Influence of prismatic effect due to decentration of optical center in ophthalmic lens.

Background and Aims: Induced prismatic effects due to poor fitting spectacle frames is a common problem, seen in most of the spectacle wearers and this improper fitting is often due to optical center demarcation on lenses and this error causes asthenopic symptoms and diplopia. However, these errors are most common in developing countries due to lack of awareness, hence a standardized regulation is required. The current study aimed to estimate the amount of prismatic effect that is induced due to the decentration of an optical center in ophthalmic lens. Methods: A quantitative cross-sectional study was conducted in single vision spectacle wearers (N = 120) with a mean age of 25 ± 5 years. The pupillometric evaluation was performed to mark the pupil center on the spectacle lens. A lensometry evaluation was done to mark the optic center of the spectacle lens. A comparison was made to note whether the optic center is aligned with pupillary center. Objective assessment was performed through Prentice's rule (P = cF) and subjective symptoms were assessed through a validated visual comfort questionnaire. Results: In this sample, around 57% of the individual with single vision glasses were not looking through the optic center and experiencing induced prismatic effect of -0.7 to 0.6 prism diopter, with mean decentration of 3.5 mm. Forty percent of the individuals with misaligned optic center showed asthenopic symptoms and visual discomfort. Conclusion: Optometrist should check quality of dispensing and visual performance before handing over the newly dispensed glasses to the patients.

Impact of color vision deficiency on the quality of life in a sample of Indian population: Application of the CVD-QoL tool.

Purpose: To investigate the quality of life (QoL) in a sample of color vision deficit (CVD) patients in India and how color vision deficiency affects them psychologically, economically, and in productivity related to their work and occupation. Methods: A descriptive and case-control study design using a questionnaire was conducted on N = 120 participants, of whom 60 were patients of CVD (52 male and eight female) who visited two eye facilities in Hyderabad between 2020 and 2021 and 60 were age-matched normal color vision participants who served as controls. We validated English-Telugu adapted version of CVD-QoL, developed by Barry et al. in 2017 (CB-QoL). The CVD-QoL consists of 27 Likert-scale items with factors (lifestyle, emotions, and work). Color vision was assessed using the Ishihara and Cambridge Mollen color vision tests. A six-point Likert scale was used, with lower scores indicating poor QoL (from 1 = severe issue to 6 = no problem). Results: The CVD-QoL questionnaire's reliability and internal consistency were measured, including Cronbach's α (α =0.70-0.90). There was no significance between the group in age (t = -1.2, P = 0.67) whereas the Ishihara colour vision test, scores showed a significant difference (t = 4.50, P < 0.001). The QoL scores showed a significant difference towards lifestyle, emotions and work (P = 0.001). The CVD group had a poorer QoL score than the normal color vision group odds ratio [OR] =0.31, 95% confidence interval [CI], (P = 0.002, CI = 0.14-0.65, Z = 3.0) . In this analysis, a low CI indicated that the OR was more precise. Conclusion: Color vision deficiency affects Indians' QoL, according to this study. The mean scores of lifestyle, emotions, and work were lower than the UK sample.Since CVD is underreported and possibly affects developing countries more, advocacy for a new health care plan on CVD is essential. Increasing public understanding and awareness could also help diagnosing the CVD population.

Color vision devices for color vision deficiency patients: A systematic review and meta-analysis.

Background and Aims: There is insufficient evidence to support that using electronic or optical color vision devices improve color perception with current advanced technology. The purpose of this study is to compare and analyze the different color vision devices available for patients with color vision deficiency (CVD) and evaluate whether these devices improved their color perception. Methods: This review included randomized, experimental, comparative studies, as well as narrative reviews, prototype and innovation studies, and translational studies, followed by case-control and clinical trials with nonsurgical interventions studies, that is, electronic color vision devices, optical devices, and contact lens-based studies, with standardized inclusion and exclusion criteria. Results: The primary outcome studied was the performance of color vision devices, both objective and subjective. Secondary outcomes included the ease of use and accessibility of color vision devices and technology. The grading of recommendation, assessment, development, and evaluation framework was used to develop a systematic approach for consideration and clinical practice recommendation for CVD devices for color-deficient populations. We incorporated meta-analysis reports from a total of n = 16 studies that met the criteria which consisted of case-control studies, prototype and innovation studies, comparative studies, pre- and post-clinical trial studies, case studies, and narrative reviews. Proportion and standard errors, as well as correlations, were calculated from the meta-analysis for various available color vision devices. Conclusion: This review concludes that commercially available color vision devices, such as EnChroma Glasses, Chromagen filters, and EnChroma Cx-14 do not provide clinically significant evidence that subjective color perception has improved. As a result, recommending these color vision devices to the CVD population may not prove high beneficial/be counterproductive. However, only a few color shades can be perceived differently. This systematic review and analysis will aid future research and development in color vision devices.

Refractive error, axial length, environmental and hereditary factors associated with myopia in Swedish children.

Clinical relevance: Investigation of refractive errors amongst Swedish schoolchildren will help identify risk factors associated with myopia development.Background: Genetic and hereditary aspects have been linked with the development of myopia. Nevertheless, in the case of 'school myopia' some authors suggest that environmental factors may affect gene expression, causing school myopia to soar. Additional understanding about which environmental factors play a relevant role can be gained by studying refractive errors in countries like Sweden, where prevalence of myopia is expected to be low.Methods: Swedish schoolchildren aged 8-16 years were invited to participate. Participants underwent an eye examination, including cycloplegic refraction and axial length (AL) measurements. Predictors such as time spent in near work, outdoor activities and parental myopia were obtained using a questionnaire. Myopia was defined as spherical equivalent refraction (SER) ≤ -0.50D and hyperopia as SER ≥ +0.75D.Results: A total of 128 children (70 females and 58 males) participated in this study with mean age of 12.0 years (SD = 2.4). Based on cycloplegic SER of the right eye, the distribution of refractive errors was: hyperopia 48.0% (CI95 = 38.8-56.7), emmetropia 42.0% (CI95 = 33.5-51.2) and myopia 10.0%. (CI95 = 4.4-14.9). The mean AL was 23.1 mm (SD = 0.86), there was a correlation between SER and AL, r = -0.65 (p < 0.001). Participants with two myopic parents had higher myopia and increased axial length than those with one or no myopic parents. The mean time spent in near work, outside of school, was 5.3 hours-per-day (SD = 3.1), and mean outdoor time reported was 2.6 hours-per-day (SD = 2.2) for all the participants. The time spent in near work and outdoor time were different for different refractive error categories.Conclusion: The prevalence of myopia amongst Swedish schoolchildren is low. Hereditary and environmental factors are associated with refractive error categories. Further studies with this sample are warranted to investigate how refractive errors and environmental factors interact over time.

The Cambridge Anti-myopia Study: variables associated with myopia progression.

PURPOSE: To identify variables associated with myopia progression and to identify any interaction between accommodative function, myopia progression, age, and treatment effect in the Cambridge Anti-Myopia Study. METHODS: Contact lenses were used to improve static accommodation by altering ocular spherical aberration, and vision training was performed to improve dynamic accommodation. One hundred forty-two subjects, aged 14-21 years, were recruited who had a minimum of -0.75D of myopia. Subjects were assigned to contact lens treatment only, vision training only, contact lens treatment and vision training, or control group. Spherical aberration, lag of accommodation, accommodative convergence/accommodation (AC/A) ratio, accommodative facility, ocular biometry, and refractive error were measured at regular intervals throughout the 2-year trial. RESULTS: Ninety-five subjects completed the 24-month trial period. There was no significant difference in myopia progression between the four treatment groups at 24 months. Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. There was a significant treatment effect at 12 months in the contact lens treatment group in younger subjects, based on a median split, aged under 16.9 years (p = 0.005). This treatment effect was not maintained over the second year of the trial. Younger subjects experienced a greater reduction in lag of accommodation with the treatment contact lens at 3 months (p = 0.03), compared to older contact lens treatment and control groups. There was no interaction between AC/A ratio and contact lens treatment effect. CONCLUSIONS: Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. Although there was no significant treatment effect at 24 months, an interaction between age and contact lens treatment suggests younger subjects may be more amenable, at least in the short term, to alteration of the visual system using optical treatments.

A randomised clinical trial to assess the effect of a dual treatment on myopia progression: the Cambridge Anti-Myopia Study.

PURPOSE: To evaluate the effect of a dual treatment modality for myopia, by improving accommodative functions, on myopia progression. METHODS: A double blind randomised control trial was conducted on 96 subjects. The treatment modality for the trial employed custom designed contact lenses which control spherical aberration in an attempt to optimise static accommodation responses during near-work, and a vision-training programme to improve accommodation dynamics. Myopia progression was assessed over a 2 year period using cycloplegic autorefraction and biometry. RESULTS: The mean progression was found to be -0.33 Dioptres (D) over the 2 years of the study. There was no interaction between contact lens treatment and vision training treatment at 24 months (p = 0.72). There was no significant treatment effect of either Vision Training or Contact Lens Spherical Aberration control on myopia progression. CONCLUSIONS: This study is unable to demonstrate that the progression of myopia can be reduced over a 2 year period by either of the two treatments aimed at improving accommodative function. Neither treatment group (contact lens or vision training) progressed at a slower rate over the 2 years of the study than did the appropriate control group.

Peripheral refractive changes associated with myopia progression.

PURPOSE: To evaluate the changes in peripheral refraction profiles associated with myopia progression and treatment modalities used in the Cambridge Anti-Myopia Study. METHODS: one hundred and seventy-seven myopes in the age range of 14 to 22 years were enrolled in the study. The mean spherical equivalent refractive error was 3.12 1.87 diopters (D) and the refractive error of each participant was corrected with contact lenses. The participants were randomly assigned to one of four treatment groups, which included: altered spherical aberration and vision training, altered spherical aberration only, vision training only, and control. Peripheral refractive error was measured using an open field autorefractor in the central 60° of the retina in 10° steps. The refractive error was measured using cycloplegic autorefraction. Two-year refractive progression data and initial peripheral refraction measurements were available in 113 participants. Measurements of peripheral refraction and cycloplegic refraction were obtained at three visits over 2 years in 12-month intervals for 92 participants. RESULTS: All subjects showed a relative peripheral hyperopia, especially in the nasal retina. A limited magnitude of myopia progression of -0.34 ± 0.36 D over 2 years was found in each of the four groups on average. There were no significant differences in the rate of progression between any of the treatment groups (P > 0.05). Initial peripheral J45 astigmatic refractive error at 20° and 30° in the nasal retina was weakly correlated with progression of myopia over 2 years (r = -0.27, P = 0.004 and r = -0.20, P = 0.040, respectively; n = 113). The change in spherical equivalent peripheral refractive error at 30° nasal retina over time was also significantly correlated with progression of myopia especially at 24 months (r = -0.24, P = 0.017, n = 92). CONCLUSIONS: Relative peripheral hyperopia is associated with myopia. Myopia progression may be weakly linked to changes in the peripheral refraction profiles in the nasal retina. However, a causative link between peripheral refractive error and myopia progression could not be established.

Repeatability of peripheral aberrations in young emmetropes.

PURPOSE: The purpose of this study is to assess the intrasession repeatability of ocular aberration measurements in the peripheral visual field with a commercially available Shack-Hartmann aberrometer (complete ophthalmic analysis system-high definition-vision research). The higher-order off-axis aberrations data in young healthy emmetropic eyes are also reported. METHODS: The aberrations of the right eye of 18 emmetropes were measured using an aberrometer with an open field of view that allows peripheral measurements. Five repeated measures of ocular aberrations were obtained and assessed in steps of 10° out to ±40° in the horizontal visual field (nasal + and temporal -) and -20° in the inferior visual field. The coefficient of repeatability, coefficient of variation, and the intraclass correlation coefficient were calculated as a measure of intrasession repeatability. RESULTS: In all eccentric angles, the repeatability of the third- and fourth-order aberrations was better than the fifth and sixth order aberrations. The coefficient of variation was <30% and the intraclass correlation coefficient was >0.90 for the third and fourth order but reduced gradually for higher orders. There was no statistical significant difference in variance of total higher-order root mean square between on- and off-axis measurements (p > 0.05). The aberration data in this group of young emmetropes showed that the horizontal coma (C(3)(1)) was most positive at 40° in the temporal field, decreasing linearly toward negative values with increasing off-axis angle into the nasal field, whereas all other higher-order aberrations showed little or no change. CONCLUSIONS: The complete ophthalmic analysis system-high definition-vision research provides fast, repeatable, and valid peripheral aberration measurements and can be used efficiently to measure off-axis aberrations in the peripheral visual field.

Increasing negative spherical aberration with soft contact lenses improves high and low contrast visual acuity in young adults.

PURPOSE: To evaluate the effects of a customised manipulation of spherical aberration (SA) on the high and low contrast visual acuities and contrast sensitivity of young adult myopes. METHODS: A placebo-controlled double masked trial of customised spherical aberration controlling soft contact lenses was undertaken in myopes aged 15-23. Participants wore customised soft contact lenses with either (i) zero spherical aberration or (ii) negative spherical aberration that resulted in a net SA (eye plus lens) of -0.1 micron. High and low contrast log MAR visual acuities and Pelli Robson contrast sensitivity were assessed in 196 eyes of 98 subjects after a period of 12 months wearing the lenses. RESULTS: Both high and low contrast acuities were significantly better in the group wearing the contact lenses with negative spherical aberration (high contrast log MAR, p = 0.043; low contrast log MAR, p = 0.043) which was not due to differences in residual astigmatism or pupil size between the two groups. Pelli Robson contrast sensitivity was not significantly different in the two groups. CONCLUSIONS: Manipulation of spherical aberration, taking account of the participants' baseline level of aberration, can cause statistically significant improvements in high and low contrast distance visual acuity although these improvements are too small in magnitude to be of clinical significance.

Aberration control and vision training as an effective means of improving accommodation in individuals with myopia.

PURPOSE: To test the efficacy of a novel dual treatment for improving accommodative accuracy and dynamics in young persons with myopia. METHODS: Ninety-three young persons with myopia (mean spherical equivalent, -3.0 +/- 1.8 D; age 16.8 +/- 2.1 years; spherical aberration +0.06 +/- 0.04 microm) participated in the study. Custom-designed soft contact lenses were used to alter ocular SA to -0.10 microm to improve accommodative accuracy and reduce any lag of accommodation. A vision training regimen was performed for 18 minutes per day for up to 6 weeks to improve speed of dynamic accommodation. Control groups had contact lenses with no added SA and/or no exercises. To avoid any effects of natural levels of negative aberration on the results of the study, all participants who had negative SA were excluded. RESULTS: The treatment contact lenses produced a significant reduction in lag of accommodation (P < 0.05) at all proximal viewing distances measured. The vision training measurement and treatment resulted in a significant increase in distance facility rate for all groups compared with their own baselines (P < 0.05). Near facility rate improved in the vision training treatment group only compared with its baseline (P < 0.05). Both positive and negative response times for distant viewing were significantly shorter in all groups after training compared with their baseline values (P < 0.05). At near, the positive response times were decreased significantly (P < 0.05) in both groups, whereas the negative response times decreased significantly only in the vision training treatment group. CONCLUSIONS: After 3 months, the dual treatments (altering SA and vision training) used in the study were effective in modifying accommodation. The static accommodative response to targets at proximal distances was increased by the altered SA contact lenses and rates of dynamic accommodation improved with vision training.

The effect of altering spherical aberration on the static accommodative response.

PURPOSE: To investigate the effect of altering the spherical aberration (SA) of the eye on the static accommodative response. METHODS: Participants were fitted with nominally afocal contact lenses with controlled amounts of SA of either -0.2, -0.1, 0.0, +0.1 or +0.2 microm for a 5-mm pupil. Measurements of SA and root mean square (RMS) total aberration for the eye plus lens for each participant were determined with a Complete Ophthalmic Analysis System aberrometer. Accommodation was stimulated either by placing targets at different dioptric distances from the eye, or by using a fixed distance target and placing negative-powered lenses in front of the eye. Accommodation responses were determined with a Shin-Nippon autorefractor. RESULTS: For both stimuli situations, the slope of the accommodation stimulus-response function was lowest for the lenses with +0.2 microm SA, and increased as the amount of SA was reduced. There was a significant negative correlation between SA and slope. Lag of accommodation at 33 cm correlated well with added SA, but did not correlate with total RMS error. There was no significant difference between the responses at 30 min after lens wear started and the responses after 1 h. CONCLUSIONS: Adding negative SA to the eye generally improves the slope of the accommodation stimulus-response curve and decreases lag of accommodation, and positive added SA depresses the slope of the stimulus-response curve and increases lag. The effect seems to be specific to SA, as there was no relationship between lag and RMS error. Altering SA may be a viable way of changing accommodative functions in clinical situations.