The disorder now known as keratoconus has fascinated and perplexed clinicians for more than three centuries. Recognized as early as the 1700s, its pathophysiology remains both curious and frustrating, and, during the last century, its clinical management has considerably changed, improving the lives of afflicted patients. Keratoconus is a disease that can be managed in many ways, ranging from optical correction to a variety of surgical interventions, and it is, at the same time, a disorder whose core etiology continues to elude us. Even today, with the tools of molecular genetics that have pinpointed single nucleotides as the source of many disorders—several of which are associated with keratoconus—the disorder cannot be traced to a consistent, single genetic abnormality and is considered to be both genetic and environmental in origin.
In the Beginning: 17th and 18th Centuries
The first mention of what is identifiable as keratoconus is from the records of Benedict Duddell (c. 1696–1760). Duddell, practicing in Nottingham, England, went to Paris to study with the famous English oculist, John Thomas Woolhouse (1660–1734) and subsequently returned to England where he practiced in Hammersmith, near London. Among the treatises that he wrote between 1729 and 1736, he described corneal anatomy in detail. In his 1736 treatise, Duddell described the case of a young boy with prominent cone-shaped corneas ( Fig. 1.1 ). The findings were also in the context of albinism and nystagmus, and, although not identified specifically as keratoconus, this is likely the first description of the disorder. ,
The flamboyant and opportunistic itinerant oculist, Chevalier John Taylor (1708–1772), who despite his education and prominence is largely regarded as a quack, has been the subject of many descriptions that point both to his erudition and to his blatant dishonesty and charlatanism. Taylor served as oculist to King George II of England as well as to other European royal families. Whatever is said about his honesty, it is likely that Taylor was an astute observer. In 1766 he wrote a description of a condition he called “ochlodes” and described it as a conical deformation of the cornea with a blunted apex with the base of the cone equal to the diameter of the cornea. His description is consistent with advanced keratoconus.
Burkhard David Mauchart (1696–1751) was appointed court physician in Tübingen (1723) and was professor at the university after completing his education in Tübingen, Paris, and Strasbourg. He described what he termed “cornea diaphanum,” which may have been an early description of keratoconus, differentiating this from other forms of staphylomatous corneal protrusion, although current evidence suggests that he could not be credited with the early description of keratoconus. ,
The 19th Century: The Age of Description
NEW OBSERVATIONS
The first half of the 19th century witnessed newer descriptions of conical cornea. Case histories of patients with what appeared to be a conical cornea were documented by Antonio Scarpa (1801), James Wardrop (1808), Pierre Demours (1818), and R. Lyall (1789-1831), who presented four cases of “staphyloma pellucidum conicum” to the Edinburgh Medical and Surgical Society.
Interestingly, Sir William Adams (1817) reported surgical procedures rendering aphakic two patients with conical cornea. The resulting improvement in vision suggested that the hyperopic shift from cataract extraction in these patients represented a surgical treatment for the myopia induced by the conical cornea.
William McKenzie (1761–1868) described conical cornea in his Practical Treatise on the Diseases of the Eye (1830). McKenzie served as the Surgeon Oculist to Queen Victoria and was founder of the Glasgow Eye Infirmary. His descriptions of the cornea in this condition included a corneal apex that could be eccentric, apical opacification in some cases, and the progressive myopic shift that occurs with progression of the disease. He accurately pointed out that the disease typically had its onset in puberty and was often asymmetrical. He did not associate the disease with inflammation, pain, or elevation in intraocular pressure. Essentially his description of keratoconus was much as we describe it today.
The frustration with keratoconus as an entity difficult to manage is described best by JH Pickford (1844) when he wrote: “There is no disease to which the eye is subject, hitherto so rebellious to medicine, so intractable in its nature, and, at the same time, so fatal to vision, as conical cornea; and not one, the pathology and treatment of which are so little understood.” This discouraging statement can be understood in an era decades before contact lenses and a century before keratoplasty would be available to these patients. This pessimism is also reflected in the work of von Ammon, who provided detailed descriptions of keratoconus and concluded that the prognosis for treatment was very poor. The first use of the term “keratoconus” was by von Ammon in 1828.
THE WORK OF JOHN NOTTINGHAM
Although there were several descriptions of what was surely keratoconus over the preceding 50 years, it was the extensive treatise by John Nottingham (1854) that collected the accounts of keratoconus and its consequences and merged them into a comprehensive description of the disease. Nottingham (1810–1895) studied medicine in London and Paris and practiced in Liverpool, UK where he was a surgeon at Southern Hospital.
He based his work on the collective descriptions of predecessors including, among others, Scarpa, von Ammon, von Carion, McKenzie, along with his own clinical observations of the disease. In his monumental 270-page treatise entitled Practical Observations on Conical Cornea and on the Short Sight and Other Defects of Vision Connected With It , Nottingham described the epidemiology and clinical presentation of the disease, and contemporary treatments ( Fig. 1.2 ).
In his treatise, Nottingham described keratoconus as a relatively rare disorder with a predilection for Asian races. His clinical description included apical thinning and protrusion of the cornea, and he described corneal hydrops with loss of transparency and edema. As is the case in contemporary ophthalmology, Nottingham could not identify a singular cause for the disease but rather suggested the possibility of an inherited component in addition to the influence of environmental exogenous factors, including inflammation, alternations in nutrition, and anomalies of the nervous system, among others.
With regard to treatment, Nottingham suggested three general approaches: (1) Optical management (including biconcave lenses, Galilean telescopes, pinhole goggles, and contact lenses “in concept”); (2) Medical management (systemic administration of zinc sulfate, arsenic, myrrh, and others, as well as topical nitric oxide of mercury); and (3) Surgical management (including anterior chamber paracentesis, pupilloplasty to form an eccentric pupil, and excision of the corneal apex), although he recommended surgery only after all other treatments were undertaken.
Remarkably, Nottingham’s extensive treatise described keratoconus much as we do today, with the difference being our repertoire of effective optical and surgical treatments of the disease.
Late 19th and Early 20th Centuries: The Period of Emerging Therapies
As the disease became better characterized, clinicians began turning their attention to more effective therapies: medical, optical, and surgical.
MEDICAL THERAPY
Of the approaches to medical therapy employed in the 19th century, few had any significant rationale or effectiveness and bear the least emphasis in our discussion. These included, among others, the use of emetics, purgatives, systemic calomel for fluid absorption, iodine collyrium, zinc sulfate, silver or iodine ointment applied to the lids, prolonged patching with miotics, and leeches applied to the lower lid or temple. Several devices were also employed to exert extended pressure on the corneas in an attempt to effect flattening of the anterior curvature. Needless to say, none of these remedies had a significant positive impact on the course of the disease.
OPTICAL THERAPY
Optical treatments employed included concave lenses, spherocylindrical spectacles, stenopaic slits, blocking lenses, pinhole glasses, Raehlman hyperbolic lenses (1878), and the hydrodiascope (1892).
Concave lenses were recommended early on by McKenzie and were likely useful for the progressive myopia experienced by keratoconic patients but became less effective with the progression of the disease. Raehlman (1879) developed hyperbolic lenses, which were designed to optically neutralize the progressively astigmatic corneas of the patient. These lenses were custom made for each patient and had the significant limitation that when the patient looked through any but the central portion of the lens, the effect was negated.
Another optical device peculiar to keratoconus and what may seem today as a bizarre solution to the problem was the hydrodiascope, introduced in 1896. Designed as a goggle that was filled with fluid and worn over one eye, the device was originally described and was able to improve visual acuity to a normal level by neutralization of irregular astigmatism and spectacle magnification. Its principal disadvantage was its poor cosmetic appearance and the high demand that it placed on accommodation. With the advent of contact lenses, the hydrodiascope fell into disuse ( Fig. 1.3 ).
