Optics
57
Optics Professor Damian Czepita Department of Ophthalmology Pomeranian Medical Academy Szczecin, Poland http:// sci.pam.szczecin.pl/
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Optics. Professor Damian Czepita Department of Ophthalmology Pomeranian Medical Academy Szczecin, Poland http://sci.pam.szczecin.pl/~czepita. EMMETROPIC EYE. Image: true, reversed, reduced Refraction: cornea 43,5 D lens 19,1 D aqueous humor boundary membrane of the vitreous - PowerPoint PPT Presentation
Transcript of Optics
Optics
Professor Damian Czepita Department of Ophthalmology
Pomeranian Medical Academy Szczecin, Poland
http://sci.pam.szczecin.pl/~czepita
EMMETROPIC EYE
• Image: true, reversed, reduced• Refraction:
cornea 43,5 D
lens 19,1 D
aqueous humor
boundary membrane of the vitreous
vitreous body
Total 58,5-64,2 D
NEAR AND FAR POINT
• Near point:
The closest situated point from where exiting rays of light are refracted on the retina.
• Far point:
The farthest situated point from where exiting rays of light are refracted on the retina.
RANGE AND AMPLITUDE OF ACCOMMODATION
• Range of accommodation:
The distance between the far and near point.
• Amplitude of accommodation:
The range of accommodation in D.
AGE, NEAR POINT,AMPLITUDE OF ACCOMODATION
• 10 years 7 cm 14 D
• 20 years 10 cm 10 D
• 30 years 14 cm 7 D
• 40 years 22 cm 4,5 D
• 50 years 50 cm 2 D
• 60 years 100 cm 1 D
• 70 years infinite 0 D
PRESBYOPIA
• After the 40th year of age:
Decrease in elasticity of fibers and capsules of the lens.
SENILE HYPEROPIA
• After the 60th year of age:
Decrease of the refractive index in eye tissues, especially in the cornea and the vitreous body.
READING GLASSES
• 40 years of age +1 D
• 50 years of age +2 D
• 60 years of age +3 D
CLASSIFICATION OF MYOPIA
• AXIAL - too long axis of the eye, normal strength of the optic system
• REFRACTIVE – normal length of the eye axis, too strong optic system
CLASSIFICATION OF MYOPIA
LOW < -4 D
MEDIUM -4 – -8 D
HIGH > -8 D
Country Area Age
(years)
Myopia (%)
Hyperopia (%)
Chile Urban 5-15 6.8 16.3
China Urban 5-15 35.1 0.8
China Rural 5-15 16.2 3.5
Country Area Age
(years)
Myopia (%)
Hyperopia (%)
India Urban 5-15 7.4 7.7
India Rural 7-15 4.1 0.8
Malaysia Urban 7-15 19.3 1.3
Country Area Age
(years)
Myopia (%)
Hyperopia (%)
Nepal Rural 5-15 1.2 1.4
Poland Urban/
Semirural
6-18 13.3 13.1
South Africa
Urban/
Semirural
5-15 2.9 1.8
0
5
10
15
20
25
30
35
6 7 8 9 10 11 12 13 14 15 16 17 18
OCCURRENCE OF MYOPIA
• Stickler syndrome
• Marfan’s syndrome
• Ehlers-Danlos syndrome
• Weill-Marchesani syndrome
• homocystinuria
OCCURRENCE OF MYOPIA
• McCune-Albright syndrome
• Kniest syndrome
• Down syndrome
• Prader-Will syndrome
• Noonan sydrome
OCCURRENCE OF MYOPIA
• Cohen syndrome
• Rubinstein-Taybi syndrome
• Cornelia de Lange syndrome
• fetal alcohol syndrome
• Knobloch syndrome
OCCURRENCE OF MYOPIA
• congenital night blindness
• deficiency of ornithine aminotransferase
• deficiency of prolidase
• premature infants
• lack of a sufficient amount of calcium, fluoride and selenium in food
READING OR WRITING VS. MYOPIAP <0,001
READING/
WRITING
MYOPIA
PRESENT
MYOPIA
ABSENT
TOTAL
< 2 H 6,44%
(n=93)
93,56%
(n=1351)
100%
(n=1444)
2-3,5 H 12,15%
(n=269)
87,85%
(n=1945)
100%
(n=2214)
> 3,5 H 16,77%
(n=360)
83,23%
(n=1787)
100%
(n=2147)
TOTAL 12,44%
(n=722)
87,56%
(n=5083)
100%
(n=5805)
COMPUTER VS. MYOPIAP < 0,01
COMPUTER MYOPIA
PRESENT
MYOPIA
ABSENT
TOTAL
< 0,8 H 11,45%
(n=392)
88,55%
(n=3033)
100%
(n=3425)
> 0,8 H 13,85%
(n=338)
86,15%
(n=2102)
100%
(n=2440)
TOTAL 12,45%
(n=730)
87,55%
(n=5135)
100%
(n=5865)
TELEVISION VS. MYOPIAP > 0,05
TV MYOPIA
PRESENT
MYOPIA
ABSENT
TOTAL
< 2 H 13,76%
(n=232)
86,24%
(n=1454)
100%
(n=1686)
2-2,5 H 11,46%
(n=237)
88,54%
(n=1831)
100%
(n=2068)
> 2,5 H 12,34%
(n=253)
87,66%
(n=1798)
100%
(n=2051)
TOTAL 12,44%
(n=722)
87,56%
(n=5083)
100%
(n=5805)
INHERITANCE OF MYOPIA
• MONOGENIC:
autosomal dominant
autosomal recessive
X-linked
• POLYGENIC:
< -6 - chromosome 1 ?
> -6 – chromosome 1-4, 7, 8, 10-12, 17, 18, 22
CHILDHOOD MYOPIA
• is the most often met form of myopia. It occurs before and during maturation.
PROCEDURES IN CHILDHOOD MYOPIA
• exercises in plus glasses when looking far away
• reading in prisms• temporary usage of spectacles• keeping hygiene of the visual work:
correct illumination, reading from a distance of 30 cm, doing breaks during visual work
PROGRESSIVE MYOPIA
• develops after birth to the 30-35 years of age. It is characterized by its fast course.
PROCEDURES IN PROGRESSIVE MYOPIA
• drugs sealing the vessels and improving circulation: Calcium, Extract vaccinium myrtillus, Pentoxifylline, Rutoside, Xantinol nicotinate
• biostimulating drugs: Aloe extract, Extract total eye, Peat bog extract, Placental extract, Sea slime extract
• vitamins: A, B1, B2, B6, B12, C, D, E, F, PP• diet with plenty of fresh fruits and vegetables
PROCEDURES IN PROGRESSIVE MYOPIA
• permanent usage of spectacles• keeping hygiene of the visual work: correct
illumination, reading from a distance of 30 cm, doing breaks during visual work
• laser treatment: photocoagulations of degenerative changes in the retina and choroidea
SUBSTANCES INHIBITING THE PROGRESS OF EXPERIMENTAL MYOPIA
• PIRENZEPINE - antagonist of the muscarinic M1 receptors,
• APOMORPHINE - unselective agonist of the dopamine receptors.
CLASSIFICATION OF HYPEROPIA
• AXIAL - too short axis of the eye, normal strength of the optic system
• REFRACTIVE - normal length of the eye axis, too low strength of the optic system
• PHYSIOLOGICAL < +3 D
0
10
20
30
40
50
60
70
80
90
6 7 8 9 10 11 12 13 14 15 16 17 18
ASTIGMATISM
• A refractive error, which causes rays of light passing through the refractive planes of the eye to be differently refracted.
ORIGINS OF ASTIGMATISM
• Corneal astigmatism:
deformation in the anterior and posterior surface of the cornea
• Lenticular astigmatism:
deformation in the anterior and posterior surface of the lens, decentralization of the lens, irregular refractive index of the lens
ORIGINS OF ASTIGMATISM
• Corneo-lenticular astigmatism
• Others - for examaple deformations of the posterior part of the eyeball
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
6 7 8 9 10 11 12 13 14 15 16 17 18
ANISOMETROPIA
• Different refractive errors in the left and right eye.
• AXIAL - different length of the eyeball
• REFRACTIVE - different strength of the eye’s optic system
LACK OF FUSION
• > +5 D
• > -6 D
OPTICAL ADVANTAGES OF CONTACT LENSES
• Are able to fully correct even very high refractive errors.
• Do not limit the visual field.
• Do not create oblique beam astigmatism.
• Do not create aniseikonia greater than 10%.
• Do not create micropsia in high myopia.
