Monocular Estimate Method Research Articles

Accommodative functions in opium users and non-users

Background: Emerging evidence highlights a concerning prevalence of accommodative and convergence anomalies in individuals with opioid use disorder. However, there remains a significant scarcity of data comparing accommodative functions of opium users and non-users. Hence, we investigated potential changes in accommodative functions of opium users compared to that of non-users. Furthermore, we evaluated changes in these parameters after administering 5% phenylephrine eye drops, both within and between the two groups. Methods: This cross-sectional case-control study recruited opium users and non-users. The binocular amplitude of accommodation (AA), monocular estimate method (MEM), negative and positive relative accommodation (NRA and PRA, respectively), and monocular and binocular accommodative facility (AF) were assessed and documented. All measurements were repeated 30 min after instillation of one drop of 5% phenylephrine hydrochloride eye drops. Results: We recruited 103 opium users and 107 non-users, with comparable mean ages (P > 0.05) but significantly different sex ratios (P < 0.05), with men outnumbering women among the opium users. All accommodative functions measured before and after the instillation of 5% phenylephrine, along with the differences in their values between the two time points, were comparable between the two groups (all P > 0.05), with the exception of the right-eye AF, which was significantly higher in non-users than in opium users after instillation (P < 0.05). Within the opium user group, all accommodative functions exhibited significant differences between pre- and post-instillation measurements (all P < 0.05), except for NRA, which did not change (P > 0.05). In contrast, the non-user group showed no significant differences between pre- and post-instillation measurements for all accommodative functions (all P > 0.05), except in the AA and the right-eye MEM (both P < 0.05). Conclusions: We observed small but significant changes in most baseline accommodative functions after the application of 5% phenylephrine eye drops in opium users. In contrast, most parameters remained unchanged in healthy non-users. When comparing the results between the two groups pre- and post-application of phenylephrine, we found similar accommodative functions overall. However, non-users had a significantly higher value for the right-eye AF following the instillation. To better understand potential binocular anomalies in opium users, further longitudinal studies that are matched for age and sex should be conducted, focusing on additional aspects of binocular vision and ocular motility.

Binocular vision parameters in handloom silk weavers

Background: Focusing the gaze for prolonged periods on a fixed distance demands high visual efficiency in handloom silk weavers and might result in various accommodative and vergence dysfunctions. The aim of the present study was to assess accommodative and vergence parameters and determine the frequency of non-strabismic binocular vision anomalies (NSBVAs) among handloom silk weavers.
 Methods: In this cross-sectional study, we recruited voluntary handloom silk weavers from the Government-aided Society of Arignar Anna Silk Co-op Society K.H.-1, Kanchipuram, aged 20–39 years. All participants underwent preliminary visual examinations and comprehensive binocular vision testing of accommodative and vergence parameters. Sensory evaluation was performed using stereopsis testing and the Worth 4 Dot test. Motor evaluation included the ocular motility assessment, heterophoria checks for distance and near, near point of convergence, negative and positive fusional vergences for distance and near, vergence facility, negative and positive relative accommodations, both monocular and binocular near points of accommodation, and accommodative facility. The monocular estimate method was used to determine the accommodative response. Quantitative data are expressed as mean (standard deviation [SD]), and qualitative data are expressed as frequency (percentage).
 Results: We recruited a total of 72 weavers, including 41 (56.9%) men and, 31 (43.1%) women with mean (SD) age, working hours, and work experience of 34.15 (4.12) years, 9 (2.5) h/day, and 17.5 (6.9) years, respectively. Of the 29 (40.3%) weavers with a refractive error, 18 (25%) had astigmatism; seven (9.7%) had myopia; and four (5.6%) had hyperopia. Of the 72 weavers, 38 (52.8%) presented with NSBVAs, including 13 (18.1%) with accommodative dysfunctions, 11 (15.3%) with vergence dysfunctions, and 14 (19.4%) with combined accommodative and vergence dysfunctions. Accommodative insufficiency was the most prevalent dysfunction among all NSBVAs. Overall, 57 (79.2%) patients reported vision-related symptoms during their weaving hours, all with NSBVAs (n = 38), 19 with normal parameters in the binocular vision test, and 15 with no symptoms.
 Conclusions: The frequency of NSBVAs was high among handloom silk weavers compared to the literature. This implies a need for comprehensive binocular vision examination for people in this occupation to rule out NSBVAs for improving their quality of life and occupational productivity. Future large-scale studies are required to determine the exact NSBVAs prevalence among workers of this near vision-related occupation.

Study of Lag of Accommodation After Using a Smartphone

Background and Objectives: With the pervasive use of digital devices, especially smartphones, concerns about their harmful effects on vision has increased. The aim of the present study was to evaluate the effect of long-term activity with a smartphone on the accuracy of lag of accommodation of two eyes. Methods: In this cross-sectional study, 27(16 females and 11 males) students and staff (23 students and 4 staff) of the Iran University of Medical Science with a Mean±SD age of 25.29±4.72 years, with a visual acuity of 10/10, and emmetropic refraction with the available sampling method were selected. At first, the participants used a smartphone for an hour, and then, the lag of accommodation of two eyes was assessed with the monocular estimate method. Results: lag of accommodation of the right eye (P=0.001) and left eye (P=0.001) both statically increased significantly after one hour of smartphone use. However, no significant difference was found between the lag of accommodation of two eyes after near work with a smartphone (P=0.265). Conclusion: The present study confirmed the relationship between long-term near work with a smartphone and increased lag of accommodation.

Measurement accuracy in accommodative response by the Nott method

The measurement of accommodative response is usually performed by means of the Nott method. The accommodative response values were obtained as described in the bibliography and considering that the neutralizing lens shapes the target image. The values in accommodative response differ according to the calculation method utilized.The accommodation and convergence values when the target is placed 40cm away from the glasses are not the same in emmetropic and ametropic subjects. At the position of the effective binocular object, the initial values are indeed the same for both types of subjects. Comparing with experimental measurements using the Monocular Estimate Method (Mem), it was obtained the same values given the effect of the neutralizing lens.Optimizing the Nott method would require placing the target at a position where the effective binocular object is 40cm. Furthermore, the effect of the neutralizing lens should be considered in the calculation method.

Accommodative response under monocular and binocular conditions as a function of phoria in symptomatic and asymptomatic subjects

BackgroundThe neurological linkage of vergence and accommodation is a factor which can affect accuracy of accommodation, is in turn associated with symptoms of near‐related visual discomfort. The purpose of this study was to compare the accommodative response under monocular and binocular conditions in symptomatic and asymptomatic participants with different near phorias.MethodsSeventy students at Zahedan University of Medical Sciences, Iran (mean age: 21.2 ± 1.7 years; age range: 18 to 25 years) participated. The participants were divided into symptomatic and asymptomatic groups according to the convergence insufficiency symptom survey questionnaire score. The type and magnitude of the near dissociated phoria were determined using the prism neutralised cover test. The accommodative lag was measured by the ‘monocular estimate method’ (MEM) retinoscopy, at first under binocular and then monocular conditions. Testing distance was 40-cm.ResultsThe accommodative lag in exophoric participants was lower under binocular conditions compared to monocular and in esophoric participants greater under binocular than under monocular conditions. The binocular accommodative response (AR) was greatest in participants with high exophoria at near vision and least in participants with esophoria at near vision (p < 0.001; one‐way analysis of variance). The difference between binocular lag and monocular lag was significantly greater in symptomatic participants than in asymptomatic participants in both exophoria (p < 0.001) and esophoria (p = 0.009) (independent samples t‐test).ConclusionThe near binocular accommodative response was related to near heterophoria. Higher levels of vergence accommodation, resulting in differences in lag under monocular and binocular conditions, may be a factor in near point asthenopia.

Comparing accommodative function between the dominant and non-dominant eye

To compare the accommodative amplitude (AA), facility (AF), and lag between dominant and non-dominant eyes. Seventy students [mean (SD) age: 21.2 (1.7) years, range 18-25] from Zahedan University of Medical Sciences were selected. Retinoscopy and subjective refraction was used to determine the refractive error. The hole-in-the card method was used to determine eye dominance. The accommodative amplitude (AA) was measured in the dominant and non-dominant eye using the push-up method, and accommodative facility (AF) using ±2.00 dioptre flipper lenses at 40cm. Accommodative lag was determined using monocular estimate method (MEM) retinoscopy at 40cm. The right eye was dominant in 53 subjects (75.7%). There was no significant difference in refractive error (sphere, cylinder, and spherical equivalent) between dominant and non-dominant eyes. The mean (SD) for the AA, AF, and lag in dominant eyes was 12.48 (2.56) dioptres, 12.45 (4.83) cycles per minute, and 0.80 (0.27) dioptres respectively. The mean (SD) for the AA, AF, and lag in non-dominant eyes was 12.16 (2.37) dioptres, 12.20 (4.88) cycles per minute, and 0.83 (0.28) dioptres respectively. The mean (SD) difference in AA, AF, and lag between dominant and non dominant eyes was 0.32 (0.75) dioptres (P = 0.001), 0.25 (1.05) cycles per minute (P = 0.04), and -0.02 (0.11) dioptres (P = 0.10) respectively. The AA and AF was statistically better (P < 0.05) in the dominant eye group than in the non-dominant eye group. These data provided little evidence of any difference in the accommodative lag between dominant and non-dominant eyes (P > 0.05). The right eye was dominant in 76% of subjects. Superior AA and AF was found in the dominant eye as determined by hole-in-the card method in young healthy adults, although these differences are perhaps not of clinical significance (<0.50 dioptres and <2cycles per minute).

Modified Bell Retinoscopy: Measuring Accommodative Lag in Children

To describe a modified bell retinoscopy (MBR) method for quantifying accommodative lag in children and to assess its repeatability and comparability with other techniques. In MBR, the target is advanced toward the patient until the retinoscopic reflex is neutralized. A "standardized 40-cm target estimate" of lag was derived for each child using data from three retinoscope distances. Within-visit repeatability was assessed in normal children 5 to 23 months of age, a heterogeneous group of clinic patients, and a group of children with Down syndrome. Clinic patients were tested on separate days for between-visit repeatability and, also, with Nott retinoscopy (NR) and the monocular estimate method (MEM) on day 2. MBR correlated with NR (r = 0.84) and MEM (r = 0.82). MBR and NR estimates were lower than MEM for high lags. Within-visit repeatability of the standardized 40-cm target estimate of MBR in normal children and clinic patients varied with the amount of lag (p < 0.0001). The repeatability index for 0.50 D lag was 0.49 D and for 1.00 D lag it was 0.80 D. Repeatability was similar in children with Down syndrome. In clinic patients, the between-visit repeatability index for 0.50 D lag was 0.60 D for the second estimate of each day, with lower repeatability for the first measure of each day. Repeatability did not vary with age or refractive error. The decrease in repeatability with high lag may be attributable to spatial measurement error. MBR estimates of accommodative lag correlate with traditional dynamic retinoscopy measures over a wide range of lags and show comparable repeatability. MBR may be a useful addition to the repertoire of clinical tools available for assessing accommodation in young children.

Intra‐examiner repeatability and agreement in accommodative response measurements

Clinical measurement of the accommodative response (AR) identifies the focusing plane of a subject with respect to the accommodative target. To establish whether a significant change in AR has occurred, it is important to determine the repeatability of this measurement. This study had two aims: First, to determine the intraexaminer repeatability of AR measurements using four clinical methods: Nott retinoscopy, monocular estimate method (MEM) retinoscopy, binocular crossed cylinder test (BCC) and near autorefractometry. Second, to study the level of agreement between AR measurements obtained with the different methods. The AR of the right eye at one accommodative demand of 2.50 D (40 cm) was measured on two separate occasions in 61 visually normal subjects of mean age 19.7 years (range 18-32 years). The intraexaminer repeatability of the tests, and agreement between them, were estimated by the Bland-Altman method. We determined mean differences (MD) and the 95% limits of agreement [coefficient of repeatability (COR) and coefficient of agreement (COA)]. Nott retinoscopy and BCC offered the best repeatability, showing the lowest MD and narrowest 95% interval of agreement (Nott: -0.10 +/- 0.66 D, BCC: -0.05 +/- 0.75 D). The 95% limits of agreement for the four techniques were similar (COA = +/- 0.92 to +/-1.00 D) yet clinically significant, according to the expected values of the AR. The two dynamic retinoscopy techniques (Nott and MEM) had a better agreement (COA = +/-0.64 D) although this COA must be interpreted in the context of the low MEM repeatability (COR = +/-0.98 D). The best method of assessing AR was Nott retinoscopy. The BCC technique was also repeatable, and both are recommended as suitable methods for clinical use. Despite better agreement between MEM and Nott, agreement among the remaining methods was poor such that their interchangeable use in clinical practice is not recommended.

Accommodative ability in exotropia: Predictive value of surgical success

To evaluate the state and symmetry of accommodative response in the two eyes of patients with basic intermittent exotropia and to determine whether accommodative response is a predicting factor to the outcome of unilateral recession-resection procedures or symmetric lateral rectus recessions. Dynamic retinoscopy was performed preoperatively on 47 patients with basic intermittent exotropia with the capacity for fusion who were undergoing a first operation for intermittent exotropia. To obtain a clinical measurement of the degree of binocular accommodative response, the monocular estimate method was used. Patients were divided into two groups: those with an "equal effective accommodative response" and those with an "unequal accommodative response" between the two eyes. Both groups received either unilateral recession-resection procedures or symmetric lateral rectus recessions. Thirty-two of 47 patients (68%) showed a persistent interocular difference in accommodative amplitude (asymmetric accommodation) of at least 0.75 D. Among these 32 patients with an "unequal effective accommodation," 5 of 14 patients (35.7%) receiving lateral rectus recessions had a satisfactory outcome compared with 13 of the 18 patients (72%) receiving recess/resect procedures (p = 0.039). Of the 15 patients with an "equal effective accommodation," 7 of 8 (87%) receiving recession-resection procedures had a satisfactory outcome compared with 5 of 7 patients (71%) who had lateral rectus recessions (p = 0.57). Data suggest that patients with an asymmetric accommodative response benefit more from recession-resection procedures. A decrease in accommodative response of the nondominant eye could be a predicting factor on the outcome of exotropia surgery.

The Accommodative Element in Accommodative Esotropia

To evaluate the effect of reducing the hyperopic correction on the state of binocular accommodative response in fully accommodative esotropia and to determine the "comfortable" amount of reduction in hyperopic correction. A cohort study. Hyperopic corrections of children with a baseline refractive error of +1.50 to +5.0 diopters were gradually reduced in 0.50-diopter increments. Binocular accommodative ability was assessed by dynamic retinoscopy (monocular estimate method). Similar binocular accommodative responses were ascertained among patients with a baseline hyperopic correction of < or =3.0 of hyperopia and >3.0 of hyperopia, and patients were divided into two groups, group 1 (13 patients) and group 2 (18 patients), accordingly. After a reduction of 2.0 diopters in group 1 and 1.0 diopter in group 2, there was a decrease in accommodative response initially in the nondominant eye, accompanied by the dominant eye with a further reduction of 0.50 diopter. To overcome the bilateral accommodative lag, a reinstatement of a 0.50-diopter stronger hyperopic correction was required. Patients in group 1 tolerated a mean undercorrection of 2.37 diopters, and 77% were weaned from their spectacles. All of the children in group 2 were dependent upon spectacles at the completion of the study period. The final spectacle worn was a median of -1.67 diopters less than their full cycloplegic refraction. A complete binocular accommodative ability seems to be a prerequisite for the establishment of "comfortable" hyperopic undercorrections. It does not seem to be a reasonable approach to consider further reductions in hyperopic correction in the presence of a bilateral decreased accommodative performance.

Comparisons of dynamic retinoscopy measurements with a print card, a video display terminal, and a PRIO ® System Tester as test targets

Dynamic retinoscopy is a common clinical test for assessment of visual function in patients with symptoms related to computer use. It has been suggested that performing dynamic retinoscopy with a fixation target resembling a computer screen may be valuable in the examination of computer users. However, such targets differ in luminance and other characteristics from the printed paper test cards typically used for dynamic retinoscopy. To address the effect of varying test targets on dynamic retinoscopy results, this study compared lag of accommodation results from dynamic retinoscopy with three different fixation targets: (a) a printed paper target, (b) a video display terminal, and (c) the PRIO vision testing device, which is designed to simulate a computer screen. MEM (monocular estimate method) dynamic retinoscopy was performed with the print target and with the PRIO device. The difference between results with the different test conditions were generally small, with a statistically significant 0.32 D lower lag found on MEM retinoscopy with the PRIO target IMEM-PRIO) than on MEM retinoscopy with a print target (MEM-PRINT). Mean lag measurements on MEM with a print target and on Nott retinoscopy with the video display terminal (NOTT-VDT) were only 0.04 D different. The 95% limits of agreement for the difference between MEM-PRINT and MEM-PRIO (+/- 0.6 D) was similar to the 95% limits of agreement for the interexaminer reliability of the two procedures (+/- 0.6 D for MEM-PRINT and +/- 0.7 D for MEM-PRIO). There was a small but statistically significant difference in lag of accommodation measured with MEM dynamic retinoscopy on the PRIO testing device when compared to a print card.

A normative study of the accommodative lag in elementary school children.

Limited normative information is available regarding the accommodative lag of elementary school children. The accommodative lag of approximately 100 children in each of the grades kindergarten to grade six was measured using the Monocular Estimate Method (MEM) of dynamic retinoscopy. Children were selected on the basis of passing school screening using Modified Clinical Technique (MCT) criteria. Habitual spectacle corrections were worn and MEM retinoscopy was performed at the child's usual working distance. The mean lag for the total population of children was OD +0.33 D (+/- 0.35), OS +0.35 D (+/- 0.34). Scatter plots show a weak relation between MEM and the other variables; however, the one-way analysis of variance of MEM against age and grade show that a dependency exists.