HYPERMETROPIA , basics of hypermetropia.

Far-sightedness, also known as long-sightedness, hypermetropia, and hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred. This blur is due to incoming light being focused behind, instead of on, the retina due to insufficient accommodation by the lens.[6] Minor hypermetropia in young patients is usually corrected by their accommodation, without any defects in vision.[2] But, due to this accommodative effort for distant vision, people may complain of eye strain during prolonged reading.[2][7] If the hypermetropia is high, there will be defective vision for both distance and near.[2] People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus.[3] Newborns are almost invariably hypermetropic, but it gradually decreases as the newborn gets older.[6]

There are many causes for this condition. It may occur when the axial length of eyeball is too short or if the lens or cornea is flatter than normal.[2] Changes in refractive index of lens, alterations in position of the lens or absence of lens are the other main causes.[2] Risk factors include a family history of the condition, diabetes, certain medications, and tumors around the eye.[5][4] It is a type of refractive error.[5] Diagnosis is based on an eye exam.[5]

1. REFRACTIVE ERRORS OF EYE Presented by : Dr MOHIT KUMAR JHA Resident ophthalmology

2. INTRODUCTION Refractive error is the common cause of low vision in both children and adults it is due to the failure of eyes to correctly focused the light rays from an object directly onto the retinal plane the resultant image seen appears blur and the refractive correction is required to see the object clearly EMMETROPIA – having normal 6/6 vision AMETROPIA – having some form of refractive error.

3. TYPES OF AMETROPIA HYPERMETROPIA MYOPIA ASTIGMATISM

4. HYPERMETROPIA aka HYPEROPIA Parallel rays of light from an object at infinity are focused behind the retina , with accommodation at rest

5. Classification Based on Etiology  AXIAL HYPEROPIA CURVATURE HYPEROPIA INDEX HYPEROPIA POSITIONAL HYPEROPIA APHAKIA CONSECUTIVE HYPEROPIA

6. AXIAL HYPEROPIA Short axial length of eye ( physiological/pathological ) at birth eyes are hypermetropic by 2.5 D to 3D as age advances axial length increases adolescence Emmetropia attained Each 1mm shortening - 3D of hypermetropia. High hyperopia is seen in microphthalmos and nanophthalmos   (<20mm)

7. CURVATURE HYPEROPIA Curvature of cornea, lens or both is flatter than normal  Example:  Cornea is flat (Cornea Plana) - decrease in curvature/increase in radius of curvature increase in 1mm of radius of curvature produces 6D of hypermetropia. trauma

8. INDEX HYPEROPIA Decrease in effective refractivity of the lens. Physiologically - in old age ( cortical sclerosis ) Pathologically – in diabetes / cataract POSITIONAL HYPEROPIA Posteriorly placed crystalline lens (congenital / trauma) CONSECUTIVE HYPEROPIA Overcorrected Myopia / under corrected IOL

9. CLINICAL TYPES OF HYPEROPIA SIMPLE HYPEROPIA PATHOLOGICAL HYPEROPIA FUNCTIONAL HYPEROPIA

10. SIMPLE HYPEROPIA Commonest form results from normal biological variation in the development of the eyeball can be hereditary it includes Axial hypermetropia                       Curvatural hypermetropia

11. PATHOLOGICAL  HYPEROPIA CONGENITAL  : Microphthalmos , Microcornea , Congenital Posterior subluxation of lens , Congenital Aphakia ACQUIRED  :       - Senile Hyperopia         Δ Curvatural – Decrease in Curvature of outer lens fibers          Δ Index – Acquired cortical sclerosis       - Positional - Acquired Posterior Subluxation Of Lens       - Aphakia       - Consecutive      - Retrobulbar orbital tumors

12. FUNCTIONAL HYPEROPIA

13. Classification of extent of error LOW – Refractive Error of +2D or Less MODERATE – Refractive error of +2.25D to +5D HIGH – Refractive Error of +5.25D and more

14. ACCOMMODATION IN HYPEROPIA TOTAL HYPERMETROPIA LATENT HYPERMETROPIA : Overcome physiologically by the tone of                                                          ciliary muscle MANIFEST HYPERMETROPIA :          FACULTATIVE : Overcome by effort of accommodation           ABSOLUTE : Cannot be overcome by accommodation TOTAL HYPERMETROPIA = LATENT + MANIFEST   MANIFEST = FACULTATIVE + ABSOLUTE

15. NORMAL VARIATION WITH AGE 

16. AFTER 50 YEARS OF AGE Tendency to develop hypermetropia again it is due to two factors, both associated with lens outer cortical fibers have less curvature decreasing the converging power old age index of refraction of cortex increases and lengths become homogeneous decreasing the converging power index hypermetropia in early life unless the error is unusually large the accommodative power can correct it all after 65 all of the hypermetropia becomes absolute due to the loss of accommodation

17. CLINICAL PICTURE ASYMPTOMATIC  (<1D) - in young patient is corrected by mild accommodative effort ASTHENOPIC SYMPTOMS  (1-2D) -patients develops asthenopic symptoms due to sustained accommodative efforts  tiredness of the eyes frontal and frontotemporal headache Watering mild photophobia symptoms are aggravated as the day progresses and also by prolonged near vision use     

18. DEFECTIVE VISION WITH ASTHENOPIC SYMPTOMS 2-4D It is not corrected fully by accommodative efforts patients complain of defective vision, more for near distance associated asthenopic symptoms due to sustained accommodative efforts DEFECTIVE VISION ONLY >4D Patient usually do not accommodate, external epic symptoms are minimal managed defective vision for near and distance intermittent sudden blurring of vision may occur due to spasm of accommodation or temporary failure of ciliary muscle. desire of accommodation in excess of convergence lead to dissociation of muscle balance producing accommodative convergent squint

19. SIGNS Reduced visual equity size of eyeball may be normal or may appear small as a whole .A scan may reveal short antero-posterior length of the eyeball Cornea may be slightly smaller than normal maybe cornea plana anterior chamber is comparatively shallow since the eyeball is small and the size of the lens varies very little, and the angle is narrow (predisposition to angle closure glaucoma)

20. Fundus Examination Optic disk may appear small and hyperemic with                                             ill-defined margins and may mimic papillitis                                       (pseudo-papillitis) the vascular reflex may be accentuated and the vessels may show undue tortuosity and abnormal branchings foveal reflex may be situated at a greater distance from disk margin. it may cause large positive angle Kappa (producing apparent divergent squint) the retina as a whole may shine due to greater brilliance of light reflection (shot silk appearance)

21. Complications Recurrent styes, blepharitis or chalazion due to constant rubbing of the eye done to get relief from fatigue and tiredness Accommodative convergent squint may develop in children( aged  2-3 years)due to excessive use of accommodation Amblyopia may develop in some cases Anisometropic amblyopia (unilateral hypermetropia) Strabismic amblyopia Ametropic amblyopia (bilateral uncorrected high hyperopia) predisposition to develop primary angle closure glaucoma due to small size of eye and shallow AC

22. TREATMENT OPTICAL TREATMENT CONVEX ( PLUS ) LENSES SPECTACLES CONTACT LENSES 2 . SURGICAL TREATMENT 3 . VISUAL HYGIENE

23. OPTICAL TREATMENT Basic principle is to prescribe convex lenses , so that the light rays are brought to focus on retina.

24. TIPS FOR PRESCRIBING IN HYPEROPIA Total amount of hypermetropia should always be discovered under complete cycloplegia. total manifest refractive error when small ( <1D ) ,correction is given only if the patient is symptomatic. spherical correction given should be comfortably acceptable to the patient ,however astigmatism should be fully corrected. The highest plus number which gives maximum visual equity should be given.

25. OPTICAL CORRECTION IN CHILDREN Children younger than 4 years usually accept full cycloplegic measurement. once a child reaches the school age, consider reducing the plus power by about 1/3 , but the child should not accommodate more than 2.5 D continually for the distance. child may not accept the power prescribed . So, always first under correct that the child accepts comfortably ,gradually increase the correction at six months interval. if there is associated exophoria ,hypermetropia is corrected by 1-2D . in presence of accommodative convergent squint, full correction should be given in the first sitting. it is important to remember that hypermetropia may diminish with the growth of the child ,so refraction should be carried out every six months

26. The national consensus for minimum refractive correction in infants and young children.

27. SPECTACLES -   comfortable , safe and easy method . CONTACT LENSES  -    INDICATED IN UNILATERAL HYPEROPIA SHOULD BE PRESCRIBED ONCE THE PRESCRIPTION HAS BEEN STABILIZED Cosmetically better. increased field of vision. less magnification. elimination of abrasions and prismatic effect

28. SURGICAL OPTIONS CONDUCTIVE KERATOPLASTY / CORNEAL REFRACTIVE SX ( rarely done ) LASER THERMAL KERATOPLASTY – heat the cornea via laser -> contraction of collagen -> increase in curvature PHOTOREFRACTIVE KERATECTOMY – done using EXIMER LASER ,  direct laser ablation of corneal stroma after removal of corneal epithelium mechanically. HYPEROPIC LASIK -  it can correct upto 4D of hyperopia ,   anterior flap of cornea lifted with keratome and excimer laser is used to sculpt the stromal bed to change the refractive error of the eye. PHAKIC IOL`S REFRACTIVE LENS EXCHANGE

29. PROBLEM OF HYPEROPIC LASIK/PRK Need to wear glasses in future on account of hyperopia returning on a later date. Decrease in Best corrected visual acuity ( BCVA )

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