Summary
Summary Complete notes for contact lenses
- Module
- Optometry (B510)
- Institution
- Glasgow Caledonian University (GCU)
Summary of 7 pages for the course Optometry at GCU (Soft contact lenses)
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KeratoconusDefinition: Non-inflammatory, progressive ectasia (distortion) of the cornea causing an irregular,
thinned corneal shape and therefore blurred vision.
- Incidence: 1 in 3000 to 1 in 10,000 depending on ethnicity
- Age of onset: typically late teens or early twenties
- Usually bilateral but often asymmetric
Risk Factors
- Asian ethnicity
- Eye rubbing
- Family history
- Atopy – form of allergy
Sub-Clinical
- No signs on slit lamp examination
- Unaided vision 6/6 or better
- Patient asymptomatic
- Retinoscopy reflex may be a little irregular (scissor like reflex)
- Mild thinning & irregularity on topography
- May go undetected/undiagnosed
Stages of Keratoconus
Early
- No signs on slit lamp examination or subtle Vogts’s striae
- Subtle thinning of corneal section
- Fleischers ring (iron deposits at base of cone)
- Mild split/scissors ret reflex
- Low myopic/astigmatic refraction
- VA corrects well
- Pachymetry under 550 microns
Moderate
- Very split/scissors reflex
- Oil droplet reflex
, - High myopia and astigmatism
- Difficult end point on refraction
- VA poor
- Pachymetry under 450 microns
Advanced
- No useful ret reflex as cornea so distorted
- Poor VA
- Munsens sign – V shaped indentation in lower lid when looking down
- Hydrops – breaks in Descemets membrane causing oedema, resolves with scarring
- CCT under 440 microns
Symptoms
• Blurred or poor quality vision
o Frequent changes in prescription recently, particularly with increasing
myopia/astigmatism
o Dissatisfaction with glasses or with previous optometrist
▪ Monocular diplopia or ghosting
▪ Glare
Investigation
- Refraction with retinoscopy
- Slit lamp examination
- Pachymetry (average normal cornea 550microns)
- Keratometry (normal range 7.10- 8.60) Are the mires distorted?
Management
- Prescribe glasses but warn Rx may change. Consider partial Rx or balance lens if high
cylinder and/or significant anisometropia
- Refer routinely to local cornea service
- Consider contact lenses
What happens at the hospital eye department?
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