Target specific focal points to optimize refractive outcomes of cataract surgery

When we perform cataract surgery, we can optimize refractive outcomes by targeting specific focal points. This allows our patients the benefit of reduced dependence on glasses as well as removal of the cataract. Where we target our patients’ postoperative refractions depends largely on their daily activities, with a distinction being made between distance vision vs. near and intermediate vision.

In the young normal eye, the range of vision without glasses is fantastic due to the high degree of accommodation, which can be more than 10 D. This range decreases with age and the onset of presbyopia until spectacles become required for near vision. The typical IOLs that are used with cataract surgery are monofocal with no ability to accommodate or change focus. While some accommodating IOLs are commercially available, their range is limited and not comparable to a young crystalline lens.

Uday Devgan

The focal point of the eye in meters is calculated as the reciprocal of the refractive state in diopters. This means that an eye with a postop refraction of exactly 0.00 (plano) has an optimal focal point of infinity, which we can understand as far distance. The functional range then depends on the depth of field, which is related to pupil size, corneal aberrations, IOL characteristics and ambient lighting. The smaller the pupil size, the wider the depth of field (Figure 1). This is similar to a camera in which a large aperture lets in more light but decreases the depth of field.

Click here to read the full publication exclusive, Back to Basics, by Uday Devgan, MD.