The patient is examined after the laser treatment and if a substantial haze remains, then additional pulses using a PTK technique are cautiously applied to reduce residual haze. Finally, in cases of haze that recur after the two treatments discussed, I will again perform re-treatment, but this time using mitomycin 0. In such a case, the transepithelial approach is similarly used.
A mitomycin pledget is used I use a 4. It is positioned directly over the area of haze and applied for 2 minutes. Care is taken to avoid excess mitomycin leaking over the remainder of the cornea. After removal of the pledget, the surface of the cornea is vigorously irrigated with balanced salt solution. Using this technique, I have not yet seen haze recur.
However, overcorrection can be a problem and can be avoided by being conservative in laser application. Indeed, some investigators have advocated mechanical stripping of any plaque-like haze with the subsequent use of mitomycin, without laser ablation. They suggest that simply removing the fibrous plaque mechanically will reduce the refractive error and mitomycin will prevent recurrence.
Donald G. Utilize the epithelium treatment in the pull down menu. This is performed in a dark room with the microscope light using ring light only low enough to visualize the natural epithelial and haze fluorescence. It will always give a central smooth removal. Removing a diameter of 4 mm to 5 mm is sufficient to include all the important haze. It is not necessary to see fluorescence disappearance out to 6. In the rare case where there is still a mild layer of haze centrally, a couple of repeated 0.
These are done in the Contoured Ablation Pattern method in the pull down menu with the Ablation Profile Adjustment turned off. Over 10 years and 45, cases in some of the earlier cases, this technique produced significant haze problems , there have been only four eyes that have had the haze return significantly. I have recently re-treated these eyes by removing the haze with the same technique and applying mitomycin C immediately.
Naturally, the best treatment for haze is prevention. With our present primary treatment, even a grade 1 haze has less than a 0. Olivia N. My preferred regimen consists of aggressive topical administration of corticosteroids and lubricating drops. If the haze decreases and best corrected visual acuity improves but more corticosteroid therapy is required, I continue with fluorometholone 0.
If corticosteroid therapy combined with lubrication is inadequate and haze and undercorrection with decreased visual acuity persist, I treat with a combination of PTK and PRK with postoperative mitomycin topical application. One of the first to suggest this therapy was Till Ancheutz, MD, of Gaggenau, Germany, who demonstrated in experimental studies in animals decreased fibroblast proliferation on confocal microscopic examination after treatment with mitomycin. Ancheutz and then Percy Amoils, MD, of Johannesburg, South Africa, demonstrated the clinical efficacy of mitomycin in reducing new collagen production and haze after re-treatments.
In-cornea scars. The refraction through these scars is real and reflected in topography, so proceeding with Lazrplastique in a refractive mode can take these patients straight to emmetropia without spectacles or contact lenses, according to Dr. Figure 5. On-cornea scars. The refraction through these scars is misleading, as is the topography clown-suit or camouflaged. According to Dr. Figure 6. Gulani, even extreme scarring, such as after radial keratotomy using multiple incisions, can be corrected refractively with Lazrplastique, and improved corneal clarity is an additional benefit.
Thickness measurements with Scheimpflug-based tomography may be underestimates. Anterior segment OCT is more accurate in eyes similar to this one. Usual epithelial irregular hypertrophy OCT epithelial thickness map would be addressed with phototherapeutic keratectomy with one caveat: A hyperopic shift may occur that will necessitate a second hyperopic PRK procedure in the future.
In my opinion, situations like this one highlight the potential risks of surface ablation, and these should be discussed with patients in advance. A similar case of mine involved a year-old woman who underwent PRK for the correction of about I routinely instruct patients to administer steroid drops for 2 months after PRK, but this patient developed an intolerance. She might also have been poorly compliant with instructions to wear UV protection.
I instruct patients to wear close-fitting sunglasses and a hat outdoors, even when skies are cloudy, and to administer an oral 1,mg vitamin C supplement daily for 2 months.
Eventually she developed reticular haze that was resistant to topical steroid therapy administered for 6 months. The data and treatment outcome are shown in Figure 7.
Figure 7. Preoperative analysis with the Pentacam underestimates corneal thickness. Three-step treatment middle row. The haze shown in Figure 1 is likely to be grade 2 or 3 rather than 3 or 4. If it is of recent origin, conservative treatment with topical steroids should be initiated along with the aggressive treatment of DED. Haze removal, correction of the small residual refractive error, and regularization of the corneal optics would be the aim of treatment.
Transepithelial topography-guided ablation would consist of two parts. The lamellar portion removes the epithelium and some protruding stroma if the surface is irregular. The laser is normally programmed so that the ablation reaches the thickest point of the epithelium, as measured by OCT.
The refractive part consists of regularizing and reshaping the stroma to treat the higher- and lower-order aberrations, respectively. The depth of treatment is decided by the ablation software, according to imported topography and refractive error measurements. To treat the haze, the maximum depth of the haze rather than the maximum depth of the epithelium is used to program the lamellar part.
A precise corneal OCT—derived haze thickness map is required. A future gene therapy may transiently express components--such as nidogen-1 and nidogen-2, perlecan, or laminin alpha which would be provided by keratocytes to regenerate the basement membrane, he predicted. This article was adapted from a presentation presented at the Refractive Surgery Subpecialty Day during the American Academy of Ophthalmology meeting. March 15, Reviewed by Steven E. Wilson, MD Defective regeneration of the epithelial basement accounts for most late haze following injury to the epithelium and anterior stroma, according to Steven E.
Wilson said. Growth factor influence Defects in the epithelial basement membrane allow two epithelium-derived growth factors, TGF-beta and PDGF, to penetrate the stroma and drive the development of myofibroblasts. Mytomycin C can prevent haze after PRK by inhibiting proliferation of myofibroblast precursors. Steven E.
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