Documentation of light therapy dates back 3000 years, but it wasn’t until about 100 years ago that Albert Einstein theorized the possibility of a LASER (light amplification by the stimulated emission of radiation)—yet his theories did not come to fruition until 1960, when the first working laser light was produced. Since then, lasers, laser light, and light-emitting diodes have become integral to everyday life, from communication and entertainment uses to industrial and military applications.

The medical front is rife with life-changing advances attributed to lasers, including treatment of disfiguring dermatologic conditions, ophthalmologic diseases, dental and oral maladies, prostate disease, neurologic and orthopedic conditions, and intrathoracic and abdominal conditions.

Laser Therapy Expanding in General Veterinary Practice

It is estimated that about 40% of veterinary practices offer laser therapy, officially termed 

(PBM), as part of their armamentarium. This is due in large part to a greater understanding of laser therapy and a maturing of the technology, making it safer, easier to use, and more effective on for a wider variety of clinical conditions.

Laser therapy uses a wavelength-specific form of PBM to restore normal biological function and repair injured or stressed cells. Cellular chromophores within the bloodstream and tissue mitochondria absorb the laser energy, stimulating or enhancing a series of primary biochemical processes, along with a broad cascade of secondary and tertiary effects.

The primary response is a direct photochemical reaction similar to photosynthesis or vitamin D production in the skin. This occurs when photons in the infrared range emitted by the laser reach the cell mitochondria and membranes. The photonic energy is converted to chemical kinetic energy within the cell, resulting in improved efficiency of the respiratory chain within the cell mitochondria due to changes in membrane permeability, nitric oxide formation, increased oxidative metabolism to produce more adenosine triphosphate (ATP), and improved signaling between mitochondria, nuclei, and cytosol.

 Other direct effects include the production of reactive oxygen species such as superoxide dismutase and a beneficial shift in the redox state.

Secondary and tertiary reactions amplify the primary photochemical reactions, resulting in improved cell metabolism and regulation of signaling pathways responsible for tissue repair. Blood vessels and lymphatics respond favorably, enhancing tissue perfusion and providing oxygen and nutrients needed for recovery.

 Studies document enhanced cell migration, RNA and DNA synthesis, cell mitosis, protein secretion, and cell proliferation.

 This enhances healing and production of collagen and epithelial cells.

PBM also stimulates a more normal distribution of type I and type III collagen during the healing process.

Damaged muscle and nerve cells heal faster and/or function better. The immune system, including white blood cells, functions efficiently to fight infection and clean up debris.

Not only does laser therapy enhance positive cellular processes, but it inhibits negative processes such as pain, exuberant inflammation, and aberrant immune responses. In vivo, it also stops further growth when healing is complete. This acceleration of normal healing and tissue regeneration without producing overgrowth or neoplastic transformation is a critical and unique feature of laser therapy.

Laser therapy can be used to treat cervical intervertebral disk disease.

Laser therapy offers 3 main benefits: analgesia, reduced inflammation, and faster and better recovery. It allows veterinarians to improve and resolve conditions that traditionally have been less responsive to other therapies. Soft tissue, musculoskeletal, neurologic, dermatologic, and even some intra-abdominal and intrathoracic conditions can be improved or managed more efficiently and with fewer drugs by adding laser therapy to the treatment regimen.

According to the investigators in a University of Florida study on laser therapy in spinal cord—injured dogs, “the results were so profound that we’re doing this procedure now on all dogs that come to us with this condition.”

 Other areas of interest include peripheral nerve injury, traumatic brain injury, stroke, and even depression.

Laser therapy is used in a wide range of dermatologic conditions, from acute injuries, trauma, and postoperative applications to management of chronic allergic and autoimmune/idiopathic syndromes including otitis, perianal fistulas, lick granulomas, and hot spots.

Many pathologic lung conditions respond favorably to laser therapy.

 It has helped slow the progression and/or decrease the intensity of drug therapy in conditions such as interstitial pulmonary fibrosis (Westie lung disease), feline asthma, and even tuberculosis.

Patients with chronic kidney disease have shown clinical improvement related to appetite, well-being, and nausea. The addition of laser therapy has also demonstrated improvement in chronic bladder issues including persistent infections and feline idiopathic cystitis, and it has been used as an adjunct to improve inflammatory bowel syndromes and other enteropathies.

 There are even anecdotal reports of decreased morbidity and mortality in parvovirus enteritis with the addition of laser therapy.

Laser therapy can be used as an adjunct for periodontal disease treatment.

To capitalize on laser therapy, veterinarians must understand the optimal parameters that allow it to be so effective across such a broad range of applications. The most important features to consider when buying a laser are power, wavelength, delivery mode, and training and support. Buying a laser with the widest array of options or adjustability will deliver the best clinical results on the broadest number of patients and conditions.

Power (watts) times time (seconds) delivers the dose (joules). In laser therapy, joules/cm

 is as critical to laser success as mg/kg of an antibiotic or mL/kg of fluid is to clinical success. The power should be adjustable from low, for small or superficial conditions or patients and acupuncture points, to high, to efficiently deliver enough energy (joules) to saturate/stimulate large areas or patients as well as deep-seated and/ or chronic musculoskeletal conditions.

The availability and selection of wavelength are important for optimal stimulation of different chromophores as well as levels of penetration. Roughly, this corresponds to wavelengths between 600 and 1100 nm. Shorter wavelengths are absorbed more superficially and thus cannot penetrate as readily as longer wavelengths. Wavelengths in the visible red range (660 nm) are highly absorbed by melanin and other superficial receptors. These can enhance wound healing. They may also stimulate trigger points and acupuncture points and cause release of secondary messengers that may improve other deep-seated conditions. Absorption spectra data have shown that wavelengths near the 970-nm range have moderate increased absorption by water.

 This is the least penetrating infrared wavelength. With higher-powered lasers, this can create some thermal gradients and increase circulation. The 905-nm wavelength is nearest the peak of the hemoglobin absorption curve. This can enhance oxygen release more efficiently. Results from recent studies have indicated that this wavelength may be able to increase oxygen release even more efficiently to tissue over the 970- to 980-nm wavelengths.

Wavelengths nearer the 800-nm range (750-830 nm) are at the peak of absorption for the cytochrome c oxidase enzyme. This is the rate-limiting step in the conversion of oxygen to ATP within the electron transport cycle. These wavelengths will accelerate the production of ATP within the mitochondria. There is new interest in the 1064-nm wavelength, particularly for its photochemical effects. This wavelength is farthest from the point of maximum melanin production, has a relative trough in the water absorption spectrum, and is still at the upper level of the cytochrome c oxidase absorption band. Therefore, it has very good penetration depth along with potent biostimulatory abilities. Having all 4 (or 5) wavelengths as well as the ability to use any combination will offer a synergistic effect and/or a wider range of treatment options across a broader spectrum of clinical conditions and patients.

Delivery mode (continuous wave, pulsed or modulated, superpulse) will enhance overall improvement and produce better clinical results. Varying pulse rates enhance different physiologic responses as well as different tissue types to a greater degree.

 Optimal pulsing frequencies are still being studied, but current literature consistently shows that overall clinical results will be higher if pulsing phases, rather than continuous-wave delivery, are part of the treatment protocol.

Although the technology behind laser therapy may sound complicated, training is paramount and the learning curve is not high. Ignoring or dismissing certain features will decrease the consistency in results, the degree or quality of improvement, and the number of conditions that will respond favorably. Today’s lasers are very safe and user-friendly. The protocols already set up in advanced therapeutic lasers incorporate all the parameters in a “point-and-shoot” instrument. This ease of use, along with proper training, will allow veterinary practices to institute laser therapy quickly and easily. It can and should be delegated to the staff for the most efficient treatment and economic benefits.

Future studies will enhance our knowledge of the variety of applications and the optimal parameters for the most effective laser therapy. The goal is not to just make our patients more comfortable—we want to return them to their normal activity level, restore range of motion, and improve muscle strength and function. Laser therapy allows performance animals to recover more quickly and more fully to regain their competitive edge and helps pets remain active members of the family.

Dr. Bradley is the veterinary medical director for K-LASER USA in Franklin, Tennessee. He began using lasers in private practice in 1999 and has worked with all types of surgical and therapeutic lasers. He was granted Fellow status in the American Society of Laser Medicine and Surgery. He has authored numerous articles and chapters and has lectured nationally and internationally on veterinary laser use. 

. London, UK: Harwood Academic Publishers; 1989.

2.      Hawkins D, Abrahamse H. Phototherapy—A treatment modality for wound healing and pain relief. 

3.      Kubota J. Effects of diode laser therapy on blood flow in axial pattern flaps in the rat model. 

4.      Tunér J, Hode L. Some basic laser physics. In 

Laser Therapy - Clinical Practice and Scientific Background

. Grängesberg, Sweden: Prima Books AB; 2002:12, 21, 22.

5.      Wood VT. Collagen changes and realignment induced by low-level laser therapy and low-intensity ultrasound in the calcaneal tendon. 

6.      Paraguassú G, Xavier FCA, Cangussu MCT, et al. Effect of laser phototherapy (660nm) on type I and III collagen expression during wound healing in hypothyroid rats: an immunohistochemical study in a rodent model. 

7.      Karu T. Primary and secondary mechanisms of action of visible to near-IR radiation on cells. 

8.      Peavy GM. Lasers and laser-tissue interaction. 

9.      Martin R. Laser accelerated inflammation/pain reduction and healing. 

10.    Karu T, Kolyakov SF. Exact action spectra for cellular responses relevant to phototherapy. 

11.    Hamblin MR, Demidova TN. Mechanisms of low level light therapy. 

12.    Draper WE. Low-level laser therapy reduces time to ambulation in dogs after hemilaminectomy: A preliminary study. 

13.    Kirkby KA, Freeman DE, Morton AJ, et al. The effects of low-level laser therapy in a rat model of intestinal ischemia—reperfusion injury. 

14.    Milojevic M, Kuruc V. Laser biostimulation in the treatment of pleurisy [in Serbian]. 

15.    Siqueira VPC, Evangelista MIS, Dos Santos A, et al. Light-emitting diode treatment ameliorates allergic lung inflammation in experimental model of asthma induced by ovalbumin. 

16.    Redkin AV, Vdovin VV, Vakhtel VM, Lukyanovich PA, Malkina NA. Reduce adverse effects of laparoscopic cholecystectomy with pulse width modulated led light (625 nm, 76 Hz, 23% duty cycle). 

17.    Hudson DE. Penetration of laser light at 808 and 980nm in bovine tissue samples. 

18.    Anders JJ. Moges H, Wu X, et al. In vitro and in vivo optimization of infrared laser treatment for injured peripheral nerves. 

19.    Cheida AA. Resonance response of cell tissue structures to impulse frequency of infrared laser radiation of low intensity. 

20.    Karu T. et al. Studies into the action specifics of a pulsed GaALAS laser (‘wavelength’ s20 nm) on a cell culture. 

21.    Karu T. Nonmonotomic behavior of the dose dependence of the radiation effect on cells in vitro exposed to pulsed laser radiation at 820 nm. 

22.    Hashmi J. Effect of pulsing in low-level light therapy. 

Articles

Clinical Focus

Photobiomodulation can improve healing&mdash;and quality of life&mdash;for veterinary patients with a host of health conditions.

Laser Therapy Today

About half of cats with murmurs have diagnosable cardiac disease. 

Cats are more adept than dogs at hiding clinical signs of heart disease, according to Rebecca Stepien, DVM, DACVIM, clinical professor of cardiology at the University of Wisconsin School of Veterinary Medicine. That’s why it is important to use multiple available diagnostic tools to detect and stage cardiac disease in cats. At the 2018 Midwest Veterinary Conference in Columbus, Ohio, Dr. Stepien presented the latest tools for diagnosis of cardiac abnormalities in cats. She began by emphasizing the importance of differentiating heart disease and heart failure in the feline patient.

Differentiating Heart Disease and Heart Failure 

Cardiac disease, she said, is typically monitored rather than clinically treated in cats, whereas cardiac failure is almost always treated. Heart disease is defined as a physical or functional abnormality of 1 or more components of the cardiovascular system; heart failure occurs when cardiac output provides inadequate blood pressure for organ perfusion despite normal hydration status. Cardiac failure may manifest clinically as hypotension due to low cardiac output or as congestion, edema, or other fluid accumulation due to sodium and/or water retention.

ACVC 2016: Hyperthyroidism in Cats - What You Need to Know

New Heart Disease Drug May Help Both Cats and People

Detecting asymptomatic heart disease in cats is not a straightforward process. Dr. Stepien estimated that approximately one-quarter to one-third of overtly healthy cats have heart murmurs. About half of cats with murmurs have diagnosable cardiac disease, while in the other half the murmurs are innocent. Dr. Stepien emphasized, “No murmur likely means no disease.” She added that the most common life stage for development of myocardial disease begins at about 6 to 8 years of age and decreases after 12 to 14 years.

To determine whether a heart murmur is causing disease, Dr. Stepien advised examining for additional abnormal findings, especially a gallop heart sound or cardiac arrhythmia. Gallop heart sounds occur when rapid ventricular filling suddenly stops because of abnormal stiffness of the ventricular wall, thus generating a third heart sound. The condition, which may be temporary or permanent, can be caused by a variety of pathologies, including hypertrophic or dilated cardiomyopathy, ventricular fibrosis (eg, restrictive cardiomyopathy), and neoplasia. In particular, Dr. Stepien noted, feline lymphoma can infiltrate and stiffen the heart wall. Increased ventricular dilation leading to gallop heart sounds can also occur in patients with renal disease after receiving fluid therapy because of overhydration and increased blood volume. The combination of a cardiac murmur and an arrhythmia also increases the likelihood of true cardiac disease, she said.

Heart Murmur in a Healthy Cat: Should I Still Worry?

A heart murmur may warrant additional investigation even in patients with no outward clinical signs, Dr. Stepien noted. Further diagnostics should be performed before any cat with a murmur undergoes anesthesia or receives fluid therapy. Also, certain systemic diseases, such as occult hypertension, anemia, and hyperthyroidism, can exacerbate a murmur and should be ruled out. Finally, some clients may encourage further diagnostics for peace of mind.

Diagnostic Imaging for Cardiac Abnormalities

Dr. Stepien noted that radiology is more useful than echocardiography for assessing congestive heart failure, but echocardiography is needed to evaluate cardiac anatomy. Many cats with cardiac disease lack significant atrial and/or ventricular enlargement on radiographs but will show enlargement when imaged by echocardiography. Obese cats frequently deposit fat in the pericardium, thus enlarging the cardiac silhouette on radiography even in the absence of cardiac disease. In such cases, Dr. Stepien advised examining the pulmonary vessels as an additional indicator of cardiac disease. She also noted that if the heart touches the diaphragm, it is likely enlarged.

Another limitation of radiography is the large overlap in vertebral heart scores between normal and abnormal cats. According to 1 study, a vertebral heart score of 8 or higher is only 78% sensitive for detecting left heart disease with no or mild left atrial enlargement

; however, sensitivity increases to 91% if left atrial enlargement is mild to moderate. Study results showed that vertebral heart score was 82% specific for detecting left heart disease, regardless of left atrial size. Therefore, vertebral heart score may be an unreliable predictor of cardiac disease. Dr. Stepien emphasized the use of echocardiography, particularly for detecting preclinical heart disease in cats. An echocardiogram provides direct information on heart structure, such as wall thickness and chamber size, as well as function. In particular, Doppler echocardiography is valuable for assessing systolic and diastolic function. An echocardiogram can also identify pleural effusion, diaphragmatic hernia, and mass lesions and can differentiate between benign and disease-related causes of heart murmur and gallop heart sounds. In short, echocardiography is an incredibly useful tool to help rule in or out heart disease.

Echocardiography holds particular value for screening at-risk cat breeds, including the sphynx and Maine coon, for hypertrophic cardiomyopathy before breeding. As noted earlier, diagnostics such as echocardiography should be performed before administering anesthesia or fluid therapy in patients with heart murmurs. Echocardiography is also the most effective tool for detecting intracardiac thrombi.

 Dr. Stepien noted that thoracic ultrasound is much less stressful than radiographs to perform on an unstable patient, and even a brief or limited scan can still provide valuable information, such as the presence or absence of pleural effusion. She allows particularly fragile patients to remain sternal and receive supplemental oxygen rather than placing them in lateral recumbency. Dr. Stepien emphasized looking at the left atrium, which will likely be enlarged in a cat with signs of congestive heart failure, such as pleural effusion and pulmonary edema. A left atrium measuring more than 1.5 times the diameter of the aorta likely indicates heart disease.

Thoracic ultrasound can also detect the presence of lung infiltrates related to heart disease, as in cases of pulmonary edema. The dorsal lung field offers an ideal location to view lung tissue by orienting the ultrasound probe between the ribs. Although the appearance of white horizontal lines, or A lines, is normal on thoracic sonography, fluid in the lungs will cause white vertical lines or “rockets” that descend vertically from the probe location.

Although echocardiography remains the gold standard for diagnosing heart disease in cats, Dr. Stepien acknowledged that many veterinarians lack access to this tool. “That doesn’t keep you from being a good practitioner,” she assured the audience. Recent advancements in cardiology include measurement of cardiac stress markers, she said.

B-type natriuretic peptide (BNP) is a hormone that regulates blood pressure and fluid balance through renal sodium and water loss as well as vasodilation. BNP is synthesized and stored in the cardiac myocytes as the promolecule proBNP. Secretion of proBNP by the myocytes is continuous and increases with excessive stretching, pressure, or expansion of the cells. Because many forms of heart disease, such as hypertrophic cardiomyopathy, cause excessive stretching of the heart muscle, BNP is an appropriate marker for assessing for the presence of heart disease. In general, the amount of circulating BNP correlates with severity of cardiac stress.

In veterinary medicine, quantitative and semiquantitative tests are available to estimate plasma N-terminal (NT)-proBNP concentrations. The measured form of BNP, NT-proBNP, is 1 cleaved end of the secreted proBNP molecule. NT-proBNP is stable and has a long half-life, making it a good indicator of circulating BNP concentrations.

The enzyme-linked immunosorbent assay (ELISA) NT-proBNP test is available from Idexx as the feline CardioPet proBNP test, which provides a quantitative result, as the amount of visible marker is proportional to the amount of circulating BNP. The SNAP feline semiquantitative test provides a positive or negative result for NT-proBNP, with a cutoff value of about 150 pmol/L. A “very dark” positive dot indicates a relatively high value, suggesting more severe cardiac stress.

Heart disease and heart failure both raise NT-proBNP levels

; however, increased NT-proBNP may occur in patients with “normal” echocardiogram findings. In such cases, it is important to rule out other causes of increased NT-proBNP. Several diseases, including systemic hypertension

 may increase NT-proBNP by affecting blood volume or cardiac work—related stress. Concentrations may also rise in cats with true renal insufficiency or prerenal azotemia due to dehydration, as NT-proBNP excretion occurs in the kidneys. Dr. Stepien noted that renal disease appears to have a lesser effect on NT-proBNP concentration in cats than in dogs and humans.

As a general rule, the greater the NT-proBNP concentration, the more severe the abnormality is. Primary cardiomyopathy causes higher NT-proBNP concentrations compared with secondary cardiomyopathy due to hyperthyroidism or hypertension. Heart disease cases also have higher NT-proBNP values than cases of impaired NT-proBNP excretion due to renal disease. Dr. Stepien added that congestive heart failure usually corresponds to higher NT-proBNP values than does heart disease alone. She provided general guidelines for interpreting NT-proBNP SNAP results (

Although the exact cutoff values are not clear, 1 study determined that a quantitative NT-proBNP test result of 99 pmol/L or higher effectively detected subclinical cardiomyopathy (sensitivity 71%, specificity 100%).

 Results from another study showed that dyspneic cats with a plasma NT-proBNP value above 265 pmol/L were likely to have heart failure (sensitivity 90%, specificity 88%).

 Cats with congestive heart failure had a median NT-proBNP value of 754 pmol/L, and 90% of values exceeded 300 pmol/L.3 A higher NT-proBNP value, Dr. Stepien stated, should increase confidence in a congestive heart failure diagnosis.

Quantitative NT-proBNP measurement using ELISA can also help clarify ambiguous situations, such as differentiating innocent murmurs from associated disease or correlating respiratory signs with heart failure.

NT-proBNP assessment, however, does have limita- tions. The test cannot specify the type of heart disease present, nor will it provide an indication for therapy. Also, research has not yet established whether NT-proBNP measurement can reliably detect preclinical genetic disease. The value of NT-proBNP measurement, Dr. Stepien stressed, lies in aiding interpretation of other clinical findings.

Clinical applications differ for the semiquantita- tive SNAP and quantitative ELISA tests, Dr. Stepien stated. The SNAP test is best used when the extent of cardiac stress needs to be determined immediately, as the quantitative test costs more and has a 12- to 24-hour turnaround time. The SNAP test is also particularly valuable for confirming suspect-normal cases, particularly before administering anesthesia or fluid therapy. Examples include a relatively low-risk, young cat with a murmur or a dyspneic cat with a history of respiratory disease but no history of cardiac disease.

Dr. Stepien reminded the audience that the cutoff value of 150 pmol/L NT-proBNP for the SNAP test is similar to the approximately 100 pmol/L cutoff for asymptomatic heart disease.

 Therefore, a positive SNAP test likely indicates the presence of heart disease, whether subclinical or clinical.

Dr. Stepien recommended the quantitative ELISA test for suspect heart disease cases for which an echocardiogram cannot be performed, as the quantitative test still provides an indication of disease severity. The quantitative test can also help track heart disease cases over time as well as provide further clarity after a positive SNAP test result.

My Patient Has Elevated BNP Levels. Should I Treat for Cardiac Disease?

Dr. Stepien reminded the audience that a positive SNAP or ELISA NT-proBNP test result should always be interpreted in combination and other diagnostic findings. "This way," she said, "one can look for suggestive evidence of heart failure, such as auscultatory or radiographic abnormalities, arrhythmia, and dyspnea." Treatment should be initiated if clinical signs indicate cardiac failure.

No diagnostic test is perfect, and the NT-proBNP test has limitations. The test is more sensitive than echocardiography; therefore, NT-proBNP levels may rise before abnormalities are visible on an echocardiogram. Likewise, marginal increases in NT-proBNP may occur because of other diseases

or may hover close to the cutoff point for abnormality.

 Finally, a patient’s NT-proBNP values can vary as much as 13% day to day and 21% week to week.

In summary, the NT-proBNP test is particularly helpful for cases in which ruling out heart disease helps avoid more costly evaluation or for those in which physical examination and diagnostic tests have provided inconclusive evidence of heart disease.

Evaluation of feline cardiovascular disease should include a combination of available diagnostic tools, including physical examination, thoracic radiography, electrocardiography (in cases of arrhythmia), echocardiography, and NT-proBNP measurement. Diseases with secondary cardiac effects, such as hyperthyroidism and renal disease, should also be considered in cats with cardiac abnormalities.

Dr. Stilwell received her DVM from Auburn University, followed by a MS in fisheries and aquatic sciences and a PhD in veterinary medical sciences from the University of Florida. She provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting.

Guglielmini C, Baron Toaldo M, Poser H, et al. Diagnostic accuracy of the vertebral heart score and other radiographic indices in the detection of cardiac enlargement in cats with different cardiac disorders. 

Connolly DJ, Magalhaes R, Fuentes VL, et al. Assessment of the diagnostic accuracy of circulating natriuretic peptide concentrations to distinguish between cats with cardiac and non-cardiac causes of respiratory distress. 

Fox PR, Oyama MA, Reynolds C, et al. Utility of plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) to distinguish between congestive heart failure and non-cardiac causes of acute dyspnea in cats. 

Fox PR, Rush JE, Reynolds CA, et al. Multicenter evaluation of plasma N-terminal probrain natriuretic peptide (NT-pro BNP) as a  biochemical screening test for asymptomatic (occult) cardiomyopathy in cats. 

Lalor SM, Connolly DJ, Elliott J, Syme HM. Plasma concentrations of natriuretic peptides in normal cats and normotensive and hypertensive cats with chronic kidney disease. 

Sangster JK, Panciera DL, Abbott JA, Zimmerman KC, Lantis AC. Cardiac biomarkers in hyperthyroid cats. 

Harris AN, Beatty SS, Estrada AH, et al. Investigation of an N-terminal prohormone of brain natriuretic peptide point-of-care ELISA in clinically normal cats and cats with cardiac disease. 

Harris AN, Estrada AH, Gallagher AE, et al. Biologic variability of N-terminal pro-brain natriuretic peptide in adult healthy cats. 

Conference Coverage

Combining radiology, echocardiography, and cardiac stress marker results can bring clarity to ambiguous cases.

MVC 2018: Advances in Feline Heart Disease Diagnosis

Judging by the excellent attendance at sessions on business and practice management topics at the American Veterinary Medical Association Convention last month, it’s clear that business-related and mental well-being subjects are very important to today’s veterinarians. Since its inception last year, 

 has strived to provide insight on the important information that most veterinarians never learned in school—personal and practice finance, practice and personnel management, law, mental health, time management, communication, and related topics that are vital to running a successful business.

It’s also clear—based on the 100+ veterinary-related journals included on PubMed and the plethora of available trade publications like 

—that there is more animal health care information available to veterinary professionals than any one person could ever hope to keep up with. As much as you’d like to pore through the multiple professional magazines you likely receive each month, the fact is you’ve got limited time to actually read them.

 has a slightly new look this month. This seemingly minor design alteration represents a major change for us: We have combined 

Although a number of factors contributed to our decision to combine the magazines, one of the primary reasons was to give readers one less magazine to have to keep track of each month. A single publication means you now have all of the expert insight, news, and conference information that you’ve come to expect at your fingertips and in one place.

Rest assured that we will continue to include cutting-edge clinical news, research highlights, and conference coverage in

. But we’ll now also offer content that will propel you forward professionally as well as lifestyle and wellness articles to ensure you maintain a happy personal life. Check out our articles on 

We’re also in the process of combining the robust websites of these valuable platforms. You can look forward to a user-friendly, interactive learning experience that will continue to offer multiple daily articles and expert videos to help you practice better medicine and stay up-to-date with industry, conference, and research news. We also send multiple newsletters each week, so be sure to sign up on 

And speaking of staying in the know, there is still time to register for the

 2018 Atlantic Coast Veterinary Conference

. From October 8 through 11, Atlantic City, New Jersey, will be home to more than 200 hours of RACE-approved continuing education, a stocked exhibit hall, and myriad networking opportunities. We hope to see you there!

Letter from the Chairman

We have combined American Veterinarian® and Veterinarian’s Money Digest® into a single publication under the American Veterinarian® umbrella.

New Look, Same Great Content

). Companion animals do not distinguish between red, green, and yellow. (Image from Cook1; used with permission) 

Every now and then veterinarians are asked about animal vision: “Are dogs truly color blind?” or “Do cats have superior night vision?” or “Who sees better, my dog or my cat?” Vision is an extremely complex sense that is influenced by various elements, differs significantly among species, and can be tested using many methodologies. Thus, there is no easy way to answer these questions.

It’s true that some animals, including cats and dogs, may be partially color blind, but certain aspects of their vision are superior to that of humans. Not only is it interesting to imagine how your patients see the world, but having a better understanding of their vision can positively influence, for example, the choice of lighting you use in your office.

Prevalence of Ophthalmologic Diseases in Other Countries

Although this review is not intended to offer an exhaustive discussion of the topic, it does focus (pun intended) on select aspects of vision in our patients.

Do Your Patients See in Black and White? 

We’ll start with the most popular question: Are cats and dogs able to see color? Cone photoreceptors are responsible for color vision in all species. The richness of color vision, and the number of shades that an eye can see, are determined by the number of cone photopigment populations and the degree of overlap in their absorbance spectrum.

To better understand how your patients see, it’s helpful to know that humans have 3 cone photopigment populations, with peak absorbance in the red, blue, and green wavelengths—which is why these are our 3 primary colors&mdash;making humans a trichromatic species. On the other end of the spectrum are monochromatic species, which have only a single photopigment population. This type of vision is characteristic of nocturnal species, which can perceive only shades of a single photopigment, usually with a red/green hue.

Most domestic animals are dichromatic, meaning they possess 2 photopigment populations. So, contrary to popular belief, domestic animals do not see in black and white. They have color vision, although not as rich as that of us trichromatic humans.

Cats, dogs, cattle, and horses all have 2 photopigment populations, with absorbance peaks of about 440 and 555 nm. Consequently, these species can see blue but have difficulty distinguishing between red, green, and yellow. Color vision in these species is analogous to that of “color-blind” humans, who are usually missing their red and green cone population (

If you think humans have the most superior vision, however, you’d be mistaken. Many fish and bird species are tetrachromatic, meaning they have a fourth photopigment absorbing light in the ultraviolet end of the color spectrum. As such, they possess color vision that is significantly richer than humans.

The frontal part of the visual field is covered by both eyes, resulting in binocular vision, which is traditionally required for depth perception. The monocular visual field is the lateral visual field of each eye, in which there is no input from the other eye. The extent of the monocular and binocular visual fields is largely dictated by the location of the orbits and eyes in the skull.

 The extent of the visual field in a dog, horse, and cat. Note that the panoramic vision of the horse comes at the expense of a small, frontal binocular visual field. Predators such as dogs and cats have a large frontal, binocular field of vision essential for depth perception, but suffer from a large blind spot behind them (Courtesy: Mr. John Doval, UC Davis).

Species with front-facing eyes have a large binocular visual field. Consequently, they have 2 small lateral monocular visual fields and a large posterior blind spot. Frontal eyes are found in predator species that require superior depth perception for accurate spatial localization when pouncing on their prey. Dogs, cats, and raptor birds fall into this category. The evolutionary price paid in the form of small peripheral fields and a large blind spot is of less concern to predator species.

On the other hand, herbivores have lateral orbits, giving them a small frontal binocular visual field and 2 large lateral monocular fields of vision that give them almost 360° panoramic vision. The large lateral monocular fields are important to these species as most of them need to see approaching predators.

How do visual fields compare? The total visual field of cats is estimated at 200°, including a 140° frontal binocular field and 2 lateral monocular fields of 30° each (

). Horses are estimated to have a visual field of about 355°, including a frontal binocular field of 65° and 2 large lateral monocular fields of about 145° each. To know the implication of these numbers, consider that enucleation of 1 eye would cause a cat to lose 30° of its total visual field and a horse nearly 145° of its total visual field. With the loss of an eye, then, a horse could become dangerous and easily scared by objects moving on the side with vision loss.

When photoreceptors are stimulated by a flash of light, they need a minimum amount of time to recover before they can respond to a subsequent flash. If the flashes are presented rapidly, the photoreceptors do not have enough time to recover fully. Beyond a certain threshold, flashes become so rapid that the retina is unable to recover. At this point, the retina is no longer able to perceive or respond to the individual flashes, resulting in “fusion” of the responses and the perception of a continuous, rather than a flickering, light.

In humans, cone responses fuse at 45 Hz. Therefore, images projected on television or computer screens, which flicker at 60 Hz (in the United States), are perceived as a continuous image. But in many other species, cone responses fuse at 70 to 80 Hz. As a result, pets can perceive individual flickering images when watching television, which can have a dramatic effect on their interest in the program.

For the same reason, companion animals can detect the flickering of fluorescent lights. This is an important distinction that should be considered when selecting lighting for your hospital. Yellow, incandescent or LED bulbs that do not flicker provide the patient with a more hospitable atmosphere.

). At night, a cat’s vision is about 6 times better than a human’s. (Courtesy: Shlomi Levi, DVM, Hachaklait)

The common narrative that companion animals have very sensitive night vision is based in truth. Study results show that cats can detect light that is 6 times dimmer than the lowest detectable threshold of humans (

This is due to several factors. First is the amount of light entering the eye. Cats have very large corneas and pupils, with diameters about 50% larger than those of humans. Therefore, more light can pass through feline eyes and reach the retina.

Second, with the exception of pigs, all domestic species possess a tapetum lucidum, a reflective tissue located in the choroid behind the retina. Light that is not absorbed by the retinal photopigment strikes the tapetum and reflects back to the retina, doubling the chances that it will be absorbed. Thus, the tapetum acts as a mirror that helps the animal increase retinal illumination in dim light. But there is an evolutionary price to be paid. The light reflected by the tapetum is scattered in the eye, reducing visual resolution. This has little consequence at night when cones, which are responsible for high-resolution vision, are inactive, but it becomes very detrimental in daylight.

The third and most critical factor that affects night vision is the distribution and concentration of retinal photoreceptors. In the retinal periphery, the maximal rod concentration in cats is about 5 times higher than that in humans. Because rods are much more sensitive to low light levels, and in fact can detect a single photon, this high rod concentration provides cats with their highly sensitive night vision and motion perception.

Visual resolution is determined mostly by the optics of the eye and the anatomy of the retina. Optically, in an emmetropic eye, light focuses properly on the retinal photoreceptors, contributing to a sharp image. In a short-sighted (myopic) eye, the image is focused in front of the retina, while in a far-sighted (hyperopic) eye the image is focused behind the retina, both of which result in a blurry image.

Findings from a study of 1500 dogs showed that a majority are emmetropic, meaning the optics of their eyes are calibrated to generate a focused image on the retina.

 If these dogs were humans, they would not require corrective glasses. The same study’s results showed that about 25% of all dogs are short-sighted, with a refractive error ranging from —0.5 to –6.0 D.

For some dog breeds, the average refractive error is myopic. For example, two-thirds of Rottweilers studied were short sighted, with a mean refractive error of —1.8 D.

 Similarly, significant numbers of dogs were far sighted, with certain breeds having a mean far-sighted refractive state.

For example, the Australian shepherd has a mean refractive error of +1.3 D.

Visual resolution is also determined by retinal anatomy. As noted, factors that contribute to enhanced night vision have a detrimental effect on daytime vision and visual resolution. Thus, the presence of a tapetum lucidum in the eyes of dogs and cats causes scattering of light that reduces visual resolution. Furthermore, differences in the concentration of cones, which process high-resolution images, also affect visual resolution. In companion animals, the concentration of these cells is lower than in humans, resulting in lower visual resolution. For example, the maximal cone concentration in the feline retina is one-eighth that in the human retina. Consequently, even if a dog or a cat is emmetropic, and has a well-focused image on the retina, its visual resolution will be reduced because the resolving power of the eye is attenuated by the low cone concentration in the retinas.

Visual acuity is typically expressed as a Snellen fraction, and this is where people have the advantage. The acuity of normal humans is the well-known figure, 20/20. By comparison, the visual acuity of horses is estimated to be 20/33, meaning that a horse must be 20 feet from an object to see it as well as a person standing 33 feet away can see it.

Visual acuity is 20/75 in dogs and 20/150 in cats. In other words, a cat has half the acuity of a dog and a fifth of the acuity of a horse. The simple translation: A cat has to be more than 7 times closer to an object to see it as sharply as we do! These figures are based on the assumption that the animal is emmetropic. If the animal is not emmetropic, then its visual resolution will be poorer.

Dr. Ofri is a professor of comparative ophthalmology at the Koret School of Veterinary Medicine, Hebrew University of Jerusalem in Rehovot, Israel. 

The spectral reflectivity of the cat's tapetum measured in situ.

Kubai MA, Bentley E, Miller PE, Mutti DO, Murphy CJ. Refractive states of eyes and association between ametropia and breed in dogs. 

Hernandez J, Moore C, Si X, Richer S, Jackson J, Wang W. Aging dogs manifest myopia as measured by autorefractor. 

Imamoto Y, Shichida Y. Cone visual pigments. 

Miller PE. The eye and vision. In: Maggs DJ, Miller PE, Ofri R (Eds). 

Slatter’s Fundamentals of Veterinary Ophthalmology

, 6th ed. St Louis, MO: Saunders Elsevier 2018:1-17.

Miller PE, Murphy CJ. Equine vision: normal and abnormal. In: Gilger BC (Ed). 

 3rd ed. Ames, IA: John Wiley & Sons; 2017:508-544.

Ofri R. Optics and physiology of vision. In: Gelatt KN, Gilger BC, Kern TJ (Eds). 

 5th ed. Ames IA: John Wiley & Sons; 2013:304-410.

Ofri R, Hollingsworth SR, Groth A, et al. Effect of optical defocus on performance of dogs involved in field trial competition. 

Do animals see in black and white? Answers to common questions from clients.

Vision in Dogs and Cats

In recent months, many major airlines have tightened their regulations regarding service and emotional support animals traveling on board flights—actions that have raised a number of questions for veterinarians:

How can veterinarians protect themselves while assisting pet owners in caring for these animals?

How do you provide health care to the pet yet not give an evaluation of its behavior or training?

What is the veterinarian’s role in this 2-sided pet care question?

At the recent Animals on the Mind 3.0 conference, hosted in May by the Institute for Human-Animal Connection, nonveterinarian experts in the field of human—animal interaction spent 2 days exploring these questions. Psychologists, animal trainers, and service/support animal handlers shared their perspectives on identifying these pets while caring for both the person and the animal.

Airlines Update Pet Policies (Again), Ban Breeds

Emotional Support Animals: New Rules, Proposed Laws

No one disputes the benefits available to people who use service or support animals. Because these animals come in all shapes and sizes with varying training levels and abilities, however, the temptation to abuse the privilege is always present.

At the conference, presenting researchers and service, emotional support, and therapy dog users were careful to point out how the handler/animal team works. They clearly had a deep awareness of the needs of the animal in these interdependent relationships. To them, the pets’ needs were as important as any human therapeutic benefits that resulted from these relationships.

Given these studies, completed on a much more evaluative level of observation of the training and behavior of the animal and the handler, how can veterinarians adequately observe and evaluate a pet being asked to do tasks? Is it even their role as health care providers to make such an evaluation during a pet’s pretravel health check? Questions involving the legitimacy of a service, emotional support, or therapy pet or its ability to behave on a plane creates a conundrum for the veterinarian.

In early March, the American Veterinary Medical Association (AVMA) announced that it had reached an agreement with United Airlines to revise the carrier’s Veterinary Health Form, which is now required prior to flying with a service or emotional support animal.

 The AVMA contended that the information being requested in the original version of the form might not position United Airlines to make good decisions that would support the health and welfare of both human and animal passengers. The AVMA also expressed concern that the statements on the form created potential liability risks for veterinarians attesting to them. In reality, veterinarians cannot and should not vouch for the training or behavior of any animal in their practice. It is beyond the scope of their examination, training, and expertise. What a veterinarian observes about a dog in the confines of a veterinary hospital might be quite different from how the dog reacts in a pressurized, noisy airline cabin.

Now the question remains: How can veterinarians serve their clients and themselves when it comes to providing a health check of a service or emotional support dog?

First, it’s important to understand the differences between a service animal and an emotional support animal. Service animals, which are acquired after months of individualized and partnership training, have federally protected rights under the Americans With Disabilities Act. They must be granted reasonable access anywhere.

An emotional support animal has protected access under the Fair Housing Act and Air Carrier Access Act, passed in 1988 and 1986, respectively. Reasonable accommodations must be made upon proof that the pet provides a necessary service. Emotional support animals provide a service by their mere presence; no real training is required. For emotional support animals to fly in the cabin of a plan, a doctor's note identifying the support the animal provides and the symptom(s) it ameliorates is mandatory.

Many veterinarians feel compelled to verify a service animal’s training and behavior, but this is not within the scope of their training. Instead, they should explain to their clients that they can only sign the health voucher. It is all they can uniquely do with their training and expertise.

Now that the AVMA has helped United Airlines reshape its form, it also hopes to work with other airlines to create more appropriate veterinary health forms, ensuring the safe travel of service and emotional support animals while keeping passengers and crew members protected.

Ms. Vey Voda-Hamilton is an attorney/mediator and principal at Hamilton Law and Mediation, the first mediation practice to focus specifically on conflicts between people over animals. She is a best-selling author of “Nipped in the Bud, Not in the Butt — How to Use Mediation to Resolve Conflicts Over Animals,” which outlines the methods she uses to address conflict, keep clients and appreciate another’s point of view in a disagreement.

AVMA, United Airlines reach agreement on veterinary health form. AVMA website. 

atwork.avma.org/2018/03/02/avma-united-airlines-reach-agreement-on-veterinary-health-form/?utm_source=smartbrief&utm_medium=email&utm_campaign=smartbrief-assoc-news

. Updated March 8, 2018. Accessed June 19, 2018.

How do new airline regulations regarding the types of animals allowed to fly in cabins affect veterinary practitioners?

August 2018

Laser Therapy Today

MVC 2018: Advances in Feline Heart Disease Diagnosis

New Look, Same Great Content

Vision in Dogs and Cats

Animals and Airplanes: The Veterinarian's Role

ACVP 2017: Test-driving CARs to Treat Canine Lymphoma

A Picture Is Worth a Thousand Likes

Current Options for Managing Canine Osteoarthritis

Pay Your (Future) Self First

Getting Started With Telemedicine

NY Vet 2017: Osteoarthritis in Cats

Clinical Tidbits (August 2018)