Lens & Vitreous Flashcards

Question

How else may congenital cataracts occur if not inherited like in the Miniature Schnauzer? What other abnormalities can congenital cataracts be associated with? And what is MOD and which breeds predisposed to this?

Answer 1

Congenital cataracts = present at birth Other forms of congenital but non inherited cataract are recognised sporadically and thought to result due to in utero insults. Other ocular abnormalities associated with them include - microphakia, PPM's, persistent hyperplastic tunica vasculosa, persistent hyperplastic primary vitreous, retinal dysplasia, microphthalmia, oscillating type of nystagmus. Above abnormalities may all be included in suspected hereditary complex of multiple ocular defects (MOD) Breed predisposed to MOD - Cavaliers, Golden Retriever, Cocker Spaniel, Old English Sheepdog, West Highland White Terrier.

Answer 2

PHPV & PHTVL - usually see both together. Can occasionally get PHTVL by itself but uncommon - fine filamentous web or punctate/pigmented opacities on posterior lens capsule. May be unilateral or bilateral. Aetiology - Hyaloid system and tunica vasculosa lentis become hyperplastic during early embryological development and continue to proliferate following birth. (Dysplasia rather than failure of regression) Degree of visual impairment depends on degree of proliferation of the hyaloid system and presence of complications e.g cataract formation and haemorrhage. Clinical lesions vary: Fine pigment spots on posterior lens capsule Fibrovascular plaques involving posterior lens capsule Accompanied by - lentigoblus, lenticonus or coloboma, cataracts, intralenticular haemorrhage, persistent hyaloid artery, persistent pupillary membranes and capsulo-pupillary vessels (pigmented strands or patent vessels originating from retrolental plaque and insert on anterior surface of the lens)

Answer 3

Bilateral inherited trait reported in the Dobermann, Staffordshire Bull Terrier, Miniature Schnauzer but can also be seen sporadically in other breeds and can be seen unilaterally. Graded 1 to 6 depending on severity. Grade 1 = minor posterior capsular cataract and retrolental dots Grade 2= more intense central posterior capsular cataract with yellow/brown retrolental fibrous tissue and pigment dots. PPM also often seen. Grade 3 = persistent tunica vasculosa lentis - hyaloid system visible with retrolental meshwork and abnormalities as for grade 2 Grade 4 = lenticonus and abnormalities as for grade 3 Grade 5 = combination of grade 3 and 4 abnormalities Grade 6 = combination of former grades associated with lens coloboma, microphakia and accumulations of blood and pigment.

Answer 4

Selective breeding to prevent as inherited condition in certain breeds (e.g excluding grade 2-6 from breeding programmes) Can progress in some breeds (Dobermann) and lead to progressive cataracts and blindness - less likely to do this in the SBT. When vision severely impaired but morphology and function of retina ok then phacoemulsification with posterior capsulectomy and anterior vitrectomy can be considered - however risks associated with vitrectomy mean much less success than with uncomplicated cataract surgery + potential for haemorrhage from persistent hyaloid artery.

Answer 5

Occurs due to failure of the hyaloid vascular system to regress normally. Relatively uncommon and sporadic. Clinical signs vary in accordance with the part of the hyaloid artery structure that has remained. Most common = small vascular remnant on the posterior lens capsule but the opacity is rarely progressive. Remnant does not usually carry blood but a persistent hyaloid artery may remain in rare cases and be patent - haemorrhage from this vessel into the lens or vitreous may occur. Differential = PHPV/PHTVL

Answer 6

Aphakia = complete absence of the lens Microphakia = small lens (may be a feature of multiple congenital ocular abnormalities or as part of the PHVTL/PHPV complex Lens appears small within the pupil and may have an aphakic cresent similar to that seen with lens subluxation - however there is little evidence of lens instabilty and the zonules appear normal in numbers but stretched to cover the extra distance between the lens and ciliary body.

Answer 7

Incomplete separation of the lens placode from the surface ectoderm may leave the lens confluent with the cornea. Cornea and lens are usually opacified at this location. Extremely rare for this condition to occur

Answer 8

Congenital cataracts (inherited vs MOD vs in utero insult) Microphakia/Aphakia Lenticonus/Lentiglobus Lens Coloboma Persistent pupillary membrane Peter's Anomaly Persistent hyaloid artery Persistent tunica vasculosa lentis/persistent hyperplastic primary vitreous

Answer 9

Cataract = any opacity of the lens or its capsule

Answer 10

Age of onset - congenital, juvenile, senile Aetiology - Primary (e.g hereditary or senile cataracts) vs Secondary (other intraocular disease, electrocution, radiation, trauma, metabolic disease etc) Extent - Incipient vs Immature vs Mature vs Hypermature Position - Capsular, Subscapsular, Nuclear, Cortical, (within or outside the visual axis) Classification important for looking at potential for progression.

Answer 11

Can be sight threatening, painful and sometimes indicator of other disease.

Answer 12

Congenital = cataract at birth Juvenile = develops early on in animals life Senile = first seen in middle aged to older animals (no defined cut off between juvenile and senile)

Answer 13

Cataracts where there is genetic basis - clinical features and morphological changes vary breed to breed.

Answer 14

Heat Shock Factor 4 Boston Terrier (also suffers from secondary type of hereditary cataract as well), French Bulldog, Staffordshire Bull Terrier Autosomal recessive - early onset and progressive cataracts - posterior suture lines Base pair deletion for HSF4 in the Australian Shepherd - dominant with incomplete penetrance hereditary cataracts - posterior cortical or subcapsular.

Answer 15

Belgian Shepherd, Golden Retriever, Labrador Retriever, Irish Setter, Giant Schnauzer, Large Munsterlander, Leonburger, Chesapeake Bay Retriever, Siberian Husky. Triangular or propellar shaped posterior polar subscapsular with occasional progression to extensive and generalised cortical cataract (Progression of disease more likely in the Husky - other breed seldom progresses to have significant effect on vision) Unknown mode of inheritance

Answer 16

Age of onset not well defined but do show typical changes in middle aged to older dogs. Type of primary cataract aetiology. Generally nuclear - opacification of nucleus alongside nuclear sclerosis and/or wedge shaped or diffuse cortical cataract formation in early stages. Slowly progressive type of cataract - vision loss after months to years

Answer 17

Diabetes mellitus Main pathway for glucose metabolism in lens = anaerobic glycolysis, rate of which is determined by enzyme hexokinase. Once the glucose levels become too high relative to the levels of hexokinase an alternative pathway of glucose metabolism is invoked using the enzyme ALDOSE REDUCTASE. Glucose metabolised by aldose reductase and produces SORBITOL Increases the OSMOTIC POTENTIAL of the lens attracting in water and causing COAGULATION OF LENS PROTEINS. Typically lenses of diabetic patients develop water clefts due to the increase in lens volume INTUMESCENCE that occurs as fluid enters the lens capsule.

Answer 18

Clefting (entrance of water into lens and increase in lens volume) tends to occur along suture lines of the lens because these are the weakest point of the lens.

Answer 19

Alpha Lipoic Acid - aldose reductase inhibitor Once cataract has formed however cannot be reduced medically.

Answer 20

Hypocalcaemia

Answer 21

Phacolytic and Phacoclastic uveitis - risk of then developing secondary glaucoma.

Answer 22

Cats - by age of 5 diminished amount of aldose reductase therefore less use of this alternative glucose pathways to convert glucose to sorbitol.

Answer 23

Perinuclear cataracts Reported in puppies fed on certain types of milk replacer May be partially reversible cataracts. Diets deficient in certain proteins and vitamins may also lead to some cataract formation.

Answer 24

Blunt trauma - vibration injury to the lens material or lens instability due to damage to the lens zonules. In very severe blunt trauma, compressive forces can lead to rupture of the globe leading to expulsion of the entire lens. Penetrating trauma - claws, thorns, teeth, foreign bodies etc. Teeth - tend to have compressive force as well and so injury that occurs to the lens is more severe and vision threatening. Thorns/claws may appear to only cause minor injuries to the outer structures of the eye but can have devastating impact on lens. All animals presenting with corneal injuries should have the lens also assessed in case the lens capsule has been compromised. Pupil dilation essential to assess lens properly after injury (so long as no lens instability noted) as the insult may have occurred at the periphery of the lens even with central corneal injuries.

Answer 25

Penetrating corneal injury may cause either penetrating or non penetrating lens injury. Penetrating = rupture of lens capsule Non penetrating = lens capsule remains intact but there may be focal or complete cataract development due to disruption of the anterior lens capsule epithelial cells.

Answer 26

If capsule has been breached - need to decide whether will reseal or if the lens will need complete removal as leakage of lens proteins leads to a phacoclastic uveitis due to a lack of immune tolerance to this large amount of liberated lens protein or as the result of bacterial contamination (can also get septic implantation syndrome several weeks to months later) Usually lens capsule tears are significantly beyond the area originally damaged making it unlikely the capsule will reseal.

Answer 27

Early phacoemulsification surgery to remove lens contents = better success than medical management alone. Better to refer patients early if suspect have had lens capsule damage.

Answer 28

Corneal injury reduces visualisation of lens Compromised lens capsule increased risk of nucleus being lost into the vitreous as well as precluding the placement of a replacement intraocular lens in some cases.

Answer 29

Aggressive therapy with systemic and topical anti-inflammatories needs to be instigated + systemic and topical management of the corneal injury and intraocular bacterial contamination.

Answer 30

Any disease which changes the physiological balance of nutrients in the eye, releases toxic metabolites or increases inflammatory mediators may lead to cataract formation. Common intraocular diseases that are associated with cataracts includes: 1. Progressive Retinal Atrophy (PRA) 2. Glaucoma 3. Lens luxation 4. Uveitis Exact mechanisms are poorly described.

Answer 31

Electrocution Radiation - animals undergoing radiotherapy where the eye is close or within the treatment field. Rare causes of cataracts in domestic animals.

Answer 32

Incipient Immature Mature Hypermature Most useful classification in terms of vision and risk of secondary problems.

Answer 33

Incipient = <15% of lens volume involved Rarely associated with visual disturbance due to low volume of lens affected. Vacuoles may be seen and are often cited as a sign of cataract progression but many incipient cataracts will have vacuoles that persist for many years with no discernable change in lens opacity.

Answer 34

Immature = covers a range of cataracts from those just over the >15% lens volume to an almost complete cataract but where the lens still has some transparency. Tapetal reflex can still be seen on distant direct ophthalmoscopy and in less advanced cases the fundus can still be examined by indirect ophthalmoscopy with the pupil dilated. Group can be further subdivided into early and late immature cataracts depending on the degree of opacity noted.

Answer 35

Mature cataract = visual axis opaque with loss of tapetal reflex and menace response. Lens may not be completely opaque for entire volume but it is across the visual axis - EYE IS BLIND Eye retains PLR and Dazzle assuming that there are no other abnormalities as passage of light to the fundus is disrupted but not blocked.

Answer 36

Hypermature cataract = Mature cataracts start to liquify and resorb leading to various changes. 1. Lens may reduce in volume and develop clefts along suture lines - lens proteins then leak through the lens capsule and white plaques develop that adhere to the inner aspect of the lens capsule leading it to develop wrinkling. 2. May be restoration of the tapetal reflex which can make differentiation of immature and early hypermature cataracts difficult. 3. In some dogs lens resorption may be sufficient to lead to the return of some vision as the visual axis clears - however this seldom occurs as often secondary vision threatening problems have occurred by this stage - phacoclastic/phacolytic uveitis, glaucoma or retinal detachment.

Answer 37

Capsular - usually insignificant unless traumatic Subcapsular - area of new lens growth therefore more likely to worsen with time Cortical - less metabolically active, typically seen with senile cataracts, progressive but often slow Nuclear - usually non progressive, becomes less of the lens volume over time and new material laid down over time.

Answer 38

Anatomy of lens - capsular, subcapsular, cortical, nuclear Position along lens axis - e.g anterior cortical or posterior cortical Position along visual axis - e.g axial, para axial, equatorial. E.g Labrador and Golden Retreviers - Posterior polar subcapsular hereditary cataracts at confluence of suture lines.

Answer 39

1. Hereditary 2. Production of a harmful metabolite 3. Accumulation of a normal metabolite (e.g sorbitol in diabetic cataracts) 4. Loss of an important metabolite 5. Dietary deficiency (e.g milk replacers in puppies) 6. Radiation 7. Oxidative injury 8. Secondary to retinal degeneration (e.g PRA) 9. Traumatic

Answer 40

1. Increase in high molecular weight and insoluble proteins - albuminoids 2. Shift in the relative concentrations of crystallins - alpha, beta and gamma 3. +/- decreased activity of Na-K ATPase pump 4. Increase in sodium/calcium content 5. Decrease in potassium content 6. Decreased oxygen consumption and ATP production 7. Anti-oxidant activity diminished 8. Increase in level of disulfide bonds 9. Hydrolytic and proteolytic enzyme activities increase 10. Eventual cell membrane rupture, loss of low molecular weight proteins and an increase in water content.

Answer 41

Leakage of lens protein associated with cataract progression and resorption, leads to an antigenic response, anti-lens crystallin antibodies decrease with cataract = phacolytic lens induced uveitis Phacoclastic uveitis = lens rupture leading to exposure of the lens protein Granulomatous inflammation set up - mononuclear and neutrophil response May occur due to swelling of the lens (intumescence) - often seen with rapid onset cataract progression e.g diabetic cataracts. Associated changes = mild episcleral hyperaemia, hyperpigmentation of the iris, reduced IOP, iris rest formation. If left untreated chronic ongoing uveitis that can result in glaucoma.

Answer 42

Subset of hypermature cataract - significant resorption of lens material but dense nuclear cataract remains which eventually falls into the inferior portion of the capsular bag.

Answer 43

Aging change within the lens Occurs as throughout life there is the continual production of anterior epithelial cells which leads to compression of the lens nucleus. Change in refractive index of the lens nucleus compared with the newer cortex which makes the nucleus appear blue/grey when viewed with the naked eye. Can be differentiated from cataract on distant direct ophthalmoscopy - absence of lens opacity (normal tapetal reflection)

Answer 44

Generally has little effect on vision but in some severe cases can notice visual changes particularly at short distance.

Answer 45

Thickening Wrinkling Plaques Rupture Vascular plaques Pupillary membrane remnants.

Answer 46

Weld or bladder cells (swollen nucleated lens cells) - indicator lens under duress and precursor to cataract formation Degeneration or necrosis

Answer 47

Developmental defect in which a smaller more spherical lens develops with partial or complete aplasia of the zonules.

Answer 48

Subluxation = partial displacement of the lens from the hyaloid fossa + partial displacement of the lens from the central visual axis.

Answer 49

Luxation = total displacement of the lens from the hyaloid fossa - either into the anterior chamber (anterior luxation) or into the posterior chamber (posterior luxation)

Answer 50

Primary - hereditary (Jack Russell Terrier, + other Terrier breeds, Yorkshire Terrier, Border Collie, Shar Pei) ADAMTS17 gene (terriers)- recessive condition Age of onset usually 3-7 years (may occur in GSD and Springer Spaniel at later age) Usually progressive and can lead to blindness due to acute glaucoma with anterior lens luxation. Secondary = acquired lens luxations - Glaucoma (stretching of the lens zonules) - Trauma - Chronic uveitis (especially cats) - hypermature cataracts also - Mass induced displacement - Idiopathic zonular degeneration

Answer 51

Can sometimes be challenging Look at breed - is it predisposed to primary lens luxation? Chronicity - is the globe buphthalmic (sign of chronic glaucoma), haab's striae etc

Answer 52

Usually bilateral and hereditary but one eye will often present first. Care should always be taken to assess contralateral eye for signs of instability. Profile of the iris may give an idea as to whether lens supporting iris based on shape - normal convexity.

Answer 53

- Change in iris convexity - Iridodonesis (subtle iris tremble as the eye moves) - Phacodonesis (subtle lens trembling as the eye moves) - Anterior displacement of vitreous through the pupil which may be accompanied by pigment (other ddx vitreous degeneration so on its own not pathognomonic for lens luxation) -Loss of anterior lens surface reflection - Increased anterior chamber depth - Aphakic cresent between pupil margin and kens

Answer 54

Fibrillin 1 = main component of zonules Production of fibrillin 1 affected in ADAMTS17 dogs - weaker lens zonules and eventual breakdown.

Answer 55

Anterior lens luxation = lens in anterior chamber Clinical signs: Pupil obscured by lens (easier to see if lens cataractous) Glaucoma (scleral injection, raised IOP, blepharospasm/pain, blindness, diffuse corneal oedema) Uveitis Focal oedema where lens touches corneal endothelium

Answer 56

Lens moves into anterior chamber = pupil block, lack of drainage of AH through the iridocorneal angle. Triggers uveitis - production of inflammatory reaction (hypopyon, aqueous flare) etc that then block the iridocorneal drainage angle.

Answer 57

Posterior lens luxation more difficult to identify - less likely to present with the severity of signs associated with anterior lens luxation (not causing blockage to iridocorneal angle) Main signs = anterior presentation of vitreous, increased in anterior chamber depth and iridodonesis.

Answer 58

SURGERY - always recommended for anterior lens luxations due to glaucoma risk Prompt referral to specialist advised. Completely luxated lens - intracapsular lens extraction (ICLE) often method of choice Some subluxated lens may choose to use phacoemulsification. Some surgeons will recommend prophylactic removal of lens in other eye at same time due to the risk of it also developing an anterior lens luxation in the future (if likely primary lens luxation) as the surgery is easier to perform at this stage and reduces the risk of acute glaucoma/corneal damage to the eye by preventing the anterior luxation.

Answer 59

Couching the lens Animal sedated/GA Pupil dilated Lens manipulated posteriorly by pushing eyelids against anterior chamber with head raised Once lens manipulated into posterior chamber - start prostaglandin analogues (usually latanoprost) to cause miosis and trap pupil in posterior chamber, also treats the glaucoma. Prostaglandin analogue then continued long term to keep lens trapped behind pupil - effectively made it a posterior lens luxation.

Answer 60

Generally tend to manage medically (no difference in outcome surgical vs medical anecdotally so far) Prostaglandin analogues - BID long term (e.g latanoprost) to induce miosis Risks: Care must be taken that the pupil remains permanently miotic - prostaglandin analogues have variable duration of effect so some dogs may require more than BID dosing to maintain miosis consistently. If treatment missed and lens moves anteriorly then further application of prostaglandin analogue contraindicated as will worsen pupil block glaucoma - risk O's may not notice and apply as usual when lens has moved anteriorly. Older animals - iris atrophy may limit effectiveness of the prostglandin analogue in causing miosis If anterior vitreal presentation miotics risk causing vitreal entrapment within the pupil which can lead to pupillary block and acute glaucoma.

Answer 61

Medical management pros: Cheaper than surgery Less risk of retinal detachment complications` No GA for older patients Medical management cons: Can be intensive for owners in order to achieve constant miosis Iris atrophy in older animals may limit effectiveness Vision loss due to severe pupil miosis Cataract development in subluxation Glaucoma management still often required Can stil sometimes see retinal detachments very rarely Rebound pupil miosis - increased risk for anterior displacement. Surgery pros: Allows lens replacement (artificial lens) Much more successful for anterior luxations Surgery cons: Expensive upfront Some animals will still need ongoing medical therapy alongside Vision loss may still occur due to glaucoma or retinal detachments.

Answer 62

Emmetropia = normal focus Hyperopia = long or far sighted Myopia = short or near sighted Most dogs emmetropic. Deviations from normal may be due to change in refractive power of the lens or the corneal curvature or size (axial length) of eye. Retinoscopy can be used to assess refractive errors and the corrective power of synthetic intraocular lenses.

Answer 63

Other intraocular disease e.g chronic uveitis/glaucoma Lens diseases rarely primary in cats.

Answer 64

Persistent Pupillary Membranes (less common - may be seen associated with upper eyelid colobomas) Peter's Anomaly Aphakia/Microphakia Persistent hyperplastic tunica vasculosa lentis/Persistent hyperplastic primary vitreous - sporadically occurs in cats but rare Macrophakia - posterior pole almost touching retina, seen in 3 cats, concurrent retinal folds described but no cataracts at initial presentation. Congenital cataracts - very uncommon

Answer 65

Risk of intraocular sarcoma formation in the short or long term (often months-years after the incident)

Answer 66

Chronic uveitis (signs often more subtle for uveitis in cats so go unnoticed until later stages) Glaucoma - expansion of the globe and tearing of the zonules. (Very rarely - trauma, often lots of other signs of trauma due to amount of force needed to displace lens in cats).

Answer 67

Anterior lens luxation Justified as an anteriorly luxated lens will cause dense, focal corneal oedema, become cataractous and contribute to further introcular inflammation. (However many of these cats already blind/painful from chronic uveitis/glaucoma and in some cases may elect to enucleate globe instead). Post op complications - ongoing uveitis, glaucoma or retinal detachment.

Answer 68

Cataracts Lens luxation Lens instability/subluxation Foreign body removal Lens capsule rupture (e.g trauma) - phaco Surgical approach to another part of eye in retinal re-attachment surgery, endocyclophotocoagulation for glaucoma or tumour removal.

Answer 69

Intracapscular = removal of lens within its capsule Extracapsular = incision into the capsule to remove the lens contents (often used phacoemulsification as an extracapsular technique now rather than ECLE) ICLE indication - anterior lens luxations ECLE indications - tiny minority of cataract procedures where phacoemulsification not possible due to excessively hard lens.

Answer 70

1. Assess and discuss general health of the patient - are there other concurrent diseases etc 2. Discuss advantages and disadvantages of performing the procedure with the owner and the risks and complications + need for often intensive medical aftercare and regular re-evaluations - are owners able to commit to this? 3. Progressive, late or mature cataracts = main types operate on although immature cataracts often better success rates as less pre-existing lens induced uveitis and softer lens - reduces surgical time + use of ultrasound energy. 4. Ideal candidate - good physical health, no existing or predisposition to other intraocular disease and immature progressive cataracts. 5. Diabetic patients generally good candidates assuming diabetes well controlled but remember their cataracts can progress quickly and that advanced cataracts = higher risk of complications. EARLY REFERRAL DIABETIC CATARACTS ADVISED.

Answer 71

1. Full clinical examination of the patient (diabetics - recent blood work, urinalysis etc) 2. Full ophthalmic examination including tear production, gonioscopy and IOP (checking for any other concurrent ocular disease/predisposition) 3. Ultrasonography - assess for lens capsule rupture, posterior lentiglobus or lenticonus, persistent and patent hyaloid artery, vitreous degeneration or vitreal/retinal detachments. (None of these factors precludes surgery but they may significantly alter the surgical approach or the likely success of this procedure restoring vision e.g if concurrent retinal detachment) 4. Electroretinography (ERG) - where unable to assess retina ophthalmoscopically or there is a concern about retinal function (Cataracts seen associated with PRA in breeds such as the Labrador, Cocker Spaniel, Poodle etc and retinal function should be considered suspect if there is any history of night blindness, PLRs slow or incomplete or inappropriate amount of pupil dilation in normal lighting conditions - if PRA diagnosed decision can be made on whether surgery beneficial for short-medium restoration of some visual capacity)

Answer 72

Patient prepping - as for general ocular surgery (clip hair, povidone iodine, rinse ocular surface with saline) Positioning - dorsal recumbency, medial and lateral canthus horizontal, upper and lower eyelids horizontal Magnification - operating microscope set up and positioned Lateral canthotomy - increase exposure (novice surgeons, cats) Stay sutures or neuromuscular blockade to keep eyes central (Stay sutures - placement through sclera away from surgical entry points, ensures fixed globe position, counters any rotation and can elevate globe/ use to move third eyelid out of the way) (Neuromuscular blockade - reduces need for stay sutures, reduces tension on globe and risk of vitreal displacement, enables access to ventromedial globe at all times, prevents vitreal push)

Answer 73

One handed and two handed approaches - this describes 2 handed approach to cataractous lens without other complications. 1. 2-3mm incision made at limbus 2. Injection of viscoelastic (hyaluronic acid) into anterior chamber to maintain its depth - essential for formation of second entry port and the anterior capsulorrhexis and to protect corneal endothelium from damage 3. 2nd incision made similar to 1st but smaller width 4. Anterior capsulorrhexis - curvilinear technique aiming to create smooth edged circular hole slightly smaller diameter to the synthetic lens in the centre of the capsule. Staining the anterior capsule blue with trypan blue can aid with visualisation of the capsule. 5. Phacoemulsification - needle advanced through the port and into the lens. Combination of irrigation, ultrasound vibration and vacuum the lens material is broken down and aspirated from the eye. 6. Irrigation and aspiration - remaining lens cortex attached at equator - irrigation/aspiration handpieces which had rounded tip and no ultrasonic power are used to reduce the risk of lens capsule rupture. Lens capsular bag is polished to remove as many of the remaining lens epithelial cells as possible. 7. Synthetic intraocular lens placement - capsule reinflated with viscoelastic and the folded intraocular lens is injected through the larger entry port into the capsular bag before positioning with lens manipulators. 8. Remaining viscoelastic aspirated from the eye 9. Entry ports are sutured (cornea) and eye re-inflated with balanced salt solution.

Answer 74

Irrigation, Aspiration and provide Ultrasonic phacofragmentation of the lens.

Answer 75

Iris prolapse Hyphaema Pupil miosis - poor access Pre-iridial fibrovascular membranes - poor access to the lens capsule/haemorrhage Vitreous prolapse occluding needle Anterior chamber collapse Capsular rupture Nucleus of lens drops into vitreous Lens dislocation Iris trauma Corneal burn Synthetic lens tearing Aqueous humour leakage from corneal entry points - wound dehiscence Retinal detachment

Answer 76

In immediate post op period treated eyes can experience raised IOP (post operative ocular hypertension) All lendectomy patients should have their IOP carefully monitored.

Answer 77

All intraocular surgery = induces degree of uveitis and managing this is key to good longer term outcomes.

Answer 78

Topical - Prednisolone acetate 1% twice daily - Diclofenac 1% 6x daily (NSAID) - Brinzolamide 2x daily (carbonic anhydrase inhibitor - manage initial post operative hypertension Oral - NSAID - typically meloxicam for 2 weeks - Antibiotics - typically cephalexin (good intraocular penetration) for 5 days

Answer 79

Topical - Prednisolone acetate 1% 6x daily - Brinzolamide 2x daily Oral - NSAIDs - meloxicam once daily for 2 weeks - Antibiotics - cephalexin for 5 days

Answer 80

7.6-10% failure rate Post op complications: - Glaucoma (esp Labradors) - Retinal detachment (esp Yorkies/Bedlington Terriers) - Posterior capsular opacification -Corneal oedema - Corneal ulceration - Posterior synechiae between iris and lens capsule or synthetic lens - Endophthalmitis

Answer 81

24 hrs hospitalised and IOP monitored = both types of patient 1 week later - diabetic stops prednisolone and brinzolamide but continue diclofenac. Non diabetic reduces prednisolone and stops brinzolamide. 1 month later - diabetic reduces diclofenac, non diabetic reduced prednisolone 3 months later- non diabetics can stop all treatment if no complications and are reviewed annually 4 months later - diabetics reduced to once daily diclofenac and remain on this for life with reviews annually

Answer 82

Main indication = anterior lens luxations 1. Initial incision = half depth corneal groove 170 degrees adjacent to limbus 2. One end of groove incised completely taking care not to penetrate lens if luxated anteriorly 3. Viscoelastic injected to inflate anterior chamber and protect corneal endothelium, injected posteriorly to break down hyaloidcapsular ligament. 4. Corneal incision extended with corneal scissors along length of original cut 5. Lens removed using a lens loop or lens vectis forceps and any remaining vitreal attachments cut away (Optional - synthetic intraocular lens can be placed by suturing the hapatic arms of the lens through the ciliary sulcus between iris and ciliary body) 6. Any anteriorly displaced vitreous is then cut away ideally using automated vitrectomy but manual vitrectomy using scissors and cellulose sponges also effective 7. Corneal incision closed in continuous pattern and the eye re-inflated using balanced salt solution.

Answer 83

70% eyes retain vision after ICLE with implantation and suture fixation of intraocular lens

Answer 84

Occurs after cataract surgery as a consequence of contraction of the capsule and/or posterior migration of epithelial cells. Dogs = seldom causes noticeable visual deficits even in advanced cases. If is causing issues then opacified capsule can be removed by excision or laser capsulotomy (YAG) - but does carry risk of damaging the lens optic.

Answer 85

Has to be clear in order to keep visual axis transparent as possible. Provides structural support to the retina Nutritional and metabolic support to retina and lens. Maintains shape and volume of the eye Storage site for retinal metabolites and waste products to safeguard lens from potential harmful substances - glycogen, free radicals, potassium, lactate.

Answer 86

Vitreous with normal consistency = deposits of lipid occur in focal particles throughout the vitreal gel. Movement of the globe shows the normal movement of the gel and therefore the bodies but they return to their normal position once glove movement has ceased. Noted as an ageing change and secondary to generalised PRA in some breeds e.g Poodles. On own do not appear to affect vision but can cause visual disturbance in common with other visual axis opacities e.g nuclear sclerosis, cataracts, corneal disease Lipid deposit but is not a result of any lipid pathology. Clinically seen as particles that move with the movement of the eye - swirl and then move back to where they were when eye static.

Answer 87

Clinically similar to asteroid hyalosis but cholesterol deposits rather than lipid in liquified vitreous. Globe movement results in snow globe type movement of deposits before they settle back down - particles fall ventrally then return to different location. Sign of vitreal degeneration, may also be a change from asteroid hyalosis.

Answer 88

Pigment dispersal syndromes e.g Pigmentary uveitis in Golden Retriever Haemorrhage in vitreous - may present later down the line as pigmentation.

Answer 89

Bleeding from persistent hyaloid artery Systemic hypertension Coagulopathies Neoplasia - haemorrhage from ciliary body or fundus PHTVL/PHPV Collie Eye Anomaly Geographic retinal dysplasia Multifocal retinal dysplasia Retinal tears/detachments

Answer 90

Inflammation of the vitreous - secondary to inflammation of adjacent structures Inflammatory cells can migrate across the vitreous to the ciliary body and posterior lens. Primary vitreal inflammation unusual but can include infectious causes - cryptococccosis/brucellosis. Long term consequence of vitreal inflammation/haemorrhage = vitreal membranes- glial scars which predispose the eye to retinal detachment.

Answer 91

Dirofilaria and Toxocara can be found alive in the vitreous

Answer 92

Aging vitreous becomes less solid - may separate from the inner limiting membrane of retina and fall ventrally. Little clinical significance - space vacated by vitreous is filled by the aqueous humour. May be mistaken for retinal detachment on ultrasonography.

Answer 93

Shih Tzu and JRT Early changes in vitreous base noted include marked opacification, liquefaction, pigment migration and hamorrhage. Heavy head shaking associated with further vitreal base breakdown/movement leading to traction being applied to peripheral retina - this in turn leads to disinsertion of the ora cilliaris and early detachment.

Answer 94

Whippets and some older dogs Otherwise associated with breakdown of lens zonules (subluxation)

Answer 95

Sit lamp biomicroscopy - anterior vitreous directly, posterior vitreous with indirect lens Vitreocentesis - can be sampled through the pars plana BUT risk of intraocular haemorrhage that can be globe threatening so very rarely performed and if so generally on non visual eyes. Ultrasonography - excellent way of assessing the vitreous and can be more sensitive than visual assessment for detecting pathology.

Answer 96

Usually performed as part of lens removal surgery Anteriorly prolapsed vitreous associated with lens luxation and incarcerated vitreous in corneal entry wounds needs to be avoided as risks retinal detachment. Manual vitrectomy = PVA sponges to adhere to the vitreous and with gentle traction allows the vitreous to be cut with scissors. Mechanical vitrectomy = Vitrector will use a guillotine or rotary cutter to aspirate and cut the vitreous - less traction than manual approach but requires a phacoemulsification machine to operate the vitrectomy hand piece. Mechanical vitrectomy also performed as part of retinal re-attachment surgery. All of the vitreous including that which has moved deep to the retina has to be removed in order to successfully re-attach the retina.

Answer 97

Post vitrectomy - balanced salt solution - allows space to fill with aqueous long term Retinal reattachment surgery - vitreous replaced with medical grade silicon oil to provide retinal tamponade and prevent further detachment.

Lens & Vitreous Flashcards

(124 cards)