Download Document 2042715

Keratoconus Overview
Diagnosis and Management
Keratoconus Definition and Diagnosis
Keratoconus is a non-inflammatory, progressive ectasia of the cornea. It is characterized by
progressive thinning and steepening of the central cornea into a cone-like shape. As the cornea
steepens and thins, the patient experiences a decrease in vision, which can be mild or severe
depending on the degree to which corneal tissue is affected. 1
Onset of keratoconus occurs during the teenage years--mean age of onset is age 16 years – but
onset has been reported to occur at ages as young as 6 years. Keratoconus rarely develops after
age 30 years. Keratoconus shows no gender predilection and is bilateral in over 90% of cases. In
general, the disease develops asymmetrically: diagnosis of the disease in the second eye lags
about five years after diagnosis in the first. The disease process is active for about five to 10
years, and then it may be stable for many years. During the active stage, change may be rapid.
Typically, vision loss can be corrected early by spectacles or soft contact lenses; later, due to the
abnormal shape of the cornea and the onset of increased myopia and irregular astigmatism, rigid
(hard) contact lenses are required for optical correction and functional vision. Contact lenses
provide a uniform refracting surface to improve the patient’s vision, while at the same time they
work to support the bulging cornea. Contact lenses can improve vision, but be uncomfortable to
wear for extended periods – sometimes beyond just a few hours a day. Further, they are believed
to contribute and exacerbate corneal scarring, which may be a manifestation of the disease.
Patients typically are informed upon diagnosis that they would likely require contact lenses
eventually. Although most patients can continue to read and drive, some feel quality of life is
adversely affected. Patients undergo eye examinations annually or more frequently to monitor
progression. About 20% of patients will eventually need a corneal transplant. 2
Keratoconus has no known cure, and many people do not even know they have it because it
begins as nearsightedness (myopia) and astigmatism. It is a progressive disorder that may
advance rapidly or sometimes take years to develop. It can severely affect the way we see the
world, including simple tasks such as driving, watching TV, or just reading a book. Some
keratoconus patients have described their vision as being “blind with light.”
Etiology3
The proposed etiology of keratoconus includes biochemical and physical corneal tissue changes,
but no one theory fully explains the clinical findings and associated ocular and non-ocular
disorders. It is possible that keratoconus is an end result or final common pathway of many
different clinical conditions. It has been found in association with hereditary predisposition, atopic
disease, certain systemic disorders, and long-term rigid contact lens wear.
Diagnosis
“INTACS Inserts for Treating Keratoconus: One Year Results,” Ophthalmology 2001. Joseph Colin, MD;
Beatrice Cochener, MD; Gwenaelle Savary, Orthoptist; Florence Malet, MD; Debby Holmes-Higgin,
MS, MPH.
2
“Keratoconus.” Surv. Ophthalmol. 1998 42:297-319. Rabinowitz, YS, MD.
3
“Keratoconus.” Surv. Ophthalmol. 1998 42:297-319. Rabinowitz, YS, MD.
1
Addition Technology, Inc.
Page 1 of 6
Last Reviewed 5/3/2017
Identifying moderate or advanced keratoconus is fairly easy. However, diagnosing keratoconus in
its early stages is more difficult, requiring a thorough case history, a search for visual and
refractive clues and the use of diagnostic equipment. Often, keratoconus patients have had
several spectacle prescriptions in a short period, and none has provided satisfactory vision
correction. Figure 1 depicts the keratoconic cornea.
Figure 1
Normal keratoscopy
Early keratoconus
Moderate keratoconus
Keratoconus can result in extremely complex and variable topographical maps, most typically
showing areas of inferior steepening. The cone can assume various shapes and sizes, and the
apex can be at various locations in relation to the central cornea.
Classification
Keratoconus can be classified4 by cone shape, central keratometric reading, or progression. The
simplest classification systems are based on keratometric reading or shape:
Based on severity of curvature

Mild <48 D in both meridians

Moderate 45-53 D in both meridians

Advanced >53 D in both meridians

Severe >55 D in both meridians
Based on shape of cone
4

Small diameter (5 mm.); round shape; easiest to fit with contact lenses

Large oval diameter (>5 mm.); often displaced inferiorly; more difficult to fit with lenses

Largest diameter (>6 mm.); 75% of cornea affected; most difficult to fit with lenses
“Live-epikeratophakia for Keratoconus,” Journal of Cataract and Refractive Surgery. 1998 Krumeich, JH; Knulle, DJ.
Addition Technology, Inc.
Page 2 of 6
Last Reviewed 5/3/2017
Current Treatment Alternatives5
Referral criteria
While 80% to 85% of patients with keratoconus can be managed with spectacles, soft and rigid
contact lenses to correct for visual acuity and astigmatism, in 15% to 20% of the keratoconic
population, a corneal transplant is eventually required 6.
The patient should be referred for transplant if any of the following generally accepted referral
criteria are met:
1) Contact lens intolerance especially with recurrent abrasions;
2) Inability to fit the patient with a contact lens (including frequent lens loss);
3) Decreased vision (generally from scarring) which prevents the patient from doing necessary
visual tasks;
4) Large cone with progressive thinning in the periphery ; and
5) The danger of perforation, though rare in keratoconus.
Surgical Treatment
Various types of surgery are available for the patient with keratoconus who has progressed
beyond correction with rigid contact lenses. Penetrating keratoplasty is the most common. In this
procedure, the keratoconic cornea is prepared by removing the central area of the cornea, and a
full-thickness corneal button is sutured in its place. An alternative is lamellar keratoplasty, a
partial corneal transplant; it should be noted that this alternative is used in less than 5% of cases.
The cornea is removed to the depth of posterior stroma, and the donor button is sutured in place.
This technique is technically difficult, and visual acuity is inferior to that obtained after penetrating
keratoplasty. Its disadvantages include vascularization and haziness of the graft.
Clinical Challenges of Current Surgical Treatment
The eye-care practitioner must decide when to recommend keratoplasty for the keratoconic
patient. This is often not a simple, straightforward decision. Keratoplasty for keratoconus is highly
successful; however, there is a long recovery period and a risk of severe ocular complications. A
number of factors must be considered in deciding when to do a keratoplasty. One of the most
important factors is the patient's functional vision. If the best acuity with their contact lenses
prevents them from doing their job or carrying out their normal activities, or when the contact
lenses cannot be worn more than a few hours a day, a transplant must be considered. The actual
measured visual acuity may be quite different for different patients. One patient may find that
he/she cannot do their job with 20/30 acuity while another patient may be very satisfied with
20/60 acuity.
Very careful contact lens fittings are necessary before recommending a corneal transplant. Prior
to transplant every effort should be made to optimally fit the patient with contact lenses, especially
if there is not significant corneal scarring affecting vision.
However, a minority of patients becomes intolerant to contact lenses, and requires a transplant
earlier than otherwise would be necessary. If the patient has a large area of thinning, a very
decentered cone or significant blood vessel growth into the usually clear cornea, called
“The Success of Penetrating Keratoplasty for keratoconus.” Eye. 1990. Kirkness, CM; Ficker, LA; et al.
6 “Keratoconus.” Surv. Ophthalmol. 1998 42:297-319. Rabinowitz, YS, MD.
5
Addition Technology, Inc.
Page 3 of 6
Last Reviewed 5/3/2017
neovascularization, a transplant may be performed earlier than otherwise indicated by the visual
performance, as these factors may require a larger than normal transplant button size and/or
increase the chance of rejection if allowed to advance too far.
The healing process following transplant is long, often taking a year or longer. The time from
surgery to the removal of the stitches is commonly 6 to 17 months. The patient may be on
steroids for months. Initially following surgery the donor button is swollen and even following
healing the button is usually thicker than the corneal bed in which it rests.
Large amounts of astigmatism are common following keratoplasty. One such study found an
average of 5.56 diopters of correction (DC) with a range from 0 to 17 diopters following suture
removal7. The patient's spectacle prescription may fluctuate for some months following surgery.
Refractive changes and keratometry or corneal topography can be used to follow the healing
process.
Graft rejection reactions occur in 18% to 20% of the patients 8,9. Signs of graft rejection include
ciliary flush, anterior chamber flare, keratic precipitates, Khodaoust line and Krachmer's spots.
Signs of graft rejection are reported to occur from 1 month to 5 years following surgery. The
rejection rate for bilateral grafts is higher than if only one eye is grafted. In the bilateral cases,
when a rejection reaction occurs it is commonly in both eyes. If the second eye is to be grafted,
there is usually a period of at least a year between grafts. If signs of rejection occur, aggressive
treatment with steroids is begun. Usually the reaction is overcome and the graft remains clear. A
high percentage of the corneal grafts are successful. However, visual rehabilitation is slow, and
keratoconus may recur 15-20 years later in the corneal transplant. As significant, and of
particular concern to younger patients, it is commonly understood and addressed in peerreviewed literature that corneal grafts have a limited life, and that subsequent attempts to graft
are less successful than the first.
Surgical Treatment of Keratoconus with Intrastromal Corneal Ring Segments (INTACS)
INTACS have been in use by corneal surgeons in clinical practice for more than five years in the US
on an off-label basis and as many as seven years by Surgeons in Europe. Ophthalmologists have
been using INTACS more than eight years in the treatment of myopia. The technical procedure,
including incision and tunneling, is well documented and has been associated with significant
clinical success.
Procedure
The placement and dimensions of the INTACS implants help to reshape the cornea to its original,
natural shape, thereby normalizing the cornea’s architecture and adjusting for the myopia and
irregular astigmatism caused by keratoconus.
Using proprietary surgical instruments, a small 1.2-millimeter incision is made in the cornea at
70% depth and tunnels are created for the insertion of the INTACS. The INTACS are then
delicately threaded into the tunnels, and the incision is closed using a 10 0 suture. The patient’s
refraction is checked and follow-up appointments are scheduled for the next day, at seven days
and one month. The patient is advised to avoid eye rubbing and strenuous physical activity for
about a month. The suture is removed after 30 days.
“The Success of Penetrating Keratoplasty for keratoconus.” Eye. 1990. Kirkness, CM; Ficker, LA; et al.
“Penetrating Keratoplasty for Keratoconus.” Cornea, 2000. Brierly, SC, MD; Izquierdo, L, MD; Mannis, MJ, MD.
9
“Indications for and Outcomes of Penetrating Keratoplasty Performed by Resident Surgeons,” American Journal of
Ophthalmology, July 2003. Randleman, JB, MD; Song, CD, MD: Palay, DA, MD.
7
8
Addition Technology, Inc.
Page 4 of 6
Last Reviewed 5/3/2017
INTACS Intrastromal corneal ring
segments. Photo provided by the
manufacturer.
Outcomes
In most cases, the patients’ uncorrected visual acuity and best-corrected visual acuity show
marked improvements.10 A high percentage of these patients were candidates for an imminent
transplant. The reshaped cornea, after the INTACS procedure, is typically aided by the use of
glasses or soft contact lenses in order to provide improved functional vision to the patient and
reduce the eye irritation previously experienced with the RGP contact lenses.
Studies have shown that INTACS placements can restore functional vision by allowing most
patients to be effectively corrected with contact lenses or glasses, if needed. Specifically, Boxer
Wachler, et. al. found that (1) the mean improvement was 4 lines UCVA and 2 lines BCVA, (2)
those with less than two lines of improvement in BSCVA still improved UCVA by 2 lines or better
in 60 percent of cases, (3) irregular astigmatism was reduced across the board, and (4) the
number of lines of correction ranged from up to ten lines BSVCA and from counting fingers
UCVA. These results were replicated by Colin, et. al., whose prospective study of 10 patients
found that both BCVA and UCVA improved in more than 50% of those patients.
Both researchers concluded that use of INTACS in patients with keratoconus is an
effective way to manage the condition and restore functional acuity to patients. Boxer
Wachler goes farther, to say, “INTACS is to be a logical addition to the stepwise treatment
of keratoconus that improves visual acuity and, in a number of patients, has negated the
need for corneal transplantation, thus far.”
“INTACS for Keratoconus,” Ophthalmology. May 2003. Brian S. Boxer Wachler, MD; Naveen S. Chandra, MD; Brian
Chou, OD; Tommy S. Korn, MD; Richard Nepomuceno, JD; Jonathan P. Christie, OD.
10
Addition Technology, Inc.
Page 5 of 6
Last Reviewed 5/3/2017
PEER REVIEWED STUDIES OF INTACS FOR KERATOCONUS
“Changes in Keratoconic Corneas After Intracorneal Ring Segment Explantation and
Reimplantation,” Ophthalmology, 2004;111:747-751. Jorge L. Alio, MD, PhD; Alberto Artola,
MD, PhD; et. al.
“INTACS for Keratoconus,” Ophthalmology. 2003; 110:1031-1040. Brian S. Boxer Wachler,
MD; Naveen S. Chandra, MD; Brian Chou, OD; Tommy S. Korn, MD; Richard Nepomuceno, MD;
Jonathan P. Christie, OD.
“Utilization of Refractive Surgery Technology in Keratoconus and Corneal Transplants.”
Current Opinion in Ophthalmology, 2002; 13:230-234. Joseph Colin, MD; Sylvie Velou, MD.
“Current Surgical Options for Keratoconus,” Journal of Cataract and Refractive Surgery,
2003;29:379-386.Joseph Colin, MD; Sylvie Velou, MD.
“Management of Keratoconus with INTACS,” American Journal of Ophthalmology,
2003;135:64-70. Charalambos Siganos, MD, PhD; George Kymionis, MD, PhD; Nikos Kartakis,
MD; Michalis Theodorakis, BSc; Nikos Astyrakakis, OD; Ioannis Pallikaris, MD, PhD.
“INTACS Inserts for Treating Keratoconus: One Year Results,” Ophthalmology, 2001;108:1409-1414.
Joseph Colin, MD; Beatrice Cochener, MD; Gwenaelle Savary, Orthoptist; Florence Malet, MD; Debby
Holmes-Higgin, MS, MPH.
“Correcting Keratoconus with Intracorneal Rings,” Journal of Cataract and Refractive Surgery,
2000: Joseph Colin, MD; Beatrice Cochener, MD; Gwenaelle Savary, Orthoptist; Florence Malet,
MD.
Addition Technology, Inc.
Page 6 of 6
Last Reviewed 5/3/2017