myopia walter huang, od yuanpei university department of optometry

MyopiaMyopia

Walter Huang, ODWalter Huang, OD

Yuanpei UniversityYuanpei University

Department of OptometryDepartment of Optometry

DefinitionDefinition

The common name for this refractive error The common name for this refractive error is is near-sightednessnear-sightedness

Patients with myopia are known as Patients with myopia are known as myopesmyopes

DefinitionDefinition

When parallel rays of light enter the eye When parallel rays of light enter the eye ((with accommodation relaxedwith accommodation relaxed) and come ) and come to a single point focus to a single point focus in front ofin front of the retina the retina

EtiologyEtiology

Axial lengthAxial length The axial length of the eye is The axial length of the eye is longerlonger than than

normal due to imperfect emmetropizationnormal due to imperfect emmetropization The most common cause of myopia for The most common cause of myopia for high high

myopesmyopes

EtiologyEtiology

Refractive powerRefractive power The refractive power of the eye is The refractive power of the eye is too strongtoo strong

Curvature myopiaCurvature myopia Cornea or lens has a steep curvature (e.g., keratoconus)Cornea or lens has a steep curvature (e.g., keratoconus)

Increased index of refraction (e.g., cornea, lens)Increased index of refraction (e.g., cornea, lens)

Anterior movement of the lens (e.g., nuclear Anterior movement of the lens (e.g., nuclear sclerosis)sclerosis)

PrevalencePrevalence

AgeAge At birth: 24 to 50%At birth: 24 to 50% As birth weight decreases, the amount of myopia As birth weight decreases, the amount of myopia

increases in premature infantsincreases in premature infants The mean refractive error for full-term infants is +2.00 The mean refractive error for full-term infants is +2.00

DD The prevalence of myopia decreases by 1 year old The prevalence of myopia decreases by 1 year old

due to the process of emmetropizationdue to the process of emmetropization 5 to 6 years old: 2% (>-0.50DS)5 to 6 years old: 2% (>-0.50DS) 13 to 14 years old: 15% 13 to 14 years old: 15%


AgeAge In Taiwan (1995)In Taiwan (1995)

7 years old: 12%7 years old: 12%



18 years old: 84%18 years old: 84% In western countriesIn western countries



GenderGender In general, there are no significant differences In general, there are no significant differences

between males and femalesbetween males and females Progression of myopia tends to begin and end Progression of myopia tends to begin and end

earlier in femalesearlier in females High myopia is more common in femalesHigh myopia is more common in females


EthnicityEthnicity Higher prevalence in Asians, Arabs, and JewsHigher prevalence in Asians, Arabs, and Jews Lower prevalence in Caucasians, Blacks, and Lower prevalence in Caucasians, Blacks, and

South Sea IslandersSouth Sea Islanders


Urban versus rural communitiesUrban versus rural communities Myopia is more common in urban Myopia is more common in urban

communities than in rural onescommunities than in rural ones

ProgressionProgression

Myopia tends to increase linearly until the Myopia tends to increase linearly until the middle or late teenage years, at which middle or late teenage years, at which point, it levels offpoint, it levels off

The earlier a child becomes myopic, the The earlier a child becomes myopic, the more rapidly the condition tends to more rapidly the condition tends to progressprogress

Juvenile-Onset MyopiaJuvenile-Onset Myopia

DefinitionDefinition Myopia in which the age of onset is 8 to 12 Myopia in which the age of onset is 8 to 12

yearsyears


EtiologyEtiology Evidence for genetics influencesEvidence for genetics influences

Greater similarity of refractive error and ocular Greater similarity of refractive error and ocular structures in identical twins than in fraternal twinsstructures in identical twins than in fraternal twins


EtiologyEtiology Evidence for genetics influencesEvidence for genetics influences

Increased prevalence of myopia in children of Increased prevalence of myopia in children of myopic parentsmyopic parents

Probability of a child being myopic is:Probability of a child being myopic is:

40% when both parents are myopic40% when both parents are myopic

2020 to to 30% when one parent is myopic30% when one parent is myopic

<10% when neither parent is myopic<10% when neither parent is myopic


EtiologyEtiology Evidence for environmental influencesEvidence for environmental influences

Association between near work, education, and Association between near work, education, and myopiamyopia

Children who do a lot of near work, like reading, tend to Children who do a lot of near work, like reading, tend to become myopicbecome myopic

Myopia is more common where occupations require Myopia is more common where occupations require extensive near workextensive near work

Myopia and Visual AcuityMyopia and Visual Acuity

Uncorrected VAUncorrected VA Refractive Error (D)Refractive Error (D)

20/3020/30 0.500.50

20/4020/40 0.750.75

20/6020/60 1.001.00

20/8020/80 1.501.50

20/12020/120 2.002.00

20/20020/200 2.502.50

SymptomsSymptoms

Blurry vision at distanceBlurry vision at distance

Clear vision at nearClear vision at near

SquintingSquinting

Occasional headachesOccasional headaches

SignsSigns

Decreased visual acuities at distanceDecreased visual acuities at distance

Clinical TestsClinical Tests

Visual acuity tests - distanceVisual acuity tests - distance

RetinoscopyRetinoscopy

Subjective refractionSubjective refraction

ManagementManagement

Divergent or minus lenses in spectacles or Divergent or minus lenses in spectacles or contact lensescontact lenses

CycloplegicsCycloplegicsSurgerySurgeryRefractive surgeryRefractive surgery


SpectaclesSpectacles Single vision glassesSingle vision glasses Bifocal glassesBifocal glasses

More effective in children with near esophoriaMore effective in children with near esophoria


Contact lensesContact lenses Soft contact lensesSoft contact lenses Rigid gas permeable contact lensesRigid gas permeable contact lenses Ortho-keratology contact lensesOrtho-keratology contact lenses Corneal reshaping therapy contact lensesCorneal reshaping therapy contact lenses


Contact lensesContact lenses Ortho-keratologyOrtho-keratology

Rigid gas permeable contact lenses are used to Rigid gas permeable contact lenses are used to flatten the corneaflatten the cornea

Results are unpredictable (0 to 5.00 D of change)Results are unpredictable (0 to 5.00 D of change)

Two eyes may respond differently in anisometropiaTwo eyes may respond differently in anisometropia

Procedure may induce astigmatismProcedure may induce astigmatism

Retainer lens is required; otherwise, the patientRetainer lens is required; otherwise, the patient’’s s prescription may return to normalprescription may return to normal


Cycloplegics (e.g., atropine)Cycloplegics (e.g., atropine) Reduce the ability to accommodateReduce the ability to accommodate May slow the progression of myopiaMay slow the progression of myopia


SurgerySurgery Radial keratotomy (RK)Radial keratotomy (RK)

TechniqueTechnique Eight cuts with a blade in a radial pattern are made on Eight cuts with a blade in a radial pattern are made on

the surface of the corneathe surface of the cornea The depth of each cut is through approximately 85 to The depth of each cut is through approximately 85 to

90% of the cornea90% of the cornea


SurgerySurgery Radial keratotomy (RK)Radial keratotomy (RK)

Post-surgical complicationsPost-surgical complications Hyperopic shiftHyperopic shift Diurnal fluctuations of refractive error and visual acuityDiurnal fluctuations of refractive error and visual acuity GlareGlare Corneal scarringCorneal scarring


Refractive surgeryRefractive surgery Photorefractive keratectomy (PRK)Photorefractive keratectomy (PRK)

TechniqueTechnique High energy photons from an excimer laser are used to High energy photons from an excimer laser are used to

photoablate a small amount of tissue from the anterior photoablate a small amount of tissue from the anterior corneal surface and sculpt the corneacorneal surface and sculpt the cornea


Refractive surgeryRefractive surgery Photorefractive keratectomy (PRK)Photorefractive keratectomy (PRK)

Post-surgical complicationsPost-surgical complications Eye painEye pain Corneal disruptionCorneal disruption Blurry visionBlurry vision Prolonged duration of drug useProlonged duration of drug use Greater time needed for eyesight recoveryGreater time needed for eyesight recovery


Refractive surgeryRefractive surgery Laser in-situ keratomileusis (LASIK)Laser in-situ keratomileusis (LASIK)

TechniqueTechnique A microkeratome is used to cut a flap of superficial A microkeratome is used to cut a flap of superficial

corneal tissuecorneal tissue The flap is lifted back, exposing the underlying corneal The flap is lifted back, exposing the underlying corneal

stroma stroma The excimer laser is used to perform tissue removal in The excimer laser is used to perform tissue removal in

the corneal stromathe corneal stroma The flap is repositioned in its original position and The flap is repositioned in its original position and

adheres to the underlying corneal stroma without the adheres to the underlying corneal stroma without the need for suturesneed for sutures


Refractive surgeryRefractive surgery Laser in-situ keratomileusis (LASIK)Laser in-situ keratomileusis (LASIK)

Post-surgical complicationsPost-surgical complications Severe dry eye syndromeSevere dry eye syndrome Poor night visionPoor night vision Reduced contrast sensitivityReduced contrast sensitivity AstigmatismAstigmatism


Refractive surgeryRefractive surgery Points to consider after the surgical procedurePoints to consider after the surgical procedure

Use eyedrops, as prescribed by the ophthalmologistUse eyedrops, as prescribed by the ophthalmologist

Be careful not to allow chlorinated water , shampoo, and Be careful not to allow chlorinated water , shampoo, and sweat to come into contact with the eyessweat to come into contact with the eyes

Wear sunglasses when outside to protect the eyes from Wear sunglasses when outside to protect the eyes from sunlightsunlight

Remember to go back to the hospital for regular follow up Remember to go back to the hospital for regular follow up visits with the ophthalmologist and to get eyedropsvisits with the ophthalmologist and to get eyedrops

Pathological Conditions Associated Pathological Conditions Associated with Myopiawith Myopia

CataractCataract Nuclear cataract causes a myopic shiftNuclear cataract causes a myopic shift


DiabetesDiabetes High blood glucose levels cause increased High blood glucose levels cause increased

sorbital levels in the lenssorbital levels in the lens Water rushes in and dilutes the sorbital in the Water rushes in and dilutes the sorbital in the

lenslens Lens bulges and results in a myopic shiftLens bulges and results in a myopic shift


MarfanMarfan’’s syndromes syndrome Suspensory ligaments breakSuspensory ligaments break Subluxation of lens occurs superiorly and Subluxation of lens occurs superiorly and

temporally and results in a very high increase temporally and results in a very high increase in myopiain myopia

myopia walter huang, od yuanpei university department of optometry

Documents

years myopia

prevalence of myopia

progression myopia

years old

females high myopia

common cause of myopia

females progression

rural communities myopia