Journal of Refractive Surgery

Original Article Supplemental Data

Contrast Sensitivity in Patients With Emmetropic Presbyopia Before and After Small-Aperture Inlay Implantation

Ling Lin, PhD; Corina van de Pol, OD, PhD; Srividhya Vilupuru, OD, PhD; Jay S. Pepose, MD, PhD

Abstract

PURPOSE:

To develop a normative contrast sensitivity function and examine the postoperative contrast sensitivity outcomes for emmetropic patients with presbyopia implanted with a KAMRA intracorneal inlay (AcuFocus Inc., Irvine, CA) in their non-dominant eyes.

METHODS:

A prospective, non-randomized, multicenter clinical trial was conducted on 507 patients between 45 and 60 years of age who were monocularly implanted with the KAMRA inlay. A predetermined subgroup of 335 patients in the contrast sensitivity substudy were measured preoperatively and postoperatively with the Functional Acuity Contrast Test (FACT) chart in the Optec 6500 Vision Tester (Stereo Optical Co., Chicago, IL) under monocular and binocular, photopic and mesopic without glare, and binocular mesopic with glare conditions each over four spatial frequencies (3, 6, 12, and 18 cycles per degree for photopic conditions and 1.5, 3, 6, and 12 cycles per degree for mesopic conditions). Normative ranges were developed using 1.96 standard deviations from the preoperative mean logCS (log10 unit of contrast sensitivity).

RESULTS:

The preoperative contrast sensitivity measurements were used to develop the normative contrast sensitivity curves. Postoperatively, contrast sensitivity was stable both monocularly and binocularly and average contrast sensitivity remained within the normative ranges. Postoperative contrast sensitivity was mildly reduced monocularly but not binocularly, and the ratio of area under logCS function comparing postoperative to preoperative values was above 90% for all but one condition.

CONCLUSIONS:

Normative contrast sensitivity curves for a presbyopic population are established to provide a referent in the investigation of the impact of other presbyopia-correcting ophthalmic procedures on contrast sensitivity.

[J Refract Surg. 2016;32(6):386–393.]

Abstract

PURPOSE:

To develop a normative contrast sensitivity function and examine the postoperative contrast sensitivity outcomes for emmetropic patients with presbyopia implanted with a KAMRA intracorneal inlay (AcuFocus Inc., Irvine, CA) in their non-dominant eyes.

METHODS:

A prospective, non-randomized, multicenter clinical trial was conducted on 507 patients between 45 and 60 years of age who were monocularly implanted with the KAMRA inlay. A predetermined subgroup of 335 patients in the contrast sensitivity substudy were measured preoperatively and postoperatively with the Functional Acuity Contrast Test (FACT) chart in the Optec 6500 Vision Tester (Stereo Optical Co., Chicago, IL) under monocular and binocular, photopic and mesopic without glare, and binocular mesopic with glare conditions each over four spatial frequencies (3, 6, 12, and 18 cycles per degree for photopic conditions and 1.5, 3, 6, and 12 cycles per degree for mesopic conditions). Normative ranges were developed using 1.96 standard deviations from the preoperative mean logCS (log10 unit of contrast sensitivity).

RESULTS:

The preoperative contrast sensitivity measurements were used to develop the normative contrast sensitivity curves. Postoperatively, contrast sensitivity was stable both monocularly and binocularly and average contrast sensitivity remained within the normative ranges. Postoperative contrast sensitivity was mildly reduced monocularly but not binocularly, and the ratio of area under logCS function comparing postoperative to preoperative values was above 90% for all but one condition.

CONCLUSIONS:

Normative contrast sensitivity curves for a presbyopic population are established to provide a referent in the investigation of the impact of other presbyopia-correcting ophthalmic procedures on contrast sensitivity.

[J Refract Surg. 2016;32(6):386–393.]

Contrast sensitivity is an important measure to study the effect of refractive procedures on quality of vision. It provides a dimension of visual quality distinct from visual quantity commonly assessed by high-contrast visual acuity, and it integrates both optical and neural processing components of vision in a single function.1,2 The clinical measurement of the contrast sensitivity function, such as the Functional Acuity Contrast Test (FACT) chart in the Optec 6500 Vision Tester (Stereo Optical Co., Chicago, IL) or the CSV-1000 Contrast Testing Instrument (VectorVision, Greenville, OH), is generally accomplished using a chart with sine wave gratings with a set of spatial frequencies and contrast steps under photopic and mesopic conditions with and without a glare source.

Contrast sensitivity under different lighting conditions provides particularly important information about quality of vision for presbyopic patients who are affected by age-related changes to their crystalline lens and neural processing, and for postoperative populations whose cornea or lens has gone through vision-correction procedures.2–5 Presbyopia is a direct consequence of the age-related loss of accommodation resulting from the crystalline lens' inability to focus at near vergence.6 According to the current estimates, more than 1 billion adults are affected by presbyopia worldwide.7 An approach to surgically correct presbyopia can be achieved by monocularly implanting a small-aperture intracorneal inlay into a lamellar pocket in the non-dominant eye. The KAMRA inlay (AcuFocus Inc., Irvine, CA) is designed to block unfocused peripheral light rays and reduce the size of the blur circle to provide increased depth of focus and an extended range of continuous vision expanding from near to far.8,9 Vilupuru et al. recently compared 6-month postoperative visual acuity and contrast sensitivity outcomes in patients implanted with a KAMRA inlay and patients implanted with multi-focal or accommodative intraocular lenses, and showed patients implanted with a KAMRA inlay generally had superior binocular contrast sensitivity outcomes while achieving comparable visual acuity results.10

Despite a large body of literature on contrast sensitivity,1,11–14 there is a need for a normative contrast sensitivity database that covers all contrast testing conditions for the presbyopic population. Most studies establishing contrast sensitivity norms either do not pertain to presbyopia population or do not test under mesopic or with-glare conditions. The purpose of this study was to establish normative contrast sensitivity curves for emmetropic presbyopes tested monocularly and binocularly under photopic and mesopic conditions with and without glare and compare preoperative versus postoperative contrast sensitivity outcomes through 36 months after KAMRA inlay implantation.

Patients and Methods

Patients and Inlay Design

In this prospective, non-randomized, multicenter, open-label, single-arm U.S. IDE clinical trial ( http://www.clinicaltrials.gov, NCT00819299 and NCT00850031), 507 consecutive eyes of 507 patients at 24 clinical sites (15 United States and 9 non-United States) were implanted with the KAMRA intracorneal inlay in their non-dominant eyes. Patients provided informed consent before being screened for eligibility and participation in the study. The study was performed in accordance with the tenets of the Declaration of Helsinki and was approved by the institutional review board or the ethics committee of each respective investigational site.

Patients were eligible for inclusion in the clinical trial if they were naturally emmetropic and presbyopic, between 45 years and 60 years old, and had corrected distance visual acuity (CDVA) of at least 20/20 in both eyes. The eye to be implanted had uncorrected near visual acuity between 20/40 and 20/100 and a preoperative spherical equivalent cycloplegic refraction between +0.50 and −0.75 diopters (D) with no more than 0.75 D of refractive cylinder.

Four hundred patients from 11 U.S. sites and 8 non-U.S. sites initially participated in the contrast sensitivity subgroup study. Three hundred thirty-five patients were analyzed and presented in this study, whereas 65 patients from one U.S. site were excluded from analysis due to inconsistent testing procedures. Study subgroups were predetermined before study initiation.

The design of the KAMRA inlay and the surgical preparation and technique for KAMRA inlay implantation have been reported in detail.15 The KAMRA inlay is made from a highly biocompatible material (polyvinylidene fluoride) and is proven to be stable in the eye.16 The inlay is 6 µm thick, has a 3.8-mm outer diameter with 1.6-mm inner diameter, is formed with a 7.5-mm spherical radius, and is microperforated with 8,400 holes between 5 and 11 µm in diameter allowing for 5% light transmission through the annulus of the inlay.

Contrast Sensitivity Testing

Contrast sensitivity was measured using slides of the FACT chart within the Optec 6500 Vision Tester (Figure A, available in the online version of this article). The charts were back-lit and the luminance was calibrated to 85 and 3 cd/m2 (±5% per manufacturer's guidelines) for photopic and mesopic testing, respectively. All extraneous illumination outside the testing unit was minimized. For testing with glare, a 28-lux glare source was added. Patients were tested under all photopic conditions first, then dark-adapted for 5 minutes prior to mesopic conditions, and finally tested with the glare source. Testing was performed with the patients' CDVA.


The FACT chart in the Optec 6500 vision tester (Stereo Optical Co., Chicago, IL) that consists of sine-wave grating patches at 9 contrast levels and 5 spatial frequencies. The corresponding log10 unit of contrast of sensivitity (logCS) scores for the FACT chart are presented. This demonstration the FACT chart reprinted with permission from Vision Sciences Research Corporation.

Figure A.

The FACT chart in the Optec 6500 vision tester (Stereo Optical Co., Chicago, IL) that consists of sine-wave grating patches at 9 contrast levels and 5 spatial frequencies. The corresponding log10 unit of contrast of sensivitity (logCS) scores for the FACT chart are presented. This demonstration the FACT chart reprinted with permission from Vision Sciences Research Corporation.

Five contrast sensitivity conditions were chosen to assess the quality of vision before and after the KAMRA inlay implantation. The conditions were monocular and binocular photopic contrast sensitivity without glare, monocular and binocular mesopic contrast sensitivity without glare, and binocular mesopic contrast sensitivity with glare. These five conditions were measured preoperatively and postoperatively at 3, 6, 12, 24, and 36 months. Monocular photopic with glare and monocular mesopic with glare conditions were added later in the clinical trial and were therefore only tested on a subset of 142 patients at the 36-month visit.

Four spatial frequencies were tested in each condition: 3, 6, 12, and 18 cycles per degree (cpd) for photopic conditions and 1.5, 3, 6, and 12 cpd for mesopic conditions. Test results were represented in log10 unit of contrast sensitivity (logCS). The standard logCS scores for the corresponding grating patches at each spatial frequency for the FACT chart are provided in Figure A. Patients who were unable to see any patches at a particular spatial frequency were assigned a logCS score of 0.3 less than the lowest logCS score that corresponds to the first patch with the highest contrast level for that spatial frequency.12,17

Other Clinical Measurements

Monocular and binocular uncorrected and corrected visual acuities were measured using high contrast visual acuity charts in the same Optec 6500 Vision Tester at distance (6 m), intermediate (80 cm), and near (40 cm). Manifest refractive spherical equivalent and CDVA was determined by “midpoint refraction” (ie, the arithmetic average of the most plus refraction and most minus refraction) to establish the arithmetic center of the depth of focus. Pupil sizes were measured with a pupillometer under full room illumination for photopic pupil size and in a dark room after 5 minutes of dark adaption for mesopic pupil size.

Data Analysis

The area under the log contrast sensitivity function (AULCSF) was computed. The logCS scores were plotted against the log10 units of the four spatial frequencies measured in each testing condition, and the curve, without smoothing, was integrated between the minimum and maximum spatial frequencies. The resulting value defined AULCSF, a single quantity used to characterize the overall visual performance of the eye in each testing condition.18

Statistical analysis was performed using the JMP statistical package, version 11.2 (SAS Institute, Inc., Cary, NC). Correlation tests were conducted on logCS data using analysis of variance. There was minor skewing to the left and minor positive excess kurtosis in logCS distributions; however, with a large sample size in each contrast sensitivity condition group, the analysis of variance test was considered sufficiently robust. Categorical parameters were compared by Pearson chi-square test. A P value of less than .05 was considered statistically significant. P values have not been adjusted for multiple comparisons.

Results

Demographics and Baseline Characteristics

Among the 335 patients who participated in the contrast sensitivity subgroup, there were 159 (47%) females and 176 (53%) males. The mean ± standard deviation age of the patients was 51.6 ± 3.6 years (range: 45 to 60 years). The race distribution was predominantly white (303, 90.4%), followed by Asian (22, 6.6%), Hispanic (5, 1.5%), African American (2, 0.6%), and other (3, 0.9%). There were 224 (66.9%) left eyes implanted and 111 (33.1%) right eyes implanted. Preoperative mean uncorrected distance visual acuity (UDVA) was 51.8 ± 3.7 letters (approximately 20/20, range: 38 to 55 letters). Preoperative uncorrected near visual acuity (UNVA) was 26.1 ± 3.8 letters (approximately 20/63 or J-8, range: 15 to 32 letters). Preoperative CDVA was 54.2 ± 1.4 letters (approximately 20/16, range: 48 to 55 letters). Preoperative manifest refractive spherical equivalent was +0.09 ± 0.29 D (range: −0.75 to +0.63 D). The preoperative near add power was +1.90 ± 0.30 D (range: +1.00 to +2.50 D). The mean photopic pupil size was 4.4 ± 0.9 mm (range: 2.4 to 7.1 mm). The mean mesopic pupil size was 5.6 ± 0.8 mm (range: 3.5 to 7.5 mm).

Contrast Sensitivity Measurements

Preoperative contrast sensitivity measurements are shown in Figure 1. The logCS curves were parallel between two photopic conditions, similarly for the three mesopic conditions. Correlation tests have confirmed that logCS is linearly correlated between different conditions (all pairs, P < .0001, R2 between 0.2 and 0.6). The upper and lower limits of normative values were developed from preoperative logCS measurements by taking 1.96 standard deviations (SDs) from the mean at each spatial frequency in each testing condition (Table 1).19


Preoperative mean log10 unit of contrast sensitivity (logCS) scores in monocular/binocular photopic/mesopic without glare and binocular mesopic with glare conditions. Curves were slightly offset for ease of comparison. cpd = cycles per degree

Figure 1.

Preoperative mean log10 unit of contrast sensitivity (logCS) scores in monocular/binocular photopic/mesopic without glare and binocular mesopic with glare conditions. Curves were slightly offset for ease of comparison. cpd = cycles per degree


Preoperative Mean ± SD logCS Scores and Normative Values

Table 1:

Preoperative Mean ± SD logCS Scores and Normative Values

Postoperative contrast sensitivity measurements are shown in Figure 2. In each of the binocular conditions (photopic without glare, mesopic without glare, mesopic with glare), the postoperative logCS curves overlapped with the preoperative curve, indicating a minimal change after surgery that remained stable for 3 years postoperatively. Under monocular photopic and mesopic without glare conditions, there was some reduction from preoperative to postoperative; however, the mean logCS appeared stable for 3 years postoperatively. The postoperative mean logCS curves were well within the high and low normal boundaries. Monocular photopic and mesopic with glare conditions were measured only at 36 months, and the mean logCS results were as follows (N = 142): 1.81 ± 0.24, 1.81 ± 0.26, 1.47 ± 0.34, and 0.95 ± 0.40 at 3, 6, 12, and 18 cpd and 1.37 ± 0.30, 1.49 ± 0.30, 1.37 ± 0.32, and 0.94 ± 0.29 at 1.5, 3, 6, and 12 cpd, respectively. The results were comparable to but slightly lower than their respective without glare conditions. This would be generally anticipated with glare testing.20


(A) Log10 unit of contrast sensitivity (logCS) function in monocular photopic without glare condition before and after KAMRA inlay (AcuFocus Inc., Irvine, CA) surgery. The solid curves represent mean logCS and the error bars represent ± one standard deviation (SD). The dashed lines represent high and low normative values established from preoperative means in this study. Curves were slightly offset for ease of comparison. (B) LogCS function in binocular photopic without glare condition before and after KAMRA inlay surgery. (C) LogCS function in monocular mesopic without glare condition before and after KAMRA inlay surgery. (D) LogCS function in binocular mesopic without glare condition before and after KAMRA inlay surgery. (E) LogCS function in binocular mesopic with glare condition before and after KAMRA inlay surgery. cpd = cycles per degree

Figure 2.

(A) Log10 unit of contrast sensitivity (logCS) function in monocular photopic without glare condition before and after KAMRA inlay (AcuFocus Inc., Irvine, CA) surgery. The solid curves represent mean logCS and the error bars represent ± one standard deviation (SD). The dashed lines represent high and low normative values established from preoperative means in this study. Curves were slightly offset for ease of comparison. (B) LogCS function in binocular photopic without glare condition before and after KAMRA inlay surgery. (C) LogCS function in monocular mesopic without glare condition before and after KAMRA inlay surgery. (D) LogCS function in binocular mesopic without glare condition before and after KAMRA inlay surgery. (E) LogCS function in binocular mesopic with glare condition before and after KAMRA inlay surgery. cpd = cycles per degree

Ceiling and Floor Effects

The ceiling and floor effects of the FACT chart are well documented in the published literature.14,21 We examined the data for potential ceiling and floor effects, for which we calculated the percentages of patients seeing the highest contrast sensitivity patch or seeing zero patches at each spatial frequency in monocular mesopic without glare condition (Figure B, available in the online version of this article). At every visit, the proportion of patients who saw the highest contrast sensitivity patch (the “ceiling”) was above 10% at low spatial frequencies and close to 1% at high spatial frequencies. The proportion of patients who did not see any contrast sensitivity patches (the “floor”) was almost 0% at low spatial frequencies and approximately 20% at high spatial frequencies. There was no statistically significant change over time in the proportion of patients seeing the highest contrast sensitivity patch at any spatial frequency (Pearson chi-square test, all P ≥ .2795). There was a significant increase after surgery in the percentage of patients seeing zero patches at 12 cpd (Pearson chi-square test, P < .0001), but not at 1.5 to 6 cpd (Pearson chi-square test, all P > .05). The percentage of patients seeing zero patches remained stable across postoperative visits (Pearson chi-square test, P = .3819 from 6 to 36 months).


(A) Percentage of patients who saw the highest contrast sensitivity patch (the “ceiling”) in monocular mesopic without glare condition pre-operatively and at various postoperative visits. (B) Percentage of patients who did not see any contrast sensitivity patches (the “floor”) in monocular mesopic without glare condition preoperatively and at various postoperative visits.

Figure B.

(A) Percentage of patients who saw the highest contrast sensitivity patch (the “ceiling”) in monocular mesopic without glare condition pre-operatively and at various postoperative visits. (B) Percentage of patients who did not see any contrast sensitivity patches (the “floor”) in monocular mesopic without glare condition preoperatively and at various postoperative visits.

AULCSF

The mean AULCSF for each testing condition is presented at preoperative and postoperative visits (Tables 23). To examine the stability of AULCSF across time, the ratio of postoperative AULCSF against preoperative AULCSF (“post/pre ratio”) were computed and averaged across patients at each visit (Tables 23). The results show that for all photopic conditions and all binocular conditions, the average post/pre ratios were above 90%. For monocular mesopic without glare condition, the average post/pre ratios varied between 87% and 91% from 3 to 36 months. These ratios indicate that the loss in the overall contrast sensitivity function was no more than 13% on average in any testing condition. For monocular photopic/mesopic with glare conditions, the post/pre ratios were unavailable because these conditions were not measured preoperatively.


Preoperative and Postoperative AULCSF for Photopic Conditions

Table 2:

Preoperative and Postoperative AULCSF for Photopic Conditions


Preoperative and Postoperative AULCSF for Mesopic Conditions

Table 3:

Preoperative and Postoperative AULCSF for Mesopic Conditions

Discussion

Normative Contrast Sensitivity Establishment

Contrast sensitivity normative values from this study are compared with other comparable sources in Figure C (available in the online version of this article). One comparable set was provided by Stereo Optical Co. for users of the Optec 6500 Vision Tester with the FACT chart (presented as the “Optec” curves). Two other sets for the 20 to 55 years age group and the 50 to 75 years age group, respectively, were provided by VectorVision for the CSV-1000 chart (presented as the “CSV1000, 20–55” and “CSV1000, 50–75” curves).12 The contrast sensitivity normative values developed in this study (the “current study” curves) and the “Optec” curves rank in the middle of the four sources, slightly higher than the “CSV1000, 50–75” curves and slightly lower than the “CSV1000, 20–55” curves. Both the current study and Stereo Optical Co. use the FACT chart for contrast sensitivity testing, and the normative contrast sensitivity curves appeared parallel between the two sources with the current study presenting a wider range between its “Low Normal” curve and “High Normal” curve. However, without sufficient knowledge of the development process by Stereo Optical Co. or their applicable age range, the cause for the range difference between these two sources cannot be determined. In the mesopic without glare condition, the current study presented both “High Normal” and “Low Normal” curves slightly higher than the “CSV1000, 20–55” curves. It should be noted that the “CSV1000, 20–55” curves tested across 3 to 18 cpd and the current study tested across 1.5 to 12 cpd.


Normative log10 unit of contrast sensitivity (logCS) curves from the current study and related sources for monocular (A) photopic and (B) mesopic without glare condition. Curves were slightly offset for ease of comparison. cpd = cycles per degree; N/A = not available

Figure C.

Normative log10 unit of contrast sensitivity (logCS) curves from the current study and related sources for monocular (A) photopic and (B) mesopic without glare condition. Curves were slightly offset for ease of comparison. cpd = cycles per degree; N/A = not available

There have been a few methods to derive normative values based on preoperative contrast sensitivity data, such as using regions encompassing 75% and 90% of their sample around the median contrast sensitivity values,11 or using the 95% confidence intervals of the mean to compare the control group and the comparison group,22 or using the mean contrast sensitivity ± 2 SD of their age- and sex-matched healthy patients to determine their “normal reference population” for the comparison group.23 These methods are similar in principle to the method used in this study setting the normative boundaries as ±1.96 SD from the mean contrast sensitivity values.19 It should be stressed that practitioners should always take into account any differences in testing methods and patient population before using the contrast sensitivity normative values published in the literature. For example, contrast sensitivity data reported in this study were measured with patients' CDVA, whereas refractive errors could have created more variability to those contrast sensitivity norms measured with patients' UCVA in other reports.11

Floor Effects in Contrast Sensitivity Testing

The impact of the floor effect on group means was taken into consideration in this study by assigning a value of 0.3 log contrast sensitivity below the lowest contrast sensitivity score for patients with zero patches seen, similar to some reports on contrast sensitivity measured with the CSV-1000 Contrast Testing Instrument.12,17 Another method, such as assigning half of the lowest logCS value to patients with zero patches seen,13,22 may lead to a slightly different logCS score but essentially uses the same principle. All of these methods strive to more closely estimate the contrast sensitivity compared to other methods either excluding the patients who could not see any patches or assigning them with the lowest logCS score, both of which could overestimate the group means, or compared to another method of assigning those patients a zero value, which could underestimate the group means.

Contrast Sensitivity Reduction After Kamra Inlay Implantation

Although there was a mild reduction in monocular contrast sensitivity, there was minimal reduction in binocular contrast sensitivity. For the monocular results, the postoperative contrast sensitivity was maintained within the normative range established from preoperative means throughout 36 months postoperatively. It has been well documented that there is significant and prolonged contrast sensitivity reduction after radial keratotomy and photorefractive keratectomy through 6 months or even 1 year after surgery.24,25 It has also been reported that there was some contrast sensitivity reduction after LASIK but the postoperative contrast sensitivity levels returned to preoperative levels 1 month postoperatively.26 Using the CSV-1000 Contrast Testing Instrument to measure contrast sensitivity, Mutyala et al. found 12 cpd to be the most sensitive frequency for detecting reduction in monocular contrast sensitivity after LASIK, while noting some reduction in contrast sensitivity at the intermediate and higher frequencies (6, 12, and 18 cpd).26 In this study, the monocular contrast sensitivity in the eyes after KAMRA surgery showed mild reduction that appeared to be on the same scale as postoperative reduction after LASIK. Comparing the KAMRA inlay to a multifocal intraocular lens, patients implanted with KAMRA inlay also demonstrated superior contrast sensitivity at 6 months after surgery.10

When the pupil contracts to approximately 1.55 mm after instillation of 1% pilocarpine, the diffraction from the constricted pupil is reported to mildly reduce contrast sensitivity.27 This may in part explain the monocular contrast sensitivity reduction from the inlay because it uses a small central aperture of 1.6 mm to create extended depth of focus. Binocular summation effect is also found to be reduced with artificial pupils of 2 mm most consistently at low contrast (5%) and by a varying degree in most other suprathreshold conditions.28 It is conceivable that the reduced binocular summation effect could be one of the contributing factors to the minimal binocular contrast sensitivity reduction from the inlay; nevertheless, the magnitude of this change is small, less than 2% to 3% considering the average post/pre ratio of AULCSF.

One other factor possibly affecting contrast sensitivity in this study is inlay centration. The inlay was qualitatively assessed to be centered relative to the first Purkinje reflex on the cornea for most patients; thus, we have little quantitative evidence to support or refute whether contrast sensitivity is affected by the centration of the KAMRA inlay.

Conclusion

We established the contrast sensitivity normative values with the view-in FACT chart in five testing conditions for the presbyopic population based on a large sample. To our knowledge, we are the first to develop and publish contrast sensitivity normative values for monocular and binocular mesopic with and without glare conditions for the young presbyopic population. The results provide the ophthalmic care community reference contrast sensitivity curves to use in detailed vision quality assessment of presbyopic patients in varied viewing conditions.5 The postoperative contrast sensitivity after KAMRA surgery has shown great stability after surgery both monocularly and binocularly, with mild reduction in monocular contrast sensitivity and minimal reduction in binocular contrast sensitivity. However, the postoperative contrast sensitivity remained within the normative ranges even with the reductions. In addition, these reductions were comparable to or better than postoperative results from other surgical vision-correction procedures such as the multifocal intraocular lens.10

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Preoperative Mean ± SD logCS Scores and Normative Values

Spatial Frequency (cpd)Mean ± SDLow NormalHigh Normal
Monocular photopic without glare
  31.847 ± 0.2121.432.26
  61.941 ± 0.2031.542.34
  121.648 ± 0.2341.192.11
  181.231 ± 0.2890.661.80
Binocular photopic without glare
  31.98 ± 0.1641.662.30
  62.08 ± 0.161.772.39
  121.804 ± 0.2071.402.21
  181.413 ± 0.2510.921.90
Monocular mesopic without glare
  1.51.679 ± 0.1981.292.07
  31.872 ± 0.1951.492.25
  61.856 ± 0.2281.412.30
  121.413 ± 0.2980.832.00
Binocular mesopic without glare
  1.51.823 ± 0.1751.482.17
  31.961 ± 0.1721.622.30
  61.958 ± 0.2031.562.36
  121.523 ± 0.270.992.05
Binocular mesopic with glare
  1.51.65 ± 0.2281.202.10
  31.79 ± 0.2311.342.24
  61.80 ± 0.2421.332.28
  121.365 ± 0.3140.751.98

Preoperative and Postoperative AULCSF for Photopic Conditions

AULCSFMonocular Photopic Without GlareBinocular Photopic Without GlareMonocular Photopic With Glare



Mean ± SDPost/Pre RatioMean ± SDPost/Pre RatioMean ± SDPost/Pre Ratio
Preoperative1.36 ± 0.151.48 ± 0.12
3 months1.24 ± 0.1891%1.45 ± 0.1398%
6 months1.26 ± 0.1993%1.46 ± 0.1299%
12 months1.29 ± 0.1795%1.48 ± 0.11100%
24 months1.29 ± 0.1895%1.48 ± 0.12100%
36 months1.28 ± 0.1894%1.47 ± 0.1499%1.25 ± 0.2

Preoperative and Postoperative AULCSF for Mesopic Conditions

AULCSFMonocular Mesopic Without GlareBinocular Mesopic Without GlareBinocular Mesopic With GlareMonocular Mesopic With Glare




Mean ± SDPost/Pre RatioMean ± SDPost/Pre RatioMean ± SDPost/Pre RatioMean ± SDPost/Pre Ratio
Preoperative1.59 ± 0.161.68 ± 0.151.54 ± 0.19
3 months1.38 ± 0.2387%1.63 ± 0.1697%1.47 ± 0.295%
6 months1.4 ± 0.2488%1.65 ± 0.1598%1.49 ± 0.297%
12 months1.43 ± 0.2390%1.66 ± 0.1599%1.49 ± 0.297%
24 months1.44 ± 0.2391%1.67 ± 0.1699%1.5 ± 0.2197%
36 months1.42 ± 0.2289%1.65 ± 0.1698%1.48 ± 0.296%1.21 ± 0.24
Authors

From AcuFocus Inc., Irvine, California (LL, SV); Marshall B. Ketchum University, Southern California College of Optometry, Fullerton, California (CvdP); and The Pepose Vision Institute and the Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri (JSP).

Supported by AcuFocus Inc., Irvine, California.

Drs. Lin and Vilupuru are employees of AcuFocus Inc., Irvine, California. Dr. van de Pol is a consultant for AcuFocus Inc., Irvine, California. Dr. Pepose is a consultant for AcuFocus Inc., Irvine, California; Abbott Medical Optics, Santa Ana, California; Allergan, Irvine, California; Bausch & Lomb, Irvine, California; Envisia Therapeutics, Morrisville, North Carolina, and TearLab, San Diego, California; and has received lecture fees from AcuFocus Inc., Irvine, California; Bausch & Lomb, Irvine, California; and TearLab, San Diego, California.

AUTHOR CONTRIBUTIONS

Study concept and design (LL, CvdP, JSP); data collection (LL, CvdP); analysis and interpretation of data (LL, CvdP, SV, JSP); writing the manuscript (LL); critical revision of the manuscript (LL, CvdP, SV, JSP); statistical expertise (LL)

The authors thank Daniel Kraus of Würzburg, Germany, for assistance with data analysis and data visualization using his XL Toolbox add-in for Excel 2010, version 14.0.6129.5000.

Correspondence: Ling Lin, PhD, AcuFocus Inc., 32 Discovery, Suite 200, Irvine, CA 92618. E-mail: llin@acufocus.com

Received: July 22, 2015
Accepted: December 09, 2015

10.3928/1081597X-20160217-04

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