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Describe aphakia and pseudophakia.

Ophthalmology · 3rd Professional

Aphakia is the absence of the crystalline lens from the pupillary area.
pseudophakia is the state in which the natural lens has been replaced by an artificial intraocular lens.

Sign of aphakia	Explanation
Deep anterior chamber	The iris has lost its support and falls back
Jet-black pupil	No lens to reflect light
Iridodonesis	Tremulousness of the iris on eye movement, from loss of lenticular support
Absent purkinje images III and IV	These are the reflections from the anterior and posterior lens surfaces; only images I and II, from the corneal surfaces, remain
Hypermetropia of about +10 to +12 dioptres	The loss of the lens removes about a third of the refractive power of the eye
Loss of accommodation	Absolute; a separate near correction of +3 D is required in addition
Other	The fundus appears small on ophthalmoscopy; and there is erythropsia and cyanopsia (a reddish or bluish tinge) because the lens no longer absorbs ultraviolet and blue light

The problems of correcting aphakia with spectacles — and this list is the reason intraocular lenses replaced them entirely: magnification of 25 to 30%, so that the image is far larger than in the fellow eye; consequent aniseikonia which the brain cannot fuse, so binocular vision is impossible in unilateral aphakia; a ring scotoma from prismatic effect at the lens edge, producing the "jack-IN-the-box" phenomenon in which an object disappears in the scotoma and then suddenly reappears; a roving ring scotoma as the eye moves; pincushion distortion; a restricted field; and the weight and cosmetic objection to very thick lenses

Signs of pseudophakia — a surgical scar or clear corneal incision; purkinje images III and IV are present but of abnormal size and orientation; the lens edge and positioning holes may be seen on retroillumination after dilation; a peripheral iridectomy may be present; the anterior chamber depth is near normal; and the refraction is close to emmetropia
Complications specific to pseudophakia — after-cataract; decentration and capture of the optic by the pupil; uveitis-glaucoma-hyphaema (UGH) syndrome from chafing by a malpositioned or anterior chamber lens; pseudophakic bullous keratopathy; late in-the-bag dislocation, characteristically in pseudoexfoliation, occurring many years later; dysphotopsia; and refractive surprise
Aphakic and pseudophakic glaucoma — occurs by several mechanisms and requires lifelong surveillance, particularly in children

Never leave an adult unilaterally aphakic with spectacles; the aniseikonia cannot be fused and the eye is functionally useless, so an implant or a contact lens is essential
Use a contact lens in an infant under about two; the Infant Aphakia Treatment Study found no advantage from a primary implant and more complications
Over-correct an aphakic infant for near; they have no accommodation and spend their time looking at close objects

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