Collarette Inc.

Family Vision Care

Call or email us at anytime with your questions.
We offer a full range of optometric services including comprehensive adult and pediatric exams, contact lenses, and vision therapy

 

Frequently Asked Questions

Q: What Is Digital Retinal Imaging?

A: Several digital retinal imaging cameras are available. These devices could also be used to transmit images over the internet. Such retinal imagers - incorporating high-resolution digital imaging with sophisticated software - are already proving to be attractive ancillary equipment for ophthalmologists.

For example, the Topcon Telemedicine System combines the TRC-NW6 Non-Mydriatic Retinal Camera with proprietary software for easy transmission of images through the internet.

Canon’s CR-DGi non-mydriatic camera also advertises telemedicine through digital imaging. Visual Pathways’s ARIS camera allows undilated fundus photography at high resolution (1000 x 1000 10-bit pixels per 30 degrees) and stores images digitally, again allowing the possibility of telemedicine.


 

Q: How Does Visual Testing for Cataracts Work?

A: We are often limited in our ability to adequately comprehend what a patient describes as decreased, blurry, or poor vision, because we can only test isolated components of visual function like Snellen acuity, contrast sensitivity, glare, color vision, and visual field. These tests give us incomplete information about a patient’s visual performance. For example, a patient may see 20/20 in each eye, but complain that while the vision in one eye is sharp and crisp, the vision in the fellow eye is blurred. It can be difficult to determine the visual significance of such a cataract since our tests do not enable us to accurately understand the quality of the patient’s sight. Visual acuity is tested monocularly with high contrast (i.e., black letters on a white background).

While this is the standard method of assessing vision, it is quite artificial and is not representative of real world conditions. Contrast sensitivity testing is more realistic but less commonly measured. Contrast sensitivity evaluates the ability to differentiate between an object and its background using low contrast letters or sine-wave gratings with different spatial frequencies. Whenever visual acuity is decreased, so is contrast sensitivity, but sometimes contrast sensitivity can be affected significantly more than visual acuity. Therefore, to better assess a patient’s visual difficulty, contrast sensitivity should be tested when the visual acuity is better than expected based on the patient’s complaints.


 

Q: What Is The Rabin Test for Contrast Sensitivity?

A: For years in the field of vision testing, the Pelli-Robson test has been the de-facto gold standard of low-contrast sensitivity testing. It has been widely accepted as the tool to turn to when testing for low-contrast sensitivity.

However, over the last two years, the Rabin Test has become the preferred product of choice for some practitioners due to its expediency: it can be done in any room setting, versus the Pelli-Robson test, which will only produce accurate results if the room lighting is calibrated precisely to the standard requirements