Immune response
Function of immune system to protect the body from micr-organisms and other harmful material activities by detecting the presence of invading foreign body and initiating healing process
Under active immune system
Dysfunction of immune response resluts in under active immune system which makes the individual vulnerable to infection
Alleriges
Over active response of immune system by releasing inappropriate and unnecessary inflammatory response to harmless material e.g pollen. Response varies in individual as it can be annoying/harmless in some and in other severs cases such as corneal damage can be sight threatening
Hypersensitivity
Allergic reaction to materials the body has already beem exposed to
Types of hypersensitivity
Type 1 - acute
Type 2 - cyclotoxin
Type 3 - Immune complex
Type 4 - Cell mediated
Type 1 Hypersensitivity reaction
- Px comes in contact with an antigen
- B and plasma cells produce antibodies specific to that antigen.When px come in contact with the same antigen the antibody will recognise.
- Primary antibody is an immunoglobin termed IgE y shaped which attached to the mast cell and is found throughout the body
- Antigen attaches to the antibody bound on the mastcell
- Mast cell degranulates and releases histamine and prostaglandin which inflammatory mediators which communicate signals and for inflammation to begin.
Type 4 hypersensitivity
Antigen is presented to T cell and antibody releases inflammatory mediators which directly damage tissue
Seasonal and parennial allergic conjunctivas
Both are a type 1 hypersensitivity reaction
- SAC, acute present at specific time of the year, antigen is grass/polen
- PAC, chronic Present all year around antigen are animal hair, dust, dust mites
Symptoms of SAC AND PAC
Symptoms are similar make sure to note down the time of the year px got the allergy
- Itching, caused by the release of histamine rubbing the eyes ehances mast cell degranulation so whilst it provides temporary relief, vengence and itchiness will soon return
- Bilateral, airborne antigen so effects both eyes equally and at the same time
- Redness, allergic reaction causing inflammation which causes vasolodilation increased blood flow to the affected tissue resulting in red conjunctiva and eyelid
Lacrimation, allergic reation caused by over active immune system which triggers a defence process which produces tears to remove antigen. The px may experience temporary blured vision due to unstable tear film which can be resolved with a few strong blinks
- Sneezing/nasal discharge, defend process to remove antigen
Atopy
Genetic predisposition of type 1 hypersensitivity
Grading scale
Important to tract the level of redness in px eyes to see for any changes
- Grading scales are used to record the severity of clinical signs
Signs of SAC and PAC
- Vasodilation- due to inflammation caused by allergic reaction resulting in increased blood flow to the effected tissue like lids and conjunctiva
- Eyelid oedema, increase in the blood vessel permeability due to inflammation causes the leakage of fluid into surrounding tissues makes the eyelid look puffy and swollen. gentle pressure on the eyelid will feel fluid filled compared to normal
-Conjunctival chemosis, increase in blood vessel permeability cause by inflammation causes fluid to escape into surrounding tissue fluid in the conjuctiva cause the generally stretched conjunctiva to loosen. Due to loose conjunctiva the light that will reflect will be looser and irregular than normal
Papillae
Raised lumps at the surface of the palpebral conjunctiva. To view evert both the upper and lower eyelid. The core of each pupillae has a central blood vessel. Papillae shows the accumulation of inflammatory cell in the conjunctiva tissue. The raised lumps give palpebral conjunctiva a rough look.
The CCLRU is used to measure the palpebral roughness
Cornea involvement in SAC and PAC
Cornea is usually not involved. To confirm florusiene dye is added to the eye and checked under the blue filter on the slit lamp for any epithelial damage. Check for any patches and bright spots and record the findings on a record card even if you can not see anything
SAC and PAC management
Managed by eyecare professional in clinics does not usually require referral to ophthamologist
- Environment, remove pets and dust from home and use anti allergen linen. Avoid freshly cut grass/pollen, close windown to avoid contact with airborne pollen and wear tightly fitted sunglasses when going out
- Cold compresses using flannel for 5 mins bd promotes vasoconstriction
- Eyewashes, artifacial tears and ocular lubricant
- Start with antihistamines and combine with mast cell stabaliser for long term use
Vernal Keratoconjunctavitis
Uncommon but severe
- Recurrent and can be sight threathning
- Caused by hypersensitivity type 1 and type 4 therefore more sevre than SAC and PAC
- Genetically predisposed in individuals as they have raised level of IgE in tear film and mast cells in conjunctiva
Symptoms of vernal keratoconjunctavitis
- Bilateral, can be unsymmetrical
- Present all year around peak during warmer spring summer time
- Itchy eyes more severe than SAC and PAC
- Redness and lacrimation also present in some cases
- White string mucoid discharge absent is SAC and PAC
- Corneal involvement key difference between sac and pac
- Px complains of blurred vision, pain and photophobia
- Blurred vision, irritation caused by bright light hitting the superficial layer of the cornea send signals to pain receptors which are innervated by trigimanal nerve
- Pain, high number of pain nerves that send signal to the brain
- Photophobia, corneal damage disrupts the transmission of refraction and light through the corneal epithelium
VKVSigns
- Palpebral conjunctiva
Hyperaemia, vasodilation in lids and conjunctival tissue.
Giant papillae formed by the accumulation of inflammatory cells due to increased blood vessel permability. Eversion of eyelid show cobble stone appearance supperior lid worse than inferior
Limbal
- VKC associated with the formation of papillae in the limbal. Raised gelatonous lumps formed due to accumulation of inflammatory cells. Inflammatory cells eosinophils form white dots on the apex of the papillae also know as horner trot dots
- Cornea
Cornea and VKC
Due to the formation of papillae on the surface of the palpebral conjunctiva and limbal release toxins which are lethal for corneal epithelium. Toxic chemicals cause formation of gaps and depression on the epithelium to view these flouroscene dye and blue filter can be used on the slit lamp which cause the gaps to glow and can easily detect corneal epithelial loss. This is called superficial punctate keratitis SPK. First sign of corneal involvement with condtions invlvling the cornea
As the disease progressesthere are more dots and more corneal damagae. The dots coalese to form a larger region of epithelial cells loss at this stage individual dots join and form a dense patch and have a macro-erosion. Corneal epithelium usually repain within 48 hours however in this case the due to the toxic chemicals and inflammation epithelial cell has no chnace to repair itself hence corneal damage is presistent which cause blurred vision, pain and photophobia.
What happens if VKC is left untreated
- If left untreated papillae forms into plaque due to non-healing epithelium
- Sub-epithelial scarring under the epithelium due to non-healing epithelium forms permanent opacification of certain areas of cornea
- Neurovasculistaion, formation of new blood vessels due to chronic inflammation and scarring
Management of VKC
- If corneal and limbal involvement urgent refferal to the ophthalmologist otherwise just the routine referral
- Mast cell stabalisers, reduces histamine in ocular area
- Cold compression to promotes vasoconstriction reduces redness and swelling caused in the lids
- Ophthalmologist can prescribe topical eyedrops
AKC
Severe allergic eye disease has high risk of sight threatening and corneal involvement
- AKC follows up after VKC which is present in childhood
- Primmarly type 1 and type 4 hypersensitivity
Symptoms of AKC
Similar of VKC
- Bilateral
- Itchy eyes severe
- Redness, inflammation of the eyelid and conjunctiva tissue caused by vasodilation
- Lacrimation, stringy white mucoid discharge
- Corneal involvement, pain, photophobia and blurred vison
Signs of AKC
Eyelid
Inflammation associated with AKC is much more severe than in other eye diseases
- Hyperaemic and thickened eyelid due vasodilation caused by increase in the blood vessel permeability
- Skin is dry around the eye and begins to crack creating small fissure
Conjunctiva
- Hyperaemia of the palpebral and balber conjunctiva gives the appearance of angry inflammated eye
- Pupillary reaction exertion of the eyelids will reveal papillaes
- Conjunctival scarring, caused by the chronic inflammation white featureless appearance
- Symblepharon scarring, severe scarring abnormal attachment between the the palpebral and balber areas due to inflammation
Cornea
- Corneal involvement can be sight threatning
- Stages include: SPK, macro-erosion, plaque ulcer, sub-eptithelial scarring and necurovascularisation
