Corneal Dystrophies

W. Lisch, B. Seitz, F. Bandello

• Publisher: S. Karger
• Year: 2011
• Print ISBN:
  9783805597203
• eBook ISBN:
  9783805597210
• Topic: Medicine
• Subtopic: Genetics in Medicine

Corneal dystrophies (CD) are bilateral hereditary disorders of the cornea in which one or several parts of the cornea lose their transparency. As the dystrophy can start in different layers of the cornea, they are classified accordingly as epithelial dystrophies, stromal dystrophies and endothelial dystrophies. This volume includes a description of the new international IC3D classification of CD reflecting what we currently know of the clinical, pathological, and genetic aspects of these disorders. Further contributions give an insight into differential diagnostics and histology, which can confirm the diagnosis as for instance in granular CD type 2, as well as DNA analysis of CD providing additional information about the pathogenesis. Also, procedures such as the phototherapeutic keratectomy with the excimer laser, the new modalities of lamellar keratoplasty, and penetrating keratoplasty are described. This publication holds a wealth of new and topical information on CD for ophthalmologists and geneticists alike.

Lisch W, Seitz B (eds): Corneal Dystrophies.
Dev Ophthalmol. Basel, Karger, 2011, vol 48, pp 116-153

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Stage-Related Therapy of Corneal Dystrophies

Berthold Seitz^a · Walter Lisch^b

^aDepartment of Ophthalmology, University of Saarland, Homburg/Saar, and ^bDepartment of Ophthalmology, City Hospital of Hanau, Hanau, Germany

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Abstract

Corneal dystrophies typically result in a gradual bilateral loss of vision in a primary ‘white eye’- often in conjunction with epithelial defects in later stages. Treatment of corneal dystrophies needs to be stage-related. To ensure a stage-related therapeutic approach, an adequate classification based on clinical, histopathological and genetic knowledge is indispensable. In principle, topical medications, contact lenses and various microsurgical approaches are applicable. In case of predominantly superficial dystrophies of the epithelium, basal membrane and/or Bowman's layer (map-dot-fingerprint, Meesmann, Lisch, Reis-Bücklers,Thiel-Behnke), recurrent epithelial defects may complicate the clinical picture. If conservative therapy with gels/ointments, application of therapeutic contact lenses and/or conventional corneal abrasion are not successful, phototherapeutic keratectomy (PTK) using a 193-nm excimer laser is the method of choice today. PTK can be repeated several times, thus postponing corneal transplantation (lamellar or even penetrating) for a long time.Three major goals may be achieved by PTK depending on the diagnosis: (1) to remove superficial opacities; (2) to regularize the surface and treat irregular astigmatism, and (3) to improve the adherence of the epithelium. In dystrophies with depositions predominantly in the stroma (e.g. granular, lattice, macular, recurrence on the graft), PTK may be a reasonable alternative to anterior lamellar or penetrating keratoplasty (PKP) depending on the exact localization of the lesions. Besides exact determination of the depth of depositions using a slit lamp, a preoperative topography analysis is indispensable. The therapy of endothelial dystrophies depends on diagnosis and age: Fuchs endothelial corneal dystrophy will need corneal transplantation (e.g. when visual acuity drops below 0.4). In contrast, transplantation will only be very rarely necessary in posterior polymorphous corneal dystrophy, but the intraocular pressure has to be checked frequently. Especially in elderly patients with reduced compliance, posterior lamellar keratoplasty - preferably in the form of Descemet stripping automated endothelial keratoplasty- may be performed instead of PKP. In case of congenital hereditary endothelial dystrophy, the best time point of PKP has to be determined with regard to amblyopia (surgery too late) and inadequate follow-up (surgery too early) together with parents and pediatric ophthalmologists on an individual basis. In conclusion, for stage-related therapy of corneal dystrophies, besides contact lenses, PTK and PKP, various techniques of lamellar keratoplasties represent an indispensable enrichment of our corneal microsurgical spectrum today.

Copyright © 2011 S. Karger AG, Basel

Corneal dystrophies typically result in a gradual bilateral loss of vision in a primary ‘white eye’ - often in conjunction with epithelial defects in later stages. Treatment of corneal dystrophies needs to be stage-related. To ensure a stage-related therapeutic approach, an adequate classification based on clinical, histopathological and genetic knowledge is indispensable. In principle, topical medications, contact lenses and microsurgical interventions are applicable.

Over the past decades, there has been a shift in treatment of these conditions from corneal transplantation (penetrating keratoplasty - PKP) to excimer laser-assisted keratectomy, typically referred to today as phototherapeutic keratectomy (PTK), for visual restoration. PTK using the 193-nm excimer laser can produce significant visual improvement in these patients, and corneal transplantation or repeat transplantation can be delayed or even avoided. In addition, lamellar keratoplasty techniques [anterior lamellar keratoplasty (ALKP) and posterior lamellar keratoplasty (PLKP)] are widely discussed today.

Phototherapeutic Keratectomy Using an Excimer Laser

In case of predominantly superficial dystrophies of the epithelium, basal membrane and/or Bowman's layer (map-dot-fingerprint, Meesmann, Lisch, Reis-Bücklers, Thiel-Behnke), recurrent epithelial defects may complicate the clinical picture. If conservative therapy with gels/ointments, application of therapeutic contact lenses and/or conventional corneal abrasion are not successful, PTK using a 193-nm excimer laser is the method of choice today [1]. PTK can be repeated several times, thus postponing corneal transplantation (lamellar or even penetrating) for a long time. Three major goals may be achieved by PTK depending on the diagnosis: (1) to remove superficial opacities; (2) to regularize the surface and treat irregular astigmatism, and (3) to improve the adherence of the epithelium. These three goals may apply to variable degrees in a given pathology (fig. 1) [2].

In dystrophies with depositions predominantly in the stroma (e.g. granular, lattice, macular, recurrence on the graft), PTK may be a reasonable alternative to anterior lamellar keratoplasty or PKP depending on the exact localization of the lesions. Besides exact determination of the depth of depositions using a slit lamp, a preoperative topography analysis is indispensable. In principle, prominent lesions have a good, whereas localized lesions with stromal thinning have a limited prognosis.

Patient Counseling

The efficacy of PTK seems to be related to several factors, including (1) the nature of the corneal disorder; (2) the patient's subjective complaints; (3) the preoperative refractive error; (4) the treatment strategy, and (5) the tissue ablation properties of the laser. Careful attention should be directed toward the specific patient complaints to better determine if PTK may be expected to achieve the desired clinical goals. Certainly, the patient should be completely informed about the diverse surgical steps. Especially, characteristic phenomena referred to as ‘sight’, ‘sound’ and ‘smell’ have to be discussed with each patient in advance to avoid unexpected reactions intraoperatively.

Fig. 1. Indications for PTK: (1) corneal opacity (o-PTK); (2) irregular corneal surface and astigmatism (a-PTK),and (3) epithelial nonadherence (e-PTK). Such indications may overlap in a number of corneal disease processes and may apply to variable degrees in a given pathology (modified after Hersh and Wagoner [2]).

Corneal Clarity

A crystal-clear cornea is typically not the goal of a PTK for superficial corneal dystrophies. The goal is to postpone or even avoid lamellar keratoplasty or PKP. Often removal of major central opacities leads to a considerable increase in visual acuity [3]. Typically some deposits are left in the midstroma (e.g. in granular dystrophy) without major disadvantages. The dystrophy may recur early after PTK, especially in macular dystrophy [4, 5] and Reis-Bücklers dystrophy [6, 7]. In contrast, map-dot-fingerprint dystrophy [8] and granular dystrophy [9, 10] will recur later. In case of recurrence of the dystrophy, repeat PTK or PKP/ALKP may be necessary [11, 12].

Visual Acuity and Refraction

Depending on the preoperative refraction, PTK may lead to an increased best-corrected visual acuity (BCVA), despite a decrease in the uncorrected visual acuity (UCVA). This may be due to a hyperopic shift after central PTK. A BCVA of 1.0 (20/20) is not the goal. Often the patient is highly satisfied when the visual acuity increases from 0.2-0.3 to 0.6-0.8. In some cases, even a hard contact lens may be necessary to achieve good vision. The patient must be aware of this potential problem in advance and should not be confronted with this issue for the first time after PTK in case a major hyperopic shift has occurred.

Recurrent Corneal Erosion Syndrome

Corneal dystrophies (especially epithelial basement membrane dystrophy - EBMD) are often associated with recurrent corneal erosion syndrome (RCES) [13]. Conservative treatment in case of RCES may include (1) gels and ointments; (2) lubricants (to be applied especially early in the morning and late at night); (3) nonpreserved artificial tears in severe cases; (4) autologous serum [14]; (5) therapeutic contact lenses, or (6) collagen shields.

Surgical alternatives include (1) abrasion and thorough removal of the basal membrane with a hockey knife, with or without (2) anterior stromal puncture [15]. Anterior stromal puncture should not be performed in the central optical zone to avoid glare, halos and visual impairment postoperatively. After PTK, the success rate is not 100% but somewhere between 85 and 90% [16, 17]. Artificial tears and/or gels are still necessary after PTK. Especially if PTK in corneal dystrophy is performed predominantly because of the pain caused by RCES, the patient must be aware of the potential loss of UCVA after PTK.

Diagnostic Approaches for Surgical Decision Making

Microsurgeons should realize that PTK is not the treatment of choice for all anterior corneal pathologies. ‘Aiming and shooting’ at all corneal pathologies should be avoided to prevent dissatisfaction and frustration. The primary diagnosis does not necessarily dictate the treatment of choice, since various clinical presentations of the same d...

Table of contents

• Cover Page
• Front Matter
• IC3D Classification of Corneal Dystrophies
• The Clinical Landmarks of Corneal Dystrophies
• Histological Landmarks in Corneal Dystrophy: Pathology of Corneal Dystrophies
• The Genetics of the Corneal Dystrophies
• Differential Diagnosis of Schnyder Corneal Dystrophy
• Clinical and Basic Aspects of Gelatinous Drop-Like Corneal Dystrophy
• Stage-Related Therapy of Corneal Dystrophies
• Author Index
• Subject Index