Diurnal Changes of the Cornea - a Pilot Study

Aim of this study is to gain a better understanding of the diurnal changes of the cornea to improve toric IOL power calculations.

Study Overview

• Status: Completed
• Conditions: Astigmatism

Detailed Description

Higher patient expectations concerning unaided visual acuity after cataract surgery has led to an increase in use of toric intraocular lenses (toric IOLs) for the correction of corneal astigmatism. Although it was shown that toric IOLs significantly reduce astigmatism, there is still some difficulty in predicting the remaining astigmatism correctly. The main source of error appears to be the pre-operative measurement of the cornea. However, it is questionable, if this error derives from a measurement error due to the imprecise measurement technique, or natural diurnal changes of the cornea. Additionally, measurements of the cornea pose several challenges: different corneal biometry devices cannot be used interchangeably and it is difficult to decide, which device is measuring the cornea correctly as there is no gold standard.

Especially, in eyes with small corneal astigmatism the error increases. Recently it was shown that the astigmatism meridian was on median 9° off for corneas with 1.0D of astigmatism and only 4° for corneas with 2.0D of astigmatism. Similar findings were observed by Shammas et al. Norrby furthermore showed that 5% of all corneas show more than 0.5D of fluctuations between measurements at different (post-operative) time-points. The reasons are not explored, but diurnal changes, temperature and humidity potentially influencing the tear film, as well as pupil size and asphericity of the cornea could play a role. Read and Collins observed diurnal changes of corneal radii within 24 hours, but in their study only young healthy volunteers were included and only one measurement device (Scheimpflug imaging, Pentacam HR) was used. Lau and Pye and Shen et al. measured the diurnal changes of the cornea, but no data concerning corneal radii were reported. Harper et al. observed diurnal changes of the central corneal thickness. However, none of these studies investigated on diurnal changes of the corneal radii in the elderly population. Aim of this study is to gain a better understanding of the diurnal changes of the cornea to improve toric IOL power calculations.

• Study Type: Observational
• Enrollment (Actual): 20

Contacts and Locations

Study Locations

• Austria
  • Vienna, Austria, 1140
    • VIROS - Vienna Institute for Research in Ocular Surgers - Departement of Opthalmology - Hanusch Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 21 years to 100 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

20 volunteers/patients (10 patients >50 years old; 5 patients with a corneal astigmatism of >1 D)

Description

Inclusion Criteria:

• 21 years, or above
• Signed informed consent

Exclusion Criteria:

• Ophthalmic diseases such as significant macular degeneration, glaucoma, diabetic retinopathy, etc.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Healthy volunteers

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Descriptive analysis of diurnal changes of the corneal radii (in diopters) and orientation of the steep meridian (in degrees) in young healthy subjects and elderly patients	24 hours

Secondary Outcome Measures

Outcome Measure	Time Frame
Comparison of the corneal radii (in diopters) and orientation of the steep meridian (in degrees) between different measuring devices	24 hours

Collaborators and Investigators

• Sponsor: Prim. Prof. Dr. Oliver Findl, MBA
• Investigators: Principal Investigator: Oliver Findl, MD, MBA, VIROS - Vienna Institute for Research in Ocular Surgers - Departement of Opthalmology - Hanusch Hospital Vienna, Vienna, Austria 1140

Study record dates

Study Major Dates

• Study Start: June 1, 2014
• Primary Completion (Actual): August 1, 2014
• Study Completion (Actual): August 1, 2014

Study Registration Dates

• First Submitted: June 2, 2014
• First Submitted That Met QC Criteria: June 2, 2014
• First Posted (Estimate): June 4, 2014

Study Record Updates

• Last Update Posted (Actual): March 16, 2020
• Last Update Submitted That Met QC Criteria: March 13, 2020
• Last Verified: March 1, 2020

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Eye Diseases; Refractive Errors; Astigmatism
• Other Study ID Numbers: DIU