Ophthalmology Flashcards
Pain scoring systems in hospitalized horses with ocular disease
Horses Discharged After Medical Treatment:
• Higher admission pain scores (HGS and BPS) compared to horses that later underwent enucleation.
• Pain scores decreased over time, indicating effective pain control and clinical improvement.
Horses Undergoing Enucleation:
• Showed increasing pain scores (HGS and BPS) during hospitalization.
• Temporal trends in pain scores were significantly associated with enucleation as the final outcome (P < 0.05).
Horses Undergoing Ophthalmic Surgery:
• Pain scores at admission and during hospitalization did not differ significantly from horses discharged after medical management.
• Surgical decisions often depended on lesion type and severity rather than pain progression.
Pain Score Correlations
• Moderate correlation between HGS and BPS scores (r² = 0.73), supporting their complementary use.
• Temporal increases in both scores were linked to worse clinical outcomes, such as enucleation.
Impact of NSAIDs and Analgesics
• Horses treated with NSAIDs (flunixin meglumine, firocoxib) and adjunctive analgesics (gabapentin, butorphanol) generally experienced reduced pain scores over time.
• Pain relief effectiveness varied based on the severity and type of ocular disease.
Utility of Pain Scales
• HGS and BPS are reliable tools for monitoring ocular pain in hospitalized horses:
• Facilitate real-time assessment of treatment response.
• Help predict clinical progression and the need for surgical intervention.
Management Decisions
• High pain scores at admission warrant aggressive medical management, potentially avoiding surgical interventions.
• Rising pain scores during hospitalization indicate poor prognosis for medical therapy and support decisions for enucleation.
• Admission pain scores alone were insufficient to predict clinical outcomes.
• Monitoring pain trends over time is more informative for guiding treatment plans.
Equine uveitis: Outcome and adverse effects after one or two intravitreal low-dose gentamicin injections
• 41% of eyes (13/32) achieved a positive outcome after one or two IVGIs:
• Uveitis controlled with minimal or no anti-inflammatory medication.
• A second IVGI improved outcomes for some cases:
-ERU: 24% positive outcome after one injection; improved to 67% after the second injection.
-HIK: 36% positive outcome after one injection; no response to the second injection.
Limitations in Treatment:
• Nearly half (14/32, 44%) of eyes required enucleation due to:
-Persistent inflammation.
-Complications such as glaucoma, corneal ulceration, or mineralisation.
• Success rates lower than earlier studies (88–94%), possibly due to:
-Predominantly anterior uveitis cases (91%).
-Late-stage disease in many horses.
Adverse Effects
Short-Term Complications:
• Peri-injection complications occurred in 16% (5/32) of eyes:
• Mild ocular discomfort.
• Periocular swelling and epiphora (resolved within a week).
• Rare events: generalized urticaria, ventromedial strabismus (resolved in <2 months).
Long-Term Complications:
• Retinal degeneration: Observed in 22% (7/32), often within 2–8 weeks post-IVGI.
• Cataract formation: Mature cataracts developed in 16% (5/32), mostly within 6–12 months.
• Corneal mineralisation: Detected in 38% (12/32), likely exacerbated by corticosteroid use or persistent inflammation.
• Corneal ulceration: Reported in 41% (13/32), often associated with topical corticosteroid therapy.
Effect of Leptospirosis
• Only 7/29 horses were tested for leptospirosis; one was positive (L. Grippotyphosa) but did not respond to treatment.
• Leptospiral involvement was not a prominent factor in this cohort, contrasting with studies from regions with higher leptospirosis prevalence.
Clinical Implications
• IVGI may be effective for specific uveitis cases, especially in eyes with chronic ERU:
• A second injection may improve outcomes in ERU cases.
• IVGI was less effective for anterior uveitis, possibly due to the site of inflammation being less accessible to intravitreal drugs.
Indications for IVGI
• IVGI is suitable for selected cases of chronic uveitis, particularly when:
-Medical management is insufficient.
-Uveitis involves the posterior segment.
-Early-stage disease and posterior uveitis may respond better than late-stage anterior uveitis.
Noninvasive diode laser–an effective and safe treatment of iris cysts in 46 eyes of 35 horses
- 93% response rate, 78% good and 15% moderate
- complications included: corneal scarring, retinal burns, corneal defects and laser induced uveitis (17% eyes)
- polycystic, hypreplastic corpora nigra and thick walled cysts less likely to respond
Transcorneal aspiration formanagement of primary iris cysts in the standing horse
-100% improvement (61% resolution)
- no long term complications (short term uveitis and fibrin)
- adequate sedation, blocking and temprement
Effects of intravenous romifidine, detomidine, detomidine combined with butorphanol, and xylazine on tear production in horses
- Romifidine- no effect
- xylazine- increased
- detomidine- decreased
- detomidine + butorphanol- lowest annd most prolonged
- none <15mm
Dorsally placed commercially available subpalpebral lavage systems have low complication rates in horses
• Overall Complication Rate: 29.1% (37/127 SPLs).
• Ocular Complications: 21.2% (27/127).
-Secondary corneal ulcers: 7.1%.
-SPL removal by horses: 6.3%.
-Eyelid cellulitis or abscessation: 5.5%.
•Nonocular Complications: 7.9% (10/127).
-Suture replacements: 3.1%.
-Catheter replacements: 2.4%.
-Tube tangling or stretching: 2.2%.
• Risk Factors: No Significant Associations:
• SPLs managed at home had higher (but not statistically significant) complication rates (42.3%) compared to hospital-managed SPLs (23.7%).
• Earlier reports (1997) showed higher complication rates (66%) for dorsally placed SPLs, attributed to:
-Practitioner-modified systems with irregular designs.
-Increased tissue irritation and mechanical instability.
-This study’s findings underscore the benefits of commercially available kits, which feature standardized materials and improved designs.
Evaluation of transpalpebral ultrasonographic measurement of optic nerve sheath diameter for indirect assessment of intracranial pressure in anesthetized and standing healthy adult horses
• Weak to moderate associations between ICP and ONSD were found in anesthetized horses, depending on head position:
• Lowered head position: Moderate association (R² = 63–78%).
• Elevated head position: Weak association (R² = 46–63%).
• Neutral position: No significant association.
• In standing horses, there was no significant association between ONSD and ICP (R² = 5–12%).
• Measurements were consistent across observers (intra-observer coefficient of variation ≤10%).
• ONSD increased slightly in the elevated anesthetized position compared to neutral but decreased inconsistently in other positions.
• Findings indicate that transpalpebral ONSD measurements are unlikely to be clinically useful for ICP monitoring in horses:
Can ocular administration of atropine cause colic?
• It is possible to induce mild reversible symptoms of colic through frequent administration of topical ocular atropine in normal healthy horses.
• Systemic bioavailabilty is potentially both high and rapid, even if individual horses vary naturally.
• Lower overall doses, conjunctival overflow losses, variation in pharmacokinetics and the presence of more potent risk factors probably explain why no retrospective clinical studies demonstrate an association between ocular atropine and colic in horses with ocular disease.
• Therefore, the use of ocular atropine at recommended dose rates for clinical ocular disease does not increase risk of colic.
Role of Leptospira spp. testing and ocular examination in horses with equine recurrent uveitis
• Leptospira infection significantly associated with ocular disease severity and visual prognosis:
• Aqueous humour titres correlated with:
-Vision loss at presentation (P = 0.04).
-Blindness, particularly with L. bratislava (P = 0.002).
-Serum titres linked to posterior segment disease (P = 0.01).
• Horses with positive aqueous humour PCR were younger (mean age: 9.25 years) compared to PCR-negative horses (mean age: 13.3 years, P = 0.01).
• The Goldmann-Witmer coefficient (C value) was positive (≥4) in 52.38% of eyes tested, indicating intraocular leptospiral antibody production.
• Most frequent serovars associated with positive C values:
-L. grippotyphosa (81.82% of cases).
-L. pomona (68.18% of cases).
-L. bratislava and L. hardjo were associated with worse visual outcomes, indicating their potential role in severe ERU cases.
Vision prognosis varied by serovar:
• L. bratislava: Highly correlated with blindness.
• L. grippotyphosa and L. hardjo: Associated with decreased vision at presentation.
• Serum titres were often positive for the same serovars as aqueous humour titres, supporting systemic infection prior to intraocular invasion.
Horses with leptospiral-positive ERU should be treated aggressively to prevent further visual deterioration:
• Antibiotics (e.g., doxycycline, minocycline) for systemic leptospiral infections.
• Immunosuppressive therapy (e.g., corticosteroids) to control immune-mediated damage.
• Advanced options, such as pars plana vitrectomy (PPV), may reduce recurrent uveitis in horses with intraocular leptospiral titres.
• Breeds and Risk Factors Although no significant breed predisposition was observed, previous studies suggest breeds like Appaloosas and Hanoverians may be overrepresented in ERU cases.
• Horses living in wet climates or with access to wildlife are at higher risk for leptospiral exposure, warranting regular testing in endemic regions.
• Findings align with prior studies linking L. grippotyphosa and L. pomona to ERU.
• Novel association with L. bratislava highlights the evolving understanding of serovar-specific roles in ERU pathogenesis.
Equine retinal detachment in the United Kingdom: 23 cases (2010-2020)
Causes of Retinal Detachment
•Equine Recurrent Uveitis (ERU):
-Most common cause, present in 43.5% of cases.
-Typically associated with chronic intraocular inflammation, posterior synechiae, and vitreal traction bands.
• Trauma:
-Responsible for 34.8% of cases, highlighting blunt or penetrating injuries as significant contributors.
• Other Causes:
-Post-surgical complications (13.0%).
-Congenital anomalies (4.3%).
-Primary glaucoma (4.3%).
Diagnostic Techniques
• Ultrasound: Confirmed RD in all 23/23 cases (100%). Provided a reliable diagnostic modality in cases where fundus visualization was obscured by cataracts, hyphaema, or corneal oedema.
• Ophthalmoscopy: Detected RD in only 9/23 cases (39.2%). Limited by concurrent anterior chamber and vitreal abnormalities.
Clinical Signs:
• Loss of menace response, dazzle reflex, or pupillary light reflex (PLR) in 63.7% of cases.
• Partial detachment cases retained weak PLR or menace response, consistent with residual vision.
Concurrent Ocular Pathology- Common findings included:
• Ipsilateral Cataracts: Present in 52.4% of cases.
• Posterior Synechiae: 38.1%.
• Vitreal Debris: 19.0%.
• Other abnormalities: lens subluxation, corneal oedema, or hyphaema in fewer cases.
Unilateral vs Bilateral Cases
• Unilateral RD in 91.3% of cases.
• Bilateral RD in 8.7%, primarily due to ERU or congenital defects.
Penetration of topically administered dexamethasone disodium phosphate and prednisolone acetate into the normal equine ocular fluids
Drug Penetration
• Aqueous Humour:
-Mean DEX concentration: 32.4 ng/mL (range: 15.7–58.3 ng/mL).
-Mean PRED concentration: 321.6 ng/mL (range: 119.0–605.3 ng/mL).
-PRED concentrations were approximately 10 times higher than DEX.
• Vitreous Humour:
-Neither DEX nor PRED was detectable in any samples (LOD: 2.5 ng/mL).
• Serum:
-Both corticosteroids were below the detection limit (LOD: 5 ng/mL), indicating minimal systemic absorption.
• Steady-State Achievement- Both corticosteroids reached steady-state concentrations in the aqueous humour after 24 hours of dosing every 2 hours.
• Concentrations plateaued up to 180 minutes post-administration, suggesting that frequent dosing intervals may not be necessary.
Clinical Implications
• Anterior Uveitis: Effective concentrations were achieved in the aqueous humour for both DEX and PRED, supporting their use for anterior segment inflammation.
• Posterior Uveitis: Lack of detectable levels in the vitreous humour indicates that topical administration is insufficient for posterior segment inflammation.
-Alternative administration routes (e.g., systemic, subconjunctival, or intravitreal injections) may be necessary.
• Formulation Considerations
-PRED’s lipid-soluble nature allows better penetration through the lipid-rich corneal epithelium compared to the water-soluble DEX formulation.
-However, DEX is seven times more potent than PRED, suggesting that dose differences should be considered when selecting a corticosteroid.
Clinical Recommendations
• PRED may be preferred for its higher aqueous humour concentrations, especially in severe anterior uveitis cases.
• DEX remains a valid choice due to its potency and water solubility, which may reduce ocular discomfort compared to PRED suspensions.
Artificial intelligence as a tool to aid in the differentiation of equine ophthalmic diseases with an emphasis on equine uveitis
Validation results for image classification:
Three-class model (uveitis, other diseases, healthy):
• Training accuracy: 99.82%.
• Validation accuracy: 96.66%.
• High accuracy indicates the CNN effectively identifies uveitis-related changes and differentiates healthy eyes from those with disease.
• The AI primarily focused on dorsal eye structures, particularly the transition between the pupil, iris, and sclera.
• While effective for identifying anterior segment changes (e.g., corneal opacities, miosis, fibrin deposits), the tool was limited in detecting posterior segment abnormalities (e.g., retinal detachment).
• The Equine A-Eye app allows veterinarians and horse owners to capture and analyze images in real-time.
Key features:
-Heatmap overlays highlight areas of diagnostic interest.
-Immediate feedback with probabilities for each diagnostic category.
-Limitations of the Tool: AI relied on the pupil size as a visual cue, potentially creating a bias: Diseased eyes often had dilated pupils due to prior mydriatic administration. This was mitigated by including a diverse dataset with medicated and non-medicated eyes.
- The tool does not assess posterior segment diseases unless visible through the pupil, limiting its scope for retinal or optic nerve pathologies.
Possible use in triage.
Comparison of four tonometers in the measurement of intraocular pressure in healthy horses
• Rebound Tonometers (Tonovet and Tonovet Plus):
-Provided IOP values closest to manometry in sedated horses: Tonovet: 25.7 ± 5.8 mmHg. Tonovet Plus: 24.8 ± 7.1 mmHg.
-Slight overestimation of IOP, particularly at values >25 mmHg.
• Applanation Tonometers (Tono-Pen AVIA Vet and Kowa HA-2):
-Consistently underestimated IOP compared to manometry:
• Tono-Pen AVIA Vet: 19.2 ± 4.7 mmHg.
• Kowa HA-2: 24.1 ± 1.2 mmHg.
• Kowa HA-2 had the least variability and was most consistent across measurements.
Field Study (Unsedated Horses)
• All tonometers showed higher variability in IOP measurements in unsedated horses:
• Tonovet and Tonovet Plus recorded higher IOP values (30.7 ± 5.6 and 29.6 ± 6.7 mmHg, respectively) compared to Tono-Pen AVIA Vet (27.3 ± 5.8 mmHg) and Kowa HA-2 (23.4 ± 2.2 mmHg).
• Tonovet and Tonovet Plus were easy to use and did not require topical anaesthesia, making them more practical for routine field evaluations.
Bias in Tonometer Readings
• Overestimation: Rebound tonometers (Tonovet and Tonovet Plus) overestimated IOP at higher pressures (>25 mmHg).
• Underestimation: Applanation tonometers (Tono-Pen AVIA Vet and Kowa HA-2) tended to underestimate IOP, particularly at higher values.
Clinical Implications
• Rebound Tonometers: Most suitable for routine clinical use due to ease of operation and lack of need for topical anaesthesia. Tonovet Plus provided slightly more consistent results than Tonovet.
• Applanation Tonometers: Kowa HA-2 exhibited excellent repeatability but required technical expertise and fluorescein dye, limiting its practicality in field settings.
• Tono-Pen AVIA Vet had the largest underestimation bias, reducing its reliability for IOP measurements.
Ultrasound biomicroscopy of the equine iridocorneal angle
UBM effectively imaged ICA structures in all 30 horses, demonstrating:
• Pectinate ligament trabeculae.
• Corneoscleral, uveal, and supraciliary trabecular meshworks.
• Associated structures, including the anterior chamber, iris, and cornea.
• Morphology of the ICA showed minimal variability across horses, suggesting a consistent ultrasonographic appearance in normal eyes.
UBM can assess ICA morphology in vivo, allowing for early detection of:
• Aqueous humour outflow obstructions.
• Structural changes associated with glaucoma (e.g., ciliary cleft collapse).
• Particularly valuable for evaluating horses with:
-Elevated intraocular pressure (IOP).
-Recurrent or chronic uveitis.
-Corneal oedema or other anterior segment abnormalities.
• Traditional assessment of the ICA is limited to gonioscopy, which provides a segmental and anterior-only view.
• UBM offers a high-resolution, full-depth visualization of ICA structures, including posterior segments not visible with gonioscopy.
• UBM has the potential to identify early morphological changes in glaucoma-prone horses, enabling: Early interventions to preserve vision. Better understanding of structural abnormalities that predispose to ocular hypertension.
Risk factors for a first episode of primary uveitis in the UK and proportion of cases that experience recurrence following this first episode
Risk Factors for Primary Uveitis
• Proximity to Pig Farms: Horses near pig farms had significantly increased odds of developing primary uveitis (OR: 27.8, 95% CI: 1.31–592.06; P = 0.03).
• Flooding of Turnout Fields: A history of recent flooding increased the risk of uveitis (OR: 15.44, 95% CI: 2.80–84.98; P = 0.002).
• Duration of Ownership: Longer ownership duration had a protective effect (OR: 0.79, 95% CI: 0.68–0.93; P = 0.004).
• Recurrence Rate: 18.2% (4/22 horses) experienced recurrence, defined as new episodes of uveitis ≥6 weeks after the initial episode.
• First recurrences occurred within 3 months for three horses and within 12 months for all four cases.
• Five horses (22.7%) required surgical interventions for non-resolving initial episodes: Three underwent enucleation. One had a pars plana vitrectomy. One received a cyclosporine implant.
• Flood-prone pastures and proximity to pig farms may facilitate exposure to Leptospira spp., a known cause of equine uveitis. However, this study did not confirm leptospiral infection in affected horses, and the role of Leptospira spp. in UK cases remains modest.
• Owner Influence: Longer ownership may reflect a stable environment or the absence of risk exposures, though causality is unclear.
Prognosis and Recurrence
• Approximately 59% of cases resolved without recurrence, suggesting favorable outcomes for most horses with appropriate initial treatment.
• The first 3 months post-diagnosis are critical for recurrence monitoring, warranting prolonged anti-inflammatory therapy.
• Severe Cases- Horses with persistent uveitis unresponsive to medical therapy may require surgical interventions (e.g., enucleation, cyclosporine implants) to preserve quality of life.
• Unlike continental studies, Leptospira kirschneri serovar Grippotyphosa, often implicated in Europe, is less prevalent in the UK, highlighting geographic variation in uveitis aetiology.
