PubMed · 6835933
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S Gigon, A Roth. 1983-02-01. [Aphakia today].. https://pubmed.ncbi.nlm.nih.gov/6835933/
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PURPOSE: We present the first in vivo CT and MR imaging description of intraocular lenses (IOLs), which are commonly encountered in elderly patients who have undergone cataract surgery. METHODS: A retrospective review was done of the imaging studies of 20 patients (22 eyes) with IOLs and of three patients (four eyes) with aphakia. CT and MR studies were performed with standard clinical protocols. RESULTS: Sixteen patients with 18 posterior IOLs underwent six CT and 43 MR studies. Four patients with four anterior IOLs had one CT and eight MR studies. The exact position of the optic portion of the IOL could be optimally determined on CT scans with 1-mm-thick sections and on fat-saturated fast T2-weighted MR orbital coil studies performed on a 1.5-T imager. The haptics could not be distinguished from the ciliary body. Three patients with aphakia had eight MR and two CT studies. Aphakia was difficult to identify if the image thickness was greater than the diameter of the pupil (2.5 to 4.0 mm). CONCLUSION: The optic portion of an IOL is visible on either high-quality CT or MR studies. However, the haptic portion is not visible on clinical in vivo images.
The majority of eyes that receive drug therapy exhibit some form of pathophysiological degradation. Two common pathophysiological states are retinal inflammation, which results in breakdown of the blood-retinal barrier, and aphakia. The purpose of this study was to examine the effects of aphakia and changes in retinal permeability and vitreous diffusivity on drug distribution in the vitreous humor of the human eye. The study was performed using a finite element model that accurately accounts for the vitreous geometry and boundary conditions. Intravitreal injection is the most common method for treating posterior segment disorders; therefore, this administration method was simulated using the models. Elimination from aphakic and phakic eyes was compared for four extreme injection locations and for two retinal permeabilities. When the retinal permeability was fixed at 5.0 x 10(-5) cm/s, increasing the drug diffusivity through the vitreous from 5.4 to 10(-7) to 2.4 x 10(-5) cm2/s decreased the half-life of drug from 64 hours to 2.7 hours. When the drug diffusivity was fixed at 5.6 x 10(-6) cm2/s, increasing the retinal permeability of the drug from 1.0 x 10(-7) to 1.0 x 10(-4) cm/s decreased the half-life of drug from 44 to 7 hours. Therefore, drug diffusivity and retinal permeability are key factors that influence elimination from the vitreous, and must be considered, particularly if the blood retinal barrier has been compromised. Faster drug elimination was observed in aphakic eyes than in phakic eyes, especially for drugs with a low retinal permeability and injected close to the lens capsule. Injection position is also important if the drug is injected in close proximity to a primary elimination barrier.
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