Biomedical subjects

G Lynn Mitchell

Publications and source records attributed to G Lynn Mitchell.

At least 37 records · Page 2Linked to original sources

PubMed2005

The effect of overnight contact lens corneal reshaping on higher-order aberrations and best-corrected visual acuity.

PURPOSE: The purpose of this study is to determine the effect of higher-order aberrations after Corneal Refractive Therapy (CRT) on best-corrected visual acuity (BCVA) and the impact of pupil size on BCVA. METHODS: High-contrast (HC) and low-contrast (LC) Bailey-Lovie BCVA was measured in the morning before and after pupil dilation on 20 myopes (mean spherical equivalent -3.11 D +/- 0.96 D) under age 40. BCVA was measured again in the afternoon after dilation. Dilated am and pm aberrations were measured using the Complete Ophthalmic Analysis System (WaveFront Sciences). Patients were fit with CRT lenses in each eye. One month after finalizing the lens fit, BCVA and aberration testing were repeated. Average higher-order RMS error (third to sixth order), spherical aberration, third-, fourth-, fifth-, and sixth-order RMS error were calculated at each visit for a 3-mm and 5-mm pupil. BCVA and aberration data were analyzed using a repeated measures analysis of variance. Linear regression was used to describe the relationship between aberrations and BCVA reductions after CRT. RESULTS: Mean refractive error changed by +3.33 D +/- 0.96 D. No clinically significant changes were found in HC BCVA post-CRT, whereas LC BCVA reductions of 0.07 logarithm of the minimum angle of resolution (logMAR) (nondilated, p = 0.002) and 0.12 logMAR (dilated, p < 0.001) were found. No additional decrease in HC BCVA was found after pupil dilation, whereas a mean additional decrease of 0.08 logMAR in LC BCVA was found with dilation post-CRT (p = 0.013). Higher-order RMS error increased for both 3-mm and 5-mm pupils (p < 0.0001) and remained stable between measurements. Spherical aberration increased for 5-mm pupils after CRT (p < 0.0001). For a 5-mm pupil, a 0.1-mum increase in spherical aberration was associated with an additional decrease in LC BCVA after pupil dilation post-CRT of 0.056 logMAR (R = 0.382, p = 0.004). CONCLUSIONS: CRT results in reduced low-contrast BCVA as a result of increased higher-order aberrations. Higher-order aberrations appear to be relatively stable after CRT. Spherical aberration appears to drive additional low-contrast BCVA losses as pupil size increases.

Adult↗

PubMed2005

A randomized clinical trial of vision therapy/orthoptics versus pencil pushups for the treatment of convergence insufficiency in young adults.

PURPOSE: : The purpose of this article is to compare vision therapy/orthoptics, pencil pushups, and placebo vision therapy/orthoptics as treatments for symptomatic convergence insufficiency in adults 19 to 30 years of age. METHODS: : In a randomized, multicenter clinical trial, 46 adults 19 to 30 years of age with symptomatic convergence insufficiency were randomly assigned to receive 12 weeks of office-based vision therapy/orthoptics, office-based placebo vision therapy/orthoptics, or home-based pencil pushups. The primary outcome measure was the symptom score on the Convergence Insufficiency Symptom Survey. Secondary outcome measures were the near point of convergence and positive fusional vergence at near. RESULTS: : Only patients in the vision therapy/orthoptics group demonstrated statistically and clinically significant changes in the near point of convergence (12.8 cm to 5.3 cm, p = 0.002) and positive fusional vergence at near (11.3Delta to 29.7Delta, p = 0.001). Patients in all three treatment arms demonstrated statistically significant improvement in symptoms with 42% in office-based vision therapy/orthoptics, 31% in office-based placebo vision therapy/orthoptics, and 20% in home-based pencil pushups achieving a score <21 (our predetermined criteria for elimination of symptoms) at the 12-week visit. DISCUSSION: : In this study, vision therapy/orthoptics was the only treatment that produced clinically significant improvements in the near point of convergence and positive fusional vergence. However, over half of the patients in this group (58%) were still symptomatic at the end of treatment, although their symptoms were significantly reduced. All three groups demonstrated statistically significant changes in symptoms with 42% in office-based vision therapy/orthoptics, 31% in office-based placebo vision therapy/orthoptics, and 20% in home-based pencil push-ups meeting our criteria for elimination of symptoms.

Adult↗

PubMed2005

Corneal asphericity and apical curvature in children: a cross-sectional and longitudinal evaluation.

PURPOSE: The contour of the human cornea is closely modeled by a conic section, which is fully described by asphericity (Q) and apical radius of curvature (r(o)). The relationship between corneal shape and other ocular dimensions in children, including anterior and vitreous chamber depths, axial length, and spherical equivalent refractive error, was investigated. METHODS: Corneal asphericity and r(o) were calculated by using corneal topography data on 643 children (72 myopes, 370 emmetropes, and 201 hyperopes), ages 6 to 15 years, who participated in the Orinda Longitudinal Study of Myopia (OLSM) during 1991. Measurements from a younger subset of these children, including 8 myopes, 92 emmetropes, and 75 hyperopes, ages 6 to 9 years in 1991, were compared to 1996 data for longitudinal analysis. RESULTS: Mean +/- SD Q of the 1991 study sample was -0.346 +/- 0.101, representing a prolate corneal shape. Almost all (99.7%) of the corneas examined were prolate. Corneal asphericity was less prolate among myopes than in emmetropes and hyperopes (P = 0.010). Less prolate corneas were related to deeper anterior chamber depths among emmetropes (r = 0.324, P < 0.0001) and hyperopes (r = 0.275, P < 0.0001), but not among myopes (r = 0.230, P = 0.0515). Flatter values of r(o) were related to longer vitreous chamber depth (r = 0.607, P < 0.0001) and axial length (r = 0.606, P < 0.0001) in all refractive error groups. Initial corneal shape was unrelated to change in refractive error over a 5-year period. CONCLUSIONS: Most corneas examined in this study were prolate in contour. Deeper anterior chamber depths were related to less prolate corneas among emmetropes and hyperopes, which is probably the result of mechanical influences on the peripheral cornea as the anterior chamber elongates during ocular growth. Longitudinal results suggest initial corneal shape is of little or no value in predicting refractive error progression.

Adolescent↗

PubMed2005

Comparison of ocular component growth curves among refractive error groups in children.

PURPOSE: To compare ocular component growth curves among four refractive error groups in children. methods Cycloplegic refractive error was categorized into four groups: persistent emmetropia between -0.25 and +1.00 D (exclusive) in both the vertical and horizontal meridians on all study visits (n = 194); myopia of at least -0.75 D in both meridians on at least one visit (n = 247); persistent hyperopia of at least +1.00 D in both meridians on all visits (n = 43); and emmetropizing hyperopia of at least +1.00 D in both meridians on at least the first but not at all visits (n = 253). Subjects were seen for three visits or more between the ages of 6 and 14 years. Growth curves were modeled for the persistent emmetropes to describe the relation between age and the ocular components and were applied to the other three refractive error groups to determine significant differences. results At baseline, eyes of myopes and persistent emmetropes differed in vitreous chamber depth, anterior chamber depth, axial length, and corneal power and produced growth curves that showed differences in the same ocular components. Persistent hyperopes were significantly different from persistent emmetropes in most components at baseline, whereas growth curve shapes were not significantly different, with the exception of anterior chamber depth (slower growth in persistent hyperopes compared with emmetropes) and axial length (lesser annual growth per year in persistent hyperopes compared with emmetropes). The growth curve shape for corneal power was different between the emmetropizing hyperopes and persistent emmetropes (increasing corneal power compared with decreasing power in emmetropes). conclusions Comparisons of growth curves between persistent emmetropes and three other refractive error groups showed that there are many similarities in the growth patterns for both the emmetropizing and persistent hyperopes, whereas the differences in growth lie mainly between the emmetropes and myopes.

Adolescent↗

PubMed2005

Axial growth and changes in lenticular and corneal power during emmetropization in infants.

PURPOSE: To evaluate the contribution made by the ocular components to the emmetropization of spherical equivalent refractive error in human infants between 3 and 9 months of age. METHODS: Keratophakometry in two meridians was performed on 222 normal-birthweight infant subjects at 3 and 9 months of age. The spherical equivalent refractive error was measured by cycloplegic retinoscopy (cyclopentolate 1%). Anterior chamber depth, lens thickness, and vitreous chamber depth were measured by A-scan ultrasonography over the closed eyelid. RESULTS: Both the mean and SD for spherical equivalent refractive error decreased between 3 and 9 months of age (+2.16 +/- 1.30 D at 3 months; +1.36 +/- 1.06 D at 9 months; P < 0.0001, for the change in both mean and SD). Average ocular component change was characterized by increases in axial length, thinning, and flattening of the crystalline lens, increases in lens equivalent refractive index, and decreases in lens and corneal power. Initial refractive error was associated in a nonlinear manner with the change in refractive error (R(2) = 0.41; P < 0.0001) and with axial growth (R(2) = 0.082; P = 0.0005). Reduction in hyperopia correlated significantly with increases in axial length (R(2) = 0.16; P < 0.0001), but not with changes in corneal and lenticular power. Decreases in lenticular and corneal power were associated with axial elongation (R(2) = 0.40, R(2) = 0.12, respectively; both P < 0.0001). CONCLUSIONS: Modulation in the amount of axial growth in relation to initial refractive error appeared to be the most influential factor in emmetropization of spherical equivalent refractive error. The associations between initial refractive error, subsequent axial growth, and change in refractive error were consistent with a visual basis for emmetropization. The cornea and crystalline lens lost substantial amounts of dioptric power in this phase of growth, but neither appeared to play a significant role in emmetropization.

Accommodation, Ocular↗

PubMed2005

Self-reported dry eye disease across refractive modalities.

PURPOSE: To compare self-reported dry eye disease across contact lens wearers, spectacles wearers, and clinical emmetropes (i.e., those not requiring refractive correction). METHODS: The survey included two symptom questions (dryness and light sensitivity) that inquired about frequency and intensity at three times of day (morning, afternoon, and evening) and a self-perception question (i.e., Do you think you have dry eyes?). Dryness and light sensitivity scales were then calculated, summed, and scored, providing a dry eye classification. Logistic regression (binary and multinomial) and analysis of covariance were used to examine the relation between mode of refractive correction and dry eye status, frequency of symptoms, and diurnal change in symptom intensity. RESULTS: Overall, 893 surveys were completed, and the age-adjusted frequency of dry eye in the sample was 28.7%, with 3.5% of the sample reporting severe symptoms (at least grade 4 of a possible 5 for both symptoms). Contact lens wearers were most likely to report dry eye disease (52.3%), followed by spectacle wearers (23.9%) and clinical emmetropes (7.1%). Adjustment for age and gender showed that contact lens (adjusted odds ratio = 12.37, 95% confidence interval = 7.55-20.26) and spectacle wearers (adjusted odds ratio = 2.06, 95% confidence interval = 1.12-3.80) were more likely than emmetropes to report dry eye problems. After adjustment for age and gender, contact lens wearers were shown to be more likely to experience frequent symptoms and an increase in symptoms throughout the day (F = 51.4, P < 0.0001). CONCLUSIONS: The frequency of self-reported dry eye is high, especially in contact lens wearers.

Adolescent↗

PubMed2005

Thinning rate of the precorneal and prelens tear films.

PURPOSE: To apply interferometry as an in vivo measure of tear film thinning between blinks. METHODS: Wavelength-dependent interference was used to measure the tear film thinning rates in 20 normal contact lens wearers, and spectra were captured at a rate of 4.5 per second for 20 seconds. Four recordings of precorneal tear film (PCTF) thinning were made, followed by 1 hour of hydrogel lens wear and then four recordings of prelens tear film (PLTF) thinning. Subjects were asked to blink 1 second after the beginning of the recording and then hold their eyes open for an additional 19 seconds, followed by 2 minutes of rest between recordings. RESULTS: The average thinning rate of the PLTF was greater than that of the PCTF and average initial tear film thickness of the PLTF was less than that of the PCTF. For both these reasons, the "tear thinning time" (time to reach 0 thickness) was typically shorter for the PLTF than for the PCTF. Histograms of PCTF and PLTF thinning rates showed a narrow peak corresponding to slow thinning of approximately 1 microm/min, but also many examples of rapid thinning of approximately 10 microm/min, with greater variability. Both the initial thickness and thinning rate of the PLTF correlated with corresponding values for the PCTF, although many more rapidly changing values were associated with the PLTF. Plots of rapid thinning of PCTF and PLTF were both linear and were not accompanied by any significant increase in thickness of corneal epithelium or contact lens, respectively. CONCLUSIONS: Tear film thinning can be analyzed in terms of flow in three spatial directions: (1) outward (evaporation), (2) inward (into the epithelium or contact lens), and (3) parallel to the tear film surface. The results indicate that the second mechanism may be unimportant. Studies have shown a range of tear film evaporation rates from 0.24 to 1.45 microm/min, whereas, when the lipid layer is washed away from the tear film, the thinning rate, due to evaporation, would be approximately 7 microm/min. Thus, slow thinning rates may be due to tear film evaporation, whereas rapid rates (which are often greater than 7 microm/min) presumably include other mechanisms such as dewetting, Marangoni flow (i.e., surface tension gradients), and pressure-gradient flow.

Adult↗

PubMed2004

Reasons patients recommend laser in situ keratomileusis.

PURPOSE: To evaluate the reasons patients who have had laser in situ keratomileusis (LASIK) recommend it to others and examine the disparity between high levels of satisfaction and patient reports of night-vision symptoms and/or dry eye after LASIK. SETTING: Northeastern Eye Institute, Scranton, and the University of Pittsburgh, Pittsburgh, Pennsylvania, and the University of California at Los Angeles, Los Angeles, California, USA. METHODS: Questionnaires assessing symptoms and satisfaction after LASIK were mailed to 2,100 patients. The questionnaires included items about night-vision symptoms and satisfaction and an open-ended question for patients to give their reasons for recommending LASIK to others. The open-ended responses were categorized and tabulated. RESULTS: Four hundred thirty-four patients provided reasons for recommending LASIK to others. Sixteen categories of reasons were identified. "No more spectacles/contact lenses" was listed by 180 patients (42%), followed by "better vision" (21%) and "convenience" (15%). Women were significantly more likely to cite "better comfort" (27 women versus 3 men; chi square = 8.99, P =.003) and "better quality of life" (41 women versus 9 men; chi square = 7.36, P =.007) as a reason for recommending LASIK. Of the 35 patients who reported dissatisfaction with post-LASIK vision, 20 (57%) would recommend LASIK to a friend because "LASIK helps others." CONCLUSIONS: Categories of reasons for recommending LASIK to others were similar to reasons given by patients for seeking LASIK. Some patients who reported dissatisfaction with their vision said they would recommend LASIK, suggesting that recommendation of LASIK to others is not necessarily a measurement of the quality of a patient's vision after LASIK.

Adult↗

PubMed2004

The repeatability of clinical measurements of dry eye.

PURPOSE: The repeatability of individual dry eye diagnostic tests has been reported in the literature on normal samples of patients and to a lesser degree in dry eye patients. In this study, the repeatability of a battery of clinical diagnostic tests for dry eye was assessed on mild to moderate dry eye patients. METHODS: A dry eye examination was performed on 75 patients on two occasions by a single examiner. The battery of dry eye tests included symptom assessment, contact lens and medical history, slit-lamp biomicroscopic evaluation of the eyelids, evaluation of Meibomian glands, assessment of tear film quality, tear meniscus height, assessment of blink quality, fluorescein tear breakup time (TBUT), fluorescein and rose bengal staining of the cornea and conjunctiva, phenol red thread test, and Schirmer test. RESULTS: The repeatability of subjective report of dryness (kappaW = 0.62) and grittiness (kappaW = 0.73) was moderate to high. In contrast, the repeatability of Meibomian gland disease classification (kappaW = 0.20), presence or absence of inferior corneal fluorescein staining (kappa = 0.25), and inferior conjunctival rose bengal staining (kappa = 0.21) was poor. When a summed staining score of corneal and conjunctival regions was evaluated, weighted kappa reliability was fair. The repeatability of tear breakup time was substantial [95% limits of agreement -5.71 to 5.83 seconds; intraclass coefficient coefficient (ICC) 0.65], and improved when the two timed readings were averaged. Repeatability of the Schirmer test is more variable as wetting scores increase. When the average Schirmer scores </= 10 mm were evaluated, moderate repeatability was demonstrated, indicating that the test performs better with more advanced disease. CONCLUSION: Although patient-reported symptoms are moderately repeatable from visit to visit, many of the procedures clinically used to diagnose and monitor dry eye syndromes are largely unrepeatable.

Adult↗

PubMed2004

The reliability and validity of McMonnies Dry Eye Index.

OBJECTIVE: The purpose of this report was to investigate the psychometric properties of the McMonnies questionnaire for dry eye disease. METHODS: The instrument was administered to 75 patients with dry eye disease on two occasions. Additional dry eye clinical tests, patient-reported dry eye interviews, and the NEI-VFQ-25 were completed during these examinations. Reliability (internal consistency and test-retest), validity (concurrent and discriminant), and accuracy were assessed for McMonnies Index scores. RESULTS: McMonnies Index showed poor internal consistency (Cronbach alpha = 0.43) and moderate test-retest reliability (ICC = 0.86, 95% confidence interval 0.76 to 0.90). The mean difference between visits was 0.49 (1-sample t test, t = 0.92, P = 0.36), and the 95% limits of agreement for test-retest reliability were -8.6 to +9.6. The instrument also showed fair concurrent validity, correlating only with the NEI-VFQ-25 pain subscale, but better discriminant validity when comparing mild and severe patients. Finally, the McMonnies Index demonstrated fair accuracy in identifying severe dry eye patients as defined by signs and symptoms (area under the ROC curve = 0.65). CONCLUSIONS: The McMonnies Index demonstrates fair reliably and validity as a patient-reported instrument for use in patient care and clinical studies of patients with dry eye disease.

Adult↗

PubMed2004

Use of the experience sampling method to measure nearwork.

PURPOSE: The purpose of this study was to use the Experience Sampling Method (ESM) to evaluate the daily visual activities of a group of optometry students and to determine whether the ESM could detect differences in visual activities when a difference was thought to exist. METHODS: Sixty-two optometry students, at four different levels of training, at The Ohio State University College of Optometry were tested using the ESM during a 14-day period. A subgroup of 18 subjects in their fourth year of study was asked to repeat the 14-day ESM on a second occasion. The two ESM periods were specifically chosen at times when the subjects were expected to have markedly different nearwork profiles. RESULTS: A comparison of members from the four optometry classes when the fourth-year students were taking final written examinations showed no significant differences in the proportion of nearwork among groups (p = 0.170); however, when the fourth-year students were primarily performing eye examinations during clinical rotations, there was a significant difference in the proportion of nearwork among training levels (13.8% for fourth-year students compared with 24.9%, 23.7%, and 30.4% for the other optometry classes; p = 0.0001). The percentage of time spent doing nearwork and performing eye examinations was significantly different between two ESM periods (paired t-test, p = 0.0001 for each activity). CONCLUSIONS: The ESM is capable of detecting differences in the proportion of time spent doing nearwork and performing eye examinations among groups of optometry students in different levels of training with different daily visual demands and between two ESM periods when these activities were expected to differ. The ESM can be used as an alternative method for nearwork quantification in future studies.

Adult↗

PubMed2004

Refractive astigmatism and the toricity of ocular components in human infants.

PURPOSE: Many studies have characterized astigmatism in infancy, but few have been longitudinal or contained ocular component data. This study characterized the frequency, orientation, and longitudinal change with age of infant astigmatism. Additional factors investigated were the influence of early astigmatism on emmetropization and its relation to corneal and lenticular toricity. METHODS: Three hundred two infants were enrolled in the study. Of these, 298 provided data for at least one visit at 3 +/- 1 months, 9 +/- 1 months, 18 +/- 2 months, and 36 +/- 3 months. Testing included cycloplegic retinoscopy (cyclopentolate 1%), video-based keratophakometry, and ultrasonography over the closed eyelid. RESULTS: Astigmatism > or =1.00 DC was common at 3 months of age (41.6%) but decreased in prevalence to 4.1% by 36 months (p < 0.0001). The most common orientation was with-the-rule at 3 months (37.0% compared with 2.7% for against-the-rule) but against-the-rule at 36 months (3.2% compared with 0.9% for with-the-rule). Most of the change in the average value of the horizontal/vertical component of astigmatism (J0) occurred between 3 and 9 months (-0.26 +/- 0.36 D; p < 0.0001) with no significant change between 9 and 36 months (-0.05 +/- 0.36 D; p=0.09). Spherical equivalent refractive error was not correlated with J0 at 3 and 9 months (R=0.002, p=0.48 and R=0.001, p=0.56, respectively). The two were only weakly correlated at 18 and 36 months (R=0.06 for each age, p <0.0001, p=0.0002, respectively). Changes in spherical equivalent between 3 and 9 months were unrelated to either the initial value of J0 (partial R for J0=0.0001; p=0.85) or the change in J0 (partial R for change in J0=0.0031; p=0.31). Across all the ages, corneal toricity was with-the-rule, and lenticular toricity was against-the-rule (produced by the toricity of the posterior lens surface). The cornea and anterior lens surface became more spherical with age, contributing to the shift away from with-the-rule refractive astigmatism. Toricity of all the refractive surfaces became less variable with age. CONCLUSIONS: Consistent with many reports, astigmatism was common in early infancy but decreased in prevalence with age, particularly when with-the-rule in orientation. The reduction in percentage of infants with astigmatism appeared to be caused by decreases in the toricity of the cornea and the anterior lens combined with decreases in the variability of corneal and lenticular surfaces. Astigmatism in infancy appeared to be unrelated to emmetropization of spherical equivalent refractive error.

Age Distribution↗

PubMed2004

Characteristics of corneal ectasia after LASIK for myopia.

PURPOSE: There are numerous reports of corneal ectasia after laser in situ keratomileusis (LASIK) for myopia without a consistent definition of this condition or a definitive etiology. We conducted a retrospective analysis of published case reports to describe common characteristics of this postoperative event and compared them with findings from a group of successful LASIK patients. METHODS: A MEDLINE search for "LASIK" and "ectasia" yielded 21 relevant articles published before May 2003 (n = 86 eyes, 59 patients). A comparison group (n = 103 eyes, 63 patients) was selected from a clinic-based sample of successful LASIK patients with 12 months of follow-up after treatment. Descriptive statistics are reported as median and interquartile range. Comparisons were performed using the Wilcoxon rank sum, Wilcoxon signed rank, and chi-square tests. RESULTS: Time to diagnosis of ectasia after LASIK was 13 months (6 to 20 months). Residual myopia in the ectasia group was -3.69 D (-6.00 to -2.13 D) and was significantly greater than the comparison group, -0.38 D (-0.75 to 0.00 D), P < 0.001. After surgery, eyes with ectasia had increased corneal toricity 2.87 D (2.00 to 4.9 D) with increased oblique astigmatism 1.3 D (0.23 to 2.89 D) relative to eyes in the comparison group 0.00 D (0.00 to 0.08 D), and a loss of 2 lines (-0.5 to -6 lines) of best spectacle-corrected visual acuity (all P < 0.001). Thirty-five percent of reported cases resulted in subsequent corneal transplantation. CONCLUSIONS: Preoperative characteristics of corneal ectasia include worse visual acuity, less corneal thickness, greater residual myopia, and greater corneal toricity than nonectatic eyes. Treatment factors associated with corneal ectasia after LASIK are greater stromal ablation and less residual stromal bed thickness. Postoperative characteristics of corneal ectasia are myopic refractive error with increased astigmatism, worse spectacle-corrected visual acuity, increased corneal toricity with topographic abnormality, and progressive corneal thinning.

Adult↗

PubMed2004

The lack of association between signs and symptoms in patients with dry eye disease.

BACKGROUND: The purpose of this report was to examine the relation between clinical tests and dry eye symptoms in patients with dry eye disease. METHODS: Seventy-five patients with dry eye disease (ICD-9 code 375.15) were included in these analyses. There was no specific entry criterion for enrollment in addition to a previous dry eye diagnosis in this clinic-based sample. Patients represented varying types and severity of dry eye disease and were previously diagnosed by clinic attending doctors in this university clinic setting. The study examination included a symptom interview that assessed dryness, grittiness, soreness, redness, and ocular fatigue. The interview was followed by a clinical dry eye examination conducted in the following sequence: meibomian gland assessment, tear meniscus height, tear breakup time test, fluorescein staining, the phenol red thread test, Schirmer test, and rose bengal staining. Partial Spearman correlation coefficients, the Wilcoxon rank sum test, chi 2 test, and multivariate logistic regression were used to evaluate the relationship between dry eye tests and symptoms. RESULTS: Symptoms were generally not associated with clinical signs in patients with dry eye disease. There were no significant correlations between signs and symptoms after adjustment for age and artificial tear use. The rank of each clinical test result did not statistically differ when stratified by the presence of patient symptoms in Wilcoxon rank sum analyses. Likewise, the frequency of patient symptoms did not differ statistically when stratified by a positive clinical test result in chi 2 analyses. In multivariate logistic regression analyses, no clinical test significantly predicted frequently reported symptoms after adjustment for age and artificial tear use. CONCLUSIONS: These results suggest a poor relation between dry eye tests and symptoms, which represents a quandary in dry eye clinical research and practice.

Adult↗

PubMed2004

Magnetic field coil measurements of the accuracy of extreme gaze ocular fixation.

PURPOSE: (1) To assess the adequacy of the magnetic field coil method (MFCM) for measures of extreme gaze ocular fixation; and (2) to measure the accuracy of ocular fixation for a short duration at gaze angles of 10 to 40 degrees. METHODS: Seven subjects participated. Two experiments were performed on the same day. In both experiments, the head and eye were rotated in opposite directions. In the first experiment, search coil slippage was assessed using photographs of a scleral search coil worn on one eye. These photographs were taken with a slitlamp biomicroscope equipped with a digital photography system as subjects rotated the eyes through nasal angles up to 40 degrees. In the second experiment, measures of ocular position were made using the MFCM as the eye was rotated through nasal angles up to 40 degrees to fixate a light-emitting diode target under two conditions. In one condition, subjects simply aimed the eye at the target. In the other, subjects placed a foveal afterimage on the target as the target was viewed through a pinhole. RESULTS: Temporal search coil slippage >10 arc min was noted for three subjects. For one subject, this slippage occurred at gaze angles > or =20 degrees, whereas for the other subjects, the slippage appeared at gaze angles of > or =30 degrees. Ocular fixation had to be assessed from the differences in fixation position between the two conditions in the second experiment because of search coil slippage and because the relationship between the anterior and posterior portions of the eyes changed for some individuals as the gaze angle changed. Fixation was usually accurate (within 10 arc min). There were occasional instances where fixation errors >15 arc min occurred, but we believe that all but one of these cases were attributable to poor localization of the afterimage. CONCLUSION.: Scleral search coils can slip on some individuals in extreme gaze. Search coils may also be inadequate to indicate the direction of the fovea in extreme gaze for some individuals because the relationship between the anterior and posterior portions can change with gaze angle. Once artifacts associated with the MFCM and localization of the afterimage are accounted for, ocular fixation is almost always within 10 arc min of the fixation target at gaze angles of 10 to 40 degrees.

Adult↗

PubMed2004

Normal eye growth in emmetropic schoolchildren.

PURPOSE: The purpose of this report is to describe the normal growth pattern of the optical components of the eye in a cohort of emmetropic, school-aged children. METHODS: Emmetropia was defined as refractive error (measured by cycloplegic autorefraction) in the vertical and horizontal meridians of the right eye between +1.00 D and -0.25 D at all the visits. This definition resulted in a sample of 194 children enrolled in the Orinda Longitudinal Study of Myopia (OLSM) between ages 6 and 14 years with at least 2 years of follow-up evaluation (across three annual visits) between 1989 and 2000. The optical components measured included corneal power, anterior chamber depth, crystalline lens thickness, Gullstrand lens power, calculated lens power, crystalline lens index, vitreous chamber depth, and axial length. RESULTS: Corneal power and anterior chamber depth were best modeled as quadratic functions of ln (age). The model involving the square of the inverse of age best described calculated lens power and crystalline lens index. The relationship between age and crystalline lens thickness was best described using a linear function of age with a point of inflection. A linear function of ln (age) with a point of inflection best described the relationship between age and axial length, Gullstrand lens power, and vitreous chamber depth. For five of the eight components (crystalline lens thickness, Gullstrand lens power, calculated lens power, corneal power, and crystalline lens index), the line modeling the data was negative in overall direction, indicating that the component value decreased with age. The upward trend of the line modeling axial length, anterior chamber depth, and vitreous chamber depth reflected the continued growth of the eye from age 6 years to age 15 years. CONCLUSIONS: A picture of normal eye growth in emmetropes from ages 6 to 15 years is provided based on a combination of cross-sectional and longitudinal data. Axial elongation, crystalline lens flattening and thinning, and decrease in lens power are its hallmarks.

Adolescent↗

PubMed2004

Validity and reliability of the revised convergence insufficiency symptom survey in adults.

PURPOSE: To assess the validity and reliability of the revised Convergence Insufficiency Symptom Survey (CISS) in adults aged 19-30 years. The CISS was developed to be the primary outcome measure for studies evaluating various treatments for convergence insufficiency (CI). METHODS: CISS mean scores from adults with symptomatic CI and adults with normal binocular vision (NBV) were compared to assess the survey's validity. Adults with symptomatic CI were given the CISS twice to evaluate reliability, which was assessed using intraclass correlation coefficient (ICC) and 95% limits of agreement. RESULTS: Forty-six adults with CI and 46 adults with NBV participated in the study. The mean CISS score for the CI group was 37.3 (S.D. = 9.3) and 11.0 (S.D. = 8.2) for the NBV group. These mean values were significantly different (p < 0.0001). Good discrimination (sensitivity = 97.8%, specificity = 87%) was obtained using a score of 21 or higher. For the CI group the ICC was 0.885 (95% CI of 0.798, 0.936) and the 95% limits of agreement were -9.0 to 7.6. CONCLUSIONS: Adults with symptomatic CI had a significantly higher CISS score than adults with NBV. The results of the study demonstrate that the CISS is a valid and reliable instrument that can be used clinically or as an outcome measure for research studies of adults with CI.

Accommodation, Ocular↗

PubMed2004

An assessment of self-reported disease classification in epidemiological studies of dry eye.

PURPOSE: To evaluate the reliability of self-reported dry eye disease status and patient-related predictors of misclassification in contact lens wearers. METHODS: Patients completed the Contact Lens Dry Eye Questionnaire (CLDEQ) short form on two occasions. Test-retest reliability of the CLDEQ composite score was determined using the 95% limits of agreement (LoA) and an intraclass correlation coefficient (ICC). The kappa statistic was used to determine reliability of disease-classification-based CLDEQ composite score cutoff points. Predictors of misclassification were determined by multivariate logistic regression. RESULTS: The sample included 274 patients. The range of CLDEQ composite scores from both visits was -1.83 to 4.50 and the mean difference between administrations was -0.05 +/- 0.75 (P = 0.30). The 95% LoA of the CLDEQ composite score were -1.51 to 1.42 and the ICC was 0.61 (95% confidence interval [CI]: 0.53-0.68). Calculations using the lower limit of the 95% CI showed that three administrations of the survey would be required to obtain a more desirable ICC (0.70). The kappa statistic for reliability of dry eye disease classification was 0.58 (95% CI: 0.48-0.67). Logistic regression showed a significant interaction between gender (females) and younger age (P = 0.02) in relation to misclassification of self-reported dry eye disease status. CONCLUSIONS: The reliability of self-reported dry eye disease classification in contact lens wearers is moderate. In epidemiologic studies of factors associated with self-reported disease status, investigators may be well advised to consider using multiple administers of such outcome instruments and controlling for sociodemographic characteristics to maintain internal validity.

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