Cataract surgery with intraocular lens (IOL) implantation has become the most frequent type of surgical intervention in medicine. The success of this treatment is derived from several factors, such as surgical techniques, surgical tools, implant designs and peri-operative diagnostics. As high standards have been reached in cataract surgery, IOL implantation has become a safe and reliable procedure. However, IOL calculation was still somewhat difficult when ultrasound measurement alone was the gold standard.
Cataract surgery with intraocular lens (IOL) implantation has become the most frequent type of surgical intervention in medicine. The success of this treatment is derived from several factors, such as surgical techniques, surgical tools, implant designs and peri-operative diagnostics. As high standards have been reached in cataract surgery, IOL implantation has become a safe and reliable procedure. However, IOL calculation was still somewhat difficult when ultrasound measurement alone was the gold standard.
After the introduction of partial coherence interferometry (PCI) in the shape of the IOL-Master (Zeiss), there were rapid developments in axial length measurement and, consequently, IOL calculation, and the potential for mismeasurement of total axial length suddenly became negligible. Individualisation and optimisation of A-constants made IOL calculation and calculation formulae more accurate. New optical biometers such as the LENSTAR LS 900 (Haag-Streit) and the ALLEGRO Biograph (WaveLight), which provide the surgeon with more data on factors such as lens thickness, anatomical anterior chamber depth and retinal thickness, will probably promote the further development of new IOL power formulae.
For special IOLs such as multifocal (MIOLs), toric or accommodative IOLs, optimal IOL power calculation is extremely important. In the 1990s, one of the biggest arguments against MIOLs was the insufficient accuracy of MIOL calculation; this argument is no longer used due to the improvements discussed above. Most optical biometers measure axial length as well as K-values of the cornea. These data are therefore crucial for the special IOLs. For toric IOLs, surgeons can also rely on the accurate data provided by laser interferometric biometers. As patients often have to pay for these special implants themselves, they too demand a high level of accuracy. Cataract surgery is now evolving into a refractive procedure. Refractive lens exchange is becoming more and more popular. For high hyperopic or myopic patients, refractive lens exchange has become the only choice. In presbyopia treatment, refractive lens exchange with MIOL implantation is becoming increasingly common. Toric implants are now widely used.
The trend today is towards an individually customised approach in terms of IOL selection and manufacturing. New developments such as the Calhoun light-adjustable IOL underline this move towards personalisation of treatment, and in the long term could even allow wavefront-guided corrections to the IOL.
In summary, the introduction of optical biometry led to axial length measurement and IOL calculation becoming so reliable that presbyopic lens exchange, use of special IOLs (MIOLs, toric IOLs) and individualisation of patient treatment options are now possible. The combination of improved diagnostic tools and developments in IOL technology has shifted lens-based surgery from curative cataract procedures to functional refractive interventions.
