Archive for January, 2011

Epithelial Basement Membrane Dystrophy (EBMD)

Friday, January 21st, 2011

Dr Raymond Stein of the Bochner Eye Institute wrote the following clinical update. We hope you find it of interest.

EBMD is a common hereditary corneal dystrophy that may result in recurrent corneal erosions and/or blurred vision. Clinical epithelial signs include fingerprint lines, map-like changes, or microcysts. If the corneal signs are subtle it is valuable to instill fluorescein and view with a Cobalt-blue light. With EBMD the epithelium is irregular and the tear breakup will be abnormal.

If patients have recurrent erosions and they are refractory to hypertonic solutions (Muro 128 5% drops and/or ointment) then a keratectomy can be performed. This procedure involves debridement of the corneal epithelium and polishing of Bowman’s layer with a diamond burr. Eighty-five percent of eyes with this technique will have resolution of their erosions. The procedure can be repeated if necessary.

If patients have glare, halos, or reduced vision secondary to EBMD then a keratectomy can be performed. The epithelium that grows back is usually smoother resulting in an improvement in vision. It usually takes 4 to 6 weeks for the best vision to be achieved.

Computerized Topography to Rule-Out Keratoconus Prior to LASIK

Friday, January 21st, 2011

Dr Raymond Stein of the Bochner Eye Institute wrote the following clinical update. We hope you find it of interest.

Keratoconus is a well-recognized contraindication to LASIK. The creation of a corneal flap and removal of tissue by an excimer laser can weaken a cornea making it structurally compromised. This can lead to corneal instability with progressive ectasia characterized by steepening and thinning. Although there are a variety of clinical signs of keratoconus the use of computerized topography and pachymetry usually allows for the detection of the earliest stages of keratoconus. The most advanced topography units measure both curvature, elevation, and pachymetry. The Pentacam is our unit of choice at Bochner.

We typically make the diagnosis of keratoconus when one or more findings are present:

1. Inferior steepening of greater than 1.5 Diopters compared to superior cornea.

2. Elevation of the posterior cornea of greater than 17 microns compared to a best-fit sphere.

3. Elevation of the anterior cornea of greater than 21 microns compared to a best-fit sphere.

4. Central steepening of greater than 49 Diopters.

5. Steepest corneal location associated with thinning of less than 500 microns.

6. Advanced clinical signs include corneal iron deposition at the base of the cone, Vogt’s striae or stress lines, and apical scarring.

In addition to the clinical findings above we are reluctant to perform LASIK if there is an immediate family history of keratoconus.

Careful preoperative evaluation prior to laser vision correction can greatly reduce the risk of corneal ectasia.

Phakic Implants for High Refractive Errors

Friday, January 21st, 2011

Dr Raymond Stein of the Bochner Eye Institute wrote the following clinical update. We hope you find it of interest.

Phakic implants are used in vision correction for high refractive errors that cannot be treated by laser vision correction. Over the past 13 years we have been inserting the Implantable Contact Lens (ICL), a posterior chamber phakic implant made by Starr Surgical. Clinical outcomes for high myopia and astigmatism have generally been excellent with 95% of eyes achieving 20/30 or better uncorrected vision. The main indications are refractive errors that are too high for laser vision correction. In general patients are candidates for a phakic implant if they have myopia greater than 10 D or hyperopia greater than 5 D.  Astigmatism can be treated up to 6 D. Patients must have a satisfactory depth of the anterior chamber (distance between the corneal endothelium and the crystalline lens) of greater or equal to 2.8 mm. Most of the high myopes will qualify unlike the high hyperopes. Patients should also have a pupil size of 7 mm or less.

Another surgical option, which patients need to know about in the informed consent, is a refractive lens exchange. Our preference is not to perform a lens exchange for high myopia because of the increased risk of retinal tears and detachment.  This is not the case with the treatment of high hyperopia, which is associated with a minimal retinal risk.

In patients that are good candidates for the ICL, a refraction is performed, the limbal white-to-white distance is measured to determine the length of the implant, and two small YAG laser iridotomies are performed to reduce the risk of elevated intraocular pressure from papillary block. The implant is custom ordered from Switzerland.

The surgical procedure is relatively easy for patients.  At the Bochner Eye Institute we perform this procedure in our sterile operating room approved by the Ontario College of Physicians and Surgeons. Under topical anesthesia a 2.8 mm limbal incision is constructed. Intraocular xylcaine is injected to numb the contents of the eye. After the implant has been carefully folded into a cartridge it is injected into the anterior chamber where it gradually unfolds. Using a specialized instrument the haptics are gently placed behind the iris. Miochol is then injected to constrict the pupil.  Intraocular Vancomycin is injected to prevent infection. The patient is then checked one hour postoperatively to be sure the intraocular pressure is normal. Follow-up examinations are usually 1 day, 1 week, 1 month, and 3 months.

Complications are rare. The main risk is inducing a cataract (1%). If patients are not satisfied with their level of uncorrected vision then laser vision correction can be performed. We have not had a case of infection over the past 13 years.

Specialized indications for the ICL include patients with keratoconus and those following radial keratotomy. In keratoconus patients if they have satisfactory best-corrected spectacle acuity (20/40 or better) then consideration can be given to the ICL. Patients may require an Intracorneal ring to reduce the degree of irregular astigmatism prior to a phakic implant. In the situation following radial keratotomy if patients have developed a hyperopic shift then this can be corrected by the ICL. Unlike a natural hyperope the post-RK eyes were previously myopic and usually have a satisfactory anterior chamber depth.

Update on Corneal Collagen Crosslinking (CXL) for Keratoconus

Friday, January 21st, 2011

The surgeons of the Bochner Eye Institute wrote the following clinical update. We hope you find it of interest.

At the Bochner Eye Institute we were the first in North America to introduce CXL using Riboflavin drops and epithelial removal in January 2008. Over the past 3 years we have treated over 2,000 keratoconic eyes with encouraging clinical results. Based on patient treatments we are now considered the most experienced centre for CXL worldwide.

As you may know, the main goal of CXL is to halt the progression of keratoconus and prevent the need for a corneal transplant. At the Bochner Institute patients have ranged in age from 10 to 60 years. The earlier the treatment the better the long-term prognosis. We have not seen a case of progressive ectasia post-CXL. A minimum corneal thickness of 400 microns is required prior to CXL. In corneas between 300 and 399 microns, we have been successful in inducing transient corneal swelling with hypotonic drops to achieve a minimum thickness over 400 microns to safely perform the UV-A laser application.

Dr Raymond Stein was recently invited to present our CXL outcomes at the American Academy of Ophthalmology in Chicago in October 2010. This is the largest ophthalmic meeting in the world with an attendance of over 20,000. The 24-month outcomes were reported that were followed with a refraction, pachymetry, and Pentacam analysis. Some patients achieved up to 8 diopters of flattening, although the average central flattening was one diopter. Topographic difference maps often showed flattening of steep areas and steepening of flat areas to enhance the overall corneal curvature and improve best-corrected spectacle acuity.  During the first month postoperatively the uncorrected visual acuity and best-corrected visual acuity is often decreased as the epithelium undergoes remodeling or maturation. At 4 to 6 months postoperatively, 60% of eyes showed an improvement of one or more lines of vision.

In Europe, which started CXL 12 years ago, the procedure is now being rapidly adopted as the standard of care for keratoconus eyes with progressive disease. Long-term data from Europe has shown a primary success rate of 98% in halting disease progression in corneas with an initial steepness of less than 58 D. If there is progressive steepening the procedure can be repeated with good results.

At the Bochner Eye Institute we continue to treat patients from as far away as Miami, Dallas, and Los Angeles. We have treated a few NHL hockey players as well as children of ophthalmologists and optometrists. This breakthrough technology is showing significant clinical benefits.

More about Clinic Director Raymond Stein MD

Femtosecond Laser for Creation of LASIK Flap

Friday, January 21st, 2011

Dr Raymond Stein of the Bochner Eye Institute wrote the following clinical update. We hope you find it of interest.

Many reports have demonstrated the superiority of Femtosecond laser created flaps over a microkeratome blade: increased flap thickness accuracy,1,2,3 greater consistency of flap thickness,4,5 the elimination of buttonhole flaps,1,6 decreased epithelial injury,4, 7,  greater flap adhesion strength, 8 ,faster visual recovery and better uncorrected visual acuity,8,9 improved contrast sensitivity,10 better refractive astigmatic neutrality,5 decreased higher order aberrations,11 and decreased corneal insensitivity and tear function compromises.12,13

The laser flap has a uniform or planar thickness. A blade creates a meniscus flap which results in a thinner flap in the centre and thicker in the periphery. This can lead to one of the most dreaded LASIK complications of a button-hole. This can result in loss of best-corrected vision from irregular astigmatism or scar tissue. When we acquired a Femtosecond laser 4 years ago we thought initially we would offer both the Femtosecond and blade technologies. After doing our first cases we quickly sold our microkeratome. All prospective laser patients should be aware that the Femtosecond laser provides the most technologically advanced and safest procedure.

Why would some laser centres today offer inferior technology? The answer is very clear – cost. The purchase of a Femtosecond laser costs around $500,000, there is an annual maintenance fee of around $70,000, and a disposable cost (suction ring) of approximately $200 per eye. A microkeratome can be purchased for $25,000 or less, there are no annual maintenance fees, and the cost of a blade is around $50 for both eyes. So you can see from a cost point of view there are significant savings to a laser centre to offer inferior technology with a microkeratome.

Femtosecond technology continues to advance. At the Bochner Eye Institute we acquired the first IFS laser in Canada, which has a speed of 150 KHz. This is 2.5 times faster than the previous laser technology. This results in the suction ring being on the eye for less time resulting in a more comfortable experience for the patient. In addition the new technology can create a flap edge greater than 100 degrees. This leads to a more stable flap position like a man-hole cover, and a lower incidence of epithelial ingrowth.

At the Bochner Eye Institute we continue to treat a significant number of eye-care professionals from across Canada and the United States. We feel this is because eye doctors understand leading edge technology and trust our surgical techniques and abilities.

1.Binder PS. Flap dimensions created with the Intralase FS Laser. J Cataract Refract Surg. 2004;30:26-32.

2. Javaloy J, Vidal MT, Abdelrahman AM, Artola A, Alio JL. Confocal microscopy comparison of Intralase femtosecond laser and Moria M2 microkeratome in LASIK. J Cataract Refract Surg. 2007; 23:178-187.

3. Patel SV, Maguire LJ, McLaren W, Hodge DO, Bourne WM. Femtosecond laser versus mechanical microkeratome for LASIK: a randomized controlled study. Am J Ophthalmol. 2007;114:1482-1490.

4. Kezirian GM, Stonecipher KG. Comparison of the Intralase femtosecond laser and mechanical keratomes for laser in situ keratomileusis. J Cataract Refract Surg. 2004;30:804-811.

5. Talamo JH, Meltzer J, Gardner J. Reproducibility of flap thickness with Intralase FS and Moria LSK-1 and M2 microkeratomes. J Cataract Refract Surg. 2006;22:556-561.

6. Binder PS. One thousand consecutive IntraLase laser in situ keratomileusis flaps. J Cataract Refract Surg. 2006;32:962-969.

7. Duffey RJ. Thin flap laser in situ keratomileusis: flap dimensions with the Moria LSK-One manual microkeratome using the 100-micron head. J Cataract Refract Surg. 2005;31:1159-1162.

8. Knorz MC, Vossmerbaeumer U. Comparison of flap adhesion strength using the Amadeus microkeratome and the IntraLase IFS femtosecond laser in rabbits. J Refract Surg. 2008;24:875-878.

9. Durrie DS, Kezirian GM. Femtosecond laser versus mechanical keratome flaps in wavefront-guided laser in situ keratomileusis: a prospective contralateral eye study. J Cataract Refract Surg. 2005;31:120-126.

10. Tanna M, Schallhorn SC, Hettinger KA. Femtosecond laser versus mechanical microkeratome: a retrospective comparison of visual outcomes at 3 months. J Refract Surg. 2009;25:S668-S671.

11.Montes-Mico R, Rodriguez-Galietero A, Alio JL. Femtosecond laser versus mechanical keratome LASIK for myopia. Ophthalmology. 2007;114:62-68.

12. Tran DB, Sarayba MA, Bor Z, Garufis G, et al. Randomized prospective clinical study comparing induced aberrations with IntraLase and Hansatome flap creation in fellow eyes. J Cataract Refract Surg. 2005;31:97-105.

13. Lim T, Yang S, Kim MJ, Tchah H. Comparison of the IntraLase femtosecond laser and mechanical microkeratome for laser in situ keratomileusis. Am J Ophthalmol. 2006;141:833-839.

14. Barequet IS, Hirsh A, Levinger S. Effect of thin femtosecond LASIK flaps on corneal sensitivity and tear function. J Refract Surg. 2008;24:897-902.