- Email: [email protected]
Ocular emergencies in the dog and cat
Br. vel . ,7. (1987) . 143, 489
VETERINARY PROFESSIONAL DEVELOPMENT SERIES
OCULAR EMERGENCIES IN THE DOG AND CAT
P . G . C . BEDFORD Department of Surgery, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA
In practical terms the ocular emergency implies that the patient is in pain and its sight is at risk . The situation usually arises suddenly, with no noticeable premonitory signs . Ocular emergencies are primarily related to trauma and infection, but they include two acute and inherited conditions, namely primary lens luxation and primary glaucoma . With these conditions premonitory signs may indeed be present, and allow the early relief of pain and prevent subsequent loss of sight .
THE CONDITIONS
Proptosis of the globe Proptosis, or exophthalmos, owes its sudden onset to orbital trauma or acute orbital cellulitis (Figs . la, lb) . Without surgical treatment or, at least, the use of topical wetting agents, exposure keratitis or ulceration will ensue rapidly . Displacement of the globe can result in impaired ocular circulation and possible haemostasis : the conjunctival tissues become hyperaemic and oedematous, and the retinal vasculature may become congested . Interference with ciliary blood supply can lead to retinal degeneration, and stretching of the optic nerve can result in its atrophy .
Fig . 1 . A) Proptosis of left eye due to orbital cellulitis ; German Shepherd Dog, 3 years, B) conjunctival and episcleral congestion .
490
BRITISH VETERINARY JOURNAL, 143, 6
Orbital trauma . Orbital damage leading to proptosis may be accompanied by fracture of the zygomatic arch, but other bone damage is unusual . Oedema of the periorbita and haemorrhage within the orbit will increase the degree of proptosis . Mydriasis indicates severe optic nerve damage or disruption of the parasympathetic supply to the iris sphincter musculature, or both . On the other hand, miosis, coupled with a soft globe, usually dictates an extremely poor prognosis . Blood within the anterior chamber is due to damage to the uveal tract, and the traumatic compression of the aqueous volume can result in angle recession, uveitis and possible glaucoma . Treatment is related to the degree of proptosis, and should take into consideration the type and amount of any accompanying damage . Diuretics and corticosteroids will help reduce the amount of orbital oedema, and broad-spectrum antibiotics should be used to reduce the risk of infection . The cornea must be kept moist until a normal blink reflex is possible, and hourly topical methyl cellulose should be replaced by tarsorrhaphy where the degree of proptosis is pronounced . Complete prolapse of the globe through the palpebral fissure occurs quite commonly in the brachycephalic, and the amount of force need not be considerable . It is the combination of a shallow orbit and a large palpebral fissure that allows this to happen, and venostasis due to occlusion of the large vortex veins, orbital oedema and optic nerve damage are the critical factors . Damage to the extraocular musculature and its cranial nerve supply may also occur. When prolapse occurs in the dolichocephalic, it usually requires much greater force, and the amount of accompanying damage to both globe and orbit can be considerable (Fig . 2). Emergency treatment consists of protecting the prolapsed globe using gauze pads soaked in physiological saline . Occasionally, the globe can be massaged gently back through the palpebral fissure should the periorbital damage be slight and where little tissue filling has occurred . When this is not possible, a lateral canthotomy will usually allow replacement of the globe behind the lids, and tarsorrhaphy will retain the globe in position until the periorbital tissue swelling has regressed . Ten to 14 days should lapse before the sutures are removed, and diuretics, systemic corticosteroids and systemic antibiotics should be used during this period . Should difficulty be experienced replacing the globe-even following lateral canthotomy, and this occurs with time-then excess chemotic conjunctiva can be removed caudal to the limbus throughout the 360 degrees of the globe . The conjunctival wound is closed using absorbable suture material . In addition the tarsorrhaphy can be supported by using a membrana flap, though this is rarely possible in the brachycephalic dog . A degree of proptosis may persist after an apparently successful repair, and globe movements may be affected as the result of damage of the extraocular muscles or their nerve supply . A common complication in this respect is temporal deviation of the globe due to damage to the medial rectus muscle or its occulomotor innervation (Fig . 3), but sight may be unaffected . However if exophthalmos is also present, then optic nerve damage can be critical . Replacement of the globe should always be attempted except where the degree of displacement causes considerable muscle and optic nerve damage . Enucleation is necessary when replacement fails, and potential corneal damage and desiccation may complicate the proptosis . Orbital cellulitis. This may cause relatively sudden onset proptosis, and similarly result in corneal drying, protrusion of the membrana nictitans, impaired circulation and possible optic nerve damage (Fig . 4a) . The pupillary reflex will be sluggish or absent, and there may be pain when the mandible is moved . Pyrexia with a leucocytosis may be
OCULAR EMERGENCIES
Fig . 2, left . Fig . 3, tight .
491
Chronic prolapse of the right eye ; Poodle, 3 years . Temporal deviation of the left eye following prolapse . Pug, 2 years .
present . Infection of the orbit usually means foreign body penetration from the mouth (Fig . 4b) or through the conjunctiva . Treatment of an orbital cellulitis necessitates the removal of the cause, drainage of exudate, and control of infection and inflammation . The orbit can be drained through a stab wound approximately 1 cm behind the last molar tooth allowing access to the floor of the orbit through the pterygoid muscles. Orbitotomy (Harvey, 1977) also affords drainage, and can facilitate the location and retrieval of foreign bodies (Fig . 5) . The zygoma is exposed and if necessary, part of it can be removed to allow adequate examination of the ventral orbit .
Fig. 4 . A) Orbit cellulitis causing proptosis of the left eye . German Shepherd Dog, 5 years . B) Apiece of wood had penetrated the oropharynx posterior to the last molar tooth . Orbital cellulitis occurred despite possible ventral drainage of the wound . a) upper molar teeth . b) the penetration wound . c) the tongue . d) the endotracheal tube .
492
BRITISH VETERINARY JOURNAL, 143, 6
Orbitotomy : The skin and subcutis have been excised along the zygomatic processes of the maxilla and temporal bones . Part of the zygomatic arch can be removed to allow adequate exposure of the orbit . a) retracted lower lid. b) ventral aspect of the globe . c) zygoma. Fig . 5 .
The eyelids Ocular emergencies involving the eyelids do not occur, but eyelid damage should be repaired as quickly and as accurately as possible otherwise corneal disease due to irritation or lagophthalmos caused by lid distortion may develop . Neonatal and early developing entropion can be severe in some breeds, and is undoubtedly responsible for blindness and pain in the Shar Pei (Fig 6) . Relief can be obtained quite easily in the very young puppy by everting the palpebral margins using a simple interrupted suture . This is immediately effective and might even provide a longterm solution, but many patients do require subsequent Hotz-Celsus resection surgery . Ophthalmia neonatorum can cause serious damage to the cornea and may even be responsible for phthisis of the globe . The sealed eyelid margins should be opened to drain the accumulating discharge, and topical antbiotics will be necessary .
The cornea Corneal penetration wounds and burns require emergency attention . On occasion, ulceration can result in rupture of the globe where there is excessive collagenase release or in the presence of a protease-producing bacterium . Wounds. These may involve the stroma to varying depths, and full thickness penetration will result in aqueous loss and hypotony . The wound may be pin-prick size with little apparent corneal damage and no obvious uveal tract involvement, whereas fullthickness penetrations may damage the iris and/or the anterior lens capsule (Fig . 7) . Potential infection and subsequent uveitis should always be considered, and both topical and local or systemic antibiotics together with mydriatic and cycloplegic therapy must be
Fig, 15. .4nterior uvcitis; left eye: hliniaturc Poodle. A dilfuse rorneal o&ma and the presence oi fiblirr in the anterior chamber
49 4
BRITISH VETERINARY JOURNAL, 143, 6
instituted . Extensive full-thickness penetration is always serious as the risk of intraocular infection and uveitis is considerable . The defect will normally seal with secondary aqueous humour and fibrin, and the anterior chamber will rapidly reform although the eye will remain hypotonic for at least 48 hours (Fig . 8) . Extrusion of iris material will help seal the wound, but the presence of this tissue in the wound and subsequent staphyloma formation provides a potential tract along which infection can enter the eye . All such wounds should be repaired as soon as possible to reduce the risk of infection and staphyloma formation . Protruding iris material should be replaced wherever possible or removed when adhesions prevent its replacement . The anterior chamber should be washed clean of blood and fibrin and reformed using balanced salt solution' or air . The wound should be repaired using interrupted 8X0 synthetic absorbable or nylon sutures, accurate apposition being necessary but complicated by corneal oedema . A spatulate needle should be used, the suture entering the cornea approximately 1 mm from the edge of the wound and passing to a depth of approximately 0 . 5 mm (Fig . 9) . Topical, local and systemic broad-spectrum antibitotics together with cycloplegic and mydriatic therapy is essential, but corticosteroid therapy to treat the uveitis should be used with care . The use of a membrana flap can be helpful . correct
incorrect
incorrect
(b)
incorrect
(c)
incorrect
(d)
Corneal suturing. In (a) there is correct apposition and the sutures will not pull through ; (b) can result in intraocular infection ; (c) & (d) will lead to wound breakdown ; and (e) will produce corneal aberration . Fig . 9.
Corneal burns. Fortunately, these are uncommon . Immediate and copious irrigation for 10-15 min with tap water or, preferably, physiological saline is essential for the bulk removal of the agent is the most important factor in treatment . Acid burns seldom '(BSS . Alcon
Laboratories)
OCULAR EMERGENCIES
4 95
penetrate further than the epithelium, and a 3% sodium bicarbonate solution to neutralize the agent plus antibiotic, can be used at 15 min intervals for 2 h following injury . In contrast, alkali burns commonly due to lime and plaster can cause severe damage (Fig . 10) . Boric or 0 . 5% acetic acid solution should be used with topical antibiotics at 15 min intervals for 2 h . There is often collagenase release, and 20% acetyl cysteine 2 may be used to counter its effect . Corneal ulceration . If this extends rapidly into the stroma emergency attention is required as descemetocoele formation and consequent rupture can occur . Primary bacterial ulcers are unusual, but the exposed corneal stroma is very susceptible to secondary infection, with staphylococci, streptococci, E . coli and Pseudomonas being the commonest organisms encountered . Pseudomonas infection in particular causes rapid stromal dissolution through a protease release. Deep ulceration is usually accompanied by marked corneal oedema and there may be stromal vascularization . A transparent base to an ulcer means that Descemet's membrane has been exposed (Fig . 11) and that descemetocoele formation with potential rupture of the globe is possible (Fig . 12) . The treatment of all deep ulcers involves broad-spectrum topical antibiotics administered hourly until the results of a corneal scrape are known . The specific antibiotic can then be used topically, locally and systemically . Cycloplegic and mydriatic therapy is essential to relieve the pain of an accompanying uveitis and reduce the possibility of staphyloma formation should rupture occur . Collagenase and protease activity should always be suspected, and 20% acetyl cysteine can be used hourly until the process of ulceration has been halted . Various conjunctival flaps can be helpful, but a pedicle of bulbar conjunctiva sutured directly into the ulcer site will provide a blood supply and physically strengthen the defective cornea (Figs . 13 & 14) . The pedicle should be wide and long enough to cover the ulcer site without tension, and sufficient conjunctiva is found on the dorsal aspect of the globe extending into the fornix . A limbal incision and two parallel incisions running posteriorly over the globe will allow the pedicle to be raised ; it is important that it is constructed of conjunctiva only, without any attached subconjunctival and Tenon's capsule material . The pedicle is sutured into the ulcer site using 8X0 synthetic absorbable material or nylon, the sutures being anchored in normal cornea whenever possible . Ten to 15 days later the pedicle's base is severed at the limbus, and any excess conjunctiva dissected away . Wound healing can be excellent and the amount of residual scarring and opacity are minimal .
The uveal tract Anterior uveitis of exogenous and endogenous origin is always a serious entity, possible posterior and peripheral anterior synechiae predisposing the eye to glaucoma, capsular deposits producing cataract and potential choroidal involvement resulting in retinal damage . The diagnostic features can be variable in extent, but pain, episcleral and possible conjunctival congestion, corneal oedema, aqueous flare or the presence of exudate in the anterior chamber, iridal oedema, a constricted pupil and a degree of hypotony are usually present (Fig . 15) . Determination of cause, and therefore its specific treatment, may be difficult, but symptomatic therapy consisting of cycloplegic, mydriatic and antiinflammatory agents must be employed routinely . One per cent atropine will break '(Mucomyst . Allard Laboratories)
496
BRITISH VETERINARY JOURNAL, 143, 6
painful iris and ciliary body spasm, and reduces the risk of posterior synechiae formation and consequent secondary glaucoma . Aggressive topical, local and systemic corticosteroid therapy is vital, and the use of non-steroidal anti-inflammatory agents can be of additional value .
Fig. 13, left . D . the iris
The conjunctival pedicle : A. the ulcer site B . the pedicle C . the bulbar conjunctiva
Fig . 14, right . The conjunctival pedicle ; left eye ; Collie Cross . A lateral canthotomy is necessary in some patients to allow adequate exposure of the cornea and the dorsal aspect of the globe . a) lateral canthotomy b) the pedicle c) the cornea
Glaucoma Acute onset glaucoma represents a dramatic ocular emergency characterized by pain and a sudden loss of vision that becomes permanent should therapy prove ineffective . The possible development of secondary glaucoma associated with trauma, uveitis and intraocular neoplasia should always be considered, and this awareness, together with effective therapy, may reduce the chance of disastrous sequelae . It is primary angle closure glaucoma (Fig . 16) and glaucoma secondary to lens luxation (Fig . 17) which usually present in an emergency situation . Premonitory signs for both conditions in indicated breeds may sometimes be seen, but invariably pass unnoticed and the patient is presented with an acute elevation of the intraocular pressure (IOP) . In angle closure glaucoma a dysplastic narrowed drainage angle rapidly closes to deny bulk aqueous drainage, while in primary lens luxation, movement of the lens and any attached vitreous humour into the pupil or the anterior chamber causes a pupillary block . The physiological iris bombé thus produced then closes the drainage angle . In both situations the IOP should be reduced as quickly as possible to limit potential optic nerve and retinal damage, and the hyperosmotic agent mannitol given intravenously at a dose rate of 1 g/ kg body weight . In angle closure glaucoma the value of miotic and aqueous inhibitor therapy is very limited, and surgical bypass of the collapsed ciliary cleft offers the best chance of long term control . Several techniques exist, but corneoscleral trephination combined with peripheral iridectomy offers the simplest approach (Bedford, 1980) (Fig .
OCULAR EMERGENCIES
497
18) . The presence of the 2 mm wide corneoscleral hole allows aqueous to be absorbed subconjunctivally, and the iridectomy prevents any forward displacement of the iris closing the drainage hole . Lens luxation is inherited in the terrier breeds, the 2-4 year old dog being the most likely candidate . It is a condition which is commonly misdiagnosed and there is often delay before the essential surgery of lens removal is completed . Such delay contributes to the irreversible collapse of the ciliary cleft, converting the transient ocular hypertension into absolute glaucoma .
iris
Fig. 17, left . Glaucoma secondary to anterior lens luxation ; left eye ; Jack Russell Terrier. The bulbar conjunctiva is chemotic ; there is diffuse corneal oedema, some vascularization at the limbus and the lens obscures the pupil . Fig. 18, right . Schematic representation of corneoscleral trephination with peripheral iridectomy* : a) preparation of the bulbar conjunctival flap b) the corneoscleral trephine hole c) the peripheral iridectomy d) the conjuctival flap sutured into position . * ( BEDFORD, P. G . C ., 1980) .
CONCLUSION The ocular emergency is obvious in presentation, often accompained by pain and threatens the sight of the patient . Effective repair techniques and medical therapies do exist for most situations but speed is of the essence if disastrous results are to be avoided .
REFERENCES G . C. (1980) . The treatment of canine glaucoma . Veterinary Record 107, 101-104 . C . E . (1977) . Exploration of the orbit . In Bistner, S. I ., Aguirre, G . & Batik, G . Atlas of Veterinary Ophthalmic Surgery. pp . 258-260. Eastbourne, Philadelphia : W .B . Saunders Co .
BEDFORD, P. HARVEY,
VETERINARY PROFESSIONAL DEVELOPMENT SERIES
OCULAR EMERGENCIES IN THE DOG AND CAT
P . G . C . BEDFORD Department of Surgery, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA
In practical terms the ocular emergency implies that the patient is in pain and its sight is at risk . The situation usually arises suddenly, with no noticeable premonitory signs . Ocular emergencies are primarily related to trauma and infection, but they include two acute and inherited conditions, namely primary lens luxation and primary glaucoma . With these conditions premonitory signs may indeed be present, and allow the early relief of pain and prevent subsequent loss of sight .
THE CONDITIONS
Proptosis of the globe Proptosis, or exophthalmos, owes its sudden onset to orbital trauma or acute orbital cellulitis (Figs . la, lb) . Without surgical treatment or, at least, the use of topical wetting agents, exposure keratitis or ulceration will ensue rapidly . Displacement of the globe can result in impaired ocular circulation and possible haemostasis : the conjunctival tissues become hyperaemic and oedematous, and the retinal vasculature may become congested . Interference with ciliary blood supply can lead to retinal degeneration, and stretching of the optic nerve can result in its atrophy .
Fig . 1 . A) Proptosis of left eye due to orbital cellulitis ; German Shepherd Dog, 3 years, B) conjunctival and episcleral congestion .
490
BRITISH VETERINARY JOURNAL, 143, 6
Orbital trauma . Orbital damage leading to proptosis may be accompanied by fracture of the zygomatic arch, but other bone damage is unusual . Oedema of the periorbita and haemorrhage within the orbit will increase the degree of proptosis . Mydriasis indicates severe optic nerve damage or disruption of the parasympathetic supply to the iris sphincter musculature, or both . On the other hand, miosis, coupled with a soft globe, usually dictates an extremely poor prognosis . Blood within the anterior chamber is due to damage to the uveal tract, and the traumatic compression of the aqueous volume can result in angle recession, uveitis and possible glaucoma . Treatment is related to the degree of proptosis, and should take into consideration the type and amount of any accompanying damage . Diuretics and corticosteroids will help reduce the amount of orbital oedema, and broad-spectrum antibiotics should be used to reduce the risk of infection . The cornea must be kept moist until a normal blink reflex is possible, and hourly topical methyl cellulose should be replaced by tarsorrhaphy where the degree of proptosis is pronounced . Complete prolapse of the globe through the palpebral fissure occurs quite commonly in the brachycephalic, and the amount of force need not be considerable . It is the combination of a shallow orbit and a large palpebral fissure that allows this to happen, and venostasis due to occlusion of the large vortex veins, orbital oedema and optic nerve damage are the critical factors . Damage to the extraocular musculature and its cranial nerve supply may also occur. When prolapse occurs in the dolichocephalic, it usually requires much greater force, and the amount of accompanying damage to both globe and orbit can be considerable (Fig . 2). Emergency treatment consists of protecting the prolapsed globe using gauze pads soaked in physiological saline . Occasionally, the globe can be massaged gently back through the palpebral fissure should the periorbital damage be slight and where little tissue filling has occurred . When this is not possible, a lateral canthotomy will usually allow replacement of the globe behind the lids, and tarsorrhaphy will retain the globe in position until the periorbital tissue swelling has regressed . Ten to 14 days should lapse before the sutures are removed, and diuretics, systemic corticosteroids and systemic antibiotics should be used during this period . Should difficulty be experienced replacing the globe-even following lateral canthotomy, and this occurs with time-then excess chemotic conjunctiva can be removed caudal to the limbus throughout the 360 degrees of the globe . The conjunctival wound is closed using absorbable suture material . In addition the tarsorrhaphy can be supported by using a membrana flap, though this is rarely possible in the brachycephalic dog . A degree of proptosis may persist after an apparently successful repair, and globe movements may be affected as the result of damage of the extraocular muscles or their nerve supply . A common complication in this respect is temporal deviation of the globe due to damage to the medial rectus muscle or its occulomotor innervation (Fig . 3), but sight may be unaffected . However if exophthalmos is also present, then optic nerve damage can be critical . Replacement of the globe should always be attempted except where the degree of displacement causes considerable muscle and optic nerve damage . Enucleation is necessary when replacement fails, and potential corneal damage and desiccation may complicate the proptosis . Orbital cellulitis. This may cause relatively sudden onset proptosis, and similarly result in corneal drying, protrusion of the membrana nictitans, impaired circulation and possible optic nerve damage (Fig . 4a) . The pupillary reflex will be sluggish or absent, and there may be pain when the mandible is moved . Pyrexia with a leucocytosis may be
OCULAR EMERGENCIES
Fig . 2, left . Fig . 3, tight .
491
Chronic prolapse of the right eye ; Poodle, 3 years . Temporal deviation of the left eye following prolapse . Pug, 2 years .
present . Infection of the orbit usually means foreign body penetration from the mouth (Fig . 4b) or through the conjunctiva . Treatment of an orbital cellulitis necessitates the removal of the cause, drainage of exudate, and control of infection and inflammation . The orbit can be drained through a stab wound approximately 1 cm behind the last molar tooth allowing access to the floor of the orbit through the pterygoid muscles. Orbitotomy (Harvey, 1977) also affords drainage, and can facilitate the location and retrieval of foreign bodies (Fig . 5) . The zygoma is exposed and if necessary, part of it can be removed to allow adequate examination of the ventral orbit .
Fig. 4 . A) Orbit cellulitis causing proptosis of the left eye . German Shepherd Dog, 5 years . B) Apiece of wood had penetrated the oropharynx posterior to the last molar tooth . Orbital cellulitis occurred despite possible ventral drainage of the wound . a) upper molar teeth . b) the penetration wound . c) the tongue . d) the endotracheal tube .
492
BRITISH VETERINARY JOURNAL, 143, 6
Orbitotomy : The skin and subcutis have been excised along the zygomatic processes of the maxilla and temporal bones . Part of the zygomatic arch can be removed to allow adequate exposure of the orbit . a) retracted lower lid. b) ventral aspect of the globe . c) zygoma. Fig . 5 .
The eyelids Ocular emergencies involving the eyelids do not occur, but eyelid damage should be repaired as quickly and as accurately as possible otherwise corneal disease due to irritation or lagophthalmos caused by lid distortion may develop . Neonatal and early developing entropion can be severe in some breeds, and is undoubtedly responsible for blindness and pain in the Shar Pei (Fig 6) . Relief can be obtained quite easily in the very young puppy by everting the palpebral margins using a simple interrupted suture . This is immediately effective and might even provide a longterm solution, but many patients do require subsequent Hotz-Celsus resection surgery . Ophthalmia neonatorum can cause serious damage to the cornea and may even be responsible for phthisis of the globe . The sealed eyelid margins should be opened to drain the accumulating discharge, and topical antbiotics will be necessary .
The cornea Corneal penetration wounds and burns require emergency attention . On occasion, ulceration can result in rupture of the globe where there is excessive collagenase release or in the presence of a protease-producing bacterium . Wounds. These may involve the stroma to varying depths, and full thickness penetration will result in aqueous loss and hypotony . The wound may be pin-prick size with little apparent corneal damage and no obvious uveal tract involvement, whereas fullthickness penetrations may damage the iris and/or the anterior lens capsule (Fig . 7) . Potential infection and subsequent uveitis should always be considered, and both topical and local or systemic antibiotics together with mydriatic and cycloplegic therapy must be
Fig, 15. .4nterior uvcitis; left eye: hliniaturc Poodle. A dilfuse rorneal o&ma and the presence oi fiblirr in the anterior chamber
49 4
BRITISH VETERINARY JOURNAL, 143, 6
instituted . Extensive full-thickness penetration is always serious as the risk of intraocular infection and uveitis is considerable . The defect will normally seal with secondary aqueous humour and fibrin, and the anterior chamber will rapidly reform although the eye will remain hypotonic for at least 48 hours (Fig . 8) . Extrusion of iris material will help seal the wound, but the presence of this tissue in the wound and subsequent staphyloma formation provides a potential tract along which infection can enter the eye . All such wounds should be repaired as soon as possible to reduce the risk of infection and staphyloma formation . Protruding iris material should be replaced wherever possible or removed when adhesions prevent its replacement . The anterior chamber should be washed clean of blood and fibrin and reformed using balanced salt solution' or air . The wound should be repaired using interrupted 8X0 synthetic absorbable or nylon sutures, accurate apposition being necessary but complicated by corneal oedema . A spatulate needle should be used, the suture entering the cornea approximately 1 mm from the edge of the wound and passing to a depth of approximately 0 . 5 mm (Fig . 9) . Topical, local and systemic broad-spectrum antibitotics together with cycloplegic and mydriatic therapy is essential, but corticosteroid therapy to treat the uveitis should be used with care . The use of a membrana flap can be helpful . correct
incorrect
incorrect
(b)
incorrect
(c)
incorrect
(d)
Corneal suturing. In (a) there is correct apposition and the sutures will not pull through ; (b) can result in intraocular infection ; (c) & (d) will lead to wound breakdown ; and (e) will produce corneal aberration . Fig . 9.
Corneal burns. Fortunately, these are uncommon . Immediate and copious irrigation for 10-15 min with tap water or, preferably, physiological saline is essential for the bulk removal of the agent is the most important factor in treatment . Acid burns seldom '(BSS . Alcon
Laboratories)
OCULAR EMERGENCIES
4 95
penetrate further than the epithelium, and a 3% sodium bicarbonate solution to neutralize the agent plus antibiotic, can be used at 15 min intervals for 2 h following injury . In contrast, alkali burns commonly due to lime and plaster can cause severe damage (Fig . 10) . Boric or 0 . 5% acetic acid solution should be used with topical antibiotics at 15 min intervals for 2 h . There is often collagenase release, and 20% acetyl cysteine 2 may be used to counter its effect . Corneal ulceration . If this extends rapidly into the stroma emergency attention is required as descemetocoele formation and consequent rupture can occur . Primary bacterial ulcers are unusual, but the exposed corneal stroma is very susceptible to secondary infection, with staphylococci, streptococci, E . coli and Pseudomonas being the commonest organisms encountered . Pseudomonas infection in particular causes rapid stromal dissolution through a protease release. Deep ulceration is usually accompanied by marked corneal oedema and there may be stromal vascularization . A transparent base to an ulcer means that Descemet's membrane has been exposed (Fig . 11) and that descemetocoele formation with potential rupture of the globe is possible (Fig . 12) . The treatment of all deep ulcers involves broad-spectrum topical antibiotics administered hourly until the results of a corneal scrape are known . The specific antibiotic can then be used topically, locally and systemically . Cycloplegic and mydriatic therapy is essential to relieve the pain of an accompanying uveitis and reduce the possibility of staphyloma formation should rupture occur . Collagenase and protease activity should always be suspected, and 20% acetyl cysteine can be used hourly until the process of ulceration has been halted . Various conjunctival flaps can be helpful, but a pedicle of bulbar conjunctiva sutured directly into the ulcer site will provide a blood supply and physically strengthen the defective cornea (Figs . 13 & 14) . The pedicle should be wide and long enough to cover the ulcer site without tension, and sufficient conjunctiva is found on the dorsal aspect of the globe extending into the fornix . A limbal incision and two parallel incisions running posteriorly over the globe will allow the pedicle to be raised ; it is important that it is constructed of conjunctiva only, without any attached subconjunctival and Tenon's capsule material . The pedicle is sutured into the ulcer site using 8X0 synthetic absorbable material or nylon, the sutures being anchored in normal cornea whenever possible . Ten to 15 days later the pedicle's base is severed at the limbus, and any excess conjunctiva dissected away . Wound healing can be excellent and the amount of residual scarring and opacity are minimal .
The uveal tract Anterior uveitis of exogenous and endogenous origin is always a serious entity, possible posterior and peripheral anterior synechiae predisposing the eye to glaucoma, capsular deposits producing cataract and potential choroidal involvement resulting in retinal damage . The diagnostic features can be variable in extent, but pain, episcleral and possible conjunctival congestion, corneal oedema, aqueous flare or the presence of exudate in the anterior chamber, iridal oedema, a constricted pupil and a degree of hypotony are usually present (Fig . 15) . Determination of cause, and therefore its specific treatment, may be difficult, but symptomatic therapy consisting of cycloplegic, mydriatic and antiinflammatory agents must be employed routinely . One per cent atropine will break '(Mucomyst . Allard Laboratories)
496
BRITISH VETERINARY JOURNAL, 143, 6
painful iris and ciliary body spasm, and reduces the risk of posterior synechiae formation and consequent secondary glaucoma . Aggressive topical, local and systemic corticosteroid therapy is vital, and the use of non-steroidal anti-inflammatory agents can be of additional value .
Fig. 13, left . D . the iris
The conjunctival pedicle : A. the ulcer site B . the pedicle C . the bulbar conjunctiva
Fig . 14, right . The conjunctival pedicle ; left eye ; Collie Cross . A lateral canthotomy is necessary in some patients to allow adequate exposure of the cornea and the dorsal aspect of the globe . a) lateral canthotomy b) the pedicle c) the cornea
Glaucoma Acute onset glaucoma represents a dramatic ocular emergency characterized by pain and a sudden loss of vision that becomes permanent should therapy prove ineffective . The possible development of secondary glaucoma associated with trauma, uveitis and intraocular neoplasia should always be considered, and this awareness, together with effective therapy, may reduce the chance of disastrous sequelae . It is primary angle closure glaucoma (Fig . 16) and glaucoma secondary to lens luxation (Fig . 17) which usually present in an emergency situation . Premonitory signs for both conditions in indicated breeds may sometimes be seen, but invariably pass unnoticed and the patient is presented with an acute elevation of the intraocular pressure (IOP) . In angle closure glaucoma a dysplastic narrowed drainage angle rapidly closes to deny bulk aqueous drainage, while in primary lens luxation, movement of the lens and any attached vitreous humour into the pupil or the anterior chamber causes a pupillary block . The physiological iris bombé thus produced then closes the drainage angle . In both situations the IOP should be reduced as quickly as possible to limit potential optic nerve and retinal damage, and the hyperosmotic agent mannitol given intravenously at a dose rate of 1 g/ kg body weight . In angle closure glaucoma the value of miotic and aqueous inhibitor therapy is very limited, and surgical bypass of the collapsed ciliary cleft offers the best chance of long term control . Several techniques exist, but corneoscleral trephination combined with peripheral iridectomy offers the simplest approach (Bedford, 1980) (Fig .
OCULAR EMERGENCIES
497
18) . The presence of the 2 mm wide corneoscleral hole allows aqueous to be absorbed subconjunctivally, and the iridectomy prevents any forward displacement of the iris closing the drainage hole . Lens luxation is inherited in the terrier breeds, the 2-4 year old dog being the most likely candidate . It is a condition which is commonly misdiagnosed and there is often delay before the essential surgery of lens removal is completed . Such delay contributes to the irreversible collapse of the ciliary cleft, converting the transient ocular hypertension into absolute glaucoma .
iris
Fig. 17, left . Glaucoma secondary to anterior lens luxation ; left eye ; Jack Russell Terrier. The bulbar conjunctiva is chemotic ; there is diffuse corneal oedema, some vascularization at the limbus and the lens obscures the pupil . Fig. 18, right . Schematic representation of corneoscleral trephination with peripheral iridectomy* : a) preparation of the bulbar conjunctival flap b) the corneoscleral trephine hole c) the peripheral iridectomy d) the conjuctival flap sutured into position . * ( BEDFORD, P. G . C ., 1980) .
CONCLUSION The ocular emergency is obvious in presentation, often accompained by pain and threatens the sight of the patient . Effective repair techniques and medical therapies do exist for most situations but speed is of the essence if disastrous results are to be avoided .
REFERENCES G . C. (1980) . The treatment of canine glaucoma . Veterinary Record 107, 101-104 . C . E . (1977) . Exploration of the orbit . In Bistner, S. I ., Aguirre, G . & Batik, G . Atlas of Veterinary Ophthalmic Surgery. pp . 258-260. Eastbourne, Philadelphia : W .B . Saunders Co .
BEDFORD, P. HARVEY,