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CASE REPORT
Recurrent corneal erosions associated with granular dystrophy led to surface irregularity and loss of best corrected acuity for this patient. Therapeutic and refractive laser
techniques restored his vision. by John W. Parks, O.D. and Jeff Machat, M.D., Chatham, Ontario A 52-year-old white male police officer was referred to our office by his doctor for assessment of his granular stromal dystrophy.
He was first diagnosed at age 30, following the onset of several corneal epithelial erosions. The patient complained of regular erosions, problems with glare and poor vision with his glasses. The patient had no systemic disorders,
but had several family members with granular dystrophy. External examination revealed a moderate
grade corneal granular stromal dystrophy. The granules were classical in clinical appearance, central and predominantly anterior and mid-stromal. Fundus examination was normal.
We agreed with the diagnosis of corneal granular dystrophy and suggested phototherapeutic keratectomy (PTK) to reduce or possibly eliminate the recurrent corneal erosions. Secondary goals were to improve best-corrected visual acuity and reduce the patient's degree of hyperopia, which we would do by combining hyperopic photorefractive keratectomy (PRK) with the PTK.
Treatment and Follow-up The treatment protocol involved performing the surgery with a transepithelial approach, utilizing the epithelium as a masking agent to reduce corneal irregularities. The surgeon performed a 6mm PTK epithelial ablation, blended out to 9mm, with the intention of leaving a smoother anterior surface after the laser procedure. This would not have been achievable if the epithelium had been removed manually. The second step involved a refractive PRK ablation to reduce the hyperopia. The final steps involved further blending PTK, titrated to create a smoother anterior curvature.
One month follow-up revealed a small reduction of granular deposits, but a smoother epithelial contour. Uncorrected visual acuity was 20/25 O.S. Best-corrected visual acuity was +225/-100 x 002 = 20/20 O.S. The patient has reported no epithelial erosions since the surgery, and has been pleased with the improved unaided and best-corrected visual acuity. There is a possibility of recurrence of the granular deposits in the future, but the likelihood and onset of this are not known. Discussion Clinically, granular corneal dystrophy presents as white snowflake flecks and clumps, which typically remain in the central cornea and spare the area within 2-3mm of the limbus. Symptomatic patients with granular corneal dystrophy will typically complain of loss of best-corrected acuity, problems with glare and recurrent corneal erosions.2 Most patients with granular corneal dystrophy require little treatment beyond genetic counseling, optimal refractions and management of the occasional corneal erosion. However, in patients with compromised visual acuity or chronic recurrent epithelial erosions, treatment is indicated. In the past, the treatment of choice for granular dystrophy was penetrating keratoplasty or sometimes superficial keratectomy. However, the granular deposits are known to recur in the transplant tissue over time.1-4 The excimer laser is known to be safe and effective for the removal and treatment of corneal scars due to trauma and infectious keratitis, as well as treating some corneal dystrophies.3-7 In this case, PTK proved to be a safe and effective treatment for granular corneal dystrophy and should be the preferred treatment of choice over penetrating keratoplasty. The latter is a much more invasive procedure, carries the risk of graft rejection and offers very little control over the refractive outcome. The most important aspect of the treatment is to appreciate that the granular deposits reduce the best-corrected visual acuity because of the associated irregular astigmatism. So, the goal of the treatment is not to eliminate the deposits but simply to create a smoother anterior contour. In the past, excimer laser PTK in these cases removed in excess of 100µ of central corneal tissue in a 5-6mm zone and induced several diopters of hyperopic refractive error. The utilization of a flying spot delivery system allows for a 9mm blend zone, reducing any induced hyperopia. In this patient, we achieved our goals of eliminating the frequent corneal erosions and improving best-corrected acuity without inducing the large hyperopic shifts of older PTK techniques.
Dr. Parks is affiliated with TLC, The Laser Center, in Windsor, Ontario. Dr. Machat is the national medical director for TLC. 1. Ruusvaara P, Setala K, Tarkkanen A. Granular corneal dystrophy with early stromal manifestation.
Acta Ophthalmologica 1990;68(5):525-31. |
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Diagnostic Data
Note the pre-operative corneal deposits (top) and the reduction after surgery. 
The objective of the PTK was not to eliminate
the granular deposits, but rather reduce the associated irregularity. The surgeon used methylcellulose 1 percent as a masking agent, and performed several 10µ PTK ablations successively, examining the patient at the slit
lamp every 10-20µ. Once the surgeon achieved an adequately smooth anterior surface, he stopped the procedure despite the persistence of granular deposits in the deeper stroma. The large taper prevents any induced epithelial
hyperplasia and subsequent hyperopic regression.
Topography (pre-op, above) demonstrates the reduction in irregular astigmatism.