The eye is situated within the orbit of the skull, cushioned in fat and connective tissue and protected by the eyelids, the conjunctiva lines, the inner eyelids and the anterior surface of the sclera (Aspinall and Lakeman, 2016). The conjunctival mucous secretions contribute to the protection of the cornea.
Conjunctivitis refers to inflammation of the conjunctiva and is very common in cats due to a variety of reasons. Primary infectious conjunctivitis is one of the most common presentations of the condition, though secondary causes are possible. Clinical signs of conjunctivitis are usually non-specific but often include hyperemia, ocular discharge, chemosis, conjunctival thickening or ulceration, conjunctival haemorrhage and follicle formation. When approaching feline conjunctivitis, the following classifications can be utilised to encourage a thorough examination:
- Duration (acute or chronic)
- Appearance (mucoid, mucopurulent, purulent, follicular, haemorrhagic)
- Cause (infectious, traumatic, secondary).
Diagnosis
In many cases of feline conjunctivitis, it is difficult to distinguish underlying causes and laboratory diagnostics may be necessary. However, a full clinical history should be taken alongside an ophthalmic and clinical examination. Registered veterinary nurses may be used in these cases to assist with history taking, creating nursing care plans and aiding clinical examination. Nursing care plans are highly recommended throughout the veterinary literature and can be easy adaptable for ophthalmic patients, especially those that may require hospital or surgical admission. Nursing care plans allow registered veterinary nurses to record and assess the patients' normal behaviours and routines to allow for patient-focused care, based on the information provided by the owner.
Upon presentation, the following should be discussed with the owner and can be recorded on an ophthalmic nursing care plan/patient questionnaire (Table 1):
- Onset and duration of clinical signs
- Presence and type of ocular discharge (especially if the owner has been cleaning ocular discharge at home)
- Changes in vision (and any associated behaviour changes)
- Presence of pain, pruritus or patient interference
- Known concurrent systemic and ocular diseases
- Current age and vaccination status
- Observation of and incidence of trauma.
Table 1.
Example of an ophthalmic nursing care plan and questionnaire
| Patient history: | |
|---|---|
| Onset and duration of clinical signs? | |
| Presence and type of ocular discharge? | |
| Changes in vision? | |
| Presence of pain, pruritus or patient interference (pain score)? | |
| Known concurrent systemic and ocular diseases? | |
| Age and vaccination status? | |
| Observation/incidence of trauma? | |
| Activity of living (AOL) | Current routine | Actual problem |
|---|---|---|
| 1. Eat adequate amounts (type of food/bowl? Allergies?) | ||
| 2. Drink adequate amounts (bowl type?) | ||
| 3. Urinate normally (substrate/litter?) | ||
| 4. Defaecate normally | ||
| 5. Breath normally (coughs/sneezing?) | ||
| 6. Maintain body temperature (indoor/outdoor?) | ||
| 7. Groom self (do they get groomed?) | ||
| 8. Mobility (normal exercise routine) | ||
| 9. Sleep/rest (where do they sleep?) | ||
| 10. Express normal behaviour (has vision affected behaviour?) |
| Pre-operative checks/readings |
|---|
| T: P: R: |
| Heart murmur? Y / N Grade: |
| ASA: 1 2 3 4 5 E |
| Intraocular pressure: L: mmHg R: mmHg |
| Schirmer tear test: L: mm/min R: mm/min |
Any changes in behaviour and associated stress should be discussed with the owner. Managing stress in all ophthalmic patients is paramount, as a raise in blood pressure (BP) can increase intraocular pressure (IOP); rendering BP and IOP results unreliable, which may be essential for diagnosing an underlying condition. Prior to the consultation and clinical examination, cats should avoid waiting in reception areas; if this is unavoidable then cat-specific waiting rooms and ‘cat-parking’ is highly recommended. The ISFM recommends examining cats while remaining in the bottom of the carrier and using a towel to lightly swaddle and help reduce stress; the towel technique can be extremely useful for ophthalmic examination (Rodan et al, 2011).
Notably, ophthalmic pain is often overlooked by both veterinary professionals and pet owners; the assessment of feline ocular pain can be difficult (Knott, 2020). Common signs of ophthalmic pain include changes in demeanor, patient interference, head pressing and ocular signs such as blepharospasm and epiphora. Pain scoring can be utilised in ophthalmic patients; however, it is recommended that they are modified as the signs can be subtle (Table 2; Knott, 2020).
Table 2.
Modified ophthalmic Glasgow feline composite measure pain scale
| Patient Name: | Date: | Procedure: | |||
|---|---|---|---|---|---|
| Choose the most appropriate expression from each section and total the scores to calculate the pain score for the cat. If more than one expression applies choose the higher score | |||||
| Time: | |||||
| Initials: | |||||
| Look at the cat in its kennel: Is it…? | |||||
| Question 1: | |||||
| Silent/purring/meowing | 0 | 0 | 0 | 0 | 0 |
| Crying/growling/groaning | 1 | 1 | 1 | 1 | 1 |
| Question 2: | |||||
| Relaxed | 0 | 0 | 0 | 0 | 0 |
| Licking lips | 1 | 1 | 1 | 1 | 1 |
| Restless/cowering at back of cage | 3 | 3 | 3 | 3 | 3 |
| Tense/crouched | 3 | 3 | 3 | 3 | 3 |
| Rigid/hunched | 4 | 4 | 4 | 4 | 4 |
| Question 3: | |||||
| Ignoring any wound or painful area | 0 | 0 | 0 | 0 | 0 |
| Attention to wound | 1 | 1 | 1 | 1 | 1 |
| Question 4: | |||||
| Circle the drawing which best depicts the cats' ear position | |||||
| Circle the drawing which best depicts the cats' muzzle position | |||||
| Approach the cage, call the cat by name & stroke along its back from head to tail, does it/is it…? | |||||
| Question 5: | |||||
| Respond to stroking | 0 | 0 | 0 | 0 | 0 |
| Unresponsive | 1 | 1 | 1 | 1 | 1 |
| Aggressive | 2 | 2 | 2 | 2 | 2 |
| Apply gentle pressure 5cm around wound or painful area (In the absence of painful area apply similar pressure around hind leg above the knee). Does the cat…? | |||||
| Question 6: | |||||
| Do nothing | 0 | 0 | 0 | 0 | 0 |
| Swish tail/flatten ears | 1 | 1 | 1 | 1 | 1 |
| Cry/hiss | 2 | 2 | 2 | 2 | 2 |
| Growl | 3 | 3 | 3 | 3 | 3 |
| Bite/Lash out | 4 | 4 | 4 | 4 | 4 |
| General impression is the cat is…? | |||||
| Question 7: | |||||
| Happy and content | 0 | 0 | 0 | 0 | 0 |
| Disinterested/quiet | 1 | 1 | 1 | 1 | 1 |
| Anxious/fearful | 2 | 2 | 2 | 2 | 2 |
| Dull | 3 | 3 | 3 | 3 | 3 |
| Depressed/grumpy | 4 | 4 | 4 | 4 | 4 |
| Look at the affected eye(s): what is the cat displaying? | |||||
| Question 8: | |||||
| Nothing/Eyes open without discomfort | 0 | 0 | 0 | 0 | 0 |
| Excessive blinking | 1 | 1 | 1 | 1 | 1 |
| Blepharospasm | 2 | 2 | 2 | 2 | 2 |
| Attempting to rub the eye(s) | 3 | 3 | 3 | 3 | 3 |
| Blepharospasm, lacrimation and rubbing of the eye(s) | 4 | 4 | 4 | 4 | 4 |
| Total score (Out of 24) | |||||
| Analgesia given? Consider rescue if score >5 or if any question has maximum score | |||||
Aetiologies
Infectious conjunctivitis
Primary infectious conjunctivitis is one of the most common aetiologies. Feline herpesvirus-1 (FHV-1) and Chlamydia felis (C. felis) are highly prevalent in the feline population (Wieliczko and Płoneczka-Janeczko, 2010; Stiles, 2013). Other infectious causes such as Mycoplasma felis (M. felis) and calicivirus are less common but should be considered (Turner, 2007). Feline conjunctivitis causes can be difficult to differentiate based on appearance.
FHV-1 infection is internationally recognised in the domestic cat population and is a major cause of feline morbidity (Gould, 2011). FHV-1 invades and replicates in the epithelia of the conjunctiva and respiratory tract; following exposure to the virus, most cats will become persistently infected and many will develop reoccurring ocular and respiratory signs in their lifetime (Andrew, 2001; Gould, 2011). Acute ocular herpetic disease can result in progressive corneal pathology, such as corneal ulceration, keratitis and corneal scarring, which can be extremely painful and may be blinding for some affected cats (Gould, 2011; Stiles, 2013). Additionally, FHV-1 infection can present with symblepharon; an adhesion between the palpebral conjunctiva, cornea and third eyelid (Kim et al, 2021). Symblepharon can cause obstruction of the lacrimal punctae, resulting in pain and epiphora (Hartley, 2013).
Diagnosis and treatment of ocular manifestations of primary FHV-1 infection can be difficult and FHV-1 can predispose patients towards secondary bacterial infections. FHV-1 can be confirmed by virus isolation, though false negative results are possible, especially in chronic recurrent cases (Dechra, 2022); diagnosis is usually identified by clinical signs and response to treatment.
Although less common and more severe in young patients, other viral causes such as calicivirus should also be considered. Calicivirus can be diagnosed by virus isolation and clinical signs such as upper respiratory tract infection and oral ulceration. Treatment of FHV-1 and calicivirus are relatively similar as treatment is often symptomatic; however, herpes-specific anti-viral medications such as ganciclovir and famciclovir are available.
For both viral causes, topical lubricants (e.g. hyaluronate), should be considered to support the cornea and conjunctiva, while antibiotics should only be used for secondary bacterial infection or for associated corneal ulceration. Antiviral medications are available but may be expensive, and good owner and patient compliance is required, as application is often frequent. Owner education from the point of diagnosis is vital, as over 80% of FHV-1 infected cats will become carriers and re-occurrence is possible.
Bacterial causes such as C. felis and M. felis, although less common, should also be considered, as these may present identically to FHV-1. Both can be diagnosed by bacterial PCR or culture; however, it is important to note that around 90% of healthy cats will harbor M. felis without disease. Culture and sensitivity testing is available, although not widely used, and may help the veterinary surgeon select a suitable choice of antibiotic (Dechra, 2022).
Secondary causes
A thorough ophthalmic examination should be performed, as a more serious underlying ophthalmic condition may also present with the red eye appearance. Registered veterinary nurses are able to assist by performing a number of routine tests including (Table 3):
- Menace response
- Maze tests
- Cotton wool/tracking test
- Schirmer tear testing
- And measurement of IOP.
Table 3.
Common ophthalmic tests
| Menace response | The menace response test is performed by making a ‘menacing’ gesture with the hand towards the patient's eye. Blink is a positive indication of functioning central and peripheral ophthalmic systems (take care to not touch the patient because of excessive air movement which could induce a false-positive result) |
| Maze tests | An obstacle course to assess vision in daylight and dim conditions, obstacles should be adjusted to avoid memorisation and mapping. |
| Cotton wool test | Cotton balls tossed into the visual field to assess the patient's visual placing response. |
| Schirmer tear test | The measurement of test tear production for the diagnosis of keratoconjunctivitis sicca, normal tear production is between 15–25 mm/min. |
| Tonometry | The measurement of intraocular pressure for the diagnosis of glaucoma, normal intraocular pressure is between 15–25 mmHg. |
Schirmer tear testing and tonometry should ideally be performed for all ophthalmic patients to rule out underlying ophthalmic disease. Although more common in dogs, an underlying tear film issue, such as keratoconjunctivitis sicca (KCS) where the tear production is below the normal range of 15–25 mm/min, may result in similar clinical signs to conjunctivitis. Schirmer tear testing in cats can be variable and can decrease with stress; therefore, the results should be interpreted with the whole clinical picture in mind. Tonometry can help aid the diagnosis of glaucoma alongside clinical examination and patient history; both conjunctivitis and glaucoma can lead to a ‘red eye’ appearance. It is important to be able to distinguish between superficial conjunctival and episcleral vessels; conjunctival hyperaemia may indicate conjunctivitis or keratitis, where-as episcleral congestion is more indicative of an underlying intraocular disease. Topical 2.5% phenylephrine may be applied to differentiate between conjunctival and episcleral vessels; conjunctival vessels will blanch rapidly, whereas episcleral vessels will blanch slower (Dechra, 2022). Additionally if phenylephrine is not available, conjunctival vessels appear more mobile than the deep episcleral vessels.
Conjunctivitis-like symptoms may be as a result of adnexal abnormalities, such as brachycephalic conformation, entropion, ectropion or distichiasis. Brachycephalic breeds such as Exotic Shorthairs, Persians and Himalayans are becoming increasingly popular and frequently present with ocular disease due to selective breeding. Brachycephalic ocular syndrome is a disease of short-skulled breeds, where the anatomical differences of the shape and positioning of the eyes lead to ocular problems (Maggs et al, 2008). Brachycephalic ocular syndrome is characterised by one or a combination of the following issues (Plummer, 2015):
- Exophthalmos (protrusion of the eyes)
- Macroblepharon (abnormal eyelid opening when compared to eye size) and/or
- Lagophthalmos (inability to close the eyes).
The combination of such characteristics often results in conjunctivitis and/or frequent corneal ulceration; often surgical and long-term medical management is required. Other secondary causes that should be ruled out include: symblepharon, obstruction of the nasolacrimal duct and neoplasia, such as squamous cell carcinoma and lymphoma.
Other causes
Although rare, other causes such as feline eosinophilic keratitis (FEK) and lipogranulomatous conjunctivitis may present. Allergic conjunctivitis is also possible and peri-ocular self-trauma may be evident due to allergic skin disease. Although this is more common in dogs, allergic skin disease should be considered and registered veterinary nurses can assist by gathering a comprehensive dermatological history to aid diagnosis (Redbond, 2022). FEK is a rare condition characterised by proliferative lesions of the cornea, moderate conjunctivitis and ocular discharge. The exact cause is unknown, though it is thought to be an immune-mediated condition (Romaneck and Sebbag, 2021). FEK can be diagnosed by cytology through corneal/conjunctival scraping, typically presenting with eosinophils. FEK should be ruled out as the treatment is considerably different to that of infectious causes; topical corticosteroids and cyclosporines can be beneficial (Romaneck and Sebbag, 2021).
Lipogranulomatous conjunctivitis presents differently to other types of conjunctivitis and is typically associated with non-ulcerative white lipid nodules in the palpebral conjunctiva. The condition may be unilateral or bilateral and often diagnosis is made by clinical appearance or histology of the excised tissue.
Treatment and long-term management
Treatment of these cats and application of frequent topical medications can cause stress and exacerbate the condition (Rodan and Heath, 2016). Registered veterinary nurses can play an important role in client education and maintaining good welfare standards in these patients (Hargrave, 2017). A holistic approach is often required and long-term stress management should be considered. Clinical responses are variable and the client must be aware of the potential outcomes prior to commencing treatment. Additionally, the registered veterinary nurse should ensure that the owner has the ability to meet the medication regime; both in application and timing. The use of medication charts can be particularly helpful and assigning a registered veterinary nurse to the case can provide the owner with confidence and a point of contact. To encourage long-term management of these patients, registered veterinary nurses can demonstrate cat-friendly and fear-free handling techniques prior to discharge following the AAFP/ISFM Feline-friendly handling guidelines (Rodan et al, 2011). Prior to handling feline patients, a hand should be offered near the cat before handling further, allowing the cat to initiate contact where possible. When handling in the home environment, the owner may wish to purchase a matt or non-slip surface where the cat can feel secure (Endersby, 2018). In addition to handling techniques, demonstration of topical eye medications should be performed. A towel can be useful to wrap around the cat and then the head should be gently raised to aid application; care should be taken in brachycephalic breeds as it is easy to cause iatrogenic harm. In some cases, hospitilsation may be required for the initial course of medication due to owner constraints or difficulty when medicating.
Frequent examination may be required initially, although careful consideration should be taken with the frequency of re-examinations, as this may cause further stress for the patient. Advising owners on ways to reduce stress on route to the practice may help reduce stress during the consultation. Clients should be advised to use a top-opening carrier to allow easy entry and exit with the use of a towel/blanket to allow the cat to hide (Endersby, 2018). Additionally, the carrier can be used as a resting area for the cat at home on a permanent basis to positively re-inforce carrier training (Pratsch et al, 2018).
Conclusions
Feline conjunctivitis is relatively commonly in veterinary practice, often presenting due to infectious aetiologies. However, it is important explore feline conjunctivitis thoroughly as secondary and other causes are possible and the clinical signs may be non-specific and similar. Registered veterinary nurses are well placed to help throughout the diagnosis by gathering history, creating nursing care plans and by supporting the veterinary surgeon in consultation. Additionally, registered veterinary nurses can have a positive impact on the treatment and long-term management of feline ocular diseases with holistic education and support of owners.
KEY POINTS
- Registered veterinary nurses should have a thorough understanding of the disease processes of feline conjunctivitis to be able to discuss feline ocular disease, treatment options and to educate clients.
- Ocular examination and diagnostics requires a team approach from both the registered veterinary nurse and veterinary surgeon.
- Feline conjunctivitis can be non-specific and present similarly despite different aetiologies; a thorough ophthalmic and clinical examination is required for every case.