3.1.7 - Tears/Dry eyes

What is dry eye?

A disorder of the tear film due to tear deficiency or excessive evaporation, which causes damage to the interpalpebral ocular surface and is associated with symptoms of ocular discomfort.

• “Dry eye is a multifactorial, symptomatic disease characterized by a loss of homeostasis of the tear film and/or ocular surface, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities are etiological factors.”

What is the purpose of the lacrimal layer?

Reduces water evaporation from the aqueous layer

Secreted by: Meibomian gland, glands of Zeiss, glands of Moll.

Only 10% of the aqueous layer evaporates as the lipid layer prevents evaporation.

What is the purpose of the aqueous layer?

• Carries nutrients and oxygen to the eye and carries away waste

• Hydrates the cornea and prevents it from drying out.

Secreted by:

• Main lacrimal gland for reflex secretion

• Basal secretion by accessory lacrimal glands of Krause and Wolfring

What is the purpose of the mucus layer?

• Trap debris and epithelial cells, which are then removed through blinking.

• Also allows for tear stability and adheres to the epithelial corneal cells and conjunctival goblet cells.

How do tears drain in the eye?

through the puncta - through canaliculi, into lacrimal sac.

• Pumped into there from lid action and gravity feed to lower punctum

Causes of dry eyes

• Allergies

• Decreased hormones associated with aging

• Pregnancy and associated hormonal changes

• Thyroid eye conditions

• Eyelid inflammation (blepharitis)

• Medication/supplement use including, but not limited to: psychiatric medicines, OTC cold medicines, anti-histamines, beta-blockers, pain relievers, sleeping pills, diuretics, hormonal replacement, and oral contraceptives

• Sjogren's syndrome (dry mucus membranes throughout body)

• Other autoimmune disorders including Lupus and/or Rheumatoid Arthritis

• Chemical exposures / injuries to the eyes

• Eye surgery

• Infrequent blinking, associated with staring at computer or video screens (which is becoming a more frequent contributor), and Parkinson's

• Environmental (dusty, windy, hot/dry)

• Contact lens use

• Neurologic conditions including: stroke, Bell's palsy, Parkinson's, trigeminal nerve dysfunction

• Exposure keratitis, in which the eyelids do not close completely during sleep (i.e. lagophthalmos)

• Post refractive surgery (LASIK or PRK)- while typically transient can become a chronic issue in some

• Inflammatory eye conditions, including uveitis / iritis

• Diabetes

• Infectious Keratitis, including Herpes Simplex and Herpes Zoster Keratitis

• Neurotrophic Keratitis

• Vitamin A deficiency (rare in US except in certain diseases such as Crohn's)

Sx of dry eyes

• Burning

• Stinging

• Itching

• Tearing

• Sandy or gritty feeling

• Scratchy or foreign-body sensation

• Discharge

• Frequent blinking

• Mattering or caking of the eyelashes (usually worse upon waking)

• Redness

• Blurry or fluctuating vision (made worse when reading, computer, watching television, driving, or playing video games)

• Light-sensitivity

• Eye pain and/or headache

• Heavy eye lids

• Eye fatigue

How to assess for dry eyes?

• TBUT - evaporative dry eye

  • line break = ADDE

  • spot break = mucin deficient

  • random = evaporative

• TMH

  • G1 = >0.3mm

  • G2 = 0.2mm

  • G3 = <0.1mm

• MGD/BLEPH

• STAINING

• Tear film quality - specular reflection on endothelium

• Schirmer test

Schirmer test 1

• Get Px to look up, place sterile strip within the lateral third of the eyelid, Px should do gentle blinks

• Without anaesthesia

• measures basic and reflex tearing (total tear production)

  • >10mm after 5 mins = normal

  • 5-10mm = borderline

  • <5mm = aqueous deficient dry eye

Schirmer test 2

• Uses anaethetic

• nasal stimulation is irritated = more tears

• only tests for basic secretion of tears

  • >15mm = normal

  • <10mm = dry eyes

Weakness of Schirmer test?

• Poor variability and reproducibility

• can detect Px with severe ADDE but not those with mild ADDE

Fluorescein

• Does not stain

• enters damaged or missing epithelial cells

• fluoresces green when exposed to blue light

• best visibility at 520-530nm

• shows where the surface cells are broken

Lissamine green

• stains damaged, dead or degenerated cells

• does not fluoresce - viewed in white light

• shows where the surface cells are unhealthy

DEWS 2

A report which aimed to create an evidence based definition and classification for DED - provided an overview of RF - modifiable and non-modifiable - forms an aqueous/evaporative spectrum - tailoring management based off Px signs - brings consistency and clarity

• Provides a global standard

• integrates signs + sx + pathophysiology

• guides treatment + management

Created by Tear Film & Ocular Surface Society

DEWS 2 concept

• Loss of TF homeostasis; any factor can disrupt the TF

  • Tear film instability

  • Tear hyperosmolarity

  • Ocular surface inflammation

  • Epithelial damage

  • Neurosensory dysfunction

These form a vicious cycle that causes dry eye disease

DEWS 2 - Step 1

One of 2 validated DED questionaries

• Ocular Surface Disease Index (OSDI)

  • score out of 48 - 12 questions graded 1-4

• DEQ-5 (5 item dry eye questionnaire)

  • equal to or > 6 = dry eye

DEWS 2 - Step 2

If +ve dry eye found from questionnaire;

• Homeostasis marker needs to be found;

  • TF stability

  • Tear Osmolarity

  • Ocular surface staining

DEWS 2 management;

Step 1;

• warm compress/lid hygiene

• educating px (diet - omega 3/fish oil)

• modification of local environment

Step 2;

• Preservative-free eye drops to avoid preservative-induced toxicity

• Teatree oil treatment

• Punctal occlusion

Step 3;

• Soft bandage lenses

• Allogenic serum eye drops

Step 4;

• Surgical punctal occlusion

• Topical corticosteroids

DEWS 3

Not yet officially published - DEWS 2 still considered gold standard

Looking at more modern issues due to lack of sleep, increased VDU use & medications

Update on neurosensory dysfunction and ocular pain

Refresh/update from DEWS 2

Px with chronic dry eye suffer more from anxiety and depression

e.g of ADDE

• Sjogren’s disease

• Age

• Medication e.g HBP/anti-histamine meds

• Surgery

• Lack of vitamin A + Omega-3 in diet

• Trauma

e.g of EDE - deficiency of lipid layer

• MGD

• Lid related disorders - incomplete blinking

• not blinking enough - screens

• CL wear - affects the lipid layer