Effect of manipulating the vergence/accommodation and image size mismatches of the ±2D flipper test on the frequency and precision of accommodative facility

Purpose

The ±2.00 D accommodative facility test presents several limitations, including the lack of objective information and inherent characteristics such as vergence/accommodative conflict, change in apparent size of the image, subjective criteria for judging blur and motor reaction time. By using free-space viewing conditions and an open-field autorefractor to monitor the refractive state, we examined the impact of manipulating these factors on the qualitative and quantitative assessment of accommodative facility.

Methods

Twenty-five healthy young adults (24.5 ± 4.5 years) took part in this study. Participants performed three accommodative facility tests (adapted flipper, 4D free-space viewing and 2.5D free-space viewing) under both monocular and binocular conditions in random order. A binocular open-field autorefractor was used to assess the accommodative response continuously, and these data were used to characterise accommodative facility quantitatively and qualitatively.

Results

There were statistically significant differences between the three testing methods both quantitatively (p < 0.001) and qualitatively (p = 0.02). For the same accommodative demand, a lower number of cycles was obtained for the adapted flipper condition in comparison with the 4D free-space viewing test (corrected p-value < 0.001, Cohen's d = 0.78). However, this comparison did not reach statistical significance for qualitative measures of accommodative facility (corrected p-value = 0.82, Cohen's d 0.05).

Conclusions

These data provide evidence that the qualitative assessment of accommodative facility is not influenced by the inherent limitations of the ±2.00 D flipper test. The use of qualitative outcomes by incorporating an open-field autorefractor allows examiners to increase the validity of the accommodative facility test in both clinical and research settings.     

Changes of the accommodative amplitude and the anterior chamber depth after implantation of an accommodative intraocular lens

Background

Modern cataract surgery is interested in recovery of the accommodative power. This investigation aimed at determining pseudophakic accommodation in subjects implanted with the accommodative Human Optics 1 CU intraocular lens after drug-induced ciliary muscle stimulation by measuring the objective refraction and the changes in anterior chamber depth in comparison with a PMMA intraocular lens with rigid haptics.

Methods

The studied sample involved 30 eyes of 30 patients undergoing cataract surgery due to age-related cataract. Patients were between 50 and 77 years of age (67.71±8.0). No randomization was performed. The 1 CU accommodative intraocular lens and the PMMA intraocular lens were implanted in 15 eyes of patients with an expected visual acuity of at least 0.7. Objective refraction under pilocarpine-stimulated ciliary muscle contraction was determined with a Hartinger coincidence refractometer. The anterior chamber depth was measured with Jäger’s Haag–Streit slit-lamp attachment. The accommodative amplitude and the anterior chamber flattening were calculated from the measured values.

Results

Twelve weeks after surgery the average accommodative amplitude in eyes with a 1 CU intraocular lens calculated from the refractive change under drug-induced stimulation was 0.48±0.36 D (with a maximum of 1.25 D). The measured change of anterior chamber depth under drug-induced stimulation was 0.3±0.32 mm (at a maximum of 0.9 mm). In the reference group with PMMA lenses, the mean accommodative amplitude derived from the refractive changes under drug-induced stimulation was 0.34±0.27 D (at a maximum of 0.85 D). The measured change in anterior chamber depth under drug-induced stimulation was 0.18±0.09 mm (at a maximum of 0.31 mm). No statistically significant differences were found between the two groups of lenses concerning change in anterior chamber depth and accommodative amplitude.

Conclusions

This investigations indicate a mean anterior 1 CU shift of only 0.32 mm and a maximum of 0.9 mm. The accommodative amplitudes measured with the Hartinger coincidence refractometer (mean value 0.47 D) correspond to these values. Similar conclusions may be drawn from existing investigative results of the reference group, which are on the same order of magnitude as those of the 1 CU group. Objective accommodation measurements are needed to evaluate commercially available accommodative intraocular lenses in a scientifically satisfactory manner. Objectively measurable parameters include changes of the anterior chamber depth as well as refraction, as determined for instance by coincidence refractometry and streak retinoscopy. Future studies should also consider the IOL properties, astigmatism, and pupillary diameter. This is the only way to identify pseudoaccommodation and a decisive factor for further development of accommodative artificial lenses.     

虹膜固定型有晶状体眼人工晶状体植入对高度近视患者睫状肌调节性微波动及调节力的影响

目的通过测量睫状肌调节性微波动高频成分(high frequency component,HFC)来分析有晶状体眼人工晶状体(phakic intraocular lens,P-IOL)植入对高度近视患者睫状肌收缩能力及调节力的影响。方法收集2004年12月～2006年3月在我院进行虹膜固定型有晶状体眼人工晶状体Verisyse植入的患者54例(54眼)。采用NIDEK ARK-730A红外验光仪中调节性微波动分析软件,分别在术后1周、3个月对该54例患者(54眼)进行睫状肌调节性微波动高频成分检查。并与患者术后调节力进行相关性分析。结果HFC与Verisys植入术后1周及3个月的调节力均正相关(术后1周r=0.628,P<0.01;术后3个月r=0.835,P<0.01);Verisyse植入术后3个月的HFC及调节力均较术后1周的HFC及调节力有明显提高。结论高度近视患者有晶状体眼人工晶状体植入有利于术后睫状肌收缩能力及调节力的提高。     

Ciliary Muscle Dimension Changes With Accommodation Vary in Myopia and Emmetropia

PurposeThe purpose of this study was to determine whether accommodation-induced changes in ciliary muscle dimensions vary between emmetropes and myopes, and the effect of the image analysis method.MethodsSeventy adults aged 18 to 27 years consisted of 25 people with emmetropia (spherical equivalent refraction [SER] +0.21 ± 0.36 diopters [D]) and 45 people with myopia (−2.84 ± 1.72 D). There were 23 people with low myopia (>−3 D) and 22 people with moderate myopia (−3 to −6 D). Right eye ciliary muscles were imaged (Visante OCT; Carl Zeiss Meditec) at 0 D and 6 D demands. Measures included ciliary muscle length (CML), ciliary muscle curved length (CMLarc), maximum ciliary muscle thickness (CMTmax), CMT1, CMT2, and CMT3 (fixed distances 1–3 mm from the scleral spur), CM25, CM50, and CM75 (proportional distances 25%–75%). Linear mixed model analysis determined effects of refractive groups, race, and demand on dimensions. Significance was set at P < 0.05.ResultsMyopic eyes had greater CML and CMLarc nasally than emmetropic eyes. Myopic eyes had thicker muscles than emmetropic eyes at nasal positions, except CM25 and CMT3, and at CM75 temporally. During accommodation and only nasally, CML reduced in emmetropic and myopic eyes, and CMLarc reduced in myopic eyes only. During accommodation, both nasally and temporally, muscles thickened anteriorly (CMT1 and CM25) and thinned posteriorly (CMT3 and CM75) except for temporal CM75. Moderate myopic eyes had greater temporal CMLarc than low myopic eyes, and the moderate myopes had thicker muscles both nasally and temporally using fixed and proportional distances.ConclusionsPeople with myopia had longer and thicker ciliary muscles than people with emmetropia. During accommodation, the anterior muscle thickened and the curved nasal muscle length shortened, more in myopic than in emmetropic eyes. The fixed distance method is recommended for repeat measures in the same individual. The proportional distance method is recommended for comparisons between refractive groups.     

Vergence and accommodation responses in the control of intermittent exotropia

Purpose

Individuals with different types of intermittent exotropia (IXT) may use neurally coupled accommodation and vergence responses differently from those without exotropia to achieve eye alignment. This study examined the relationship between simultaneously recorded accommodation and vergence responses in children and young adults with a range of types of IXT while aligned and deviated.

Methods

Responses of 29 participants with IXT (4–31 years) and 24 age-matched controls were recorded using simultaneous eye-tracking and eccentric photorefraction while they watched a movie in binocular or monocular viewing at varying viewing distances. Gradient response AC/A ratios and fusional vergence ranges were also assessed. Eight participants had divergence or pseudo-divergence excess type IXT, 5 had convergence insufficiency and 16 had basic IXT.

Results

Control and IXT participants accommodated similarly both in monocular and binocular-aligned conditions to visual targets at 80 and 33 cm. When deviated in binocular viewing, most participants with IXT exhibited changes in accommodation <0.5D relative to alignment. Gradient response AC/A ratios were similar for control [0.56 MA/D (IQR: 0.51 MA/D)] and IXT participants [0.42 MA/D (0.54 MA/D); p  = 0.60]. IXT participants showed larger vergence to accommodation ratios with changes from distance to near fixation [1.19 MA/D (1.45 MA/D)] than control participants [0.78 MA/D (0.60 MA/D); p = 0.02], especially among IXT participants with divergence or pseudo-divergence excess. Participants with IXT exhibited typical fusional divergence ranges beyond their dissociated position [8.86 Δ (7.10 Δ)] and typical fusional convergence ranges from alignment [18 Δ (15.75 Δ)].

Conclusions

This study suggests that control of IXT is typically neither driven by accommodative convergence alone nor associated with over-accommodation secondary to fusional convergence efforts. These simultaneous measurements confirmed that proximal vergence contributed significantly to IXT control, particularly for divergence or pseudo-divergence excess type IXT. For IXT participants in this study, achieving eye alignment did not conflict with having clear vision.     

The accommodative response,refractive error and mental effort: 1. The sympathetic nervous system

The accommodative response of 12 emmetropic subjects was measured for an array of numbers located at -1,-3 and -5 dioptres using an objective infra-red optometer. Responses were compared for passive (reading numbers) and active (adding numbers) conditions. The imposition of mental effort induced a significant increase in mean response for the -1 D stimulus, a response equivalent to the passive condition at -3 D and a reduction in response at -5 D. Mental effort induced similar responses for the -1 D and -3 D locations when sympathetic innervation to the ciliary muscle was blocked with the beta-receptor antagonist timolol maleate. Responses for the -5 D location were, however, significantly increased. It is proposed that sympathetic inhibition can modify the effect of mental effort on near accommodative responses.     

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

During accommodation, the refractive changes occur when the ciliary muscle contracts, releasing resting zonular tension and allowing the lens capsule to mold the lens into an accommodated form. This results in centripetal movement of the ciliary processes and lens edge. The goal of this study was to understand the relationship between accommodative refractive changes, ciliary process movements and lens edge movements during Edinger-Westphal (EW) and pharmacologically stimulated accommodation in adolescent rhesus monkeys. Experiments were performed on one eye each of three rhesus monkeys with permanent indwelling electrodes in the EW nucleus of the midbrain. EW stimulated accommodative refractive changes were measured with infrared photorefraction, and ciliary process and lens edge movements were measured with slit-lamp goniovideography on the temporal aspect of the eye. Images were recorded on the nasal aspect for one eye during EW stimulation. Image analysis was performed off-line at 30 Hz to determine refractive changes and ciliary body and lens edge movements during EW stimulated accommodation and after carbachol iontophoresis to determine drug induced accommodative movements. Maximum EW stimulated accommodation was 7.36+/-0.49 D and pharmacologically stimulated accommodation was 14.44+/-1.21 D. During EW stimulated accommodation, the ciliary processes and lens edge moved centripetally linearly by 0.030+/-0.001 mm/D and 0.027+/-0.001 mm/D, with a total movement of 0.219+/-0.034 mm and 0.189+/-0.023 mm, respectively. There was no significant nasal/temporal difference in ciliary process or lens edge movements. 30-40 min after pharmacologically stimulated accommodation, the ciliary processes moved centripetally a total of 0.411+/-0.048 mm, or 0.030+/-0.005 mm/D, and the lens edge moved centripetally 0.258+/-0.014 mm, or 0.019+/-0.003 mm/D. The peaks and valleys of the ciliary processes moved by similar amounts during both supramaximal EW and pharmacologically stimulated accommodation. In conclusion, this study shows, for the first time, that the ciliary processes and lens edge move centripetally, linearly with refraction during EW stimulated accommodation. During pharmacological stimulation, the ciliary processes move to a greater extent than the lens edge, confirming that in adolescent monkeys, lens movement limits the accommodative optical change in the eye.     

视力不良儿童调节幅度与眼生物参数的相关性

目的 探讨8～10岁视力不良儿童调节幅度与眼生物参数的相关性.方法 横断面研究.2010年7月对北京市密云区三所小学三、四年级300名视力不良学生进行了调查.所有学生均接受睫状肌麻痹后电脑验光与检影验光、调节幅度测定以及生物参数测量.根据屈光度范围,将受试者分为A组(+0.75 D≤SE≤-0.75 D)、B组(-0.75 D＜SE＜-1.75 D)和C组(SE≥-1.75 D),分别进行调节幅度与屈光度、眼生物参数的Pearson相关和线性回归分析.结果 A组调节幅度仅与前房深度具有相关性(r=-0.30,P=0.05).B组调节幅度与屈光度、眼轴长度及前房深度均具有显著相关性,有统计学意义(r=0.40、-0.41和-0.40,P均＜0.05),而与晶状体厚度、角膜厚度以及角膜曲率无相关性.C组中调节幅度与各生物参数均无相关性.结论 在一定的屈光度范围内(-0.75 D＜SE＜-1.75 D),调节幅度的大小与屈光度、眼轴长度及前房深度具有显著相关性.提示在近视初发时,可以通过视觉训练来改变调节功能的异常,间接、部分地控制近视的发展.     

Ciliary muscle morphology and accommodative lag in hyperopic anisometropic children

International Ophthalmology - To investigate the cross-sectional area (CSA) and thickness of the ciliary muscle and their correlation with accommodative lag in hyperopic anisometropic children....     

The Effect of Pattern Scan Laser Photocoagulation on Peripapillary Retinal Nerve Fiber Layer Thickness and Optic Nerve Morphology in Diabetic Retinopathy

Purpose

To evaluate the effect of pattern scan laser (PASCAL) photocoagulation on peripapillary retinal nerve fiber layer (RNFL) thickness, central macular thickness (CMT), and optic nerve morphology in patients with diabetic retinopathy.

Methods

Subjects included 35 eyes for the PASCAL group and 49 eyes for a control group. Peripapillary RNFL thickness, cup-disc area ratio and CMT were measured before PASCAL photocoagulation and at 2 and 6 months after PASCAL photocoagulation in the PASCAL or control groups.

Results

The average RNFL thickness had increased by 0.84 µm two months after and decreased by 0.4 µm six months after PASCAL photocoagulation compared to baseline, but these changes were not significant (p = 0.83, 0.39). The cup-disc area ratio was unchanged after PASCAL photocoagulation. CMT increased by 18.11 µm (p = 0.048) at two months compared to baseline thickness, and partially recovered to 11.82 µm (p = 0.11) at six months in the PASCAL group.

Conclusions

PASCAL photocoagulation may not cause significant change in the peripapillary RNFL thickness, CMT, and optic nerve morphology in patients with diabetic retinopathy.     

The Convergence Insufficiency Treatment Trial: Design,Methods, and Baseline Data

Objective: This report describes the design and methodology of the Convergence Insufficiency Treatment Trial (CITT), the first large-scale, placebo-controlled, randomized clinical trial evaluating treatments for convergence insufficiency (CI) in children. We also report the clinical and demographic characteristics of patients. Methods: We prospectively randomized children 9 to 17 years of age to one of four treatment groups: 1) home-based pencil push-ups, 2) home-based computer vergence/accommodative therapy and pencil push-ups, 3) office-based vergence/accommodative therapy with home reinforcement, 4) office-based placebo therapy. Outcome data on the Convergence Insufficiency Symptom Survey (CISS) score (primary outcome), near point of convergence (NPC), and positive fusional vergence were collected after 12 weeks of active treatment and again at 6 and 12 months posttreatment. Results: The CITT enrolled 221 children with symptomatic CI with a mean age of 12.0 years (SD = +2.3). The clinical profile of the cohort at baseline was 9Δ exophoria at near (+/? 4.4) and 2Δ exophoria (+/?2.8) at distance, CISS score = 30 (+/?9.0), NPC = 14 cm (+/? 7.5), and near positive fusional vergence break = 13 Δ (+/? 4.6). There were no statistically significant nor clinically relevant differences between treatment groups with respect to baseline characteristics (p > 0.05).Conclusion: Hallmark features of the study design include formal definitions of conditions and outcomes, standardized diagnostic and treatment protocols, a placebo treatment arm, masked outcome examinations, and the CISS score outcome measure. The baseline data reported herein define the clinical profile of those enrolled into the CITT.     

Accommodative disorders in non-presbyopic subjects with type 1 diabetes without retinopathy: A comparative,cross-sectional study

Purpose

The purpose of this study was to assess accommodative function in non-presbyopic individuals diagnosed with type 1 diabetes (T1D) without any signs of retinopathy, to determine the existence of possible accommodative disorders related to this disease, and to determine the influence of T1D duration and glycosylated haemoglobin values on accommodative function.

Methods

This comparative, cross-sectional study included 60 participants between 11 and 39 years old, 30 with T1D and 30 controls, with no previous eye surgery, ocular disease or medication that could affect the results of the visual examination. Amplitude of accommodation (AA), negative and positive relative accommodation (NRA and PRA), accommodative response (AR) and accommodative facility (AF) were assessed using the tests that showed the highest repeatability. Participants were classified based on normative values into ‘insufficiency, excess or normal results’, and a diagnosis of accommodative disorders (accommodative insufficiency, accommodative infacility and accommodative excess) was made.

Results

Participants with T1D had statistically significant lower AA and AF and higher NRA values than the controls. Furthermore, AA was significantly and inversely correlated with age and the duration of diabetes; however, AF and NRA were only correlated with disease duration. In the classification by accommodative variables, a higher percentage of ‘insufficiency values’ was observed in the T1D group (50%) than in the control group (6%; p < 0.001). In terms of accommodative disorders, accommodative infacility was the most prevalent (15%), followed by accommodative insufficiency (10%).

Conclusions

Our findings indicate that T1D affects most accommodative parameters, with accommodative insufficiency being associated with this disease.     

Accommodative vergence is driven by the phasic component of the accommodative controller

Conflicting opinions exist as to whether the phasic (reflex) component alone or both the phasic and tonic (adaptive) components of the accommodation and vergence systems drive accommodative vergence and vergence accommodation crosslinks. In this study the dissociated phoria to a 2 D target was measured before and after accommodative adaptation to discriminate the two possibilities. Results showed a significant difference in the dark-focus of accommodation pre- and post- near-vision task, indicating that accommodative adaptation had occurred. No significant change occurred in dark-vergence or in the accommodative response to the 2 D target. However, a significant decrease was found in the dissociated phoria presumably because of decreased phasic accommodation and its stimulation of accommodative vergence after the adaptation. This result is consistent with a model in which the accommodative vergence crosslink is driven by phasic accommodation only.     

Outcomes in patients with esotropic duane retraction syndrome and a partially accommodative component

Background:

The management of Duane retraction syndrome (DRS) is challenging and may become more difficult if an associated accommodative component due to high hyperopia is present. The purpose of this study is to review clinical features and outcomes in patients with partially accommodative esotropia and DRS.

Setting and Design:

Retrospective, non-comparative case series.

Materials and Methods:

Six cases of DRS with high hyperopia were reviewed.

Results:

Of the patients studied, the mean age of presentation was 1.3 years (range: 0.5-2.5 years). The mean amount of hyperopia was + 5D (range: 3.50-8.50) in both eyes. The mean follow up period was 7 years (range: 4 months-12 years). Five cases were unilateral while one was bilateral. Four cases underwent vertical rectus muscle transposition (VRT) and one had medial rectus recession prior to presentation; all were given optical correction. Two (50%) of the four patients who underwent vertical rectus transposition cases developed consecutive exotropia, one of whom did not have spectacles prescribed pre-operatively. All other cases (four) had minimal residual esotropia and face turn at the last follow-up with spectacle correction.

Conclusion:

Patients with Duane syndrome can have an accommodative component to their esotropia, which is crucial to detect and correct prior to surgery to decrease the risk of long-term over-correction. Occasionally, torticollis in Duane syndrome can be satisfactorily corrected with spectacles alone.     

Oculomotor adaptations produced by virtual reality environments

Purpose: Virtual reality (VR) displays require a static accommodation response to be maintained despite continual variation in vergence. The aim of this experiment was to establish the effect of VR stimulation upon the tonic elements of the accommodation and vergence controllers. Methods: Twenty subjects (mean age 22.0 ± 4.5 years) participated with informed consent in the experiment. The subjects were emmetropic and free of all ocular or systemic disease. Tonic accommodation (TA) was measured in darkness using the Shin‐Nippon SRW‐5000 (Tokyo, Japan) infrared autorefractor which takes a measure of the accommodative state every 1 s. Readings were taken over a period of 3 min and an average TA value was calculated when the accommodative state had reached a stable level. Tonic vergence (TV) was measured in darkness continuously for 3 min using an EyeTrace 300X (Iota AB, Sundvall, Sweden) infrared limbal eyetracker and an average TV value was calculated when the traces had reached a stable level. Subjects were then immersed in a VR environment, for 30 min, generated using SimulEyes field‐sequential shutter goggles controlled by a Dell XPS R450 PC (Bracknell, UK). The VR display required a constant accommodation response of 3D, while the vergence response typically varied between 0 and 5 MA. Following immersion, measurements of TA and TV were repeated. Results: A significant relationship (y = 1.13x ? 0.71, R = 0.85, p = 0.001) was found between the initial TV level and the shift induced by the VR environment such that negative TV positions shifted in the positive direction and vice‐versa. No significant change in TA was observed. Conclusions: The VR environment produced substantial adaptation of TV. These findings suggest that the vergence controller acts to shift vergence bias in order to reduce stimuli conflicts with accommodation found in VR environments. This enables subjects to maintain a stable accommodation response despite continual changes in the vergence position.     

Short-term adaptation of accommodation,accommodative vergence and disparity vergence facility

Previous studies have found that subjects can increase the velocity of accommodation using visual exercises such as pencil push ups, flippers, Brock strings and the like and myriad papers have shown improvement in accommodation facility (speed) and sufficiency (amplitude) using subjective tests following vision training but few have objectively measured accommodation before and after training in either normal subjects or in patients diagnosed with accommodative infacility (abnormally slow dynamics). Accommodation is driven either directly by blur or indirectly by way of neural crosslinks from the vergence system. Until now, no study has objectively measured both accommodation and accommodative–vergence before and after vision training and the role vergence might play in modifying the speed of accommodation. In the present study, accommodation and accommodative–vergence were measured with a Purkinje Eye Tracker/optometer before and after normal subjects trained in a flipper-like task in which the stimulus stepped between 0 and 2.5 diopters and back for over 200 cycles. Most subjects increased their speed of accommodation as well as their speed of accommodative vergence. Accommodative vergence led the accommodation response by approximately 77 ms before training and 100 ms after training and the vergence lead was most prominent in subjects with high accommodation and vergence velocities and the vergence leads tended to increase in conjunction with increases in accommodation velocity. We surmise that volitional vergence may help increase accommodation velocity by way of vergence–accommodation cross links.     

Risk factors for abnormal binocular vision after successful alignment of accommodative esotropia.

PURPOSE: The purpose of this study was to identify clinical factors associated with abnormal binocular vision outcomes among children with accommodative esotropia (ET) whose eyes were successfully realigned with spectacles only or with spectacles and surgery. METHODS: The participants were 69 children with accommodative ET who were followed up prospectively from the time of diagnosis. Clinical factors examined in this study included high accommodative convergence-to-accommodation (AC/A) relationship, high hyperopia, anisometropia, age of onset, and duration of eye misalignment. Binocular vision was assessed using measures of stereopsis, fusional vergence, sensory foveal fusion, and motion visual-evoked potential (mVEP). RESULTS: Children with a high AC/A relationship are 2.2 times more likely to have an absence of fusional vergence than are children with a normal AC/A relationship. Children having a duration of constant eye misalignment >/= 4 months before being successfully treated are 4.6 times more likely to have abnormal stereopsis, 33 times more likely to have no stereopsis, 37 times more likely to have an absence of fusional vergence, 31 times more likely to have an absence of sensory foveal fusion, and 17 times more likely to have an asymmetric mVEP response than children with a duration of constant ET diagnosed at 0 to 3 months. CONCLUSIONS: Following successful eye alignment, as many as 75% of patients with accommodative ET had anomalous binocular vision. A high AC/A relationship poses a significant risk for abnormal fusional vergence only. A constant eye misalignment lasting >/= 4 months poses a significant risk for anomalous binocular vision on all measures studied.