Presbyopia is the most common refractive error worldwide. Due to increasing patient expectations of spectacle independence, several refractive corneal surgical solutions, (eg, multifocal corneal ablation or intrastromal femtosecond ring incisions) have been developed to correct distance, intermediate, and near vision.1,2 However, none of these are optimal for all patients. Intraocular lens (IOL)–based surgical procedures using multifocal lenses and enhanced depth of focus IOLs show good visual outcomes but also disadvantages such as symptoms of halo, glare, or starburst, reduced contrast, or reduced vision in low light.3–5 Another option to reduce the need for spectacles is the implantation of corneal inlays. This refractive procedure can be used in the treatment of presbyopia by changing the refractive index of the cornea (Flexivue Microlens; Presbia, Los Angeles, CA; or Icolens; Neoptics AG, Hunenberg, Switzerland), by changing the corneal curvature (Raindrop Near Vision Inlay; ReVision Optics, Lake Forest, CA), or by extending the depth of focus (KAMRA inlay; AcuFocus, Irvine, CA).6 Small aperture corneal inlays are implanted monocularly in the non-dominant eye and improvement of near and intermediate vision without significant loss of distance vision has been shown in previous trials.7,8
The main outcome of this prospective clinical trial was the evaluation of uncorrected and corrected distance visual acuity (UDVA and CDVA), contrast sensitivity, defocus curves, and visual field in patients with a small aperture corneal inlay implanted in the non-dominant eye in combination with bilateral cataract surgery. In this study, the usability and early efficiency of binocular cataract surgery with concurrent implantation of a small aperture corneal inlay was investigated.
Patients and Methods
In this prospective, randomized clinical trial, cataract surgery was combined with the implantation of a corneal small aperture inlay (KAMRA inlay). All surgeries were performed at the Ruhr-University Eye Hospital in Bochum, Germany, by the same experienced surgeons (laser treatment: ME; manual surgery: HBD). The local ethics committee approved the trial and an informed consent was obtained for all patients. The tenets of the Declaration of Helsinki were observed. Prior to surgery, the patients were randomized into two treatment groups (inlay-cataract and control) by a computer random generator. Inclusion criteria for the study were patients older than 59 years with significant bilateral cataract (Lens Opacities Classification System III NC grades 2–5) and corneal regular astigmatism of less than 0.75 diopters (D). Exclusion criteria included microphthalmia, previous ocular surgery including corneal or refractive surgery, chronic intraocular inflammation, acute ocular disease, diabetes mellitus with retinal changes, any type of glaucoma, pseudoexfoliation syndrome, macular degeneration, pupillary irregularity, keratoconus, corneal endothelial dystrophy, pregnancy, or participation in another trial in the past 30 days.
Visual acuity, refraction, contrast sensitivity, and visual field were analyzed. The study visits took place 1, 4, and 12 weeks after surgery. The OPTEC 6500P Vision Tester (Stereo Optical Company, Inc., Chicago, IL) was used to examine uncorrected near visual acuity (UNVA) and UDVA, corrected near visual acuity (CNVA) and CDVA, defocus curves, and contrast sensitivity. The visual field was examined with the Octopus (Haag-Streit, Inc., Wedel, Germany).
In the inlay-cataract group, the dominant eye was treated first. The dominant eye was determined using the Miles test, the Porta test, and the Dolman method. A corneal pocket was made with a femtosecond laser (iFS; AMO, Inc., Santa Ana, CA). The pocket depth was set to 200 µm. Immediately after the laser treatment, state-of-the-art manual small incision cataract surgery with phacoemulsification and implantation of a three-piece monofocal IOL (Tecnis ZA9003; Johnson & Johnson Vision, Santa Ana, CA) was performed under the operating microscope. Finally, the small aperture corneal inlay (KAMRA inlay) was placed intrastromally inside the previously created corneal pocket under the operating microscope. The non-dominant eye of patients in the inlay-cataract group was implanted with a monofocal IOL 2 weeks later. The control group underwent two separate small incision standard cataract surgeries with implantation of a monofocal IOL (ZA9003; AMO, Inc.) in their dominant and non-dominant eyes. The target refraction for all eyes in both groups was emmetropia. No additional surgery was performed.
All statistical analyses were performed using commercial analytics software (SPSS version 22.0; SPSS, Inc., Chicago, IL). Significance between the groups was calculated using the Student's t test. A P value of less than .05 was considered statistically significant.
Sixteen patients with advanced cataracts underwent cataract surgery on both eyes in separate surgeries. Eight patients were randomized into the inlay-cataract group and received the small aperture corneal inlay in the non-dominant eye. The mean age was 71.1 ± 7.2 years (range: 59 to 82 years) in the inlay-cataract group and 70.6 ± 5.2 years (range: 61 to 77 years) in the control group. There was no significant difference in both groups (P = .88; Table 1). In the inlay-cataract group, 2 patients were male and 6 were female. In the control group, 3 patients were male and 5 were female. Mean Lens Opacities Classification System (LOCS) grade was 3.4 in the control group and 3.3 in the inlay-cataract group. There was no statistically significant difference in LOCS III grading between treatment groups (P = .43).
Baseline Study Population Demographics
In both groups, refractive outcomes were analyzed after 12 weeks. In the inlay-cataract group, the mean refractive error (spherical equivalent) was −0.42 ± 0.27 D (range: 0.00 to −0.75 D) in the dominant eye. In the non-dominant eye with the small aperture corneal inlay, the mean spherical equivalent was −0.39 ± 0.66 D (range: −1.60 to +0.50 D).
In the control group, the mean spherical equivalent was −0.17 ± 0.33 D (range: −0.63 to +0.25 D) in the dominant eye and +0.02 ± 0.57 D (range: −0.38 to +1.38 D) in the non-dominant eye. There was no statistically significant difference between the groups (dominant eye: P = .21, non-dominant eye: P = .12; Table 1).
Mean UDVA was 0.04 ± 0.07 logMAR at 4 weeks and 0.01 ± 0.06 logMAR at 12 weeks postoperatively in the control group and 0.03 ± 0.08 logMAR at 4 weeks and 0.04 ± 0.12 logMAR at 12 weeks postoperatively in the inlay-cataract group. The difference in UDVA between groups was not statistically significant after 12 weeks (P = .59).
Mean uncorrected intermediate visual acuity (UIVA) was 0.21 ± 0.12 logMAR at 4 weeks and 0.20 ± 0.07 logMAR at 12 weeks postoperatively in the control group and 0.07 ± 0.14 logMAR at 4 weeks and 0.06 ± 0.11 logMAR at 12 weeks postoperatively in the inlay-cataract group. The UIVA was significantly better in the inlay-cataract group (P = .03).
Mean UNVA was 0.35 ± 0.2 logMAR at 4 weeks and 0.32 ± 0.08 logMAR at 12 weeks postoperatively in the control group and 0.11 ± 0.15 logMAR at 4 weeks and 0.11 ± 0.24 logMAR at 12 weeks postoperatively in the inlay-cataract group. There was better UNVA in the inlay-cataract group, but it was not statistically significant (P = .07, Figure 1, Table 2).
Binocular uncorrected (A) distance, (B) intermediate, and (C) near visual acuity 6 months after surgery.
An improvement in visual acuity of up to 2.5 lines can be seen in the defocus curve over a wide range from +2.00 to −3.00 D. These findings correlate with the tested visual acuity in logMAR units (Figure 2).
Mean 3-month postoperative binocular defocus curve in the inlay-cataract and the control group. x-axis = defocus (diopters), y-axis = visual acuity (logMAR)
Contrast sensitivity was examined 12 weeks postoperatively without glare under mesopic conditions at frequencies of 1.5, 3, 6, and 12 cycles per degree (cpd) and under photopic conditions at frequencies of 3, 6, 12, and 18 cpd. There was no statistically significant difference between both groups under binocular photopic and mesopic conditions. Under binocular mesopic conditions with glare, discrete reduced contrast sensitivity was seen in the inlay-cataract group in comparison to the control group. However, the difference was not statistically significant (Figure 3).
Log contrast sensitivity function 3 months postoperatively under (A) photopic conditions without glare, (B) mesopic conditions without glare, and (C) mesopic conditions with glare.
Postoperative visual field examination showed a mean deviation of 4.36 ± 1.65 dB in the non-dominant eye of the inlay-cataract group and 2.71 ± 2.38 dB in the non-dominant eye of the control group. There was no statistically significant difference between groups (P = .46).
Our findings demonstrate that implantation of monofocal IOLs in combination with a small aperture corneal inlay in the non-dominant eye helps to increase intermediate and near visual acuity. Although the better CNVA in the inlay-cataract group was not significantly different than in the control group, the UNVA was on average two lines better in this group. Improvement in UIVA and UNVA in the inlay-cataract group was more than would be expected due to the slightly more myopic endpoint achieved in the inlay-cataract group relative to the control group. The mean difference in refractive outcomes between groups was −0.25 D in the dominant eye and −0.41 D in the non-dominant eye. This difference would be expected to affect UDVA by approximately one line and to provide approximately one line of UNVA. The inlay-cataract group had a mean UDVA within one line of the control group (0.04 vs 0.01 logMAR). This result may be in part the result of the expanded depth of focus in the inlay eye, which provides improved acuity in both the plus and minus direction around the peak of the defocus curve (Figure 2).
Contrast sensitivity is often used to assess functional vision. In phakic patients monocularly implanted with the small aperture corneal inlay, contrast sensitivity for monocular and binocular mesopic and photopic conditions remains within normal ranges after surgery.9,10
We found similar results in a cataract population and no significant difference between the inlay-cataract and control groups, indicating functional vision is not impaired by the presence of the small aperture inlay.
Visual field assessments between the inlay-cataract and control group showed a lower, but not significantly different, mean deviation for the inlay-cataract group. The visual field results in this study did not show any constriction of the visual field or introduction of isolated field defects in the presence of the small aperture. The slight depression of the visual field in the inlay-cataract eyes relative to the control group eyes is anticipated as a result of the effect of the small aperture of the inlay. This small effect was also found in a study of 24 phakic presbyopic patients implanted with the corneal inlay, where a reduction in mean deviation from 0.21 ± 1.25 dB preoperatively to −0.35 ± 0.87 dB 12 months postoperatively was determined.9 Similar results were found in a retrospective trial published by Tomita et al.11
In comparison to IOL-based presbyopia correcting solutions, the small aperture corneal inlay can be removed without an intraocular procedure in cases where an uninterrupted view of the retina is needed. Nevertheless, there is always a risk of corneal infection or opacity in corneal surgery. Moreover, long-term results are not yet available.
The implantation of small aperture corneal inlays seems to be an interesting alternative for pseudophakic patients who desire good near, intermediate, and distance visual acuity with spectacle independence.
- Paley GL, Chuck RS, Tsai LM. Corneal-based surgical presbyopic therapies and their application in pseudophakic patients. J Ophthalmol. 2016;2016:52638702.
- Hawker MJ, Madge SN, Baddeley PA, Perry SR. Refractive expectations of patients having cataract surgery. J Cataract Refract Surg. 2005;31:1970–1975. doi:10.1016/j.jcrs.2005.03.065 [CrossRef]
- Gil MA, Varón C, Cardona G, Vega F, Buil JA. Comparison of far and near contrast sensitivity in patients symmetrically implanted with multifocal and monofocal IOLs. Eur J Ophthalmol. 2014;24:44–52. doi:10.5301/ejo.5000335 [CrossRef]
- de Vries NE, Webers CA, Touwslager WR, et al. Dissatisfaction after implantation of multifocal intraocular lenses. J Cataract Refract Surg. 2011;37:859–865. doi:10.1016/j.jcrs.2010.11.032 [CrossRef]
- Chiam PJ, Chan JH, Aggarwal RK, Kasaby S. ReSTOR intraocular lens implantation in cataract surgery: quality of vision. J Cataract Refract Surg. 2006;32:1459–1463. doi:10.1016/j.jcrs.2006.04.015 [CrossRef]
- Gil-Cazorla R, Shah S, Naroo SA. A review of the surgical options for the correction of presbyopia. Br J Ophthalmol. 2016;100:62–70. doi:10.1136/bjophthalmol-2015-306663 [CrossRef]
- Waring GO 4th, . Correction of presbyopia with a small aperture corneal inlay. J Refract Surg. 2011;27:842–845. doi:10.3928/1081597X-20111005-04 [CrossRef]
- Dexl AK, Jell G, Strohmaier C, et al. Long-term outcomes after monocular corneal inlay implantation for the surgical compensation of presbyopia. J Cataract Refract Surg. 2015;41:566–575. doi:10.1016/j.jcrs.2014.05.051 [CrossRef]
- Seyeddain O, Bachernegg A, Riha W, et al. Femtosecond laser-assisted small-aperture corneal inlay implantation for corneal compensation of presbyopia: two-year follow-up. J Cataract Refract Surg. 2013;39:234–241. doi:10.1016/j.jcrs.2012.09.018 [CrossRef]
- Lin L, van de Pol C, Vilupuru S, Pepose JS. Contrast sensitivity in patients with emmetropic presbyopia before and after small-aperture inlay implantation. J Refract Surg. 2016;32:386–393. doi:10.3928/1081597X-20160217-04 [CrossRef]
- Tomita M, Kanamori T, Waring GO 4th, Huseynova T. Retrospective evaluation of the influence of pupil size on visual acuity after KAMRA inlay implantation. J Refract Surg. 2014;30:448–453. doi:10.3928/1081597X-20140530-03 [CrossRef]
Baseline Study Population Demographics
|Group||Age (y)||Axial Length (mm)||Sphere (D)||Cylinder (D)||SE (D)|
|Group||UDVA (logMAR)||UIVA (logMAR)||UNVA (logMAR)||CDVA (logMAR)||CIVA (logMAR)||CNVA (logMAR)|