MYOPIA

MYOPIA : PROGRAM

Myopia: program I

• Generalities– Definition– Etiology– Epidemiology

• Classification:– According to magnitude– Clinical

Myopia: program II

• Myopia simple:– Characteristics– Clinical exam– Prescription criteria. Factors:

• Age• Anisometropia• Binocularity• Control of myopic progression

Myopia: program III

• Degenerative myopia:– Characteristics– Clinical examen– Prescription criteria. Factors:

• Type of optical compensation

• Pseudomyopia:– Characteristics – Clinical exam– Prescription criteria

Myopia: program IV

• Nocturnal myopia:– Characteristics – Treatment

MYOPIA: GENERALITIES

Myopia: Generalities I

• Refractive condition in which the image of an object at a distance does not form on the retina but focuses in front of the retina.

• Structural causes of myopia could be:– Excessive axial longitude of the eye– Excessive power of the eye– Error in the relationship between axial

longitude and power

Myopia: Generalities II

• The etiology of myopia depends on diverse factors. Such as:– Hereditary– Magnitude– Sex– Work NV– Diet– Etc.

MYOPIA: CLASSIFICATION

Myopia: classification I

• According to the magnitude of the myopia:– Low myopia: between -0,25 and -3,00 D– Moderate myopia: between -3,25 and -6,00

D– High myopia: between -6,25 and -10,00 D– Very high myopia: above -10,00 D

Myopia: Classification II

• Clinically:– Simple myopia– Magna, degenerative, or pathological

myopia– Pseudomyopia– Noctunal myopia

Myopia: classification III

• Most common type of myopia• Is recognized by:

– Good VA in DV with correction – Absence of structural anomalies of the

ocular sphere (no pathologies)– Retinoscopy subjective– Progresses limitedly

• School age: 0.50 D/year• After 18-20 years of age it has few variations

SIMPLE MYOPIA

Myopia: Classification IV

• Secondary to an excessive axial longitude of the eye

• Associated to alterations or degeneration of certain ocular structures

• With the passage of time the VA can be diminished

• Alterations to the posterior pole (mainly):– Myopic cone– Loosening of the retina– Macular alterations– Etc

MAGNA OR DEGENERATIVE MYOPIA

Myopia: Classification V

• Pseudomyopia– Result of an accomodative spasm– Subjective exam is more negative than the

retiniscopy

• Nocturnal myopia– VA reduction in conditions of low illumination

MYOPIA: SIMPLE MYOPIA

Simple myopia: Characteristics I

Factors associated with the prevalence of simple myopia

Age •2%-5% at 6 years of age•25%-35% in young adults

Sex •Greater in women

Race •Greater in white races, Japanese, Jews, and Chinese.•Lesser in darker races

Reading and education

•Increases when the reading and educational levels increase

Occupation

Greater in cases which consist of activity in NV

Simple myopia: Characteristics II

• Age – School age:

• At 6 years of age: 5% myopes• At 18 years of age: 25-35% myopes

– 20-60 years of age: stabalization– > 65 years of age: do not forget the relationship between

nuclear cataracts and myopia

Simple myopia: Characteristics III

• Possible risk factors for the development of myopia:– Family history of myopia– Emmetropia at pre-school age– Astigmatism against the rule– Altered accomodative function– Endophoria in NV– Prolonged work in NV and at very short

distances– Obstruction in the formation of images during

the first few years

Simple myopia: Symptoms and signs

• Symptoms – Blurry vision in DV– Rarely symptoms in NV

• Signs – Blinks to reduce the palpebral

aperture– Good VA in NV– Mydriasis– Exodeviation– Bringing glasses closer

Simple myopia : Clinical exam

• Retinoscopy and subjective have similar value

• With the adequate Rx the VA tends to reach 20/20 or even 20/15

• Absence of related anomalies in the funduscopy.

• If the subject has never worn glasses he/she could show a reduced amplitude of accomodation for his/her age

Simple myopia: Clinical treatment I

• Age:– Children < 2 years of age: hypercorrect by 1-2 D– Children up to 5-years-old (pre-schoolers):

hypercorrect by 0,5-1 D– From 6 to 40 years of age: avoid hypercorrections.

Evaluate:• Visual needs• Binocularity

– > 40-years-old: Precaution if he/she has never had a myopic Rx before

Simple myopia: Clinical treatment II

• Anisometropia:– Up to 8-10 years of age: try to prescribe for

the anisometropia– > 10 -12 years of age: prudence in the

prescription. Possible existence of monovision

Simple myopia: Clinical treatment III

• Binocularity:– Exodeviations: Total Rx for general use.

• In young subjects with exotropia: evaluate a possible slight hypercorrection.

– Endodeviations: avoid hypercorrections. • In NV try a slight hypocorrection

MYOPIA: MYOPIA DEGENERATIVE

Degenerative myopia: Generalities I

• Elevated myopia associated to pathological degenerative changes mainly in the posterior segment of the eye

• Abnormally large axial longitude• Ocular complications increase with age• Frequent cause of legal blindness

Degenerative myopia: Generalities II

• Etiology/risk factors:– Family history– Prematurity and low weight– Albinism– Mental retardation– Certain ocular pathologies

• Age of beginning:– 0-5 years of age: 31%– 6-11 years of age: 61%– 12 or more years of age : 8%

Degenerative myopia: Generalities III

• Symptoms: VA in DV, even with the best refraction:

• From problems in the posterior segment• Minifying effect of the lenses (-)

– Good VA in NV but at reduced distances– Discomfort with the glasses:

• Peripheral distortion• Weight• Chromatic aberration• Minification of the environment

Degenerative myopia: Clinical exam

• Signs:– Occasionaly exophthalmos– VA with the best refraction– More negative retinoscopy than the subjective– Vertex distance critical during the subjective– Anterior segment:

• Flatter and thinner cornea• Mydriasis• Deep anterior chamber

– Posterior segment: relationship cup/disc (in the ophthalmoscopy)• Myopic cone• Posterior staphyloma• Etc.

Degenerative myopia: Clinical treatment

• Avoid hypercorrections• If prescribing glasses: control the vertex

distance• Importance of prismatic effects in

secondary sight positions• Contact lenses:

– Less distorted vision– More accomodative demand in NV

MYOPIA: PSEUDOMYOPIA

Pseudomyopia: Generalities I

• Value of the subjective exam is more negative than the that of the retinoscopy

• Possible spasm of the Ciliary muscle• Do not confuse pseudomyopia with

myopic hypercorrection

Pseudomyopia: Generalities II

• Etiology:– Spasm of the Ciliary muscle after tasks in

NV– Exodeviations– Effects of medication– Inadequate work conditions in NV

• Symptoms: VA in DV (constant or intermittent)– Asthenopia in NV

Pseudomyopia: Clinical exam I

• VA in DV• Retinoscopy:

– Can fluctuate

• Subjective:– More negative than in the retinoscopy– The VA does not justify the refractive changes

• Accomodation:– With the Rx of the subjective it can seem like

the amplitude of accomodation is reduced

Pseudomyopia: Clinical exam II

• Binocularity:– Can be associated with exodeviations

(secondary condition pseudomyopia)– Can be associatated with endodeviations

(primary condition pseudomyopia)

Pseudomyopia: Clinical treatment

• Treatment:– Negative minimum– If prescription: use mainly in DV– Norms of visual hygiene– Visual exercises to relax accomodation

MYOPIA: NOCTURNAL MYOPIA

Nocturnal myopia: Generalities

• Diminishment of VA in conditions of poor illumination that improves with contact lenses

• Etiology:– Spherical aberration– Dark focus of the accomodation

• Detection depends on the subject’s symptomology

Nocturnal myopia: Clinical treatment

• Specific Rx for nocturnal activities– Tends to be sufficient with a prescription of -

0,75 or -1,00 D

MYOPIA: CASES

Myopia: case 1-I

• MT, 13-years-old. Student.• MC: Revision. Occasionally notes that

he/she does not see well in DV• PH: Has never worn glasses. It is his/her

first visual revision (previous check-ups by the pediatrician). No illnesses or ingestions of medication.

• FH: Father and older brother are myopes. Maternal grandmother has cataracts.

Myopia: case 1-II

• Normal VA in DV and NV:– RE: 20/30+; NV: 20/20– LE: 20/25; NV: 20/20

• Binocularity in habitual conditions:– Cover test:

• DV: ORTHO• NV: Low endophoria

– Promixal convergence: 6/10cm

Myopia: case 1-III

• Retinoscopy:– RE: -0,50-0,50x90º– LE: -50x90º

• Subjective DV and VA:– RE: -0,50-0,25x75º; VA: 20/20+

– LE: -0,50x100º; VA: 20/20+

• Habitual amplitude of accomodation:– RE: 8cm≈12,5D– LE: 8cm≈12,5D

• Ocular health tests: within normal limits

Myopia: case 1-IV

• Complete diagnostic of the case• Treatment proposed and plan of

revisions• Possible evolution of the condition

Myopia: case 1-V

• Complete diagnostic of the case– Low inverse astigmatism in both eyes– Low myopia in RE– Endophoric tendency in NV– The rest of the tests are within normal limits

Myopia: case 1-VI

• Treatment proposed. There are two possibilities:– Option A:

• Do not prescribe glasses• Recommend sitting as close as possible to the

board in class• Recommend rules of visual hygiene: postures and

work distance• Explain the condition and desired conduct to the

patient• Revision in 3-4 months

Myopia: case 1-VII

• Treatment proposed. There are two possibilities:– Option B:

• Prescribe glasses: RE: -0,50-0,25x75º; LE: -0,50x100º

• Exclusive use for DV. In class when necessary to in order to pay attention to the board.

• Do not use the glasses while studying in NV• Recommend standards for visual hygiene: postures

and work distance• Explain the condition and the desired conduct to the

patient• Revision in 4-6 months

Myopia: case 1-VIII

• Possible evolution of the condition:– Progression of the myopia

Myopia: case 2-I

• SE, 23 years of age. Salesman.• MC: notes that he/she does not see will

in DV, mainly while driving.• PH: Has worn general use glasses for 10

years. The most recent pair are three-years-old. No illnesses or ingestion of medication.

• FH: Irrevelant.

Myopia: case 2-II

• Rx and VA are habitual in DV and NV:– RE: -2,25; VADV: 20/25-; VANV: 20/20

– LE: -1,75-0,50x10º; VADV:20/30+; VANV: 20/20

• Binocularity in habitual conditions:– Cover test:

• DV: Ortho• NV: Low exophoria

– Proximal convergence: up to the nose

Myopia: case 2-III

• Retinoscopy:– RE: -2,75-0,25x180º– LE: -2,25-0,50x180º

• Subjective DV and VA:– RE: -2,50-0,25x15º; VA: 20/20+

– LE: -2,25-0,50x15º; VA: 20/20+

• Habitual amplitude of accomodation:– RE: 9cm≈11D– LE: 9cm≈11D

• Ocular health tests: within normal limits

Myopia: case 2-IV

• Complete diagnostic of the case• Treatment proposed and a plan of

revisions• Possible evolution of the condition

Myopia: case 2-V

• Complete diagnostic of the case– Simple myopia low in AO– Low, direct astigmatism in both eyes– Exphoric tendency in NV– The rest of the tests within normal limits

Myopia: case 2-VI

• Treatment proposed:– Prescribe new glasses:

• RE: -2,50-0,25x15º• LE: -2,25-0,50x15º

– For general use– Explain the change made– New check-up in 2 years or before if new

symptoms appear

Myopia: case 2-VII

• Possible evolution of the condition:– Significant refractive changes are not

expected until the age of prebyopia

MYOPIA: BIBLIOGRAPHY

Myopia: bibliography

• Amos JF. Diagnosis and management in vision care. Butterworth-Heinemann, 1987

• Milder B, Rubin ML. The fine art of prescribing glasses. (2nd edition), Triad Publishing company, 1991.

• Grosvenor T. Flom MC. Refractive anomalies. Research and clinical applications. Butterworth-Heinemann, 1991

• Brookman KE. Refractive management of ametropia. Butterworth-Heinemann, 1996

• Werner DL, Press LJ. Clinical pearls in refractive care. Butterworth-Heinemann, 2002

Myopia: Bibliography

• http://www.wrongdiagnosis.com/r/refractive_eye_disorders/intro.htm

• http://www.nlm.nih.gov/medlineplus/ency/article/001023.htm

• http://www.tarso.com/Miopia.html