Parameters for defining quality of vision

According to Oliver Findl, it is becoming increasingly important to use a wider variety of parameters to assess visual quality after cataract surgery in order to gain a better understanding of patient's day-to-day experiences.

Speaking at the "Better optics for better vision" symposium, Dr Findl discussed how the recent introduction of aspheric IOLs has increased interest in using additional parameters to assess visual function, rather than just the standard visual acuity (VA) tests. For example, it is becoming more common to use low contrast VA charts or sinusoidal ratings at different spatial frequencies whereupon the resulting contrast sensitivity function can be compared with that of standard spherical IOLs.

A number of companies produce aspherical IOLs with prolate surfaces of different intensities to compensate for the positive spherical aberrations of the cornea. Findl himself conducted a bilateral randomised study demonstrating that an aspherical IOL (Tecnis, AMO) can actually increase contrast sensitivity, especially at 12 cycles per degree, under mesopic conditions. As a result of manufacturers using different models of the ?average' cornea there can be problems for patients who have a spherical aberration far from the norm. In these cases an aspheric lens may not represent a much better option than conventional spherical designs.

In addition to the physical, objective measurements, Findl believes we should be measuring the patient's subjective assessment of their visual function and how it relates to their quality of life. Although it is not uncommon for patients to have unrealistic expectations of their surgery, it should always be considered that glare or halos, poor contrast acuity or IOL edge glare could be real reasons for a patient's negative opinion. Questionnaires offer a different method of assessment that allow for a broader picture and understanding.

Findl made it clear that we cannot rely on the traditional visual tests alone to decide whether treatments are successful or not. It is vital to get a wide range of data from physical tests through to patient questionnaires in order to see the bigger picture.

Ophthalmology Times Europe reporting from the XXIV Congress of the ESCRS, London, 9-13 September, 2006.