Optical rehabilitation or Correction of Aphakia

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.