Week 1: intro Flashcards
A systematic review is a ___________ survey of a topic in which all primary studies of the highest level of evidence have been systematically identified, appraised and then summarized according to an explicit and reproducible methodology
may or may not include a meta-analysis
comprehensive
What is the PICO approach?
- P: patient, problem, population
- I: intervention
- C: comparison, control gorup
- O: outcome measure
What is a meta analysis?
A statistical approach to combine the results of separate but similar studies, so the results can be generalized to a larger population
What type of study is considered the gold standard for medical and clinical research?
randomized controlled trials
When are cohort studies performed?
When a randomized control trial is not feasible or ethically possible
What are cohort studies and case-control studies unable to determine?
cause-effect relationships
both can indicate an association between disease and expsoure
Cross-sectional studies are what type of study?
observational
measures the point prevalence of health outcomes
unable to assess disease incidence or determine what came first, the exposure or the outcome
What are the benefits of a SOAP note?
improved patient care, help healthcare profesionals better document, recall and apply details about a specific case
What are risk factors for filamentary keratitis?
- aqueous-deficient dry eye disease
- corneal exposure
- ptosis
- ocular surgery
- systemic disease
- anticholinergic medications
- ocular surface abnormalities
etiology of filamentary keratitis
What can cause in increase in the tear film mucus to aqueous ratio?
A decrease in aqueous tear production
etiology of filamentary keratitis
what makes up the composition of the filaments in filamentary keratitis
degenerated epithelial cells and mucus
etiology of filamentary keratitis
What allows filaments to anchor to the ocular surface?
small defects in the corneal epithelium
What are the symptoms of filamentary keratitis?
- foreign body sensation
- photophobia
- blepharospasm
- increased blink reflex
- excessive tearing
- ocular pain
treatment of filamentary keratitis
How are filaments removed?
using cotton tip applicator or fine-tipped forceps
what are the treatment methods for filamentary keratitis?
- removal of filaments
- PF lubricants (long-term)
- punctal plugs
- contact lenses (comfort, promote healing)
- topical corticosteroid and cyclosporine emultion to reduce inflammation
- mucolytic agent: breakdown mucus filaments (N-acetylcysteine)
- hypertonic agents, autologous serum tears and amniotic membranes for refractory cases
3 functions of the lipid layer
- prevent evaporation of tears
- prevent spillover of tears at lid margin
- prevent skin lipids from moving onto the ocular surface
lipid layer is 0.1 microns thick
2 purposes of the aqueous layer
- immunological protection of the eye
- reduce friction (anti-adhesive and lubricant properties)
What does the mucin layer interact with?
glycocalyx
3 functions of the mucin layer
- facilitate the adhesion of the aqueous layer to the corneal surface
- maintain stability of tears on the surface of the cornea
- act as a viscoelastic buffer against mechanical shock
What forms wax esters found in the lipid layer of tears?
long-chain fatty acids linked by an ester bond with a long-chain alcohol
mostly non-polar but amphipathic
What makes up diesters found in the lipid layer of tears?
hydroxy fatty acid, linked via an ester bond to a fatty acid and either another fatty acid or another alcohol
also mostly non-polar but amphipathic
how are polar lipids aligned in the tear film?
hydrophilic heads aligned toward the aqueous phase and hydrophobic tails aligned toward the lipid phase
Which type of lipids serve to increase the thickness of the lipid layer?
nonpolar lipids
take a more central position in the lipid ayer
What makes up the aqueous layer?
proteins and electrolytes
what binds to antigens to act as a line of defense?
antigens are usually proteins but can also be carbohydrates, lipids or nucleic acids
immunoglobulins
all immunoglobulins bind to foreign substances in order to initiate an immunological reponse
What gives the mucin layer its viscoelastic buffer properties and creates the jelly-like consistency of the mucous layer?
complex carbohydrates
What is the dual mechanism of action of doxycycline?
- antibacterial: inhibits protein syntheses (bacteriostatic)
- Anti-inflammatory: inhibits cytokines, enzymes and matrix metalloproteinases
what is an ocular side effect of doxycycline?
pseudotumor cerebri
What are side effects of doxycycline?
nausea, vomiting, diarrhea, epigastric irritation, inhibition of bone growth, photosensitivity, intracranial hypertension, hypersensitivity reactions, hepatoxicity
What are contraindications to doxycycline?
pregnant women, children <8 years old
What is the pharmaceutical agent that breaks down mucin into glycoproteins by reducing the disulphide bonds of the mucoproteins?
how do we treat filamentary keratitis?
N-Acetylcysteine (NAC)
brand names: mucomyst, acetadote, fluimucil
What are ocular side effects of N-Acetylcysteine?
eye irritation, redness
What are systemic side effects of N-acetylcysteine?
nausea, vomiting, diarrhea, GERD, GI bleeding, anaphylaxis (IV NAC)
What are contraindications to IV NAC?
patients prone to fluid overload (cardiomyopathy or CHF patients)
What condition is caused by the rupture/ schisis of Descemet’s membrane?
Acute Corneal Hydrops
What type of patients are prone to getting hydrops?
patients with corneal ectasia
including: atopic disease, keratoconus, pellucid marginal corneal degeneration, keratoglobus, previous ocular surgery, elevated IOPs
What is the prognosis for acute corneal hydrops?
self-limiting condition, spontaneously resolves after 2-4 months
What are the symptoms of Acute Corneal Hydrops?
blurry vision, pain or irritation, redness, photophobia, epiphora
What is the treatment and management of hydrops?
- hyperosmotics for edema
- cycloplegics for pain
- antibiotics
- topical steroids for inflammation
- BCL for comfort
- intracameral air/gas to reattach Descemet
- Compression sutures
- endothelial keratoplasty
- penetrating keratoplasty
What type of cells are found in the corneal epithelium?
nonkeratinized stratified squamous epithelial cells formed by basal cells
What type of junctions adhere the basal cells to the basement membrane of the epithlium?
hemidesmosomes
2 important characteristics of Bowman’s membrane?
- not a true basement membrane
- does not regenerate
What makes up the dense regular connective tissue of the corneal stroma?
collagen and glycosaminoglycans (GAGs)
produced by keratocytes
Why is the corneal stroma 78% water?
high concentration of GAGs
What is the purpose of GAGs in the corneal stroma?
ensures the regular spacing of the collagen fibrils
Is Descemet’s membrane or Bowman’s membrane a true basement membrane?
Descemet’s membrane
produced by endothelium, regenerates when injured, increases in thickness throughout life
Where are the pumps located that help keep the cornea clear?
endothelium
endothelial pumps utilize active transport to create an osmotic gradient by moving Na+ and HCO3- from the stroma to the aqueous
What are the 5 main factors that control corneal hydration?
- barrier function of the epithelium and endothelium
- stromal swelling pressure
- endothelial pumps
- tear evaporation
- intraocular pressure
zonula occludens of the epithelium offer twice the resistance to water flow compared to the macula adherens of the endothelium
Explain the equation: IOP = SP + IP
- SP: stromal swelling pressure: the force necessary to prevent stroma swelling (~55 mmHg); SP decreases with stromal edema
- IP: stromal imbibition pressure: negative pressure exerted by GAGs that draws fluid into the cornea (-40 mmHg); dependent on endothelial function
intact endothelium = (-) IP -> no corneal edema
endothelium dysfunction= (+) IP -> corneal edema
Which type of edema will happen when IOP exceeds SP and IP is (+)
this is the case in acute angle closure
epithelial edema
Which type of edema will happen with a normal IOP and low SP?
in the case of endothelial dystrophy
Stromal edema
