Impact of accommodative insufficiency and accommodative/vergence therapy on ciliary muscle thickness in the eye.

PURPOSE: Recent evidence suggests that the ciliary muscle apical fibres are most responsive to accommodative load; however, the structure of the ciliary muscle in individuals with accommodative insufficiency is unknown. This study examined ciliary muscle structure in individuals with accommodative insufficiency (AI). We also determined the response of the ciliary muscle to accommodative/vergence therapy and increasing accommodative demands to investigate the muscle's responsiveness to workload. METHODS: Subjects with AI were enrolled and matched by age and refractive error with subjects enrolled in another ciliary muscle study as controls. Anterior segment optical coherence tomography was used to measure the ciliary muscle thickness (CMT) at rest (0D), maximum thickness (CMTMAX) and over the area from 0.75 mm (CMT0.75) to 3 mm (CMT3) posterior to the scleral spur of the right eye. For those with AI, the ciliary muscle was also measured at increasing levels of accommodative demand (2D, 4D and 6D), both before and after accommodative/vergence therapy. RESULTS: Sixteen subjects with AI (mean age = 17.4 years, SD = 8.0) were matched with 48 controls (mean age = 17.8 years, SD = 8.2). On average, the controls had 52-72 µm thicker ciliary muscles in the apical region at 0D than those with AI (p = 0.03 for both CMTMAX and CMT 0.75). Differences in thickness between the groups in other regions of the muscle were not statistically significant. After 8 weeks of accommodative/vergence therapy, the CMT increased by an average of 22-42 µm (p ≤ 0.04 for all), while AA increased by 7D (p < 0.001). CONCLUSIONS: This study demonstrated significantly thinner apical ciliary muscle thickness in those with AI and that the ciliary muscle can thicken in response to increased workload. This may explain the mechanism for improvement in signs and symptoms with accommodative/vergence therapy.

Ciliary muscle thickness in adults with Down syndrome.

PURPOSE: The relationship between ciliary muscle thickness (CMT), age and refractive error was investigated to determine if CMT, like other anterior ocular anatomy, differs in adults with Down syndrome (DS). METHODS: The CMT of 33 adults with DS was imaged using anterior segment optical coherence tomography. Images from the right eye obtained 45 minutes after cycloplegia (1% tropicamide, 2.5% phenylephrine) were analysed to calculate thickness at 1, 2 and 3 mm posterior to the scleral spur (CMT1, CMT2, CMT3), maximum thickness (CMTMAX) and apical thickness (AT = CMT1 - CMT2). Spherical equivalent refractive error was determined by clinical refraction using both non-dilated and dilated measures. Multivariate regression analysis evaluated the relationship between CMT and refractive error while controlling for subject age. RESULTS: Images were analysed from 26 subjects (mean age (SD) 29 years; mean refractive error (SD): -0.90 (5.03) D, range: -15.75 to +5.13D). Mean (SD) CMT decreased with posterior position (CMT1: 804 (83) µm; CMT2: 543 (131) µm; CMT3: 312 (100) µm). Mean (SD) CMTMAX and AT was 869 (57) µm and 260 (84) µm, respectively. There was a significant linear correlation indicating thinning CMT with increasing age for CMT1 and CMT2 (p ≤0.05). CMT2 and CMT3 had a significant negative correlation (thicker muscle with increasing myopic refractive error) (p ≤0.01). AT had a significant positive correlation (thicker muscle with increasing hyperopic refractive error) (p <0.01). CONCLUSIONS: Ciliary muscle thickness in participants with DS was found to be in a similar range with similar refractive error trends to previous reports of individuals without DS. However, it is important to note that the refractive error trends were driven by individuals with moderate to high levels of myopia.

A randomised clinical trial of multifocal contact lenses and contact lens discomfort.

PURPOSE: To determine how multifocal contact lenses affect contact lens discomfort. METHODS: This randomised, participant-masked, crossover clinical trial fitted 84 uncomfortable soft contact lens wearers (30-40 years old) with single vision and multifocal contact lenses. Contact lens discomfort was assessed using the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8). RESULTS: There was no difference between multifocal and single vision survey scores (p = 0.08). There was an interaction between lens type and age group (p = 0.05). CLDEQ-8 scores with the single vision lens were less symptomatic than multifocal scores in participants <35 years old (p = 0.01). Single vision and multifocal scores for the older age group were not different. Subjectively, those in the <35 year-old age group preferred the single vision lens for intermediate (p = 0.02), distance (p = 0.003), and overall vision (p = 0.002). In the ≥35 year-old age group, no lens was significantly preferred for vision. CONCLUSIONS: Participants in the younger age group had more favourable wearing experiences with the single vision lens compared to the multifocal lens. The older age group, however, had similar wearing experiences with both lens types. While younger contact lens wearers may prefer the wearing experience with single vision lenses, some uncomfortable contact lens wearers approaching 40 years old may benefit from wearing a multifocal contact lens sooner in life than is typically practised.

A study of contact lens compliance in a non-clinical setting.

PURPOSE: To evaluate soft contact lens replacement, overnight (ON) wear, and contact lens case compliance in a non-clinical sample. METHODS: Subjects (n = 297) were recruited at the Center for Science and Industry (COSI) in Columbus, Ohio. Adult (≥ 18 years) soft contact lens wearers completed a survey about contact lens replacement, ON contact lens wear, and contact lens case replacement habits. RESULTS: Two-week replacement lenses (according to the manufacturer's replacement schedule [MRS]) were most common (45.5%), followed by monthly (34.3%) and daily replacement (20.2%). Non-compliance with replacement schedule was reported in 38.7% of subjects. Age (p = 0.02), years of lens wear (p = 0.02), and MRS (p <0.0001) affected replacement compliance. Post-hoc analysis showed daily replacement wearers were more compliant than two-week (p <0.0001) and monthly (p <0.0001) replacement wearers with prescribed lens replacement. Non-compliance with prescribed ON wear was reported in 23.9% of subjects. Subjects who were non-compliant with lens replacement were more likely to be non-compliant with ON wear (p = 0.02) and had worn contact lenses for less time (p = 0.02). Of the subjects who used contact lens cases, 74.6% were unsure when they should replace their case. Frequency of case replacement was not associated with age (p = 0.5), gender (p = 0.5), years of contact lens wear (p = 0.7), MRS (p = 0.4), replacement compliance (p = 0.3), or ON wear compliance (p = 0.7). CONCLUSIONS: Daily replacement wearers were most likely to be compliant with contact lens replacement, but all subjects, including daily replacement wearers, had similar ON wear non-compliance. Non-compliant lens replacement was associated with non-compliant ON wear, but contact lens case replacement was not related to either compliance category. The majority of subjects had no knowledge of proper contact lens case replacement, despite compliance in other categories.

Presbyopic and non-presbyopic contact lens opinions and vision correction preferences.

PURPOSE: To compare vision correction preferences, refractive error, and gender of non-presbyopes and presbyopes. METHODS: Adults who wear spectacles or contact lenses completed a survey about refractive correction opinions and refractive error was measured. RESULTS: Of the 304 subjects, 38.2% were presbyopic (≥40 years) and 59.2% were female. Spectacles were the primary vision correction for 78.0% of subjects. Compared to contact lens wearers, the proportion of presbyopes was higher (p=0.006) in spectacle wearers. There was no difference in the proportion of presbyopes and non-presbyopes who have tried contact lenses (p=0.2) or who would prefer to wear contact lenses (p=0.2). In contact lens wearers, there was no difference in the proportion of presbyopes and non-presbyopes with a history of temporary discontinuation (p=0.9). Within the contact lens wearing group, there was no refractive error difference between presbyopes and non-presbyopes (spherical equivalent p=0.6; power vector J0 p=0.5; power vector J45 p=0.4; anisometropia p=0.2). Overall, contact lens wearers were more likely to be female (p=0.004). There was no difference in gender in presbyopic and non-presbyopic contact lens wearers (p=0.5). CONCLUSIONS: Presbyopes and non-presbyopes have similar opinions about spectacles and contact lenses. Presbyopes of all refractive errors prefer contact lens correction when good vision and comfort can be achieved. Eye care providers should not assume that presbyopia, refractive error, or gender are factors that preclude a patient from being interested in contact lens wear.

A Survey of Presbyopic Contact Lens Wearers in a University Setting.

PURPOSE: To determine why presbyopic patients discontinue contact lens wear and describe their opinions of comfort and visual quality with contact lenses. METHODS: A survey assessing current age, gender, contact lens material/design, and opinions of contact lens comfort and visual quality was mailed to 2400 presbyopic patients (age 40 years and older) that have had eye exams in the Ohio State University College of Optometry's Contact Lens Services over the last 4 years. RESULTS: A total of 496 surveys were analyzed. The mean age of survey respondents was 57 ± 9 years, and 68% of the sample was female. Permanent discontinuation of contact lens wear was reported by 15%. No association was found between contact lens discontinuation and age (p = 0.7), gender (p = 0.2), age of beginning contact lens wear (p = 0.1), or contact lens material (p = 0.1). Poor vision (38%), discomfort (34%), convenience (20%), and cost (6%) were the primary reported reasons for discontinuation. There was no difference between the proportion of subjects reporting "poor vision" as their primary discontinuation reason and those reporting "discomfort" (p = 0.7). Discontinued wearers had a worse overall opinion of their distance (p = 0.03), intermediate (p = 0.01), and near vision (p = 0.002) compared to subjects who were still wearing their contact lenses. CONCLUSIONS: Discomfort has been reported as the primary reason for contact lens discontinuation. In this presbyopic population, dissatisfaction with vision and discomfort were reported equally as often as primary reasons for discontinuation. As well, subjects who ceased contact lens wear had worse overall opinions of their vision at all distances than current contact lens wearers. The results of this survey suggest that presbyopes have unique demands and opinions related to contact lens wear.

Can Binocular Vision Disorders Contribute to Contact Lens Discomfort?

PURPOSE: To determine the relationship between binocular vision (BV) disorder and dry eye symptoms and the frequency of BV disorders in subjects with contact lens-induced dry eye symptoms. METHODS: Subjects recruited for a larger dry eye study (n = 104) completed the Ocular Surface Disease Index (OSDI) and Convergence Insufficiency Symptom Survey (CISS) to determine if symptoms assessed on these two surveys were related. Also, myopic soft contact lens wearers (n = 29) with self-reported dry eye symptoms were recruited. Subjects completed the OSDI and CISS to assess severity of dry eye and BV disorder symptoms. Basic BV and dry eye testing was performed on each subject. RESULTS: Severity of symptoms assessed on the OSDI and CISS was found to be significantly correlated in the larger subject group (ρ = 0.68, p = 0.0001). This significant correlation warranted further investigation of both symptoms and clinical signs. In the group of myopic soft contact lens wearers, 48.3% had a BV disorder. This proportion appeared to be higher than previously reported prevalence estimates of BV disorders. Accommodative lag greater than or equal to 1.00 diopter was the most common BV disorder sign encountered (48.3%), and pseudo-convergence insufficiency was the most common BV disorder (31.0%). CONCLUSIONS: Symptoms related to dry eye and BV disorders overlap. Subjects with symptoms of discomfort while wearing soft contact lenses may be experiencing a concurrent or stand-alone BV disorder. Accommodative insufficiency and pseudo-convergence insufficiency were common in the sample of myopic soft contact lens wearers. Clinicians should screen symptomatic contact lens-induced dry eye patients for BV disorders. Dry eye studies should assess basic BV function.

Four characteristics and a model of an effective tear film lipid layer (TFLL).

It is proposed that a normal, effective tear film lipid layer (TFLL) should have the following four characteristics: 1) high evaporation resistance to prevent water loss and consequent hyperosmolarity; 2) respreadability, so it will return to its original state after the compression-expansion cycle of the blink; 3) fluidity sufficient to avoid blocking secretion from meibomian glands; 4) gel-like and incompressible structure that can resist forces that may tend to disrupt it. These characteristics tend to be incompatible; for example, lipids that form good evaporation barriers tend to be disrupted by compression-expansion cycles. It is noted that clues about the function and organization of the TFLL can be obtained by comparison with other biological lipid layers, such as lung surfactant and the lipid evaporation barrier of the skin. In an attempt to satisfy the conflicting characteristics, a "multilamellar sandwich model" of the TFLL is proposed, having features in common with the skin evaporation barrier.

Ciliary muscle thickness in anisometropia.

PURPOSE: The purpose of this study was to investigate the relationships between ciliary muscle thickness (CMT), refractive error, and axial length both across subjects and between the more and less myopic eyes of adults with anisometropia. METHODS: Both eyes of 29 adult subjects with at least 1.00 D of anisometropia were measured. Ciliary muscle thickness was measured at the maximum thickness (CMTMAX) and at 1.0 (CMT1), 2.0 (CMT2), and 3.0 mm (CMT3) posterior to the scleral spur, and also at the apical region (Apical CMTMAX = CMTMAX - CMT2, and Apical CMT1 = CMT1 - CMT2). Multilevel regression models were used to determine the relationship between the various CMT measures and cycloplegic refractive error or axial length, and to assess whether there are CMT differences between the more and less myopic eyes of an anisometropic adult. RESULTS: CMTMAX, CMT1, CMT2, and CMT3 were negatively associated with mean refractive error (all p ≤ 0.03), and the strongest association was in the posterior region (CMT2 and CMT3). Apical CMTMAX and Apical CMT1, however, were positively associated with mean refractive error (both p < 0.0001) across subjects. Within a subject, i.e., comparing the two anisometropic eyes, there was no statistically significant difference in CMT in any region. CONCLUSIONS: Similar to previous studies, across anisometropic subjects, a thicker posterior region of the ciliary muscle (CMT2 and CMT3) was associated with increased myopic refractive error. Conversely, shorter, more hyperopic eyes tended to have thicker anterior, apical fiber portions of their ciliary muscle (Apical CMTMAX and Apical CMT1). There was no difference between the two eyes for any CMT measurement, indicating that in anisometropia, an eye can grow longer and more myopic than its fellow eye without resulting in an increase in CMT.

Region-specific relationships between refractive error and ciliary muscle thickness in children.

PURPOSE: To determine if there is a relationship between refractive error and ciliary muscle thickness in different muscle regions. METHODS: An anterior segment optical coherence tomographer was used to measure cycloplegic ciliary muscle thicknesses at 1 mm (CMT1), 2 mm (CMT2), and 3 mm (CMT3) posterior to the scleral spur; maximum (CMTMAX) thickness was also assessed. An autorefractor was used to determine cycloplegic spherical equivalent refractive error (SPHEQ). Apical ciliary muscle fibers were obtained by subtracting corresponding CMT2 values from CMT1 and CMTMAX. Multilevel regression models were used to determine the relationship between ciliary muscle thickness in various regions of the muscle and refractive error. RESULTS: Subjects included 269 children with a mean age of 8.71 ± 1.51 years and a mean refractive error of +0.41 ± 1.29 diopters. In linear models with ciliary muscle thicknesses and SPHEQ, SPHEQ was significantly associated only with CMT2 (ß = -11.34, P = 0.0008) and CMT 3 (ß = -6.97, P = 0.007). When corresponding values of CMT2 were subtracted from CMT1 and CMTMAX, apical fibers at CMT1 (ß = 14.75, P < 0.0001) and CMTMAX (ß = 18.16, P < 0.0001) had a significant relationship with SPHEQ. CONCLUSIONS: These data indicated that in children the posterior ciliary muscle fibers are thicker in myopia (CMT2 and CMT3), but paradoxically, the apical ciliary muscle fibers are thicker in hyperopia (CMTMAX and CMT1). This may be the first evidence that hyperopia is associated with a thicker apical ciliary muscle region.

The effect of phenylephrine on the ciliary muscle and accommodation.

PURPOSE: To objectively measure changes in the human ciliary muscle dimensions in vivo after instillation of topical phenylephrine, a mydriatic and vasodilating agent. METHODS: A cross-sectional study of 25 healthy young adults was conducted. Measurements of pupil size, accommodation, and ciliary muscle thickness were made both before and 30 min after instillation of 1% proparacaine and 2.5% phenylephrine. Accommodation was measured in three ways: subjectively using a push-up technique and Royal Air Force (RAF) rule, and objectively using both the Grand Seiko autorefractor and PowerRefractor. Images of the temporal ciliary muscle were acquired using the Visante Anterior Segment Optical Coherence Tomographer (OCT). Ciliary muscle images were objectively analyzed using a computer-based segmentation technique. RESULTS: Amplitude of accommodation using the push-up test was reduced by about 1 D with phenylephrine (p < 0.001). Phenylephrine did not change the accommodative response to a 4 D Badal target as measured by either autorefraction or photorefraction (p > 0.30). There was statistically significant thickening of the anterior region and thinning of the posterior region of the ciliary muscle with accommodation (p < 0.001, all locations). Phenylephrine did not affect either baseline ciliary muscle thickness or the accommodative contraction of the muscle (p > 0.09). CONCLUSIONS: Low-dose phenylephrine does not affect ciliary muscle dimensions, ciliary muscle contractility, or accommodative response to a 4 D near target.

Measuring changes in ciliary muscle thickness with accommodation in young adults.

PURPOSE: To develop a measurement protocol for changes in the shape and size of the ciliary muscle with accommodation using the Zeiss Visante™ anterior segment optical coherence tomography (AS-OCT) and to determine the test-retest repeatability of these measurements. METHODS: Subjects were 25 adults aged 23 to 28 years. The ciliary muscle was imaged at two visits with the Visante™ while accommodative response was monitored during imaging using the PowerRefractor. Ciliary muscle thickness (CMT) was measured at 1 mm (CMT1), 2 mm (CMT2), and 3 mm (CMT3) posterior to the scleral spur and at the point of maximal thickness (CMTMAX). Thickness was measured at these locations while subjects viewed a target at distance and at a 4.00 D accommodative stimulus. Outcome measures were the change in thickness between distance and the 4.00 D stimulus and the change in thickness per diopter of accommodative response (PowerRefractor). Finally, the repeatability measurements between visit 1 and visit 2 were determined with a Bland-Altman analysis. RESULTS: The statistically significant modeled changes in CMT were as follows: CMTMAX = 69.2 µm (4.00 D stimulus) and 18.1 µm (per diopter of accommodation); CMT1 = 45.2 µm (4.00 D stimulus) and 12.3 µm (per diopter of accommodation); and CMT3 = -45.9 µm (4.00 D stimulus) and -12.0 µm (per diopter of accommodation); p < 0.0001 for all. CONCLUSIONS: The combination of the Visante™ and the PowerRefractor is a feasible tool for measuring thickening of ciliary muscle at more anterior locations and thinning at more posterior locations during accommodation. We noted a wide range of accommodative responses during the time of image capture in this study indicating that the most accurate estimates of the change in ciliary muscle dimensions with accommodation may be obtained by using accommodative response rather than stimulus values and by using measurements taken simultaneously with image capture.

Changes in ciliary muscle thickness during accommodation in children.

PURPOSE: To investigate the morphology of the ciliary muscle during the act of accommodation in a population of children. METHODS: Thirty children aged 6 to 12 years were enrolled. Accommodative response was measured through habitual correction. Height was measured as a control variable. Central axial length was measured with the IOLMaster. Four images of the temporal ciliary muscle were taken with the Visante Optical Coherence Tomographer at three different stimulus levels (0, 4, and 6 D) while accommodative response was monitored concurrently with the PowerRefractor. Accommodative response monitoring was time-matched to ciliary muscle image capture, and the mean was calculated for 5 s surrounding this time point. Four cycloplegic images of the temporal ciliary muscle were also taken. Ciliary muscle thickness measurements were made at the point of maximum thickness (CMTMAX) and at 1 mm (CMT1), 2 mm (CMT2) and 3 mm (CMT3) posterior to the sclera spur. RESULTS: Increasing accommodative response was correlated with increases in the thickness of CMTMAX (p = <0.001) and CMT1 (p = <0.001) and decreases in the thickness of CMT3 (p = <0.001). Thicker values of CMTMAX under cycloplegic conditions were significantly correlated with values of CMTMAX (p = <0.001) and CMT1 (p = 0.001) while accommodating and approached significance in modeling CMT3 (p = 0.06). Mean axial length was correlated with the amount of thinning at CMT3 with accommodation (p = 0.002). Axial length was not significantly correlated with thickness values at CMTMAX (p = 0.7) or CMT1 (p = 0.6). CONCLUSIONS: In a manner similar to previous adult studies, ciliary muscle thickness at CMTMAX and CMT1 increased with accommodation and CMT3 thinned with accommodation. Further investigation is necessary to determine whether CMT2 is a "fulcrum" point along the length of the ciliary muscle where the net change with accommodation is always zero or whether that point varies across subjects or with varying levels of accommodative effort.

Vitamin D receptor (VDR) and group-specific component (GC, vitamin D-binding protein) polymorphisms in myopia.

PURPOSE: Epidemiologic evidence indicates that time outdoors reduces the risk of myopia, suggesting a possible role for vitamin D. This case-control study was conducted to determine whether single-nucleotide polymorphisms (SNPs) within VDR at 12q13.11 and GC at 4q12-13 are associated with myopia. METHODS: The primary analysis was conducted on 81 white adult control subjects between 18 and 50 years of age with a spherical equivalent refractive error between +0.50 and +2.00 D in both eyes and less than 1.50 D of astigmatism. Affected myopic subjects were 289 unrelated white adults at least 18 years of age with at least -0.75 D myopia in both principal meridians of both eyes. RESULTS: One SNP within VDR was significantly associated with myopia in the multivariate analysis of the primary sample (rs2853559: odds ratio = 1.99, P = 0.003). In a subsample of less severely myopic white subjects between -0.75 and -4.00 D, three SNPs within VDR were significantly associated in a multivariate model after adjustment for multiple comparisons (rs2239182: odds ratio = 2.17, P = 0.007; rs3819545: odds ratio = 2.34, P = 0.003; rs2853559: odds ratio = 2.14, P = 0.0035), accounting for 12% of model variance over age alone. CONCLUSIONS: Polymorphisms within VDR appear to be associated with low to moderate amounts of myopia in white subjects. Future studies should determine whether this finding can be replicated and should explore the biological significance of these variations with respect to myopia.

Semiautomatic extraction algorithm for images of the ciliary muscle.

PURPOSE: To develop and evaluate a semiautomatic algorithm for segmentation and morphological assessment of the dimensions of the ciliary muscle in Visante Anterior Segment Optical Coherence Tomography images. METHODS: Geometric distortions in Visante images analyzed as binary files were assessed by imaging an optical flat and human donor tissue. The appropriate pixel/mm conversion factor to use for air (n = 1) was estimated by imaging calibration spheres. A semiautomatic algorithm was developed to extract the dimensions of the ciliary muscle from Visante images. Measurements were also made manually using Visante software calipers. Interclass correlation coefficients and Bland-Altman analyses were used to compare the methods. A multilevel model was fitted to estimate the variance of algorithm measurements that was due to differences within- and between-examiners in scleral spur selection vs. biological variability. RESULTS: The optical flat and the human donor tissue were imaged and appeared without geometric distortions in binary file format. Bland-Altman analyses revealed that caliper measurements tended to underestimate ciliary muscle thickness at 3 mm posterior to the scleral spur in subjects with the thickest ciliary muscles (t = 3.6, p < 0.001). The percent variance due to within- or between-examiner differences in scleral spur selection was found to be small (6%) when compared with the variance because of biological difference across subjects (80%). Using the mean of measurements from three images, achieved an estimated interclass correlation coefficient of 0.85. CONCLUSIONS: The semiautomatic algorithm successfully segmented the ciliary muscle for further measurement. Using the algorithm to follow the scleral curvature to locate more posterior measurements is critical to avoid underestimating thickness measurements. This semiautomatic algorithm will allow for repeatable, efficient, and masked ciliary muscle measurements in large datasets.

Accommodative fluctuations, lens tension, and ciliary body thickness in children.

PURPOSE: To investigate the relationship among microfluctuations in accommodation, resting tension on the crystalline lens, ciliary body thickness, and refractive error in children. METHODS: Subjects were 49 children, aged 8 to 15 years. Subjects wore habitual correction over their left eye and an infrared filter over the right eye during accommodative measurements. Monocular accommodation was measured continuously for two, 30-second periods using a PowerRef I at a sampling rate of 25 Hz while subjects viewed a high-contrast target at 0.25 m. The high (1.0 to 2.3 Hz) and low- (0 to 0.6 Hz) frequency components of the power spectrum from a fast Fourier transform of the accommodative response were used in analysis. Resting tension on the crystalline lens was assessed by measuring the amplitude of the oscillations of the crystalline lens after a rightward 20 degrees saccadic eye movement. Ciliary body thickness was measured 2 mm posterior to the scleral spur from images obtained with a Zeiss Visante optical coherence tomography (OCT). Cycloplegic spherical equivalent refractive error was obtained with the Grand Seiko autorefractor. RESULTS: The mean +/- SD spherical equivalent refractive error was -1.00 D +/- 2.25 (range, -6.00 D to +3.44 D). Greater power in the log of the high-frequency component of accommodative microfluctuations was associated with thinner ciliary bodies (p = 0.03) and lower ages (p = 0.0004). More hyperopic refractive errors with greater power in the high-frequency component (p = 0.0005) and the low-frequency component (p = 0.02). No statistically significant relationship was found for the low-frequency component or root mean square of accommodative microfluctuations and refractive error. CONCLUSIONS: High-frequency microfluctuations of accommodation appear to be suppressed with thicker ciliary bodies. These variations in accommodation need to be observed in a longitudinal study to better assess the functional significance of their relationship to ciliary body size and refractive error.

Validation of optical coherence tomography-based crystalline lens thickness measurements in children.

PURPOSE: To evaluate the validity and repeatability of crystalline lens thickness measurements obtained by anterior segment optical coherence tomography (OCT). METHODS: Forty-seven normal children (mean age, 11.06 +/- 2.30 yr) had their crystalline lens thickness measured with the Visante anterior segment OCT (Carl Zeiss Meditec, Dublin, CA) and with conventional corneal touch A-scan ultransonography (ultrasound) (Humphrey 820). The subjects' right corneas were anesthetized, and their right eyes were cyclopleged. Five ultrasound measurements were recorded per eye, and three Visante OCT measurements were recorded per eye. Thirty-eight subjects had measurements at a second visit where three additional Visante OCT measurements were recorded. RESULTS: The mean of the differences between the Visante OCT and ultrasound was -0.045 mm (p = 0.017) with 95% limits of agreement from -0.29 to 0.20 mm, indicating that the measurement of crystalline lens thickness was slightly thinner with the Visante OCT. When validity was assessed using only Visante OCT images that contained the corneal reflex, the mean of the differences was 0.019 mm (p = 0.11) with 95% limits of agreement from -0.091 to 0.13 mm. For the repeatability of the Visante OCT, the mean of the differences between visit one and visit two was -0.008 mm (p = 0.25) with 95% limits of agreement from -0.088 to 0.072 mm. Repeatability improved when reassessed using only images that contain the corneal reflex; the mean of the differences was -0.0001 mm (p = 0.97) with 95% limits of agreement from -0.030 to 0.030 mm. CONCLUSION: The Visante OCT is a non-contact instrument that is simple to use, and it provides valid crystalline lens thickness measurements with excellent repeatability. Validity and repeatability are optimized when the Visante OCT images contain the corneal reflex and a consistent corneal index refraction is applied to the entire image.

Ciliary body thickness and refractive error in children.

PURPOSE: To determine whether ciliary body thickness (CBT) is related to refractive error in school-age children. METHODS: Fifty-three children, 8 to 15 years of age, were recruited. CBT was measured from anterior segment OCT images (Visante; Carl Zeiss Meditec, Inc., Dublin, CA) at 1 (CBT1), 2 (CBT2) and 3 (CBT3) mm posterior to the scleral spur. Cycloplegic refractive error was measured with an autorefractor, and axial length was measured with an optical biometer. Multilevel regression models determined the relationship between CBT measurements and refractive error or axial length. A Bland-Altman analysis was used to assess the between-visit repeatability of the ciliary body measurements. RESULTS: The between-visits coefficients of repeatability for CBT1, -2, and -3 were 148.04, 165.68, and 110.90, respectively. Thicker measurements at CBT2 (r = -0.29, P = 0.03) and CBT3 (r = -0.38, P = 0.005) were associated with increasingly myopic refractive errors (multilevel model: P < 0.001). Thicker measurements at CBT2 (r = 0.40, P = 0.003) and CBT3 (r = 0.51, P < 0.001) were associated with longer axial lengths (multilevel model: P < 0.001). CONCLUSIONS: Thicker ciliary body measurements were associated with myopia and a longer axial length. Future studies should determine whether this relationship is also present in animal models of myopia and determine the temporal relationship between thickening of the ciliary muscle and the onset of myopia.

Outcomes of LASIK for myopia with FDA-approved lasers.

PURPOSE: To report expected outcomes of laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism from existing US Food and Drug Administration (FDA) data. METHODS: Data from Summaries of Safety and Effectiveness for each of the 12 lasers approved by the FDA for LASIK for myopia or myopic astigmatism between 1998 and 2004 were recorded from the FDA Web site. The Cochran-Armitage test for trend was used to determine whether improvements in outcomes occurred with laser technology changes. RESULTS: For all patients, there was a statistically significant trend toward improvement with improved laser technology in the proportion of patients with uncorrected visual acuity (UCVA) of 20/20 or better, UCVA of 20/40 or better, results within +/-0.50 D of intended correction, results within +/-1.00 D of the intended correction, and night vision symptoms (all P < 0.0002). Because there were preoperative differences across laser types, subgroup analyses were also completed. The results for subgroup analyses (high myopia, low to moderate myopia, spherical myopia, and myopic astigmatism) for visual acuity and refractive error outcomes were similar to results for analyses for all groups combined. Conversely, there was no difference across laser types in the proportion of patients who experienced dry eye symptoms or for the proportion of patients with low to moderate myopia who experienced night vision symptoms that were worse or significantly worse than before LASIK. CONCLUSIONS: LASIK provides excellent visual acuity and refractive error outcomes. Night vision and dryness symptoms still occur in a significant proportion of patients. Future studies should seek to determine whether additional changes in technology, patient selection criteria, or postoperative treatment could reduce or eliminate these symptoms.