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PSEUDOPHAKIA
APHAKIA
Presenter: Pushkar DhirModerator:- DR.O.P .Gupta
???APHAKIA???
Absence of crystalline lens from patellar foss
APHAKIACAUSES
Congenital Traumatic Absorption of Lens
Posterior Dislocation in vitreousSurgical Removal
OPTICS OF APHAKIA CHANGES IN CARDINAL DATA
• Eye becomes highly HM(Far- Sightedness)
• Power reduces from +60 to +44d• Anterior focal point becomes 23.2
mm in front of cornea• Posterior focal 31 mm behind the
cornea• Two principle points are almost on
anterior surface of cornea• Nodal points are nearer and 7.2mm
behind cornea
CLINICAL SYMPTOMSSYMPTOM
• Defective vision for both far and near .
• Erythropsia and cynopsia i.e., seeing red and blue Images due to excessive entry of ultraviolet and infrared rays in the absence of crystalline lens.
SIGNS• Limbal scar - Surgical Aphakia.• Anterior chamber is deeper than normal.• Iridodonesis.• Jet black pupil.• Purkinje image test: 3rd and 4th images are
absent.• Fundus examination: small hypermetropic disc.• Retinoscopy shows high HM.
IMAGE FORMATION
• Image size depends on axial length and keratometry reading
• Vary from 20 to 50%• Average 30%
ACCOMODATION IN APHAKIA• Total loss of accommodation• Glasses for near and distance are required
BINOCULAR VISION• Aneisokonia of 5% is compatible with binocular
vision• In aphakia aneisokonia is detrimental to
development of normal binocular vision
TREATMENT
Spectacles
Contact lens
Intraocular lens
Refractive
corneal
surgery
SPECTACLES
• Most common method of correction
• +10D is used • Near vision-+3 -+4 D
correction needed
Advantage-• Cheap• Easy to use• Safe method of correction
DISADVANTAGES1)IMAGE MAGNIFICATION• 1D of convex power leads to about 3 %
magnification of image;thus 10 dioptre=30%
• Difference of image size between the two eyes of about 7 % is tolerable
• beside that give rise to diplopia i.e., two images of one object are seen one small (from normal eye) and other larger (from aphakic eye).
• Not useful in unilateral aphakics
• Objects appear larger they appear falsely closer than reality, and this leads to physical in-coordination.
Roving Ring Scotoma
• Edge of a convex lens acts as a prism • higher the power of the convex lens the greater is the prism angle
(alpha). • Light falling on the prism bends towards its base by an angle alpha/2
.• Aphakic spectacles, the angle alpha being large, the light falling at
the edge of the lens bends towards the center of the lens (base of prism)
• And does not reach the pupil and is, therefore, not seen. • Resulting in an area of the visual field which is not visible to the
patient, or scotoma. • And because the edge of the lens is present all around the lens like a
ring, so it gives rise to a ring shaped scotoma. • Position of this scotoma is not fixed in the visual field because the
eye keeps moving (or roving) in relation to the aphakic spectacle.
Jack-in-the-box Phenomenon
PIN CUSHION AFFECT
• Magnification of image is more at the periphery of the lens due to prism• Effect,objects appear stretched out(large ,nearer,elongated in radial. Direction) at
the corners like a pin-cushion.• Moving objects appear to be faster• Straight lines become curves
Spherical Aberrations
• Light converges more near the edge of the lens than at the center.
• Rays of light falling near the edge are brought to focus in front of the rays falling at the center.
• Results poor quality of image despite appropriate correction of refractive error
Chromatic Aberrations
• The shorter the wave-length the more is the refraction a ray of light undergoes.
• VIBGYOR the violet end undergoes greater refraction than the red.
• This causes diffraction of light and makes the edges of white object appear rain-bow colored.
4)RESTRICTED VISUAL FIELD• 50% all around • Both monocular and binocular
5)COLOUR VISION• PT may complain of colored hue• Due to
-absence of natural filter of crystalline lens
6)COSMETIC BLEMISH• Eyes appear larger• Seen more in young aphakics
7)THICK AND HEAVY GLASSES
2)CONTACT LENS ADVANTAGES
• Less magnification of image• No chromatic aberrations• No prismatic affect• Wider field of vision• Cosmetically acceptable• Better for uniocular aphakics
DISADVANTAGES
• More cost• Cumbersome to wear-both for
young and old age• Corneal complications may be
associated
INTRAOCULAR LENS IMPLANTATION
Secondary Iols- In Sulcus ACIOL Iris Claw SFIOL
REFRACTIVE CORNEAL SURGERIES
Keratophakia Epikeratophakia Hyperopic LASIK
PSEUDOPHAKIA
The condition of aphakia when corrected with implantation of an IOL
is referred to as pseudophakia.
It is also known as artiphakia (as an artificial lens is implanted).
Types of IOLs
• Anterior chamber IOL• Iris-supported lenses• Posterior chamber lenses• Scleral Fixated IOLS
CALCULATION OF IOL POWER
• Most common method is SRK(Sanders Retzlaff and Kraff) by regression formula
P=A-0.9k-2.5L• P=power of IOL• A=constant• L=axial length of eyeball
A1(new const.) Axial lenth of eye
A1 3 <20mm
A1 2 20 to <21mm
A1 1 21 to <22mm
A 22 to 24.5 mm
A-0.5 >24.5mm
For long eyeball some adjustment is made in the formula by taking new constant A1
OTHER FORMULAS WHICH ARE USED
Hoffer Q SRK-T Holladay
REFRACTIVE STATUS OF PSEUDOPHAKIC EYE
EMMETROPIA
CONSECUTIVE MYOPIA
CONSECUTIVE HYPERMETROPIA
ASTIGMATISM
EMMETROPIA
• It is produced when the power of the IOL implanted is exact. It is the most ideal situation. Such patients require plus glasses for near vision
Yes!!! Got it
CONSECUTIVE MYOPIA
Consecutive myopia occurs when the IOL implanted
overcorrects the refraction of eye.
Such patients require glasses to correct the myopia for distance
vision May or may not need glasses for
near vision depending upon degree of myopia.
CONSECUTIVE HYPERMETROPIA
Consecutive hypermetropia develops when the under power IOL is implanted. Such patients requires plus glasses for distance vision and additional +2 to +3D for near vision.
ASTIGMATISM
Varying degree of surgery induced astigmatism is also present in pseudophakia
SIGNS OF PSEUDOPHAKIA
• Surgical limbal scars may be seen.• Anterior chamber is slightly deeper than
normal.• Mild iridodonesis of iris may be demonstrated.• Purkinje image test shows four images.
• Pupil is black in colour but, when light is thrown in pupillary area, shining reflexes are absorbed .
• When examined under magnification after dilating the pupil , the presence of IOL is conformed.
• Visual status and refraction will vary, depending upon the power of IOL implanted.
References
• Gullstrand’s schematic eye: to listing reduced eye - Google Search
• Volume 1, Chapter 33. The Human Eye as an Optical System
• Epikeratophakia - Google Search• Chapter 38 – Optics of Aphakia and
Pseudophakia | Free Medical Textbook• jack_in_box.pdf
