Femtosecond laser in refractive corneal surgery.

The introduction of the femtosecond (fs) laser has revolutionized ophthalmic surgery. With the worldwide application of fs-lasers, clinical outcomes and safety in corneal procedures have improved significantly and they have become an ideal tool for ultra-precise corneal refractive surgery. Flap creation in laser in situ keratomileusis (LASIK) is the most common use of this laser. It can also be used for other corneal refractive procedures including channel creation for the insertion of intrastromal corneal ring segments (ICRS), performing astigmatic keratotomies (AK), femtosecond lenticule extraction including small incision lenticule extraction (SMILE), and the insertion of corneal inlays. This article summarizes recent advanced applications of fs laser technology in corneal refractive surgery.

Genetics in Keratoconus - What is New?

BACKGROUND: Keratoconus is characterized as a bilateral, progressive, non-inflammatory thinning of the cornea resulting in blurred vision due to irregular astigmatism. Keratoconus has a multifactorial etiology, with multiple genetic and environmental components contributing to the disease pathophysiology. Several genomic loci and genes have been identified that highlight the complex molecular etiology of this disease. CONCLUSION: The review focuses on current knowledge of these genetic risk factors associated with keratoconus.

Visual, aberrometric, photic phenomena, and patient satisfaction after myopic wavefront-guided LASIK using a high-resolution aberrometer.

PURPOSE: The purpose of this study was to evaluate the visual, refractive, and aberrometric outcomes as well as the level of patient satisfaction and photic phenomena after myopic laser in situ keratomileusis (LASIK) surgery using wavefront-guided (WFG) ablations based on measurements obtained with a high-resolution aberrometer. PATIENTS AND METHODS: This study was a prospective analysis including 253 eyes of 127 patients (aged between 19 years and 54 years) undergoing WFG LASIK using the STAR S4 IR Excimer Laser System combined with the iDesign System and iFS Femtosecond Laser. Visual, refractive, and aberrometric outcomes during a 2-month follow-up as well as patient satisfaction and photic phenomena were evaluated by means of a questionnaire. RESULTS: A total of 85% (215/253) and 99% (251/253) of eyes achieved a postoperative (Postop) uncorrected distance visual acuity of 20/16 and 20/20, respectively, and all eyes achieved an uncorrected distance visual acuity of 20/25. Postop spherical equivalent values were within ±0.25 D and ±0.50 D in 97% and 100% of eyes, respectively. Likewise, manifest cylinder was <0.25 D in 97% (245/253) of eyes. A statistically significant reduction was found in the total root mean square (P<0.001) and in the level of primary spherical aberration (P=0.001). Postop difficulties related to vision were graded as minimal, with low levels of photic phenomena and high levels of patient satisfaction. The level of difficulty to perform daily activities and the level of glare perceived by patients while driving car were significantly decreased (P<0.001). CONCLUSION: WFG LASIK surgery using the technology evaluated is predictable and effective for the correction of myopia and leads to high levels of patient satisfaction.

Comparison of short-term refractive surgery outcomes after wavefront-guided versus non-wavefront-guided LASIK.

PURPOSE: To evaluate and compare visual and refractive outcomes after laser-assisted in situ keratomileusis (LASIK) surgery for the correction of myopia or myopic astigmatism using 3 different treatment protocols. METHODS: We included 736 eyes of 369 patients (age 18-62 years) divided into 3 groups: 235 eyes of 118 patients (MEL80 group) undergoing LASIK using optimized aspheric ablation profiles (MEL80 excimer laser; Carl Zeiss Meditec), 248 eyes of 124 patients (Wavescan group) undergoing wavefront-guided (WFG) LASIK (STAR S4IR excimer laser + Wavescan aberrometer; Abbott Medical Optics), and 253 eyes of 127 patients (iDesign group) undergoing WFG LASIK (STAR S4IR excimer laser + iDesign system; Abbott Medical Optics). Visual and refractive outcomes were evaluated 2 months after surgery. RESULTS: A total of 91% (215/235), 95% (237/248), and 99% (251/253) of eyes achieved a postoperative uncorrected distance visual acuity of 0.0 logMAR (≈20/20) in the MEL80, Wavescan, and iDesign groups, respectively. Postoperative spherical equivalent (SE) was within ±0.5 D in 95% (223/235), 98% (242/248), and 100% (253/253) of eyes in these same 3 groups, respectively. Likewise, manifest cylinder was below 0.50 D in 95% (223/235), 97% (241/248), and 100% (253/253) of eyes. Significant differences in postoperative SE and cylinder were found between the MEL80 and iDesign groups (p<0.05). CONCLUSIONS: All evaluated LASIK treatment protocols are predictable and effective for the correction of myopia. The treatment planned with a high resolution aberrometer obtained the best postoperative refractive outcomes.

The Ocular Surface and How It Can Influence the Outcomes of Keratoprosthesis.

Severe ocular diseases may result in partial or complete limbal cell deficiency. Besides conservative options, treatment options include conjunctival replacement procedures and limbal autografting. Limbal allografts are an option in patients with bilateral limbal cell deficiency. In many of these cases, a keratoprosthesis (KPro) is the last option to restore functional vision in patients with severe corneal blindness with no other options.

Femtosecond laser-assisted intrastromal arcuate keratotomy to reduce corneal astigmatism.

PURPOSE: To report the initial results of intrastromal arcuate keratotomy performed with a femtosecond laser to treat corneal astigmatism. SETTING: Department of Ophthalmology, Paracelsus Medical University, Salzburg, Austria. DESIGN: Interventional case series. METHODS: Patients with corneal astigmatism (naturally occurring or after cataract surgery) were treated with an iFS femtosecond laser to perform paired arcuate cuts on the steep axis completely placed within the corneal stroma. Patients were followed for 6 months after surgery. Preoperative and postoperative (1-day, 1-week, and 1-, 3-, and 6-month) examinations included corrected and uncorrected visual acuities, manifest refraction, corneal topography, endothelial cell count, and corneal pachymetry. A subjective questionnaire was used to evaluate patient satisfaction. RESULTS: The study enrolled 16 patients. No perforations occurred, and all incisions were placed at the planned locations. After a 6-month follow-up, the mean refractive cylinder was reduced significantly from 1.41 diopters (D) ± 0.66 (SD) to 0.33 ± 0.42 D (P<.001). The mean topographic astigmatism was reduced significantly from 1.50 ± 0.47 D preoperatively to 0.63 ± 0.34 D at 6 months (P=.002). There was excellent refractive and topographic stability over time. The endothelial cell density was unchanged. Patient satisfaction was very high. CONCLUSION: The femtosecond laser allowed the effective creation of precise, purely intrastromal, arcuate incision patterns with an excellent safety profile, rapid recovery, and stability of vision without the known risks associated with incisions that penetrate Bowman membrane.

Bilateral reading performance of 4 multifocal intraocular lens models and a monofocal intraocular lens under bright lighting conditions.

PURPOSE: To compare changes in reading performance parameters after implantation of 4 multifocal intraocular lens (IOL) models and a monofocal IOL. SETTING: Department of Ophthalmology, Paracelsus Medical University, Salzburg, Austria. DESIGN: Prospective randomized controlled clinical trial. METHODS: Patients with bilateral cataract without additional ocular pathology were scheduled for bilateral implantation of Acri.Smart 48S monofocal, Acrysof Restor SN6AD3 apodized multifocal, AT LISA 366D diffractive multifocal, Tecnis ZMA00 diffractive multifocal, or Rezoom refractive multifocal IOLs. Bilateral corrected and uncorrected reading acuity, reading distance, mean and maximum reading speeds, and smallest log-scaled print size of a Radner reading chart were evaluated under bright lighting conditions (500 lux) using the Salzburg Reading Desk. Pupil size was not measured throughout the trial. The minimum follow-up was 12 months. RESULTS: The diffractive multifocal groups had significantly better uncorrected reading acuity and uncorrected smallest print size than the monofocal and refractive multifocal groups 1, 6, and 12 months postoperatively. The diffractive IOL groups had comparable uncorrected reading distance of approximately 32 cm, which was larger in the monofocal group (38.9 ± 8.4 cm) and refractive multifocal group (37.1 ± 7.3 cm) at the last visit. Patients with diffractive IOLs could read print sizes of approximately 0.74 to 0.87 mm, which was much better than in the monofocal and refractive multifocal groups. The diffractive AT LISA IOL provided the best reading speed values (mean and maximum, corrected and uncorrected). CONCLUSION: Multifocal IOLs with a diffractive component provided good reading performance that was significantly better than that obtained with a refractive multifocal or monofocal IOL. FINANCIAL DISCLOSURE: Drs. Grabner and Dexl were patent owners of the Salzburg Reading Desk technology (now owned by SRD-Vision, LLC). No other author has a financial or proprietary interest in any material or method mentioned.

Reading performance and patient satisfaction after corneal inlay implantation for presbyopia correction: two-year follow-up.

PURPOSE: To evaluate change in reading performance parameters after monocular Kamra corneal inlay implantation for the surgical correction of presbyopia. SETTING: University surgical outpatient center. DESIGN: Prospective interventional case series. METHODS: A corneal inlay was implanted in the nondominant eye. Naturally emmetropic and presbyopic patients between 45 years and 60 years old with an uncorrected distance visual acuity of at least 20/20 in both eyes without additional ocular pathology were eligible for inclusion. Bilateral uncorrected reading acuity, reading distance, mean and maximum reading speed, and the smallest log-scaled print size (lower case letter of a Radner reading chart) were evaluated using the Salzburg Reading Desk. The minimum postoperative follow-up was 24 months. RESULTS: Twenty-four patients were enrolled. The mean reading distance was 46.7 cm ± 6.3 (SD) preoperatively and 39.5 ± 6.4 cm 24 months postoperatively (P<.001). The mean reading acuity at best distance improved (0.33 ± 0.13 logRAD versus 0.23 ± 0.11 logRAD) (P=.004). The mean reading speed increased from 141 ± 20 words per minute (wpm) to 146 ± 20 wpm, respectively (P=.261), and the mean maximum reading speed from 171 ± 28 wpm to 180 ± 22 wpm, respectively (P=.110). The smallest print size improved from 1.50 ± 0.42 mm to 1.01 ± 0.22 mm, respectively (P<.001). CONCLUSION: Improving the depth of focus by monocular implantation of a small-aperture optic caused statistically significant changes in all tested reading performance parameters except reading speed metrics in emmetropic presbyopic patients.

Correction of myopic astigmatism with a foldable iris-claw toric phakic intraocular lens: short-term follow-up.

PURPOSE: To evaluate the efficacy, predictability, stability, and complications after implantation of a foldable iris-fixated toric phakic intraocular lens (pIOL) to correct myopic astigmatism. SETTING: University Eye Clinic, Paracelsus Medical University, Salzburg, Austria. DESIGN: Retrospective nonrandomized observational case series. METHODS: The study assessed eyes having implantation of an Artiflex toric pIOL with spherical power ranging from -1.0 to -13.5 diopters (D) and additional cylinder from -1.0 to -5.0 D, both in 0.5 D increments. The main parameters were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction stability, slitlamp biomicroscopy, tonometry, and central endothelial cell count (ECC). RESULTS: The study enrolled 42 eyes of 24 patients with a mean age of 35 years (range 18 to 52 years), a mean spherical equivalent of -7.52 D ± 2.22 (SD) (range -2.63 to -13.0 D), and a mean preoperative cylinder of -1.82 ± 0.96 D (range -1.0 to -5.0 D). Six months postoperatively, the UDVA (Snellen lines) was 1.0 or better in 38 eyes (90%). The CDVA improved by 1 line in 22 eyes (52%) and by 2 lines in 2 eyes (5%); no eye lost lines. All eyes were within ±0.50 of the target refraction (spherical equivalent); the mean refractive astigmatism was -0.18 ± 0.30 D. Refraction was stable from 1 day postoperatively. A slight ECC loss (-0.72%) occurred at 6 months. There were no serious complications. CONCLUSION: After a short-time follow-up, toric pIOL implantation was effective, predictable, stable, and safe for the correction of myopic astigmatism.

Central and peripheral corneal iron deposits after implantation of a small-aperture corneal inlay for correction of presbyopia.

PURPOSE: To describe central and peripheral corneal iron deposition after implantation of the AcuFocus corneal inlay (ACI 7000, AcuFocus Inc) for the surgical correction of presbyopia. METHODS: Patients who underwent inlay implantation between September 2006 and May 2007 and displaying corneal iron deposits were enrolled in the study. RESULTS: Eighteen (56%) eyes of 32 patients developed corneal iron deposition within 36 months after corneal inlay implantation. One (5.5%) eye had a central spot-like iron deposition only, 10 (55.5%) eyes had formation of deposits in a half-moon shape in the inferior cornea parallel to the outer margin of the inlay or a complete circular ring formation, and 7 (39%) eyes demonstrated deposits in both areas. The median interval between implantation and diagnosis of corneal iron deposition was 18 ± 9 months. CONCLUSIONS: Corneal iron deposition can develop in different shapes after implantation of the small-aperture ACI 7000. Alterations in tear film thickness, its composition, and corneal epithelial basal cell storage, resulting from changes in corneal topography, may be contributing factors for these specific iron depositions.

Dynamic corneal imaging.

PURPOSE: To determine the clinical practicability of in vivo dynamic corneal imaging (DCI) to assess the individual elastic properties of normal human eyes, eyes with abnormal findings, and eyes after refractive surgery. SETTING: University Eye Clinic, Paracelsus Private Medical University, Salzburg, Austria. METHODS: The DCI method uses sagittal, stepwise, central indentation of the cornea with electronically controlled microprecision motors and sequential registration of videotopography images. The indentation steps are preselected and range from 50 to 800 mum. The computerized analysis of the videotopography images captured during the process uses Zernike polynomials to establish a newly defined flexing curve for normal eyes and eyes with abnormal findings. RESULTS: Dynamic corneal imaging was done in 187 eyes of 103 patients who had clinically healthy corneas, distinct keratoconus, or previous refractive surgery. The method rapidly evaluated artificially and reversibly induced changes in corneal topography in a clinical setting using a modified Placido disk-based computer-assisted videokeratography system with a small cone. In early analysis, the flexing curve showed a significant correlation with the applied indentation depth. Factors influencing the shape of the curve were central corneal thickness, intraocular pressure, and patient age. The DCI method also allowed easy examination of keratoconic corneas and corneas after refractive surgery. CONCLUSIONS: Dynamic corneal imaging induced a reproducible and reversible change in corneal topography corresponding to the different indentation depths. The results indicate that several clinical parameters are correlated with corneal elastic behavior in vivo and that the technology could increase the predictability of refractive corneal surgery and help in the early diagnosis of corneal diseases and with newly developed therapies.

Anterior chamber angle biometry with ultrasound biomicroscopy after diode laser thermal keratoplasty.

PURPOSE: To evaluate the effect of diode laser thermal keratoplasty (DTK) on the geometry of the anterior chamber angle with ultrasound biomicroscopy (UBM). SETTING: Department of Ophthalmology and Optometry, Paracelsus Private Medical University, Salzburg, Austria. METHODS: In 9 eyes, a Rodenstock DTK (ProLaser Medical Systems) was used to correct hyperopia (n = 6) or hyperopic astigmatism (n = 3). Hyperopia was treated with a single- or double-ring pattern and hyperopic astigmatism, with additional spots in each of the flat half meridians. Ultrasound biomicroscopy measurements of the chamber angle were obtained preoperatively and 3 months postoperatively using a Humphrey UBM 840 system with a 50 MHz transducer. Quantitative measurements were performed at 3-, 6-, 9-, and 12-o'clock positions using a standardized method. RESULTS: No statistically significant differences between the preoperative and postoperative chamber angle measurements were detected. CONCLUSIONS: The results of the UMB measurements were surprising given the flattening of the corneal periphery found by computerized topography, a finding that suggests narrowing of the chamber angle. Shortening of the corneal tissue may result in centripetal traction that affects the trabecular meshwork and results in a relative opening of the chamber angle structures.

Correction of astigmatism with short arc-length intrastromal corneal ring segments: preliminary results.

OBJECTIVE: To evaluate the refractive effect of 130 degrees short arc length intrastromal corneal ring segments (ICRS) designed to correct myopia concurrent with astigmatism. DESIGN: Prospective, nonrandomized, comparative (self-controlled) trial. PARTICIPANTS: Ten eyes of 6 patients from one surgical center with manifest refraction spherical equivalent between -1.00 and -6.00 diopters (D), manifest cylinder correction between 1.00 and 6.00 D, and best spectacle-corrected visual acuity of 20/20 or better. INTERVENTION: The patients were assigned to receive 1 of 6 ICRS thicknesses, ranging from 0.25 to 0.50 mm by 0.05 mm increments, with an arc length of 130 degrees. MAIN OUTCOME MEASURES: Vector analysis of astigmatic correction. Efficacy was assessed by uncorrected visual acuity and by deviation of postoperative spherical and cylindrical refractive error from predicted correction. Safety was assessed by maintenance or loss of preoperative best spectacle-corrected visual acuity. Measurements were made before surgery and after surgery at days 1 and 7 and months 1, 2, 3, and 6. RESULTS: At 6 months, uncorrected visual acuity was 20/20 or better in 80% of eyes (8/10) and 20/40 or better in all eyes. Eight of 10 eyes (80%) were within +/-0.25 D of plano spherical equivalent manifest refraction. There was no loss of best spectacle-corrected visual acuity, and 6 of 10 eyes (60%) gained a line. Reduction of keratometric cylinder by ICRS thickness was statistically significant (P = 0.039). CONCLUSIONS: Preliminary results of visual and refractive performance after correction of compound myopic astigmatism using short arc length ICRS are promising.

Evaluation of bone reduction in osteo-odontokeratoprosthesis (OOKP) by three-dimensional computed tomography.

PURPOSE: To study the stability and preservation of the osteodental lamina in osteo-odontokeratoprosthesis (OOKP) according to Strampelli with spiral computed tomography (CT). METHODS: Computed tomography of the orbit was performed in nine patients after successful OOKP surgery. Indications for surgery included ocular pemphigoid (three patients), Lyell's syndrome (two patients), graft versus host disease (one patient), and severe chemical burns (three patients). In four eyes, the osteodental lamina was covered with a buccal mucosa graft; in five eyes, a "transpalpebral" approach with the placement of the optical cylinder through the patient's own lid skin was used. The mean time from surgery to examination was 4 years. The age of the patients ranged from 32 to 75 years (mean, 52). Spiral CT in the transaxial plane was performed, followed by three-dimensional (3D) surface reconstruction of the OOKP. The dimensions of the osteodental lamina were measured and compared with measurements taken at the time of surgery. RESULTS: A minor reduction of the lamina, mainly in the anterior and inferior part, could be found in all the patients without loss of stability and integrity of the lamina cylinder complex in seven patients. One patient showed complete resorption of the inferior half of the osteodental lamina, and another patient demonstrated "moth-eaten" dissolution of dentine and bone tissue. No correlation between the degree of reduction in the dimensions and patient age, diagnosis, or length of follow-up could be found. CONCLUSION: Osteo-odontokeratoprosthesis shows good results in patients with corneal blindness not amenable to keratoplasty. Nevertheless, the surgeon must be aware of eventual signs of dissolution of the osteodental lamina, making close follow-up mandatory. Because ultrasound biomicroscopy cannot be used in these cases, spiral CT with 3D reconstruction seems to be a good diagnostic alternative.

Histologic evaluation of corneal stroma in rabbits after intrastromal corneal ring implantation.

PURPOSE: Previous refractive corneal implants have produced histologic changes characteristic of nonspecific lipid keratopathy. Intacs intrastromal corneal ring segments are polymethylmethacrylate (PMMA) corneal inserts approved for the correction of low myopia by the U.S. Food and Drug Administration. The purpose of this study was to describe histologic changes associated with these corneal implants in rabbit eyes. METHODS: Two 150-degree PMMA arc segments, 0.30 mm thick, were surgically implanted through a single radial incision at two-thirds stromal depth in the mid-peripheral cornea of five New Zealand white rabbits. We collected corneas 6 months after implantation that were prepared for light and electron microscopy. We analyzed tissue with oil red O, filipin, and periodic acid-Schiff (PAS) staining. Additional studies with energy-dispersive x-ray analysis and autofluorescent microscopy were conducted. RESULTS: In all samples, we observed new collagen formation with lamellar organization adjacent to the implant and increased keratocyte density. Intracellular accumulations of osmophilic and saturated lipid material corresponded to stromal opacification visible by slit-lamp microscopy. These same regions were autofluorescent and stained positively with oil red O, and filipin but negatively with PAS. Granular lipid inclusions characteristic of lipofuscinosis were absent on transmission electron microscopy. Energy-dispersive x-ray analysis demonstrated elevated levels of calcium compared with adjacent tissue. CONCLUSION: Tissue response to these corneal inserts includes keratocyte activation, intracellular lipid accumulation, and new collagen formation. Our histologic findings suggest that these deposit formations are not lipofuscin accumulations.

[Clinical and histological studies on the intrastromal corneal ring segments (ICRS(R), Intacs(R))]. / Klinische und histologische Studien zu den intrastromalen kornealen Ringsegmenten (ICRS(R), Intacs(R)).

Intrastromal corneal ring segments (ICRS(R), Intacs(R)) are corneal inlays made of PMMA with an arc length of 150 degrees for the correction of low to moderate myopia. This additive and potentially reversible method has recently been developed to clinical usefulness during the last few years. Besides the historical development und the results of the US FDA studies, we focus on the results of the European experience with this technique. For the first time, long-time follow-up results (5 years from a single surgical center) are presented. Morphological changes after implantation of Intacs(R) were investigated in a series of patients by confocal microscopy. Weeks and months after implantation "lamellar channel deposits" regularly appear around the segments. This material consists of intracellular lipids (cholesterol ester, triglyceride and unesterified cholesterol), as we could show in new histological studies on rabbit eyes. New developments of this technique include short arc length segments (130 degrees ) for the correction of myopia concurrent with astigmatism and radially placed corneal inlays (Intrastromal Corneal Segments, ICS(R)) for the correction of hyperopia. In recent years, Intacs(R) have also been implanted in eyes with keratoconus and keratectasia after LASIK. These early results seem to indicate that in certain cases of early keratoconus, these implants can indeed improve corneal geometry and vision. Even in cases of regression or undercorrection after LASIK (with thin corneas), Intacs(R) seem to give promising results in selected cases. Although Intacs(R) do give comparable results regarding both safety and efficacy when compared with PRK and LASIK, this technology has not yet been widely accepted among refractive surgeons. Whether Intacs(R) will play a greater role in routine refractive surgery in the future or will just remain a special device for the correction of keratectasia, keratoconus or regression after LASIK cannot yet be decided with certainty.

Histopathology of human corneas after amniotic membrane and limbal stem cell transplantation for severe chemical burn.

PURPOSE: To describe the histopathologic changes in the cornea following amniotic membrane transplantation (AMT) combined with limbal transplantation. METHODS: Four eyes with complete limbal stem cell deficiency after severe chemical burn underwent AMT with either a living-related conjunctival limbal allograft (lr-CLAL) (three eyes) or a conjunctival limbal autograft (CLAU) (one eye) for ocular surface reconstruction. Penetrating keratoplasty was performed several months after the initial procedure for further visual rehabilitation. Mean follow up time was 20 months. Light and transmission electron microscopy (TEM) and indirect immunofluorescence microscopy of the excised corneal buttons were performed. RESULTS: All specimens displayed a multilayered epithelium without conjunctival goblet cells over the entire corneal surface. Basal epithelial cells demonstrated a firm connection to the remnants of the transplanted amniotic membrane (AM), which at some places appeared to be in a state of "modification" or "remodeling" in the collagen layers. The basement membrane zone displayed a positive staining when using antibodies against collagen IV and VII, integrin alpha6 and beta4, laminin 5, and bullous pemphigoid antigen 2. Remnants of the AM in the specimen showed staining of collagen IV, which was found also in cross-sections of cryopreserved AM. The recipients Bowman's membranes that were only partially present after the initial trauma were significantly disturbed. CONCLUSION: Within the time frame studied, the transplanted AM apparently survives and integrates into the host tissue being modified or remodeled by recipient cells. AMT in combination with a CLAU or lr-CLAL is a useful technique in promoting a rapid and stable reepithelialization of a corneal surface following severe chemical or thermal damage.

Histopathologic findings in explanted osteo-odontokeratoprosthesis.

PURPOSE: To report the histologic findings in three explanted osteo-odontokeratoprosthesis (OOKP) laminae. METHODS: The osteodental lamina of patient 1 with linear IgA bullous dermatosis had to be explanted 15 months after OOKP surgery because of permanent leakage after the resorption of the inferior half of the bone/dentin complex. Patient 2 underwent surgery because of corneal blindness caused by ocular pemphigoid. The remnants of the osteodental lamina were removed after a spontaneous loss of the optic cylinder 30 months after surgery. Patient 3 showed decentration of the optic cylinder 14 years after OOKP surgery was performed because of severe bilateral chemical burn. After intraoperative detachment of the optical cylinder from the broken lamina, the keratoprosthesis had to be completely removed. All specimens were fixed, decalcified using electrolysis, sectioned, and stained with hematoxylin and eosin. RESULTS: All three laminae showed some degree of transformation and resorption of dentin and bone tissue. An inflammatory reaction could be observed in the laminae of patient 1 and 2. Downgrowth of keratinizing squamous epithelium and a reduction of bone tissue and dentin was found in patient 1. Most of the osteodental lamina of patient 2 had been replaced by connective tissue. No signs of acute or chronic inflammation could be found in patient 3. The optical cylinder was surrounded by a thin layer of connective tissue that was enclosed by a layer of woven bone. Dentine was found in just one half of the specimen, adjacent to a partly preserved alveolar-dental ligament. CONCLUSION: No conclusive explanation for the dissolution of the osteodental lamina in some of the patients can be offered at this time, although a few different mechanisms such as epithelial downgrowth and/or localized inflammation seem to play a pivotal role. Conversely, the preservation of the alveolar-dental ligament seems to be essential for the maintenance of the integrity of the OOKP.