KAMRA Inlay Implantation for Presbyopia Compensation: A Retrospective Evaluation of Patient Satisfaction and Subjective Vision 12-Month Postoperative.

PURPOSE: The aim of the study is to evaluate patients' satisfaction and subjective vision 12 months after monocular KAMRA corneal inlay implantation for the surgical compensation of presbyopia. SUBJECTS AND METHODS: Medical records of patients who underwent corneal inlay implantation in the nondominant eye between 2013 and 2014 were retrospectively reviewed. Data were collected from several centers in Lebanon. Patients with hyperopia or myopia with presbyopia between 45 and 70 years not suffering from any other ocular pathology were eligible for inclusion. Twelve-month postoperative satisfaction score was evaluated in all patients as well as the subjective vision score for near, intermediate, and distant tasks.
RESULTS: This study included 73 patients. Almost 95% (69/73) of patients were satisfied or very satisfied with their vision and 93% (68/73) never or almost never used reading glasses while performing daily tasks. Subjective vision scores were found to be higher for distant and intermediate tasks performed during the day than for those performed during the night (P < 0.001). The average subjective vision score for reading a book or a newspaper in dim light was the lowest among all average subjective vision scores. No difference in satisfaction was found between patients with myopia or hyperopia or between males and females.
CONCLUSION: The implant of a small-aperture corneal inlay resulted in a substantial improvement in patients' distant, intermediate, and near subjective vision, better in normal light than in dim light, and most patients became spectacles independent.

Introduction

Presbyopia is the most common refractive error, currently affecting around 2 billion people worldwide.[1] The demand for spectacle independence has urged the expansion of research to find the most effective procedure with the best patient satisfaction. Among these procedures are corneal inlay implantations and corneal refractive surgeries.

Nowadays, there are three different types of intracorneal inlays of different mechanisms of action: lenses designed to change the eye's refractive index by generating a bifocal optic (e.g., Flexivue Microlens®and Icolens®);[12] those intended to reshape the anterior curvature of the cornea (e.g., Raindrop Near Vision®);[13] and small-aperture inlays which rely on the principle of pinhole optics to increase the eye's depth of focus by blocking unfocused light (e.g., KAMRA®Inlay by AcuFocus™).[4]

Since its approval in European subcontinent in 2005, refractive surgeons have been implanting KAMRA inlays on a commercial basis (nearly 20,000 inlays implanted today worldwide).[15] It was then approved by the US Food and Drug Administration in April 2015.[4] The KAMRA inlay was designed to improve uncorrected near and intermediate vision while minimally affecting distant vision.[6] Mid-term and long-term studies support the efficacy and safety of this inlay for the treatment of presbyopia.[57]

Corneal refractive surgery includes the creation of monovision in laser in situ keratomileusis (LASIK) and multifocal ablations (presbyLASIK).[8] These two are known to reduce distant visual acuity, stereopsis, contrast sensitivity, and quality of vision.[9]

The objective of this study is to evaluate the 12-month (mid-term) postoperative satisfaction among patients who have undergone KAMRA corneal inlay implantation as well as their subjective vision while performing daily near, intermediate, and distant tasks in normal and dim light. It also aims at exploring the effect of coexisting refractive errors and gender on patient satisfaction.

Subjects and Methods

This retrospective collection of data included patients from multiple centers in Lebanon who have undergone monocular implantation of the third-generation AcuFocus KAMRA ACI7000PDT corneal inlay in the nondominant eye between 2013 and 2014. Patients were consented for accessing their medical records. Patients were eligible for inclusion in this study if they completed the 12thmonth follow-up, were presbyopic, and were aged between 45 and 70 years. Previous ocular surgeries, anterior or posterior segment disease or degeneration, or any type of immunosuppressive disorders were key exclusion criteria.

Surgical technique

All inlay implantation surgeries have been performed by the same surgeon (W.H.) between January 2013 and December 2014. Eye dominance was determined by the Dolman method (hole-in-the-card test). The procedure was done under topical anesthesia. A 200-μm flap was created using a femtosecond laser, and KAMRA corneal inlays were implanted monocularly in the nondominant eye on the stromal bed at a minimum attempted depth of 200 μm flap. Proper centration was done using the AcuTarget system®(AcuFocus™).

Postoperative protocol

Postoperative medications included azithromycin dihydrate eye drops (twice daily for 3 days), dexamethasone phosphate eye drops (four times daily for 1 week) followed by loteprednol etabonate eye drops (three times daily for 1 month), and sodium hyaluronate 0.15% eye drop (every hour for the 1stweek then continued as needed).

Small-aperture intracorneal inlay

The current generation of the AcuFocus KAMRA inlay (model ACI7000PDT) is a 5 μm thin microperforated artificial aperture made of polyvinylidene fluoride with incorporated nanoparticles of carbon, with a total diameter of 3.8 mm and a central aperture of 1.6 mm. The opaque permeable material has a light transmission of 6.7%; it further features a pseudorandom microperforation pattern consisting of 8400 holes ranging from 5 to 11 μm in diameter to allow water and nutrition flow through the inlay to sustain the viability of the anterior stromal lamella and to prevent corneal thinning and epithelial decompensation. Based on the pinhole effect, the inlay increases the depth of focus and consequently improves near and intermediate visual acuity without significant impact on distance vision. The KAMRA does not split light between near, intermediate, and distant focal points. Therefore, binocular summation is maintained despite the monocular implantation in the nondominant eye.[5]

Patient evaluation

Data on patients' 12-month postoperative evaluation were collected. At the assessment visit, patients' overall satisfaction with their vision was rated using a subjective questionnaire developed by the manufacturer of the corneal inlay. Near vision was assessed by the ability to read a book or a newspaper, intermediate vision by the ability to read TV subtitles, and distant vision by the ability to drive. Patients rated their postoperative need for reading glasses under different lighting conditions, as well as their satisfaction with the procedure and with their near vision: they answered by very satisfied, satisfied, unsatisfied, or very unsatisfied. In addition, they were asked how often they had to use reading glasses and how easily, on a scale of 1–10 (1 = very difficult and 10 = easiest), and they could perform near-vision, intermediate-vision, and distant-vision tasks in day and nighttime and in normal and dim light depending on the task. Patients reported how easily they could perform sports activities and use a personal computer (PC) after KAMRA.

Statistical analysis

All analyses were performed using IBM SPSS Statistics for Windows (Version 20.0. Armonk, NY, USA: IBM Corp). Categorical variables were described using frequencies and percentages, whereas continuous variables were described using means and standard deviations. 95% confidence intervals were used, and a P < 0.05 was considered statistically significant. Differences in satisfaction between males and females and between hyperopes and myopes were tested using Chi-square tests. Comparison of subjective vision score for distant, intermediate, and near tasks between daytime and nighttime and between normal and dim light was performed using paired t-test.

Results

Study population and baseline characteristics

Seventy-three presbyopic patients were included in the study. The mean age of the population was 52.2 ± 3.4 years, 77% of which were female. Sixty-seven patients had coexisting hyperopia (91.8%), while the other 6 patients (8.2%) had myopia.

Patient satisfaction and dependence on reading glasses

At 12-month postoperatively, 69 patients (94.5%) were satisfied or very satisfied with their vision, and almost the same proportion reported never or almost never using reading glasses (93.2%). Results for postoperative satisfaction and spectacle dependence are shown in Figures 1 and 2, respectively. When comparing satisfaction between males and females, no significant difference was observed (P = 0.37). The age had no effect on the satisfaction level after surgery (P = 0.43). In addition, no difference in satisfaction was found between patients with myopia or hyperopia (P = 0.79).

Figure 1

Patient satisfaction 12 months after inlay implantation for presbyopia compensation

Figure 2

Spectacle dependence 12 months after inlay implantation for presbyopia compensation

Near, intermediate, and distance vision

Subjective vision scores for near, intermediate, and distant tasks are shown in Table 1. Subjective vision score was significantly higher for driving during the day than during the night (9.8 ± 0.8 vs. 9.5 ± 1.2, P < 0.001). Scores were also significantly higher for “reading TV subtitles” and “reading a newspaper or a book” in normal light than in dim light (P < 0.001). Comparisons are shown in Table 2. Patients reported an average vision score of 9.7 ± 1.0 for the use of PC and 9.7 ± 0.9 for the performance of sports activities. Overall, mean subjective vision scores for all tasks were above nine except for reading a book or a newspaper in dim light.

Table 1

Subjective vision score 12 months after inlay implantation for presbyopia compensation (n=73)

	Minimum-maximum	Range	Mean±SD	Variance
Day light driving after KAMRA	5-10	5	9.77±0.81	0.65
Night driving after KAMRA	4-10	6	9.45±1.16	1.33
Reading TV subtitles in normal light	5-10	5	9.7±0.91	0.82
Reading TV subtitles in dim light	4-10	6	9.23±1.34	1.79
Reading newspaper or book in normal light	4-10	6	9.64±1.03	1.07
Reading newspaper or book in dim light	1-10	9	8.88±1.72	2.94
How easy can you perform using a PC after KAMRA	5-10	5	9.67±0.97	0.95
How easy can you perform sports activities after KAMRA	5-10	5	9.67±0.88	0.78

SD: Standard deviation

Table 2

Comparison for distant, intermediate, and near vision between day and night or normal and dim light 12 months after inlay implantation for presbyopia compensation

	Day	Night	P
Driving after KAMRA, mean±SD	9.77±0.81	9.45±1.16	<0.001
	Normal light	Dim light	P
Reading TV subtitles after KAMRA, mean±SD	9.7±0.91	9.23±1.34	<0.001
Reading newspaper or book after KAMRA, mean±SD	9.64±1.03	8.88±1.72	<0.001

SD: Standard deviation

Complications

No inlay was explanted in the 12 months after surgery. There was no evidence of corneal thinning or epithelial ingrowth, and no inlay had to be recentered.

Discussion

Patients undergoing KAMRA in our study were mostly females (76.7%); this percentage is similar to that found in many studies on intraocular inlays for presbyopia.[10] This might be explained by the postulation that women are more likely to seek ophthalmic corrections to get rid of eyeglasses for esthetic purposes.

A high satisfaction rate was reported among our patients; almost 95% of them were satisfied or very satisfied with their vision and almost the same proportion reported never or almost never using reading glasses. These results were in agreement with results reported in two other studies on the same KAMRA model in which at 12-month postoperative, 75% of patients agreed that they would undergo the surgical treatment again.[511]

This result is higher than that observed with the previous KAMRA model (ACI7000). Dexl et al. reported a satisfaction rate of 83.9% with the ACI7000 at 5-year postoperative.[7] This difference might be due to the enhancements made to the current model and the improvement in the implantation and centration technique. Although our study evaluated patient satisfaction with near vision at 12 months, a similar study showed that the satisfaction increases between the 12thand 24thmonths or is maintained at the same level.[6]

When compared to other inlays, a similar result was obtained at 12 months after implantation of the Flexivue®inlay,[12] where 81.3% of the patients perceived their near vision in the operated eye as excellent and 93.8% were independent of their near spectacles. Similarly, 1 year after the implantation of the Icolens®inlay, 90% of the patients were satisfied with the procedure, but 40% of the patients reported always/often still using their spectacles for near vision tasks.[13] Whitman et al. reported that 92% of participants were somewhat, very, or completely satisfied with their inlay vision 1 year after Raindrop®inlay implantation.[14] A recent study on the same inlay showed a similar satisfaction rate (82%); however, 13.6% of the patients needed near glasses more often after surgery than before surgery. In addition, 42.3% of the patients reported having glare at night or dark place and 37.2% had a decrease of vision at night or in a dark place.[15]

When compared to other presbyopia compensation techniques, corneal inlays show a higher patient satisfaction rate. In a study on the correction of presbyopia by technovision central multifocal LASIK (PresbyLASIK), 76% of patients reported a high degree of satisfaction at 6 months, but only 72% of patients were spectacle independent for all distances.[8] In another study on monovision correction by LASIK, 90% of presbyopic patients were satisfied or highly satisfied with their overall results even though correction was still required for fine near work and driving, especially at nighttime.[9]

In our study, age did not affect the satisfaction level; no significant difference was observed in satisfaction between males and females and between myopic and hyperopic patients. Similar results were obtained in a study on patients undergoing KAMRA inlay implantation along with LASIK, where no significant differences in patient satisfaction and in the need for reading glasses were found between emmetropia, myopia, and hyperopia groups 6 months after surgery.[16] Contrarily, Tomita andWaring investigated the effect of age on patient satisfaction at 1 year following simultaneous LASIK and small-aperture corneal inlay implantation for hyperopic presbyopia.[17] They found that the older the patients, the higher their satisfaction, and conversely the lower their reduction in dependence on reading glasses. This result was justified by the fact that older patients appreciate even slight improvements in their vision unlike younger patients who rely on their near vision in their daily professions.

Our study showed a significant difference in subjective vision score for driving between daytime and nighttime and for reading TV subtitles and reading a newspaper between normal light and dim light. This was also reported in another KAMRA study where patients scored higher when asked about performing near, intermediate, or distance vision tasks under bright light conditions,[5] while other studies reported comparable scores for distant vision under any lighting condition.[611] It was suggested that the pinhole effect is more effective in normal light than in dim light since the amount of light reaching the retina is reduced;[5] another interpretation was that the forward light scatter (caused by the light entering the pupil through the 1.6 mm central aperture and the 8400 nutritional pores of the annulus) might diminish the efficacy of the inlay under dim light conditions.[6]

In this study, no recentration or explants were done; the same was observed in recent studies that followed patients for 1- or 2-year post-operative and used the new thinner model of the KAMRA (PDT).[518] With the older model of the inlay (ACI-7000), Yilmaz et al. reported three inlay explantations in one study and four in another.[1019] Explantations were due to patient dissatisfaction or unexpected complications; following explantation, patients safely returned to within ±1.00 diopter of their preoperative refractive state for near and distance vision. This shows that even when medically necessary or sought for any reason, explantation is safe. This represents an important advantage of this procedure being completely reversible, because unlike LASIK, it includes no ablation over the optical axis, and the increase in the depth of focus is not based on reshaping the corneal surface.

The explantation rate with the KAMRA is much lower than that with other types of inlays. For instance, for shape-changing inlays, Whitman et al. reported 11 explantations of the Raindrop®inlay and 18 exchanges due to decentration. The rate of exchanges, explantations, or both at 1 year was 7.8% mainly due to dissatisfaction with vision.[14] As for refractive inlays, the unique study on Icolens®reported 11 inlay explantations (out of 52 implants) up to 12 months after surgery due to poor refractive outcomes,[13] and one study on Flexivue®reported 6 explants out of 52 implants during 1-year follow-up due to significant discomfort caused by a reduction in distance vision and the presence of significant halos and glare.[20]

The effect of proper centration on postoperative visual acuity is controversial. Gatinel et al. reported 2 KAMRA inlay recentrations at 2 weeks and 3 weeks postoperatively, resulting in significant improvements in the visual acuity and quality of vision. They concluded that accurate centration of the inlay was an important factor in obtaining satisfactory results and that recentration was possible if proper centration was not obtained after the first surgery.[21] On the other hand, Corpuz et al. investigated the effect of inlay decentration in a retrospective analysis of 992 eyes and found no influence of the amount of inlay decentration on postoperative visual acuity.[22]

In our study, there was no evidence of corneal thinning or epithelial ingrowth. Of note, the ACI7000 first-generation KAMRA resulted in epithelial changes in the form of central and peripheral iron deposits in more than 56% of eyes after 3 years of follow-up,[4] whereas only one out of 20 patients showed these deposits after 2 years of follow-up with the current PDT inlay design.[18] These deposits were not associated with any visual or refractive outcomes. The new and thinner design, as well as the current deeper implantation compared to previous procedures, induces only minor topographic changes in the cornea.[18]

Long-term follow-up studies have reported stable efficacy of the KAMRA inlay with no description of inflammatory reactions, ulcerations, stromal fibrosis, or significant change in endothelial cell count.[718]

In a study that followed up patients undergoing KAMRA implantation for 12 months, Dexl et al. concluded that the objective visual acuity test results were in accordance with the subjective patient questionnaire results.[5] The ultimate goal of inlay implantation, from a patient's perspective, is to enable them to perform common near vision daily tasks (e.g., reading) without spectacles. It has been recently suggested that spectacle independence might even be a better indicator of “functional success” of the inlay implantation procedure than visual acuity or other measurements.[1623]

Conclusion

Our study suggests that the implantation of a small-aperture corneal inlay shows a high satisfaction rate among patients. In addition, patients had significant improvement in their subjective distant, intermediate, and near vision, better in normal light than in dim light, and most patients became spectacles independent. Many studies have shown the safety, stability, and efficacy of the KAMRA in presbyopia compensation, but such data are still scarce in the Middle East. Further studies and longer follow-up periods are needed to assess the long-term outcomes of this inlay.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.