Hypermetropia

Hypermetropia Definition, Classification, epidemiology, signs and symptoms, complications, diagnosis and treatment.

1. HYPERMETROPIA Presented by- Shruti Dagar Amity University

2. Definition The term  hyperopia  comes from Greek  hyper  "over" and ōps  "sight "  When parallel rays of light come to a focus behind the retina, when accommodation is at rest is called Hypermetropia or Hyperopia . A person who has hyperopia is called hyperope . Hyperopia is also called ‘ longsightedness ’ or ‘farsightedness’.

3. Hypermetropia can be classified on the basis of: Anatomical Features (Simple) Degree Functional Pathological and Physiological Classification

4. Classification by anatomical features: Axial Hypermetropia:  If   antero -posterior diameter of the eye is less than the normal causes hypermetropia (Normal axial length is 24mm).  1mm shortening will cause +3D hypermetropia Curvature Hypermetropia:  Normal radius of curvature of cornea is 7.8mm anteriorly and 6.5mm posteriorly . Normal radius of curvature of lens is 10mm anteriorly and 6mm posteriorly. If the curvature of cornea and lens is less than the normal causes hypermetropia.  1mm flattening of curvature of cornea will cause +6D hypermetropia.

5. Index Hypermetropia:  If refractive index of cornea and lens is less than the normal causes hypermetropia.  Normal refractive index of cornea is 1.377 and lens is 1.41 at centre (Nucleus) & 1.386 at periphery (Cortex).  This condition may occur in diabetes under treatment . Displacement of lens:  If the lens is displaced back ward, it causes hypermetropia. Absence of lens:  Absence of crystalline lens causes hypermetropia . Usually lens is absence of the eye is called Aphakia . It may be surgical removal or posterior dislocation.

6. Classification by degree of hypermetropia : Low : +0.25 to + 3D May have good distance vision and near vision, but may have eyestrain and headaches with prolonged near work. Medium : +3.25 to + 5D Near vision blurred, but good distance vision. M ay have eyestrain and headaches. High : >+ 5D Both distance and near vision blurred( near vision is worse than distance vision.)

7. Classification by the action of accommodation : Also called Functional Hyperopia caused due to paralysis of accommodation. It is of following types: Latent Hypermetropia :  It is the amount of hypermetropia which is corrected normally by the normal tone of ciliary muscle. It is more in young children than in adults. It can be revealed only after cycloplegic drops are put in the eye. Manifest Hypermetropia : The strongest convex lens with which the patient can still maintain full distance vision 6/6 ,indicates manifest hypermetropia .  Is made up of two components - Facultative Hypermetropia and Absolute Hypermetropia

8. D ifferent type of manifest hypermetropia : Absolute Hypermetropia: It cannot be overcome by the effort of accommodation .  If the patient can not normally see 6/6 without a lens then the weakest convex lens that will allow him to read this line ,indicates absolute hypermetropia . Facultative Hypermetropia: It is that part of hypermetropia which can be corrected by the effort of accommodation. Facultative hypermetropia=Manifest hypermetropia -Absolute hypermetropia. Total Hypermetropia:  It can be find out by abolishing the tone of ciliary muscle by cycloplegics like atropine. Total hypermetropia=Latent hypermetropia+Manifest hypermetropia . (Facultative + Absolute).

9. Pathological Hypermetropia This is due to some underlying pathology Acquired : Corneal trauma, chalazion , chemical thermal burn, developing cataract, cyclopegic agents, albinism, aniridia , Lebers congenital amurosis . A reduction in axial length due to space-occupying lesion within the eye such as retinal detachment, CSR, orbital tumours,  retinal tumour   etc. Congenital : Micropthalmia , Nanaopthalmia , Cornea plana , lens plana , sclero cornea, anterior chamber cleavage syndrome, limbal dermoids . Physiological Hypermetropia It is normal biological variation. It includes axial and curvatural hypermetropia. It may be hereditary.

10. Epidemiology Age-Related Full term infants have mild hypermetropia Higher level of astigmatism are associated with moderate to high hypermetropia No gender difference Most full-term infants are mildly hyperopic. By age 6-9 months approximately 4-9% of infants are hyperopic and by age 12 months the prevalence is approximately 3.6%. Infants with moderate to high hyperopia (greater than +3.50D) are up to 13 times more likely to develop strabismus by age 4 if left uncorrected . Hyperopia is most common in the Hispanic population, next most common in Native Americans, African Americans, and Pacific Islanders, and least most common in Asians and Caucasians, according to a multi-ethnic study of atherosclerosis .

11. Symptoms Blurred vision –more for near than for distance . Accommodative asthenopia , i.e ., Tiredness of eyes and Frontal or fronto -temporal headache . E yestrain(sore, tired, red, dry, or watery eyes) Difficulty reading or performing near tasks Vision that seems worse at night or in dim light. Squinting of eyes Frequent blinking Decreased Binocularity Eye hand coordination can be decreased.

12. Signs Small size of eye ball. Small size of cornea . Anterior chamber is shallow and the angle is narrow. Visual acuity varies with the degree of hypermetropia and the power of accommodation. D ivergent squint or Convergent Squint Ophthalmoscopically -         a) Optic disc is smaller, hyperaemia with less defined cup disc ratio.      b) It may show a characteristic appearance which may resemble optic neuritis or papilloedema .         c) Tortuosity and abnormal branching of blood vessels.

13. Complications : Recurrent stye , blepharitis or chalazion may occur due to repeated rubbing of the eyes to get clear vision. Accommodative Convergent squint may develop in children due to excessive use of accommodation. Amblyopia . Angle closure glaucoma due to small eye with shallow anterior chamber and narrow anterior chamber angle.

14. Diagnosis The gold standard for visual acuity testing is to use the Snellen chart using manifest and cycloplegic refraction .   Subjective refraction can be performed with a visual acuity chart at far distance and near distance Objective refraction can be performed using an auto-refraction machine or retinoscopy .

15. Treatment : A)Optical : 1.Glasses : Convex lenses are prescribed after cycloplegic refraction , particularly children below 10 years. 2.Contact lenses . B )Surgical : 1.Keratophakia. 2. Epikeratophakia . 3.Keratomileusis. 4.Secondary IOL implantation in Aphakia . :

16. Bibliography Brien Holden Vision Institute Modules https://eyewiki.aao.org/Hyperopia Optometryeducation.blogspot.com