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Assessment of Visual Performance in Patients With Low Levels of Astigmatism

This study has been completed.
Information provided by:
Alcon Research Identifier:
First received: February 11, 2009
Last updated: September 23, 2010
Last verified: September 2010
To assess visual performance in patients with low levels (0.5-0.75 Diopters) of corneal astigmatism.

Condition Intervention
Cataract Extraction
Corneal Astigmatism
Other: Visual performance measures

Study Type: Observational
Study Design: Observational Model: Cohort
Time Perspective: Prospective

Further study details as provided by Alcon Research:

Primary Outcome Measures:
  • High and Low Contrast Acuity [ Time Frame: Day of study visit ]
    Visual acuity differences between subjects tested with full correction and spherical equivalent (SE) correction at contrast levels of 9% and 25% (low contrast acuity) and 100% (high contrast acuity). LogMAR is the "logarithm of the minimum angle of resolution". A lower logMAR value indicates better VA. These measurements were performed under photopic conditions by means of 9%, 25%, and 100% contrast ETDRS (Early Treatment Diabetic Retinopathy Study) charts (Vector Vision).

  • Contrast Sensitivity [ Time Frame: Day of Study Visit ]
    Contrast Sensitivity (CS) differences between subjects tested with full correction & spherical equivalent (SE) correction. CS is the measurement of one's ability to detect slight changes in luminance before it becomes indistinguishable. CS is measured in logarithmic units by means of an illuminated box, the CSV 1000 by Vector Vision. Testing was performed under photopic conditions (no glare) & mesopic conditions (with & without glare), and was measured at four spatial frequencies of 3, 6, 9, and 12 cycles per degree (cpd). A higher value for the logarithmic units translates to better CS.

  • Reading Acuity and Speed [ Time Frame: Day of Study Visit ]
    Reading Acuity and Speed differences between subjects tested with full correction and spherical equivalent (SE) correction. Reading Acuity was measured using the Radner reading charts, which are logarithmically scaled at different acuity levels (print sizes), and expressed in terms of logRAD (logrithmic Reading Acuity Determination). Reading speed was measured in words per minute (wpm). The results were presented as Average Reading Speed by Print Size (logRAD).

Enrollment: 40
Study Start Date: January 2009
Primary Completion Date: March 2009 (Final data collection date for primary outcome measure)
Groups/Cohorts Assigned Interventions
Visual performance measures
Collection of visual performance measures in subjects with low levels of astigmatism.
Other: Visual performance measures
Collection of visual performance measures in subjects with low levels of astigmatism.


Ages Eligible for Study:   50 Years to 75 Years   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Sampling Method:   Non-Probability Sample
Study Population
Subjects were selected from a single investigator's primary care clinic.

Inclusion Criteria:

  • 50-75 years of age
  • Proof of eye exam within the last 12 months
  • Operated for uncomplicated, age-related cataracts >3 months
  • Corneal astigmatism of 0.5-0.75 diopter

Exclusion Criteria:

  • Previous ocular or refractive surgery/trauma
  • Clinically severe corneal dystrophy
  • Amblyopia
  • Degenerative visual disorders
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT00842231

United States, Texas
Contact Alcon Call Center For Trial Locations
Fort Worth, Texas, United States, 76134
Sponsors and Collaborators
Alcon Research
  More Information

Responsible Party: Diane Houtman, OD, Associate Director, Surgical IOL Clinical Science, Alcon Research Ltd Identifier: NCT00842231     History of Changes
Other Study ID Numbers: P-08-06
Study First Received: February 11, 2009
Results First Received: August 11, 2010
Last Updated: September 23, 2010

Keywords provided by Alcon Research:
Corneal astigmatism
post-cataract surgery
visual performance
Corneal astigmatism 0.5-0.75 Diopter

Additional relevant MeSH terms:
Lens Diseases
Eye Diseases
Refractive Errors processed this record on April 28, 2017