Allergic Conjunctivitis refers to the inflammation of the conjunctiva. The conjunctiva is the tissue that covers the inside of the eyelids and the white parts of the eyeball as well. It is usually caused by allergens and irritants, such as pollen, dust mites, pet dander or other allergy causing agents.
Allergic Conjunctivitis is a common condition of the eye and very important as a topic for your Ophthalmology paper. Read this blog post thoroughly to learn all about this condition and boost your NEET PG preparation.
It is a form of ocular allergy that primarily presents irritation and excessive watering in the eyes due to immunoinducive agents.
It can be acute, seasonal, or perennial allergic reactions.
The types of allergic conjunctivitis are vernal keratoconjunctivitis, atopic and phlycenular keratoconjunctivitis.
Allergy caused by endogenous antigens→ Staphylococcus aureus and tuberculosis infections.
Presents watering and itching.
Characteristic of phlyctenular conjunctivitis→ nodule of phycten near the limbus and conjunctival congestion
Involvement of cornea leads to a fascicular ulcer, which later develops into ring ulcer.
It is a type 4 hypersensitivity reaction→ treated with steroids
Recurrence of PC due to infection→ antibiotics, such as tetracycline.
It is a type 1 hypersensitivity reaction caused by exogenous allergens, such as pollen, dust, etc.
Common in summer and children.
Presents itching, watering, and ropy discharge containing mucin.
It does not develop follicular reactions but only papillary reactions.
Three forms of vernal conjunctivitis
Three forms are palpebral, limbal and mixed.
It is characterised by papillary reaction with cobblestone appearance
It develops horner trantas spots: white dots containing eosinophils
When it involves the cornea, it forms the cupid’s bow, also known as pseudogerontoxon.
Gerontoxon is another name for arcus senilis. The epithelial lesion in vernal conjunctivitis appears like arcus senilis. Hence the name.
Later stages lead to shield ulcer: deposition of mucus and calcium phosphates in micro-erosions
Maxwell Lyon’s sign is a pseudomembrane formed due to excessive deposition of mucus on the papilla.
Antiallergic mast cell stabilisers and antihistamines: olopatadine and azelastine
Mast cell stabiliser: sodium cromoglycate and nedocromil sodium
Antihistamines: apenastin and bepotastine.
Mild steroids: fluorometholone and loteprednol etabonate, when others do not work.
Acetylcysteine to dissolve mucus
Common temperate regions and winters.
Predominant in adults with no gender predilection.
Findings in Atopic keratoconjunctivitis
Dennie morgan folds: skin folds under the eyes due to excessive rubbing.
Keratoconus: due to rubbing
Madarosis: loss of eyebrows and eyelashes.
Hertoghe’s sign: loss of lateral one-third eyebrows
Treatment for atopic keratoconjunctivitis
In case of severe allergic reactions: immunomodulators such as cyclosporin and calcineurin inhibitors, such as tacrolimus.
Other causes of Hertoghe’s sign
It is a spectrum of ocular diseases due to Vitamin A deficiency.
WHO grading of xerophthalmia
The grading helps determine the severity of the condition. The signs are denoted by X and a subscript. They are
Xn → night blindness nyctalopia: the earliest sign
X1a → conjunctival xerosis
X1b → bitots spot
X2 → corneal xerosis
X3a → keratomalacia in less than one-third of the cornea
X3b → keratomalacia in more than one-third of the cornea (keratomalacia is liquefactive necrosis of cornea)
Xs → cornea scarring
Xf → xerophthalmia fundus → white spotted fundus anddecreased amplitude in electroretinogram
Q. why do we see decreased amplitude in ERG?
Ans. ERG represents the activity of layers of rods and cones. Since xerophthalmia affects rods and bipolar cells, ERG shows a dip in amplitude.
More about bitots spot
Bitots spot: is keratinised epithelia and infection by corynebacterium xerosis. It is more common on the temporal side:
Pathological changes in xerophthalmia
Loss of goblet cells
Squamous metaplasia with keratinisation.
Treatment for xerophthalmia
Child more than one year: one lakh IU of vitamin A on the 0th, 1st, and 14th day
Less than one year: half the dose
Oral: double the dose of injectival vitamin A.
Local treatment for xerophthalmia
Intense lubrication: eyedrops containing methylcellulose derivatives or sodium hyaluronate
Topical: retinoic acid
Other causes of nyctalopia
Late stage of primary open-angle glaucoma
Congenital stationary night blindness (CSNB)
Choroidal dystrophy: choroideremia and gyrate atrophy
Two forms of CSNB
fundus albi punctatus: night blindness with white spots in the fundus
Oguchi’s disease: night blindness with pale spots on the fundus.
Pale fundus restores its appearance when a person suffering from Oguchi’s disease stays in darkness for about an hour. The cause of the phenomenon is the overstimulation of rods.
It is conjunctival degeneration characterised by triangular fibrovascular subepithelial ingrowth of bulbar conjunctiva over the limbus. It occurs commonly on the nasal side.
Ugly appearance if it is not covering the pupil; otherwise, harmless.
Diminished vision when it encroaches on pupils.
Elastotic degeneration of conjunctival stroma: similar to pinguecula.
Structure of Pterygial Formation
Body: part from the triangle's base to the border of the pupil.
Head: apical part of pterygium that protrudes into the pupil. and
Avascular halo: the region around the tip: the destruction of bowman’s membrane by metalloproteinases.
Stocker’s line occurs due to iron deposition near the head.
Exposure to UVB rays
What else does UVB cause?
In addition to pterygium, it can cause phot ophthalmia, also called snow blindness → UVB rays reflect off the snow and cause corneal epithelial erosion.
It is a scarring that appears like pterygium.
How to differentiate it from pterygium?
Glass rod test: if the glass rod passes through scarring, it is pseudo-pterygium.
Bare sclera technique
The recurrence rate after the bare sclera technique is 30 to 40%..
Mitomycin C, an antimitotic drug administered preoperatively reduces the recurrence.
It is the most effective modality
cut a portion of the conjunctiva in the upper or superior temporal quadrant, including limbal stem cells:
Stitch it over the affected area: conjunctiva at excised region regenerates.
It stands for Pterygium Extended Resection Followed By Extended Conjunctival Transplantation.
It is a modified version of autografting wherein the conjunctiva excised is much larger.
It is a yellowish-white mound near the limbus formed by elastotic degeneration of conjunctival stroma
It is commonly nasal.
It does not extend on to the cornea.
Not needed: if asymptomatic.
Mild steroids or lubricants: if presents itching
Excision is an option but not preferable.
It is a condition caused by impaired functions of any layer of the tear film. It becomes a disease with the onset of ocular inflammation.
Dysfunction of any of the three layers of tear film causes inadequate volume, unstable secretion, or dysfunction in the tear.
Layers of Tear Film After Cornea
Mucin layer: formed of goblet cells of conjunctiva → helps spread tear over the ocular surface
Aqueous layer: thickest layer: formed of lacrimal and accessory lacrimal glands→ lubrication.
Lipid layer: formed by meibomian glands in the lens → prevents evaporation of tear.
Keratoconjunctivitis sicca is the deficiency of the aqueous layer.
Rheumatoid arthritis is a connective tissue disorder, and its association with keratoconjunctivitis sicca leads to secondary Sjogren syndrome. Hence, patients with rheumatoid arthritis experience dry eye disorder.
Clinical Manifestations of Dry Eye
Gritty sensation of foreign bodies
Excessive mucus deposition
Diminished vision when precorneal tear film involved
Tear meniscus height lesser than 0.25 mm.
Punctate epithelial keratitis
Investigation of Dry Eye Disorder
Slit lamp examination
To visualise tear meniscus height, which is the length of a triangular cross-section between lower lid margin and cornea.
Schirmer’s test 1 It involves placing Whatman paper No. 41 under the lower lid for 5 minutes: Wet length of less than 15mm indicates dry eye. It measures both basal and reflex secretion.
Schirmer’s test 2 Measures only basal secretion using topical anaesthesia.
Phenol red thread test Yellow-colored thread is brought in contact with the eye for 15 seconds, and the length of the stain that turns red is measured. Less than 6 mm indicates severe dry eye.
Tear film break-up time
It is the time taken for a dry spot to appear from the last blink.
Less than 10 seconds indicates severe dry eye.
While Schirmer’s and phenol red thread tests help diagnose aqueous layer dysfunction, TBUT helps diagnose deficiency in the meibomian and lipid layer.
Rose Bengal or lissamine green staining
They help visualize dead cells and mucus.
Low levels of lactoferrin indicate dry eye.
Measures the number of goblet cells.
Tear osmolality measurement
A high value indicates a dry eye.
Treatment is either medical or surgical
Lubricating eye drops containing methylcellulose derivatives, polyvinyl alcohol with povidone, and hyaluronate derivatives.Acetylcysteine to dissolve mucus.Cyclosporin for inflammation
Lacrimal punctal occlusion.For temporary measure Collagen plug that can be dissolved in a few weeks.Silicone plugs for prolonged occlusion.For permanent measure thermal cautery of proximal canaliculate.
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