Corneal inlay implantation for correction of presbyopia

Presbyopia results from age-related deterioration of the lens in the cornea of the eye and usually begins to develop at around 40 years of age. This form of lens deterioration causes difficulty with accommodation (focusing on near objects).

Standard treatment for presbyopia is corrective spectacles or contact lenses. Surgery (monovision or blended-vision laser in situ keratomileusis [LASIK], or refractive lens exchange or replacement) may be considered in some patients.

Corneal inlay implantation aims to improve near visual acuity and increase depth of focus. It may particularly benefit people who find it difficult to use spectacles or contact lenses, for instance, those with limited dexterity.

The procedure is usually performed on the non-dominant eye, under topical anaesthesia. The patient fixates their eye on a light source on a surgical microscope so that the surgeon can identify the target position on the centre of the visual axis. Laser or microkeratome techniques are used to create either a lamellar corneal flap or a pocket within the corneal stroma. The flap or pocket is separated with a spatula and a special tool is used to position the inlay within it, at the marked centre of the axis. The flap or pocket self-seals, holding the inlay in place. Patients are normally prescribed corticosteroids and antibiotic eye drops in the short term and artificial tears for as long as needed. The inlay can be removed or replaced if needed.

A case series of 32 patients reported that mean uncorrected near visual acuity (UNVA) in the treated eye improved from J7/8 preoperatively to J1 at 3 years, and binocular UNVA improved from J6 to J1 (p<0.00001). Mean uncorrected intermediate visual acuity (UIVA) in the treated eye improved from 20/40 to 20/25 at 3 years (p<0.00001); binocular UIVA also improved from 20/32 to 20/20 (p<0.001). Mean uncorrected distance visual acuity (UDVA) in the treated eye decreased slightly from 20/16 to 20/20 at 3 years (p<0.001). The change in binocular UDVA was not statistically significant (p=0.77).

A case series of 39 patients reported an improvement in mean UNVA in the treated eye from 20/50 preoperatively to 20/20 in 22 patients followed up for 4 years (p<0.001). Mean UDVA in the treated eye changed from 20/20 to 20/25 after 4 years (p=0.107).

The case series of 32 patients reported an increase in mean reading speed per minute from 142 words before treatment to 149 words after a mean follow-up of 2 years (p=0.029). Mean reading distance decreased from 48.1 cm to 38.9 cm (p<0.0001).

The case series of 32 patients reported that the percentage of patients using glasses all or most of the time decreased from 88% to 6% at 3 years (absolute numbers not given).

A case series of 24 patients reported a mean satisfaction with the procedure of 5.0 (on a scale of 1 to 7 where higher scores show more satisfaction) at 2 years after treatment. Mean satisfaction with reduction in reading glasses was 5.3 in bright light and 3.1 in dim light, using the same scale. It was reported that 75% (18 out of 24) of patients said that they would have the procedure again, 21% (5 out of 24) were undecided and 1 patient said he would not have the procedure again (exact question not reported).

The Specialist Advisers listed key efficacy outcomes as improved unaided near or reading vision with maintained distance vision.

Removal of the inlay was reported in 4 patients in the case series of 39 patients because of a buttonhole flap (in 1 patient at 6 weeks), refractive shifts and reported glare and halos (in 2 patients after 3 months) and a thin corneal flap causing symptoms (in 1 patient after 17 months). Following removal of the inlay, visual acuity returned to pretreatment values in all 4 patients.

Inlays were re-centred after 6 months because of initial misplacement in 2 patients in the case series of 32 patients. Both patients' visual acuity for near, intermediate and distance improved after recentration (reported graphically).

Cataracts affecting visual function and needing surgical treatment developed in 5 treated eyes after 3 to 4 years in the case series of 39 patients.

Loss of visual acuity at 3 years was reported in 14 patients in the case series of 32 patients (2 lines of UDVA were lost by 4 patients, 1 line of corrected distance visual acuity [CDVA] was lost by 9 patients, and 3.8 lines of CDVA were lost by 1 patient).

Flap striae developed in 1 patient after 1 month in the case series of 32 patients, resulting in epithelial ingrowth that needed repeated flap lift and debridement and was resolved by suturing after 2 months.

Hyperopic shifts greater than +0.5 D were measured in 4 patients in the case series of 32 patients at 3 years' follow-up. Myopic refractive shifts were also noted in 4 patients.

Severe, moderate and mild halo was reported by 1, 8 and 11 patients respectively in the case series of 32 patients at 3 years. Mild or moderate halo had been reported by 3 patients before treatment. Five patients in the same study reported severe problems with night vision.

A significant decrease in photopic (p<0.001) and mesopic (p<0.0001) contrast sensitivity at all spatial frequencies was reported in a case series of 508 patients at 1 year after treatment.

Very mild edge haze around the cornea was reported at 2 years' follow-up in all the patients in a case series of 8 patients.

The Specialist Advisers listed additional theoretical adverse events as infectious keratitis, corneal scarring or opacification, corneal thinning and melting, difficulty measuring intraocular pressure, failure to adapt to near monovision, reduction in unaided distance vision and reduction in best spectacle-corrected distance visual acuity.

The Committee recognised that although this procedure is usually undertaken for cosmetic reasons, some patients with presbyopia might be unable to use spectacles or contact lenses.

The Committee recognised that presbyopia is a progressive condition and therefore long-term data on efficacy and safety are important.

The Committee recognised that a number of inlays are available and they may differ in their efficacy, their safety and the way they work.