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What is the definition of dry eye syndrome ?
Dry eye syndrome is e multifactorial disease of the ocuular surface that results in symtoms of discomfort, visual disturbance and tearfilm instability with potential damage to the ocular surface. It's accompanied by increase in osmolarity of the tearfilm and inflammation of the ocular surface.
What systems compromise the Lacrimal function unit (LFU)?
- The Lacrimal function unit (LFU) compromises the:
- - lacrimal glands
- - ocular surface: cornea, conjunctiva, meibomian glands
- - eyelids
- - sensory and motornerves connecting the tructures above
What is the function of the Lacrimal function unit (LFU) ?
- The overall functions of the LFU are to preserve
- - tearfilm integrity: lubricating, antimicrobial, nutriotional rolls
- - Ocular surface health: maintaining corneal transparency and surface stem cell population
- - Quality of image projected onto the retina
What are tearfilm stabalizing factors?(3)
- -Tears secretion
- -Delayed Clearance
- -Tear composition
- Tear-film stability is thretened when the above consituents are altered
Which are the core mechanisms of dry eye syndrome?
- 1. Tear hyper opsmolarity, activates a cascade of inflammatory events at the ocular surface and a release of inflammatory mediators into the tears
- -Due to high evaporation (antihypertensives, antihystamines, antimuscarinic agents)
- - Due to low lacrimal flow
- - also due to tearfilm instability
- 2. Tear-film instability
- - due to hyperosmolarity
- - Evaporation / MGD
- - Xerosing medication
- - Xerophthalmia
- - Ocular Allergy
- - Topical preservative use
- - Contactlens wear
What are causes of reduced lacrimal secretion? (6)
- Low androgens
- Systemic drug use that inhibit flow
- Inflammatory lacrimal damage: Sjögren, non-Sjögren dry eye syndrome, lacrimal obstruction
- Inflamation causing receptor block:M3Receptor block by M3 antibodies
- Reflex secretory block due to LASIK, CLwear, topical anesthetic
What are the two mayor etiologic causes of dry eye?
- 1. Aqueous-deficient Tear dysfunction
- 2. Evaporative Tear dysfunction
What are the groupings of Aqueous-deficient Tear Dysfunction (ATD)?
What are the two types of Evaporative Tear Dysfunction (ETD)
- Intrinsic: regulation of the evaporativ eloss from the tearfilm is affected
- Extrinsic: conditions associated with evaporation through pathologic effects one the ocular surface
Name Intrinsic factors in Evoporative Tear Dysfunction (4)
- Disorder of lid aperture
- Low Blink Rate
- Drug action accute (eg retinoids)
Name extrinsic factors of Evaporative Tear Dysfunction (4)
- Vitamin A-deficiency
- Topical drugs preservatives
- Contactlens wear
- Ocular Surface Disease e.g. allergy
Describe the Shirmertest?
- This is the basic secretion test
- Its preformed by instilling a topical anesthetic A thin oaoer filterstrip 5mmwide and 35mm long is placed in the inferior fornix.<5mm in 5 minutes is suggestive fore ATD.
Describe the Shirmer test I
This test measures the asic and reflex tears combines. It is rpeformed without instillation of topical anesthetics.
Decribe the Shirmer II test
- This test measures the defect reflex reaction
- No anethetic is instilalted and de nasal mucosa is irritated with a conton-tipped applicator.
- Weeting of less then 15mm after 5 minutes is positive
Which findings suggest ATD?
- Abnormal Shirmer testing
- Exposure pattern of conjunctival and/or corneal staining
- Filamentary keratopathy
Describe features of advanced staged of Aqueous Tear Deficiency
- Corneal calcification
- Band keratopathy
- Keratinization of the cornea and conjunctiva
Describe de stare test
Thsi sia rappid assesment of dry eye. After a few blinks, a patient is asked to look at a visual acuity chart. The time untile the image blurs should be more then 8 second.
What are the signs of dry eye on examination?
- Conjunctival hyperemia
- Decreased tear meniscus
- Irregular corneal surface
- Debris in the tear film
- Epithelial keratopathy (exposure or linear staining)
- Filaments in more severe dry eyes
Which laboratory tests can be preformed for the evaluation of ATD?
- Lacrimal gland biopsy (rarily)
- Salivary glad biopsy
- Conjunctival inpression cytology to monitor progression of conjunctiva (goblet cell density, metaplasia, keratinization)
- Autoantibiodies: ANA, RF, SS-A and SS-B
What is the use of cyclosporine A 0.05% in dry eye?
- Thsi treats the inflammatory component of dry eye. Modulation of the ocular surface inflammatpry response might reduce lacrimal acini destruction ad increade neural responsiveness , thereby improving lacrimal secretion.
- Approximately 70% of patients with moderate to severe dry eye seem to benefit from it.
Which medications other then lubricating tears may be useful for the treatment of ATD?
- Corticosteroid (off-label)
- Hyaluronic acid
- Autologous serumd rops
- Cholinergic agonist to stimulate the muscarine receptor in lacrimal gland Pilocarpine and cevimeline , only in Xerostomia
Which surgical treatments can be considered in ATD?
- Punctal occlusion: reversible or irriverible
- Correction of eyelid malpositions
What is the indication for permanent punctum occlusion?
- Minimal basal tear secretion
- Punctate keratopathy
- no significant inflammation
- (Older patients)