, and cats: a retrospective study of 161 cases. Submitted for publication, 1992) documented only three (8.6%) implant failures. In all cases with cosmetic evaluations, the owners gave an excellent or good rating. Silicone implants are commercially available (Jardon Institute for Eye

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Care, Southfield, MI) and mesh implants are fabricated by bridging the orbital rim with nonabsorbable monofilament suture using a grid or wheel-spoke pattern. Case selection and perioperative management help prevent implant rejection or extrusion (Hamor RE, Roberts SM, Severin GA: Orbital implants in dogs, horses, and cats: a retrospective of 161 cases. Submitted for publication, 1992).20 One implant failed due to an incompletely excised orbital angiosarcoma. The implant extruded 10 days after surgery. Implants into an orbit involving neoplasia, infection, or chronic inflammation cannot be recommended. 13,19,21 Two other failures related to perioperative procedures. In each instance, implant extrusion occurred within 1 month of implantation. Th.is is similar to early extrusion in humans, commonly caused by intraorbital hematoma formation and possible subsequent infection. 7, 11,21 For these reasons, some human ophthalmologists recommend perioperative systemic antibiotics and most recommend postoperative pressure bandaging to reduce the chance of early extrusion. 11, 16, 21 Proper tissue closure and apposition over the implant are crucial to prevent extrusion. 16, 21 It is important to interpose tissue between the implant and the skin before skin closure. Contouring the anterior one fourth of the silicone implant allows a forward-directed flat face (Fig. 1) and prevents the implant face from being near the skin. In addition, the facial skin has a flat contour. Implant position is maintained by placing sutures across the orbital opening and anchoring into dense fascia at the orbital rim. Such sutures keep the implant within the orbit. Subcutaneous tissue apposition and possibly placement of autogenous fat or subcutaneous tissue grafts over the implant provide additional tissue protection. The choice of implant material depends on the situation surrounding the enucleation and the surgeon's preference. Methyl methacrylate (Storz Instrument, St Louis, MO) and lucite (Jardon Institute for Eye Care) spheres are available in addition to silicone and suture meshtype implants. Spherical implants must be of adequate size to fill the orbital width and depth. The use of intraorbital aqueous antibiotics (300,000 to 500,000 IV of potassium penicillin) around the implant, immediately upon skin closure, reduces the chance of infection. Neither

Figure 1. Example of untrimmed, trimmed, and contoured silicone prosthesis.

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of the two horses that had implant extrusions within 1 month of surgery had perioperative systemic antibiotics or pressure bandaging. To help prevent ocular implant extrusion in horses, the anterior implant face should be sculpted, intraorbital and systemic antibiotics administered, and postoperative pressure bandages applied. 14 Complications and Return to Use

Complications from an enucleation without an implant are minimal except those related to cosmetics. Addition of an orbital implant after enucleation significantly improves the cosmetic appearance without introducing unwarranted patient risk. Appropriate case selection and rational management minimize orbital infection and inflammation, the most significant complications. Implants occasionally rotate either spontaneously or traumatically. Rotation usually results in the curved posterior face of the implant facing anteriorly. Although the owner may dislike the appearance, rotation does not cause extrusion on its own. Owners often express concern regarding the horse's ability to function after removal of one eye. Enucleations generally are performed on visually impaired eyes that are painful, chronically inflamed, blind, or neoplastic. The acutely injured, visually impaired horse causes many owners more concern. If the horse performs tasks adequately before the enucleation, deviation from this use after surgery is unexpected. Most horses adapt quickly and continue to perform well after the loss of a globe. Only 3 of 24 horses had a change in function after enucleation of one globe (Hamor RE, Roberts SM, Severin GA: Orbital implants in dogs, horses, and cats: a retrospective study of 161 cases. Submitted for publication, 1992). In all cases, the horses were high-performance animals such as race horses and were retired from performance to become pleasure riding or breeding animals. Each case should be treated individually and options and outcome discussed in advance with the owner. Loss of vision in one eye rarely eliminates the horse from normal use. INTRAOCULAR PROSTHESIS

A silicone prosthesis placed within the corneoscleral shell following evisceration offers a definite cosmetic improvement over enucleation procedures. The procedure also provides pain relief from severely injured or chronically diseased eyes. A report on globe lacerations showed most had a guarded or poor prognosis, given that 26 of 43 (60%) resulted in blindness, globe atrophy, enucleation, or euthanasia of the horse. ls Cosmetic salvage of some may have been possible with this procedure. 22 The indications for implantation of an intraocular prosthesis are similar to enucleation but reasonably intact ocular tissues

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are required. 4, 12, 17, 18, 26, 28, 29, 30 Contraindications to placement of an intraocular prosthesis include intraocular neoplasia, panophthalmitis, severe keratitis, or scleritis. 4, 12, 17,18,26,28,29,30 These diseases may lead to complications and extrusion.

Enhancing Cosmetic Appearance

The surgical procedure for intraocular prosthesis implantation, described in the literature,4, 12, 17, 18, 26, 28, 29, 31 requires proper patient selection for a successful and cosmetic outcome. Atrophied or extensively damaged globes are beyond repair. It is important to remember the previously mentioned contraindications. Prosthesis size is crucial to surgical success and merits further discussion. The horizontal diameter of the normal cornea is measured and a prosthesis that is equal to or 1 mm smaller than the measured diameter is implanted. If the globe is buphthalmic, the proper implant size is based on the measured normal cornea. The buphthalmic globe will shrink around the prosthesis and provide a normal-sized globe. An atrophied globe should not be stretched by introducing a prosthesis larger than the globe. This surgery involves dorsally incising the conjunctiva 5 mm behind the limbus, dissecting conjunctiva from sclera, and incising the sclera 1 cm behind the limbus to create an incision parallel to the limbus from the nasal to temporal globe aspect. In the nonglaucomatous globe, extending a second incision posteriorly from the center of the perilimbal incision (forming a "T" incision) facilitates prosthetic insertion. Copious hemorrhage occurs when a small spatula-shaped instrument (e.g., cyclodialysis or Green spatula) separates the uveal tract and retina from the sclera. Intraocular con nts are removed by freeing the tissues in one conical mass. Touching the corneal endothelial surface with any instrument is avoided. Visualization is enhanced by using suction, but careful uveal dissection is the real key. If properly dissected, the uvea and retina remain attached at the optic disc. Cutting a hole in the peripapillary sclera should be avoided when amputating the uvea and retina. Scleral and conjunctival wounds are closed with 5-0 and 6-0 absorbable suture, respectively, using simple interrupted and continuous patterns. Perioperative procedures are important to successful outcome of the procedure. Histopathology should be performed on intraocular contents, especially if an intraocular neoplasm is suspected. Diagnosis of intraocular neoplasia warrants immediate removal of the globe. Use of a systemic antibiotic in every case and a nonsteroidal anti-inflammatory agent in most cases is prudent. A temporary tarsorrhaphy is used for 2 to 4 weeks after surgery to protect the cornea and mask intraocular hemorrhage during healing. In buphthalmic globes, a temporary tarsorrhaphy is especially beneficial to aid in protecting the cornea until the eye returns to a normal size. Owners should be advised that an intraocular prosthetic procedure

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requires more time for healing and optimal cosmetic appearance than an enucleation. The hematoma organizes and goes through color changes similar to a bruise. In addition, the cornea develops pronounced interstitial vascular keratitis that regresses within 2 months, leaving clear visualization of the prosthesis or a dull gray cornea. The corneal appearance after surgery depends primarily on corneal health (especially the posterior endothelium) before surgery and handling of the cornea during surgery. 27/ 30 Corneal damage before or during surgery results in corneal opacity after normal healing. Complications and Return to Use

Careful case selection and perioperative care decrease complications. Implanted, blind globes occasionally suffer traumatic corneal injuries, requiring aggressive treatment, hopefully avoiding corneal perforation. Corneas of implanted globes may have reduced healing capabilities because of loss of aqueous humor production. Owners should be advised that implant extrusion usually requires an enucleation for management. Extrusion did not occur in one study that evaluated equine intraocular implants in two horses. 2o One horse developed a localized incision infection that responded to oral antibiotic treatment, however. Clinical experience at the Colorado State University Veterinary Teaching Hospital suggests that carefully selected patients have few complications and implant extrusion or rejection rarely occurs. The owners of the two horses already mentioned rated the cosmetic appearance after surgery as excellent. This agrees with our clinical experience. Most implanted horses adapt as well to monocular vision as enucleated horses. CORNEOSCLERAL PROSTHESIS

A molded, plastic prosthesis fitted beneath the eyelids achieves the most natural appearance after scarring, atrophy, or globe removal. Painting and detailing the appliance simulates the conjunctiva and anterior segment, including the iris and pupil. This type of prosthesis, called a corneoscleral prosthesis, covers the conjunctival sac or disfigured globe. Although visually appealing, the process involves a greater investment in time and money than previously described procedures. Enhancing Cosmetic Appearance

Some veterinarians and animal owners ask, "Why would an owner go to the expense and time commitment involved in the fabrication, placement, and management of a corneoscleral prosthesis?" Economics and cosmetic appearance motivate some owners involved in showing

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and breeding of horses. For some owners, extension of an animal's show and breeding career may be more significant and personally or financially rewarding than the investment in a corneoscleral prosthesis. The prosthesis offers an improved cosmetic appearance, allowing the animal to continue competing and, perhaps, to benefit from exposure and, ultimately, increased breeding contracts or foal production. Other owners, motivated purely by improved cosmetic appearance, feel their equine friend and companion should be as normal in appearance as possible. Some owners find an enucleated, unsightly globe, or phthisical globe unacceptable. Veterinarians have an obligation to offer owners all possible options and let them make decisions regarding the best procedure for their animal. The indications for fitting a corneoscleral prosthesis are similar to an enucleation or intraocular prosthesis but also include improving phthisical, scarred, or microphthalmic globe appearance. 13, 14,24 Poorly developed or damaged fornices represent the primary contraindications to fitting a corneoscleral prosthesis. 5 Retention of the prosthesis depends on an animal having well-defined superior and inferior fornices. Although a properly designed prosthesis can fit directly over a phthisical, scarred, or microphthalmic globe, best results and fewer patient complications occur if the damaged or small globe is enucleated, with placement of an orbital implant. If the prosthesis covers an abnormal globe, problems may arise due to continued globe shrinkage, globe motion causing prosthetic extrusion, and prosthetic-related injury or irritation to underlying ocular tissues. Any changes in orbital or intraorbital tissue contours result in a poor prosthetic fit. Problems secondary to poor fit include chronic conjunctivitis, corneal irritation, corneal ulceration, epiphora, catarrhal discharge, prosthetic rotation or misalignment, and improper prosthetic retention. If the globe is near normal size, the posterior prosthesis surface perfectly matches the globe surface, and the prosthesis is thin (Le., 3-6 mm thick), good results are possible. Optimal management of small globes involves enucleation and orbital prosthetic implantation, thus allowing a thin and light corneoscleral prosthesis rather than a thick, heavy device. Particular attention must focus on the size of the orbital implant to maximize cosmetic appearance and decrease the possibility of extrusion. l l ,21 Larger orbital implants allow a thin, light prosthetic eye. Such a prosthesis fits better and is not as prone to secondary complications or sagging of the lower lid under the weight of a heavy prosthesis. Achieving this goal requires a transconjunctival enucleation approach to save the integrity of the conjunctival fornices and eyelids. The orbital implant-silicone, methyl methacrylate, or lucite-should maximally fill the orbital space. It is important to leave enough conjunctiva and orbital fascia to cover the implant adequately and allow for near-normal conjunctival anatomy. If insufficient tissue covers the orbital implant, the corneoscleral prosthesis may rub and irritate the conjunctiva, causing complications such as late extrusion of the implant. 21 The veterinarian must work closely with a human ocularist. The ocularist needs an understanding of the differences between veterinary

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and human orbital and ocular anatomy. Unique differences include the presence of a third eyelid, retractor oculi (bulbi) muscles, variable limbal pigmentation, nasal and temporal filtration angle visualization, a horizontal pupil, and granulae iridica in horses. Third eyelid preservation is important because of the associated glandular tear production. This gland provides approximately 35% of the aqueous tear film in dogs and presumptively has a similar role in horses. 8 Retractor oculi muscles cause globe retraction and may affect proper fit of the corneoscleral prosthesis, but transconjunctival enucleation and orbital implantation avoid this potential complication. Knowledge of internal ocular anatomy is important in achieving superior cosmesis. If the prosthesis shows a horizontal pupil, maintenance of proper orientation demands accurate prosthetic fit. Omitting the pupil avoids pupil tilt caused by rotational problems and eliminates the need to reproduce granulae iridica in the prosthesis. The cosmetic appearance in this latter situation remains good because of the natural dark iris color in most horses. Accurate corneal shape and filtration angle detail at the nasal and temporal globe aspect are important in a good prosthesis. Potential problems may be avoided by establishing a close working relationship between the veterinarian and ocularist that includes submission of color photographs or slides for final prosthetic fabrication.

Procedure

Similar prosthetic impression, fabrication, and fitting techniques apply for horses and humans. 1, 5, 13, 14 An ocularist can help obtain the basic equipment, including impression trays, impression material, conformers, and dental stone casting material. One should have several impression trays and conformer sizes to allow for the variable sizes and shapes of the equine orbit. Impression trays, molded from plastic or Orthoplast (Johnson & Johnson Orthopedic, Raynham, MA), are customized with fenestrations to allow for air displacement by the impression material and are sized to properly fit into the superior and inferior fornices (Fig. 2A). Making an impression and producing the ocular prosthesis is a multiple-step procedure, with the basic steps described subsequently (Table 1). For specific details or variations, an ocularist serving your area should be contacted. Impressions can be taken on most horses while standing, using topical anesthesia and moderate to heavy intravenous sedation. Regional anesthesia of the upper eyelid with a frontal nerve block facilitates the impression process. For an optimal impression on fractious or stubborn animals, general anesthesia is recommended. Before taking an impression of the socket, the eyelids and conjunctival sac are carefully evaluated for abnormalities, especially infectious or inflammatory disease. Existing disease should be diagnosed and treated before this procedure is attempted. The impression tray is slipped between the eyelids and carefully

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Figure 2. Major steps in corneoscleral prosthesis impressioning and casting. A, Commercial or self-made (*) impression trays are used. B, Mix the alginate and load into syringe. C, Support the tray in the socket to approximate the normal corneal position. D, Fill but do not overdistend the socket with alginate. E, Examine the posterior surface for exactness and note the nictitans (*), nasal canthus (N), and temporal canthus (T). F, Place the impression posterior side down into the casting material, allow it to set, and apply a thin layer of liquid soap to the cast. G, Cover the balance of the impression with casting stone and allow to dry for several hours. H, Separate the two cast pieces and label the posterior surface with nasal (N), temporal (T), and nictitans (*) markings.

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Table 1. STEPS IN PRODUCING A CORNEOSCLERAL PROSTHESIS* Procedure (1) Enucleation and orbital implant

(2) Impression and casts of socket (perform after all conjunctival sutures are gone and a smooth surface exists)

(3) Send cast and impression to ocularist (4) Fit temporary prosthesis

(5) Final prosthesis fabrication and fitting

Specific Details (a) During healing of surgical site, treat with topical antibiotic ointment four times daily and systemic antibotics (b) Fit a temporary conformer in the socket to maintain eyelid and conjunctival sac size (a) Mix alginate to smooth pudding consistency and infuse into impression tray to fill the socket (b) Replace conformer (c) Dry stone cast several hours before separating (d) Mark nasal and temporal canthus on stone cast (e) Photograph the normal eye (a) Send impression in moist chamber (b) Temporary prosthesis will be fabricated (a) Allow initial wear prior to fitting (b) Adjust fit with dental wax applied to prosthetic rim (c) Mark limbus location, pupil position, and pupil size (d) Return acceptable temporary prosthesis to ocularist with color photograph or slide of normal eye (e) Replace conformer (a) Final colored prosthesis is made (b) Fitting and final instruction to owner on prosthesis care and maintenance

Time Frame 7-10 days 21-30 days'

30 minutes

4 hours

3-4 days 2 weeks 1-7 days 45 minutes

3-4 days

2 weeks 1 hour

*The process can be initiated at either step one or two, depending on whether an enucleation is performed.

positioned to fit the superior and inferior fornices well. The tray should cover the entire orbital opening. The ophthalmic alginate material is mixed with water, achieving a smooth paste consistency, and loaded into a syringe (Fig. 2B). The anterior curvature of the impression tray must approximate the anterior globe curvature. Through an impression tray fenestration, the orbital socket is filled (Fig. 2C) until excess alginate material flows out the extra fenestrations (Fig. 20). Overfilling the socket should be avoided to prevent deforming orbital tissues. The setting time of approximately 3 to 5 minutes depends on the mixture and ambient temperature. The impression tray is kept in proper alignment with the socket and external ocular structures during setting. After the alginate has set, the impression tray is removed and the posterior impression surface inspected for defects. The posterior portion of the impression must replicate the socket exactly (Fig. 2E). The procedure is repeated if necessary to obtain a perfect impression or to mold the normal surface of the other eye. Any remaining alginate material is removed from the socket.

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The dental stone casting material is mixed with water and gently agitated or tapped to bring air bubbles to the surface. A two piece dental stone investment or casting is made by filling a paper cup onethird full with casting material and slightly embedding the posterior impression surface into the casting material as it would normally be positioned within the orbit (Fig. 2F). Fifteen minutes is allowed for cast setting. A thin layer of liquid soap is then applied on top of the investment surface. The anterior impression surface is carefully covered with casting material, making a second investment (Fig. 2G). The investments should completely cover the impression at a thickness of 1 to 2 cm. After setting is complete, the investments are separated (the layer of soap prevents adherence of the two portions) and the portion representing the socket surface is carefully examined. To aid the ocularist in the final prosthetic fabrication, label the nasal, temporal, and third eyelid locations on the surface of the investment cast (Fig. 2H). The entire procedure is repeated if the impression or investment is imperfect. Accurate impression and investment will prevent secondary problems related to poor prosthetic fit. The impression and investment are sent to the ocularist and a conformer is placed into the socket. Some ocularists prefer to work with the original impression versus the investment cast. To manufacture the actual prosthesis, the ocularist places methyl methacrylate into the investment and subjects it to heat and pressure curing. The resulting model serves as a temporary prosthesis for trial fitting, alignment testing, and pupil marking. The temporary prosthesis is placed within the socket for any necessary adjustments and markings. Minor adjustments are made in fit by layering dental wax around the edge of the prosthesis. The modified prosthesis is placed in the socket to evaluate fit and position. If the original temporary prosthesis fits well, the horse can wear the appliance for 1 to 7 days before making final fit determinations. The dental wax-adjusted prosthesis is returned to the ocularist for modification. Upon receipt of the approved temporary prosthesis, the ocularist will need a close-up color photograph or slide of the normal eye to match color and detail. The conformer is used until receipt of the final prosthesis, preventing alteration in lid conformation due to an empty socket. The ocularist will make the final prosthesis by removing 3 to 4 mm from the prosthetic surface, allowing space for painting of iris and scleral detail. Application of a transparent overlay over the painted surface provides anterior chamber depth and approximates anterior corneal curvature. An orientation mark on the final prosthesis allows for correct positioning in the animal. The various prosthetic stages of fitting may require chemical restraint, topical anesthesia, and twitch restraint. Silicone oil or ophthalmic ointment will supply lubrication. To fit the prosthesis, the appliance is slipped between the eyelids and into the upper fornix until it is past the lower eyelid (Fig. 3A). Releasing the prosthesis allows positioning behind the lids across the orbital face (Fig. 3B). After the horse has worn the prosthesis for several days, the technique of fitting without chemical restraint is demonstrated to the owner. With practice,

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Figure 3. Fitting the prosthesis. A, Sedate and topically anesthetize the horse. Introduce the prosthesis with the orientation mark in the correct position and gently push into the superior fornix until the inferior rim of the prosthesis clears the lower eyelid margin. B, Release the prosthesis to allow seating in the socket and lubricate with silicone oil or ophthalmic ointment.

most owners learn to work with the prosthesis with minimal use of drugs. Proper prosthesis maintenance is thoroughly discussed with the owner. Attention to this detail will help avoid most potential complications. Owners are encouraged to remove the prosthesis every 1 to 2 weeks for cleaning of the prosthesis and socket. Figure 4 provides examples of final prosthetic appearances. Complications and Return to Use

Potential complications include conjunctivitis, growth of an immature orbit, atrophy of orbital contents, contracture of the conjunctival sac, and irritation of retained remnants of disfigured globes. 24 Conjunctivitis may result from prolonged prosthetic retention, foreign body entrapment around the prosthesis, and poor prosthetic fit. Proper appliance maintenance and fit avoid most conjunctivitis and foreign body problems. Owners of young horses should be warned about improper fit due to orbital growth. If a young horse outgrows the prosthesis, the horse is refit or the original prosthesis is built up. Atrophy of the orbital contents and prosthesis recession are usually not problems when fitting an anophthalmic socket with an orbital implant. Most horses tolerate the corneoscleral prosthesis and have an excellent cosmetic appearance to owners. In some instances, observers are unaware the horse has a blind, prosthetic eye. COSMETIC CONTACT LENS

Indications for a cosmetic contact lens primarily revolve around improving the cosmesis of a scarred or discolored cornea. 13, 14 Lenses

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Figure 4. Examples of final prosthetic styles. A, Prosthesis with a pupil. B, Prosthesis without a pupil. C, At a distance, the lack of a pupil does not seriously alter the cosmetic appearance. D, Even subtle fit problems still allow an acceptable appearance demonstrated by the prosthesis in the left socket.

work best on a scarred cornea that otherwise is normal in shape and contour. Contact lenses tolerate slight corneal surface irregularity, but fitting and lens retention become difficult over an irregular cornea, especially when deep surface defects are present. Poorly fitted lenses become dislodged by the eyelids and nictitating membrane. This form of ocular cosmetic appliance serves as a temporary mask for globe lesions. Once a properly fitting lens is obtained, the lens, tinted to partially occlude light, masks even dense leukoma (Fig. 5). The owner should apply the lens before a special event and remove it soon afterward. If the lesion being masked regresses or resolves, use of the contact lens should be discontinued. Horses' reluctance to tolerate frequent lens insertion and removal hampers long-term use. Although possible in some cooperative horses, long-term retention is difficult and frequent lens loss or damage occurs. If the lens is left on the cornea for more than 48 hours, removal and cleaning is recommended at least every other day. Your veterinary ophthalmologist should be consulted in obtaining contact lenses. Some opticians may be willing to provide assistance as well.

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Figure 5. Example and fitting of a tinted contact lens. A, This tinted equine extended-wear contact lens was used to mask a corneal scar when the horse entered the show ring. B, A similar contact is being placed on a horse's cornea.

TATTOO

Eyelid tattooing is useful in situations of inadequate pigmentation of the lids and nictitating membrane. Some indications are cosmetic, but the greatest use involves increasing coloration of periocular tissues to reduce the chance of solar blepharodermatitis or squamous cell carcinoma. 13, 14 Application of a corneal tattoo may improve cosmetic appearance and allow masking of corneal leukoma causing intraocular glare, lacrimation, photophobia, or blepharospasm. 2, 6, 13, 14 The introduction of tinted contact lens has made this procedure obsolete in humans and rarely used in horses. Contraindications to corneal tattoos include the presence of ulcerative or inflammatory keratitis, anterior uveitis, or loss of corneal innervation. Caution should be used when covering a central leukoma because further degradation in vision may result.2, 13 Corneal and eyelid tattoos should be avoided in the presence of neoplastic, ulcerated, necrotic, or infected tissues. Tetanus immunization must be current for eyelid tattooing and general anesthesia is used for eyelid or corneal tattoos. Preoperative nonsteroidal anti-inflammatory treatment helps reduce postoperative swelling and pain. Topical and systemic antibiotics are administered subsequent to eyelid tattoos and topical antibiotics and atropine after corneal tattooing. Eyelid Tattoos

Eyelid tattooing, although not complicated, requires time and patience for proper effect. 13, 14 After inducting general anesthesia and clipping the eyelashes and vibrissae, a 5-minute skin and ocular surface

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Figure 6. Tattoos can be applied to the eyelids or cornea. A, This Appaloosa had a history of blepharitis secondary to solar radiation irritation. Before tattooing, the majority of the eyelid skin was nonpigmented. B, Note the darkened appearance of the eyelid margins several hours after tattooing and initial cleaning of excess ink from the tattoo site and face. C, It is possible to mask corneal lesions and allow them to blend in with the underlying darkly colored iris and pupil. A focal lesion in the central cornea has been tattooed black with platinum chloride.

disinfectant rinse with dilute povidone-iodine solution (i.e., 1 part povidone-iodine to 19 parts saline) is applied. Gentle blotting and irrigation of tissues are used rather than scrubbing. The globe is protected with ophthalmic antibiotic ointment and the skin area not involved in the tattoo with a thin film of petrolatum. Petrolatum facilitates subsequent cleaning of the facial area. Because most tattoos involve large tissue areas, an electric tattoo gun fitted with a multipleneedle cluster is used. To tattoo the eyelid margin, a needle cluster of 2 to 4 needles is used. A needle cluster of 8 to 12 needles arranged in a circular pattern works well for larger surface areas. For most situations, carbon-based, black tattoo ink is used given that the primary goal is to protect the skin from ultraviolet radiation. Other colors of ink are readily available from human tattoo establishments. The tattoo needles are chemically disinfected and the needle stroke set to allow the instrument to glide over the tattoo site without catching or tearing the skin. Needle penetration of 1 to 2 mm is adequate for the outer eyelids and 0.5 to 1 mm for the nictitans. Hemorrhage is blotted away as needed. Saline rinsing removes excess ink, allowing evaluation of the area of coverage and density of tattoo. The procedure is continued until adequate coverage of the entire site is obtained (Fig. 6A and B). Eyelid tattoos are not permanent, gradually fading with time, but good color is retained for at least 2 to 5 years. If using black ink, the final tissue color will be gun-metal gray. Tattooed horses

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generally are not cosmetically acceptable for showing in conformation classes.

Corneal Tattoos

Tattooing of the cornea by chemical or mechanical means is possible. 2, 13, 14 Chemical tattooing is safer than mechanical, using an electric gun device or intrastromal India ink injection. After general anesthesia induction and ocular surface disinfection with dilute povidone-iodine, the epithelium over the affected area is removed. Touching the epithelium destined for removal with an isopropyl alcohol-soaked swab facilitates debridement. A solution of 2% platinum chloride is applied to the site by swab or careful use of an eye dropper for a 2-minute period. The site is then treated with a 2% hydrazine hydrate solution for 30 seconds. The reduced platinum, a black precipitate, permanently deposits in the anterior stroma (Fig. 6C). The conjunctival sac is rinsed with 0.9% saline to remove excess chemical solutions. The superficial ulcer is treated using topical antibiotic and atropine ointment four times daily until healed. Epithelium regeneration occurs within 5 to 7 days. Another, similar, chemical procedure uses 3% gold chloride for 2 to 3 minutes followed by 2% tannin solution as a reducing agent for 1 minute. This latter precipitation reaction occurs best in an alkaline environment, achieved by use of 1% soda solution or previously buffered gold chloride. A globe with corneal leukoma masked by a tattoo, although appearing reasonably normal at a distance, still shows a noticeable corneal lesion on close inspection. Depending on the tattoo location, visual impairment may result. Due to the probability of vision impairment, tattooed horses may be declared unsound. SUMMARY

Specific details on surgical procedures, although not covered here, are available in other references. Factors enhancing the overall cosmetic appearance obtained with procedures are emphasized, providing information that should allow veterinarians to offer clients a good cosmetic appearance and effective treatment for disfiguring ocular problems in their horses. Questions regarding procedures should be addressed to your referral ophthalmologist or, in the case of a corneoscleral prosthesis, the ocularist assisting. References 1. Allen L: Modified impression fitting. In Shannon G, Connelly F (eds): Oculoplastic

Surgery and Prosthetics. Int Ophthalmol Clin 10:747-762, 1970

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