Implantable Contact Lens Vision Correction Surgery

History will guide us when we listen. Phakic intraocular lenses (pIOL) have been used to treat refractive error for decades – well before lasers were even invented. Now gaining in popularity, phakic IOLs are understood, by surgeons and patients alike, to be a safe additive and reversible refractive correction procedure.

In 1953, Strampelli implanted the first anterior chamber (AC) pIOL to correct myopia. This was a negative-powered polymethylmethacrylate (PMMA) lens that worked to correct myopia, however, the lens design and material in the AC resulted in many complications, including endothelial cell failure, pupil ovalisation and angle fibrosis. Additionally, inappropriate lens size caused the lens to rub and damage angle structures, with consequent glaucoma(Figure 1).1 Theodore Maiman invented the world’s first laser in 1960 – the ‘Ruby Laser’ (Figure 2), but it was not until the 1980s that laser energy was used to correct myopia with corneal reshaping. As we go further in this article and look at modern phakic lens implants, it will become evident that lens design features contributing to safety and success can all be traced back to the early observations with the Strampelli lens.

MYOPIA TREATMENT

Myopia is not going away. Acupoint treatment was unsuccessful as a traditional medicinal intervention designed to reduce the progression of myopia in teenage children, and it is now estimated that there will be five billion myopes in the world by 2050 – half the world’s population. Three surgical approaches can permanently correct myopia;

1. Refractive lens exchange,
2. Laser corneal reshaping, and
3. Phakic lens implants.

Refractive lens exchange offers a permanent solution but, as an intraocular procedure, is associated with loss of accommodation and increased risk of retinal detachment in this myopic population.

Laser corneal surgery is very effective as a correction for myopia and, with current technology including lenticule extraction (SMILE), 87% of patients will get correction within 0.5D of the intended outcome.

Laser refractive surgery is fast, safe and predictable for the right patient, but it does have intrinsic limitations. The cornea is irreversibly weakened; the ocular surface disrupted with exacerbation of ocular surface disease and dry eye problems; the correction of refractive error is associated with an increase in higher order aberrations – particularly spherical aberration; and the mechanical components of the procedure – whether the flap in LASIK or the lenticule cut and removal in SMILE – have their own potential problems with loss of corneal clarity. Certainly, there are limits to how much refractive error can be corrected with corneal laser reshaping, and this range of treatability has become narrower over the 25 years of LASIK as we better understand the impacts of our treatments on visual quality and corneal stability.