Intraocular lens insertion for correction of refractive error, with preservation of the natural lens

There are several types of refractive error including myopia, hypermetropia and presbyopia.

Refractive errors can usually be corrected by wearing spectacles or contact lenses. Surgical treatments include photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK) and insertion of corneal implants.

The procedure may be indicated for people with a high degree of myopia, or those for whom wearing spectacles is difficult, for example because of a disability or professional requirements.

The procedure is carried out with the patient under local anaesthesia. The pupil is dilated using topical medication, and a phakic intraocular lens (IOL) is inserted into the anterior or the posterior eye chamber via a small corneal incision. Depending on its design, the phakic IOL is anchored to the iris, placed in the angle between the cornea and the iris, or positioned to float over the surface of the natural lens. A nylon suture is sometimes used to close the incision.

Several different devices can be used for this procedure.

In a randomised controlled trial (RCT) of 50 eyes (with the fellow eye as control), mean Manifest Refraction Spherical Equivalent (MRSE) was -0.95±0.45 D in phakic IOL-treated eyes and -0.74±0.67 D in LASIK-treated eyes at 1‑year follow-up (p not significant). A non-RCT of 9,239 eyes reported that mean post-procedural MRSE was -1.78±2.03 D in phakic IOL-treated eyes, 0.36±1.30 D in LASIK-treated eyes and -0.18±0.5 D in PRK-treated eyes (level of significance not stated).

In a non-RCT of 769 eyes, correction to within 0.5 D of that intended was achieved in 69% (127 out of 184) of phakic IOL-treated eyes and 57% (57 out of 100) of LASIK-treated eyes at 1‑year follow-up (p=0.05).

A case series of 1,140 phakic IOL-treated eyes reported that the proportion of eyes with uncorrected visual acuity (UCVA) of 20/20 or better increased from 0% (0 out of 622) at baseline to 27% (62 out of 231) at 3‑year follow-up (significance not stated).

The Specialist Advisers stated that the key efficacy outcomes for this procedure include improvements in UCVA and best spectacle-corrected visual acuity (BSCVA), independence from optical aids and maintenance of quality of vision.

In a non-RCT of 9,239 eyes, retinal detachment was reported in 4% (12 out of 294) of phakic IOL-treated eyes, less than 1% (11 out of 3,009) of LASIK-treated eyes and less than 1% (9 out of 5,936) of PRK-treated eyes (retinal detachments occurred after a mean of 20.5, 24.6 and 53.6 months, respectively).

A meta-analysis of 6,338 eyes reported new-onset cataract development in 1% (15 out of 1,161) of eyes treated with angle-fixed anterior chamber IOL, less than 1% (20 out of 2,781) of eyes treated with iris-fixed anterior chamber IOL, and 9% (223 out of 2,396) of eyes treated with posterior chamber IOL (median follow-up 1 year). Anterior subcapsular cataract was reported in 2% (1 out of 43) of toric phakic IOL-treated eyes in an RCT of 88 eyes at 2‑year follow-up.

A case series of 399 eyes reported that explantation because of endothelial cell loss was necessary in 1% (3 out of 399) of eyes (mean follow-up 4 years). In the same study, mean endothelial cell density decreased significantly from 2,836±398 cells/m^m2 at baseline to 2,791±246 cells per mm² 4 years after insertion of a phakic IOL (p=0.004), and from 2,755±362 cells per mm² to 2,698±576 cells/mm² after insertion of a second type of phakic IOL at the same timepoint (p=0.002).

A case series of 263 eyes implanted with a phakic IOL reported halo and glare symptoms in 60% (157 out of 263) of treated eyes at 1‑year follow-up (reported as 'significant' in 21% [54 out of 263]).

The Specialist Advisers stated that key safety outcomes include glaucoma, loss of lines of BSCVA, reduced contrast sensitivity, night vision disturbances and the need for additional refractive surgery.