Myopic Defocus Research Articles

Influence of the time of day on axial length and choroidal thickness changes to hyperopic and myopic defocus in human eyes

Research in animal models have shown that exposing the eye to positive or negative spectacle lenses can lead to predictable changes in eye growth. Recent research indicates that brief periods (1–2 h) of monocular defocus results in small, but significant changes in axial length and choroidal thickness of human subjects. However, the effects of the time of day on these ocular changes with defocus are not known. In this study, we examined the effects of monocular myopic and hyperopic defocus on axial length and choroidal thickness when applied in the morning (change between 10 a.m. and 12 p.m.) vs the evening (change between 5 and 7 p.m.) in young adult human participants (mean age, 23.44 ± 4.52 years). A series of axial length (using an IOL Master) and choroidal thickness (using an optical coherence tomographer) measurements were obtained over three consecutive days in both eyes. Day 1 (no defocus) examined the baseline ocular measurements in the morning (10 a.m. and 12 p.m.) and in the evening (5 and 7 p.m.), day 2 investigated the effects of hyperopic and myopic defocus on ocular parameters in the morning (subjects wore a spectacle lens with +3 or −3 DS over the right eye and a plano lens over the left eye between 10 a.m. and 12 p.m.), and day 3 examined the effects of defocus in the evening (+3 or −3 DS spectacle lens over the right eye between 5 and 7 p.m.). Exposure to myopic defocus caused a significant reduction in axial length and thickening of the subfoveal choroid at both times; but, compared to baseline data from day 1, the relative change in axial length (−0.021 ± 0.009 vs +0.004 ± 0.003 mm, p = 0.009) and choroidal thickness (+0.027 ± 0.006 vs +0.007 ± 0.006 mm, p = 0.011) with defocus were significantly greater for evening exposure to defocus than for the morning session. On the contrary, introduction of hyperopic defocus resulted in a significant increase in axial length when given in the morning (+0.026 ± 0.006 mm), but not in the evening (+0.001 ± 0.003 mm) (p = 0.047). Furthermore, hyperopic defocus resulted in a significant thinning of the choroid (p = 0.005), but there was no significant influence of the time of day on choroidal changes associated with hyperopic defocus (p = 0.672). Exposure to hyperopic and myopic defocus at different times of the day was also associated with changes in the parafoveal regions of the choroid (measured across 1.5 mm nasal and temporal choroidal regions on either side of the fovea). Our results show that ocular response to optical defocus varies significantly depending on the time of day in human subjects. These findings represent a potential interaction between the signal associated with the eye's natural diurnal rhythm and the visual signal associated with the optical defocus, making the eye perhaps more responsive to hyperopic defocus (or ‘go’ signal) in the morning, and to myopic defocus (or ‘stop’ signal) in the latter half of the day.

Defocus vibrations in optical systems-considerations in reference to the human eye.

Experimental visual acuity (VA) of eight subjects was measured using the Freiburg vision test in a custom-made adaptive optics system. Measurements were conducted under one control and five defocus-induced conditions. In the defocus-induced conditions, 1 diopter of myopic defocus was added to the system using the Badal stage, and defocus vibrations with five different levels of amplitude were generated by a deformable mirror at 50 Hz. Computational simulations of the visual Strehl ratio (VSOTF) were performed using average aberrations of each subject recorded in the control condition. For the first time, to the best of our knowledge, it has been shown experimentally that both the simulated VSOTF and experimentally measured VA improve when defocus vibrations are added to a defocused eye.

The Effect of Atropine on Human Global Flash mfERG Responses to Retinal Defocus.

To investigate the action of atropine on global flash multifocal electroretinogram (gmfERG) responses to retinal defocus. gmfERG recordings were made monocularly in 19 healthy adults under three lens-imposed defocus conditions (2 diopters myopic, 2 diopters hyperopic, and no defocus) before and 24 hours after instillation of 1 drop of 0.1% atropine. Signals reflecting activity from the outer and inner retina (direct [DC] and induced [IC] components respectively) were analyzed. Responses were grouped into either a central (0°-6°) or peripheral (6°-24°) retinal zone. The gmfERG responses were compared relative to the no defocus, no atropine condition. Within the central zone, atropine had no effect on the amplitudes and peak times of DC or IC responses to defocus. For IC responses in the peripheral zone, there was a significant interaction effect of atropine and defocus (F2,36 = 6.050, P = 0.011) with greater post-atropine amplitudes under myopic defocus (mean increase = 15.5%, 95% confidence interval [CI] = 5.6%-25.4%, P = 0.004). Atropine also had a significant main effect of increasing IC peak times (F1,18 = 9.722, P = 0.006). For DC responses, atropine had a significant main effect of increasing DC amplitudes (F1,18 = 7.821, P = 0.012) and peak times (F1,18 = 15.406, P = 0.001) regardless of sign of defocus. Our results imply that atropine acts in the inner layers of the peripheral retina to affect neuronal responses to myopic defocus, raising the possibility that atropine may potentiate the effects of myopic defocus in inhibiting eye growth.

Multi-Factoral Mechanisms of Therapeutic Effect of Perifocal Spectacles (Perifocal-M) on Progressive Myopia in Children

There is detailed review of multi-factoral mechanisms of spectacles with peripheral defocus influence in children with progressive myopia in this article. At present local retinal mechanisms of neuro-regulatory control of eye growth are most effective in prevention of myopia development and progression. Optical correction of relative peripheral hyperopia with following peripheral myopic defocus affects the biochemical cascade from retina to choroid and sclera, which constrains an eye growth. Optical methods of myopia control, including spectacles, widely used in native and foreign ophthalmology practice. Since 2011, in Russia Perifocal-M spectacles are using, said spectacles provides bigger functionality of influence on myopic eye comparing to foreign analogues. Construction features of said spectacle lens have a complex influence on different optic-physiological eye structures and each of said structures affects refractogenesis. Perifocal spectacles takes into account specific for myopic eye features of central and peripheral refraction along horizontal and vertical meridians. They have stronger refraction in horizontal, which allows to eliminate specific optical disbalance in myopic eye and to create optical balance in the eye. Perifocal-M lens construction with asymmetric horizontal progression allows to correct relative peripheral hyperopia, to create myopic defocus in horizontal and to affect relations between refraction of nasal and temporal halves of retina. The latter is due to the fact that optical influence starts earlier and has bigger effect on nasal half of retina relative to temporal. Perifocal spectacles are inducing positive spherical aberrations in the eye, increasing accommodation functions, supporting high binocular visual acuity, improving binocular interaction during near work, fighting against heteroforias. Thus, optical features of Perifocal-M spectacles for the first time creates conditions for versatile functional influence on main myopogenic factors simultaneously, it effectively stops myopia progression.

The influence of different means of myopia correction on peripheral refraction depending on the direction of gaze

Peripheral defocus was experimentally found to control the development of refraction. To evaluate peripheral refraction (PR) of myopic eyes in terms of different means of correction and the direction of gaze. The study examined 128 patients (256 eyes) aged 8-14 years (average 11.07±0.39 years) with myopia from -1.0 to -7.0 (average -3.57±0.27 D). PR was measured without correction, in perifocal (PF), monofocal (MF), progressive glasses (PAL), monofocal soft contact lenses (ΜCL) and after orthokeratological (OCL) correction with the gaze directed straightforward or head angled outward, inward, upward and downward; all measurements were performed using binocular open-field auto ref/keratometer. PR profile without correction and with contact (OCL, ΜCL) correction does not depend on the direction of the gaze. In glasses, peripheral defocus is different with straightforward and skewed gaze directions. OCL forms a significant myopic defocus throughout the periphery of the retina. When using MCL, hyperopic defocus increases in all zones except the extreme temporal. In MF glasses, hyperopic defocus is formed and enhanced in all areas, significantly greater with skewed gaze than with straightforward. In PALs, myopic defocus is formed with gaze directed upward and downward, as well as at the extreme temporal periphery of the retina with straightforward gaze. In all other zones, hypermetropic defocus increases. In PF, in most zones myopic defocus is formed with all gaze directions. The greatest inhibitory effect on myopia progression is provided by OCL (YPR=0.28 D/year) and PF glasses (YPR=0.26 D/year). In contrast to correction with contact lenses, PR in glasses does depend on the direction of gaze. The inhibitory effect of the optics correlates with correction of hypermetropic defocus in myopic eyes.

Correcting progressive myopia with bifocal contact lenses with central zone for distant vision: changes in accommodation and axial length (a preliminary report)

To assess the state of accommodation and the dynamics of changes of ocular axial length in patients with progressive myopia who use bifocal soft contact lenses (BFSCLs). The main and control groups consisted of 50 children (100 eyes) each. Patients of the main group used BFSCLs with distance-oriented central zone and added power of 4 D on the periphery. Patients of the control group were corrected with spherical soft contact lenses (SSCLs). Baseline measurements included amplitude of accommodation (AA), positive relative accommodation (PRA) and the length of anterior-posterior axis of the eye. All patients were examined before wearing SCLs and every 3 months during the entire period of observation lasting 9 to 12 months. Correction of myopia with contact lenses is accompanied by the increase of AA and RPA. The users of BFSCLs with distance-oriented central zone and added power of 4 D on the periphery, which induces myopic peripheral defocus, had their accommodative function normalize much faster than the patients wearing SSCLs. The average increase in the ocular axial length in the BFSCLs group appeared to be significantly smaller than in the SSCLs group (0.11 and 0.58 D, respectively), which can be attributed to the simultaneous formation of the central focus and induced peripheral myopic defocus.

Long-term results of perifocal defocus spectacle lens correction in children with progressive myopia

To study the long-term results of wearing perifocal spectacles on the refraction in children with progressive myopia. Perifocal spectacles were assigned to children of 7-14 years old with progressive myopia from -1.0 to -6.0 D in terms of refractive spherical equivalent. The children were examined before the prescription of perifocal spectacles and after 6 months, 12-18 months, 2 years, 3 years and 4-5 years. We measured visual acuity, the character of vision, refractive error before and after cycloplegia, performed biomicroscopy, ophthalmoscopy and biometry. Peripheral refraction was studied at 15° and 30° points in the nasal (N15 and N30) and temporal (T15 and T30) meridians without correction and while wearing perifocal spectacles. In perifocal spectacles, in the 15° zone, 100% of the eyes formed myopic defocus, which averaged -0.05±0.1 D in T15°, -0.25±0.16 D in N15° and -0.44±0.03 D in T30°. In the N30° zone, the hypermetropic defocus decreased by 4 times and amounted to 0.38±0.03 D. The rate of progression of myopia decreased from 0.8 D of baseline values to 0.17 D at 4-5 years of follow-up. After 6 months of wearing perifocal spectacles, the refraction gain was -0.2±0.02 D (in the control group it was -0.38±0.04 D), after 12-18 months - (-)0.38±0.04 D (-0.63±0.09 D in the control group), after 2 years - (-)0,78±0,06 D (-1.18±0,15 D in the control group), after 3 years - (-)0.99±0.12 D (-1.65±0.20D in the control group). During the 4-5 years of the follow-up, the refractive error in the main group was -1.16±0.2 D, which is 60% less than in the control group (-1.95±0.2 D). Constant wearing of perifocal spectacles reduces the rate of myopia progression in children by 4.5 times compared with the initial rate, and by 1.6 times (by 60%) in comparison with the control group. Perifocal spectacles are recommended as optical means to slow the progression of myopia.

Peripheral defocus of myopic eyes corrected with Perifocal-M glasses, monofocal glasses, and soft contact lenses

The purpose of the work was to study peripheral refraction in myopic patients without correction, in soft contact lenses (SCL), in monofocal glasses, and in Perifocal-M glasses.Material and methods. A total of 97 patients (184 eyes) aged 9–18 years with various degrees of myopia were examined. The peripheral refraction was measured using a Grand Seiko WR-5100K binocular open-field autorefractometer without correction, in glasses, and in the SCL. For the eviation of gaze, a nozzle was designed, which was attached to the device stand at a distance of 50 cm from the patient's eyes. On the nozzle, there were 4 marks for fixing the gaze in the position of 15° and 30° to the nose (N) and to the temple (T) from the central position.Results. In patients with myopia of various degrees without correction and with correction by monofocal glasses, hyperopic defocus formed in all zones on average. In eyes that were corrected with SCL and were mildly myopic in all zones, hyperopic defocus was detected. In moderate myopia, myopic defocus was detected in the zones T30° and N30°. With a high degree of myopia, myopic defocus was detected on the periphery in all zones except T15°, reaching -2.23 ± 1.35 D in the T30° zone and -1.56 ± 0.82 D in the N30° zone. In Perifocal-M glasses, myopic defocus formed in mildly myopic eyes: in the T15° zone its value was -0.95 ± 0.12 D, -0.24 ± 0.05 D in the N15° zone, and -1.14 ± 0.13 D in the T30° zone. Hyperopic defocus was observed only in the zone at N30°, and its value was minimal compared to other types of correction which was 0.13 ± 0.05 D. In moderate myopia, myopic defocus was observed only in the zone N15° at -0.28 ± 0.04 D. In all other zones, hyperopic defocus remained, but its magnitude was minimal compared to monofocal glasses: 0.6 ± 0.1 D at T30°, 0.05 ± 0.04 D at T15°, and 0.74 ± 0.11 D at N30°. Conclusion. In relation to peripheral defocus, perifocal glasses have an advantage in correcting myopia of a low and, in part, moderate degree.

The effect of the optical design of multifocal contact lenses on choroidal thickness.

Studies have found reduced myopia progression with multifocal contact lenses, albeit with an unclear mechanism behind their protective effect. It is hypothesized that the induced myopic defocus of the addition zones of the multifocal contact lenses leads to choroidal thickening and therefore inhibits eye growth. In the current study, the effect of the optical design of multifocal contact lenses on choroidal thickness was investigated. Eighteen myopic participants wore four different contact lenses ((1) single-vision lenses corrected for distance, (2) single-vision lenses with +2.50 D full-field defocus, (3) Multifocal center-distance design, (4) Multifocal center-near design, both with addition power +2.50 D) for 30 min each on their right eye. Automated analysis of the macular choroidal thickness and vitreous chamber depth were performed before and after the wear of each of the contact lenses. Peripheral refraction profiles in primary gaze were obtained using eccentric photorefraction prior to contact lens wear. Choroidal thickness and vitreous chamber depth showed no significant differences to baseline with any of the contact lenses (all p > 0.05). Choroidal thickness increased by +2.1 ± 11.1 μm with the Multifocal center-distance design, by +2.0 ± 11.1 μm with the full-field defocus lens, followed by the Multifocal center-near design with +1.6 ± 11.3 μm and the single-vision contact lens correcting for distance with +0.9 ± 11.2 μm. Multifocal contact lenses have no significant influence on choroidal thickness after short-term wear. Therefore, changes in choroidal thickness might not be the main contributor to the protective effect of multifocal contact lenses in myopia control.

Effect of Optical Defocus on Choroidal Thickness in Healthy Adults With Presbyopia

To investigate changes in subfoveal choroidal thickness (SFCT) induced by retinal defocus in presbyopic adults. Thirty-seven healthy presbyopic subjects (age 57.74 ± 4.06 years) with low refractive errors (+0.08 ± 1.09 Diopters [D]) viewed a distant target (video movie at 6 m) for 60 minutes on two occasions while SFCT was monitored with optical coherence tomography every 20 minutes. On each occasion, both eyes were optimally corrected for distance: one eye acted as control, while the other (experimental) eye viewed through an additional ophthalmic lens: a +2.00 D lens imposing myopic defocus on one occasion and a -2.00 D lens imposing hyperopic defocus on the other occasion. Baseline SFCT was not different between experimental and control eyes (226 ± 72 μm vs. 232 ± 75 μm; P = 0.28). Myopic defocus caused a significant (P < 0.001) increase in SFCT in the defocused eye by 20 minutes (and +10 ± 5-μm increase at 60 minutes: P < 0.001), while hyperopic defocus caused a significant decrease in SFCT by 20 minutes (and -10 ± 5-μm decrease at 60 minutes: P < 0.001) with no change in control eyes. In presbyopic subjects, imposed myopic retinal defocus caused thickening of SFCT, while hyperopic defocus caused thinning of SFCT. This implies that uncorrected presbyopia, which is associated with hyperopic retinal defocus for near objects and which is highly prevalent in the developing world, would likely be associated with choroidal thinning and possibly reduced choroidal blood flow with prolonged periods in a near visual environment.

Gene expression in response to optical defocus of opposite signs reveals bidirectional mechanism of visually guided eye growth.

Myopia (nearsightedness) is the most common eye disorder, which is rapidly becoming one of the leading causes of vision loss in several parts of the world because of a recent sharp increase in prevalence. Nearwork, which produces hyperopic optical defocus on the retina, has been implicated as one of the environmental risk factors causing myopia in humans. Experimental studies have shown that hyperopic defocus imposed by negative power lenses placed in front of the eye accelerates eye growth and causes myopia, whereas myopic defocus imposed by positive lenses slows eye growth and produces a compensatory hyperopic shift in refractive state. The balance between these two optical signals is thought to regulate refractive eye development; however, the ability of the retina to recognize the sign of optical defocus and the composition of molecular signaling pathways guiding emmetropization are the subjects of intense investigation and debate. We found that the retina can readily distinguish between imposed myopic and hyperopic defocus, and identified key signaling pathways underlying retinal response to the defocus of different signs. Comparison of retinal transcriptomes in common marmosets exposed to either myopic or hyperopic defocus for 10 days or 5 weeks revealed that the primate retina responds to defocus of different signs by activation or suppression of largely distinct pathways. We also found that 29 genes differentially expressed in the marmoset retina in response to imposed defocus are localized within human myopia quantitative trait loci (QTLs), suggesting functional overlap between genes differentially expressed in the marmoset retina upon exposure to optical defocus and genes causing myopia in humans. These findings identify retinal pathways involved in the development of myopia, as well as potential new strategies for its treatment.

Sensitivity to S-Cone Stimuli and the Development of Myopia.

PurposeLongitudinal chromatic aberration (LCA) is a color signal available to the emmetropization process that causes greater myopic defocus of short wavelengths than long wavelengths. We measured individual differences in chromatic sensitivity to explore the role LCA may play in the development of refractive error.MethodsForty-four observers were tested psychophysically after passing color screening tests and a questionnaire for visual defects. Refraction was measured and only subjects with myopia or hyperopia without severe astigmatism participated. Psychophysical detection thresholds for 3 cyc/deg achromatic, L-, M-, and S-cone–isolating Gabor patches and low-frequency S-cone increment (S+) and decrement (S−) blobs were measured. Parametric Pearson correlations for refractive error versus threshold were calculated and nonparametric bootstrap 95% percentage confidence intervals (BCIs) for r were computed.ResultsS-cone Gabor detection thresholds were higher than achromatic, L-, and M-cone Gabors. S-cone Gabor thresholds were higher than either S+ or S− blobs. These results are consistent with studies using smaller samples of practiced observers. None of the thresholds for the Gabor stimuli were correlated with refractive error (RE). A negative correlation with RE was observed for both S+ (r = −0.28; P = 0.06; BCI: r = −0.5, −0.04) and S− (r = −0.23; P = 0.13; BCI = −0.46, 0.01) blobs, although this relationship did not reach conventional statistical significance.ConclusionsThresholds for S+ and S− stimuli were negatively related to RE, indicating that myopes may have reduced sensitivity to low spatial frequency S-cone stimuli. This reduced S-cone sensitivity might have played a role in their failure to emmetropize normally.

Effect of Peripheral Defocus on Axial Eye Growth and Modulation of Refractive Error in Hyperopes: Protocol for a Nonrandomized Clinical Trial.

BackgroundHyperopia occurs due to insufficient ocular growth and a failure to emmetropize in childhood. In anisohyperopia, it is unclear why one eye may remain hyperopic while the fellow eye grows toward an emmetropic state. Animal studies have shown that manipulating peripheral defocus through optical means while simultaneously providing correct axial focus can either discourage or encourage axial eye growth to effectively treat myopia or hyperopia, respectively. Myopia progression and axial eye growth can be significantly reduced in children and adolescents through the use of multifocal contact lenses. These contact lenses correct distance central myopia while simultaneously imposing relative peripheral myopic defocus. The effect of correcting distance central hyperopia while simultaneously imposing relative peripheral hyperopic defocus is yet to be elucidated in humans.ObjectiveThe objective of our study is to understand the natural progression of axial eye growth and refractive error in hyperopes and anisohyperopes and to establish whether axial eye growth and refractive error can be modified using multifocal contact lenses in hyperopes and anisohyperopes.MethodsThere are 3 elements to the program of research. First, the natural progression of axial eye growth and refractive error will be measured in spectacle-wearing hyperopic and anisohyperopic subjects aged between 5 and <20 years. In other words, the natural growth of the eye will be followed without any intervention. Second, as a paired-eye control study, anisohyperopes aged between 8 and <16 years will be fitted with a center-near multifocal design contact lens in their more hyperopic eye and a single-vision contact lens in the fellow eye if required. The progression of axial eye growth and refractive error will be measured and compared. Third, subjects aged between 8 and <16 years with similar levels of hyperopia in each eye will be fitted with center-near multifocal design contact lenses in each eye; the progression of axial eye growth and refractive error in these subjects will be measured and compared with those of subjects in the natural progression study.ResultsRecruitment commenced on 6 June 2016 and was completed on 8 April 2017. We estimate the data collection to be completed by April 2020.ConclusionsThis trial will establish whether axial eye growth can be accelerated in children with hyperopia by imposing relative peripheral hyperopic defocus using center-near multifocal contact lenses.Trial RegistrationClinicalTrials.gov NCT02686879; https://clinicaltrials.gov/ct2/show/NCT02686879 (Archived by Webcite at http://www.webcitation.org/71o5p3fD2)Registered Report IdentifierRR1-10.2196/9320

Narrow-band, long-wavelength lighting promotes hyperopia and retards vision-induced myopia in infant rhesus monkeys

The purpose of this investigation was to determine the effects of narrow band, long-wavelength lighting on normal refractive development and the phenomena of lens compensation and form-deprivation myopia (FDM) in infant rhesus monkeys. Starting at 24 and continuing until 151 days of age, 27 infant rhesus monkeys were reared under long-wavelength LED lighting (630 nm; illuminance = 274 ± 64 lux) with unrestricted vision (Red Light (RL) controls, n = 7) or a +3 D (+3D-RL, n = 7), −3 D (−3D-RL, n = 6) or diffuser lens (From Deprivation (FD-RL), n = 7) in front of one eye and a plano lens in front of the fellow eye. Refractive development, corneal power, and vitreous chamber depth were measured by retinoscopy, keratometry, and ultrasonography, respectively. Comparison data were obtained from normal monkeys (Normal Light (NL) controls, n = 39) and lens- (+3D-NL, n = 9; −3D-NL, n = 18) and diffuser-reared controls (FD-NL, n = 16) housed under white fluorescent lighting. At the end of the treatment period, median refractive errors for both eyes of all RL groups were significantly more hyperopic than that for NL groups (P = 0.0001 to 0.016). In contrast to fluorescent lighting, red ambient lighting greatly reduced the likelihood that infant monkeys would develop either FDM or compensating myopia in response to imposed hyperopic defocus. However, as in the +3D-NL monkeys, the treated eyes of the +3D-RL monkeys exhibited relative hyperopic shifts resulting in significant anisometropias that compensated for the monocular lens-imposed defocus (P = 0.001). The red-light-induced alterations in refractive development were associated with reduced vitreous chamber elongation and increases in choroidal thickness. The results suggest that chromatic cues play a role in vision-dependent emmetropization in primates. Narrow-band, long-wavelength lighting prevents the axial elongation typically produced by either form deprivation or hyperopic defocus, possibly by creating direction signals normally associated with myopic defocus.

The Interactions Between Bright Light and Competing Defocus During Emmetropization in Chicks.

The environment comprises multiple optical signals that affect eye growth. We aimed to determine if the inhibitory effects of myopic defocus and bright light (BL) against myopia are additive in the presence of the myopia-genic hyperopic defocus. In experiment 1, three groups of 24 chicks each were fitted with the following multizone dual-power lenses (pl): pl/-10 D (50:50 area), +10/-10 D (50:50 area), and +10/-10 D (33:67 area) monocularly for 6 days. Half of each group were raised under normal illumination of 500 lux, 12/12-hour light/dark cycle, whereas the remainder were exposed to 6-hour BL of 40 klx and 6-hour 500 lux during the light cycle. In experiment 2, 38 chicks wore +10/-10 D (33:67 area) lenses monocularly for 8 days and were exposed to one of four light intensities for 6 hours per day-500 lux, 10 klx, 20 klx, or 40 klx-and received 500 lux for the remainder of the light cycle. In experiment 1, interocular difference in refractions after 6 days for the three groups were -3.6 D, +2.0 D, and -4.2 D, respectively, under normal light and were -0.9 D, +4.2 D, and +0.67 D under BL, manifesting as a shorter anterior segment and vitreous chamber. In experiment 2, the effect of BL increased with light intensity in the +10/-10 D (33:67) group, with a significant difference in refraction between the 10 klx and 20 klx groups (interocular difference -2.75 ± 2.76 D vs. 1.70 ± 2.40 D, P < 0.01), but plateaued between 20 klx and 40 klx (1.70 ± 2.40 D vs. 1.70 ± 0.35 D, P > 0.05). The protective effects of myopic defocus and BL against experimental myopia were additive. The inhibitory effect of BL against myopia was dose dependent at 10 klx and above but plateaued at 20 klx.

The proportion of myopic defocus of the defocus incorporated soft contact (DISC) lens on retarding myopic progression

The proportion of myopic defocus of the defocus incorporated soft contact (DISC) lens on retarding myopic progression

High speed visual stimuli generator to estimate the minimum presentation time required for an orientation discrimination task.

How brief can a visual stimulus be and still be seen? To answer this question, we developed a digital micromirror device (DMD) based system operating at high speed (22.7 kHz) to control the rapid presentation of visual stimuli and estimated the minimum time required to identify the orientation of tumbling Snellen E letters. Time thresholds were measured in five subjects using a QUEST algorithm to vary the presentation time of the letters subtending either 0.75°, 1.5° and 4.5° on the retina, for two different effective pupil sizes (0.3 and 1 mm). Additionally, to evaluate the effect of defocus on time thresholds, the experiment was repeated with 1.5° letters and induced myopic defocus with 3, 6 and 9 D trial lenses placed in a conjugated pupil plane. We found that subjects were able to identify the orientation of the letters presented as briefly as 5 ms.

The interaction between homatropine and optical blur on choroidal thickness.

To analyse the short-term interaction between a short period of myopic and hyperopic defocus and the muscarinic antagonist homatropine upon the choroidal thickness and ocular biometrics of healthy subjects. Thirty young adults (15 myopes and 15 emmetropes) aged 18-35years had subfoveal choroidal thickness (ChT) and ocular biometry measurements taken before, 30min, and 60min following the introduction of monocular optical blur (0.00 D, +3.00 D and -3.00 D) combined with administration of either 2% homatropine or placebo (total of six conditions). Each combination of optical blur and drug was tested on different days, 2days apart, in randomised order. For choroidal thickness, we captured three SD OCT images (5mm, cross scans centred at the fovea with 999 A-scans and 50 B-scans) with the Copernicus SOCT HR instrument (www.optopol.com). A masked observer manually segmented the average B-scan images to derive subfoveal choroidal thickness measurements from each measurement session. The choroid exhibited significant thinning after imposing hyperopic defocus (-3.00 D) combined with placebo (-11±3μm, p<0.001). Homatropine prevented the significant choroidal thinning response with hyperopic defocus (+3±2μm), and the magnitude of ChT change was significantly different to placebo and hyperopic defocus (p<0.001). There was a significant increase in ChT after the introduction of myopic defocus (+3.00 D) with placebo (+12±3μm, p<0.0001) and homatropine combined with myopic defocus also caused a similar increase in ChT (+11±3μm; p<0.001). Eyes treated with homatropine alone exhibited a significant increase in ChT (+14±3μm, p<0.0001). There was no evidence of differences in choroidal response between refractive groups. Axial length also underwent small but significant changes (all p<0.01 except homatropine/hyperopic blur and placebo) that were of similar magnitude, but of opposite direction to the changes in choroidal thickness. Homatropine appears to block the thinning effect of hyperopic defocus on choroidal thickness but did not enhance the thickening effect of myopic defocus. The changes in the choroid may relate to the different pathways in the eye's response to myopic and hyperopic blur or reflect an upper limit on the capacity of the choroid to thicken in the short-term.

The Adenosine Receptor Antagonist, 7-Methylxanthine, Alters Emmetropizing Responses in Infant Macaques.

PurposePrevious studies suggest that the adenosine receptor antagonist, 7-methylxanthine (7-MX), retards myopia progression. Our aim was to determine whether 7-MX alters the compensating refractive changes produced by defocus in rhesus monkeys.MethodsStarting at age 3 weeks, monkeys were reared with −3 diopter (D; n = 10; 7-MX −3D/pl) or +3D (n = 6; 7-MX +3D/pl) spectacles over their treated eyes and zero-powered lenses over their fellow eyes. In addition, they were given 100 mg/kg of 7-MX orally twice daily throughout the lens-rearing period (age 147 ± 4 days). Comparison data were obtained from lens-reared controls (−3D/pl, n = 17; +3D/pl, n = 9) and normal monkeys (n = 37) maintained on a standard diet. Refractive status, corneal power, and axial dimensions were assessed biweekly.ResultsThe −3D/pl and +3D/pl lens-reared controls developed compensating myopic (−2.10 ± 1.07 D) and hyperopic anisometropias (+1.86 ± 0.54 D), respectively. While the 7-MX +3D/pl monkeys developed hyperopic anisometropias (+1.79 ± 1.11 D) that were similar to those observed in +3D/pl controls, the 7-MX −3D/pl animals did not consistently exhibit compensating myopia in their treated eyes and were on average isometropic (+0.35 ± 1.96 D). The median refractive errors for both eyes of the 7-MX −3D/pl (+5.47 D and +4.38 D) and 7-MX +3D/pl (+5.28 and +3.84 D) monkeys were significantly more hyperopic than that for normal monkeys (+2.47 D). These 7-MX–induced hyperopic ametropias were associated with shorter vitreous chambers and thicker choroids.ConclusionsIn primates, 7-MX reduced the axial myopia produced by hyperopic defocus, augmented hyperopic shifts in response to myopic defocus, and induced hyperopia in control eyes. The results suggest that 7-MX has therapeutic potential in efforts to slow myopia progression.

Предикторы миопии как отправная точка для начала активных мер по предупреждению ее развития

The review gives a detailed account of research data on myopia predictors. The most reliable predictors include cycloplegic sphere equivalent of axial refraction less than +0.75 D in children under 6 years, the axial length of more than 23.5 mm with the refractive error ≤ +1.0 D, myopic parents, axial length / corneal radius ratio (AL/CR) of less than 3, AC/A ratio over 4 Δ/D, pseudomyopia, heterophoria of more than 4 Δ, peripheral refraction of the nasal half of the eye at 20-30° higher than the temporal refraction in both eyes more than 0.5 D, reduced outdoor activity and high visual activity. Measures of prevention of myopia development are presented: adhering to the regiment of visual activity load, ergonomic stereotypes of near visual work, creation of binocular central and peripheral myopic defocus - positive spectacles or spectacles with Perifocal-P lenses with a central refraction of +0.25 D for permanent wear, home accommodative training exercises, physical exercises and sports, outdoor activity at least 90 minutes a day during daylight hours. For citation: Tarutta E.P., Proskurina O.V., Tarasova N.A., Ibatulin R.A., Kovychev A.S. Myopia predictors as a starting point for active prevention of myopia development. Russian ophthalmological journal. 2018; 11 (3): 107-12 (In Russian). doi: 10.21516/2072-0076-2018-11-3-107-112