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J J Nichols

Publications and source records attributed to J J Nichols.

7 recordsLinked to original sources
PubMed2004

The relation between disease asymmetry and severity in keratoconus.

BACKGROUND/AIM: Keratoconus is described as a bilateral, asymmetric, non-inflammatory corneal ectasia. The purpose of the study was to examine the relation between disease asymmetry and severity in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study cohort. METHODS: Analyses included 1037 keratoconus patients from the CLEK Study baseline examination visit, none of whom had undergone corneal surgery in either eye. Disease asymmetry was determined by taking the difference between eyes for continuous variables. For categorical variables, asymmetry was categorised by whether the variable was present in neither, one, or both eyes. Disease severity was defined using the first definite apical clearance lens (FDACL) technique (a rigid contact lens to measure corneal curvature) from the worse (steeper) eye. Statistical analyses included Pearson's correlation coefficients (continuous variables) and analysis of variance (categorical variables). RESULTS: There were generally weak correlations between asymmetry and severity for low contrast habitual visual acuity (r = 0.12, p = 0.0003), high contrast habitual visual acuity (r = 0.14, p<0.0001), low contrast best corrected visual acuity (r = 0.21, p<0.0001), and high contrast best corrected visual acuity (r = 0.29, p<0.0001). Asymmetry in refractive error was more moderately correlated with disease severity (r = 0.41, p<0.0001), as was asymmetry in the flat (r = 0.61, p<0.0001) and steep keratometric readings (r = 0.54, p<0.0001). The average FDACL was significantly steeper in patients who had one eye with Vogt's striae, Fleischer's ring, or corneal scarring compared with the average FDACL when neither eye had these findings. CONCLUSION: Keratoconus patients with more severe disease are also more asymmetric in their disease status.

Adult↗
PubMed2001

The performance of the refractive status and vision profile survey in a contact lens clinical trial.

OBJECTIVE: To evaluate the Refractive Status and Vision Profile (RSVP) questionnaire in a contact lens clinical trial and to assess the feasibility of its use in future trials. DESIGN: Randomized, crossover clinical trial and survey. PARTICIPANTS: The RSVP was administered to 50 contact lens-wearing participants recruited from a large contact lens clinic. METHODS: RSVP scores were calculated for subjects at three outcome visits: (1) baseline, (2) after wearing daily disposable contact lenses, and (3) after wearing disposable extended wear contact lenses. One-sample t tests were used to compare baseline survey scores with those previously reported for the instrument. The relation of survey scores within and between subjects was assessed with repeated measures analysis of variance. Statistical power and sample size calculations were performed to determine the number of subjects required in future studies to detect differences in RSVP subscale scores. MAIN OUTCOME MEASURES: Eight subscale scores (concern, driving, expectations, glare, optical problems, physical and social functioning, problems with corrective lenses, and symptoms) and the overall RSVP score were calculated on the basis of guidelines reported for scoring of the instrument. RESULTS: Five of eight mean subscale scores (concern, expectations, driving, optical problems, and problems with corrective lenses) and the overall score were significantly lower than those previously reported. No differences were found in the following subscales after contact lens treatment: concern, expectations, physical and social functioning, driving, optical problems, problems with corrective lenses, or the overall RSVP score. Significant differences were found on the symptoms (P = 0.03) and glare (P = 0.05) subscales; post hoc testing revealed that the significant differences in these scores occurred between baseline and daily disposable lens wear and not between treatment modalities (daily disposable and disposable extended wear). A sample size of 420 would be required to find clinically relevant significant differences (25%) for all subscales in a similar one-sample clinical trial. A more restrictive difference (10%) would require more than 1100 subjects for four of the nine subscales. CONCLUSIONS: The RSVP questionnaire may not be the appropriate quality-of-life instrument for use in a contact lens clinical trial. The instrument seems to lack sensitivity and discriminative validity in evaluating contact lens treatments.

Adolescent↗
PubMed2000

Frequency of dry eye diagnostic test procedures used in various modes of ophthalmic practice.

PURPOSE: There are many suggested dry eye diagnostic test batteries in the literature. However, clinicians use a wide variety of dry eye diagnostic tests in clinical practice due to a number of factors, including time constraints. In addition, there has been no systematic description of the standard of care in diagnosing dry eye in the literature. The purpose of this study is to determine the type and frequency of dry eye diagnostic tests used in various modes of ophthalmic practice across a spectrum of dry eye severity. METHODS: A total of 467 patient charts (patients with a previous dry eye diagnosis) were reviewed retrospectively to determine diagnostic test frequency. In reviewing patient charts, the following tests were identified as performed or not performed: symptom assessment, fluorescein staining, tear break-up time (TBUT), Schirmer test, rose bengal staining, and "tear assessment" (including quantity and quality of the tear meniscus). RESULTS: Dry eye diagnostic tests were used in the following frequencies across all modes of practice: symptom assessment (82.8%), fluorescein staining (55.5%), TBUT (40.7%), tear assessment (22.2%), Schirmer test (8.5%), and rose bengal staining (4.9%). When the clinics are pooled, two test procedures were used with the highest frequency (38.9%). The most commonly performed two-test procedure combination was a symptom assessment combined with fluorescein staining of the cornea (43.7%). CONCLUSIONS: Symptom assessment plays a large role in the diagnosis of dry eye. The current clinical standard of care for dry eye diagnosis includes the performance of at least one test procedure in addition to a symptom assessment.

Contrast Media↗
PubMed2000

Corneal scarring and vision in keratoconus: a baseline report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study.

PURPOSE: The multicenter Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a prospective, observational study of 1,209 keratoconus patients. We report on the correlation of corneal scarring with clinical and patient-reported variables at the baseline visit. METHODS: Patients completed a questionnaire on their vision, effect of glare, contact lens wear, and work-related issues. Clinical examination included high- and low-contrast visual acuity, refraction, assessment of corneal scarring by the clinician and by photography, and measurement of corneal curvature. The correlation of central corneal scarring with visual acuity and patient-reported variables was analyzed using multiple regression analysis and generalized estimating equations. RESULTS: High- and low-contrast visual acuity with habitual and optimal correction is reduced in scarred eyes. Multiple regression analyses controlling for age, contact lens wear, and disease severity show that central scarring is associated with poorer visual acuity and increased patient-reported symptoms of glare. Restrictions on day-to-day activities do not appear to be associated with corneal scarring above and beyond the effects of keratoconus alone. CONCLUSIONS: Corneal scarring in keratoconus is significantly associated with decreased high- and low-contrast visual acuity.

Cicatrix↗
PubMed2000

Overnight orthokeratology.

PURPOSE: Orthokeratology is defined as the temporary reduction in myopia by the programmed application of rigid gas-permeable contact lenses. New reverse geometry contact lens designs and materials have led to a renewed interest in this field. The purpose of this study is to assess visual, refractive, topographic, and corneal thickness changes in subjects undergoing overnight orthokeratology. METHODS: Ten myopic subjects (mean age, 25.9+/-3.9 years) were recruited for a 60-day trial of overnight orthokeratology using reverse geometry rigid contact lenses. After commencing lens wear, subjects were examined on days 1, 7, 14, 30, and 60 at several times throughout the day. High- and low-contrast logarithm of the minimum angle of resolution (logMAR) visual acuity, monocular subjective refraction, autorefraction, autokeratometry, corneal topography, corneal thickness, and slit lamp examinations were performed at each session. RESULTS: Eight subjects completed the study. Both high- and low-contrast uncorrected visual acuity improved significantly by day 7. The mean change in uncorrected high contrast visual acuity at day 60 was -0.55+/-0.20 logMAR (mean at day 60, -0.03+/-0.16; Snellen equivalent, 20/19). The mean change in uncorrected low-contrast visual acuity at day 60 was -0.48+/-0.26 logMAR (mean at day 60, +0.22+/-0.23; Snellen equivalent, 20/33). The mean subjective refraction and autorefraction were significantly reduced from baseline at day 60 (mean change in subjective refraction, +1.83+/-1.23 D; mean change in autorefraction, +0.64+/-0.52 D). Corneal topography showed significant central flattening (mean change in apical radius, +0.20+/-0.9 mm; mean change in shape factor, -0.11+/-0.18 at day 60). The central cornea also showed significant thinning (mean change, -12+/-11 microm at day 60). All visual, refractive, and topographic outcomes were sustained over the course of an 8-h day. CONCLUSIONS: Overnight orthokeratology is an effective means of temporarily reducing myopia. The possible mechanism of corneal remodeling through central corneal thinning is discussed.

Adult↗
PubMed2000

Daily disposable vs. disposable extended wear: a contact lens clinical trial.

BACKGROUND: The purpose of this work was to compare traditional standards of contact lens success and patient-reported preferences in the daily-disposable and disposable extended-wear contact lens modalities. METHODS: This study was a randomized, cross-over contact lens clinical trial involving 50 patients. After the baseline examination, two outcome examinations were performed including the self-administration of the Refractive Status and Vision Profile (RSVP) survey, an additional survey, and masked visual acuity and slit-lamp assessments. RESULTS: No differences were noted on the RSVP when comparing treatment modalities. Patients were considered equally successful in terms of wearing time, overall comfort, visual acuity, and ocular health criteria. In terms of patient preferences, a significant number of patients preferred the disposable extended-wear modality over the daily-disposable modality (chi2(1) = 4.08, p = 0.04). Patients preferred disposable extended-wear over daily-disposables due to convenience (odds ratio = 30.33). CONCLUSIONS: Disposable extended-wear represents a convenient contact lens option for contact lens patients.

Adolescent↗