Clinical Trial: Correlation of Scheimpflug Densitometry Measurements of Corneal Haze With Disability Glare

Study Status: Not yet recruiting
Recruit Status: Unknown status
Study Type: Observational

Official Title:

Brief Summary: Disability glare is described as "halos" or "starbursts" around bright sources of light that can cause discomfort and reduce vision. The cornea is the clear "window" at the front of the eye, but certain conditions such as a previous infection can leave a scar. Corneal scars can cause disability glare by scattering and spreading incoming light instead of allowing it to focus on the back of the eye (retina) to get a crisp image. In this study, the corneal scar will be analyzed using a new device that measures scar density (Pentacam), and a relationship with disability glare will be made. This can help us further understand disability glare and make better decisions in the future on when to treat these scars to help patients see better.

Detailed Summary:

Disability glare is a phenomenon commonly described as starbursts and halos that results in difficulty seeing clearly in the presence of bright "blinding" light. It can appear as if a veil of light is cast over the world outside. Optically, this occurs when incoming light is scattered in the eye instead of being focused on the retina. This is called straylight, and it diffusely illuminates the retina which causes desensitization of the photoreceptors and reduces the contrast of the retinal image (Lombardo & Lombardo, 2010). The main sources of scatter in the human eye are opacities in the clear ocular media, primarily due to diffusion and loss of transparency in the cornea and lens, as well as within the retina. While the lens is the largest contributor to light scatter (especially with cataract formation and aging), opacification of the cornea (e.g. scars or haze) can similarly cause intraocular light scattering, resulting in disability glare and decreased contrast sensitivity (Fan-Paul et al., 2002).

Due to the subjective nature of disability glare and contrast sensitivity, it is fairly difficult to develop a reliable objective way to measure and quantify this phenomenon. One of the most commonly used clinical tests for disability glare is the Brightness Acuity Tester (BAT), which is described as an ice cream scooper 60 mm in diameter with a 12 mm hole in the center. With the patient viewing a visual acuity chart through the hole, a uniform luminance at three different settings—high (white sand beach), medium (clear day), low (overhead lighting)—is used to induce glare and simulate the various real-life conditions. The drop in visual acuity with the various glare settings is used as a measure of disability glare. The BAT test has been found to be a reliable predictor of outdoor visual acuity (clinically validated for use in measuring disability
Sponsor: Angela Zhu

Current Primary Outcome:

• Disability glare [ Time Frame: 1 year ]
  BAT measurements of disability glare
• Visual quality [ Time Frame: 1 year ]
  NEI-VFQ25 questionnaire on functional visual quality
• Contrast sensitivity [ Time Frame: 1 year ]
  Vistech contrast grating test
• Visual acuity [ Time Frame: 1 year ]
  Visual acuity measured by Snellen chart

Original Primary Outcome: Same as current

Current Secondary Outcome:

Original Secondary Outcome:

Information By: University Hospitals Cleveland Medical Center

Dates:
Date Received: September 17, 2014
Date Started: September 2014
Date Completion:
Last Updated: September 17, 2014
Last Verified: September 2014