Repeatability intraexaminer and agreement in amplitude of accommodation measurements

Background  Clinical measurement of the amplitude of accommodation (AA) provides an indication of maximum accommodative ability. To determine whether there has been a significant change in the AA, it is important to have a good idea of the repeatability of the measurement method used. The aim of the present study was to compare AA measurements made using three different subjective clinical methods: the push-up, push-down, and minus lens techniques. These methods differ in terms of the apparent size of the target, the end point used, or the components of the accommodation response stimulated. Our working hypothesis was that these methods are likely to show different degrees of repeatability such that they should not be used interchangeably. Methods  The AA of the right eye was measured on two separate occasions in 61 visually normal subjects of mean age 19.7 years (range 18 to 32). The repeatability of the tests and agreement between them was estimated by the Bland and Altman method. We determined the mean difference (MD) and the 95% limits of agreement for the repeatability study (COR) and for the agreement study (COA). Results  The COR for the push-up, push-down, and minus lens techniques were ±4.76, ±4.00, and ±2.52D, respectively. Higher values of AA were obtained using the push-up procedure compared to the push-down and minus lens methods. The push-down method also yielded a larger mean AA than the negative-lens method. MD between the three methods were high in clinical terms, always over 1.75D, and the COA differed substantially by at least ±4.50D. The highest agreement interval was observed when we compared AA measurements made using minus lenses and the push-up method (±5.65D). Conclusions  The minus lens method exhibited the best repeatability, least MD (−0.08D) and the smallest COR. Agreement between the three techniques was poor. Presentation at ARVO 2007. This study was supported by grant PR1/07-14909 from the Universidad Complutense de Madrid.     

Scleral expansion bands for presbyopia

OBJECTIVE: To evaluate the safety and effectiveness of surgery using scleral expansion bands. DESIGN: Prospective, noncomparative, small case series. PARTICIPANTS: Six subjects were enrolled. Four subjects received implants in one eye and two subjects received implants in both eyes. METHODS: Implantation of the scleral expansion bands (SEB) was performed using Schachar's standard technique. Subjects were observed at six postoperative examination intervals through 1 year. MAIN OUTCOME MEASURES: The key efficacy measures were distance-corrected near visual acuity (at 40 cm and 60 cm) and subjective amplitude of accommodation (push-up, push-down, and minus lens procedures). RESULTS: Distance visual acuity was similar before and after surgery. The near visual acuity and the subjective amplitude of accommodation were temporarily improved in three eyes. However, in the other five eyes, we did not note any improvement of accommodation or near vision after the scleral expansion surgery. CONCLUSIONS: In this study, the outcome of the SEB intervention was characterized by inconsistent and unpredictable results with a low level of patient satisfaction.     

Lens thickness with age and accommodation by optical coherence tomography

PURPOSE: To utilize time-domain optical coherence tomography (OCT) to measure changes in the crystalline lens with age and accommodation. METHODS: A cross-sectional study of pre-presbyopic and presbyopic subjects was conducted. Amplitude of accommodation was measured with the push-up test. Objective accommodation was measured with the Grand Seiko auto-refractor and a Badal lens system. Lens thickness was measured with the Zeiss Visante OCT and an internal optometer. The data were analysed using correlation coefficients, linear regression, and by calculating the average change in lens thickness per diopter change in objective accommodation. RESULTS: Twenty-two subjects between the ages of 36 and 50 years completed the study. Subjective amplitude of accommodation ranged from 2.17 to 6.38 D. Objective accommodation ranged from 0.22 to 4.56 D. The mean lens thickness was 4.05+/-0.20 mm. The mean change in lens thickness for up to a 5-D accommodative stimulus ranged from 0.01 to 0.26 mm. The correlation coefficients were: age and subjective accommodation, r= -0.74; age and objective accommodation, r= -0.84; change in lens thickness and age, r= -0.65; change in lens thickness and subjective accommodation, r=0.74; change in lens thickness and objective accommodation, r=0.64; objective and subjective accommodation, r=0.82 (all p<0.01). An increase in lens thickness of 21 microm per year of age was determined by linear regression. For the subjects who showed at least 1 D of accommodative response on the Grand Seiko auto-refractor, there was an increase of 51+/-19 microm per dioptre of accommodation. CONCLUSIONS: Optical coherence tomography is a non-invasive technique that can be used to quantify changes in the thickness of the crystalline lens. Subjective and objective measurements of accommodation, as well as age, were robustly correlated with the measured changes in lens thickness. Lens thickness changes with age and accommodation as measured with the Visante OCT compare well with previous findings using Scheimpflug photography and ultrasound.     

Objective accommodation measurement with the Grand Seiko and Hartinger coincidence refractometer.

PURPOSE: Subjective push-up tests and dynamic retinoscopy are standard clinical accommodation tests. These are inadequate for assessing if accommodation can be restored in presbyopes. Commercially available clinical autorefractors offer potentially reliable methods for objective accommodation measurement. This study evaluated accuracy and reliability of the Grand Seiko WR-5100K autorefractor for objective accommodation measurement in young adults. METHODS: Twenty-two subjects, aged 21 to 30 years (mean 25.6 +/- 2.26) participated. Three methods were used to stimulate and measure accommodation: (1) subjective push-up test in free space, (2) a near target pushed-up on a near-point rod and the response measured with the WR-5100K and a Hartinger coincidence refractometer (HCR), and (3) a distant target viewed through increasing powered negative trial lenses and the response measured with the WR-5100K and the HCR. Trial lens calibration procedures were also used to test the accuracy of the instruments. RESULTS: Average maximum accommodative amplitude with the subjective push-up test was 7.74 D +/- 0.36 D (mean +/- SE). For a 5 D stimulus, accommodation of 4.68 D +/- 0.10 D (mean +/- SE) and 4.13 D +/- 0.09 D was measured with the WR-5100K and the HCR, respectively. With a distant target viewed through a -5.00 D trial lens, the WR-5100K measured 4.07 D +/- 0.09 D and the HCR measured 4.05 D +/- 0.09 D of accommodation. Maximum mean response measured with trial lens-induced accommodation was 5.67 D +/- 0.15 D with the WR-5100K and 5.77 D +/- 0.18 D with the HCR. CONCLUSIONS: The subjective push-up test overestimated accommodative amplitude relative to the objective measures. The WR-5100K showed good agreement in the responses measured for both pushed-up near targets and a distant target viewed through trial lenses with the HCR, a widely used laboratory instrument. The Grand Seiko WR-5100K, a commercially available instrument, has been demonstrated to be well suited for clinical, objective accommodation measurement using a population of normal young adults.     

Validity and repeatability of the modified push-up method for measuring the amplitude of accommodation

Introduction : The modified push-up method is recommended for testing the amplitude of accommodation in young children. In this study, the modified push-up method was compared with the conventional push-up method for measuring the amplitude of accommodation. Methods : Three experiments were carried out in the validity study. The first experiment was set up to compare the measured amplitudes between the modified push-up method and the conventional push-up method. The second and third experiments were carried out to further investigate the possible contribution of the target choice or criterion choice, respectively, to the measured amplitude results. The repeatability study was then performed. Results : The modified push-up method produced lower measures of the amplitude of accommodation than the conventional push-up method. The average difference was 0.40 D monocularly and 1.30 D binocularly. The choices of both target and criterion significantly contributed to the difference. The modified push-up method was a highly repeatable method. Conclusion : We conclude that the modified push-up method is interchangeable with the conventional push-up method for clinical use, but lower amplitude readings by 0.40 D monocularly and 1.3 D binocularly would be expected.     

可调节人工晶状体植入术的早期疗效观察

目的探讨超声乳化白内障吸除可调节人工晶状体植入术的临床疗效和调节幅度。方法对75例(94只眼)白内障患者行超声乳化白内障吸除1CU型可调节人工晶状体植入术,观察并记录术眼的主观屈光状态、裸眼远视力、裸眼近视力、最佳矫正远视力、30cm处远视力矫正后近视力、30cm处最佳矫正近视力、主观调节幅度(分别采用主观移近法和负镜片法测量)。术后随访时间1～12个月,对术后1周、1个月及3个月的资料进行分析。结果术后1周、1个月及3个月裸眼近视力≥Jr5者分别占81.9%(77/94)、85.1%(80/94)及84.0%(79/94);远视力矫正后近视力≥Jr5者分别占78.7%(74/94)、79.8%(75/94)及74.5%(70/94)。采用主观移近法和负镜片法检查调节幅度,术后1周分别为(1.96±0.63)D(0.75～4.50D)和(1.74±0.59)D(0.75～4.50D),术后1个月分别为(1.89±0.54)D(0.75～3.25D)和(1.68±0.47)D(0.75～3.25D),术后3个月分别为(1.77±0.53)D(0.75～2.75D)和(1.66±0.50)D(0.75～2.75D)。术后1周、1个月及3个月2种方法测量的主观调节幅度比较,差异均无统计学意义(P>0.05)。远视力矫正后近视力和调节幅度之间为正相关(P=0.00)。结论早期观察结果显示1CU型可调节人工晶状体植入术后视功能恢复良好,患者在具有较好远视力的同时,具备良好的视近能力。远期效果有待进一步观察。     

Scleral expansion bands for presbyopia1

Objective

To evaluate the safety and effectiveness of surgery using scleral expansion bands.

Large sample study of the effects of phenylephrine 2.5% eyedrops on the amplitude of accommodation in man

A single drop of phenylephrine 2.5% (MYDFRIN ^TM) was instilled into the eyes of 160 volunteers (aged 20 to 30 years) and their amplitude of accommodation assessed under standard illumination using a push-up technique without an artificial pupil- The amplitude was assessed every 5 or 10 min over a period of 90 min. Within 30 min, nearly 75% of the subjects showed a measurable change in amplitude. Overall, the amplitude declined slowly with time to realize an average 11 % reduction from an average starting amplitude of 10.7 D. A large range of responses from a 30% increase to a 60% decrease in amplitude was. however, observed. Subjects with large amplitudes of accommodation were more likely to show significant decreases while some subjects with smaller amplitudes showed an apparent increase in accommodation ( r ²= 0.176). The phenomenon was observed in both blue- and brown-eyed subjects and in non-contact lens wearers and soft contact lens wearers ( r ² values of 0.144 to 0.265).     

MEASUREMENT OF ACCOMMODATIVE AMPLITUDE IN AMBLYOPIA

Abstract Monocular accommodative amplitudes were measured in amblyopic individuals by the subjective minus lens push-up techniques and by the objective dynamic retinoscopy. Accommodative amplitudes were always reduced in amblyopic eyes using the minus lens and retinoscopy techniques, but not with the push-up technique which Inflated this measure, Owing to difficulty in detecting defocused stimuli with the amblyopic eye. it is suggested that the objective retinoscopic technique be used by clinicians for accurate assessment of accommodative amplitude in these patients.     

Tetraflex可调节人工晶状体临床应用的初步观察

目的 观察白内障超声乳化联合囊袋内可调节人工晶状体植入术的效果.方法 病例对照研究.全部患者行白内障超声乳化联合囊袋内人工晶状体植入术,根据植入人工晶状体的不同分为试验组:22例(30只眼)植入可调节人工晶状体,对照组:22例(29只眼)植入单焦点人工晶状体.观察并记录术后6个月和12个月时术眼远、近视力,主观调节幅度,应用OCULUS Pentacam三维前段分析仪测量2%毛果芸香碱眼液诱导前后的前房深度变化值.各观察指标数据以均数±标准差表示.使用SPSS13.0软件对数据进行分析.采用两组独立样本t检验比较两组各观察指标,以P<0.05为差异有统计学意义.结果 术后随访期间,试验组患者的裸眼近视力和最佳远视力矫正后的近视力与对照组患者相比,有统计学差异(P=0.000),两组患者的最佳矫正视力差异无统计学意义(P>0.05);术后6个月时,应用主观移近法测得的主观调节幅度,试验组为(1.60±0.57)D,对照组为(1.10±0.70)D.前房深度变化值试验组为(0.50±0.37)mm,对照组为(0.08±0.06)mm.术后12个月时,应用主观移近法测得的主观调节幅度,试验组为(1.38±0.52)D,对照组为(1.06±0.61)D.前房深度变化值试验组为(0.30±0.27)mm,对照组为(0.10±0.09)mm.结论 与传统的单焦点人工晶状体相比,Tetraflex可调节人工晶状体可以为患者提供较好的近视力和主观调节幅度,但远期疗效有下降趋势.     

Accommodation measurements in a prepresbyopic and presbyopic population

PURPOSE: To study the efficacy of several subjective and objective methods of accommodation measurement in normal prepresbyopic and presbyopic populations to identify appropriate methods for measuring the outcome of accommodative restorative procedures. SETTING: University of Houston, College of Optometry, Houston, Texas, USA. Methods: Thirty-one normal subjects with a mean age of 43.7 years (range 31 to 53 years) participated. Accommodation was measured monocularly using 3 subjective approaches--the push-up test, minus lenses to blur, and a focometer--and 2 approaches measured with a Hartinger coincidence refractometer, in which accommodation was stimulated with minus lenses to blur and topical pilocarpine 6%. RESULTS: The push-up method overestimated accommodative amplitude relative to objective measures in 28 subjects. Two subjective methods, minus lenses to blur and the focometer, produced comparable results, but with lower amplitudes in younger subjects and higher amplitudes in older subjects compared with objective methods. Comparable results were obtained when accommodation was stimulated in 1 of 2 ways and measured with the Hartinger. Pilocarpine elicited stronger accommodative responses than distance blur for subjects with low accommodative amplitudes. Pilocarpine 6% produced stronger responses in subjects with light irides than in those with dark irides. CONCLUSIONS: Hartinger-measured accommodation provides more realistic measurement of accommodative amplitude than the subjective methods tested, especially in the presbyopic population. In presbyopic subjects, the subjective tests resulted in accommodative amplitudes up to 4.0 diopters greater than those measured with objective tests. Measurements of accommodative amplitude are best achieved with objective methods to stimulate and measure accommodation.     

Anterior segment changes with age and during accommodation measured with partial coherence interferometry

PURPOSE: To evaluate anterior segment alterations with age and during accommodation in different age groups. SETTING: Department of Ophthalmology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary. METHODS: Fifty-three subjects (101 normal eyes) were enrolled in this study and divided into 3 age groups: younger than 30 years (Group 1), between 31 years and 44 years (Group 2), and older than 45 years (Group 3). The total amplitude of accommodation was determined with a defocusing technique, and anterior segment measurements were performed by partial coherence interferometry. RESULTS: Group 1 comprised 32 eyes; Group 2, 37 eyes; and Group 3, 32 eyes. The total amplitude of accommodation decreased with age (P<.0001). With the target position at infinity, the lens thickness (LT) and anterior segment length (ASL) increased and the anterior chamber depth (ACD) decreased significantly with age (P<.0001). During accommodation in the youngest group, the mean change in LT was 36.3 mum/diopter (D) and in ACD, -26.7 mum/D. The mean accommodation-induced ACD change was -0.08 mm +/- 0.06 (SD) in Group 1, -0.064 +/- 0.087 mm in Group 2, and -0.03 +/- 0.06 mm in Group 3 (P = .0004). The mean LT change during near fixation was 0.109 +/- 0.063 mm in Group 1, 0.103 +/- 0.136 mm in Group 2, and 0.006 +/- 0.05 mm in Group 3 (P<.0001). The mean ASL change during accommodation was 0.029 +/- 0.037 mm, 0.039 +/- 0.114 mm, and -0.023 +/- 0.051, respectively (P<.0001). CONCLUSIONS: In addition to forward movement of the anterior lens surface with age, the posterior surface moved backward. Alterations in LT and ACD sufficient for a unit of refractive power change during accommodation might be smaller than previously thought. Anterior shifting of the lens may also participate in the accommodative response.     

The fluctuations of accommodation and ageing

Objective The aim of this study was to investigate the influence of age on the fluctuations of accommodation.
Method Fluctuations of accommodation were measured on six 'young' (16–25 years, mean age 22 years) observers and six 'older' (35–48 years, mean age 42 years) observers. Accommodation was continuously recorded using a SRI optometer whilst the observers steadily viewed a high contrast target at stimulus levels 0.25 D, 1.00 D and 2.00 D. Fluctuations were quantified using power spectrum analysis, and frequencies were grouped into bands: low (LFC 0.3–0.6 Hz and 0.3–0.9 Hz) and high (HFC 1.1–2.2 Hz).
Results Accommodation response levels for these stimuli for both groups of observers were quite similar. Fourier analysis was used to generate power spectra so that the fluctuations of accommodation for each observer group could be compared. In general power increased for increasing response levels for both groups of observers, although less power was evident for the older observers in both LFC and HFC bands. Differences in power were not significant at these frequency bands for the two observer groups. When the whole power spectrum is compared these differences became significant with more power evident in the younger cohort.
Conclusion Reductions in both amplitude and speed of accommodation with age are well known, and the decline in magnitude of the fluctuations found here is consistent with a general diminution in accommodation dynamics as the accommodation mechanism ages. For the older group, some of who were near absolute presbyopia, there may be little contribution to power from changes in lens shape and it is possible that small changes in lens position in the eye contribute to the power spectrum.     

托品酰胺滴眼液对眼睫状肌麻痹效果的客观观察

目的通过客观观察托品酰胺滴眼液的睫状肌麻痹效果．尝试对临床上如何更科学地使用托品酰胺滴眼液进行验光检查作出客观评价和指导。方法利用移近法、负镜法、“shin-Nippon Auto-Refractor”三种主客观方法测量21例（42眼）受试者在滴用托品酰胺后的调节幅度变化情况，分析托品酰胺的睫状肌麻痹效果和药效动力学。结果使用客观测量方法评价托品酰胺的药效动力学时．最佳睫状肌麻痹效果在第一次滴药后第45分钟出现残余调节M=（0．40±0．26）D，在同一时间用移近法所得的平均残余调节M=（1．80±0．60）D，负镜法所得的平均残余调节M=（1．62±0．42）D，三种方法测量残余调节的结果显示主观与客观测量方法之间差异有显著性（P〈0．05）。结论0．5％托品酰胺滴眼液是一种有效的睫状肌麻痹剂，适合正常人群（含轻度近视）眼科屈光检查时使用，同时应注意主观调节检查的缺陷，尽量使用客观检查结果作为科研依据。     

Pseudophakic accommodation with translation lenses – dual optic vs mono optic

PURPOSE: To investigate the pseudophakic accommodation effect in dual and mono optic translation accommodative intraocular lenses (AIOL) using linear matrix methods in the paraxial space. METHODS: Dual (anterior optic of power +32 D linked to a compensatory posterior optic of negative power) and mono lens power was determined in the non-accommodated state using linear geometric optics based on the Gullstrand model eye. The position of the AIOL was calculated from a regression formula. Pseudophakic accommodation was assessed with three systems: (1) forward shift of the mono optic lens, (2) anterior translation of the anterior optic in the dual optic lens system with an unchanged position of the posterior minus lens and (3) symmetrical anterior and posterior translation of the anterior and posterior lens. The Gullstrand model eye was modified by changing the axial length (and proportionally changing the phakic anterior chamber depth) to investigate the accommodative effect in myopic and hyperopic eyes. RESULTS: The dual optic lens system (2) yields a nearly constant accommodation amplitude of 2.4-2.5 D mm(-1) movement over the total range of axial lengths. The mono optic lens (1) provides a higher accommodative effect only in extremely short eyes (high refractive power of the lens), whereas for normal eyes (1.4-1.5 D mm(-1) movement) and for long (myopic) eyes the accommodative effect is much less than the dual optic lens. The dual optic lens system under condition (3) yields less accommodation amplitude compared with the dual optic system under condition (2) over the total range of axial length but provides higher accommodation amplitude compared with the mono optic lens system (1) with axial lengths greater than 22.3 mm (lens power 25.5 D). In the accommodated state, with lens translation of 1 mm, the absolute value of the lateral magnification increases with the refractive power of the mono optic lens (1) and decreases in both dual optic lens systems (under conditions 2 and 3). CONCLUSIONS: A mathematical strategy is presented for calculation of the accommodative effect of mono-optic and dual optic AIOL. The dual optic lens yielded a nearly constant accommodation amplitude of about 2.4-2.5 D mm(-1) translation, whereas the mono optic lens yielded an accommodative response of <2 D mm(-1) translation in long myopic or normal eyes. Only in extremely short eyes is the accommodative amplitude of the mono-optic lens higher than the dual optic lens.     

Amplitude of accommodation in Zairian subjects

The authors studied the amplitude of accommodation in Zairian patients who consulted the Ophthalmic Clinic of University of Kinshasa from February 24 to July 31, 1986. During this period, of 1326 Zairians seen, 159 (318 eyes) were included in this study. Patients with monocular visual acuities less than 10/10, or with ocular pathology, astigmatisms and anisometropias exceeding one diopter were excluded from the study. The mean age +/- SD was 32 years +/- 12 with a range of 10 to 58 years. There were 101 males and 58 females. The measurements were performed, once for each patient, with Osterberg Bino-Oculus apparatus according to the "push-up" method and the plus spherical method. The amplitude of accommodation decreased with the age. This decrease was more notable between 30 and 40 years. The age of onset of presbyopia calculated from the amplitude of accommodation according to the "push-up" method was 39 years. The values of the amplitude of accommodation obtained by the both methods could be superposed (p greater than 0.05). They were similar to those of black patients and were also inferior to the white patients obtained by other authors.     

Aging changes in apparent accommodation in eyes with a monofocal intraocular lens

PURPOSE: To examine the aging changes in the amplitude of apparent accommodation in eyes with a monofocal intraocular lens (IOL). DESIGN: Prospective comparative observational study. METHODS: Two hundred eyes of 200 patients who were scheduled for phacoemulsification and monofocal IOL implantation were studied. Forty patients in each of five age groups-younger than 40 years of age or in their 50s, 60s, 70s, and 80s-were prospectively recruited. Using an accommodopolyrecorder, the amplitude of apparent accommodation of these patients was measured approximately 1 month after surgery. Visual acuities from far to near distances after best-corrected distance were examined using an all-distance vision tester, and the region of accommodation at which each patient achieved a visual acuity of 20/29 or 20/40 was determined and converted to the diopteric range. Contrast sensitivity was also examined using a vision contrast test system. RESULTS: The amount of apparent accommodation as measured with the accommodopolyrecorder was decreased significantly in proportion to patient age (P <.0001). Furthermore, significant negative correlation was found between the amount of apparent accommodation and actual age of each patient (r = -.491). The diopteric range of accommodation at which the patients achieved 20/29 or 20/40 also reduced in proportion to the age. Although no significant differences were found in the mean far visual acuities between age groups, the intermediate and near visual acuities worsened significantly with age. The contrast sensitivity was also reduced in proportion to the age. CONCLUSIONS: The amplitude of apparent accommodation in eyes with a monofocal IOL decreases significantly in proportion to age, resulting in worsening of best-corrected intermediate and near visual acuities.     

Slit-lamp studies of the rhesus monkey eye: II. Changes in crystalline lens shape, thickness and position during accommodation and aging

Changes in crystalline lens shape and axial thickness, anterior chamber depth and anterior cornea-posterior lens distance during accommodation induced by corneal iontophoresis of carbachol or electrical stimulation of the Edinger-Westphal nucleus were studied in 25 living, surgically aniridic rhesus monkey eyes, aged 1-25 years. Intraocular distances and anterior and posterior lens surface curvatures were evaluated from slit-lamp Scheimpflug photographs; distances were also determined by A-scan ultrasonography. With increasing accommodation, both lens surfaces become more sharply curved, the lens thickens and the anterior chamber shallows, while the posterior lens surface remains fixed relative to the cornea. Within statistical limits, the respective curvature and distance changes are the same for a given dioptric accommodation induced by either stimulation technique. The respective intraocular distance-accommodation relationships are identical whether derived from photographic or ultrasonographic measurements. Temporal and contralateral reproducibility of all measurements is excellent. Each parameter-accommodation relationship is strikingly linear in all eyes, although above 20 D the slopes of the lens surface curvature-accommodation relationships may have decreased. The curvature change per D of accommodation averages approximately 20% more for the posterior than for the anterior lens surface. There is relatively little interindividual variation in the slope of each relationship despite the significant interindividual differences in age and accommodative amplitude, indicating that the relationships are independent of age. However, when extrapolated back to the non-accommodated resting state, the data indicate that the lens thickens, both its surfaces become more sharply curved, and the anterior chamber shallows with age in adult greater than 5 years, while opposite trends are seen in younger animals.     

Simultaneous measurements of refraction and A-scan biometry during accommodation in humans.

PURPOSE: Accommodation is a dioptric change in power of the crystalline lens resulting from ciliary muscle contraction that leads to an increase in lens surface curvatures and thickness and changes in the position of lens surfaces. Previous studies have used A-scan ultrasound to measure changes in the position of lens surfaces with voluntary accommodation, but have not simultaneously measured the change in refraction. The goal of this study is to simultaneously measure and correlate refractive and biometric changes in the lens during voluntary accommodation in humans. METHODS: Refraction was measured off-axis in the right eye and biometry on-axis in the left eye simultaneously during voluntary accommodation in 22 human subjects between the ages of 21 and 30 years (mean +/- standard deviation: 25.8 +/- 2.3 years). Subjects viewed a distant target and four near targets spanning the full accommodative range available to evaluate refraction and lens surface position at each accommodative state. RESULTS: Maximum objectively measured accommodative amplitude of all subjects was 5.64 +/- 0.21 D (mean +/- standard error of mean). Biometric and refractive changes during accommodation were linearly correlated. The mean +/- standard error of mean decrease in anterior chamber depth was 0.051 +/- 0.008 mm/D, increase in lens thickness was 0.067 +/- 0.008 mm/D, and increase in anterior segment length was 0.017 +/- 0.005 mm/D during accommodation. There was a net anterior movement of the lens center of 0.017 +/- 0.005 mm/D. CONCLUSION: Anterior chamber depth, lens thickness, and anterior segment length change linearly with refraction during accommodation. Per-diopter changes in the lens were greater in the current study compared with previous studies in which only accommodative demand was measured, which overestimates the accommodative response.