Visual Acuity Outcomes in Diseases Associated with Reduced Visual Acuity: An Analysis of the National Health Insurance Service Database in Korea.

Visual acuity declines with age, and disease-related visual acuity changes vary. We evaluated factors affecting visual acuity and age-related visual acuity in diseases associated with reduced visual acuity such as hypertension, diabetes mellitus (DM), glaucoma, and diabetic retinopathy (DR). The Korean National Health Insurance Service 2015-2016 data were analyzed for age-related visual acuity changes and prevalence of diseases associated with reduced visual acuity. Among 993,062 participants, the prevalence rates of hypertension, DM, glaucoma, and DR were 27.0%, 15.1%, 13.8%, and 2.7%, respectively. Despite having the lowest prevalence, DR alone or DR with hypertension and glaucoma resulted in low visual acuity. Correlation analysis between disease frequency and mean age-related visual acuity revealed higher positive correlations in DR and hypertension than in DM and glaucoma, indicating lower visual acuity. Odds ratios for low visual acuity in cases including one disease such as hypertension, DM, glaucoma, and DR were 1.73, 1.23, 1.04, and 1.52, respectively. The prevalence and number of diseases associated with reduced visual acuity increased with age, and visual acuity decreased. The leading causes of vision loss were DR as a single disease and hypertension as a concomitant disease. Therefore, age-related vision management, through periodic eye examination and correction with age, should be performed along with management of diabetes and hypertension.

Comparison of image-based quantification methods in evaluating fixation stability using a remote eye tracker in abnormal phoria.

OBJECTIVE: This study was performed to establish a quantitative evaluation and comparison of fixation stability, as measured by an eye tracker, using image-based areas determined by the bivariate contour ellipse area (BCEA), kernel density estimation (KDE), and Scanpath methods. METHODS: This prospective cross-sectional study included 45 and 20 participants with abnormal and normal phoria, respectively. Eye movements were recorded using a remote eye tracker and were plotted using RStudio software. Image-based areas were evaluated using ImageJ software. RESULTS: The image-based areas used to evaluate fixation stability exhibited decreasing stability in the abnormal phoria group in the following order: KDE with ±1 standard deviation (SD), BCEA with ±1 SD, KDE with ±2 SD or Scanpath, and BCEA with ±2 SD. The BCEA tended to be overestimated, and the KDE tended to be underestimated at high density. The Scanpath method had a very high probability area because the area spans all gaze points. CONCLUSIONS: Fixation stability could be quantified as image-based areas by the KDE, BCEA, and Scanpath methods. Our findings suggest that fixation stability may be evaluated using one or more methods.

Quantitative Evaluation of the Association Between Fixation Stability and Phoria During Short-Term Binocular Viewing.

Purpose: Fixation stability for binocular anomalies with a phoria cannot be detected by direct observations. This study aimed to quantitatively evaluate fixation stability using an eye tracker rather than direct directions in binocular vision with abnormal and normal phorias. Methods: Thirty-five and 25 participants with abnormal and normal phoria, respectively, were included in the study. The horizontal and vertical gaze points and convergence were recorded for 10 s using a remote eye tracker while binocularly viewing a target on a display screen 550 mm away. Fixation stability was quantified using bivariate contour ellipse areas (BCEA). Results: The fixation stability for all participants-based evaluations as a single cluster in the abnormal phoria group was lower than that in the normal phoria group (p = 0.005). There was no difference between the two groups in the evaluation based on the BCEA for each participant-based evaluation (p = 0.66). Fixation stability was also more related to convergence for the abnormal phoria group than for the normal phoria group (r = 0.769, p < 0.001; r = 0.417, p = 0.038, respectively). Conclusion: As the first study to evaluate fixation stability using an eye-tracker to differentiate between abnormal and normal phoria for non-strabismus, these findings may provide evidence for improving the evaluation of binocular vision not detected with clinical diagnostic tests.

The effect of uncorrected ametropia on ocular torsion induced by changes in fixation.

BACKGROUND AND OBJECTIVE: Ocular torsion, the eye movements to rotating around the line of sight, has not been well investigated regarding the influence of refractive errors. The purpose of this study was to investigate the effect of uncorrected ametropia on ocular torsion induced by fixation distances. METHODS: Seventy-two subjects were classified according to the type of their refractive error, and ocular torsion of the uncorrected eye was compared based on changes induced by different fixation distances. Ocular torsion was measured using a slit-lamp biomicroscope equipped with an ophthalmic camera and a half-silvered mirror. RESULTS: In all groups, excyclotorsion values increased as the fixation distance decreased, but the myopia and astigmatism groups had larger amounts of ocular torsion than the emmetropia group. In addition, as the amount of uncorrected myopia and astigmatism increased, the amount of ocular torsion increased. CONCLUSION: Since the amount of ocular torsion caused by a change to a shorter fixation distance was larger when the refractive error was uncorrected, we suggest that ametropia should be fully corrected in patients frequently exposed to ocular torsion due to changes in fixation distance.

Measurement of ocular counter-roll using iris images during binocular fixation and head tilt.

OBJECTIVE: To compare the ocular counter-roll (OCR) measured using iris images during binocular fixation and head tilt with OCR measured via fundus photography. METHODS: Fifty-three healthy college students participated in this study. The mean OCR was measured by collection of iris images and fundus images under seven head tilt conditions (0 degrees; 10, 20, and 30 degrees right; and 10, 20, and 30 degrees left). Three iris images (crossed pupil center, pupil center, and pupil periphery) were taken using a slit-lamp biomicroscope with an ophthalmic camera and a half-silvered mirror; fundus images were collected via fundus photography. The mean OCR values were compared between images taken with each method. RESULTS: No iris images or head tilt conditions revealed any significant differences in mean OCR comparison with fundus images. The mean difference in OCR was smallest, and the correlation was greatest, between the crossed pupil center and fundus images. CONCLUSION: A half-silvered mirror and iris images can replace fundus photography for the measurement of OCR.

Differences in the optical properties of photochromic lenses between cold and warm temperatures.

The aim of our study was to quantitatively evaluate the optical properties of photochromic lenses available on the market under cold and warm temperatures corresponding to the winter and summer seasons. The transmittance of 12 photochromic lenses from five manufacturers was measured using an UV/VIS spectrophotometer at cold (6 ± 2°C) and at warm (21 ± 2°C) temperatures. Transmittances were recorded from 380 to 780 nm and at the wavelength with maximum absorbance, which was calculated from the transmittance. The characteristics of the lenses were evaluated by examining changes in the optical properties at colorless and colored states and in the fading rate depending on temperature. The wavelength with maximum absorbance for photochromic lenses at the cold temperature showed a shorter shift than that at the warm temperature. The photochromic properties at the cold temperature were 11.5% lower for transmittance, 1.4 times higher for the change in optical density, and 1.2 times higher for the change in transmittance in the colored and colorless states, optical blocking % ratio, and change in luminous transmittance as compared to those at the warm temperature in the colored state. The fading rates based on the half-life time at the cold temperature were from 2.7 to 5.4 times lower than those at the warm temperature. The fading time until 80% transmittance was 6.4 times longer at the cold as compared to that at the warm temperature. There were significant differences in the optical properties of the photochromic lenses in terms of an absorbance at a shorter wavelength, a lower transmittance, a higher optical density, optical blocking % ratio, and luminous transmittance at the cold as compared to the warm temperature. Hence, it is necessary to provide consumers with information on photochromic optical properties, including the transmittance in colored and colorless states, and the fading rates at temperatures corresponding to the summer and winter seasons for each product.

Fusional Single Vision with Prism-induced Vergence Has More Influence than Diplopia on Postural Stability.

SIGNIFICANCE: Prism-induced convergence and vertical vergence for maintaining binocular fusion induced postural instability to a greater extent than diplopic conditions. This finding has important implication in relation to postural control of patients with large exophoria or vertical phoria in optometric clinic. PURPOSE: The purpose of this study was to examine whether binocular single vision with prism-induced horizontal and vertical vergence and diplopia might affect the static postural stability. METHODS: Forty-two subjects with a mean ± standard deviation age of 23.79 ± 2.81 years were enrolled in this study. To simulate convergence and divergence, base-in and base-out (BO) prisms of 4 and 8 Δ were added, respectively. To simulate vertical vergence, vertical prism of 2 Δ was added in a trial frame that corrected for the subject's refractive error during far distance (6 m) gaze. The prism power necessary to break fusion in each subject was detected and applied to induce diplopia in horizontal and vertical directions. Indices of general instability and sway power were measured under visual conditions using Tetrax and compared with normal viewing without the prism. Correlations between general instability indices and the ranges of break point in convergence and divergence were analyzed. RESULTS: Postural instability was increased significantly when convergence induced by BO 4 and 8 Δ and vertical vergence induced by 2 Δ were stimulated. The correlation coefficient between ranges of BO break point and indices of general instability was -0.308 in the BO 4 Δ and -0.306 in the BO 8 Δ condition. CONCLUSIONS: Although binocular input is recognized as an important factor in postural stability, binocular input with excessively stimulated convergence and vertical vergence during a far distance gaze is a latent factor affecting postural stability. On the other hand, diplopia did not influence postural stability.

Receiver operating characteristic curve analysis of clinical signs for screening of convergence insufficiency in young adults.

Convergence insufficiency (CI) is a dysfunction of binocular vision that is associated with various signs and symptoms in near work. However, CI screening is performed less frequently in adults than in children. We aimed to evaluate the ability of screening tests to discriminate CI from other binocular vision anomalies and normal binocular vision in young adults. One hundred eighty-four university students (age, 18-28 years) who underwent an eye examination due to ocular discomfort were included. Near point of convergence (NPC), phoria, accommodative amplitude, fusional vergence, the ratio of accommodative convergence to accommodation, relative accommodation, binocular accommodative facility, vergence facility, and the values corresponding to Sheard's and Percival's criteria were evaluated. Receiver operating characteristic (ROC) curve analysis for each test was also performed. The prevalence of CI ranged from 10.3% to 21.2%, depending on the signs and the presence of CI associated with accommodative disorders. Assessments based on NPC, Sheard's criterion, and Percival's criterion showed high discriminative ability, with the ability being higher between the CI and normal binocular vision groups than between the CI and non-CI groups. Sheard's criterion showed the highest diagnostic performance in discriminating CI with three signs from the non-CI group. The cut-off values were 7.2 cm for NPC, -0.23 to 1.00 for Sheard's criterion, and -4.00 to -2.33 for Percival's criterion. Our results suggest that the use of Sheard's criterion with NPC shows high performance for screening of CI.

Effect of induced hyperopia on fall risk and Fourier transformation of postural sway.

BACKGROUND AND PURPOSE: Fall accidents are a social challenge in Korea and elsewhere. Most previous studies have focused on the effects of reduced visual acuity due to myopia on falls and body balance. The objective of this study was to investigate whether uncorrected hyperopia was a major risk factor for falls and to establish whether the risk of falls was absolutely correlated with visual acuity. METHODS: Fifty-one young subjects with a mean age of 22.75 ± 2.13 years were enrolled in this study. To induce hyperopic and myopic refractive errors, spherical lenses of ±1.0-6.0 D (1.0 D stepwise) were used. Under each induced condition, fall risk index and sway power were assessed via Fourier transformation of postural sway using a TETRAX system. RESULTS: The fall risk index for eyes-closed was significantly greater than that of eyes-open with full correction (t = -5.876, p < 0.05). The fall risk index increased significantly from hyperopia induced with -4.0 D lenses (with visual acuity of 0.69 ± 0.32) compared to eyes-open with full correction (F = 3.213, p < 0.05). However, there was no significant change in the induced myopia conditions, despite a drastic decline in decimal visual acuity. Sway power increased significantly in the low-to-medium frequency band derived from the peripheral vestibular system when hyperopia was induced. A significant difference was detected in hyperopia induced with -6.0 D lenses compared to eyes-open with full correction (F = 4.981, p = 0.017). CONCLUSION: An uncorrected hyperopia rather than myopia may increase the risk of falls, although eyes may show normal visual acuity due to the inherent accommodation mechanism. Our findings suggest that the corrected state of refractive errors is more important than the level of visual acuity as the criteria for appropriate visual input, which contributes to stable posture. Therefore, clinicians should consider the refractive condition, especially the characteristics of hyperopia, when analyzing body balance, and appropriate correction of uncorrected hyperopia to prevent falls.

Diurnal variations of amplitude of accommodation in different age groups.

Clinical assessment of amplitude of accommodation (AA) involves measuring the ability of the eye to change its optical power and focus on near tasks/objects. AA gradually decreases with increasing age. However, details of age-related diurnal changes in AA are not well known. This study compared diurnal changes in AA in the adolescents, the twenties, and the forties age groups. Measurement of AA using the push-up method was performed in six sessions at two-hourly intervals for 154 subjects (48, 56, 50 subjects for the adolescents, twenties, and forties age groups, respectively); the first measurements were taken from 9:00-10:00 a.m. and the final measurements from 7:00-8:00 p.m. The mean AA was 14.67 D (highest: 16.15 D in the 3:00-4:00 p.m. session, lowest: 13.35 D in the 9:00-10:00 a.m. session) for the adolescent group; 11.13 D (highest: 11.69 D in the 3:00-4:00 p.m. session; lowest: 10.61 D in the 9:00-10:00 a.m. session) in the twenties group; and 5.53 D (highest: 5.80 D in the 1:00-2:00 p.m. session, lowest: 5.11 D in the 7:00-8:00 p.m. session) in the forties age group. The measured AA showed significant difference between sessions; however, diurnal variations were greater in the younger groups. The measured AA was low at the beginning of the day in the adolescents and twenties groups and low at the end of the day in the forties age group. All age groups showed a high AA during the afternoon hours of the day (1:00-4:00 p.m.). Since the difference between each session was larger in younger subjects, AA should be evaluated while taking the age-related diurnal variations into account.

Uncorrected low hyperopia in young subjects induces postural instability even in those with clear visual acuity.

Reports have indicated the effect of myopic blur on postural stability. The objective of this study was to investigate the minimum refractive error to significantly affect postural stability through a various levels of hyperopia and myopia induced by ophthalmic lenses. Forty subjects with a mean age of 22.95 ± 2.21 years were enrolled. In all subjects, the subjective refraction with MPMVA (Maximum to Plus Maximum Visual Acuity) was performed to correct refractive error. To induce hyperopia and myopia, spherical lenses of ±1.0, ±2.0, ±3.0, ±4.0, ±5.0 and ±6.0 D were used on top of the trial frame with corrected condition as MPMVA (eyes-open with MPMVA). Under each induced-refractive error condition, general stability (ST) and sway power (SP) in frequencies by each subsystem were measured with Tetrax posturography with firm plates at patient's upright position, after performed the measurements under the conditions of eyes-open with MPMVA and eyes-closed. ST at eyes-closed was significantly greater than that at eyes-open with MPMVA (p < 0.001). ST was increased significantly for induced hyperopia of -1.0 D (p < 0.001) with decimal visual acuity of 1.07 ± 0.17 and for induced myopia of +3.0 D (p = 0.011) with decimal visual acuity of 0.16 ± 0.09, as compared to that at eyes-open with MPMVA. No significant difference was observed between induced hyperopia of -6.0 D and those at eyes-closed only. SP was increased significantly at low medium-frequencies of the peripheral vestibular signals in induced hyperopia, moreover, hyperopia induced at -6.0 D lenses was significantly different compared to that at eyes-open with MPMVA. Uncorrected low hyperopia in young subjects may lead to postural instability, although they can obtain clear vision. The corrected state of ametropia, especially hyperopia, is a more important factor of appropriate visual input in stable postural adjustment than visual acuity.

Effects of prolonged continuous computer gaming on physical and ocular symptoms and binocular vision functions in young healthy individuals.

BACKGROUND AND OBJECTIVE: Addiction to computer gaming has become a social problem in Korea and elsewhere, and it has been enlisted as a mental health disorder by the World Health Organization. Most studies related to computer use and vision have individually assessed physical and ocular symptoms and binocular vision. Accordingly, the present study comprehensively assessed subjective physical and ocular symptoms and functions related to binocular vision after prolonged continuous computer gaming. This study aimed to investigate the effects of prolonged continuous computer gaming on physical and ocular health and visual functions in young healthy individuals. METHODS: Fifty healthy college students (35 male/15 female), aged 19-35 years old, were enrolled in this study. The inclusion criteria were no binocular vision problems and no reported history of ocular disease. Participants played continuously for 4 h from 6:00 to 10:00 p.m. Physical and ocular symptoms and visual functions such as convergence, accommodation, phoria, and the blink rate were assessed before and after continuous computer gaming for 4 h. RESULTS: Continuous computer gaming for 4 h resulted in convergence and accommodation disturbances and increased physical and ocular discomfort. Near phoria showed an exophoric shift, whereas distance phoria showed no change. Moreover, the accommodative and vergence facilities and blink rate were significantly decreased. All visual functions recovered to the baseline levels by the following morning. DISCUSSION: Our findings suggest that excessive and continuous computer gaming impairs visual functions and causes ocular and physical fatigue. Our findings further the understanding of the adverse effects of excessive computer use on physical and ocular health, and adequate breaks are necessary to reduce physical and visual discomfort during computer gaming.

Comparison of predicted and measured axial length for ophthalmic lens design.

Ocular parameters have been applied to ophthalmic lens designs in order to satisfy individual wearers. An axial length (AL) of them can be used in individual ophthalmic lens designs. Our aim was to propose a reliable formula that predicts an individual's AL using the corneal radius and refractive error, and to demonstrate the applicability of this formula. A total of 348 subjects underwent keratometry, objective and subjective refraction, and AL measurement. The formula of calculated AL for prediction obtained from the original Gullstrand simplified schematic eye: calculated AL = (24.00 × aveK/7.80)-(SE × 0.40), where aveK and SE denote average corneal radius and spherical equivalent, respectively. Calculated AL was 24.50 ± 1.83 mm, which was 0.18 ± 0.47 mm longer than the measured value of 24.32 ± 1.73 mm (p < 0.001). The proportion showing the differences between the calculated and measured ALs were 284 eyes (40.8%) for 0.00-0.25 mm, 525 eyes (75.4%) for less than 0.50 mm, 665 eyes (95.5%) for less than 1.00 mm, and 31 eyes (4.5%) for more than 1.01 mm. Correlation coefficient showed a very high correlation between calculated and measured ALs (r = 0.967, p < 0.001), and higher in the myopic than in the hyperopic group. The mean difference was 0.18 mm; the 95% limit of agreement was +1.10--0.75 mm in all groups. Agreement was better in hyperopic eyes than myopic eyes. Prediction from calculation of AL with a formula using the corneal radius and SE provides an alternative method to direct measurements of AL, especially in the restricted environment, which can't use biometric equipment for personalized ophthalmic lens design.

Smooth-pursuit eye movements without head movement disrupt the static body balance.

[Purpose] To investigate the changes of body balance in static posture in smooth-pursuit eye movements (SPEMs) without head movement. [Subjects and Methods] Forty subjects (24 males, 16 females) aged 23.24 ± 2.58 years participated. SPEMs were activated in three directions (horizontal, vertical, and diagonal movements); the target speed was set at three conditions (10°/s, 20°/s, and 30°/s); and the binocular visual field was limited to 50°. To compare the body balance changes, the general stability (ST) and the fall risk index (FI) were measured with TETRAX. The subjects wore a head-neck collar and stood on a balance plate for 32 s during each measurement in three directions. SPEMs were induced to each subject with nine target speeds and directions. All measured values were compared with those in stationary fixation. [Results] The ST and FI increased significantly in all SPEMs directions, with an increased target speed than that in stationary fixation. In the same condition of the target speed, the FI had the highest value relative to diagonal SPEMs. [Conclusion] SPEMs without head movement disrupt the stability of body balance in a static posture, and diagonal SPEMs may have a more negative effect in maintaining body balance than horizontal or vertical SPEMs.

Changes in falling risk depending on induced axis directions of astigmatism on static posture.

[Purpose] To assess the changes in falling risk depending on the induced axis direction of astigmatism using cylindrical lenses in a static posture. [Subjects and Methods] Twenty subjects (10 males, 10 females; mean age, 23.4 ± 2.70 years) fully corrected by subjective refraction participated. To induce myopic simple astigmatism conditions, cylindrical lenses of +0.50, +1.00, +1.50, +2.00, +3.00, +4.00, and +5.00 D were used. The direction of astigmatic axes were induced under five conditions with increased cylindrical powers:, 180°, 90°, and 45° on both eyes; 180°/90° right/left eye, and 45°/135° right/left eye. Changes in the fall risk index were analyzed using the TETRAX biofeedback system. Measurements were performed for 32 seconds for each condition. [Results] The fall risk index increased significantly from C+4.00 D in 180°/90° right/left eye, C+3.00 D in 45°/135° right/left eye, and C+3.00 D in 45° on both eyes versus corrected emmetropia. Among the five axis conditions with the same cylindrical power lenses, the increase in the fall risk index was highest at 45° in both eyes. [Conclusion] Uncorrected oblique astigmatism may increase falling risk compared to with-the-rule and against-the-rule astigmatism. Clinical specialists should consider appropriate correction of astigmatism for preventing falls, especially for uncorrected oblique astigmatism.

Body balance under ametropic conditions induced by spherical lenses in an upright position.

[Purpose] To investigate the changes in body balance under ametropic conditions induced by spherical lenses in an upright position. [Subjects and Methods] Twenty subjects (10 males, 10 females) of average age 23.4±2.70 years participated and they were fully corrected by subjective refraction. To induce ametropic conditions (binocular myopia and hyperopia), lenses of ±0.50 D, ±1.00 D, ±1.50 D, ±2.00 D, ±3.00 D, ±4.00 D and ±5.00 D were used. General stability (ST), fall risk index (FI), and sway path (SP) were analyzed through changes in synchronization of left/right and toe/heel, as measured by the biofeedback system, TETRAX. Measurement was performed for 32 seconds for each condition. [Results] ST increased significantly from +0.50 D-induced myopia and from -1.00 D-induced hyperopia as compared with corrected emmetropia. FI increased significantly from +4.00 D-induced myopia and from -1.50 D-induced hyperopia as compared with corrected emmetropia. In SP, which means a change of body balance, toe/heel was significantly greater than left/right in all ametropic conditions. SP of right/left synchronization was not affected by the side of the dominant eye. [Conclusion] An uncorrected hyperope may cause subjects to have a higher risk of falling than an uncorrected myope. Therefore, clinical specialists should consider the refractive condition, especially hyperopia, when analyzing body balance.

Improvement of Vergence Movements by Vision Therapy Decreases K-ARS Scores of Symptomatic ADHD Children.

[Purpose] To determine whether the improvement of vergence movements by vision therapy can decrease the K-ARS scores of symptomatic ADHD children. [Methods] Eighty-one out of 1,123 children surveyed using the K-ARS, a parents'-reported questionnaire, led to 16 of these 81 children being showed scores of ≥19, and measurement of binocular function diagnosed as having convergence insufficiency. The 16 children were divided equally into a control group and a vision therapy group. [Results] After vision therapy for 12 weeks, near point convergence (4.38±0.69 cm) significantly neared compared to the near point convergence before vision therapy (11.50±2.28 cm), and both the break point (32.38±2.53 Δ) and recovery point (19.75±2.11 Δ) of near positive fusional vergence significantly improved compared to their values before vision therapy (15.88±2.64 Δ, 6.38±6.70 Δ, respectively). Near exophoria after vision therapy (7.81±2.00 Δ BI) significantly decreased compared to its value before vision therapy (12.00±1.16 Δ BI). The K-ARS scores referring to symptomatic ADHD significantly decreased after vision therapy (17.13±2.84) compared to before vision therapy (23.25±1.49). [Conclusions] Convergence insufficiency symptoms are closely related to symptoms screened for ADHD, and vision therapy to improve vergence movements is an effective method of decreasing the K-ARS scores.

Comparison of presbyopic additions determined by the fused cross-cylinder method using alternative target background colours.

PURPOSE: To compare and contrast standard and alternative versions of refractor head (phoropter)-based charts used to determine reading addition. METHODS: Forty one presbyopic subjects aged between 42 and 60 years were tested. Tentative additions were determined using a red-green background letter chart, and 4 cross-grid charts (with white, red, green, or red-green backgrounds) which were used with the fused cross cylinder (FCC) method. The final addition for a 40 cm working distance was determined for each subject by subjectively adjusting the tentative additions. RESULTS: There were significant differences in the tentative additions obtained using the 5 methods (repeated measures ANOVA, p < 0.001). The mean differences between the tentative and final additions were <0.10 D and were not clinically meaningful, with the exception of the red-green letter test, and the red background in the FCC method. There were no significant differences between the tentative and final additions for the green background in the FCC method (p > 0.05). The intervals of the 95% limits of agreement were under ±0.50 D, and the narrowest interval (±0.26 D) was for the red-green background. CONCLUSIONS: The 3 FCC methods with a white, green, or red-green background provided a tentative addition close to the final addition. Compared with the other methods, the FCC method with the red-green background had a narrow range of error. Further, since this method combines the functions of both the fused cross-cylinder test and the duochrome test, it can be a useful technique for determining presbyopic additions.