Ophtalmo Flashcards

Question

What is the suspected etiology of congenital stationary night blindness in Tennessee Walking Horses ?

Answer 1

We identified a likely causal **recessive missense variant in GRM6**. The estimated allele frequency in Tennessee Walking Horses is 10%. ## Footnote Whole-genome sequencing identifies missense mutation in GRM6 as the likely cause of congenital stationary night blindness in a Tennessee Walking Horse evj 2020

Answer 2

No ## Footnote Evaluation of transpalpebral ultrasonographic measurement of optic nerve sheath diameter for indirect assessment of intracranial pressure in anesthetized and standing healthy adult horses J Vet Emerg Crit Care 2021

Answer 3

74% had **anterior segment pathology** (Cobs and Shetlands) → **cataract** (52%), mostly **anterior cortical** (65%) 44% had posterior segment pathology : **senile retinopathy** (43%) 71% were **bilateral** ## Footnote Ocular findings in a population of geriatric equids in the United Kingdom ejv 2024

Answer 4

**No** Further study will be needed to determine whether amniotic membrane extract will be helpful for infected or malacic equine corneal ulcers. ## Footnote Commercial amniotic membrane extract for treatment of corneal ulcers in adult horses evj 2021

Answer 5

**Keratomalacia**, or **corneal melting**, results when there is an **overabundance** of these enzymatic proteins elaborated by recruited inflammatory cells, activated resident host cells, and any pathogens present. The **destructive forces overwhelm** the restorative responses and result in dissolution of corneal collagen and necrosis of cells. The production of elastase and alkaline phosphatase by **Pseudomonas**, hyaluronidase by **Staphylococcus** and other extracellular proteases by **fungal** organisms can greatly augment this melting process.

Answer 6

- Often, especially in corneas infected with **fungi**, a **groove or furrow** will develop at the periphery of the lesion owing to increased concentrations and activity of proteases elaborated both by host tissues and the pathogens. - Infections that travel to the deeper layers of the cornea, especially **fungal organisms that are chemoattracted to Descemet’s membrane**, are more likely to result in a full-thickness rupture. - Most cases of **corneal abscesses** in the horse are fungal in origin.

Answer 7

Amniotic membrane transplantation for **superficial wounds** may provide **excellent cosmetic results** and minimize corneal opacity. However, it is **not recommended** for reconstruction of deeper lesions or instances of fungal keratitis.

Answer 8

**Season** (depends on location) → spring and fall in Colorado **Wind speed** → with higher wind speeds associated with greater rates of fungal involvement ## Footnote Prevalence of equine ulcerative keratomycosis in Colorado and association of environmental factors: A retrospective and descriptive study (2002–2017) eve 2021

Answer 9

Overall complication rate for SPL systems was **29.1%**, with 21.2% being ocular complications and 7.9% being nonocular complications. The authors talk about "low complication rates" but... ## Footnote Dorsally placed commercially available subpalpebral lavage systems have low complication rates in horses javma 2022

Answer 10

**Congenital**, **primary** and **secondary** glaucoma Secondary to : * **chronic uveitis (ERU ++)** * trauma * hyphema * intraocular neoplasia * lens luxation * postcataract surgery

Answer 11

- Active, recurrent, and chronic/persistent **uveitis** - **Age > 15 yo** - Breed (**Appaloosa**)

Answer 12

- Combination of topical β-blocker **0.5% timolol** and the topical CA inhibitor **2% dorzolamide** used every 8-12h. The combination is more effective than when administered alone. Potential adverse effect of timolol : miosis - Another CA inhibitor : **brinzolamide**

Answer 13

**Transcleral cyclophotocoagulation (TSCP)** is considered the therapy of choice for long-term IOP control in horses. This is indicated in **visual eyes**. Contraindicated in the presence of intraocular neoplasia. Pre-existing ocular conditions, such as uveitis, should be controlled before laser therapy to minimize complications.

Answer 14

The most common bacterial genera were **Streptococcus** (35%), **Staphylococcus** (29%) and **Pseudomonas** (13%), with a shift towards **more Staphylococcus** and less Streptococcus compared to previous years. Same susceptibility. ## Footnote Monitoring trends in antimicrobial susceptibility patterns of bacterial isolates from horses with ulcerative keratitis eve 2023

Answer 15

The **rebound tonometer** may be the preferred instrument to **minimise intra-user and inter-user variation** for IOP measurement in unsedated horses. The rebound tonometer is also likely to be the preferred instrument to minimise intra-user variation in sedated horses. If the **applanation tonometer** is used to perform IOP measurement in horses, it is recommended that this is performed **while horses are sedated** to minimise inter-user variation for this instrument. ## Footnote Inter-user and intra-user variation of two tonometers in horses evj 2020

Answer 16

IOP should be estimated using the same tonometer over time, and the bias of the tonometer used, such as **overestimation** (**rebound tonometer**) and **underestimation** (**applanation tonometer**), should be acknowledged. ## Footnote Comparison of four tonometers in the measurement of intraocular pressure in healthy horses evj 2023

Answer 17

A notable **increase in IOP** was observed in the **medical barn** compared with the horse stable, while tear production exhibited no significant variance between the two environments. ## Footnote Comparing the effects of intraocular pressure and tear production measurements in horses in two different environments: Horse stable and medical barn evj 2024

Answer 18

All protocols of sedation **decreased IOP** compared with baseline, with greatest reduction at +5 min. A combination of **detomidine and butorphanol** causes **greater IOP reduction** 5 minutes following sedation than other commonly used sedation protocols. IOP reduction is less pronounced when detomidine is used alone. ## Footnote Intraocular pressure following four different intravenous sedation protocols in normal horses evj 2021

Answer 19

Facial nerve damage secondary to trauma such as mandibular fracture

Answer 20

**CN III** dysfunction results in a laterally and lightly ventral strabismus, **CN VI** results in a prominent globe with a medial strabismus, **CN IV** deficiency results in a dorsomedially rotated pupil.

Answer 21

Appaloosas with congenital stationary night blindness will often have a **characteristic dorsomedial strabismus**. A dorsomedial rotation can also be seen with **cerebellar abiotrophy** in Arabian horses.

Answer 22

**Horner syndrome** is the result of a **loss of sympathetic innervation** to the head. Manifestations include **head sweating, upper eyelid ptosis**, and **mild miosis**. Enophthalmos and elevation of the nictitating membrane are inconsistently found and can be subtle. It is more commonly associated with **guttural pouch disease**.

Answer 23

**SCC** is the most common neoplasm of the globe and adnexa in the horse. Clinically, SCC typically presents as a **fleshy pink growth** on the **nictitating membrane, conjunctiva, eyelid, or limbus**.

Answer 24

- In general, **ocular SCC** is **locally invasive** and **slow to metastasize**. The prognosis for the treatment of SCC is **good** if lesions are identified and treated when they are small. - **Surgical excision** is relatively *unsuccessful* if performed alone, but **adjunctive treatment** with radiation, cryotherapy, CO2 laser ablation, photodynamic therapy, application of mitomycin C, or a combination of treatments significantly *improves outcome*. - The exception seems to be **SCC of the nictitating membrane**, which has a *good prognosis* after surgical excision with a very low recurrence rate. - Recurrence rates after excision are **higher** in **eyelid SCC** as compared with other locations

Answer 25

- **increasing age** - **ultraviolet radiation** - **unpigmented skin** - a genetic link with an autosomal recessive mode of inheritance has been suggested in **Halflingers**

Answer 26

- Although *good results* can still be achieved for periocular sarcoids, as treatment is most successful when **lesions are small** it is paramount to treat with the most effective therapies available **early** in the course of disease. - Due to wide, poorly defined margins, **recurrence rates** after surgical excision of sarcoids are **high**, as high as 82% in the periocular area where there is **limited tissue for resection**.

Answer 27

**Retrobulbar** injection using **10 mL lidocaine is safe** in normal eyes of adult horses, but carries **risk** in structurally **compromised** or **glaucomatous** eyes due to **transient IOP increase**. **Reversible chemosis** commonly develops **2- 4h following injection**, and may be severe in some horses with risk for **corneal ulceration**. ## Footnote Retrobulbar lidocaine injection via the supraorbital fossa is safe in adult horses but produces regionally variable periocular anaesthesia evj 2022

Answer 28

**Low-volume (5 mL)** retrobulbar block was not associated with adverse effects. In terms of efficacy, mepivacaine block showed no clinical advantage over **lidocaine** block. However, **bupivacaine** block induced comparatively rapid and sustained corneal anesthesia. Corneal anesthesia was similar but periocular soft tissue anesthesia was not achieved with any local anesthetic drug at low volume. (50% reduction volume improves the safety) ## Footnote Comparative efficacy of low-volume retrobulbar anesthesia using three commercial local anesthetics in adult horses javma 2024

Answer 29

**Refinement and revalidation of the Equine Ophthalmic Pain Scale (R-EOPS)** may be an effective tool for reliably assessing the pain level in horses with ophthalmic diseases and potentially guiding pain management although it still requires large-scale application and external validation. Another recent study also used the **Horse Grimace Scale (HGS)** and **Behavior Pain Score (BPS)** (but not validated) ## Footnote Refinement and revalidation of the Equine Ophthalmic Pain Scale: R-EOPS a new scale for ocular pain assessment in horses vet J 2024 Pain scoring systems in hospitalized horses with ocular disease jvim 2024

Answer 30

Both short- and long-term results indicate diode laser treatment is a **useful and safe option for iris cyst size reduction**, with a **low risk of recurrence**. Factors are associated with less satisfactory response : - polycystic eyes - thick-walled cysts - hyperplastic corpora nigra Presurgical **ultrasonography** is recommended ## Footnote Noninvasive diode laser–an effective and safe treatment of iris cysts in 46 eyes of 35 horses evj 2023

Answer 31

The exact mechanism of induction of uveitis and the pathogenesis of how the bacterium is associated with the recurrences is not completely understood. Leptospira may account for the **initial blood–ocular barrier disruption**, which then triggers the subsequent **immune reaction**. Increased intraocular antibodies compared with the serum are indicative of **local intraocular antibody production** (**C-value**), with **MAT** (high Se and Spe). **C-value ≧ 4 : positive**, the aqueous humour Ab titre is at least four-fold higher than the Ab titre found in the serum. C-value ∈ [1-4] : suspicious C-value < 1 : negative **PCR** results are an **unreliable method** of detecting the presence of Leptospira. ## Footnote Equine recurrent uveitis— A review EVE 2023

Answer 32

Equine recurrent uveitis is generally considered to be an **autoimmune disease**. The disease's onset and severity may be associated with **environmental factors** and/or **genetic predisposition** (Appaloosa with LP allele). It is commonly accepted that ERU develops due to **blood–ocular barrier disruption** following an initial bout of inflammation. Following disruption of the local immunity, CD4+ and T-lymphocytes gain access to the eye, where they remain. ## Footnote Equine recurrent uveitis— A review EVE 2023

Answer 33

The most common intraocular serovars were Leptospira interrogans **grippotyphosa**, **pomona**, and **bratislava**. Intraocular antibody production was suspected in samples of 22/65 horses (c-values > 1). ## Footnote Leptospiral antibody prevalence and surgical treatment outcome in horses with Equine Recurrent Uveitis (ERU) in Switzerland vo 2020

Answer 34

PPV was performed in 21 eyes with **positive** leptospiral test results, SCDI in 15 eyes with **negative** leptospiral test results. (*Not the same population compared*) Uveitis recurred **less often after PPV** (2/21) compared to SCDI (6/15, P = .04), but with an increased risk of **retinal detachment**. **Enucleation** was more often warranted in horses after **SCDI** in this study due to a higher uveitis recurrence. ## Footnote Leptospiral antibody prevalence and surgical treatment outcome in horses with Equine Recurrent Uveitis (ERU) in Switzerland vo 2020

Answer 35

- **Age**, - **coat pattern** (**fewspot coat pattern** was significantly associated with increased risk for ERU), - **genetics** (The **LP/LP genotype** was at a significantly greater risk for ERU compared to lp/lp (OR = 19.4) and LP/lp (OR = 6.37)). → are major risk factors for the diagnosis and classification of ERU in the Appaloosa ## Footnote Risk factors for equine recurrent uveitis in a population of Appaloosa horses in western Canada vo 2020

Answer 36

The ERU prevalence in donkeys reported here **(2.9%)** is **comparable** to that reported for horses in the UK. ## Footnote The prevalence of uveitis in a population of donkeys in the UK evj 2020

Answer 37

Right answer : **b) A positive titre in aqueous humor for any leptospirosis serotype** The study showed that horses with a **positive titer in the aqueous humor** for any serotype of leptospirosis, particularly **L. bratislava**, were associated with a **worse prognosis** regarding their vision, particularly with blindness at presentation. ## Footnote Role of Leptospira spp. testing and ocular examination in horses with equine recurrent uveitis: A retrospective study of 63 horses eve 2022

Answer 38

Answer: B) IVGI showed limited effectiveness, with only a small proportion of horses achieving a positive outcome. A positive outcome was observed in **41% of eyes**, with **retinal degeneration** in 22% and **mature cataracts** in 15% of eyes. **Enucleations** were performed in **14/32 eyes**, due to lack of favourable response of IVGI, or due to complications, that is, glaucoma, corneal ulceration, and/or corneal mineralisation. ## Footnote Equine uveitis: Outcome and adverse effects after one or two intravitreal low-dose gentamicin injections evj 2024

Answer 39

**Being close to a pig farm** (OR 27.8) and a **recent history of flooding of the pasture** (OR 15.43) was associated with increased risk of uveitis. Impact on lepto exposition ? Being in the same owner's possession for a longer amount of time had a protective effect (OR 0.79). ## Footnote Risk factors for a first episode of primary uveitis in the UK and proportion of cases that experience recurrence following this first episode evj 2023

Answer 40

**about 20%** Recurrence was observed in 4/23 horses (18.2%). All first recurrent events occured **within the 12 months**. ## Footnote Risk factors for a first episode of primary uveitis in the UK and proportion of cases that experience recurrence following this first episode evj 2023

Answer 41

- Similar to findings for Appaloosas, **LP homozygotes** had higher odds of uveitis compared with true solid (N/N) horses (LP/LP OR= 7.64) and **age** was also identified as a risk factor. After accounting for LP, the **16–20 age group** had higher odds compared with the youngest group (OR= 13.36). - Bullet hole’ and ‘butterfly’ retinal lesions were not significantly associated with ERU-affected horses. This result is similar to findings in the Appaloosa. ‘Bullet-hole’ lesions have, in fact, been shown to be a result of **EHV-1** occurring between 3 weeks and 3 months post-infection likely due to **ischaemic injury** caused by viraemia. - There was no significant effect of PATN1 genotype. - Positive results for Leptospira exposure were not associated with higher odds of ERU in our sample. Our data support **genotyping for LP** to assess risk of ERU in Knabstruppers. Prevalence of **insidious uveitis** in this sample of Knabstruppers was **20.7%**. ## Footnote Risk factors for insidious uveitis in the Knabstrupper breed evj 2023

Answer 42

**ERU** was the most common aetiology (n = 10) followed by **trauma** (n = 8), like in USA ## Footnote Equine retinal detachment in the United Kingdom: 23 cases (2010–2020) eve 2023

Answer 43

**Cataracts**, **posterior synechiae** and **vitreal debris** were found commonly in both the ipsilateral and contralateral eye affected. ## Footnote Equine retinal detachment in the United Kingdom: 23 cases (2010–2020) eve 2023

Answer 44

It is possible to induce **mild reversible symptoms of colic** through **frequent administration of topical ocular atropine** in **normal** healthy horses. BUT the use of ocular atropine **at recommended dose rates for clinical ocular disease does not increase risk of colic.** ## Footnote Can ocular administration of atropine cause colic? eve 2020

Answer 45

All samples tested negative (below the limit of detection of the analytical method) for **dexamethasone one day** and for **prednisolone one week** after treatment cessation. Prefer **topical dexamethasone** to treat race horses ## Footnote Systemic detectability of dexamethasone and prednisolone after eye drop application in horses evj 2021

Answer 46

**Answer:** B) Dexamethasone and prednisolone reached effective concentrations in the **aqueous** humour but not in the vitreous humour. Potentially effective dexamethasone and prednisolone concentrations were measured in the **anterior chamber**, but **vitreal concentrations were negligible**. Therefore, treatment with only topically administered corticosteroids is deemed insufficient in horses in cases of **posterior uveitis**. ## Footnote Penetration of topically administered dexamethasone disodium phosphate and prednisolone acetate into the normal equine ocular fluids evj 2022

Answer 47

Exophthalmos may develop secondary to retrobulbar formation of **hydatid cysts** owing to **Echinococcus granulosus**. The **definitive host** for this tapeworm is the **dogs and foxes**. Horses, as well as humans, serve as an **intermediate host**. Dogs and other canids, as the definitive hosts, harbor the intestinal stage of the tapeworm, which produces infective eggs. The intermediate hosts and human are infected by ingesting the eggs in contaminated food or water. After oral ingestion of E granulosus eggs, cysts may develop in many anatomic sites, including the **liver**. Retrobulbar cyst formation may be detected via ultrasound imaging. However, definitive diagnosis is made by **histopathologic** identification of tissue taken after **enucleation**, which is often necessary for resolution of orbital disease.

Answer 48

Rapid globe retraction and resulting “flashing” third eyelid elevation are 2 well-recognized ocular signs of **tetanus** in the horse. Hyperesthesia is also a common finding.

Answer 49

**Hyperkalemic periodic paralysis (HYPP)** is an inherited myopathy of **QH, Paint, Appaloosas**, and QH crossbreds. It occurs as an **autosomal-dominant trait** in horses that are related to the Quarter Horse stallion *Impressive*. Clinical manifestations include myotonia, muscle fasciculations and weakness, and/or paralysis. Ocular signs of HYPP include **globe retraction** owing to spasm of the retractor bulbi muscle with **subsequent elevation of the third eyelid**, which may present as one of the early clinical signs of an episode. Episodes of HYPP can occur during periods of **increased serum potassium**, including after change in feed to high potassium diets such as alfalfa or electrolyte supplementation, or with stressors. DNA test available

Answer 50

Ocular abnormalities with peripheral vestibular disease include: - **ventral strabismus** of the globe on the affected side, which is often **positional** (noted with head elevation), - **horizontal nystagmus** with the fast phase away from the affected side.

Answer 51

Onchocerciasis is caused by ***Onchocerca cervicalis*** in the horse and commonly causes dermatitis as well as ocular changes, particularly in older horses. The matured worms in the nuchal ligament produce **microfilaria**, which can migrate and cause clinical disease. Migrating microfilaria have shown a preference for the **ventral midline** and **face** of the horse where they can be ingested by Culicoides spp. to help complete the cycle. Preferential microfilaria localization associated with the ocular tissues includes the **lower eyelid** and **lateral limbus of the eye**. **Depigmentation (vitiligo)** of the conjunctiva around the **temporal limbus** is a distinguishing clinical sign.

Answer 52

**Habronemiasis**, also known as **summer sores**, is caused by the nematodes Habronema muscae, H. microstoma, and Draschia megastoma. Ocular signs of habronemiasis include **nodule formation** at the site of the hypersensitivity reaction and appear as yellow, raised, caseous lesions (“sulfur granules”) most often at the **medial canthus**, but can also form in the conjunctiva and periocular region. The horse may develop **pruritis** associated with the nodules, which can progress to **fistulous tracts** in the medial canthus. In some cases, keratitis and corneal ulceration develop if the eyelids become irregular from nodular formation.

Answer 53

**Hereditary equine regional dermal asthenia (HERDA)** is a genetic condition, with an **autosomal-recessive** mode of inheritance, that has been recognized in QH, Paint and Appaloosa with QH lineage. The condition is likely present at birth; however, clinical signs are often not recognized until the horse begins preparation for riding. Ocular signs of HERDA include a **thinner cornea** and thus an increased risk of **corneal ulcers**, with an increased frequency of **corneal opacity**. DNA test available

Answer 54

**Metabolic encephalopathies** (**hepatic, uremic, intestinal**) are the most common cause of central blindness in horses. Less common causes of central blindness in horses include: - postictal change; - head trauma; - encephalitis owing to viral, protozoal, fungal (Aspergillosis spp. associated with guttural pouch mycosis), or bacterial infection; - **leukoencephalomalacia** (“moldy corn poisoning” owing to the **mold Fusarium moniliforme** and its mycotoxin **fumonisin**); - space-occupying masses such as tumors, abscesses, granulomas; - thiamine deficiency; - complications from anesthesia or inadvertent intracarotid injection.

Answer 55

**Silver coat color** is associated with **multiple congenital ocular anomalies (MCOA)**, autosomal dominant mutation with incomplete penetrance. Black horses with the silver mutation can range in phenotype from dark body with **light mane and tail** (A) to a light body known as light chocolate silver (B). Also note the **dappling** (B) that is present in some horses with the silver mutation. (D) Chestnut horses with the silver allele only appear chestnut because silver does not dilute red pigment. Therefore, **chestnut horses with or without the silver allele coat are phenotypically indistinguishable.** *Breeds affected* : Rocky Mountain horse, Kentucky mountain saddle horse, Kentucky mountain pleasure horse, **Icelandic horse**, **Shetland pony**, American miniature horse, **Comtois**, and other breeds with silver, including American quarter horse and Morgan.

Answer 56

**Silver coat color** is associated with **multiple congenital ocular anomalies (MCOA)**, autosomal **dominant** mutation with **incomplete penetrance**. DNA test available : silver test *Breeds affected* : Rocky Mountain horse, Kentucky mountain saddle horse, Kentucky mountain pleasure horse, **Icelandic horse**, **Shetland pony**, American miniature horse, **Comtois**, and other breeds with silver, including American quarter horse and Morgan. Horses **heterozygous** (Z/N) for the silver mutation most often have the cyst-only phenotype, whereas **homozygotes** (Z/Z) have multiple ocular defects. The **cysts phenotype** is characterized by **temporal cysts** that originate from the ciliary body or the peripheral retina. The **MCOA** phenotype is considered to be more severe and is characterized by **ciliary or peripheral retina cysts** with additional abnormalities, including iris hypoplasia, corneal globosa, megaloblepharon, retinal dysplasia, immature nuclear cataracts, and iridocorneal hypoplasia. Horses homozygous for the silver mutation (Z/Z) have **impaired vision** or are **blind**.

Answer 57

**Ocular SCC** can originate at the limbus, the nictitans, or the upper and lower eyelids. Haflingers are over-represented for limbal SCC, with prevalence estimated to be **35%** in this breed. An **autosomal recessive** mode of inheritance best explains the genetic risk for limbal SCC in the breed. Haflingers **homozygous for the T allele** had 5.89 times greater risk of developing limbal SCC than horses with T/C or C/C genotypes. DNA test available : ocular SCC The SCC genetic risk variant was also detected in 2 other closely related breeds with reported cases of ocular SCC, **the Belgian** and **the Percheron**, suggesting that it may also be an SCC risk factor in these breeds.

Answer 58

**Junctional epidermolysis bullosa (JEB)** is characterized by mechanical stress–induced lesion of the skin and mucosal membranes, in draft breeds and American Saddlebreds. This condition is a **recessive disorder** and carrier-to-carrier matings should be avoided. Mutations in laminin genes cause separation of the dermis and epidermis. Ocular manifestations : **corneal ulcers**

Answer 59

Friesian horses have several reported **inherited collagen disorders**, including megaesophagus, aortic rupture, dwarfism, and hydrocephalus, and these may be related to 2 corneal disorders in the breed. - **Corneal dystrophy** : characterized by **stromal loss** that is bilateral and has a higher occurrence in **males**, making an inherited X-linked recessive hypothesis likely. - **Districhiasis** : condition in which **cilia aberrantly emerge** from the meibomian gland openings, and, when pointing toward the cornea, these can cause corneal irritation or ulceration. No DNA test available

Answer 60

Perform a complete ophthalmic examination, including tonometry to measure IOP. Use a consistent protocol with the horse's head above heart level, and consider an auriculopalpebral nerve block (conflicting results). Compare IOP between both eyes, as normal equine IOP ranges from 15-30 mmHg. An IOP >32-35 mmHg in the affected eye, along with the clinical signs and history, would be diagnostic for glaucoma. ## Footnote Vet clinic Equine glaucoma

Answer 61

The initial medical management should include a combination of the **topical β-blocker 0.5% timolol and the topical carbonic anhydrase inhibitor 2% dorzolamide, used every 8 to 12 hours.** This **combination is more effective** than when the two drugs are administered alone. Additionally, treat the **underlying uveitis with appropriate anti-inflammatory medications**. ## Footnote Vet clinic Equine glaucoma

Answer 62

For a **blind, painful eye with glaucoma** that is unresponsive to medical management, **end-stage** procedures should be considered. 1. Pharmacologic ciliary body ablation using intravitreal injection of gentamicin and dexamethasone 2. **Enucleation** (surgical removal of the eye) 3. Evisceration with placement of an intrascleral prosthesis for a more cosmetic outcome The choice depends on factors such as the horse's overall health, owner preferences, and potential complications associated with each procedure. ## Footnote Vet clinic Equine glaucoma

Answer 63

* **Auriculopalpebral** nerve block – **motor** block of **facial** nerve (**VII**) – eyelid akinesia * **Supraorbital** nerve block – sensory nerve block of frontal nerve (**V**) * **Lacrimal** nerve block – **sensory** nerve block of lacrimal nerve (**V**) * **Infratrochlear** nerve block – **sensory** nerve block of infratrochlear nerve (**V**) * **Zygomatic** nerve block – **sensory** nerve block of zygomatic nerve (**V**) * **Retrobulbar** nerve block – **sensory** (ophthalmic nerve **V**) and **motor** nerve **(III, IV and VI**) block – globe akinesia and central eye position

Answer 64

30 mm in 30 sec or 35 mm in < 1min

Answer 65

The correct answer is C) The EOPS showed **good reliability and was able to accurately distinguish between healthy horses and those with ocular pathology**. Most items in the **behavioral and ocular expression categories showed excellent inter- and intra-observer reliability** (ICC ≥ 0.75) At the optimal **cut-off score of ≥7, the EOPS demonstrated high sensitivity (81.3%) and specificity (100.0%) in identifying horses with ocular pathology** Overall behaviour, ear movements, position inside the box à lowest reliability Improved after exclusion of physiological parameters (HR, RR, T) ## Footnote 2021 Development and preliminary validation of a pain scale for ophthalmic pain

Answer 66

true Acetaminophen administered orally to healthy horses at 20 mg/kg every 12 h for six doses readily penetrates the normal equine eye, with a higher aqueous humour:serum ratio than flunixin and firocoxib as measured 1 h after the last dose. Further studies are required to determine if acetaminophen represents a viable addition or alternative to traditional NSAIDs in the treatment of equine ocular pain and inflammation, and if so, the mechanism by which this occurs. mean ± SD aqueous humour:serum acetaminophen concentration ratio was found to be substantially higher than previously studied oral NSAIDs, flunixin meglumine, and firocoxib (44.9 ± 15.9% compared to 3.59 ± 3.32% and 11.99 ± 4.62%, respectively)

Answer 67

**differentiation between retinal and central blindness** retinal **function** is desired but the retina cannot be viewed, such as before **cataract** surgery **Suspected congenital stationary night blindness,** **hyphema** owing to trauma, **chorioretinal** lesions (owing to equine recurrent uveitis or other causes), **glaucoma** are some of the common indications for ERG in equine patients. **normal ERG can be recorded from a blind animal if the blindness has originated from lesions in deeper retinal layers, the optic nerve, or the brain**

Answer 68

However, the greater the extent of the lesion (active or scar), the more likely it is to cause visual impairment. In addition, lesions in the retinal area centralis may lead to greater effect on vision than peripheral lesions. Moreover, retinal lesions that affect only the outer retina may have a lesser effect on vision compared with deeper lesions that affect the inner retina and the nerve fiber layer, because the nerve fiber layer carries visual input from photoreceptors in other areas of the retina. The

Answer 69

The exact etiology of these lesions is unknown; however, choroidal vasculitis, infarction, and ischemia have been proposed. An infection with equine herpesvirus 1 in utero has also been suggested as a possible etiology. A recent study has shown that even extensive bullet hole lesions occupying most of the nontapetal fundus (>“150 bullet holes”) did not affect retinal function, as measured by fERG, and the reported horses did not seem to have visual deficits

Answer 70

Any cause of uveitis with peripapillary involvement can lead to this type of lesion, and it is not pathognomonic to equine recurrent uveitis