CLEK Study CLEK - The Collaborative Longitudinal Evaluation of KC Sought to describe the clinical course of KC Sought to identify both risk & protective factors The study concluded after nearly 10 years, with data collected from 1,209 patients CLEK Findings: KC is not as strongly associated as once believed with CT diseases (DS, Marfan, Ehlers-Danlos) 50% of patients reported rubbing their eyes vigorously 53% of patients reported a history of atopy Patients who present with KC earlier in life tend to progress more rapidly, although progression generally slows by the fourth decades.
CLEK Study CLEK Findings: 74% of patients in CLEK were corrected with contact lenses 73% of those contact lens patients said their lenses were comfortable Twice risk of K scarring in KC patients who wear CLs vs. those who do not KC causes a slow, consistent, yet mild decrease in both high-and-low contrast corrected VA Patients worse than 20/40 vision report a worse quality of life than expected
KC Etiology KC etiology remains obscure...possible theories: Inheritance suspected to be a major cause KC accelerate the process of keratocyte apoptosis- programmed cell death following injury Minor external traumas (eye rubbing, poor CL fit & ocular allergies) Can release cytokines from the epithelium that stimualte keratocyte apoptosis Genetic mutations lead to oxidative damage = KC Common belief- KC has a low-grade inflammatory component
Classification of KC Stages of KC Forme Fuste (Early or incomplete KC) Detectable but often missed Modest KC Eyes begin to require GPs for optimal visual correction Advanced KC Fleisher ring, vogt’s striae, corneal scarring, hydrops Poor vision with spectacle correction Severe KV Surgical treatments should be considered
Intacs for KC Intacs Corneal Implants Intrastromal rings that flatten the central cornea by shortening the arc length of the anterior corneal surface Intacs provide biomechanical support, flattening & regularization of the K Intacs --) peripheral support --) flattening of cone --) reduces irregular astigmatism Popularity: potentially reversible treatment for KC Especially for those who are contact lens intolerant & who want to delay or eliminate the need for PK
Goals of Intacs for KC When Intacs are used as treatment for KC, the surgeon’s goals are three-fold To improve visual acuity with & without spectacles Defer corneal transplantation Long-term effects on KC progression post Intacs implantation are unknown Create a cornea more receptive to contact lenses To regularize the corneal contour enough so that patients can once again wear contacts or spectacles
Intacs Candidates Low to moderate KC K readings over 60D don’t do as well as lower ones- Less than 60D in steep K reading K cannot be flattened more than 10D; sometimes can flatten only 5-6D Clear corneas- no scarring! 450 microns of tissue in corneal periphery Corneal apex at least 350 microns thick Very thin corneas, less than 200um, don’t do well No previous surgery Ideal candidate is someone who’s actually not an a PK candidate Patients with central, visually significant scars or excessive thinning in the mid-periphery S&S of CL intolerance Subjective or mechanical irritation from GP lenses
Intacs Outcome 5 years studies show that: Intacs are relatively safe Significant refractive error may remain Up to 10% of KC eyes managed with Intacs may require adjustment surgery LASEK, SCL & scleral CLs
Intacs Outcome Researchers have demonstrated the following results from Intacs implantation: BCVA: 45% gained >2 lines UCVA: 72% gained >2 lines Mean BCVA: 20/50 pre-op to 20/32 post-op Mean UCVA: 20/200 pre-op to 20/80 post-op Statistically significant change in mean keratometry values 50.86D pre-op to 47.63D post-op No statistically significant change in astigmatism; 3.33D pre-op to 3.06D post-op
Intacs Outcome Success with intacs for KC is defined differently than it is with LASIK for myopia KC patients are often happy to be able to wear CLs or specs, even if their vision isn’t perfect Most patient require glasses or CLs postop BCVA improves! Some can go without specs/CLs for more of their daily life
Intacs Complications 5 years studies show that: Migration of the segments Extrusion of the segments- if eye rubbing involved Halos Glare Ring exposure due to K thinning Stromal thinning & K melting If rings planted too superficially Blepharitis Vascularization in 5% Lack of effect in 2-3% of patients
Technique Lack of large-scale, well controlled studies on Intacs for KC Difficult to dictate the definitive method of performing the procedure Surgeons approach the procedure in different ways Techniques used: Placing the entry incision on the cornea’s steep axis Mismatch segment sizes 0.2mm; 0.21mm; 0.3mm; 0.35mm; 0.4mm; 0.45mm For example: A cone located inferiorly with the K’s steep axis on Horizontal plane The incision will be on the horizontal axis One thinner segment will be placed under the cone and a thicker one opposite the cone- done to pull up the opposite center and move the optical center This approach yields better results & fewer optical aberrations
Technique Techniques used: Some surgeons prefer to place the entry incision on the cornea’s flat axis So many mismatching techniques No one really knows at this point if there is a significance difference between the various techniques Not enough data out there! A lot of variability in these corneas that it’s difficult to ascertain what the best methodology is No matter what technique is used, by supporting the mid-periphery the intacs will tend to centralize the cone In essence the intacs are going around the entire cornea, so you have a new limbus
Advantages of Intacs They are additive, removable, and replaceable Reposition the cone & allow a large, clear optic zone Less invasive Shorter recovery period Easier than PK or DALK 10-minute procedure Minimal risk of infection Short duration of procedure + small incision site K topography improves the next day Better results when combined with corneal cross-linking Good option in cases of progressive Keratoconus
Intacs F/U Fitting & F/U for intacs patients: Practitioners should wait at least 3 months post implantation for vision to stablize before attempting to fit a patient with contact lenses In fact, one study reported visual acuity, refraction & topography were not stable until 9 months post-op At F/U always monitor for surgical complications Chronic FBS Halos Channel deposits Wound site vascularization
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