Corneal reshaping is a rapidly progressing and increasingly popular modality worldwide and has demonstrated success in myopia reduction with patients as young as age 7.1-3

There have been some reports of adverse reactions in patients during corneal reshaping (see Corneal Reshaping and Microbial Keratitis, page 60).4-11 But, with careful patient education and compliance, these complications are avoidable.

Here, well look at some of the latest designs and fitting pearls for corneal reshaping and who the best candidates are for this modality.

Whos a Candidate?
Most patients with -4.50D or less myopia are suitable candidates for corneal reshaping. Patients often experience a myopic reduction of 1.00D to 2.00D the first night.12

Many O.D.s limit eligible patients to the non-presbyopia age group, although monovision corneal reshaping (i.e., undercorrecting one eye) is occasionally prescribed. Presbyopic corneal reshaping designs show promise, according to recent research.13

If youve just introduced corneal reshaping into your practice, you might want to start with the -1.00D to -2.00D myopic patient to gain confidence with this process. Also, start with young adults who are either non-contact lens or soft contact lens wearers and have no more than -1.50D of corneal cylinder (preferably not limbus-to-limbus). Corneal reshaping may result in a 50% reduction of central corneal toricity.14 Patients with against-the-rule or irregular astigmatism are not good candidates.15

You can prescreen potential patients by phone. When patients schedule an appointment, you (or your staff) can ask them about any known refractive error and current lens wear. Make sure that patients who are good candidates for corneal reshaping understand that this is a temporary process that requires retainer lens wear at night and compliance with the wearing schedule and care regimen.

Spherical gas permeable (GP) lens wearers must discontinue lens wear for at least four weeks before being fit with ortho-K lenses. Expect more lens exchanges and variable topography maps with these patients, even if they discontinue GP lens wear as recommended.16

Fitting and Follow-up
The lens designs we commonly use for ortho-K have at least four zones: the base curve; the secondary, or reverse, curve, which is often 3.00D to 5.00D steeper than the base curve; an intermediate alignment or fitting curve, which parallels the mid-peripheral cornea; and a peripheral curve radius, which is often slightly steeper than conventional designs, resulting in less peripheral clearance.17 The optical zone is often 6mm (it will be less in certain designs for higher refractive errors). Regardless of which design you select, fitting and follow-up care must be consistent.

Some designs use the Jessen factor, which is based simply upon lacrimal lens power changes. For example, if the patients spherical refractive error is -3.00D, you would select a base curve radius approximately 3.50D to 3.75D flatter than K to result in a refractive error of +0.50D to +0.75D. This is an ideal power to allow for regression of refractive error during the day. So, if the patient has keratometry readings (or simulated K values) of 43.75 @ 180 or 44.50 @ 090 and a prescription of -3.75 -0.75 x 180, you would use a base curve radius of 40.00D for +0.75D. A corneal topographer is important in the pre-fitting, fitting and follow-up of all corneal reshaping patients.

A bulls-eye lens-to-cornea fitting relationship with limited movement upon blinking and zones of less clearance and more clearance should be present (figure 1). Centration is extremely important, as a decentered lens will result in a decentered treatment zone and symptoms of glare, ghost images and variable vision.

1. The fluorescein pattern shows a bulls-eye lens-to-cornea fitting relationship.

Once you fit the lenses, have the patient return the next morning wearing the lenses so that you can assess the fitting relationship and, upon removal, corneal integrity. Coalesced central staining indicates excessive lens bearing.

Assess corneal topography, unaided vision and refractive error. The difference map should show a well-centered bulls-eye pattern (figure 2). If the topography is inconclusivethat is, not entirely the desired bulls-eye pattern but not excessively flat (smiley-face) or steep (central island)have the patient return three days after the initial fit to further assess the lenses. On average, it takes 10 days to achieve a stable endpoint.18

2. This representative difference map shows a well-centered bulls-eye pattern.
Courtesy: Precision Technology Services

Return visits at one week, two weeks, one month, three months and six months are recommended. Patients do not need to wear their lenses at these appointments. Check unaided visual acuity, refractive error, corneal integrity and topography at these visits. One-day disposable lenses, in gradually reduced minus powers, can be worn in the daytime during the treatment period. Some O.D.s allow patients to wear corneal reshaping lenses in the daytime during this period.

Corneal Reshaping and Microbial Keratitis
Recent reports of corneal ulcers among corneal reshaping patients have raised concerns worldwide about the safety of corneal reshaping, particularly in children.4-6 For example, one group of researchers found 50 cases of microbial keratitis (MK) among corneal reshaping patients worldwide; 40 of these cases, occurred in East Asia.7

The researchers suggest compliance problems as the main culprit. These include storage in saline solution, cleaning with tap water, limited patient education and follow-up care, and inappropriate wearing schedules. Patients who do not regularly replace their lens case or who fail to clean the case daily and disinfect it weekly are much more likely to have contamination of the case and lenses, often with the same organism for both.8 Inadequate fitting techniques (i.e., empirical fitting with no corneal topographer) and use of low Dk lens materials may also be responsible for the cases of MK, the researchers say.

Here are some ways to minimize the risk of adverse effects, including the the possible incidence of microbial infection:

Use a hyper-Dk ( 100) lens material. This is customary with the lenses used today in the United States.

 Use a corneal topographer. This is invaluable in patient selection, fitting and follow-up care. Corneal topography can determine a decentered corneal apex or the presence of subclinical keratoconus; both of these rule out corneal reshaping. Topography also can help you determine corneal eccentricity; studies have shown that the more corneal eccentricity present, the greater the potential myopia with corneal reshaping.9

 Instruct patients in lens insertion and removal. Make sure patients, especially pediatric patients, can handle the lenses. Use of a high-viscosity drop, such as Aquasite (Novartis) or Refresh Liquigel (Allergan) prior to inserting the lenses at night, can reduce corneal staining.10

Also, tell patients to wait at least 10 minutes upon awakening before removing their lenses, and to use a rewetting/lubricant agent before removal. Instruct the patient to physically manipulate the lower lid against the lens edge to break any adherent seal of the lens to the eye before removal.

 Teach proper lens hygiene. Advise patients to clean the lenses upon removal in the morning. Also instruct patients to clean the back
 surface of their lenses weekly by using a cotton swab soaked in cleaner with specific attention devoted to the reverse zone region.11 Do not allow patients to use tap water. Make sure they understand the importance of disinfection and compliance with the care regimen.

Give patients several lens cases, and tell them to replace these cases oftenmonthly if possible. Tell patients to clean the cases every night and disinfect them weekly.

 Instruct patients to discontinue lens wear and call your office if they experience sudden onset of discomfort or redness.

 Educate patients at every follow-up visit. Make sure they still use the recommended solutions, clean the lenses properly, and clean and replace lens cases often. Also, make sure that patients comply with the prescribed lens wearing schedule. E.S.B.


Lens Designs
The FDA has approved these lenses for corneal reshaping:

Paragon CRT (Paragon Vision Sciences). The CRT, which stands for Corneal Refractive Technology, was the first lens approved for overnight corneal reshaping. This lens consists of a 6mm central treatment zone, a 1mm wide return zone of variable depth, a tangent curve, a landing zone and an ellipse edge profile. Do not allow the terminology to confuse you, as this design is not complicated to fit. Laminated lens selection and problem-solving cards are available from Paragon.19

This design uses a diagnostic lens fitting approach. Paragon has a 100-lens CRT Diagnostic Dispensing System with a range of base curves, return zone depths and landing zone angles selected to result in the ability to dispense from inventory in the majority of cases.

BE Retainer (Precision Technology Services). The topography-based system uses eccentricity value, apical radius and horizontal visible iris diameter to determine the recommended lens design (figures 3 and 4). Any changes in lens design depend upon the resultant topography map (bulls-eye, smiley face or central island).

3. The topography software printout for the BE Retainer shows the recommended trial lens, taking apical radius, corneal eccentricity and effective sag into consideration.
Courtesy: Precision Technology Services

The BE Retainer system consists of a 25 retainer trial lens set and BE Studio software. The software assists in trial retainer determination, problem solving and custom retainer construction. It also predicts the amount of refractive change possible and potential treatment zone size (which decreases with increasing refractive error).

4. The BE Retainer lens is a topography-based system.
Courtesy: Bausch & Lomb

Contex OK E-System (Contex). You can order this multiple-zone design empirically by providing refractive and corneal shape information (central K and corneal eccentricity) or via diagnostic fitting (recommended). The optical zone most often is 6.0mm but can vary from 5.0mm to 8.0mm. The peripheral curve is aspheric (figure 5). The initial overall diameter is 10.6mm. A dispensing inventory set is available for diagnostic fitting. Lenses come in different eccentricity values to correspond with the specific corneal eccentricity value.

5. The Contex E-System lens design most often has an optical zone of 6.0mmbut it can vary from 5.0mm to 8.0mmand the peripheral curve is aspheric.
Courtesy: Bausch & Lomb

DreamLens (DreimLens). The DreamLens System integrates the DreamLens design (figure 6) and Procornea Eyelite software, which uses elevation data from the corneal topographer to assist in lens selection, ordering and problem-solving. Diagnostic fitting is not necessary with this four-zone reverse-geometry design.

6. The Dreamlens features a four-zone reverse geometry lens design.
Courtesy: Bausch & Lomb

Emerald (Euclid). The Emerald design (figure 7) is fit via the use of an empirical fitting philosophy. Accurate keratometric and spectacle refraction measurements as well as horizontal visible iris diameter are the only requirements for the initial lens selection. The standard overall diameters are 10.2mm, 10.6mm and 11.0mm with a standard power of +0.75D with this four-zone lens design.

7. The Emerald lens design features four zones and a standard power of +0.75D.
Courtesy: Bausch & Lomb

The lens you use depends upon the fitting method you desire, your desired fabricating laboratory and the software you plan to use during the process. You must be certified to fit specific designs such as the Paragon CRT. The BE Retainer, Contex OK E-System, DreamLens and Emerald designs fall under the Bausch & Lomb Vision Shaping Treatment (VST) umbrella. You must be certified by Bausch & Lomb to fit these designs and be certified for any one or more of these designs. You can accomplish this online.

Corneal Reshaping Lens Designs/Certification
Bausch & Lomb Vision Shaping Treatment: www.bausch.com/us/ resource/visioncare/vst/index.jsp
BE Retainer (Precision Technology Services): www.beretainer.com
Contex OK E-System (Contex): www.oklens.com
DreamLens (DreimLens Inc.) www.dreimlens.com
Emerald (Euclid Systems Corp.): www.euclidsys.com
Paragon CRT (Paragon Vision Sciences): www.paragoncrt.com

Corneal reshaping is a safe, temporary alternative to refractive surgery for low to moderate myopia. Careful patient screening and selection and use of a corneal topographer is important with this modality. Patients need to be educated on the importance of proper care and compliance and be evaluated on a regular basis. With the increasing popularity of these designs among young people, as well as an increasing number of design options, the future looks very bright for this potentially life-changing modality.

Dr. Bennett is executive director of the Gas Permeable Lens Institute and is co-chief of the contact lens service and director of student services at University of Missouri-St. Louis College of Optometry.

1. Walline JJ, Rah M, Jones LA. The Childrens Overnight Orthokeratology Investigation (COOKI) pilot study. Optom Vis Sci 2004 Jun;81(6):407-13.
2. Reim TR, Lund M, Wu R. Orthokeratology and adolescent myopia control. Contact Lens Spectrum 2003;18(3):40-42.
3. Cho P, Cheung SW, Edwards M. The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control. Curr Eye Res 2005 Jan;30(1):71-80.
4. Young AL, Leung AT, Cheng LL, et al. Orthokeratology lens-related corneal ulcers in children: a case series. Ophthalmology 2004 Mar;111(3):590-5.
5. Hutchinson K, Apel A. Infectious keratitis in orthokeratology. Clin Exp Ophthalmol 2002 Feb;30(1):49-51.
6. Wilhelmus KR. Acanthamoeba keratitis during orthokeratology. Cornea. 2005 Oct;24(7):864-6.
7. Swarbrick H, Watt K. Microbial keratitis in orthokeratology: The worldwide perspective. Presentation at the 2005 Global Orthokeratology Symposium, Chicago, July 2005.
8. Cho P. Microbial flora of tears of ortho-k patients and microbial contamination of contact lenses and contact lens accessories. Presentation at the 2004 Global Orthokeratology Symposium, Toronto, July 2004.
9. Mountford J. An analysis of the changes in corneal shape and refractive error induced by accelerated orthokeratology.  Int Contact Lens Clin 1997;24:128-143.
10. Herzberg CM. Improved efficacy of eye gel lubricants vs. rewetting drops in Ortho-k. Presentation at the 2005 Global Orthokeratology Symposium, Chicago, July 2005.
11. Rah M. Personal communication. July 2005.
12. Sridharan R. Response and regression of the cornea with short-term orthokeratology lens wear. Masters thesis, University of New South Wales, Sydney, Australia, 2001.
13. Legerton J. Corneal Refractive Therapy for hyperopia and presbyopia. Presented at the Global Orthokeratology Symposium, Toronto, July 2004.
14. Mountford J. Advanced orthokeratology: Part 2: Patient selection and trial fitting. Optician 2002;224(5867):26-37.
15. Rinehart JM, Bennett ES. Orthokeratology. In Bennett ES, Hom MM. Gas Permeable Contact Lenses (2nd ed.), St. Louis, MO, Elsevier, 2004:424-483.
16. Subramaniam SV, Bennett ES, Morgan B, Lakshrimnarayanan V. Comparison of overnight orthokeratology in RGP and non-RGP wearers. ARVO Abstract #3713, 2003.
17. Bausch & Lomb. A Guide to Overnight Orthokeratology, www.bausch.com/us/resource/ visioncare/orthok/guide_to_orthok.pdf. Accessed August 2005.
18. Alharbi A, Swarbrick HA. The effects of overnight orthokeratology lens wear on corneal thickness. Invest Ophthalmol Vis Sci 2003 Jun;44(6):2518-23.
19. McCampbell K, Bennett ES, Rah M. Corneal reshaping made easy with the CRT lens. Contact Lens Spectrum 2004;19(10):30-37.

Vol. No: 142:10Issue: 10/15/2005