myopia 1.pptx Ophthalmology MBBS 3rd year

Myopia (nearsightedness) is a common condition that’s usually diagnosed before age 20. It affects your distance vision — you can see objects that are near, but you have trouble viewing objects that are farther away like grocery store aisle markers or road signs. Myopia treatments include glasses, contact lenses or surgery.

1. myopia

2. Myopia or shortsightedness is a type of refractive error in which parallel rays of light coming from infinity are focused in front of the retina when accommodation is at rest .

3. ETIOLOGY Etiologically myopia may be of following types: 1 . Axial myopia results from increase in anteroposterior length of the eyeball. It is the commonest form. One mm increase in axial length results in-3D of myopia. 2. Curvatural myopia occurs due to increased curvature of the cornea, lens or both. One mm decrease in radium ofcurvature of cornea results -6D of myopia. 3. Positional myopia is produced by anterior placement of crystalline lens in the eye. 4. Index myopia results from increase in the refractive index of crystalline lens associated with nuclear sclerosis. 5. Myopia due to excessive accommodation occurs in patients with spasm of accommodation.

4. GRADING OF MYOPIA American Optometric Association (AOA) has defined three grades of myopia: Low myopia, when the error is ≤ -3D. Moderate myopia, when the error is between-3D to -6D. . High myopia, when the error is ≥ -6D.

5. CLINICAL VARIETIES OF MYOPIA CONGENITAL MYOPIA SIMPLE OR DEVELOPMENTAL MYOPIA PATHOLOGICAL OR DEGENERATIVE MYOPIA SECONDARY MYOPIA

6. CONGENITAL MYOPIA • Present since birth, the congenital myopia, is usually diagnosed by the age of 2-3 years. • Anisometropia is usually present, hence most of the time the error is unilateral. Rarely, it may be bilateral. • High degree of error, about 8 to 10D, is usually present, which mostly remains constant. • Convergent squint may develop in order to preferentially see clear at its far point (which is about 10- 12cm). .

7. • Associations may include other congenital anomalies such as cataract, microphthalmos , aniridia , megalocornea , and congenital separation of retina. •Early correction of congenital myopia is desirable

8. SIMPLE MYOPIA :- Introduction Also called as developmental myopia or school myopia Considered as a physiological error not associated with disease of eye Age of onset : 5-15 years

9. Etiology Mechanism of development : It results from normal biological variation in the development of eye : M ay or may not be genetically determined Axial type of simple myopia : Due to p hysiological variation in the length of the eyeball : As sociated with precocious neurological growth duringchildhood Curvatural type of simple myopia : Considered to be due to underdevelopment of the eyeball

10. Predisposing/precipitating factors Role of genetics :- Genetics plays some role in the biological variation of the development of eye Theory of excessive near work in childhood :- It is being believed that myopia is aggravated by close work, watching television, smart phones, computer and other VDUs. Limited outdoor activity and not using proper glasses, also contribute towards progression of myopia . Role of diet in early childhood has also been reported without any conclusive results

11. Clinical features Symptoms Poor vision for distance (short-sightedness) Asthenopic symptoms : Eye strain and headache Half shutting of eyes Signs Prominent eyeballs Anterior chamber is slightly deeper than normal . Pupils are somewhat large and a bit sluggishly reacting Fundus is normal rarely temporal myopic crescent may be seen Magnitude and progression: Simple myopia usually occurs between 5 and 15 years of age and it keeps on increasing till about 21 years of age at a rate of about -0.5 + 0.30 every year. Exophoria may occur in some patients due to imbalance between accommodative efforts and convergence DIAGNOSIS :- is confirmed by clinical refraction

12. Pathological myopia A rapidly progressive error which starts in childhood at 5-10 yrs of age and results in high myopia (greater than or equal to - 6D during early adult life which is usually with degenerative changes in the eye. Less common Etiology 1. Role of heredity . -)Familial, in most of the cases. -)Race. More common in certain races like Chinese, Japanese, Arabs and Jews, uncommon among Negroes, Nubians and Sudanese. -) Sex. More common in women than men. -) Genetic. Autosomal dominant pathological myopia has been linked to genes 18p11.31 and 12q21.23. -) Sex-linked, recessive inherited disorder status is being given to high myopia (>6D). -) Heredity-linked growth of retina is presumed to be determinant in development of myopia. The sclera due to its distensibility follows the retinal growth but the choroid undergoes degeneration due to stretching, which in turn causes degeneration of retina. 2. Role of general growth process The factors (such as nutritional indifferent general health) which affect the general growth process will also influence the progress of myopia.

13. Clinical Features Symptoms 1.Defective vision. There is considerable failure in visual function as the error is usually high. Further, due to progressive degenerative changes, an uncorrectable loss of vision may occur. 2.Floaters, i.e., floating black opacities in front of the eyes are often complained by many patients. These occur due to degenerated liquefied vitreous. 3.Difficulty in night vision may be complained by very high myopes having marked degenerative changes 4.Photophobia, usually occurs due to more light entering the eye owing to large pupils. Most people squeeze the eyes ( palpebral aperture) to reduce the photophobia and improve visual acuity by pinhole effect. 5.Flashes of lights may be reported occasionally.

14. Signs 1. Prominent eyeballs The eyes are often prominent, appearing elongated and even simulating an exophthalmos , especially in unilateral cases. The elongation of the eyeball mainly affects the posterior pole and surrounding area; the part of the eye anterior to the equator may be normal. 2.Cornea is large. 3.Anterior chamber is deep. 4.Pupils are slightly large and react sluggishly to light. 5.Magnitude of refractive error increases rapidly and finally may vary from - 10D to -40D.

15. 6. Fundus examination reveals following characteristic signs: a . Optic disc appears large and pale and at its temporal edge a characteristic myopic crescent is present

16. b . Degenerative changes in retina and choroid are common in progressive myopia These are characterized by: 1) Chorioretinal atrophic patches at the macula with a little heaping up of pigment around them. 2) Foster-Fuchs' spot (dark red circular patch due to sub-retinal neovascularization and choroidal haemorrhage) may be present at the macula. 3) Cystoid degeneration may be seen at the periphery. 4)Lattice degeneration and or snail track lesions with or without retinal holes/tears may be present; which later may be complicated by retinal detachment. 5)Total retinal atrophy , particularly in the central area may occur in an advanced case.

17. c . Posterior staphyloma due to ectasia of sclera at posterior pole may be apparent as an excavation with the vessels bending backward over its margins. d . Degenerative changes in vitreous include: liquefaction, vitreous opacities, and posterior vitreous detachment (PVD) appearing as Weiss' reflex. 7.Visual fields may show contraction and in some cases ring scotoma may be seen. 8.ERG may reveal subnormal electroretinogram due to chorioretinal atrophy. Complications Retinal detachment, Complicated cataract, Vitreous haemorrhage, Choroidal haemorrhage, Strabismus fixus convergence, and Primary open angle glaucoma, not a complication, but is a reported association.

18. SECONDARY MYOPIA Secondary myopia is caused by other eye diseases which are not recognised as population risk factors. It is off 7 types . [1] Index myopia Nuclear sclerosis cause increase in refractive index.near vision of such patients is corrected and called second light. Incipient cataract also produce this. Myopia in diabetics is due to increased glucose levels and decrease in refractive index. [2] C urvatural secondary myopia Corneal-occur in keratoconus and corneal ectasis . Lenticular -occur in lenticonus anterior or posterior

19. [3] P ositional Occur in anterior subluxation of lens [4] C onsecutive -occur in surgical overcorrection of hypermetropia and pseudoplakia [5] Pseudomyopia - due to spasm of accomodation . [6] Myopia of prematurity -without retinopathy or following retinopathy treatment. [7] Drug induced -occur with cholinergics , steroids, sulphonamide.

20. Treatment of myopia Treatment modalities [1] Optical treatment of myopia ￱prescription of appropriate concave lenses ￱ convave lenses are prescribed as spectacles and contact lenses ￱contact lenses are particularly justified in case of high myopia as they avoid peripheral distortion and minification produced by strong concave spectacle lens [2 ] Surgical treatment : Has become popular nowadays [3] Low Vision Aids : indicated in patients with progressive myopia having advanced degenerative changes where vision cannot be obtained with spectacles and contact lenses

21. Surgical treatment of myopia A .Cornea based procedure: Includes . Radial keratotomy . Laser ablation corneal procedures . Refractive lenticule extraction . Intercorneal ring implantation . Orthokeratology B . Lens based procedures . Refractive lens exchange . Phakic refractive lens or implantable contact lens

22. THANKYOU