Lacrimal System PDF

Secretory vs Excretory Lacrimal System Secretory (Afferent) lacrimal system: responsible for tear production ○ Basal tears: used to lubricate and nourish the ocular surface ○ Reflex tears: produced in response to ocular surface irritation or emotions Larger q...

Secretory vs Excretory Lacrimal System Secretory (Afferent) lacrimal system: responsible for tear production ○ Basal tears: used to lubricate and nourish the ocular surface ○ Reflex tears: produced in response to ocular surface irritation or emotions Larger quantity than basal tears (100x) Reflex tearing occurs w/the stimulation of branches of the ophthalmic nerve or in response to external stimuli such as intense light Excretory (Efferent) lacrimal system: responsible for tear drainage ○ 90% of tears are drained by the nasopharynx and 10% evaporate Lacrimal system is innervated through the lacrimal nerve, a branch of the ophthalmic division of the trigeminal nerve (CN V) Tear Film Function: keeps the surface moist ○ Acts a lubricant between eyelid and globe ○ Traps debris and removes sloughed off epithelial cell ○ Source of oxygen for cornea ○ Smooth refractive surface ○ Antimicrobial ○ Maintain corneal hydration ○ Aids in ocular surface wound healing Composed of 3 layers ○ Lipid (oily) layer: outermost layer Produced by: meibomian glands (MG), Zeiss and Moll Glands Function: thicken, stabilize, and decrease evaporation of the aqueous layer In healthy eyes, the lipid layer should be ~0.10 um (if more than.10, patient will see blurry) Blinking releases the lipid layer, if forceful blinking then more lipids are released ○ Aqueous: middle layer Produced by: accessory exocrine lacrimal glands of Krause and Wolfring (produce basal) Stimulated tears are produced by the main lacrimal gland (produce reflex) Function: provides oxygen to the cornea, cushions the globe from the eyelids and contains antimicrobial proteins Lactoferrin and lysozymes - help combat viruses, bacteria, fungi Production rate decreases with age ○ Mucin: innermost layer Produced by: goblet cells and tarsal crypts of Henle Function: lubricate the lids and serves as the absorbing site for the aqueous layer  Mucin also gives stability to aqueous layer to prevent washout Also performs waste management If disrupted or contaminated, it will elicit tear break up Tears Drainage Some tears are evaporated, others are absorbed by the conjunctival tissue but ~75% passes through the nasolacrimal drainage system Nasolacrimal system consists of: ○ Puncta - superior and inferior ○ Canaliculi - vertical and horizontal ○ Lacrimal sac ○ Nasolacrimal duct Evaluation of lacrimal system (Tear film) Quality: ○ Fluorescein staining ○ TBUT ○ Rose Bengal/Lissamine Green staining Quantity: ○ Schirmer Test I & II ○ Red phenol thread Ophthalmic dyes: Fluorescein Penetrates areas of corneal epithelium and conjunctival epithelium where intracellular junctions are disrupted Observed under direct diffuse cobalt blue illumination at low ○ Wratten filter In addition to evaluating corneal and conjunctival epithelium disruptions, it also aids in tear film stability and tear meniscus ○ Tear break-up time (TBUT)  Quantifies the stability of the precorneal tear film Must be performed before any other procedure that may mechanically or pharmacologically alter the ocular surface Anesthesia, tonometry Procedure: Apply fluorescein using a wetted NaFl strip Under low magnification w/ cobalt blue illumination, scan the cornea and ask the patient to blink several times and then stare ahead without blinking Count the seconds it takes for the first tear film breaks to appear Holly and Lamps mechanism Tear film thins out uniformly by evaporation -> some lipid molecules are attracted by mucin layer -> mucin becomes hydrophobic and tear film ruptures Indicate of tear film instability in all different causes of dry eye W/ fluorescein (invasive)-- reflex tearing Non-invasive (toposcope) The more dry spots, the more the instability Do not perform after instilling anesthesia- false positives! Values of < 10 s are considered abnormal 5-9 s are borderline dry eye < 5 s are clearly indicative of dry eye Ophthalmic dyes: Rose Bengal Stains damaged conjunctival and corneal epithelial cells Useful in the detection of keratoconjunctivitis sicca (KCS) and early detection of ocular surface disease Rose bengal is very painful and could be toxic If lissamine green is available, it is preferred Ophthalmic dyes: Lissamine green Affinity for staining dead and degenerated cells Proper illumination levels are important when evaluating ○ If illumination is too intense or bright, the contrast will be diminished causing underestimation of the staining ○ If normal or average illumination is used, staining may appear washed out ○ Recommended to star w/ low illumination and increase until staining is best appreciated Conjunctival and corneal staining Note for any staining present on the cornea or conjunctiva Record: dye used, staining pattern, reach each eye separately  Schirmer Test I Evaluate the integrity of the lacrimal secretion system and how many tears are being produced Measure primarily aqueous production, due to the aqueous layer composing the largest part of the tear film Total tear secretion is the sum of basal and reflex secretion ○ No anesthesia is used Schirmer I is performed using Whatman no. 41 filter paper ○ The head of the strip is folded, 5 mm Apply the strip w/ the folded end onto the lower lid margin at the lateral canthus after drying the excess tears ○ Make sure the cornea is touched! ○ Ask the patient to look nasally and insert temporally Instruct the patient to keep their eyes open and blink normally ○ Give the patient a distance target Evaluate the strip after 5 min and measure the amount of wetting on the filter Results: ○ Less than 10 mm is significant for decreased lacrimal secretion ○ Less than 5 mm is diagnostic of lacrimal insufficiency ○ If over 25 mm, excessive reflex tearing, basal secretion test should be performed Basal secretion test: ○ This will allow for basal reflex measurement only, eliminating the reflex by irritation ○ Apply anesthetic and measure basal secretion production This technique, with anesthesia, is the most used clinically since basal tear reflex is measured  proptosis -> lagothalmos -> dry eye) Medications, such as antihistamines (Benadryl, Xyzal, Claritin, Allegra) Blink rate, palpebral fissure widening, and video display terminal (VDT) use can also influence in DES ○ Presentation: Pseudoepiphora due to aqueous deficiency Contact lens wearer may remain symptomatic, but SCL wearers for over 10 years, typically develop DES Medications such as anticholinergic, anxiolytics and antihistamines can decrease aqueous production ○ Blinks, eyelids and lashes in relation w/ DES The eyelids neural, muscular, and structural components must remain intact in order to maintain a healthy tear film Problems w/ the tear film may present from: Lagophthalmos Myokymia Tear hyperosmolarity w/ decreased tear volume during sleep Overnight cl wear Bell’s palsy Ectropion Inflammation or trauma to the eyelids Trichiasis Blepharitis ○ Meibomian gland dysfunction (MGD)  Diffuse SPK pattern Epiphora (tearing) ○ May be caused by a series of conditions: Hypersecetion or a defective drainage system ○ Hypersecretion: a condition presenting secondary to inflammation or ocular surface infections Typically it is associated w/ other systems, linked to the underlying disease Viral conjunctivitis ○ Defective drainage: Malposition of puncta Obstruction of the drainage system Could be from puncta to nasolacrimal drainage Lacrimal pump failure: secondary to lower lid laxity or weakness of orbicularis oculi (ex: facial nerve palsy) Punctum stenosis ○ Occurs due to a narrowing or an occlusion of the punctum Narrowing is considered to be < 0.3 mm in diameter ○ Conjunctivochalasis ○ It is loose redundant conjunctiva, not attributed to edema  ○ Occurs secondary to aging and mostly is asymptomatic ○ In some cases, may cause ocular irritation and epiphora ○ Dacryocystitis ○ Inflammation of the lacrimal sac ○ Presents commonly in infants and postmenopausal women In infants, chronic infection typically accompanies the NLD obstruction ○ Usually presents secondary to a nasolacrimal duct obstruction ○ Signs: Erythematous, tender swelling over the nasal aspect of the lower lid in the nasal periorbital area Accompanied by mucoid or purulent discharge, which can be expressed from the punctum ○ ○ Canalicular Disorders Congenital anomalies of the canaliculi Acquired stenosis of the canaliculi ○ Bacterial, viral or fungal origin Obstruction of the canaliculi secondary to: ○ Steven-johnson syndrome (hypersensitivity rxn to sulfa medications for ex.= blisters all over skin) ○ Ocular ○ Systemic chemotherapy w/ fluorouracil ○ Topical idoxuridine for HSK Canaliculitis ○ Rare disorder, consisting of infection or inflammation of the canaliculus  Punctal plug insertion ○ Only accounts for 2% of patients with epiphora ○ ○ Disorders of the Nasolacrimal Duct (NLD) Congenital Primary acquired nasolacrimal duct obstruction (PANDO) Trauma Intranasal disorder Acquired punctal occlusion Disorders of the Secretory System Alacrima Lacrimal hypersecretion Paradoxical lacrimation (crocodile tears)- when eating/moving jaw Hemolacria = bloody tears Lacrimal gland tumors Dacryoadentitis ○ Infectious or tumor ○ Inflammation of the lacrimal gland ○ Typically from an infectious cause ○ Mostly viral but bacterial and fungal can also be possible ○ Other causes such as thyroid eye disease and Sjorgren’s syndrome ○ Signs: Unilateral swelling of the lateral eyelid, giving an S-shape ptosis Tenderness of the lacrimal gland fossa and injection Possible reduced lacrimal secretions