Eye Care In Modern Life Dr. Dorothy Fan Department of Ophthalmology & Visual Sciences November 2009 dorothyfan@cuhk.edu.hk
Structure of the Eye Information age > 90% of sensory input Blindness is one of the most fearful disabilities
Structure of the Eye Nowadays, not just life and death but also Quality Enhancement
Structure of the Eye
Structure of the Eye Accommodation Camera: no presbyopia Eye: presbyopia after age of 40 Functional Visual system Camera Perception >> Camera
Refractive Errors & Refractive Surgery
Refractive error What is it?
Refractive Error A mismatch between the refractive power and the focusing distance of the eye
Myopia The refractive power of the eye is too much so that light focuses in front of the retina
Hyperopia The refractive power of the eye is too weak so that light focuses behind the retina
Astigmatism The refractive power is different in different meridian
Hong Kong Story Number of cases Age of onset Severity 90% of University students are myopic
Hong Kong Story Prevalence of myopia Kindergarten: 3.25% Primary school: 36.09%
Myopia Causes of myopia?? Nature Vs Nurture
Myopia Nature Genetic factors Interactive with environment
Myopia Nurture? Visual task e.g. reading, writing, TV, computer, etc. No definite conclusions yet
Correction of Myopia Spectacles Contact lens Operation
Correction of Myopia Spectacles Contact lens Operation
Contact Lens At least 35 million contact lens wearers worldwide 10% of the US population trend in Hong Kong
Contact Lens Commonly used types Hard lens Rigid gas-permeable lens (RGP) Soft lens Daily wear Extended wear
Contact Lens Improvement in the past 10-20 years More gas permeable material Better design Better fitting techniques Better after care products
Contact Lens Contact lens wear: overall
Contact Lens - Complications Change ocular surface environment Hypoxia Allergy & Toxic Mechanical trauma Infection
Contact Lens - Complications Complications develop esp with improper care Regular check up is required
Contact Lens - Care Self Check See Feel Look
Correction of Myopia Spectacles Contact lens Operation
Correction By changing the eyeball length By changing the refractive power Changing the power of the existing structure Adding extra refractive medium
Corneal Refractive Surgery Commonest refractive procedure Radial keratotomy (RK) Photorefractive Keratectomy (PRK) LASIK LASEK
Corneal Refractive Surgery In myopia, the refractive power is too strong for the axial length Light focuses in front of the retina
Corneal Refractive Surgery In myopia, the refractive power is too strong for the axial length Light focuses in front of the retina cornea is flattened Chinese were among the first to put stones on the eye at night to achieve a flatter cornea in the morning
Corneal Refractive Surgery In hyperopia, light focuses behind the retina cornea is steepened
Photorefractive Keratectomy Painful Delayed Re-epithelialization haze Keratitis Elevated Intraocular Pressure Regression esp for high myopia
LASIK State of the Art Laser Assisted Stromal In-situ Keratomileusis
LASIK good candidates Refraction +6D to -13D Astigmatism <6D Enough corneal thickness Small pupil
LASIK - Results FDA (less than -7D) Better than 20/20 = 85% Better than 20/40 = 99% Depends on patients pre operative refraction
Complications
LASIK - complications Common problems dry eyes, halos at night Flap complications and infections are rare but could be serious ~0.3%
Risk Vs Benefits
Cataract Lens Within eye ball Behind the iris
Cataract Lens Main function: Focusing objects +10D (spectacle-equivalent)
Severity Cataract
Cataract Causes of cataract Congenital Traumatic Senile Drug induce Diabetes Others...
Cataract A major problem in Hong Kong Growing population Longevity Aging population
Cataract - Treatment Observation? Medication? Laser? Operation?
Cataract - Treatment Removal of the cataract lens + Correction of refractive error (+10D = 1,000 degree)
Guidelines for VDT Use Maintain visual comfort by proper ambient lighting Place VDTs away from windows and overhead lights. Clean screen to improve visibility regularly Proper working distance
Guidelines for VDT Use Top of VDT is slightly below eye level Blink eyes regularly Relax accommodation by looking at distant objects (30s every 30 mins) Maximize contrast
Guidelines for VDT Use Place reference material close to screen Use single-vision glasses instead of bifocal or progressive lens Rigid instead of soft contact lens Polarized, tinted or dark glasses for people with migraine
Guidelines for VDT Use With proper visual hygiene, one can enjoy trouble-free computing
Structure of the eye Refractive errors Contact lens Refractive surgery Cataract Computer eye care