Comparison of corneal and total ocular aberrations before and after myopic LASIK.

PURPOSE: To assess the compensation of total ocular and corneal wavefront aberrations after conventional myopic LASIK. METHODS: This study comprised 57 eyes of 57 patients. Total and corneal aberrations were measured preoperatively and 3 months postoperatively using the OPD-Scan (NIDEK Co Ltd) aberrometer. Total and corneal aberrations root-mean-square (RMS) was calculated out to the 6th Zernike order for a 6.0-mm pupil diameter. The percentage increase postoperatively was defined by the ratio of RMS pre- and postoperatively for each corneal and total eye group. The compensation between corneal and internal aberrations for a given aberration group was defined as: (corneal aberration group RMS - total eye aberration group RMS)/corneal aberration group RMS. RESULTS: Postoperatively, higher order aberrations increased by a factor of 1.77+/-1.26 (total) and 2.47+/-2.25 (corneal) (P<.05). Coma aberration increased by a factor of 2.43+/-2.61 (total) and 2.56+/-2.66 (corneal). Spherical aberration increased by a factor of 1.46+/-1.83 (total) and 2.64+/-2.24 (corneal). The values of the ratio of compensation did not change significantly before and after LASIK for individual aberrations (P>.05). CONCLUSIONS: Although myopic LASIK induced significant corneal aberrations, the level of partial compensation of corneal aberrations by internal structures remained unchanged. These results suggest that the previously described emmetropization that is effective during development may also be effective with acquired variations in corneal shape.

Clinical Outcomes of an Asymmetric Model of Intrastromal Corneal Ring Segments for the Correction of Keratoconus.

PURPOSE: To evaluate the clinical outcomes of a new model of intrastromal corneal ring segments (ICRSs) (Keraring AS) in patients with keratoconus and quantify subsequent changes in refraction and corneal topography. METHODS: This nonrandomized, single-center, retrospective observational study explores the effect of progressive thickness ICRS implantation in patients with keratoconus with a 3-month follow-up. After creating an intrastromal tunnel using a femtosecond laser, 1 or 2 ICRSs of progressive thicknesses (150/250 µm or 200/300 µm) and 160-degree arc length were implanted. Changes in uncorrected distance visual acuity, best-corrected distance visual acuity, refractive outcomes, corneal astigmatism, and maximum keratometry readings were recorded before and after surgery. RESULTS: The study cohort consisted of 82 patients (104 eyes) with a mean age of 31.2 ± 10 years. At 3 months, ICRS implantation significantly improved uncorrected and corrected visual acuities from 0.82 to 0.46 (logarithm of the minimum angle of resolution [LogMAR]) and from 0.31 to 0.21 (LogMAR), respectively (P < 0.001). The mean spherical error reduced from -1.74 diopters (D) to -0.90 D (P < 0.001), and the mean cylindrical error reduced from -4.22 D to -2.01 D (P < 0.001). The manifest refraction spherical equivalent reduced from -3.85 D to -1.91 D (P < 0.001). All topographic parameters were reduced, including maximum keratometry (53.6 D vs. 50.3 D) and keratometric astigmatism (-4.6 D vs. -2.2 D) (P < 0.001). CONCLUSIONS: The Keraring AS provides a new, apparently safe, and effective means of improving visual acuity and reducing the refractive error and mean keratometry in eyes with asymmetric keratoconus.

Extracellular matrix metalloproteinase inducer/CD147 promotes myofibroblast differentiation by inducing alpha-smooth muscle actin expression and collagen gel contraction: implications in tissue remodeling.

Extracellular matrix metalloproteinase inducer (EMMPRIN) is a cell surface glycoprotein enriched on tumor cells and normal epithelia. It is mainly known for its ability to induce matrix metalloproteinase production in fibroblasts following epithelial-stromal interaction. We sought to examine whether EMMPRIN has a broader role promoting fibroblast-to-myofibroblast differentiation. Because alpha-smooth muscle actin (alphaSMA) is considered a marker of this differentiation process, we analyzed the effect of EMMPRIN on its expression in corneal and skin fibroblasts by Western blots, immunocytochemistry, and a functional assay of collagen lattice contraction. Increasing EMMPRIN expression by cDNA transfection or by treatment with exogenously added recombinant EMMPRIN resulted in an up-regulation of alphaSMA expression. EMMPRIN also increased the contractile properties of the treated fibroblasts as demonstrated by the immunohistochemical appearance of stress fibers and by the accelerated contraction of fibroblast-embedded collagen lattices. Blocking EMMPRIN expression by small interfering RNA inhibited alphaSMA and collagen gel contraction induced not only by EMMPRIN but also by transforming growth factor-beta, a major mediator of myofibroblast differentiation that also regulated EMMPRIN expression. These findings, combined with the fact that EMMPRIN and alphaSMA colocalized to the same cells in the stroma of pathological corneas, expand on the mechanism by which EMMPRIN remodels extracellular matrix during wound healing and cancer.

Comparison of and correlation between anterior and posterior corneal elevation maps in normal eyes and keratoconus-suspect eyes.

PURPOSE: To compare the anterior and posterior corneal elevation maps between keratoconus-suspect eyes and normal eyes. SETTING: Rothschild Foundation, AP-HP, University Paris VII, Hôpital Bichat Claude Bernard, Paris, France. METHODS: The anterior and posterior corneal surface elevations were analyzed and compared in 60 normal myopic patients and 48 keratoconus-suspect patients. The anterior and posterior best-fit sphere radii, central and thinnest corneal pachymetries, anterior and posterior aconic shape parameters (aconic radius, aconic asphericity, aconic toricity), and anterior and posterior elevation in the 1.0 mm radius zone were analyzed. The correlations between elevation and aconic shape parameters between the anterior and posterior surfaces were compared. RESULTS: The mean central and thinnest pachymetry values were significantly lower in keratoconus-suspect eyes (P<.0001). Compared with normal eyes, keratoconus-suspect eyes had significantly increased anterior toricity (P = .0002) and posterior toricity (P<.0001), more negative asphericity (P = .042), and higher posterior elevation (P<.0001). The correlation between aconic toricity and the anterior and posterior corneal surfaces was better in keratoconus-suspect eyes than in normal eyes. Aconic asphericity and apical curvature were less correlated in keratoconus-suspect eyes than in normal eyes. CONCLUSIONS: The posterior corneal elevation and the corneal thickness values were different in keratoconus-suspect eyes. The correlation between the anterior and posterior corneal aconic shapes was between keratoconus-suspect eyes and normal eyes.

Archipelago keratitis: a clinical variant of recurrent herpetic keratitis?

OBJECTIVE: To describe archipelago keratitis, a presumed clinical variant of herpetic epithelial keratitis. DESIGN: Case series. PARTICIPANTS: A series of 6 patients with an unusual form of superficial keratitis. METHODS: History, including age, gender, clinical evolution, and treatment; slit-lamp biomicroscopy findings; in vivo confocal microscopy findings; and corneal epithelial scrapings were analyzed. MAIN OUTCOME MEASURES: Clinical ocular examination, a diagnostic workup including corneal scraping for herpesvirus polymerase chain reaction, in vivo confocal microscopy, and therapeutic outcome. RESULTS: The authors describe a series of 6 patients with keratitis consisting of foci of epithelial erosions associated with subepithelial nummular inflammatory infiltrates and disposed in a radial, centripetal, archipelagolike pattern originating from the limbus. All the patients had a past history of herpetic epithelial keratitis, herpetic vesicles on the ipsilateral lid, or both. Polymerase chain reaction-based screening for herpes simplex virus 1 and 2 in corneal scrapings demonstrated positive results in 2 patients. In vivo corneal confocal microscopy revealed focal areas of hyperreflective epithelial cells and hyperreflective subepithelial dendritic structures overlying activated keratocytes. All the patients improved with oral valacyclovir treatment followed by topical steroid therapy. CONCLUSIONS: Archipelago keratitis may be a new clinical variant of herpetic keratitis, reflecting herpetic dissemination from the limbus to the center of the cornea.

Long-term visual outcome of childhood blepharokeratoconjunctivitis.

PURPOSE: To assess the visual outcome of childhood blepharokeratoconjunctivitis. DESIGN: Retrospective noncomparative case series. METHODS: We reviewed visual acuity and corneal examination results for 23 patients (mean age 19 +/- 4 years, range, 11 to 26 years) who had healed more than three years previously (up to 15 years). RESULTS: The disease involved 29 eyes and was unilateral in 17 children. Corneal sequelae (neovascularization or scars) involved 18 eyes (62%) of 15 children (65%). Mean best-corrected visual acuity was 20/25 (range, 20/100 to 20/20). Best-corrected visual acuity was no more than 20/30 in seven eyes (24%) of seven children (30%). Fifteen eyes (52%) of 13 children (45%) had astigmatisms of at least 0.75 diopters attributable to corneal scars. CONCLUSIONS: Corneal and visual sequelae are frequent in childhood blepharokeratoconjunctivitis. Early diagnosis and specific treatment are mandatory.

Objective assessment of the quality of vision before and after repositioning of a dislocated iris-fixated aphakic anterior chamber lens.

PURPOSE: To document severe visual symptoms due to the dislocation of an iris-fixated aphakic anterior chamber lens using wavefront aberrometry. METHODS: A patient complaining of severe visual blur and distortion due to a decentered Artisan iris-fixated anterior chamber lens was evaluated pre- and postoperatively after recentration. The patient underwent complete ophthalmic evaluation including the measurement of corneal topography and wavefront aberrations using the NIDEK OPD-Scan. OPD Station software was used to correlate and simulate the patient's symptoms. RESULTS: After the repositioning procedure, the visual symptoms resolved, and high magnitudes of tilt (7.536 microm) and high order aberrations (5.129 microm) were dramatically reduced by simple lens repositioning (4.40-mm pupil). The cylinder magnitude was reduced from 6.25 to 0.75 diopters. CONCLUSIONS: These are the first diagnostic images of this kind in a highly aberrated eye with iris-fixated anterior chamber lens dislocation. The images documented the optical effect and visual consequences of IOL decentration and subsequent recentration.

Geometric customization of optical and transition zone parameters for treatment of compound myopic astigmatism with the NIDEK EC-5000 excimer laser.

PURPOSE: To compare the refractive outcome of two ablation zone designs using LASIK for the correction of compound myopic astigmatism. METHODS: This retrospective study compared refractive outcomes in two groups of patients undergoing LASIK. In the circular treatment group, 45 eyes were corrected with circular optical and transition zones of 6 mm and 6.5 mm, respectively. In the customized treatment group, 45 eyes were corrected with optical and transition zones enlarged along the flat axis to 6.5 mm and 7.5 mm, respectively. P values <.05 were considered statistically significant. RESULTS: Mean preoperative spherical equivalent refraction was -5.36+/-2.02 diopters (D) and -5.36+/- 2.13 D for the circular and customized treatment groups, respectively. Mean postoperative spherical equivalent refraction was -0.09+/-0.74 D and -0.11+/-0.42 D for the circular and customized treatment groups, respectively. Mean cylinder was 0.49+/-0.39 D and 0.22+/-0.43 D for the circular and customized treatment groups, respectively (P<.001). Postoperative blur strength index was 0.68+/-0.44 D and 0.39+/-0.27 D in the circular and customized treatment groups, respectively (P<.001). Uncorrected visual acuity was significantly better in the customized treatment group compared with the circular treatment group (P<.05). The gain in lines of best spectacle-corrected visual acuity was significantly greater in the customized treatment group compared with the circular treatment group (P<.001). CONCLUSIONS: An elliptical ablation zone for treating compound myopic astigmatism results in better efficacy, safety, and lower tissue removal than a circular treatment zone. This may be due to the geometric optimization provided by the enlargement of the optical and transition zones along the flat meridian.

Corneal hysteresis, resistance factor, topography, and pachymetry after corneal lamellar flap.

PURPOSE: To measure prospectively the early changes in corneal hysteresis, topography, and pachymetry after the creation of a stromal flap cut without laser photoablation. METHODS: A 37-year-old man was referred for a bioptic procedure to correct for compound myopic astigmatism in the left eye. A 159-microm-thick 8x8.5-mm superior hinged flap was created with a mechanical microkeratome in the left cornea. Changes in the corneal hysteresis, corneal resistance factor, Goldmann correlated intraocular pressure (lOP), corneal compensated IOP, anterior and posterior topography, and optical and ultrasound pachymetry were monitored prospectively before and at 1 hour, 1 day, 5 days, and 25 days after flap creation. The right eye served as a control. RESULTS: In the left eye, corneal hysteresis and corneal resistance factor decreased immediately after the flap cut and remained lower than preoperatively at 1 hour, 1 day, 5 days, and 25 days. Corneal compensated IOP varied significantly less than Goldmann correlated IOP in both eyes. Central flattening of the horizontal meridians was observed on the difference topography maps. The values of the left eye posterior best fit sphere increased after the flap cut. Increased central corneal thickness occurred immediately after the flap cut and decreased over time without returning to its preoperative value. CONCLUSIONS: The creation of a stromal flap can modify the biomechanical properties of the cornea, including a reduction in corneal hysteresis. The topographic changes were consistent with previously reported cases of flap cut in normal corneas.

Contribution of the corneal epithelium to anterior corneal topography in patients having myopic photorefractive keratectomy.

PURPOSE: To assess the variations in corneal topographic characteristics after removal of the epithelium in patients having myopic photorefractive keratectomy (PRK). SETTING: Rothschild Foundation, Paris, France. METHODS: Forty-four eyes of 25 patients with myopia had corneal topography examination with the Orbscan II device (Bausch & Lomb) before removal of the corneal epithelium preoperatively and after removal of the corneal epithelium during PRK. On each examination, elevation, curvature, and pachymetry parameters were recorded and analyzed (paired 2-sided Student t test). RESULTS: The mean difference in central pachymetry between preoperative and epithelial removal was 37.84 mum +/- 9.82 (SD) (range 19 to 58 mum). The mean best-fit spherical surface radius was 7.75 +/- 0.28 mm (range 7.25 to 8.42 mm) before removal of the epithelium and 7.92 +/- 0.29 mm (range 7.39 to 9.16 mm) after removal of the epithelium (P<.0001). The mean simulated K-value difference increased from 0.75 +/- 0.55 diopter (D) (range 0.1 to 4.7 D) before removal to 1.21 +/- 0.66 D (range 0.2 to 4.7 D) after removal (P<.0001). The mean simulated value decreased from 43.77 +/- 1.83 D (range 40.25 to 47.00 D) to 42.44 +/- 1.73 D (range 37.05 to 45.50 D), respectively. The mean power (3.0 mm) decreased from 44.42 +/- 1.59 D (range 40.4 to 47.2 D) before removal to 43.46 +/- 1.37 D (range 39.7 to 46.9 D) after removal. The mean irregularity index increased from 1.07 +/- 0.35 D (range 0.5 to 2.5 D) to 2.03 +/- 0.38 D (range 1.3 to 3.3 D), respectively (P<.0001). The mean asphericity value (Q) changed from -0.44 +/- 0.14 (range -0.72 to -0.20) to -0.65 +/- 0.46 (range -1.04 to 0.14), respectively (P = .003). CONCLUSIONS: The epithelium affected the topographic properties of the cornea by significantly reducing corneal topographic astigmatism and irregularity. This might prove to be important in the assessment of patient candidacy for and treatment planning in refractive surgery.

Topical cyclosporine A in severe steroid-dependent childhood phlyctenular keratoconjunctivitis.

PURPOSE: To assess the efficacy of topical cyclosporine A (CsA) in children with phlyctenular keratoconjunctivitis associated with severe steroid-dependent corneal inflammation. DESIGN: Prospective, noncomparative, interventional case series. METHODS: patients: Children with phlyctenular keratoconjunctivitis associated with severe steroid-dependent corneal inflammation and not responding to oral antibiotics (cyclines or erythromycin). intervention: Topical CsA 2% four times daily, initially combined with topical dexamethasone for the first week. main outcome measures: Efficacy was judged by the patients (symptoms and ocular redness) and by the ophthalmologist (ocular redness and corneal inflammation). The patients were monitored for adverse effects, and cyclosporinemia was determined every 3 months. RESULTS: We studied 11 children (13 eyes) with a mean age of 9 years (range, 4 to 15 years). Inflammation was controlled in all the eyes within 14 days. Inflammation did not recur during CsA monotherapy, during a mean follow-up of 12 +/- 8 months (range, 6 to 31 months). CsA therapy was stopped in eight patients (10 eyes) after a mean treatment duration of 13 +/- 9 months (range, 6 to 31 months), and no recurrences occurred during 10 +/- 3 months of follow-up (range, 6 to 12 months). Local tolerance of CsA was good. None of the patients had detectable CsA blood levels. CsA was withdrawn in one case after 6 months, because of generalized skin rash. CONCLUSIONS: Long-term topical CsA 2% therapy is safe and effective in children with phlyctenular keratoconjunctivitis associated with severe steroid-dependent corneal inflammation.

Measurement of combined corneal, internal, and total ocular optical quality analysis in anterior segment pathology with the OPD-scan and OPD-station.

PURPOSE: To show the clinical use of the NIDEK OPD-Scan wavefront aberrometer and OPD-Station software in anterior segment surgery and pathology. METHODS: Case examples are presented along with discussion about the relevant clinical data obtained from the OPD-Scan and OPD-Station software. RESULTS: Six case examples including cataract surgery, secondary IOL implantation, phakic intraocular lens surgery, pterygium surgery, contact lens fitting, and multifocal ablations are discussed. CONCLUSIONS: A complete understanding of the optics of the eye facilitates a better clinical comprehension of a variety of conditions in anterior segment surgery and pathology.

EMMPRIN/CD147, an MMP modulator in cancer, development and tissue repair.

Matrix metalloproteinases (MMPs) play a central role in normal tissue remodeling and disease, they regulate tumor microenvironment and their expression is increased in most human cancers. Targeting their activity remains a major challenge. Their production and activation is tightly regulated by complex mechanisms that include cytokines and growth factors, cell-matrix and cell-cell interactions. The observations of increased MMP level at the epithelio-stromal interface led to the identification of EMMPRIN/CD147, a membrane spanning molecule highly expressed in tumor cells, that stimulates MMPs production in neighboring fibroblasts. Later studies have shown that EMMPRIN can also induce MMP in the same population of cells. Elevated EMMPRIN level was detected in numerous malignant tumors and has been correlated with tumor progression in experimental and clinical conditions. The presence and modulation of EMMPRIN in normal tissues associated with increased MMP expression suggests that this EMMPRIN-mediated MMP induction could be a common mechanism in non-tumoral physiological and/or pathological situations. Targeting EMMPRIN in cancer and other pathological conditions such arthritis and ulceration appears a promising future therapeutic strategy, but requires a better understanding of its mode of action and regulation. Potential regulators that influence EMMPRIN level and its MMP inducing activity include growth factors, hormones, glycosylation and membrane shedding. This review will discuss the recent findings concerning these diverse regulatory mechanisms in various physiological and pathological situations.

Volume estimation of excimer laser tissue ablation for correction of spherical myopia and hyperopia.

PURPOSE: To determine the theoretical volumes of ablation for the laser treatment of spherical refractive errors in myopia and hyperopia. METHODS: The cornea was modeled as a spherical shell. The ablation profiles for myopia and hyperopia were based on an established paraxial formula. The theoretical volumes of the ablated corneal lenticules for the correction of myopia and hyperopia were calculated by two methods: (1) mathematical approximation based on a simplified geometric model and (2) finite integration. These results were then compared for optical zone diameters of 0.5 to 11.00 mm and for initial radii of curvature of 7.5, 7.8, and 8.1 mm. RESULTS: Referring to a simplified geometrical model, the volume of ablated corneal tissue was estimated to be proportional to the magnitude of treatment (D) and to the fourth power of the treatment diameter (S(4)). For refractive correction of myopia and hyperopia, volume estimations using our formula, V congruent with D. (S/9)(4), were similar to those obtained by finite integration for optical zone diameters of 0.5 to 8.5 mm and for corneal radii of curvature within the clinical range (7.5, 7.8, and 8.1 mm). CONCLUSIONS: The theoretical volume of corneal tissue ablated within the optical zone for spherical corrections can be accurately approximated by this simplified formula. This may be helpful in evaluating factors that contribute to corneal ectasia after LASIK for myopia and hyperopia. Treatment diameter (S) is the most important determinant of the volume of tissue ablation during excimer laser surgery.

Corneal asphericity change after excimer laser hyperopic surgery: theoretical effects on corneal profiles and corresponding Zernike expansions.

PURPOSE: To determine the theoretical relationships between the changes in corneal paraxial power, asphericity, and the corresponding Zernike polynomial expansion after conventional and customized excimer laser correction of hyperopia. METHODS: The initial corneal profile was modeled as a conic section of apical radius of curvature R1 and asphericity Q1. The theoretical value of the postoperative apical radius of curvature R2 was computed by using a paraxial formula from the value of R1 and hyperopic defocus D. The postoperative asphericity Q2 of the corneal surface was computed within the optical zone of diameter S after the delivery of a Munnerlyn-based profile of ablation for hyperopia using conic section-fitting and minimization of the squared residuals. These calculations were repeated for different values of defocus, initial apical radius of curvature, and asphericity. Taylor series expansions were also used to provide an approximation aimed at predicting change in asphericity. The coefficients of a Zernike polynomial expansion of the rotationally symmetrical corneal profile (defocus C2(0), spherical aberration C4(0), secondary spherical aberration C6(0)) were also computed, by using scalar products applied to the considered corneal profile modeled as a conic section and were expressed as a function of both its apical radius and asphericity. This allowed approximation of the variations of the Zernike polynomial expansion of the corneal profiles by subtracting the postoperative coefficient weighting a particular aberration from that of the preoperative one in different theoretical situations, after both conventional and customized hyperopia treatments aimed at controlling the postoperative corneal asphericity and delivered over a normalized pupil diameter. RESULTS: Conical least-squares fitting was unambiguous, allowing approximation of the postoperative corneal profile as a conic section of apical radius R2. After a Munnerlyn-based hyperopia treatment, the sign of the asphericity of this profile remains theoretically unchanged, but its value decreased for initially oblate and increased for initially prolate corneas, respectively. A similar trend was noted with the approximation obtained by the Taylor series expansion. The alteration of the apical radius and/or of the asphericity of the corneal surface resulted in variations of both the corneal profile Zernike coefficients C2(0) and C4(0). The former was essentially dependent on the variation of the apical radius and the latter essentially on the variation of both apical radius and asphericity. CONCLUSIONS: Conventional and customized profiles of ablation for hyperopia alter the postoperative corneal asphericity and the Zernike coefficients of the corneal profile. The results of this study may be useful in the interpretation of the postoperative variations of the corneal profile and their impact on corneal wavefront expansion variations after both conventional and customized profiles of ablation.

Analysis of customized corneal ablations: theoretical limitations of increasing negative asphericity.

PURPOSE: To determine the ablation depths of customized myopic excimer laser photoablations performed to change corneal asphericity after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). METHODS: A mathematical model of aspheric myopic corneal laser surgery was generated. The initial corneal surface was modeled as a conic section of apical radius R(1) and asphericity Q(1). The final corneal surface was modeled as a conic section of apical R(2) and asphericity Q(2), where R(2) was calculated from the paraxial optical formula for a given treatment magnitude (D), and Q(2) was the intended final asphericity. The aspheric profile of ablation was defined as the difference between the initial and final corneal profiles for a given optical zone diameter (S), and the maximal depth of ablation was calculated from these equations. Using the Taylor series expansion, an equation was derived that allowed the approximation of the central depth of ablation (t(0)) for various magnitudes of treatment, optical zone diameters, and asphericity. In addition to the Munnerlyn term (M), incorporating Munnerlyn's approximation (-D small middle dot S(2)/3), the equation included an asphericity term (A) and a change of asphericity term (Delta). This formula (t(0) = M + A + Delta) was used to predict the maximal depth of ablation and the limits of customized asphericity treatments in several theoretical situations. RESULTS: When the initial and final asphericities were identical (no intended change in asphericity; Q(1) = Q(2); Delta = 0), the maximal depth of ablation (t(0) = M + A) increased linearly with the asphericity Q(1). To achieve a more prolate final asphericity (Q(2) < Q(1); dQ < 0; Delta > 0), the maximal depth of ablation (M + A + Delta) was increased. For treatments in which Q(2) was intended to be more oblate than Q(1) (Q(2) > Q(1); dQ > 0; Delta < 0), the maximal depth of ablation was reduced. These effects sharply increased with increasing diameters of the optical zone(s). Similarly, in the case of PRK, the differential increase in epithelial thickness in the center of the cornea compared with the periphery resulted in increased oblateness. CONCLUSIONS: Aspheric profiles of ablation result in varying central depths of ablation. Oblateness of the initial corneal surface, intentional increase in negative asphericity, and enlargement of the optical zone diameter result in deeper central ablations. This may be of clinical importance in planning aspheric profiles of ablation in LASIK procedures to correct spherical aberration without compromising the mechanical integrity of the cornea.

The first international consensus on mucous membrane pemphigoid: definition, diagnostic criteria, pathogenic factors, medical treatment, and prognostic indicators.

OBJECTIVE: We aimed to develop consensus-based recommendations for streamlining medical communication among various health care professionals, to improve accuracy of diagnosis and treatment, and to facilitate future investigations for mucous membrane pemphigoid. PARTICIPANTS: Because of the highly specific nature of this group of diseases, the 26 invited participants included either international scholars in the field of mucous membrane pemphigoid or experts in cutaneous pharmacology representing the 3 medical disciplines ophthalmology, oral medicine, and dermatology. EVIDENCE: The first author (L.S.C.) conducted a literature search. Based on the information obtained, international experts who had contributed to the literature in the clinical care, diagnosis, and laboratory investigation for mucous membrane pemphigoid were invited to participate in a consensus meeting aimed at developing a consensus statement. CONSENSUS PROCESS: A consensus meeting was convened and conducted on May 10, 1999, in Chicago, Ill, to discuss the relevant issues. The first author drafted the statement based on the consensus developed at the meeting and the participants' written comments. The draft was submitted to all participants for 3 separate rounds of review, and disagreements were reconciled based on literature evidence. The third and final statement incorporated all relevant evidence obtained in the literature search and the consensus developed by the participants. The final statement was approved and endorsed by all 26 participants. CONCLUSIONS: Specific consensus-based recommendations were made regarding the definition, diagnostic criteria, pathogenic factors, medical treatment, and prognostic indicators for mucous membrane pemphigoid. A system of standard reporting for these patients was proposed to facilitate a uniform data collection.

Three-dimensional representation and qualitative comparisons of the amount of tissue ablation to treat mixed and compound astigmatism.

PURPOSE: To compare the shape and volume of the lenticules of corneal tissue ablated for the correction of spherical, cylindrical, and spherocylindrical refractive errors using Boolean operations of theoretical 3-dimensional (3-D) surfaces. SETTING: Department of Ophthalmology, Rothschild Foundation, Paris, France. METHODS: Digital modeling software was used to perform graphic representations of ablated lenticules on 3-D virtual surfaces. Various Boolean operations were performed between different preoperative and postoperative surfaces, and the additional and subtractive properties of ablated theoretical lenticules were analyzed to determine profiles of ablated lenticules for mixed and compound myopic and hyperopic astigmatism. RESULTS: Negative-cylindrical treatment, used to treat simple myopic astigmatism, was equivalent to the combination of a positive-cylindrical and a negative-spherical treatment of the same magnitude. Combining a pure negative-cylindrical and a positive-spherical treatment in a sequential strategy when treating compound astigmatism resulted in redundant ablation (plano lenticule), leading to an unnecessary increase in the amount of tissue ablation. CONCLUSIONS: Negative-cylindrical treatments result in greater tissue ablation than corresponding positive-cylindrical treatments. For any given compound astigmatic error, the strategy using the greater magnitude of positive cylinder incurs the minimal amount of tissue ablation.

Vector summation of anterior and posterior corneal topographical astigmatism.

PURPOSE: To determine whether vector addition of posterior corneal astigmatism improves the correlation between topographical and refractive astigmatism. SETTING: Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, USA. METHODS: Orbscan topographical maps of 40 eyes (31 patients) showing 1.0 to 6.0 diopters (D) of astigmatism were analyzed. Topographical anterior and posterior corneal surface astigmatism was determined. Refractive astigmatism was compared to topographical astigmatism using 3 methods: anterior topographical astigmatism, overall topographical astigmatism obtained by vector summation of anterior and posterior topographical astigmatism, and simulated keratometry (SimK). RESULTS: Refractive astigmatism ranged from 0.25 to 5.00 D. The mean error in magnitude between topographical and refractive astigmatism was significantly smaller with the overall topographical method (1.06 D +/- 0.92 [SD]) than the anterior topographical method (1.37 +/- 1.04 D) (P <.0001). The mean error in axis between topographical and refractive astigmatism was smaller with the overall topographical method (10.4 +/- 13 degrees) than with the anterior topographical method (15.5 +/- 30.6 degrees) and with SimK (13.3 +/- 15.1 degrees), but these differences were not statistically significant. CONCLUSION: Consideration of the Orbscan measurement of posterior corneal surface toricity may improve the prediction of the magnitude of refractive astigmatism.

Limbal stem cell deficiency following phototherapeutic keratectomy.

PURPOSE: To describe a case of limbal stem cell (LSC) deficiency following phototherapeutic keratectomy (PTK). METHODS: We analyzed the case of a 67-year-old man who developed LSC deficiency in his left eye following PTK for recurrent epithelial erosions. Predisposing factors included diabetes mellitus and rosacea. RESULTS: Surgical treatment consisted of debridement of the diseased corneal epithelium, followed by limbal autografting from the fellow eye. The cornea healed and remained transparent after 1 year. Histologic examination confirmed the diagnosis of LSC deficiency, showing the presence of goblet cells and inflammatory cells within the epithelium. CONCLUSION: The extensive corneal mechanical debridement and laser photoablation incurred during phototherapeutic keratectomy can cause clinical LSC deficiency in patients with predisposing external diseases.