Contrast sensitivity testing FAQ

Addressing common questions surrounding contrast sensitivity

By David W. Evans, PhD, MBA

Contrast sensitivity (CS) is the ability to detect and differentiate subtle shades of grey in real-life low-contrast settings. CS is unlike visual acuity, which tests the ability to read high contrast black-and-white letters.

Unfortunately, there is widespread confusion about how to effectively test CS. Here are answers to some frequently asked questions regarding CS.

HOW IS CS TESTED?

Three types of tests are generally used, and all of these tests are mistakenly referred to uniformly as CS. The types of tests are:

• Low contrast acuity. This test presents letters at a lower contrast level than the standard black-on-white acuity letters, and the patient is asked to read down the chart, just like standard acuity testing.
• Letter CS. This test uses the same size letters throughout the test. The letters are broken into sets of 3 letters, each set with a decreasing level of contrast. The patient is asked to read down to the lowest contrast level where letters can still be identified.
• Threshold grating CS. This test presents bar patterns (called sine-wave gratings) of different sizes (typically four or five sizes) and contrast levels (typically seven to 10 contrast levels). The patient is asked to determine the lowest contrast level, for a specific bar size, where they can just detect the gratings. This detection task is performed for each bar size, and a curve is produced to describe vision.

WHAT ARE THE PROS AND CONS OF EACH TEST?

Tests that use letters for contrast testing have the advantage that patients are familiar with reading letters, which then can translate to less test time and potentially less variability. The disadvantages are that the test requires the identification of letters, which significantly lowers the sensitivity of the test compared to requiring a detection task, and the tests provide only one number to describe vision. Think in comparison to the audiogram hearing test. This test requires detection of specific tones (not identification of the tones) and is tested across numerous tones to describe hearing. This is the most sensitive test for audition and one that is now widely used to prescribe hearing aids.

The advantages of threshold grating testing are that it is much more sensitive than the letter tests and it provides a curve to fully describe vision. The disadvantages are that patients are not familiar with the test; thus, it can require more chair time to train and test the patients when tested for the first time, and the tests can have higher variability.

WHAT DOES THE FDA THINK?

In 2003, through a diligent evaluation process, the FDA determined that grating threshold tests were most appropriate for evaluating the overall quality of vision due to the advantages described above, as long as the test used forced-choice methodology that limited excess variability.

This process of evaluating the various tests derived from when PRK and LASIK were first approved for correcting refractive error in the United States; the FDA determined that visual acuity was inadequate to describe the visual function of post-surgical patients and began requiring CS for the FDA protocols. Various companies were using the different types of contrast tests and the FDA stepped in to standardize the protocols. The specific FDA protocol now requires testing across four different bar sizes, each using at least eight contrast levels, under photopic, mesopic and mesopic with glare conditions.

HOW IS CS USED CLINICALLY?

The widest use of CS is for the evaluation of the quality of vision when patients retain good acuity, typically with pre-surgery cataract, post-refractive surgery or post-cataract surgery IOL patients and patients with corneal conditions. For example, it is not uncommon for cataract patients to maintain good acuity yet fail the CS grating test. And, in some instances, CS can accurately quantify the concern of post-surgery patients who complain of poor quality of vision due to certain types of IOLs.

Further, for post-retinal detachment patients, who maintain good acuity, CS is highly useful. Doctors can determine the level of vision loss related to specific complaint. Some companies provide population norms to determine pass/fail, which makes it easy for the clinician to quantify to true quality of vision compared to the population.

CS is becoming more widely used to evaluate and track eye disease. New studies show glaucoma patients often recover CS when properly treated.¹ CS can track this recovery to help determine the efficacy of different treatments.

Patients at risk for vision loss from AMD often see CS improvements with proper nutrition.² This means CS can allow doctors to determine which nutritional supplement is best for the patient.

Data with patients who have early or no diabetic retinopathy shows that CS can detect early vision losses and aid with the evaluation and management of the patients.³ In addition, other types of vision complaints that are poorly quantified by acuity are also growing areas of CS use, such as for patients who experience stroke, traumatic brain injury or optic nerve damage. Finally, CS is used to evaluate visual performance, such as in athletes, pilots, etc.

Many doctors are using CS testing as part of a battery of tests for the evaluations as noted above, in many cases to evaluate vision before and after treatment. Patients are charged a fee for the additional evaluation. For example, patients are shown improvements in CS after nutritional therapy, thus allowing not only the doctor but also the patient to better understand the benefits of specific formulas.

CONCLUSION

Cataract surgery patients (and their relatives) are often pleased to learn about the significant levels of improvements in CS, even when the acuity change is small. The same is true for the battery of tests used to evaluate sports vision.

CS results benefit not only the doctor’s knowledge about the status of visual function but also the patient education and treatment experience. OM

David Evans, PhD, MBA, is Chief Science Officer and director of Guardion Health Sciences, a manufacturer of nutritional supplements and diagnostic devices. Dr. Evans is also the  founder of Guardion’s subsidiary VectorVision. 

REFERENCES

1. Fry LE, Fahy E, Chrysostomou V, et al. The coma in glaucoma: Retinal ganglion cell dysfunction and recovery. Prog Retin Eye Res. 2018;65:77-92.
2. Davey PG, Henderson T, Lem DW, et al. Visual function and macular carotenoid changes in eyes with retinal drusen — An open label randomized controlled trial to compare a micronized lipid-based carotenoid liquid supplementation and AREDS-2 formula. Nutrients. 2020;12:3271.
3. Heravian J, Shoeibi N, Azimi A, et al. Evaluation of contrast sensitivity, color vision and visual acuity in patients with and without diabetic retinopathy. Iran J Ophthalmol. 2010;22:33-40.

What you need to know about FMLA

Who qualifies and what employers need to do

By Stephanie K. Becker, MD, PC

In private practice, one of the most daunting tasks is managing employees.

We are in a COVID-driven economy where employees are a bit of a wild card. Not only do we need to keep track of which staff members may have tested positive, but we also need to ask administrative questions such as who is entitled to leave and when. Navigating the benefits of the Family and Medical Leave Act (FMLA) is complicated, but it’s important to understand so you don’t land in a difficult position with your state’s Labor Department.

WHO IS COVERED UNDER FMLA?

A covered employee for FMLA can be either in the private or public sector. In the private sector, an employer is obligated to follow the FMLA if it employs 50 or more employees in 20 or more workweeks in the current or previous calendar year. An employee is considered to be employed each working day of the calendar week if the employee works any part of the week. The workweeks do not have to be consecutive. This counts for both full- and part-time employees as well as seasonal workers. Any employee on leave is also counted, as long as there was expectation that the employee would be returning to active employment. Employees who have already been terminated or laid off or unpaid volunteers who do not appear in payroll records or documents are not counted as “covered employees.”

FMLA ELIGIBILITY

Four criteria must be met for an employee to be eligible for the FMLA:

1. Employee works for a covered employer
2. Employee has worked for the covered employer for at least 12 months from the date the FMLA leave is supposed to start
3. Employee has worked for at least 1,250 hours in the 12 months before their FMLA leave
4. Employee works at a location where you (the employer) employ at least 50 people within 75 miles of your worksite

Some of the circumstances that qualify for FMLA leave (up to 12 workweeks in a 12-month period) include: the birth of a child (mothers or fathers); serious health condition that renders employee unable to do their job (including pregnancy); care for a spouse, child or parent (not sibling) with a serious health condition.

A full list can be found at www.dol.gov/sites/dolgov/files/WHD/legacy/files/employerguide.pdf .

EMPLOYEE OBLIGATIONS

The employee must provide you, their employer, with notice that they need leave. The employer may require that employees comply with their usual protocol for requesting leave, unless unusual circumstances prevent this.

The employee’s notice may be either verbal or written. The employee is not obligated to mention the FMLA the first time they request leave; however, they do need to provide you with enough information so that you can assess that they may be covered by the FMLA. If the leave is foreseeable, the employee should indicate how much time they will need and when it will be needed. Once you have approved the FMLA for a covered reason, if the employee requests additional leave, you may ask additional questions to determine if the leave is FMLA-qualifying.

For leave that is “foreseeable,” the employee is supposed to provide at least 30 days’ notice of the need for FMLA leave. If the leave is foreseeable but your employee did not provide you with at least 30 days’ notice, even though it was “possible and practical” to do so, you can delay the FMLA until 30 days from the time you were given notice. Of course, there are times when 30 days’ notice is not “possible and practical,” in which case your employee is expected to give notice for their needed leave as soon as possible.

THE ELIGIBILITY NOTICE

If an employee is FMLA-eligible, you must provide them with notice. Consider the following:

• Notice may be verbal or written (written is recommended)
• At least one reason must be provided if it is determined that the employee is not eligible
• Notice must be provided to the employee within five business days of the initial request for leave
• Notice must be provided in a language in which the employee is literate
• Notice must provide the Rights and Responsibilities Notice (see below).

If the leave has already begun, the Rights and Responsibilities Notice should be mailed to the employee’s address of record. The Rights and Responsibilities Notice must provide the specific details relating to the leave:

• A statement of the period of the leave that can be counted for the FMLA entitlement
• Information regarding which 12-month period was used to track FMLA use
• Information regarding the need for the employee to provide verification of their need for leave
• The employee’s rights regarding their paid leave (ie, if substitution of paid leave required, or if the employee is eligible to take unpaid leave if they do not qualify for FMLA)
• If the employee is a “key employee” (ie, a salaried, FMLA-eligible employee, among the top 10% of all employees and lives within 75 miles of worksite)
• Future job restoration and the maintenance of their benefits
• If premium payments are necessary by the employee to maintain their health benefits
• Consequences for the employee not meeting their obligations toward their benefit obligations.

POSTING AND NOTICE OBLIGATIONS

Every employer covered by the FMLA must provide a general notice to their employees regarding the FMLA. To satisfy this requirement, employers must display or post a general notice (an official poster can be downloaded at www.dol.gov/agencies/whd/posters/fmla ). This poster must be displayed in an area where it can be easily seen and read by all employees, among other requirements. The full list of requirements can be viewed on page 12 of the Employer’s Guide to the Family and Medical Leave Act (tinyurl.com/exwey4jy ).

CONCLUSION

While there are still many more topics to cover, this is a good start. I recommend also reading the Wage and Hour Division of the U.S. Department of Labor’s Employer’s Guide to the Family and Medical Leave Act. Have an employee meeting and discuss the FMLA with your employees — it will spare you some surprises later. OM

Dry Eye University hosts 20th session

The program returned to in-person events this year.

By Robert Stoneback, associate editor

Dry Eye University held its 20th program on July 9-10 in Atlantic Beach, Fla. This summer’s event was the second in-person session the organization held this year since COVID protocols and restrictions began to loosen. A total of 75 attendees, made up of MD, OD, clinical and administrative staff, traveled to the conference from around the world, including Mexico and Brazil.

Patti Barkey, COE, the executive director for Dry Eye University, was concerned that participation may have suffered due to the COVID lockdown, but instead attendance was up compared to previous meetings. Many people expressed their appreciation for being able to attend again.

“It’s humbling to watch the excitement on [attendees’] faces, to know they will go back and have a project to work on that will benefit a lot of patients,” Ms. Barkey says.

SPEAKERS AND TOPICS

The two-day program included presentations on topics such as rosacea, blepharitis, neurostimulation and new therapies and products. Speakers included Ivan Mac, MD, Richard Adler, MD, Frank W. Bowden III, MD, FACS, Sarah Darbandi, MD, Jerry Robben, OD, Stephen Summerow, OD, and Ms. Barkey.

UNIVERSITY ORIGINS

The origins of Dry Eye University stem from Bowden Eye & Associates investigating new ways to treat MGD, starting in 2011 with the then-newly released LipiFlow system. TearScience (which has since been purchased by Johnson & Johnson Vision) recognized the success Bowden Eye & Associates was having using the LipiFlow system and began recommending other practices learn from Ms. Barkey’s staff. When Bowden Eye & Associated wanted to expand teaching to other dry eye therapies, Dry Eye University was created.

CONCLUSION

Approximately 26 vendors were in attendance at the July session, including ScienceBased Health, whose regional business manager, Lauren Levine, has attended 14 Dry Eye University sessions.

“Patti Barkey, Bowden Eye and Dry Eye University set the standard for dry eye programs across the country,” Ms. Levine says. “The attendees that are there have already made the decision that they want to take dry eye and their practice seriously. I don’t have to talk them into looking at dry eye as a disease. They’ve already embraced that by taking the time out of their day and attending.”

Dry Eye University’s next session will be held this fall, Oct. 22-23, at the Gaylord Texan Resort & Convention Center in Grapevine, Texas. For more information and to purchase tickets, visit www.dryeyeuniversity.com . OM

Letters to the editor

To The Editor: We are writing in regard to the article titled “Prevent postoperative endophthalmitis” (POE), published in the May 2021 issue of Ophthalmology Management. The authors, Elizabeth T. Viriya, MD and Francis S. Mah, MD state that “vancomycin should not be used as an intraocular prophylactic agent.” They justify this recommendation by stating that the outcome after hemorrhagic occlusive retinal vasculitis (HORV) is generally worse than after POE, ie, most patients that develop HORV as a result of intracameral vancomycin (ICV) have a final visual acuity of 20/200 or worse, and about one fifth of the patients have no light perception, etc. They recommend intracameral moxifloxacin (ICM) instead of ICV.

However, in order to determine the relative morbidity of alternative treatment/preventative measures, it is clearly necessary to consider not only the severity of any adverse effects but also their incidence.

Our publication¹ on this subject contains more extensive references, and can be summarized as follows. If ICM is used, the incidence of endophthalmitis is reduced from approximately 0.07% to 0.02%.² In comparison, after ICV, Paul Ernest, MD, and one of us (Richard Mackool, MD, Sr.) reported 140,000 consecutive eyes with no cases of endophthalmitis.² Other investigators³ have similarly reported no endophthalmitis or HORV in 45,000 cases. We did experience two cases of HORV in the 140,000 consecutive cases receiving vancomycin. Because severe vision loss of 20/200 or less occurs in approximately 1 of 3 eyes that develop POE, this event would be predicted to result in a postoperative acuity of 20/200 or less in 1/15,000 eyes. After HORV, the reported incidence of severe vision loss of 20/200 or worse is 61%. Therefore, with an incidence of HORV of 1/70,000 eyes, 1 in 115,000 eyes receiving ICV would suffer severe vision loss of 20/200 or less from HORV (none would be expected to have severe vision loss from POE).

In summary, based upon the available literature and our experience, the risk of severe vision loss of 20/200 or less after cataract surgery from either POE and/or HORV is nearly eight times less with ICV than the risk of such vision loss with POE after ICM.

Our current regimen at The Mackool Eye Institute is to use a concentration of 30 mg per 500 cc of BSS infusion fluid, and approximately 8,000 cataract extractions per year are performed at our ASC. — Richard Mackool, MD, Sr., & RJ Mackool, MD, Jr., Astoria, N.Y.

REFERENCES

1. Counterpoint: intracameral vancomycin during cataract surgery is a good choice for endophthalmitis prevention. Richard J. Mackool, MD and Paul Enerst, MD. Review of Ophthalmology, October 2018.
2. Haripriya A, Chang DF, Ravindrian RD. Endophthalmitis reduction with intracameral moxifloxacin prophylaxis; Analysis of 600,000 surgeries. Ophthalmology. 2017;124:768-775.
3. Intracameral antibiotics for prophylaxis of postoperative endophthalmitis in Australia: a review. Lipskey L, Barrett G. Clin Exp Ophthalmol 2019;47:537-541.

RESPONSE FROM THE ARTICLE’S AUTHORS

We appreciate the interest generated by our review on postoperative endophthalmitis. It is only with transparent discussion and sharing of knowledge that we can truly further our specialty. Our opinion and recommendation is based on the collective feeling that the devastating visual morbidity which can be caused by HORV is too great to recommend intracameral vancomycin. We are in agreement with the ASCRS,¹ the AAO,² the FDA³ and the recommendations within the AAO’s Cataract in the Adult Eye Preferred Practice Pattern.⁴ — Elizabeth T. Viriya, MD, and Francis S. Mah, MD OM

REFERENCES

1. ASCRS. Clinical Alert: HORV Association with Intraocular Vancomycin. July 2016. https://ascrs.org/clinical-education/clinical-reports/2016-cr-clinical-alert-horv-association-with-intraocular-vancomycin . Accessed Aug. 8, 2021
2. American Academy of Ophthalmology. Updated clinical characteristics of HORV. May 3, 2013. https://www.aao.org/editors-choice/updated-clinical-characteristics-of-horv . Accessed Aug. 8, 2021
3. U.S. Food & Drug Administration. A case of hemorrhagic occlusive retinal vasculitis (HORV) following intraocular injections of a compounded triamcinolone, moxifloxacin, and vancomycin formulation. Oct. 3, 2017. https://www.fda.gov/drugs/human-drug-compounding/case-hemorrhagic-occlusive-retinal-vasculitis-horv-following-intraocular-injections-compounded . Accessed Aug. 8, 2021
4. American Academy of Ophthalmology. Cataract in the Adult Eye PPP – 2016. Oct. 2016. https://www.aao.org/preferred-practice-pattern/cataract-in-adult-eye-ppp-2016 . Accessed Aug. 8, 2021.