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Conjunctiva definition
Highly vascular mucous membrane lining the inner eyelids
Covers the sclera
Conjunctival blood supply origin
Ophthalmic artery
Anterior ciliary arteries
Lacrimal artery
Sclera tissue characteristic
Thin tissue
Effects of contact lens wear on conjunctiva
Hyperemia
Injection
Chemosis
Inflammation
Hyperemia and injection definition
Engorgement and dilation of bulbar and palpebral conjunctival blood vessels
Causes of hyperemia and injection
Hypoxia (reduced oxygen)
Desiccation (drying due to loss of moisture)
Tightly fitting lenses
Mechanical rubbing
Immunological response to soiled lenses or solutions
Purpose of hyperemia response
Increase oxygen supply
Facilitate migration of immune cells (e.g., leukocytes)
Chemosis definition
Edema of bulbar conjunctiva
Cause of chemosis
Inflammation caused by soiled or poorly fitting lenses
Palpebral conjunctival inflammation causes
Immune response to antigens on lens surface
Mechanical response to poor surface or edge design
Papillae definition
Tiny bumps on the superior palpebral conjunctiva
Causes of papillae
Lens rubbing
Irritation from lens deposits
Irritation from lens solutions
Severe papillae symptoms
Large papillae
Hyperemic papillae
Mucous discharge
Eyelid tissue characteristic
Loose tissue
Eyelid lining
Palpebral conjunctiva
Primary eyelid function
Rewet corneal surface with tear film
Rewet conjunctival surface with tear film
Flush away debris
Protect the eyes from injury
Effect of CL wear on superior palpebral conjunctiva
Papillary hypertrophy (enlargement or swelling of papillae)
Blink changes with CL wear
Less frequent blinks (especially with rigid lenses)
Less complete blinks (especially with rigid lenses)
Consequence of altered blink rate
Desiccation of the cornea
Desiccation of the conjunctiva
Lid sensitivity change with RGP wear
Eyelids become desensitized to the lens edge during adaptation
Benefit of reduced lid sensitivity
Increased patient comfort
Risk of reduced lid sensitivity
Predisposes to inflammation that may go undetected
Risk of reduced lid sensitivity
Predisposes to mechanical insult that may go undetected
Ptosis definition
Eyelid drooping
Ptosis with rigid CL wear
Caused by decreased lid sensitivity and daily pulling during tug-and-blink removal
Mechanism of CL-related ptosis
Partial disinsertion of levator muscle due to repeated tug-and-blink removal
Ptosis with soft lenses
Soft lenses rarely cause ptosis
Tear film layer order (outer to inner)
Lipid; Aqueous; Mucin
Lipid layer composition
Waxes, cholesterols, triglycerides
Lipid layer function
Slows evaporation of the aqueous portion of tears
Prevents tears from spilling out over the eyelids
Lipid layer secretion
Meibomian glands
Lipid layer secretion
Accessory sebaceous glands of Zeiss
Lipid layer thickness
Approximately 0.1 micron
Aqueous layer composition
Water, electrolytes, proteins
Aqueous layer role
Makes up the bulk of the tear layer
Aqueous layer function
Maintains corneal hydration
Carries nutrients to the cornea
Contains protective elements against microbes
Aqueous layer secretion
Glands of Kraus and Wolfring
Aqueous layer thickness
Approximately 7 microns
Mucin layer composition
Glycoproteins and mucopolysaccharides
Mucin layer function
Adheres to corneal microvilli creating a hydrophilic surface for aqueous attachment
Mucin layer secretion
Goblet cells
Mucin layer thickness
Approximately 0.02–0.05 microns
Optical function of tear film
Creates a smooth anterior refracting surface for sharp optics
Impact of tear film disruption
Any disruption causes decreased vision
Protective components of tear film
Immunoglobulins, lysozyme, lactoferrin
Metabolic functions of tear film
Supplies cornea with glucose and oxygen
Metabolic functions of tear film
Removes shed epithelial cells
Metabolic functions of tear film
Removes carbon dioxide
Effects of CL wear on tear film parameters
Affects tear production, evaporation rate, osmolarity, pH, temperature, volume, and structure
Evaporation rate change with CL wear
Usually increased due to thinner or absent lipid layer
Tear film structure measurement methods
Tear film interferometry or Tearscope to view fringe patterns
Tear film structure changes
Not consistently described; varies across studies
Effect of rigid lenses on tear film structure 1
Lipid layer thin/absent
Aqueous layer thin and dries rapidly
Mucoid layer appears absent
Effect of hydrogel lenses on tear film structure
Lipid layer thin and its thickness and stability vary with lens water content/thickness
Aqueous layer present
Mucoid layer thicker but more loosely attached
Tear film stability with CL wear
Generally decreased
Consequences of decreased tear film stability
Drier lens surface
Possible symptoms (e.g., discomfort)
Effect on borderline dry eye patients
Patients may become symptomatic with contact lens wear
Clinical importance of considering CL effects on ocular surface
Helps determine follow-up schedule and wear time
Helps determine management plans
Helps guide patient education
Helps determine contact lens material and design
Goals of CL management
Minimize problems related to contact lens wear
Maximize success with contact lens wear