Aphakia

Ophthalmology Practicals Viva

1. APHAKIA
1) what is aphakia?
@ absence of lens in pupillary area is called aphakia.
2) what are the causes of aphakia?
@ causes of aphakia --surgical removal of cataract
---surgical removal of clear lens for high myopic correction
---absorption of lens in children following trauma
---traumatic dislocation of lens into vitreous
---traumatic exclusion of lens from the eye
---congenital absence of lens
3) sigs and symptoms of aphakia?
@ symptoms -- diminution of vision for both distant & near
-- erythropsia and cynopsia (seeing red and blue images due to entry of
excessive UV rays)
signs --operative scar
--deep anterior chamber due to lack of lens support
--iridodonesis
--pupil is jet black in colour
--fundus examination shows hypermetropic small disc
--retinoscopy reveals high hypermetropia

2. 4) What are the optical changes in aphakia?
@ eye becomes -- highly hypermetropic
-- total power of eye s reduced to +44D from +60D
-- total loss of accommodation
-- posterior focal point is 7mm behind the eye ball
5) why pupil looks jet black in aphakia?
@ pupil looks black because light is absorbed by retinal pigment epithelium and pigment of
choroid and no light is reflected black.
6) how will you correct aphakia?
@ --Intra ocular lens implantation is best available method—secondary IOL
--spectacles
--contact lenses
7) what is secondary IOL implantation?
@ when IOL implantation is done sometime after cataract surgery i.e. by second
operation, it is called secondary IOL. cataract removal is usually performed with IOL
implantation in one sitting, is called primary IOL implantation.
8) what difficulty may aphakic patient has after wearing spectacles?
@ aphakic patient faces
--spectacle causes enlargement of images by 25-30%.so it is not fused with the image of
other eye resulting in diplopia. that is why in uniocular aphakia glasses cannot be
prescribed and contact lens or secondary IOL is the only option.
--the thick aphakic glasses causes aberrations and does not provide quality vision and
result's in jack in box phenomenon.

3. 9) what type of glasses will aphakic patient accepts usually?
@ roughly about +10D with cylindrical lenses for surgically induced astigmatism are
required to correct aphakia in previously emmetropic patients. How ever
exact power of glasses will differ in individual cases and should be
estimated by retinoscopy or auto refractometry. An addition of +3D is required for
near vision to compensate the loss of accommodation.
10) Any surgical procedures for correction of aphakia?
@ -- keratophakia have been tried with out much success
-- epikeratophakia have been tried with out much success
-- hyperopic LASIK can be tried in few cases
11) aphakia is considered risk factor for which eye disease?
@ retinal detachment
12) what is the depth of normal anterior chamber?
@ the depth of normal anterior chamber is 2.5-3.5mm in centre in an emmetrope.
It is less in hypermetropes and more in myopes.
13) how will you differentiate aphakia from pseudophakia?
@ --by absence of shinning reflex in pupillary area
--absence of tremulousness of iris
--anterior chamber is less deep when compared to pseudopahkia
--visual acuity is less when compared to pseudophakia.

4. 14) what is visual acuity in aphakic patients?
@ visual acuity in patients depends on pre operative refractive status of eye .it is
counting fingers half meter if the patient was emmetrope and more if the
patient was myope.
15) what is clear lens extraction?
@ clear lens extraction is the procedure for correction of myopia of 16 to 18D
16) what is the disadvantage of clear lens extraction when compared to other refractive
surgeries?
@ in clear lens extraction there will be total loss of accommodation and patient has to
wear glasses for near vision, where as in other refractive surgeries patient will get rid of
glasses for both distant and near
17) what is anisometropia?
@ unequal refractive power in both eyes.
18) what is anisokonia?
@ is a condition where because of anisometropia the images formed from both eyes is
unequal in size.1D anisometropia causes 2% anisokonia.
19) Why diplopia develops is anisometropia?
@ aphakic glasses produces 20-30% magnification. Brain can tolerate and fuse
images having difference <5% of magnification only. if difference in image size is >5%
they cannot be fused in brain resulting in diplopia.