Presbyopia is considered to be the “holy grail” of refractive surgery, and various treatment options, including cornea-based,1–7 lens-based,8,9 and sclera-based10,11 procedures, have been employed to manage it. However, cornea-based procedures are preferred by many surgeons in an individual with a clear crystalline lens to avoid various complications associated with refractive lensectomy.12–14 Of the available corneal options, laser in situ keratomileusis (LASIK) monovision is one of the commonly performed procedures, and has been shown to be safe and effective in various studies.2,15,16 However, monovision was found to decrease stereoacuity and contrast sensitivity as the degree of anisometropia between the eyes increased.17,18 Laser Blended Vision, performed with the MEL 80 excimer laser and the CRS-Master (Carl Zeiss Meditec GmbH), a procedure described by Reinstein et al,19–20 successfully combines monovision with extended depth of field achieved by aspheric laser ablation profile using a micro-monovision protocol to treat presbyopia. This procedure has been shown to be safe and effective across all types for ametropia, without a significant loss of contrast sensitivity.19–23
PRESBYOND Laser Blended Vision, or simply PRESBYOND, is the next version of Laser Blended Vision performed using the MEL 90 excimer laser and allows for import of preoperative spherical aberrations from Wavefront Aberration Supported Customized Ablation (WASCA; Carl Zeiss Meditec), use of a wide range of optical zones, and entry of functional age data of the patient into the CRS-Master. In this study, we report 1-year clinical outcomes of PRESBYOND including the safety, efficacy, re-treatment rate, and patient satisfaction in presbyopic patients who underwent this procedure at our center.
Patients and Methods
The study was approved by the institutional ethics committee of Nethradhama Eye Hospital and involved retrospective review of electronic medical records of the patients who had undergone LASIK for correction of presbyopia from June 2015 to June 2018. Only patients who had a corrected distance visual acuity (CDVA) of 20/25 or better in either eye were included in the study. Exclusion criteria were: previous refractive surgery, corneal and lens opacities that may affect vision, acute or chronic systemic disease, or any kind of immunosuppressive disorder. Only patients whose complete records were available and who had a follow-up of 12 months after the surgery were included.
Preoperative Evaluation and Treatment Planning
A complete ophthalmic examination was performed for all patients prior to surgery, which included anterior and posterior segment evaluation, dilated refraction, corneal topography with ATLAS topographer (Carl Zeiss Meditec) and Pentacam HR (Oculus Optikgeräte), and dry eye assessment with Schirmer's I and II, and tear film break-up time tests.
The first step in the preoperative refractive work-up was verification of the eye dominance, because the standard micro-monovision protocol of PRESBYOND Laser Blended Vision involves correcting the dominant eye for distance and the non-dominant eye for near. Dominance of the eye was tested using three methods: hole in the card test, shooting test, and camera test. Dominance was confirmed if the result was the same for at least two of the three tests. Once the dominance was verified, tolerance testing for anisometropia and micro-monovision was performed with retinoscopy lenses after applying the full manifest correction in both eyes. A positive sphere corresponding to a standard myopic target of +1.50 diopters (D) was then added to the non-dominant eye, followed by which the patient was asked to read the smallest letter on the Snellen distance vision chart with both eyes. While patients were reading the Snellen chart, they was asked if they experienced any visual discomfort or disturbances. The patients read a Jaeger chart with both eyes and were asked about their comfort with the near vision. If patients were satisfied with the quality of distance and near vision and did not report any symptoms, they were deemed tolerant of the target near additional correction. For those who expressed discomfort, the addition in the non-dominant eye was reduced in +0.25-D steps until they reported no blur with minimum discomfort. If patients could not achieve the desired near vision with the +1.50 D, the addition in the non-dominant eye was increased to +1.75 to a maximum of +2.00 D. Patients were given enough time determine their comfort with their vision by asking them to walk, read, and see on mobile devices and computer with the trial frame correction provided on both eyes. A contact lens monovision trial was not performed. Patients were counseled in detail about the expected but temporary side effects of dryness, glare, and vision fluctuations, which are expected to resolve within an adaptation period of up to 3 to 4 months.
WASCA was used to measure the ocular wavefront aberrations in scotopic condition and data at a diameter of 6 mm were analyzed. For patients in whom there was a discrepancy about age, functional age was calculated. In routine cases, calculation of functional age was not deemed necessary.
All surgical procedures were performed by two experienced refractive surgeons (SG, SB) using the VisuMax femtosecond laser (Carl Zeiss Meditec GmbH) and MEL 90 excimer laser. The CRS-Master software platform was used to design the aspheric ablation profile using the ocular wavefront data obtained by the WASCA aberrometer, which was then exported for treatment with the MEL 90 excimer laser.
The surgical procedure was similar to that of a standard femtosecond laser–assisted LASIK treatment. Flaps were created with the VisuMax femtosecond laser using a 100- to 120-µm flap thickness. Stromal aspheric ablation was performed using the MEL 90 excimer laser with an optical zone of 6.3 ± 0.23 mm (range: 6 to 6.5 mm) and 6.57 ± 0.12 mm (range: 6.5 to 6.8 mm) for the myopia and hyperopia group, respectively, and a 2.2-mm transition zone.
Patients were followed up at 1 day, 2 weeks, 3 months, and 12 months postoperatively. On all follow-up visits, measurement of uncorrected distance and near visual acuity (UDVA and UNVA), CDVA, distance-corrected near visual acuity, manifest refraction, and responses to a subjective questionnaire were obtained. We also analyzed the change in preoperative versus postoperative corneal higher order aberrations and spherical aberrations using the Pentacam HR, and attempted to derive a theoretical value of the depth of focus achieved, based on previous publications by Benard et al24 and Yi et al,25 who reported the relationship between spherical aberrations and depth of focus as 2.00 D/µm and 2.59 D/µm, respectively. The change in spherical aberrations (postoperative-preoperative) in micrometers was multiplied by a factor of 2.00 and 2.59 to derive the range of theoretical depth of focus in diopters achieved, as per these two studies, respectively.
Statistical analysis was performed using the SPSS statistical package (version 17.0; SPSS, Inc.). Data were checked for normality before analysis. If the data were normally distributed, paired Student's t tests were performed to compare the mean values of UDVA, UNVA, CDVA, and root mean square of spherical ocular aberration. If the data distribution was not normal, the Wilcoxon signed-rank test was used. A P value of less than .05 was considered statistically significant.
A total of 101 patients with a mean age of 51.05 ± 5.15 years (range: 40 to 65 years) who underwent bilateral treatment with PRESBYOND for myopic (38 patients) or hyperopic (63 patients) refractive error with or without astigmatism were included in the study.
Table 1 shows the preoperative demographic details of all patients included in the study. Mean follow-up was 14 ± 3 months. More than 96% of patients completed 12 months of follow-up.
Refractive Outcomes at 12 Months
In the myopia group, the mean SE refraction of the distance eye was +0.13 ± 0.32 D, attempted target SE for the near eye was −1.98 ± 1.89 D (range: 1.32 to −5.75 D), and the postoperative achieved SE in the near eye was −1.42 ± 0.33 D (range: −0.88 to −2.50 D) (Table A, available in the online version of this article). A total of 92% eyes were within ±0.50 D. All eyes were within ±1.00 D of the intended target refraction (Figure 1A). The surgically induced astigmatism was within ±0.50 D of the target induced astigmatism in 97% of eyes (Figure 1B). The residual astigmatism was within ±0.50 D in 97% of eyes postoperatively (Figure 1C).
Mean Spherical Equivalent Refraction (Diopters) of Distance and Near Eyes Before and After All Treatments
(A) Histogram showing the accuracy to the intended spherical equivalent refraction (SEQ) at 12 months for the myopia group. (B) Target induced astigmatism (TIA) vs surgically induced astigmatism (SIA) scatter plot for the myopia group. (C) Histogram showing change in refractive astigmatism for the myopia group. (D) Histogram showing the accuracy to the intended spherical equivalent refraction after all treatments for the hyperopia group. (E) Target induced astigmatism vs surgically induced astigmatism scatter plot for the hyperopia group. (F) Histogram showing change in refractive astigmatism for the hyperopia group. D = diopters
In the hyperopia group, the mean SE refraction in the distance eye was −0.13 ± 0.24 D, attempted target SE for the near eye was +2.89 ± 0.87 D (range: +1.52 to +5.65 D), and the postoperative achieved SE in the near eye was −1.28 ± 0.31 D (range: −0.63 to −2.00 D) (Table A). A total of 87% eyes were within ±0.50 D, and all eyes were within ±1.00 D of the intended target refraction (Figure 1D). The surgically induced astigmatism was within ±0.50 D of the target induced astigmatism in 89% of the eyes, whereas all eyes were within ±1.00 D of target induced astigmatism (Figure 1E). The residual astigmatism was within ±0.50 D in 93% of eyes postoperatively (Figure 1F).
The mean UDVA for distance eyes, near eyes, and binocularly was −0.01 ± 0.04, 0.37 ± 0.08, and −0.02 ± 0.05 logMAR, respectively, for the myopia group. UDVA at the 1-year follow-up visit is presented in Figures 2–3, respectively, for distance eyes, near eyes, and binocularly. Uncorrected binocular visual acuity was at least 0.0 logMAR (20/20) at distance and J3 (20/25) at near in 97% of patients.
Cumulative histogram for uncorrected distance visual acuity (UDVA) at 12 months, grouped into distance eyes, near eyes, and binocularly for the myopia group. CDVA = corrected distance visual acuity
Cumulative histogram for uncorrected near visual acuity (UNVA) at 12 months, grouped into distance eyes, near eyes, and binocularly for the myopia group. DCNVA = distance corrected near visual acuity
The mean UDVA for distance eyes, near eyes, and binocularly was −0.04 ± 0.06, 0.38 ± 0.09, and −0.05 ± 0.07 logMAR, respectively, for the hyperopia group. UDVA and UNVA at the 1-year follow-up visit is presented in Figures 4–5, respectively, for distance eyes, near eyes, and binocularly. Uncorrected binocular visual acuity was at least 0.0 logMAR (20/20) at distance and J3 (20/25) at near in 98% and 97% of patients, respectively. Figure A (available in the online version of this article) shows the combined outcomes of uncorrected binocular vision at distance and near at 1 year of follow-up for the myopia and hyperopia groups.
Cumulative histogram for uncorrected distance visual acuity after all treatments, grouped into distance eyes, near eyes, and binocularly for the hyperopia group. CDVA = corrected distance visual acuity
Cumulative histogram for uncorrected near visual acuity after all treatments, grouped into distance eyes, near eyes, and binocularly for the hyperopia group. DCNVA = distance corrected near visual acuity
Combined distance and near binocular uncorrected distance visual acuity for the (A) myopia and (B) hyperopia groups.
All eyes in the myopia group achieved CDVA of 20/20 or better postoperatively. At 1 year of follow-up, there was a loss of one line of CDVA for 4 eyes in the myopia group, of which 1 eye was 20/12.5 and 3 eyes were 20/16 preoperatively. No eyes lost two or more lines of CDVA (Figure 6).
Histogram showing the change in Snellen lines of corrected distance visual acuity (CDVA) for the (A) myopia and (B) hyperopia groups.
All eyes in the hyperopia group achieved CDVA of 20/25 or better postoperatively. Eleven eyes in the hyperopia group lost one line; 18% (2 of 11) of those eyes were 20/12.5 preoperatively and 82% (9 of 11) were 20/16 preoperatively. No eyes lost two or more lines (Figure 6).
Except for a few patients who required lubricants and topical cyclosporine therapy for symptoms of postoperative dryness, none of the eyes in either group had any short- or long-term complications such as diffuse lamellar keratitis, infection, flap wrinkles, dislocation, or epithelial ingrowth.
Patient Satisfaction Questionnaire
One year after surgery, the mean satisfaction scores for activities related to distance, intermediate, and near were evaluated on a scale of 0 to 100, where 0 meant “not at all satisfied” and 100 meant “fully satisfied.” The mean satisfaction scores for both groups are provided in Table 2. Spectacle independence was evaluated based on the percentage of patients who were completely free of glasses for a particular distance (Table 2). Five percent of patients in the myopia group and 8% of patients in the hyperopia group had minimal dysphotopsia, but no patient complained of severe glare or halos at 1 year.
Postoperative Patient Satisfaction and Dysphotopsia Scores (Mean ± SD)
Change in Higher Order Aberrations and Spherical Aberrations and Theoretical Depth of Focus
There was a significant increase in the postoperative corneal higher order aberrations, as measured using the Pentacam topographer in both groups for both dominant and non-dominant eyes. On the other hand, spherical aberrations (Z40) increased from preoperative values in the myopia group and changed from positive to negative values in the hyperopia group. These results were statistically significant (P < .05) (Table 3).
Change in Corneal HOA and SA (Mean ± SD)
According to the relationship between spherical aberration and depth of focus described by Benard et al24 and Yi et al,25 PRESBYOND Laser Blended Vision for hyperopia had an average increase in the depth of focus of 0.67 and 0.86 D for dominant eyes and 1.20 and 1.55 D for the non-dominant eyes. In myopic eyes, the shift in spherical aberration theoretically showed a calculated increase in the depth of focus of 0.37 and 0.48 D in dominant eyes and 0.12 and 0.16 D in non-dominant eyes (Table 3).
Two eyes in the hyperopia group underwent early enhancement for near vision at a mean period of 3 months. None of the eyes in either group underwent enhancement for distance vision or near vision at 1 year postoperatively.
In 2009, Reinstein et al19 published their outcomes of Laser Blended Vision in hyperopic eyes and showed that the hyperopic micro-monovision protocol was well tolerated and effective for treating patients with presbyopia in moderate to high hyperopia with corrections ranging up to +5.75 D. In our series of hyperopic eyes treated using PRESBYOND, we also observed good safety and efficacy of this protocol for treating hyperopia up to the limit of +5.00 D. The binocular UDVA in their study was 20/20 in 95% of patients and near vision was J2 in 81% of patients at a median follow-up of 12.5 months. Our results were comparable with theirs; the binocular UDVA in our study was 20/20 in 98% and J2 in 83% of patients at a mean follow-up of 12 months. The mean residual refractive error for the near eyes was also similar at −1.28 D in our study compared to −1.32 D in their study. However, the reported enhancement rate in their study was 22% (of which 50% were for the distance eye and 50% for the near eye) versus 3.17% in our data of hyperopic eyes, where all eyes had enhancement for the near eye and none for the distance eye. One reason for our comparatively lower enhancement rate could be that our mean preoperative hyperopic refractive error was lower (+1.75 ± 0.99 D) compared to theirs (+2.54 ± 1.16 D), and hence there was a greater possibility of regression at 1 year.
Our sample size was also relatively smaller (63 patients) compared to the 129 patients in their study. Patient-related factors could also play a role; some patients are less tolerant and would request an enhancement procedure for a smaller degree of residual refractive error, as low as for 0.50 D. We observed better tolerance to residual refractive error and most of our patients had adapted to it and did not ask for an enhancement procedure, even though 13% of them had the postoperative refraction off by more than 0.50 D. This may also be related to a slight difference in the mean age group between their study and our study; their cohort was slightly older (range: 44 to 66 years, median: 56 years) compared to ours (range: 40 to 62 years, mean: 52 years). Middle age hyperopia and failing accommodation due to changes in the crystalline lens would affect older individuals more than younger individuals, thus resulting in changes in refraction over time and a potential increase in chances of enhancement.26,27
Finally, as stated in their studies, Reinstein et al19,20 followed specific criteria for enhancement, such as a gain of two lines of UDVA and patients with cylinder of 0.75 D, even if UDVA was already 20/20. Their retreatment rate would have been lower had a threshold for UDVA and UNVA been applied to determine suitability for re-treatment.
Outcomes of Laser Blended Vision with the MEL 80 laser for myopic eyes have been reported by Reinstein et al20 in 155 patients, and the results were analyzed at a median period of 12.5 months. Another 3-month follow-up study was reported in a Chinese population including 40 patients who underwent Laser Blended Vision for simultaneous correction of myopia and presbyopia.28 In terms of UDVA, our results were comparable to both of these studies, where 97% of eyes achieved 20/20 binocular distance vision versus 98.5%20 and 98%28 in the other studies, respectively. However, in terms of binocular near vision, 89% of patients read J2 in our series compared to 95%20 and 95.6%28 in the other studies. Despite this, none of the eyes in our group had enhancement for either distance or near eyes at 1 year or earlier, in contrast to Reinstein et al,20 who reported an enhancement rate of 19% in their myopic series, which was probably influenced by similar factors stated above in the context of hyperopia. Our observations suggest slightly more predictable and stable results in the myopia group compared to the hyperopia group.
This is also reflected in the results of the patient satisfaction questionnaire in our study, where the near vision satisfaction was seen to be higher in the myopic group (95%) compared to the hyperopic group (89%) at the end of 1 year. This could be because some of the near eyes in the hyperopic group had high hyperopia (> +2.00 D), which is expected to slightly regress by 1 year, rendering the myopic target less negative and compromising the near vision. On the other hand, regression of the near eye in the myopic group would result in making the myopic target more negative, thus helping in maintenance of good near vision, although at a slight compromise of distance vision in the non-dominant eye. However, this does not lead to patient dissatisfaction, unless the distance eye is also affected. The patient satisfaction scores for distance and intermediate vision were comparable for both groups.
The effect of spherical aberrations on depth of focus has been investigated using adaptive optics systems by Rocha et al,29 who showed that the depth of focus increases in a linear manner with spherical aberrations up to ±0.6 µm, with less of an increase in the depth of focus with further degrees of induced spherical aberrations. Further experiments performed by Benard et al24 and Yi et al25 reported the relationship between spherical aberrations and depth of focus as 2.00 and 2.59 D/µm, respectively. Although the theoretical depth of focus achieved was larger in hyperopic eyes compared to myopic eyes in our study, near vision outcomes were better in the myopic group, probably due to the factors discussed above. Although the root mean square of higher order corneal and spherical aberrations in both the hyperopic and myopic groups increased significantly, it did not lead to poor visual quality and night vision, as inferred by the subjective patient questionnaire.
PRESBYOND Laser Blended Vision demonstrated excellent safety, efficacy, and stability in our 12-month outcomes in an Indian population, and seems to be a well-tolerated modality for simultaneous correction of myopia and hyperopia with presbyopia, without inducing significant side effects. The low rate of enhancement observed in our population particularly suggested good stability of achieved results, which may be considered as a favorable aspect related to this procedure.
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|Characteristic||Myopia (n = 38 Patients)||Hyperopia (n = 63 Patients)|
|Gender (male/female), no.||15/23||28/35|
|Age (y), mean ± SD (range)||48.82 ± 4.94 (42 to 65)||52.40 ± 4.83 (40 to 63)|
|Mean sphere (D), mean ± SD (range)||−3.02 ± 1.84 (−0.50 to −6.50)||1.51 ± 0.93 (+5.00 to +0.25)|
|Mean cylinder (D), mean ± SD (range)||−0.71 ± 0.60 (0 to −2.75)||0.47 ± 0.54 (+3.25 to 0.00)|
|Mean SE (D), mean ± SD (range)||−3.36 ± 1.86 (−0.75 to −7.50)||1.75 ± 0.99 (+5.00 to +0.25)|
Postoperative Patient Satisfaction and Dysphotopsia Scores (Mean ± SD)a,b
|Distance vision||98.18 ± 2.10||97.43 ± 2.78|
|Intermediate vision||99.47 ± 0.62||99.22 ± 0.75|
|Near vision||95.84 ± 2.71||89.75 ± 4.14|
|Spectacle independence (% of patients)|
| Distance vision||97% (37/38)||96% (60/63)|
| Intermediate vision||100% (38/38)||100% (63/63)|
| Near vision||95% (36/38)||89% (56/63)|
|Dysphotopsia score (% of patients)|
| Grade 0 (Nil)||95% (36/38)||92% (58/63)|
| Grade 1 (Mild)||5% (2/38)||8% (5/63)|
| Grade 2 (Moderate)||0% (0/38)||0% (0/63)|
| Grade 3 (Severe)||0% (0/38)||0% (0/63)|
Change in Corneal HOA and SA (Mean ± SD)
|Group||Preop HOA (µm)||Postop HOA (µm)||P||Preop Z40 (µm)||Postop Z40 (µm)||P||Shift in SA (Postop–Preop Z40)||Theoretical DOF Achieved (D)a||Theoretical DOF Achieved (D)b|
| Dominant eyes||0.46 ± 0.13||0.54 ± 0.25||< .001||0.26 ± 0.14||−0.08 ± 0.24||< .001||0.33 ± 0.22||0.67 ± 0.45||0.86 ± 0.58|
| Non-dominant eyes||0.49 ± 0.18||0.81 ± 0.37||< .001||0.23 ± 0.18||−0.37 ± 0.31||< .001||0.60 ± 0.27||1.20 ± 0.53||1.55 ± 0.69|
| Dominant eyes||0.42 ± 0.09||0.72 ± 0.29||< .001||0.23 ± 0.07||0.42 ± 0.13||.03||0.19 ± 0.16||0.37 ± 0.31||0.48 ± 0.40|
| Non-dominant eyes||0.42 ± 0.12||0.58 ± 0.16||< .001||0.24 ± 0.09||0.30 ± 0.12||.03||0.06 ± 0.13||0.12 ± 0.26||0.16 ± 0.33|
Mean Spherical Equivalent Refraction (Diopters) of Distance and Near Eyes Before and After All Treatmentsa
|Group||Preoperative||Intended After Treatment (Target)||Attempted||After Treatment|
| Distance||−3.34 ± 1.96 (−0.75 to −7.00)||+0.09 ± 0.24 (+0.54 to −0.65)||−3.43 ± 1.88 (−0.81 to −6.67)||+0.13 ± 0.32 (+0.75 to −0.50)|
| Near||−3.39 ± 1.79 (−0.80 to −7.50)||−1.41 ± 0.34 (−0.59 to −2.95)||−1.98 ± 1.89 (1.32 to −5.75)||−1.42 ± 0.33 (−0.88 to −2.50)|
| Distance||+1.71 ± 0.97 (+5.00 to +0.25)||+0.16 ± 0.22 (+0.81 to −0.59)||+1.55 ± 0.84 (+4.19 to +0.49)||−0.13 ± 0.24 (0.50 to −0.50)|
| Near||+1.78 ± 1.02 (+5.00 to +0.25)||−1.11 ± 0.25 (−0.62 to −1.60)||+2.89 ± 0.87 (+5.65 to +1.52)||−1.28 ± 0.31 (−0.63 to −2.00)|