Lecture 1 Visual functions in different age Lecture 1 Visual functions in different age. Main diagnostic criteria in ophthalmology. Blidness. Term „norm” & „pathology” of visual organ. Refraction. Types of clinical refraction. Progressive myopia. Prophylaxis, methods of surgical and conservative treatment. Presbyopia. Lecture is delivered by Ph. D., assistant of professor Tabalyuk T.A.

Visual organ consists from: 1) peripheral part – eyeball with ocular adnexa; 2) guiding pathway – optic nerve, chiasm, optic tract; 3) undercortex centers – lateral geniculare nucleus and optic radiation; 4) higher visual centers in the occipital cortex.

Structure of Visual Analisator 1 - retina, 2 - optic nerve (non-crossed fibers), 3 -  optic nerve (crossed fibers), 4 - optic tract, 5 -  lateral geniculare nucleus, 6 - radiatio optici, 7 - lobus opticus

OPTICAL SYSTEM of the EYE: EYEBALL I. External (structural) layer – cornea & sclera; II. Middle (vascular) layer – iris, ciliary body & choroid; III. Internal layer – retina. Internal nucleus of the eye includes: lens, vitreous & aqueous humor, which fill in eye chambers. The eyes lie within two bony cavities, or orbits. OCULAR ADNEXA : Lacrimal gland & excretory system Oculomotor apparatus Eyelids Conjunctiva OPTICAL SYSTEM of the EYE: Cornea Aqueous humor Lens Vitreous

VISUAL FUNCTIONS: Light sensitivity Field of vision Visual acuity Peripheral vision (rods are response) includes: Light sensitivity Field of vision Central vision (cones are response) includes: Visual acuity Colour vision

Light sensitivity Eye adaptation to light lasts till 1 minute. Eye adaptation to dark lasts till 1 hour. Adaptometr is a special equipment with the help of which we can measure dark adaptation of the human eye. The investigation durates 1 hour. Hemeralopia is a light sensitivity disorder. Functional hemeralopia is usually caused by hypovitamonosis A. Symptomatic hemeralopia is an index of rods condition and may be a symptom of retinitis pigmentosa, optic neuritis or glaucoma.

Field of vision is a space which is seen by non-moving eye (one eye, not both). Perimetry – projection of visual field on spherical concave space, which is concetric to retina. Left picture – ancient perimetr of Ferster Right picture – modern automatic computerized spheroperimetr

Campimetry is a projection of visual field on a plane This method is useful to reveal and measure phisiological scotoma – blind spot – projection in a space optic disc. Usually blind spot is found in temporal part of visual field 12-18 degrees of point of fixation (controposite nasal location of optic disc). Its vertical size - 8-9 degrees (10-11 sm), its horizontal size – 5-7 degrees (8-9 sm).

Normal bounders of visual field for objects of different colour

Visual field defects 1.Narroving of visual field bounders: concetric (retinitis pigmentosa, optic atrophy, final glaucoma) local (usual hemianopsia : homonim - dextra or sinistra & heteronim - binasal or bitemporal) 2. Patch loosing of visual field - scotoma: positive (with complaints) & negative (without complaints) absolute & relative physiological & pathological I.e. blind spot is physiological, absolute & negative scotoma

Visual acuity Visual acuity is measured in relative units. visus=d/D, where d-distance of investigation; D-distance, from each normal eye can definite signs of this line (is written in the left of each line of Sivtcev table). For example, the person reads first line of Sivtcev table from 5 m. Normal eye definites the signs of this line from 50 m. So, visus=5 m/50 m=0,1. If the person does not see optotypes of first line of Sivtcev table from 5 m, we ask him to come more near to the table. For example, the person reads first line of Sivtcev table from 3 m. Normal eye definites the signs of this line from 50 m. So, visus=3 m/50 m=0,06. If the person does not see optotypes of first line of Sivtcev table even from 0,5 m, we project the light to his or her eye from different direcrion. If the person gives correct answers, then his visus=1/∞ pr.l.certa. If the person see light, but gives not correct answers even in one direction, then his visus=1/∞ pr.l.incerta. If the person does not see light, then his visus=0. In such cases usually direct light reaction of pupil is absent & during objective measuring of visual acuity with the help of nystagmoaparat optokinetic nystagmus is absent.

VISUAL ACUITY TEST (UKRAINIAN & FOREIGN ONE) Left picture – Snellen chart Right picture – Sivtcev table

Visual acuity transcription 20 feet equivalent (USA) 6 meter equivalent (Great Britain) 5 meter equivalent (Ukraine) 20/20 6/6 1,0 20/25 6/7.5 0,8 20/40 6/12 0,5 20/60 6/18 0,3 20/200 6/60 0,1

Normal data of visual acuity in children Newborns – 0,005; 4 months – 0,01 1 year – 0,1-0,3; 2 years – 0,2-0,5; 3 years – 0,3-0,6; 4 years – 0,4-0,7; 5 years – 0,5-0,9; 6 years –0,7-1,0; 7-15 years – 1,0

Colour vision Polichromatic Rabkins tables are used for investigation Normal colour vision according to this method is called normal trichromasia

Colour vision disorders: Congenital usually bilateral Aquired usually monolateral Defect of one of three main colours is called dichromasia White & black perceprion is called monochromasia Anomal perception of red – protanomaly Anomal perception of green – deyteranomaly Anomal perception of blue - tritanomaly

PHYSICAL REFRACTION of the EYE: average refractive power of the eye is approximetly 60 D individual indices fluctuate from 52 till 71 D Average refractive power of optical mediums of the eye: Cornea – 40 D Lens - 19-20 D Aqueous humor & vitreous – less then 1 D In sum – 60 D

EMMETROPIA & AMMETROPIA: CLINICAL REFRACTION of the EYE: correlation between refractive power of the eye & its length EMMETROPIA & AMMETROPIA: MYOPIA HYPERMETROPIA ASTIGMATISM

Emmetropia (E or Em) – refractive power of the eye corresponds with its length, thus main focus is located on retina Ammetropia – refractive errow, abnormal correlation between refractive power & length of the eye: Myopia (M or My) – main focus is before retina due to incresed refractive power or length of the eye Hypermetropia (H or Hy) - main focus is behind retina due to decresed refractive power or length of the eye Astigmatism – different refractive power in two perpendicular planes. Combination of different clinical refraction or different degrees of one type of clinical refraction in one eye is usually named astigmatism.

Myopia is subdivided into: Light degree – till minus 2,75 D; Middle degree – from minus 3,0 till 5,75 D; High degree – minus 6,0 D and more Hypermetropia is subdivided into: Light degree – till plus 1,75 D; Middle degree – from plus 2,0 till 4,75 D; High degree – plus 5,0 D and more Anisometropia is different refraction of both eyes more then 1,0 dptr

TYPES of ASTIGMATISM: 1. Simple – combination of emmetropia in one meridian & ammetropia in perpendicular one. A. Simple myopic - combination of emmetropia & myopia in two perpendicular planes; B. Simple hypermetropic - combination of emmetropia & hypermetropia in two perpendicular planes. 2. Complex – combination of different degrees of one type of ammetropia in two meridians. A. Complex myopic - combination of different degrees of myopia in two perpendicular planes; B. Comlex hypermetropic - combination of different degrees of hypermetropia in two perpendicular planes. 3. Mixt – combination of myopia & hypermetropia in perpendicular planes of one eye. II. 1. Direct – refractive power of vertical meridian is stronger then horizontal one 2. Indirect - refractive power of horizontal meridian is stronger then vertical one III. 1. Regular - refractive power of hole meridian is the same 2. Irregular - refractive power in one meridian is different due to corneal diseases, i.e. keratoconus, scars etc.

METHODS of MEASURING the REFRACTION I. Objective methods: sciascopy or retinoscopy refractometry autorefractometry ophtalmometry II. Subjective method according to improving the visual acuity with trial glasses

Retinoscopy, refractometry, autorefractometry

Ophthalmometry, corneal topography

NORMAL DEVELOPMENT of REFRACTION in CHILDREN Newborns – Hm 3,0-5,0 dptr; 1 year – Hm 3,5 dptr; 2 years – Hm 3,0 dptr; 3 years – Hm 2,5 dptr; 4 years – Hm 2,0 dptr; 5 years – Hm 1,5 dptr; 6 years – Hm 1,0 dptr; 7-8 years – Hm 0,75 dptr; 9-15 years – Hm 0,5 dptr;

EXAMPLES: 1. The results of refractometry of both eyes: 90 degrees –My (-) 5,0 dptr; 180 degrees – My (-) 5,0 dptr It's middle degree myopia OU. 2. The results of refractometry of both eyes: 90 degrees – Hm (+) 2,0 dptr; 180 degrees – Hm (+) 2,0 dptr It's middle degree hypermetropia OU. Pay attention for patients' age! It may be physiological refraction! 3. The results of refractometry of right eye: 180 degrees – Em It's simple myopic direct astigmatism OD.

EXAMPLES: 4. The results of refractometry of left eye: 90 degrees – Hm (+) 5,0 dptr; 180 degrees – Hm (+) 10, 0 dptr It's complex hypermetropic indirect astigmatism OS. 5. The results of refractometry of both eyes: 90 degrees – My (-) 2,0 dptr; 180 degrees – Hm (+) 3,0 dptr It's mixt direct astigmatism OU. 6. The results of refractometry of right eye: 90 degrees –My (-) 2,0 dptr; 180 degrees – My (-) 2,0 dptr The results of refractometry of left eye: 180 degrees – Hm (+) 5, 0 dptr It's anisometropia. Light degree myopia OD. High degree hyperopia OS.

METHODS of AMMETROPIA CORRECTION: GLASSES CONTACT LENSES SURGICAL, i.e. EXIMER LASER ORTHOKERATOLOGY in light & middle myopia

Glasses is the most simple, most ancient method of correction, but not always the most effective Sph concave for myopia Sph convex for hyperopia Cyl for simple astigmatism Sph-cyl for complex & mixt astigmatism

SOFT & HARD CONTACT LENS

Irregular cornea, i.e. in keratoconus Anisometropia Contact lenses give the better & more natural vision, but the patient have to be under a special doctors control Medical indications for contact correction: High myopia High astigmatism Aphakia Irregular cornea, i.e. in keratoconus Anisometropia

Lasik surgery – changing of cornea shape

Implantation of phakic intraocular lenses in high myopia & astigmatism

ORTHOKERATOLOGY – changing of corneal shape in light & middle myopia with the help of special contact lenses to stop myopia progression in children & in cases when laser surgery is contrindicated (i.e. thin cornea)

Accommodation -   adjustment of the eye for vision in different distances . In short distances - ciliary muscle contracts – zonula ciliaris relax – lens becomes more convex – refractive power of lens increases In long distances - ciliary muscle relaxes – tensio of zonula ciliaris increases – lens becomes more concave – refractive power of lens decreases

PRESBYOPIA – age loosing of accommodation To correct it special multifocal glasses (progressive) or glasses for near distance are prescribed. Approximetly: 40 years – sph convex (+) 1,0 dptr 45 years – sph convex (+) 1,5 dptr 50 years – sph convex (+) 2,0 dptr 55 years – sph convex (+) 2,5 dptr 60 years – sph convex (+) 3,0 dptr over 60 years – sph convex (+) 3,5 dptr

STRABISMUS

HIRSHBERG TEST is used to determine angle of strabismus

Differentiation of neurologycal & ophthalmological srabismus Paralytic (nonconcominant) strabismus Concominant (nonparalytic) strabismus Decreasing or absence of eye movements in any direction Full amount of eye movements Primary & secondary angle of strabismus are different Primary & secondary angle of strabismus are equal Diplopia Diplopia is absebt

Types of concominant srabismus Accommodative strabismus Nonaccommodative strabismus Angle of srabismus is visible only for near distance (if it is esotropia) or only for far distance (if it is exotropia) Angle of srabismus is present constantly (for far & near distances) Using of cycloplegic agents (S. atropini, Mydriacili or Tropicamide) corect angle of srabismus (if it is esotropia) or increases it (if it is exotropia) Using of cycloplegic agents (S. atropini, Mydriacili or Tropicamide) does not influence on angle of srabismus Glasses corect angle of srabismus: sph convex if it is esotropia sph concave if it is exotropia Glasses does not influence on angle of srabismus

TREATMENT of NONACCOMMODATIVE STRABISMUS only SURGICAL Recession (weakening of eye muscle) & Resection (strenthening of eye muscle)

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