1 OCULAR REFRACTION

2 Visual analyser performances Phisical status of refractive components (correct focus on the retina); Phisical status of refractive components (correct focus on the retina); Retinian neurons quality; Retinian neurons quality; Brain neurons quality. Brain neurons quality.

3 Ocuar refraction is defined by the anatomical components which contribute on light array optical modulation Ocuar refraction is defined by the anatomical components which contribute on light array optical modulation

4 transparent mediums lacrimal layer lacrimal layer cornea cornea aqueous humour aqueous humour lens lens vitrious vitrious

5 Ocular refraction static refraction static refraction dinamic refraction dinamic refraction

Subjects 1.Ametropia 2.Hyperopia 3.Myopia 4.Astigmatism 5.Anizometropia 6.Accomodation 7.Presbyopia 6

EMETROPIA emetropia is that optical condition in which there is no refraction error so that rays of parallel to the visual axis appear entering the eye are brought to a focus on the fovea centralis when no accommodation is used emetropia is that optical condition in which there is no refraction error so that rays of parallel to the visual axis appear entering the eye are brought to a focus on the fovea centralis when no accommodation is used 7

AMETROPIA classification spherical or stigmic disorders in which enter: spherical or stigmic disorders in which enter: myopia myopia hyperopia hyperopia 8

asferical or astigmic disorders in which we include astigmatisms: asferical or astigmic disorders in which we include astigmatisms: regular regular iregular iregular 9

HYPEROPIA refractive condition of the eye in which (with accommodation suspended) parallel rays of light are intercepted by the retina before coming to focus refractive condition of the eye in which (with accommodation suspended) parallel rays of light are intercepted by the retina before coming to focus 10

Clasification of hyperopia Axial = when the globe is too short to the amount of the refractive power present; Axial = when the globe is too short to the amount of the refractive power present; Refractive = when the power of the cornea and lens is inadequate for the length of the globe Refractive = when the power of the cornea and lens is inadequate for the length of the globe 11

Type of hyperopia Total hyperopia = amount of the hyperopia with all accommodation suspended (by using the cycloplegic drugs); Total hyperopia = amount of the hyperopia with all accommodation suspended (by using the cycloplegic drugs); Manifest hyperopia = is the maximum hyperopia that can be corrected with a convex lens when accommodation is active; Manifest hyperopia = is the maximum hyperopia that can be corrected with a convex lens when accommodation is active; Latent hyperopia = is the difference between total and manifest hyperopia. Latent hyperopia = is the difference between total and manifest hyperopia. 12

Signs and symptoms Visual acuity is reduced when accommodation is not able to fully substitute the hyperopia; Visual acuity is reduced when accommodation is not able to fully substitute the hyperopia; Vision is blurred, especially after near work; Vision is blurred, especially after near work; The increased of the accommodation may stimulate an excessive degree of convergence, manifested as a tendency of for the eyes to deviate inward (esodeviation); The increased of the accommodation may stimulate an excessive degree of convergence, manifested as a tendency of for the eyes to deviate inward (esodeviation); The cornea is smaller than normal, and even the globe itself may be smaller; The cornea is smaller than normal, and even the globe itself may be smaller; 13

Oftalmoscopy optic disk congestive, with indistinct margins and the absence of the physiologic cup (pseudopapiledema) optic disk congestive, with indistinct margins and the absence of the physiologic cup (pseudopapiledema) 14

Treatment convex lenses (glases or contact lenses) convex lenses (glases or contact lenses) corneal refractive surgery: corneal refractive surgery: Laser thermal keratoplasty Laser thermal keratoplasty Lamellar keratoplasty Lamellar keratoplasty Photorefractive keratectomy Photorefractive keratectomy Laser in situ keratomileusis (LASIK) Laser in situ keratomileusis (LASIK) phakic intraocular lenses using iris-claw IOL; phakic intraocular lenses using iris-claw IOL; clear lens extraction with posterior chamber lens implantation. clear lens extraction with posterior chamber lens implantation. 15

LASIK 16

MYOPIA optical condition in which rays of light entering the eye parallel to the visual axis come to focus in front of the retina optical condition in which rays of light entering the eye parallel to the visual axis come to focus in front of the retina 17

Clasification of myopia Axial = because the refractive power of the cornea and lens is too great for the length of the eye; Axial = because the refractive power of the cornea and lens is too great for the length of the eye; Refractive = because the eye is to long for the refractive power present Refractive = because the eye is to long for the refractive power present 18

physiologic myopia physiologic myopia refractive (lenticular myopia – is refractive myopia related to the lens power) refractive (lenticular myopia – is refractive myopia related to the lens power) axial axial pathologic or degenerative myopia – is axial myopia pathologic or degenerative myopia – is axial myopia 19

physiologic myopia is the most common type is the most common type onset usually between 5 and 10 years of age but may begin as late as 25 years age onset usually between 5 and 10 years of age but may begin as late as 25 years age gradually increase until the eye is fully grown about 18 years of age gradually increase until the eye is fully grown about 18 years of age seldom exceeds 6 diopters. seldom exceeds 6 diopters. 20

pathologic or degenerative myopia Symptoms decreased vision decreased vision axial length of the eye is excessive, primarily because of overgrowth of the posterior two thirds of the globe axial length of the eye is excessive, primarily because of overgrowth of the posterior two thirds of the globe 21

oftalmoscopy crescent of the optic disc that begins at the temporal side and progresses to surround the disc. crescent of the optic disc that begins at the temporal side and progresses to surround the disc. Staphyloma of the posterior pole. Staphyloma of the posterior pole. hyperpigmented spot in the macula (Fuchs spot). hyperpigmented spot in the macula (Fuchs spot). degeneration of the retinal pigment epithelium degeneration of the retinal pigment epithelium choroidal sclerosis. choroidal sclerosis. peripheral retinal thinning with lattice degeneration and retinal breaks. peripheral retinal thinning with lattice degeneration and retinal breaks. 22

Treatment is neutralized by concave lenses is neutralized by concave lenses contact lenses (in high myopia, anizometropia); highly fitted contact lenses may temporarily reduce the corneal curvature and thus may show an apparent decrease in myopia contact lenses (in high myopia, anizometropia); highly fitted contact lenses may temporarily reduce the corneal curvature and thus may show an apparent decrease in myopia 23

Refractive surgery radial keratotomy acts through peripheral radial incision that flatten the central cornea radial keratotomy acts through peripheral radial incision that flatten the central cornea photorefractive keratectomy (PRK) ablates tissue directly from central cornea. photorefractive keratectomy (PRK) ablates tissue directly from central cornea. laser in situ keratomileusis (LASIK) excimer application (PRK) after creation of a hinged flap laser in situ keratomileusis (LASIK) excimer application (PRK) after creation of a hinged flap posterior chamber phakic intraocular lens (implantable ocular lens) posterior chamber phakic intraocular lens (implantable ocular lens) intracorneal implants intracorneal implants 24

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For high myopia laser photocoagulation for symptomatic retinal breaks laser photocoagulation for symptomatic retinal breaks extrafoveal or juxtafoveal laser photocoagulation therapy extrafoveal or juxtafoveal laser photocoagulation therapy combination between LASIK and phakic intraocular lens = “BIOPTIC” combination between LASIK and phakic intraocular lens = “BIOPTIC” scleral enforcement to stop or to retard the progression of disease (controversial and under investigation scleral enforcement to stop or to retard the progression of disease (controversial and under investigation 26

ASTIGMATISM optical condition in which the refractive power of the eye is not the same in all meridians. optical condition in which the refractive power of the eye is not the same in all meridians. variation in the curvature of the cornea or lens at different meridians induces light rays focusing to more than one point. variation in the curvature of the cornea or lens at different meridians induces light rays focusing to more than one point. 27

Classifications irregular = when the meridian are not at right angle to each other irregular = when the meridian are not at right angle to each other regular = when the meridian of minimal and maximal refraction are at right angle to each other. Regular astigmatism can be: regular = when the meridian of minimal and maximal refraction are at right angle to each other. Regular astigmatism can be: with the rule – when the vertical meridian is steepest and a correcting plus cylinder should be placed at axis 90° with the rule – when the vertical meridian is steepest and a correcting plus cylinder should be placed at axis 90° against the rule – when the horizontal meridian is steepest and a correcting plus cylinder should be placed at axis 180° against the rule – when the horizontal meridian is steepest and a correcting plus cylinder should be placed at axis 180° oblique astigmatism – the principal meridian do not lie at or close to 90° and 180° oblique astigmatism – the principal meridian do not lie at or close to 90° and 180° 28

Classifications II simple: when one meridian is emetropic and other is ametropic (myopic and hypermetropic) simple: when one meridian is emetropic and other is ametropic (myopic and hypermetropic) composed: when both meridian are ametropic composed: when both meridian are ametropic myopic = both meridian are in front of the retina myopic = both meridian are in front of the retina hypermetropic = both meridian are intercepted by retina before coming to a focus hypermetropic = both meridian are intercepted by retina before coming to a focus mixed astigmatism: one meridian is myopic and other is hypermetropic mixed astigmatism: one meridian is myopic and other is hypermetropic 29

Classifications III congenital astigmatism congenital astigmatism acquired astigmatism: acquired astigmatism: surgical incision o the cornea surgical incision o the cornea trauma and scarring of the cornea trauma and scarring of the cornea tumors of the eyelid pressing upon the globe tumors of the eyelid pressing upon the globe 30

Pathogenic aspects parallel rays of light do not focus at a point. Each meridian has a focal line; the distance between these focal lines is the “interval of Sturm”. Between the focal lines, in the circle of least diffusion (conffusion), the diverging and converging tendency of the light rays is the same. In this area the image is clear enough to satisfy the patient parallel rays of light do not focus at a point. Each meridian has a focal line; the distance between these focal lines is the “interval of Sturm”. Between the focal lines, in the circle of least diffusion (conffusion), the diverging and converging tendency of the light rays is the same. In this area the image is clear enough to satisfy the patient 31

Symptoms and signs the image is not clear the image is not clear the accommodation is interfered the accommodation is interfered severe astigmatism may cause the optic disc to appear oval rather then near circular severe astigmatism may cause the optic disc to appear oval rather then near circular 32

Treatment Minor degree of astigmatism with good VA and without symptoms – correction is not indicated Minor degree of astigmatism with good VA and without symptoms – correction is not indicated Simple astigmatism – cylindrical lens placed in the meridian 90 degrees away from the axis of the ametropic meridian Simple astigmatism – cylindrical lens placed in the meridian 90 degrees away from the axis of the ametropic meridian Composed and mixed astigmatism – sphero-cylindric lenses (combination of a sphere and a cylinder -plus or minus- ) Composed and mixed astigmatism – sphero-cylindric lenses (combination of a sphere and a cylinder -plus or minus- ) 33

Hard contact lenses may be used to correct regular astigmatism and especially the irregular astigmatism Hard contact lenses may be used to correct regular astigmatism and especially the irregular astigmatism Surgery Surgery incisional surgery (relaxing incisions, block resection, compressive suture) is indicated in congenital regular astigmatism incisional surgery (relaxing incisions, block resection, compressive suture) is indicated in congenital regular astigmatism excisional surgery (excimer laser – PRK and LASIK) is recommended both in regular and irregular astigmatism excisional surgery (excimer laser – PRK and LASIK) is recommended both in regular and irregular astigmatism 34

ACCOMMODATION process by which the refractive power of the anterior lens segment increases so that a near object may be distinctly imaged upon the retina process by which the refractive power of the anterior lens segment increases so that a near object may be distinctly imaged upon the retina 35

complex reflex the stimulus is a blurred retinal image the stimulus is a blurred retinal image this is coming to brain this is coming to brain different area of the brain send order to the periphery different area of the brain send order to the periphery stimulation of the short ciliary branch of the oculomotor nerve constricts or relaxes the circular ciliary muscle stimulation of the short ciliary branch of the oculomotor nerve constricts or relaxes the circular ciliary muscle the eye almost instantly adjust to provide clear vision. the eye almost instantly adjust to provide clear vision. 36

For near vision contraction of the ciliary muscle causes contraction of the ciliary muscle causes the zonulae fibers to relax the zonulae fibers to relax then lens become more convex then lens become more convex the power is increased the power is increased the focal line is projected onto retina. the focal line is projected onto retina. 37

For long distance ciliary muscle relaxes ciliary muscle relaxes the zonulae fibers are pull and tensioned the zonulae fibers are pull and tensioned the convexity of the lens surface becomes minimal the convexity of the lens surface becomes minimal 38

amplitude of accommodation is distance between far point of the eye and nearest point at which the eye can maintain focus is distance between far point of the eye and nearest point at which the eye can maintain focus amplitude of accommodation is properly a monocular expression and is measured for each eye independently amplitude of accommodation is properly a monocular expression and is measured for each eye independently 39

accommodation associated reactions accommodation associated reactions convergence of the eyes convergence of the eyes pupilary constriction (miosis) pupilary constriction (miosis) 40

presbyopia with ageing with ageing lens capsule becomes less elastic lens capsule becomes less elastic nucleus becomes harder and less compressible nucleus becomes harder and less compressible this causes a gradual loss of accommodation this causes a gradual loss of accommodation 41

Symptomes inability to see near work distinctly inability to see near work distinctly patient places reding mater farther away from the eyes than previously patient places reding mater farther away from the eyes than previously ocular discomfort ocular discomfort 42

Evolution of accomodation 10 years age - 14Dpt. 10 years age - 14Dpt. 45 years age - 1Dpt., 45 years age - 1Dpt., 50 years age - 2Dpt., 50 years age - 2Dpt., 55 years age - 2.5Dpt., 55 years age - 2.5Dpt., 60 years age - 3Dpt., 60 years age - 3Dpt., 70 years age - 3.5Dpt 70 years age - 3.5Dpt 43

Special situations Myopic patients may compensate for presbyopia by removing the lens that corrects the distance vision. Myopic patients may compensate for presbyopia by removing the lens that corrects the distance vision. Presbyopia is aggravated in a hypermetropic patients if the lens that corrects the hypermetropia is removed Presbyopia is aggravated in a hypermetropic patients if the lens that corrects the hypermetropia is removed 44

Treatment convex lenses added to the distance correction; convex lenses added to the distance correction; Rules: Rules: the weakest possible convex to permit the individual to carry an vocational and avocational tasks; the weakest possible convex to permit the individual to carry an vocational and avocational tasks; if a subject requires lenses for distance, bifocal, trifocal or multifocal lenses should be worn as soon as are indicated if a subject requires lenses for distance, bifocal, trifocal or multifocal lenses should be worn as soon as are indicated 45

Convergence insufficiency (CI) the inability to maintain fusion at near as a result of a reduced amplitude of fusional convergence power. the inability to maintain fusion at near as a result of a reduced amplitude of fusional convergence power. Symptomes: Symptomes: eye discomfort eye discomfort headache headache blurred vision from reading or doing near work blurred vision from reading or doing near work Signs: Signs: reduced amplitude of accommodation reduced amplitude of accommodation exoforia exoforia 46

Accomodative insufficiency (AI) symptoms develops after min of reading (same as CI) but: symptoms develops after min of reading (same as CI) but: these patients have normal fusion capacities when a 4 diopters base in prism is placed in front of the eye while reding these patients have normal fusion capacities when a 4 diopters base in prism is placed in front of the eye while reding patients with AI benefit from reading glases patients with AI benefit from reading glases 47

Accomodative spasm (AS) inability to relax ciliary muscle (involuntary) inability to relax ciliary muscle (involuntary) is associated with stressful situations or functional nevroses is associated with stressful situations or functional nevroses Symptoms: Symptoms: bilateral blurred distance vision bilateral blurred distance vision headache, headache, fluctuating vision fluctuating vision Sings: Sings: cycloplegic refraction reveals hyperopia cycloplegic refraction reveals hyperopia abnormally close near point of focus abnormally close near point of focus miosis miosis 48

ANISOMETROPIA condition in which the refractive error of each eye is different condition in which the refractive error of each eye is different the different is more than 2 diopter there is a different in image size of the two eyes named anizeiconia the different is more than 2 diopter there is a different in image size of the two eyes named anizeiconia total amount of aniseiconia suported by patient must be less then 8% total amount of aniseiconia suported by patient must be less then 8% 49

several problems the difference of the power of the two lenses (bifocal lenses) induce a vertical prism, so that the image from each eye is on a different level (anisophoria); the difference of the power of the two lenses (bifocal lenses) induce a vertical prism, so that the image from each eye is on a different level (anisophoria); severe anisometropia may cause ambliopia because of the developing infant`s failure to use the eye with greater refractive error; severe anisometropia may cause ambliopia because of the developing infant`s failure to use the eye with greater refractive error; failure of central vision leads to strabismus, to absence of binocular vision or to deficiency of binocular vision failure of central vision leads to strabismus, to absence of binocular vision or to deficiency of binocular vision 50

Treatment must be done in the first year of life must be done in the first year of life must to equalize the size of the retinal image. must to equalize the size of the retinal image.When: the refractive difference between two eyes is smaller then 4D = full corection with glases the refractive difference between two eyes is smaller then 4D = full corection with glases this difference is greater we can use: this difference is greater we can use: contact lens corection contact lens corection specific surgical procedure for each type of refractive error specific surgical procedure for each type of refractive error 51