Intraocular Pressure Changes during Accommodation in Progressing Myopes, Stable Myopes and Emmetropes

The impact of different postures on acute intraocular pressure and accommodation responses during reading

INTRODUCTION

To investigate the effects of different reading postures on intraocular pressure (IOP) and near-work-induced transient myopia (NITM) in children with myopia.

METHODS

Sixty myopic children were instructed to read a book text placed at 33 cm for 30 min with two different reading postures: head bowed and head upright postures. The participants' IOP and NITM were assessed using a rebound tonometer and an open-field autorefractor. The measurement of IOP was conducted prior to reading, during reading sessions (at 5, 10, 20, and 30-min intervals), and after a 5-min recovery period.

RESULTS

For the head bowed posture, the mean baseline IOP was 16.13 ± 2.47 mmHg. A significant rise in IOP was observed after 5 min of reading (17.17 ± 2.97 mmHg; +1.03 ± 2.29 mmHg; p = 0.014). Subsequent measurements revealed a further increase after 20 min (17.87 ± 2.90 mmHg; +1.73 ± 2.58 mmHg; p < 0.001), which continued to persist even after 30 min of reading (17.57 ± 3.46 mmHg; +1.43 ± 2.66 mmHg; p = 0.002). The IOP at different time points measured in the head upright posture did not show any significant difference in comparison to the baseline measurement (all p = 1.000). Compared to reading with the head upright, reading with the head bowed resulted in a greater increase in IOP at each time point (p < 0.05). Furthermore, the NITM was higher for reading with the head bowed than for reading with head upright at 30 min (-0.24 ± 0.53 D vs. -0.12 ± 0.47 D, p = 0.038).

CONCLUSION

Reading in a head bowed position resulted in greater increases in IOP and NITM compared to reading in a head upright posture.

The lack of causal link between myopia and intraocular pressure: Insights from cross-sectional analysis and Mendelian randomization study

OBJECTIVE

This study aimed to explore the potential causal relationship between intraocular pressure (IOP) and myopia.

METHODS

The study included 3,459 patients who underwent corneal refractive surgery at our institution between 2021 and 2023. Preoperative data on IOP, spherical equivalent (SE), axial length (AL), and corneal thickness (CCT) were collected. The association between IOP and myopia was investigated through rank correlation analysis, and causal inference was examined using Mendelian randomization (MR) methods, including MR-Egger, weighted median, mode-based estimation, simple mode, and inverse variance weighted (IVW) approaches. Utilizing summary statistics from genome-wide association studies (GWAS), IOP was considered as the exposure, with myopia as the outcome variable. IVW method was employed for the primary analysis, supplemented by sensitivity analyses.

RESULTS

Cross-sectional analysis revealed a non-significant association between corrected IOP (cIOP) and myopia (r = -0.019, P = 0.12). MR analysis indicated a non-significant genetic causal relationship between cIOP and myopia under the IVW method (OR = 1.001; 95 % CI [0.999-1.003], P = 0.22), a finding corroborated in replication samples (OR = 0.98; 95 % CI [0.96-1.00], P = 0.099).

CONCLUSION

This study did not find a direct causal link between IOP and the development of myopia. These findings challenge the traditional role attributed to IOP in the progression of myopia and highlight the complex, multifactorial process of myopia development. This provides a new perspective on understanding the intricate mechanisms behind myopia progression.

Exploring the relationship between accommodation and intraocular pressure: a systematic literature review and meta-analysis

PURPOSE

To investigate the relationship between accommodation and intraocular pressure (IOP).

METHODS

Systematic literature search and meta-analysis following PRISMA guidelines was conducted on studies analyzing the relationship between accommodation and intraocular pressure. After removal of duplicates, title and abstract screening, full-text analysis was performed to select relevant articles and meta-analysis was then conducted as well.

RESULTS

Of the 1357 records identified, 17 met the selection criteria and were included. Overall, all studies showed that accommodation can influence IOP levels and meta-analysis indicated a significant IOP reduction of 1.10 mmHg (95%CI, -1.77; -0.42) following accommodative stimulus in healthy individuals, albeit with high heterogeneity among studies. Differences in IOP changes between emmetropic and progressing myopic individuals were not significant. Controversial results were obtained in patients with glaucoma with significantly lower IOP fluctuations being noted in eyes with previous trabeculectomy; however, the clinical heterogeneity of enrolled patients among studies made it not possible to combine results. Type of accommodative task, extraocular muscle contraction, head and body position all could potentially play a role in the measured IOP changes with, interestingly, near reading on a smartphone suggesting IOP increase.

CONCLUSION

Accommodation has an impact on IOP measurements and, overall, determines IOP decrease in healthy individuals. While such variations might not hold clinical significance for individuals in good health, their impact in patients with glaucoma should be considered. Further studies focused on specific components of such relationship are required to elucidate their individual impact and to define their potential role as non-pharmacological strategies to reduce IOP levels in selected patient categories.

Models of myopia: the effect of accommodation, lenses and atropine

BACKGROUND

Two quantitative models for myopia have been proposed and used for myopic intervention, one derived from feedback theory, and the other from physiological and mechanical considerations. This paper shows that they both predict the same results indicating that they are valid and reliable. These models are the only ones that can make predictions about the effect of atropine and lenses on myopia, explain multiple observations heretofore unexplained and offer possible interventions.

OBJECTIVE

Using their predictive power we test the models by calculating and comparing the effect of accommodation, lenses or atropine. The models offer a rationale that makes atropine equivalent to a positive lens for purposes of refractive development.

METHODS

This report includes thought experiments, actual experiments and trials, as well as an analysis of clinical data and integrates and tests results from all of them for far-reaching conclusions.

RESULTS

Both models accurately predict the same myopia progression caused by near work. These models are simple but powerful enough to suggest what treatments are indicated. Interventions for prevention and control of myopia are evaluated analytically, in particular atropine and optical treatments, such as positive lenses and under correction.

CONCLUSION

Optical treatments have enormous potential; atropine is of questionable value since there are ways to get the same or superior effect with lenses of power calculated as described here.

Two-Year Results of 0.01% Atropine Eye Drops and 0.1% Loading Dose for Myopia Progression Reduction in Danish Children: A Placebo-Controlled, Randomized Clinical Trial

We investigated the two-year safety and efficacy of 0.1% loading dose and 0.01% low-dose atropine eye drops in Danish children for reduction in myopia progression in an investigator-initiated, placebo-controlled, double-masked, randomized clinical trial. Ninety-seven six- to twelve-year old myopic participants were randomized to 0.1% loading dose for six months and then 0.01% for eighteen months (loading dose group, N = 33), 0.01% for two years (0.01% group, N = 32) or placebo for two years (placebo, N = 32). Axial length (AL) and spherical equivalent refraction (SER) were primary outcomes. Secondary outcomes included adverse events and reactions, choroidal thickness, and other ocular biometrical measures. Outcomes were measured from baseline and at six-month intervals. Individual eyes nested by participant ID were analyzed with linear-mixed model analysis. Data were analyzed with intention-to-treat. Mean AL was 0.08 mm less (95% confidence interval (CI): -0.01; 0.17, p-value = 0.08) in the 0.1% loading dose and 0.10 mm less (95% CI: 0.01; 0.19, p-value = 0.02) in the 0.01% group after two years of treatment compared to placebo. Mean SER progression was 0.12 D (95% CI: -0.10; 0.33) less in the loading dose and 0.26 D (95% CI: 0.04; 0.48) less in the 0.01% groups after two years of treatment compared to placebo (p-value = 0.30 and 0.02, respectively). In total, 17 adverse events were reported in the second-year follow-up, and all were rated as mild. Adjusting for iris color did not affect treatment effect estimates. Intra-ocular pressure increased over two years comparably between all groups but remained within normal limits. Two-year treatment with 0.01% low-dose atropine eye drops is a safe and moderately efficacious intervention in Danish children for reducing myopia progression.

Short-Term Exposure to Violet Light Emitted from Eyeglass Frames in Myopic Children: A Randomized Pilot Clinical Trial

Violet light (VL), 360−400 nm wavelength, is contained in the sunlight and is an effective element for myopia suppression. This study is to investigate the safety and efficacy of novel eyeglasses that emit VL from the frames. This is a double-masked, randomized, pilot clinical trial conducted in a clinic in Japan. Forty-three children with myopia were enrolled. Participants were randomly assigned to two groups, wearing VL-emitting eyeglass frames (VLf) that emitted VL of 310 μW/cm2 (VLf group, n = 22) or pseudo-placebo eyeglass frames with a minimal emission of VL (<10 μW/cm2) (control group, n = 21). The exposure time was 3 h per day. The primary outcomes were visual acuity, tear film break-up time, corneal endothelial cell density, and the slit-lamp/fundus examinations. The secondary outcome was the 6-month changes in the axial lengths and cycloplegic refractions. Forty-one (95%) participants were included; twenty-one in the VLf group and twenty in the control group. No significant differences were seen in any safety evaluation. Significant changes were seen in axial elongation, choroidal thickness, and cycloplegic refractions in the subgroup analysis of 8- to 10-year-old children (p < 0.05), but otherwise no significant differences were seen. The VLf showed short-term safety and effectiveness against myopia progression.

A Review of Intraocular Pressure (IOP) and Axial Myopia

The pathogenesis of myopia is driven by genetic and environmental risk factors. Accommodation not only alters the curvature and shape of the lens but also involves contraction of the ciliary and extraocular muscles, which influences intraocular pressure (IOP). Scleral matrix remodeling has been shown to contribute to the biomechanical susceptibility of the sclera to accommodation-induced IOP fluctuations, resulting in reduced scleral thickness, axial length (AL) elongation, and axial myopia. The rise in IOP can increase the burden of scleral stretching and cause axial lengthening. Although the accommodation and IOP hypotheses were proposed long ago, they have not been validated. This review provides a brief and updated overview on studies investigating the potential role of accommodation and IOP in myopia progression.

Peripheral refraction of myopic eyes with spectacle lenses correction and lens free emmetropes during accommodation

PURPOSE

To measure axial and off-axis refraction patterns in myopic eyes with spectacle lenses correction and lens free emmetropes in young healthy subjects at different target distances from 2.00 m (0.50 D) to 0.20 m (5.00 D) in terms of sphere, astigmatism, and spherical equivalent refraction.

METHODS

Refraction was measured at the center, 20 and 40 degrees from the line of sight both nasally and temporally in 15 emmetropic and 25 myopic young healthy subjects with an open field, binocular, infrared autorefractor (Grand Seiko WAM-5500, Hiroshima, Japan). Fixation target was a Maltese cross set at 2.00, 0.50, 0.33 and 0.20 m from the corneal plane. Changes in off-axis refraction with accommodation level were normalized with respect to distance axial values and compared between myopic eyes with spectacle lenses correction and lens free emmetropes.

RESULTS

Off-axis refraction in myopic eyes with spectacle lenses correction was significantly more myopic in the temporal retina compared to lens free emmetropes except for the closest target distance. Relative off-axis refractive error changed significantly with accommodation when compared to axial refraction particularly in the myopic group. This change in the negative direction was due to changes in the spherical component of refraction that became more myopic relative to the center at the 0.20 m distance as the J0 component of astigmatism was significantly reduced in both emmetropes and myopes for the closest target.

CONCLUSION

Accommodation to very near targets (up to 0.20 m) makes the off-axis refraction of myopes wearing their spectacle correction similar to that of lens free emmetropes. A significant reduction in off-axis astigmatism was also observed for the 0.20 m distance.

Accommodative Exercises to Lower Intraocular Pressure

Purpose

This study investigated how a conscious change in ocular accommodation affects intraocular pressure (IOP) and ocular biometrics in healthy adult volunteers of different ages.

Methods

Thirty-five healthy volunteers without ocular disease or past ocular surgery, and with refractive error between −3.50 and +2.50 diopters, were stratified into 20, 40, and 60 year old (y.o.) age groups. Baseline measurements of central cornea thickness, anterior chamber depth, anterior chamber angle, cornea diameter, pupil size, and ciliary muscle thickness were made by autorefraction and optical coherence tomography (OCT), while IOP was measured by pneumotonometry. Each subject's right eye focused on a target 40 cm away. Three different tests were performed in random order: (1) 10 minutes of nonaccommodation (gazing at the target through lenses that allowed clear vision without accommodating), (2) 10 minutes of accommodation (addition of a minus 3 diopter lens), and (3) 10 minutes of alternating between accommodation and nonaccommodation (1-minute intervals). IOP was measured immediately after each test. A 20-minute rest period was provided between tests. Data from 31 subjects were included in the study. ANOVA and paired t-tests were used for statistical analyses.

Results

Following alternating accommodation, IOP decreased by 0.7 mmHg in the right eye when all age groups were combined (p = 0.029). Accommodation or nonaccommodation alone did not decrease IOP. Compared to the 20 y.o. group, the 60 y.o. group had a thicker ciliary muscle within 75 μm of the scleral spur, a thinner ciliary muscle at 125–300 μm from the scleral spur, narrower anterior chamber angles, shallower anterior chambers, and smaller pupils during accommodation and nonaccommodation (p's < 0.01).

Conclusion

Alternating accommodation, but not constant accommodation, significantly decreased IOP. This effect was not lost with aging despite physical changes to the aging eye. A greater accommodative workload and/or longer test period may improve the effect.

Effect of Near Work on Intraocular Pressure in Emmetropes

Objective

To determine whether accommodation induced by reading alters intraocular pressure (IOP) in healthy, young, emmetropic adults and to document the duration and magnitude of this effect.

Design

Cross-sectional study. Participants. Fifteen healthy, emmetropic young adults.

Methods

Subjects performed 20 minutes of near work (reading at 33 cm) followed by 20 minutes of far work (reading at 520 cm) while IOP was measured using an iCare tonometer at baseline and every 5 minutes thereafter. Statistical analysis was performed using repeated measures ANOVA. Main Outcome Measures. Intraocular pressure.

Results

IOP decreased significantly compared to baseline IOP after 10 minutes of near work (average change of −1.60 ± 2.2 (SD) mm Hg, p < 0.05). IOP remained lower than baseline IOP throughout all subsequent near and far work. The difference in IOP at the end of experimentation compared to baseline IOP was −1.87 ± 1.81 mm Hg (p < 0.05). IOP remained lower than baseline IOP throughout all subsequent near and far work. The difference in IOP at the end of experimentation compared to baseline IOP was −1.87 ± 1.81 mm Hg (

Conclusions

Near work decreases IOP in healthy emmetropes, and this effect is sustained for at least 20 minutes after discontinuing prolonged near work. Providers may need to consider this effect when measuring IOP in clinical practice.

Effect of Smartphone Use on Intraocular Pressure

The rapidly increasing utilization of smartphones makes ophthalmic problems associated with their use an important issue. This prospective study aimed to determine whether using a smartphone to view visual material is associated with a change in the intraocular pressure (IOP), and to determine which groups of factors best predict the time-dependent increase in IOP with smartphone use. This study included 158 eyes (127 glaucomatous and 31 healthy eyes) recruited from Seoul National University Bundang Hospital. Participants performed a sustained fixation task consisting of watching a movie on a smartphone screen for 30 minutes continuously at a viewing distance of 30 cm. A small but statistically significant time-dependent increase in IOP was observed while viewing a movie on a smartphone, being 10.6 ± 3.1, 11.0 ± 3.3, 11.2 ± 3.4, and 11.6 ± 3.5 mmHg before and 5, 10, and 30 minutes after the fixation task, respectively (P < 0.0001). Recursive partitioning tree analysis revealed that a shallower anterior chamber (<2.32 mm) was the strongest predictive factor for faster time-dependent increase in IOP (0.68 mmHg/minute). A higher visual field mean deviation (≥-0.22 dB), and an older age (≥48 years) were the second and third most influential factors associated with the rate of IOP increase (0.59 and 0.15 mmHg/minute, respectively).

Dynamic Changes in Schlemm Canal and Iridocorneal Angle Morphology During Accommodation in Children With Healthy Eyes: A Cross-Sectional Cohort Study

Purpose

The purpose of this study was to explore changes in Schlemm canal (SC), trabecular meshwork (TM), and iridocorneal angle (ICA) morphology during accommodative effort in children and young adults.

Methods

We acquired anterior segment optical coherence tomography images (AS-OCT) of the ICA and ciliary muscle (CM) of both eyes of 50 children age 4 to 16 years with healthy eyes, at two levels of accommodation: 2.5 and 15 diopters (D). Semiautomated nasal ICA measurements were as follows: angle opening distance at 500/750 μm (AOD-500, -750), trabecular iris space area at 500/750 μm (TISA-500, -750), and trabecular iris angle at 500/750 μm (TIA-500, -750). Manual measurements were as follows: anteroposterior and radial SC diameter (SC-APD, SC-RD), cross-sectional area of SC (SC-CSA) and TM height (TMH), TM length (TML), and TM density (TMD). CM width was measured at 1, 2, and 3 mm from the scleral spur (CM-1, CM-2, CM-3). For each parameter, a three-level random-effects model was fitted to estimate differences between the two levels of accommodation.

Results

With accommodative effort, SC diameters and CSA increase significantly, as do TM length and iridocorneal angle parameters. With increasing age, SC dimensions reduce. Angle parameters are smaller in eyes with greater spherical equivalent (hypermetropia).

Conclusions

AS-OCT can be used to visualize dynamic morphologic changes in outflow structures with physiologic accommodation. The increase in SC dimensions with accommodative effort may contribute to the regulation of IOP in children.

Intraocular pressure monitoring by rebound tonometry in children with myopia

BACKGROUND/PURPOSE:

Topical atropine treatment is generally accepted to retard the progression of myopia, but it is associated with side effects such as photophobia and elevation of intraocular pressure (IOP). IOP measurements in children are challenging. The traditional applanation tonometry by direct contact with the cornea will require patient's cooperation. The rebound tonometer, using a dynamic electromechanical method for measuring IOP, shows good correlation with traditional tonometry. The purpose of this study is to evaluate the IOP of myopic children under atropine treatment using rebound tonometer and to compare the characteristics between rebound tonometry and applanation tonometry.

METHODS:

This study is a prospective study measuring IOP by rebound tonometer in myopic children under regular low-dose atropine treatment. We recruited children with refraction error showing myopia over −0.5 D with 0.15%, 0.3%, or 0.5% atropine eye drops use every night or every other night for myopia control. Children with treatment duration of atropine <1 month were excluded from the study. IOP measurements were performed by applanation tonometer (Tono-Pen XL, Reichert) and rebound tonometer (ICARE). The reliability of rebound tonometer was analyzed with percentage. Comparison of IOP between rebound tonometer and applanation tonometry was presented.

RESULTS:

The rebound tonometry was well tolerated by all participants and caused no complaints, discomfort, or adverse events. Totally 42 myopic eyes of 42 subjects were included in the study. The average age of these participants was 10 years old, range from 5 to 16. Median = 10 years old. The average IOP of the right eye by rebound tonometer was 17.4 ± 3 mmHg, and 17.1 ± 3 mmHg by applanation tonometry. Nearly 19%, 33%, and 24% of difference of IOP readings between rebound tonometer and Tono-Pen applanation are within 0 mmHg, 1 mmHg, and 1–2 mmHg, respectively.

CONCLUSIONS:

Rebound tonometry has good correlation with applanation tonometry and 76.1% of differences between two tonometers are <2 mmHg. The advantage of drop-free rebound tonometry has made it easier to obtain IOP readings in myopia children under atropine treatment.