Predictors of hematologic malignancy relapse in patients with advanced chronic graft-versus-host disease.

Malignancy relapse remains a major barrier to treatment success in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Chronic graft-versus-host disease (cGVHD) markedly reduces hematologic malignancy relapse risk, but relapses still occur in these patients. Patients (n = 275) with moderate or severe cGVHD were enrolled on the National Cancer Institute (NCI) prospective cross-sectional natural history study (NCT00092235). Subjects were median 36 months after allo-HSCT and were followed subsequently for malignancy relapse and survival. Seventeen patients experienced relapse. In a multivariable model including time-dependent influences on relapse, risk factors associated with increased risk of relapse included shorter time from transplant to cGVHD evaluation (HR 0.279, 95% CI 0.078-0.995) and lower number of prior lines of systemic immunosuppressive therapy for cGVHD (HR 0.260, 95% CI 0.094-0.719). In a model excluding time-dependent influences on relapse risk, lower number of prior lines of systemic immunosuppressive therapy for cGVHD (HR 0.288, 95% CI 0.103-0.804), lower C4 complement level (HR 0.346, 95% CI 0.129-0.923), and higher body mass index (HR 3.222, 95% CI 1.156-8.974), were all associated with increased relapse risk. Parameters indicating cGVHD severity and activity are associated with risk of malignancy relapse. Classical predictors of relapse after allo-HSCT do not seem to be prognostic.

Impact of the 2014 NIH chronic graft-versus-host disease scoring criteria modifications assessed in a large cohort of severely affected patients.

In 2005, the National Institutes of Health (NIH) chronic graft-versus-host disease (cGVHD) consensus project provided diagnosis and staging criteria, based mostly on clinical experience and expert opinion. These criteria were revised in 2014, aiming to provide enhanced specificity and clarity. However, the impact of 2014 changes to the original NIH cGVHD severity scoring criteria has not been reported. In this study, 284 patients, prospectively enrolled on the National Cancer Institute's cross-sectional cGVHD natural history study, were scored using the 2005 NIH cGVHD criteria and then rescored according to the 2014 modifications. In comparing the two criteria, 2014 cGVHD global severity scoring resulted in a tendency toward being categorized as milder scores (75 vs. 72% of severe score per 2014, p = 0.0009), with a statistically significant shift in NIH liver and lung scores toward milder categories (p < 0.0001). 2005 and 2014 NIH global severity scores showed a significant association with reduced grip strength (p < 0.0001), reduced joint range of motion (p = 0.0003), and the subspecialist evaluation score (p < 0.0001). Poor survival prediction of the severe NIH lung score is also retained in the new criteria (p = 0.0012). These findings support the use of 2014 cGVHD scoring criteria in continuous efforts to develop better classification systems.

Complicated spastic paraplegia in patients with AP5Z1 mutations (SPG48).

OBJECTIVE: Biallelic mutations in the AP5Z1 gene encoding the AP-5 ζ subunit have been described in a small number of patients with hereditary spastic paraplegia (HSP) (SPG48); we sought to define genotype-phenotype correlations in patients with homozygous or compound heterozygous sequence variants predicted to be deleterious. METHODS: We performed clinical, radiologic, and pathologic studies in 6 patients with biallelic mutations in AP5Z1. RESULTS: In 4 of the 6 patients, there was complete loss of AP-5 ζ protein. Clinical features encompassed not only prominent spastic paraparesis but also sensory and motor neuropathy, ataxia, dystonia, myoclonus, and parkinsonism. Skin fibroblasts from affected patients tested positive for periodic acid Schiff and autofluorescent storage material, while electron microscopic analysis demonstrated lamellar storage material consistent with abnormal storage of lysosomal material. CONCLUSIONS: Our findings expand the spectrum of AP5Z1-associated neurodegenerative disorders and point to clinical and pathophysiologic overlap between autosomal recessive forms of HSP and lysosomal storage disorders.

Longitudinal Study of Age-Related Cataract Using Dynamic Light Scattering: Loss of α-Crystallin Leads to Nuclear Cataract Development.

PURPOSE: To conduct a longitudinal study on age-related nuclear cataracts using dynamic light scattering (DLS) to determine if cataract progression is associated with loss of the unbound form of the lens molecular chaperone protein, α-crystallin. DESIGN: Natural history and cohort study. PARTICIPANTS: Patients 30 years of age or older of either gender seeking treatment at the Wilmer Eye Institute Cornea-Cataract Department. METHODS: All patients underwent a comprehensive dilated eye examination every 6 months, including slit-lamp grading of their lenses using the Age-Related Eye Disease Study (AREDS) clinical lens grading system and obtaining an estimate of unbound α-crystallin level in the nucleus, the α-crystallin index (ACI), using the National Aeronautics and Space Administration-National Eye Institute DLS device. We used a random effects statistical model to examine the relationship of lens opacity changes over time with ACI changes. MAIN OUTCOME MEASURES: α-Crystallin Index (ACI) and AREDS nuclear cataract grade. RESULTS: Forty-five patients (66 eyes) 34 to 79 years of age with AREDS nuclear lens grades of 0 to 3.0 were followed up every 6 months for a mean of 19 months (range, 6-36 months). We found that lenses with the lowest baseline levels of ACI had the most rapid progression of cataracts, whereas lenses with higher ACI at baseline had no or slower cataract progression. Lenses that lost α-crystallin at the highest rates during the study also had faster progression of nuclear cataracts than lenses with a slower rate of ACI loss. Kaplan-Meier survival curves showed that lenses with the lowest initial ACI had the highest risk of undergoing cataract surgery. CONCLUSIONS: This longitudinal study corroborates our previous cross-sectional study finding that higher levels of unbound α-crystallin as assessed by ACI are associated with lower risk of cataract formation and that loss of ACI over time is associated with cataract formation and progression. This study suggested that assessment of ACI with the DLS device could be used as a surrogate for lens opacity risk in clinical studies, and for assessing nuclear cataract events in studies where cataract development may be a side effect of a drug or device.

Predictive models for ocular chronic graft-versus-host disease diagnosis and disease activity in transplant clinical practice.

Ocular chronic graft-versus-host disease is one of the most bothersome common complications following allogeneic hematopoietic stem cell transplantation. The National Institutes of Health Chronic Graft-versus-Host Disease Consensus Project provided expert recommendations for diagnosis and organ severity scoring. However, ocular chronic graft-versus-host disease can be diagnosed only after examination by an ophthalmologist. There are no currently accepted definitions of ocular chronic graft-versus-host disease activity. The goal of this study was to identify predictive models of diagnosis and activity for use in clinical transplant practice. A total of 210 patients with moderate or severe chronic graft-versus-host disease were enrolled in a prospective, cross-sectional, observational study (clinicaltrials.gov identifier: 00092235). Experienced ophthalmologists determined presence of ocular chronic graft-versus-host disease, diagnosis and activity. Measures gathered by the transplant clinician included Schirmer's tear test and National Institutes of Health 0-3 Eye Score. Patient-reported outcome measures were the ocular subscale of the Lee Chronic Graft-versus-Host Disease Symptom Scale and Chief Eye Symptom Intensity Score. Altogether, 157 (75%) patients were diagnosed with ocular chronic graft-versus-host disease; 133 of 157 patients (85%) had active disease. In a multivariable model, the National Institutes of Health Eye Score (P<0.0001) and Schirmer's tear test (P<0.0001) were independent predictors of ocular chronic graft-versus-host disease (sensitivity 93.0%, specificity 92.2%). The Lee ocular subscale was the strongest predictor of active ocular chronic graft-versus-host disease (P<0.0001) (sensitivity 68.5%, specificity 82.6%). Ophthalmology specialist measures that were most strongly predictive of diagnosis in a multivariate model were Oxford grand total staining (P<0.0001) and meibomian score (P=0.027). These results support the use of selected transplant clinician- and patient-reported outcome measures for ocular chronic graft-versus-host disease screening when providing care to allogeneic hematopoietic stem cell transplantation survivors with moderate to severe chronic graft-versus-host disease. Prospective studies are needed to determine if the Lee ocular subscale demonstrates adequate responsiveness as a disease activity outcome measure.

Biomarker-driven phase 2 study of MK-2206 and selumetinib (AZD6244, ARRY-142886) in patients with colorectal cancer.

PURPOSE: PI3K/AKT/mTOR and RAS/RAF/MEK pathways are frequently dysregulated in colorectal cancer (CRC). We conducted a biomarker-driven trial of the combination of MK-2206, an allosteric AKT 1/2/3 inhibitor, and selumetinib, a MEK 1/2 inhibitor, in patients with CRC to evaluate inhibition of phosphorylated ERK (pERK) and AKT (pAKT) in paired tumor biopsies. PATIENTS AND METHODS: Adult patients with advanced CRC were enrolled in successive cohorts stratified by KRAS mutation status. Initially, 12 patients received oral MK-2206 90 mg weekly with oral selumetinib 75 mg daily in 28-day cycles. Following an interim analysis, the doses of MK-2206 and selumetinib were increased to 135 mg weekly and 100 mg daily, respectively. Paired tumor biopsies were evaluated for target modulation. RESULTS: Common toxicities were gastrointestinal, hepatic, dermatologic, and hematologic. Of 21 patients enrolled, there were no objective responses. Target modulation did not achieve the pre-specified criteria of dual 70 % inhibition of pERK and pAKT levels in paired tumor biopsies. CONCLUSION: Despite strong scientific rationale and preclinical data, clinical activity was not observed. The desired level of target inhibition was not achieved. Overlapping toxicities limited the ability to dose escalate to achieve exposures likely needed for clinical activity, highlighting the challenges in developing optimal combinations of targeted agents.

National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease: I. The 2014 Diagnosis and Staging Working Group report.

The 2005 National Institutes of Health (NIH) Consensus Conference proposed new criteria for diagnosing and scoring the severity of chronic graft-versus-host disease (GVHD). The 2014 NIH consensus maintains the framework of the prior consensus with further refinement based on new evidence. Revisions have been made to address areas of controversy or confusion, such as the overlap chronic GVHD subcategory and the distinction between active disease and past tissue damage. Diagnostic criteria for involvement of mouth, eyes, genitalia, and lungs have been revised. Categories of chronic GVHD should be defined in ways that indicate prognosis, guide treatment, and define eligibility for clinical trials. Revisions have been made to focus attention on the causes of organ-specific abnormalities. Attribution of organ-specific abnormalities to chronic GVHD has been addressed. This paradigm shift provides greater specificity and more accurately measures the global burden of disease attributed to GVHD, and it will facilitate biomarker association studies.

Web-based versus paper administration of common ophthalmic questionnaires: comparison of subscale scores.

OBJECTIVE: To compare participants' responses to Web-based and paper-and-pencil versions of an ophthalmic, patient-reported outcome (PRO) questionnaire. DESIGN: Questionnaire development. PARTICIPANTS: Matched subjects with ocular surface disease (OSD) (n = 68) and without OSD (controls, n = 50). METHODS: Subjects completed a standard, paper-and-pencil and a Web-based version of the same questionnaire in randomized order. The administered questionnaire included several ophthalmic PRO subscales: the National Eye Institute's (NEI's) Refractive Error Quality of Life Instrument's Clarity of Vision, Near Vision, Far Vision, Glare, Symptoms, Worry, and Satisfaction with Correction subscales; the Ocular Surface Disease Index's (OSDI's) Symptoms subscale; and the NEI's Visual Function Questionnaire's Driving subscale. Possible scores for each subscale ranged from 0 (no difficulty) to 100 (most difficulty). Agreement of subscale scores between modes of administration was assessed using the Bland-Altman approach and multivariable logistic regression. MAIN OUTCOME MEASURES: Subscale scores and an unweighted average total score for each mode of administration. RESULTS: Mean differences in scores between modes of administration ranged from -2.1 to +2.3 units. Although no differences were found to be statistically significant, the Worry and Satisfaction with Correction subscales approached statistical significance (P = 0.07 and 0.08, respectively). Although most subscale mean differences in score did not differ significantly by gender, age (≥40 vs. <40 years), disease status (OSD vs. control), order of administration, or time between completion of the questionnaires, women had slightly greater score differences than men for the Driving (P = 0.04) and Clarity of Vision (P = 0.03) subscales; those with OSD had greater score differences for Clarity of Vision than did controls (P = 0.0006); and those aged ≥40 years had slightly greater differences in OSDI Symptoms subscale than those aged <40 years (P = 0.04). CONCLUSIONS: To our knowledge, this Food and Drug Administration and NEI collaboration is the first study to evaluate the equivalence of Web-based and paper versions of ophthalmic PRO questionnaires. We found no evidence of clinically significant differences between scores obtained by the 2 modes for any of the examined subscales. A Web-based instrument should yield scores equivalent to those obtained by standard methods, providing a useful tool that may facilitate ophthalmic innovation. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

National Institutes of Health chronic graft-versus-host disease staging in severely affected patients: organ and global scoring correlate with established indicators of disease severity and prognosis.

Between 2004 and 2010, 189 adult patients were enrolled on the National Cancer Institute's cross-sectional chronic graft-versus-host disease (cGVHD) natural history study. Patients were evaluated by multiple disease scales and outcome measures, including the 2005 National Institutes of Health (NIH) Consensus Project cGVHD severity scores. The purpose of this study was to assess the validity of the NIH scoring variables as determinants of disease severity in severely affected patients in efforts to standardize clinician evaluation and staging of cGVHD. Out of 189 patients enrolled, 125 met the criteria for severe cGVHD on the NIH global score, 62 of whom had moderate disease, with a median of 4 (range, 1-8) involved organs. Clinician-assigned average NIH organ score and the corresponding organ scores assigned by subspecialists were highly correlated (r = 0.64). NIH global severity scores showed significant associations with nearly all functional and quality of life outcome measures, including the Lee Symptom Scale, Short Form-36 Physical Component Scale, 2-minute walk, grip strength, range of motion, and Human Activity Profile. Joint/fascia, skin, and lung involvement affected function and quality of life most significantly and showed the greatest correlation with outcome measures. The final Cox model with factors jointly predictive for survival included the time from cGVHD diagnosis (>49 versus ≤49 months, hazard ratio [HR] = 0.23; P = .0011), absolute eosinophil count at the time of NIH evaluation (0-0.5 versus >0.5 cells/µL, HR = 3.95; P = .0006), and NIH lung score (3 versus 0-2, HR = 11.02; P < .0001). These results demonstrate that NIH organs and global severity scores are reliable measures of cGVHD disease burden. The strong association with subspecialist evaluation suggests that NIH organ and global severity scores are appropriate for clinical and research assessments, and may serve as a surrogate for more complex subspecialist examinations. In this population of severely affected patients, NIH lung score is the strongest predictor of poor overall survival, both alone and after adjustment for other important factors.

Diagnosis and treatment of ocular chronic graft-versus-host disease: report from the German-Austrian-Swiss Consensus Conference on Clinical Practice in chronic GVHD.

PURPOSE: Ocular chronic graft-versus-host disease (cGVHD) is one of the most frequent long-term complications after hematopoietic stem cell transplantation and is often associated with significant morbidity and reduced quality of life. METHODS: The German/Austrian/Swiss Consensus Conference on Clinical Practice in cGVHD aimed to summarize the currently available evidence for diagnosis and (topical) treatment and to summarize different treatment modalities of ocular cGVHD. The presented consensus was based on a review of published evidence and a survey on the current clinical practice including transplant centers from Germany, Austria, and Switzerland. RESULTS: Ocular cGVHD often affects the lacrimal glands, the conjunctiva, the lids (including meibomian glands), and the cornea but can also involve other parts of the eye such as the sclera. Up to now, there have been no pathognomonic diagnostic features identified. The main therapeutic aim in the management of ocular cGVHD is the treatment of inflammation and dryness to relieve patients' symptoms and to maintain ocular integrity and function. Therapy should be chosen in the context of the patient's overall condition, systemic immunosuppressive therapy, symptoms, ocular surface integrity, and inflammatory activity. The consensus conference proposed new grading criteria and diagnostic recommendations for general monitoring of patients with graft-versus-host-disease for use in clinical practice. CONCLUSION: The evidence levels for diagnosis and treatment of ocular cGVHD are low, and most of the treatment options are based on empirical knowledge. Topical immunosuppression, for example, with cyclosporine, represents a promising strategy to reduce inflammation and dryness in ocular cGVHD. Further clinical trials are necessary to elucidate risk factors for eye manifestation, complications, and visual loss and to evaluate staging criteria and diagnostic and therapeutic measures for ocular cGVHD.

Sclerotic-type chronic GVHD of the skin: clinical risk factors, laboratory markers, and burden of disease.

Chronic GVHD is one of the most severe complications of allogeneic HSCT. The sclerotic skin manifestations of cGVHD (ScGVHD) result from inflammation and fibrosis of the dermis, subcutaneous tissue, or fascia, leading to significant functional disability. Risk factors and clinical markers associated with ScGVHD remain largely unexamined. By using a single-visit, cross-sectional design, we evaluated 206 patients with cGVHD at the National Institutes of Health. Most patients manifested severe (ie, 63% National Institutes of Health score "severe"), refractory disease (median treatments = 4). ScGVHD was detected in 109 (52.9%) patients. ScGVHD was associated with greater platelet count (P < .001) and C3 (P < .001), and decreased forced vital capacity (P = .013). Total body irradiation (TBI) was associated with development of ScGVHD (P = .002). TBI administered in reduced-intensity conditioning was most strongly associated with ScGVHD (14/15 patients, P < .0001). Patients with ScGVHD had significant impairments of joint range of motion and grip strength (P < .001). Greater body surface area involvement was associated with poorer survival (P = .015). We conclude that TBI, particularly in reduced-intensity regimens, may be an important risk factor for ScGVHD. Widespread skin involvement is associated with significant functional impairment, distressing symptoms, and diminished survival. This trial is registered at http://www.clinicaltrials.gov as NCT00331968.

Evaluation of the age-related eye disease study clinical lens grading system AREDS report No. 31.

PURPOSE: To examine the grading (interrater) reliability of the Age-Related Eye Disease Study (AREDS) Clinical Lens Grading System (ARLNS). DESIGN: Evaluation of diagnostic test or technology. PARTICIPANTS: One hundred fifty volunteers (284 eyes). METHODS: Participants with lens opacities of varying severity were independently graded at the slit lamp for cataract severity by 2 examiners (retinal or anterior segment specialists) using the ARLNS, which employs 3 standard photographs of increasing severity for classifying each of the 3 major types of opacity. Lens photographs were taken and graded at a reading center using the more detailed AREDS System for Classifying Cataracts from photographs. MAIN OUTCOME MEASURES: The Pearson correlation, weighted-kappa, and limits-of-agreement statistics were used to assess the interrater agreement of the gradings. RESULTS: Examinations were performed on 284 lenses (150 participants). Tests of interrater reliability between pairs of clinicians showed substantial agreement between clinicians for cortical and posterior subcapsular opacities and moderate agreement for nuclear opacities. A similar pattern and strength of agreement was present when comparing scores of retinal versus anterior segment specialists. Interrater agreement between clinical and reading center gradings was not as great as inter-clinician agreement. CONCLUSIONS: Interrater agreements were in the moderate to substantial range for the clinical assessment of lens opacities. Inherent differences in cataract classification systems that rely on slit lamp vs photographic assessments of lens opacities may explain some of the disagreement noted between slit lamp and photographic gradings. Given the interrater reliability statistics for clinicians and the simplicity of the grading procedure, ARLNS is presented for use in studies requiring a simple, inexpensive method for detecting the presence and severity of the major types of lens opacities. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Salivary gland involvement in chronic graft-versus-host disease: prevalence, clinical significance, and recommendations for evaluation.

Although xerostomia is a commonly reported complaint in patients with chronic graft-versus-host disease (cGVHD), criteria for evaluating the prevalence and characteristics of salivary gland involvement have not been well defined in this patient population. Previous studies also have made no distinction between salivary and mucosal oral cGVHD. We systematically evaluated signs and symptoms of sicca in a large cohort of patients with cGVHD (n = 101) using instruments widely used to study Sjogren's syndrome. Xerostomia was reported in 60 (77%) patients reporting ocular and 52 (67%) patients reporting oral complaints [corrected]. The salivary flow rate was < or =0.2 mL/min in 27%, and < or =0.1 mL/min in 16%. Histopathological changes, consisting of mononuclear infiltration and/or fibrosis/atrophy, were present in all patients with salivary dysfunction. Importantly, there was no correlation of salivary and oral mucosal involvement in cGVHD. Patients with cGVHD-associated salivary gland involvement had diminished oral cavity-specific quality of life and lower body mass index. Salivary gland involvement is a common and clinically distinct manifestation of cGVHD. Formal evaluation of salivary function using standardized criteria is needed, and this could be incorporated as an outcome measure in clinical trials of cGVHD.

Clinical detection of precataractous lens protein changes using dynamic light scattering.

OBJECTIVE: To use dynamic light scattering to clinically assess early precataractous lens protein changes. METHODS: We performed a cross-sectional study in 380 eyes of 235 patients aged 7 to 86 years with Age-Related Eye Disease Study clinical nuclear lens opacity grades 0 to 3.8. A dynamic light-scattering device was used to assess alpha-crystallin, a molecular chaperone protein shown to bind other damaged lens proteins, preventing their aggregation. The outcome measure was the alpha-crystallin index, a measure of unbound alpha-crystallin in each lens. The association of the alpha-crystallin index with increasing nuclear opacity and aging was determined. RESULTS: There was a significant decrease in the alpha-crystallin index associated with increasing nuclear lens opacity grades (P < .001). There were significant losses of alpha-crystallin even in clinically clear lenses associated with aging (P < .001). The standard error of measurement was 3%. CONCLUSIONS: Dynamic light scattering clinically detects alpha-crystallin protein loss even in clinically clear lenses. alpha-Crystallin index measurements may be useful in identifying patients at high risk for cataracts and as an outcome variable in clinical lens studies. CLINICAL RELEVANCE: The alpha-crystallin index may be a useful measure of the protective alpha-crystallin molecular chaperone reserve present in a lens, analogous to creatinine clearance in estimating renal function reserve.

Inhibition of the ATPase activity of the catalytic portion of ATP synthases by cationic amphiphiles.

Melittin, a cationic, amphiphilic polypeptide, has been reported to inhibit the ATPase activity of the catalytic portions of the mitochondrial (MF1) and chloroplast (CF1) ATP synthases. Gledhill and Walker [J.R. Gledhill, J.E. Walker. Inhibition sites in F1-ATPase from bovine heart mitochondria, Biochem. J. 386 (2005) 591-598.] suggested that melittin bound to the same site on MF1 as IF1, the endogenous inhibitor polypeptide. We have studied the inhibition of the ATPase activity of CF1 and of F1 from Escherichia coli (ECF1) by melittin and the cationic detergent, cetyltrimethylammonium bromide (CTAB). The Ca2+- and Mg2+-ATPase activities of CF1 deficient in its inhibitory epsilon subunit (CF1-epsilon) are sensitive to inhibition by melittin and by CTAB. The inhibition of Ca2+-ATPase activity by CTAB is irreversible. The Ca2+-ATPase activity of F1 from E. coli (ECF1) is inhibited by melittin and the detergent, but Mg2+-ATPase activity is much less sensitive to both reagents. The addition of CTAB or melittin to a solution of CF1-epsilon or ECF1 caused a large increase in the fluorescence of the hydrophobic probe, N-phenyl-1-naphthylamine, indicating that the detergent and melittin cause at least partial dissociation of the enzymes. ATP partially protects CF1-epsilon from inhibition by CTAB. We also show that ATP can cause the aggregation of melittin. This result complicates the interpretation of experiments in which ATP is shown to protect enzyme activity from inhibition by melittin. It is concluded that melittin and CTAB cause at least partial dissociation of the alpha/beta heterohexamer.

A clinical study of the human lens with a dynamic light scattering device.

A study was conducted to determine the potential usefulness and repeatability of a new dynamic light scattering (DLS) device for clinical studies of the human lens and early cataract. Studies using the cold cataract model showed this new device to be more sensitive than the Scheimpflug cataract imaging system in detecting the earliest cataractous changes. A miniaturized clinical DLS device developed by NASA using fiber optic probes was mounted on a Keratoscope (Optikon 2000), which has a 3-dimensional aiming system for accurate repeated sampling of the same area of the lens. A test/retest study was then conducted on the nuclear region of the lenses of 12 normal eyes. After a full, dilated eye examination, DLS data were obtained using the new device on the same eyes twice, 30-60 min apart. Particle size distributions and mean log particle size data were obtained. The mean percent differences between the larger and smaller of the test--retest pairs was 6.4% (range 0.05--10.8%); the between-test S.D. was 0.116. Actual numerical margin of error was +/- 0.023. In addition, the mean coefficient of variation was 4.2% (range 0.3--7.3%). A useful clinical end point obtained from data produced by the device was the mean log particle size. These results suggest that the DLS will be useful in the detection and study of the beginning and earliest stages of cataract formation in humans.