B i.e. Posterior chamber Classical signs of aphakia are - a deep anterior chamber, iridodonesis (tremulousness of iris), only 2 images on Purkinje's test, dark (jet black) papillary reflexQ and highly hypermetropic small disc on fundus examination with markedly defective vision for both far and near d/t high hypermetropia and absence of accommodationQ. A scar mark around limbusQ is found in surgical aphakia. Because of high hypermetropia, an aphakic eye requires the correcting spectacle lens of about 10-11 D worn in the usual position if the eye were previously emmetropic. The retinal image of aphakic eye wearing spectacles is about 25% (quaer) magnified/ larger than the emmetropic image. Hence vision of even 6/6 with 10-11 D glasses is not quite as good as it seems. Because of the disparity of images, correcting unilateral aphakia with spectacles when there is good vision in other eye 1/ t an intolerable diplopia. With contact lenses, a comfoable binocular vision may be attained in aphakia. However, posterior chamber intraocular (in bag) lens implantation is the best available method of correcting aphakiaQ - The optical rehabilitation of aphakia is best done by IOL implants and best site for intraocular lens implants is posterior chamber or within capsular bag Q and this is the normal anatomical position. Whereas anterior chamber lens has more complications like corneal endothelial damage, secondary glucoma, uveitis etc. - With incision in upper pa of cornea, the sutureless phacoemulsification produces 0.5-1D 'against the rule' astigmatism (since cornea is flattened in veical meridian) whereas, extra capsular cataract extraction (ECCE) performed with sutures produces 1 D to 3 D 'with the rule' astigmatism (which gradually reduces after suture removal & thee after). Aphakia Aphakia means absence of crystalline lens from eye. However from optical point of view, it may be considered a condition in which the lens is absent from the pupillary area. Causes of aphakia are - congenital absence of lens, surgical aphakia (most common), traumatic absorption or extrusion of lens and posterior dislocation of lens Optical changes of aphakia eye are: - Total power of eye is reduced to +44 D from + 60 D Q - Eye becomes highly hypermetropic (10-11 D) Q - All accommodation is lost Q - The anterior focal point becomes 24 mm (15 nun for normal eye) in front of the cornea - The posterior focal point becomes 31 mm (24 mm for normal eye) behind the cornea i.e. about 7 mm behind the eye ball (anteroposterior length of eye ball is 24 mm) Signs of aphakia are - deep anterior chamber, jet black pupil, iridodonesis (i.e. tremulousness of iris) and purkinje's image test shows only two images (normally four images are seen). Main symptoms of aphakia is marked defective vision for both far and near d/t high hypermetropia and loss of accommodationQ. Erythropsia and cynopsia (seeing red & blue images) occurs d/t excessive entry of UV and infrared rays in absence of lens Features Aphakia Pseudoaphakia (Ae-phakia) Definition Absence of It is correction of crystalline lens aphakia with an from it normal aificial intraocular position (pupillary lens (i.e. presence of area) in eye. an IOL implant). Surgical scar Limbal scar may be Mostly seen (unless seen in surgical but very small) near absent in congenital absence of lens limbus Anterior Deep (>4 mm) and Normal or slightly chamber wide deep ( Iridodonesis Tremulousness of Usually absent or very iris characteristically present & is inarkedQ mild Purkinje Only 2 images are All 4 images (just like image test seen with absence of 3rd & 4f5 images normal are seen) Pupil Jet black papillary Black in color but reflexQ when light is thrown shining reflexes are observed in pupillary area and presence of IOL is confirmed Fundus Hypermetropic Relatively normal examination small discQ sized disc Retinoscopy High Refractive status is & Refraction hypermetropiaQ variable and may be and astigmatism. 1. Emmetropia (ideal) Roughly + 10 to + occurs if exact 11D cylindericalQ power IOL glasses are required implanted; patient in previously needs plus (+) emmetropic eyes. glasses for near An addition +3 to vision only +4 D is required for 2. Consecutive near vision to myopia occurs compensate for when implanted IOL accommodation over corrects the refraction of eye; patient require glasses for distant vision/ myopia and may or may not need glasses for near vision. 3. Consecutive hypermetropia occurs when under power IOL is implanted; patient requires plus (+) glasses for distance vision & additional + 2D to + 3D for near vision.