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Optical rehabilitation or Correction of Aphakia by Dr Nikhil Bansal
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Removal of the cataractous lens renders
the patient Aphakic.
Aphakia- Aphakia literally means absence of crystalline lens from the eye.
causes
Congenital absence of lens. Due to absorption of lens matter. Traumatic extrusion of lens. Posterior dislocation of lens. Surgical aphakia occuring after
removal of lens.
symptoms
Defective vision. Erythropsia & cynopsia(i.e.seeing
red & blue images)
sign
Anterior chamber is deep. Iridodonesis. Pupil is jet black. Retinoscopy reveals high
hypermetropia.
For the pt. to be able to see clearly some form of optical rehabilitation must be provided.
This may be in the form of
1.Spectacles
2.Contact lenses
3.Intraocular lens
Comfort & convenience
Optical aberration
Aniseikonia
spectacle •Heavy
•Cosmetically poor
•Visual distortion, pin cushion effect because of central magnification
•Magnification of 20-30% so produces diplopia
Contact lens
•Insertion & removal cumbersome
nil •Magnification about 8%,tolarable
Iol Comfertable in every way
nil •Magnification 1-2%,negligible
INTRAOCULAR LENS
The central part overlying the optic axis is called Optic.
Peripheral arms used for placement & stabilization are the Haptic.
History
Intraocular lens implant history had its beginning on Nov.29,1949 when Harold Ridley, a British ophthalmologist performed his 1st case.
Types of IOLs
Anterior chamber IOL Iris-supported lenses Posterior chamber lenses
Anterior chamber IOL
Lie in front of iris & supported in the angle of anterior chamber.
ACIOL inserted after ICCE or ECCE. It is not so popular due to
comparatively higher incidence of bullous keratopathy.
Kelman multiflex type of ACIOL is used.
Iris supported lenses
These lenses are fixed on the iris with the help of sutures, loops or claws.
These lenses also have a high incidence of postoperative complication.
E.g. Singh & Worst’s iris claw lens.
Posterior chamber lenses
PCIOLs rest entierly behind the iris. This may be supported by the ciliary sulcus or the capsular bag, recent trend is towards in the bag fixation.
Depending on material of manufacturing,types of PCIOLs are available
Rigid IOLs- made entirely from PMMA.
Foldable IOLs- use after Phacoemulsification are made of silicon, acrylic, hydrogel & collamer.
Rollable IOLs- It is after phakonit technique.made of hydrogel.
Calculatio of IOL power-
Most common method is SRK formula by regression formula.
P=A-2.5L-0.9K P=power of IOL A=constant L=axial length of eyeball.
For long eyeball some adjustment is made in the formula by taking new constant A1.
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
Surgical technique of ACIOL implantation Can be carried out after ICCE & ECCE. After lens extraction, the pupil is
constricted by injecting miotics into A.C.
A.C. is filled with 2% methylcellulose or 1% sodium hyaluronate.
IOL,held by a Forceps gently slid into A.C.
Inferior haptic is pushed in the inferior angle at 6o’ clock position & upper haptic is pushed to engage in the upper angle.
Technique of posterior chamber IOL implantation
Implantation of rigid IOL- It implanted after ECCE. Capsular bag & A.C. is filled with
2% methylcellulose or 1%sodium hyaluronate.
IOL,hold by a Forceps.
Inferior haptic is pushed in the inferior angle at 6o’ clock position
The superior haptic is grasped by tip, & is gently pushed down & then released to slide in the upper part of the capsular bag behind the iris.
The IOL is then dilated into the horizontal position.
Implantation of foldable IOLs is made either with the help of holder-folder forceps or the foldable IOLs injector.
References
Parsons’ diseases of the eye.