This is another radial keratotomy patient (RK) with 16 cuts in the corneal. These are not the cleanest cuts and some are even double-cut, resulting in a cornea that has some irregular astigmatism. The patient is undergoing cataract surgery and the decision was made to implant the Apthera IC-8 small aperture IOL which is now owned by Bausch & Lomb. This IOL has a central donut shape that blocks some of the incoming light with an outer diameter of 3.23 mm (on the 6 mm optic) and a central opening of just 1.36 mm in diameter. With a 5 mm pupil, then the incoming light transmittance will be about 66% of a typical IOL (Apthera incoming light area = (5/2)2π -(3.23/2)2π + (1.36/2)2π versus a typical IOL incoming light area at 5mm = (5/2)2π for comparison). This sounds reasonable given the benefits but remember that it will drop off as the pupil size becomes smaller and dramatically so when the pupil is smaller than the outer edge of the donut.
This patient had a very good outcome and the small aperture IOL helped to block some of the corneal aberrations and irregularities. Fortunately our patient has reactive pupils that dilate in dark conditions so that the light transmittance is only moderately decreased. We will have a full review of this IOL as compared to the other extended depth of focus (EDOF) IOLs coming soon. I am happy to have this IOL in our toolbox, but like all IOLs, it cannot cheat physics and there is a give and take between benefits versus compromises.
