Pre-final Hyperopia Flashcards
The term hypermetropia is derived from hyper meaning “______”
Met meaning “______” and opia meaning “_____”
“in excess”
“Measure”
“Of the eye”
Hyperopia also called
Longsightedness
First suggested
1755 kastner
It is the refractive state of eye where in parallel rays of light coming from infinity are focused behind the sentient layer of retina with accommodations being at rest
Hyperopia
______ _____ is behind the retina which receives a blurred image
Posterior focal point
-Most common
-total refractive power of eye is normal
-shortening of eyeball
-1mm short -3 D of HM
-At birth +2.5 -3D of Hm (physiologically)
-pathologically seen in cases like orbital tumour, inflammatory mass ,oedama
Axial
-flattening of cornea,lens or both
-1mm increase in radius of curvature results in 6D of HM
-never exceed 6D HM physiologically
-congenitally flattened (cornea plana)
-result trauma and disease
Curvature
-change in refractive index with age
-physiologically in old age
-pathologically in diabetics under treatment
INDEX
-posteriorly placed crystalline lens
-occurs as congenital anomaly
-result of trauma or disease
POSITIONAL
The 5 etiology
Axial
Curvature
Index
Positional
Absence of lens
Clinical types
Simple hyperopia
Pathological
Functional hyperopia
-Most common
-results from Normal biological variations in development of eyeball
-include axial and curvature hypermetropia
-maybe hereditary
Simple hyperopia
-anomalies lie outside the limits of biological variations
-acquired hypermetropia ( decreases curvature of outer lens fibers in old age, cortical sclerosis)
Pathological hypermetropia
Pathological hypermetropia has a
Positional hypermetropia
Aphakia
Consecutive hypermetropia
-Results from paralysis of accommodations
-seen in patients with 3rd nerve paralysis and internal ophthalmoplegia
Functional hypermetropia
-parellel ray focus behind retina
-diffusion circles produce blurred and indistinct images
-retina is nearer to nodal point
-image is smaller than emmetropic
-ray diverge from retina
-formation of clear image is possible only when converging power of eye is increased
OPTICAL CONDITION
The relative sizes of the image in hypemetropia,emmetropia and myopia
AB is the object , (N) is the nodal point of the eye. The image is at obtained by drawing straight lines from A and B through N to the retina. Since the retina is the hypermetropic (H) it’s nearer to N. And in the myopic eye (M) is further away than in emmetropic eye (E) it follows the image of the first (1) smaller and that second (3) is larger than the image of the emmetropic eye (2)
Total hypermetropia=
Latent + manifest
(Facultative+ absolute)
Nomenclature
-it is the total amount of REFRACTIVE error, estimated after complete cycloplegia with atropine
-divide into latent and manifest
Total hypermetropia
-corrected by inherent tone of ciliary muscle
-usually about 1D
-high in children
-decreases with age
-revealed after abolishing tone of ciliary muscle with atropine
LATENT HYPERMETROPIA
-Remaining part of total hypermetropia
-correct by accommodation and convex lens
-measure by add strongest lens with max vision
-consists of facultative and absolute
Manifest hypermetropia
Corrected by patients accommodative effort
Facultative hypermetropia
Residual part not corrected by patients accommodative effort
ABSOLUTE HYPERMETROPIA
Manifest Hypermetropia-absolute HYPERMETROPIA= facultative Hypermetropia
(Strongest lens) - (weakest lens)
-total hm -manifest hm= latent hm
Manifest hypermetropia cont
-at birth +2+3D hypermetropia
-slightly increase in one year of life
-gradually diminishes until by age 5-10 years
Normal age variation
A type of ametropia light passes through the different media of the eye forming focal point behind the retina
Hyperopia
A type of astigmatism where both focal points fall behind the retina
Compound hyperopic astigmatism
Another term of hyperopia
Longsightedness
