Contact Lens (Conjunctiva and Tear film)

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59 Terms

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Conjunctiva definition

  • Highly vascular mucous membrane lining the inner eyelids

  • Covers the sclera

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Conjunctival blood supply origin

  • Ophthalmic artery

  • Anterior ciliary arteries

  • Lacrimal artery

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Sclera tissue characteristic

Thin tissue

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Effects of contact lens wear on conjunctiva

  • Hyperemia

  • Injection

  • Chemosis

  • Inflammation

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Hyperemia and injection definition

Engorgement and dilation of bulbar and palpebral conjunctival blood vessels

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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

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Purpose of hyperemia response

  • Increase oxygen supply

  • Facilitate migration of immune cells (e.g., leukocytes)

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Chemosis definition

Edema of bulbar conjunctiva

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Cause of chemosis

Inflammation caused by soiled or poorly fitting lenses

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Palpebral conjunctival inflammation causes

  • Immune response to antigens on lens surface

  • Mechanical response to poor surface or edge design

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Papillae definition

Tiny bumps on the superior palpebral conjunctiva

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Causes of papillae

  • Lens rubbing

  • Irritation from lens deposits

  • Irritation from lens solutions

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Severe papillae symptoms

  • Large papillae

  • Hyperemic papillae

  • Mucous discharge

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Eyelid tissue characteristic

Loose tissue

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Eyelid lining

Palpebral conjunctiva

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Primary eyelid function

  • Rewet corneal surface with tear film

  • Rewet conjunctival surface with tear film

  • Flush away debris

  • Protect the eyes from injury

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Effect of CL wear on superior palpebral conjunctiva

Papillary hypertrophy (enlargement or swelling of papillae)

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Blink changes with CL wear

  • Less frequent blinks (especially with rigid lenses)

  • Less complete blinks (especially with rigid lenses)

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Consequence of altered blink rate

  • Desiccation of the cornea

  • Desiccation of the conjunctiva

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Lid sensitivity change with RGP wear

Eyelids become desensitized to the lens edge during adaptation

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Benefit of reduced lid sensitivity

Increased patient comfort

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Risk of reduced lid sensitivity

Predisposes to inflammation that may go undetected

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Risk of reduced lid sensitivity

Predisposes to mechanical insult that may go undetected

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Ptosis definition

Eyelid drooping

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Ptosis with rigid CL wear

Caused by decreased lid sensitivity and daily pulling during tug-and-blink removal

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Mechanism of CL-related ptosis

Partial disinsertion of levator muscle due to repeated tug-and-blink removal

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Ptosis with soft lenses

Soft lenses rarely cause ptosis

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Tear film layer order (outer to inner)

Lipid; Aqueous; Mucin

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Lipid layer composition

Waxes, cholesterols, triglycerides

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Lipid layer function

  • Slows evaporation of the aqueous portion of tears

  • Prevents tears from spilling out over the eyelids

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Lipid layer secretion

Meibomian glands

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Lipid layer secretion

Accessory sebaceous glands of Zeiss

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Lipid layer thickness

Approximately 0.1 micron

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Aqueous layer composition

Water, electrolytes, proteins

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Aqueous layer role

Makes up the bulk of the tear layer

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Aqueous layer function

  • Maintains corneal hydration

  • Carries nutrients to the cornea

  • Contains protective elements against microbes

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Aqueous layer secretion

Glands of Kraus and Wolfring

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Aqueous layer thickness

Approximately 7 microns

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Mucin layer composition

Glycoproteins and mucopolysaccharides

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Mucin layer function

Adheres to corneal microvilli creating a hydrophilic surface for aqueous attachment

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Mucin layer secretion

Goblet cells

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Mucin layer thickness

Approximately 0.02–0.05 microns

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Optical function of tear film

Creates a smooth anterior refracting surface for sharp optics

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Impact of tear film disruption

Any disruption causes decreased vision

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Protective components of tear film

Immunoglobulins, lysozyme, lactoferrin

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Metabolic functions of tear film

Supplies cornea with glucose and oxygen

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Metabolic functions of tear film

Removes shed epithelial cells

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Metabolic functions of tear film

Removes carbon dioxide

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Effects of CL wear on tear film parameters

Affects tear production, evaporation rate, osmolarity, pH, temperature, volume, and structure

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Evaporation rate change with CL wear

Usually increased due to thinner or absent lipid layer

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Tear film structure measurement methods

Tear film interferometry or Tearscope to view fringe patterns

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Tear film structure changes

Not consistently described; varies across studies

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Effect of rigid lenses on tear film structure 1

  • Lipid layer thin/absent

  • Aqueous layer thin and dries rapidly

  • Mucoid layer appears absent

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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

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Tear film stability with CL wear

Generally decreased

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Consequences of decreased tear film stability

  • Drier lens surface

  • Possible symptoms (e.g., discomfort)

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Effect on borderline dry eye patients

Patients may become symptomatic with contact lens wear

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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

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Goals of CL management

  • Minimize problems related to contact lens wear

  • Maximize success with contact lens wear