While medical texts published more than five years ago are typically considered outdated, old and antiquated publications often hold valuable insights into the development of treatments and into the presentation of diseases. This is exactly what Samuel Friedrich Hahnemann, MD, had in mind when he began translating medical texts in the late 18th century. Dr. Hahnemann had denounced the medicine of his time as irrational.1 His sentiments were likely well-founded, as blood-letting and calomel were standard treatments for everything from the common cold to combat wounds. The yellow oxide form of mercury was a panacea for chronic eye conditions, and ocular injection of cobra venom was used to treat macular degeneration.2 Needless to say, these treatments worsened the conditions or expedited death more often than they cured.
Homeopathy—literally, "same suffering"—was Dr. Hahnemann's solution to these wayward medical practices. As a result of his research, he proposed that an illness could be treated with a substance that caused symptoms similar to the illness in a healthy person. Serial dilution removed the toxic effects of the substance, while the "essence" of the substance was retained by the diluent. Homeopathy blossomed in popularity because while its efficacy was comparable to bloodletting, homeopathy didn't cause further harm. Its popularity, however, was short-lived, as more scientific approaches to medicine became preferred.
For almost a century, homeopathy remained quiet, virtually forgotten by all except so-called "quack" doctors.3 In recent decades, however, homeopathy has seen a revival, becoming a multi-million dollar industry serving at least 6 million Americans.4,5 In our increasingly well-educated country where evidence of efficacy is expected, what is driving patients to trust in homeopathic remedies for ophthalmic conditions?
Homeopathic History
Today, quinine derivatives from cinchona bark are known to be a natural treatment for some forms of malaria, although fatal if taken in high doses.6 While translating documents involving its anti-malarial activity, Dr. Hahnemann decided to try the supposed-cure, and after repeatedly dosing himself, he experienced symptoms similar to malaria.7,8 This led him to theorize that if a substance given to a healthy person induced certain symptoms, it could be used to treat those same symptoms in an ill person. This idea is Dr. Hahnemann's "law of similars." He believed, however, that the concentrations that caused symptoms in a healthy person were too strong for treatment of an ill person. This consideration led to the minimum-dose principle, or "law of infinitesimals," which states that the therapeutic potency of a substance increases with more dilutions. In homeopathy, the most important part of the dilution process is a vigorous shaking of the solution after each dilution, so as to imprint the substance's nature on the water.9
The last principle Dr. Hahnemann proposed is that of holism, or the "single remedy," which is the belief that one remedy should be used to address all of the symptoms that a patient experiences. In consultation with a patient, the homeopathic practitioner aims to capture all aspects of physical and mental state, in order to best tailor the treatment to the individual. The remedy is chosen to address the total set of symptoms, instead of just those directly related to a disease.7 While classical homeopathy upholds the holistic, single-ingredient approach, modern homeopathy has adopted a broader definition, and some treatments do include a mixture of ingredients.
Modern Homeopathy
Today, homeopathy is categorized as a type of complementary and alternative medicine. It's often confused with the practice of herbalism, another form of
The conditions that homeopathy claims to treat range from cataracts to allergic conjunctivitis and, while not clinically proven, the treatments remain largely free of potential harm to patients. Cineraria maritima, derived from the tincture of the dusty miller plant, is purported to prevent or retard the formation of cataracts.11 One brand of homeopathic drops for cataracts contains active ingredients cineraria maritima 6X (denoting that the solution was diluted in a 1:10 ratio six times),7 conium maculatum 6X (from the poison hemlock plant) and phosphorus 12X.12
Other ophthalmological remedies include pulsatilla (from the wind flower) for "conjunctivitis with thick yellow discharge," and silica for blocked lacrimal ducts.2 One homeopathic dry-eye drop contains mercurius sublimatus 6X (mercuric chloride) indicated for dryness, belladonna 6X (from the deadly nightshade plant) for dryness and redness, and euphrasia 6X (from the eye-bright plant) for redness and inflammation.13
Proof of Efficacy
Throughout history, homeopathic remedies have been confronted by much skepticism and opposition from the scientific community. In one of his medical essays, the 19th-century physician Oliver Wendell Holmes made the following comment on Dr. Hahnemann's principles: "When one man claims to have established these three independent truths, which are about as remote from each other as the discovery of the law of gravitation, the invention of printing, and that of the mariner's compass, unless the facts in their favour are overwhelming and unanimous, the question naturally arises, is not this man deceiving himself, or trying to deceive others?"14 
Today, opponents of homeopathy argue that no matter how intensely the results of serial dilutions are agitated, there isn't any physical presence of the active ingredients if they are diluted to below Avogadro's number. Moreover, while there are published claims that the ultra-high dilutions of substances may involve phenomena at both the molecular level and in the structure of water, these results have not been consistently reproducible.15 Clinical trials to substantiate the efficacy of homeopathic remedies have been conducted, but the results are mixed.7
Some supporters of homeopathy insist that due to the nature of the remedies, efficacy should only be determined on the basis of patient satisfaction, rather than clinical trial results.1 A similar sentiment appears to be shared by the U.S. Food and Drug Administration, as efficacy trials aren't required prior to the sale of the highly diluted homeopathic remedies.9 Labels for homeopathic remedies sold over-the-counter only need to include an ingredients list, instructions for safe use, an indication for at least one self-limiting condition and the dilution strength. Those claiming to treat serious, non-self-limiting diseases (e.g., cancer) must be sold by prescription only, and must include a cautionary statement of the prescription status of the drug, a statement including recommended dosage and a package insert bearing the labeling information for the homeopathic practitioner.16
In contrast, for most conventional medications, especially prescription, proof of efficacy through clinical trial results is pivotal to FDA approval. In fact, the FDA relies on an entirely separate entity, the Homeopathic Pharmacopoeia Convention of the United States (HPCUS), to define and catalog the current homeopathic ingredients.16 To be accepted by the HPCUS, a substance must have either "homeopathic provings" or be known to induce symptoms that mimic the condition it's intended to treat. The substance must also be manufactured according to HPCUS criteria.17
Natural Fad or Telling Trend?
Despite the lack of active ingredients and of controlled clinical proof of efficacy, homeopathy is thriving. The rising popularity of homeopathy and other natural therapies has been suggested to correspond to the beginnings of the holistic health movement in the 1970s and the New Age movement of the 1980s.18 In a 1999 survey, more than 6 million Americans reported having used homeopathy in the past year,15 and an estimate of homeopathic drug sales in the United States in 2003 exceeded $300 million dollars.19 Proposed reasons for this choice include the natural ingredients, the holistic approach of a practitioner, who usually takes around twice as long as a conventional clinician to carefully tailor the treatment to the individual;20 and the lack of side effects due to the high dilutions.
Other factors may also influence patients' choice of homeopathic treatments. An Italian survey of 30,000 families revealed that 8.2 percent of the population had used homeopathy in 1999 and 2000. Within this population, the reported reasons for using homeopathic remedies were lower toxicity (71 percent), they were the only therapy available (22.6 percent), greater efficacy (20.5 percent), better doctor-patient interaction (13.2 percent), cultural belief (10 percent) and unknown (8 percent).21
In some instances, culture and homeopathy may be a marriage of convenience. For instance, homeopathy is booming in 
A distrust of corporate "Big Pharma"24 likely influences Americans' choices in health care today. The perception that pharmaceutical companies are primarily interested in profit, rather than consumer health, has only been fueled by recalls of products due to serious, yet unexpected, side effects. Perhaps the appeal of homeopathy's harmless nature, with the chance of efficacy, is enough to entice patients who feel unsettled by the ingredients and side effects of modern therapeutics.
Marketing Lingo
Even though homeopathic remedies appear to be cut from a different cloth than the drugs of major pharmaceutical companies, they are still sold by a for-profit industry. Direct-to-consumer prescription advertising, while regulated by the FDA, is controversial for both pharmaceuticals and alternative therapies. Since patients seldom seek medical advice before buying over-the-counter products, they are especially prone to often-misleading marketing jargon. For example, some advertisements for homeopathic remedies indicate "clinically proven" results alongside "homeopathic" in order to enhance the perceived credibility. Advertisements for a currently marketed zinc nasal gel for the treatment of common cold symptoms display the tag, "clinically proven to get you over your cold three times faster when taken at the first sign of a cold."25 It's easy to imagine how this statement can give the impression that the homeopathic remedy is three times better than conventional cold medications, even though the advertisement does not mention what the product's efficacy was actually compared to. The reference for this claim reveals that the study was actually performed versus placebo and is not, in fact, a measure of efficacy versus a conventional cold treatment.26 The same company claims, "No side effects. Just real relief," for its homeopathic nasal gel for nasal and ocular allergies. True to homeopathic principles, the active ingredients of the nasal gel include histaminum hydrochloricum 12X—a fancy name for a solution of the very molecule that elicits itching.
Natural Derivatives in Drugs
Perhaps what's often overlooked is the presence of natural ingredients in conventional therapies, although they're not usually known to elicit symptoms of the condition. One of the artificial tears available for the treatment of dry eye contains a derivative of the guar shrub as its gelling agent, HP-Guar, to approximate the glycocalyx, adhering the tear film to the epithelial cells. Cyclosporine A is a cyclic polypeptide produced by the fungus Beuveria nivea, and is known for anti-inflammatory properties.27
Several natural products, or derivatives thereof, have endured time and regulatory evaluations to remain present in modern medicines and are estimated to represent one-third of the top-selling drugs.28 While perhaps not conspicuously displayed on packaging or in advertisements, natural derivatives still constitute a fair portion of modern-day ophthalmic agents.
So, what is driving patients to homeopathic medicine? It seems that whatever the direct cause, our patients may not be so far off from what Dr. Hahnemann created at the core of homeopathy. Perhaps patients are uncomfortable with the potential side effects that are sometimes related to conventional medicine, and see a safer alternative in homeopathic remedies.
When consulting with patients who use, or who are interested in using, homeopathic or alternative choices for their ophthalmic conditions, it's important to emphasize the distinction between evidence-based therapeutics and homeopathic remedies. While conventional therapies may contain a higher toxicity, they are regulated by the FDA and are required to demonstrate proven safety and efficacy through controlled clinical trials. Furthermore, some even contain natural derivatives. Taking the time to actively listen to patients and then explain these facts could increase patient compliance and put patients at ease. When confronted with a patient who insists on taking homeopathic cataract eye drops, know that while they may not result in a miraculous recovery, they're very unlikely to worsen the condition.
Dr. Abelson, an associate clinical professor of ophthalmology at
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