Jessica H. Mathew

Quantified Histopathology of the Keratoconic Cornea

Purpose. This study systematically investigated and quantified histopathological changes in a series of keratoconic (Kc) corneas using a physiologically formulated fixative to not further distort the already distorted diseased corneas. Methods. Twelve surgically removed Kc corneal buttons were immediately preserved and processed for light and transmission electron microscopy using an established corneal protocol. Measurements were taken from the central cone and peripheral regions of the host button. The sample size examined ranged in length from 390 to 2608 &mgr;m centrally and 439 to 2242 &mgr;m peripherally. Results. The average corneal thickness was 437 &mgr;m centrally and 559 &mgr;m peripherally. Epithelial thickness varied centrally from 14 to 92 &mgr;m and peripherally from 30 to 91 &mgr;m. A marked thickening of the epithelial basement membrane was noted in 58% of corneas. Centrally, anterior limiting lamina (ALL) was thinned or lost over 60% of the area examined, whereas peripheral cornea was also affected but to a lesser extent. Histopathologically, posterior cornea remained undisturbed by the disease. Anteriorly in the stroma, an increased number of cells and tissue debris were encountered, and some of these cells were clearly not keratocytes. Conclusions. It is concluded that Kc pathology, at least initially, has a distinct anterior focus involving the epithelium, ALL, and anterior stroma. The epithelium had lost its cellular uniformity and was compromised by the loss or damage to the ALL. The activity of the hitherto unreported recruited stromal cells may be to break down and remove ALL and anterior stromal lamellae, leading to the overall thinning that accompanies this disease.

Fine Structure of the Interface between the Anterior Limiting Lamina and the Anterior Stromal Fibrils of the Human Cornea

PURPOSE To use transmission electron microscopy (TEM) to investigate further the ultrastructural details of the collagen fibrils linking the anterior limiting lamina (ALL; Bowmans membrane) of the human cornea to the anterior stromal lamellae. METHODS Six disease-free corneas from donors aged 42 to 82 years were fixed (2% glutaraldehyde in 80 mM sodium cacodylate) and processed for TEM within 72 hours postmortem. A series of overlapping images, at 10,204x magnification, of the central corneal ALL-stroma interface were assembled. The features of the terminal ends of fibril bundles at the interface with the anterior stroma were quantitatively assessed. RESULTS TEM revealed apparently terminating anterior stromal fibril bundles adjacent to the ALL. These terminating lamellae (7.8 per 100 mum) were embedded in an electron-dense material within the surrounding stromal matrix and were termed electron-dense formations (EDFs). The mean width of these stromal features was 1.6 mum. At intervals, anterior stromal lamellae approached the ALL and, in a shallow manner, inserted into the ALL. Such projections (5.4 per 100 mum) into the ALL were, on average, less than 1 mum. Numerous fibrils (29.8 per 100 mum) extended from the ALL into the stroma with a mean length of 0.8 mum. CONCLUSIONS The interface the ALL forms with the anterior stroma is complex, and TEM revealed at least three different types of fibrillar arrangements, which may serve optical requirements rather than provide a structural function.

Lamellar changes in the keratoconic cornea

The purpose of this study was to identify ultrastructural changes associated with ectasia and to determine the association between lamellar count and corneal thinning.

Recurrence or Re-emergence of Keratoconus – What is the Evidence Telling Us? Literature Review and Two Case Reports

Keratoconus may recur following penetrating or lamellar keratoplasty, but latency is considerably longer in the former. Since keratoplasty involves only partial excision of the cornea, and recent research strongly indicates the presence of the pathology in the peripheral host cornea, the reappearance of the pathology after a latency period is most likely due to migration of the disease from host to donor cornea. This notion is further corroborated by the shorter latency period in partial thickness keratoplasty, where more of the diseased host cornea remains in place. Other proposed causes for the recurrence of keratoconus, such as eye rubbing and contact lens wear, were reportedly not associated with a significant number of cases, and, therefore, are not the primary factor. Based on existing literature, it is concluded that, in post-keratoplasty keratoconus, the etiology stems from re-emergence of the disease rather than recurrence. Keratoconus patients in need of keratoplasty should be counseled on the possibility of the disease re-emerging.

Impact of lens care solutions on protein deposition on soft contact lenses

Purpose To evaluate the effect of four contemporary lens care solutions on total protein, total lysozyme, and active lysozyme extracted from three contact lens materials. Methods Adapted contact lens wearers were recruited at three sites, and all subjects were randomly assigned to daily wear of either etafilcon A, galyfilcon A, or senofilcon A for 2 weeks. Four lens care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and ClearCare) were used by each subject in random order with a new pair of lenses after a washout period between solutions of at least 4 days. After 2 weeks of daily wear, contact lenses were collected for analysis. Proteins were extracted from a subset of contact lenses (n = 568) and total protein, total lysozyme, and lysozyme activity were quantified using a modified Bradford assay, an enzyme-linked immunosorbent assay, and a micrococcal assay, respectively. Results Higher levels of total protein were extracted from etafilcon A when used with Biotrue compared to other solutions (p = 0.0001). There were higher levels of total lysozyme extracted from galyfilcon A lenses when used with PureMoist than with Biotrue or ClearCare (p < 0.006). Higher total lysozyme was extracted from senofilcon A when used with RevitaLens OcuTec compared to Biotrue (p = 0.002). Lower lysozyme activity was recovered from senofilcon A lenses with RevitaLens OcuTec when compared to all other care solutions (all p < 0.004). When Biotrue, PureMoist, or RevitaLens OcuTec were used, higher total lysozyme was extracted from galyfilcon A compared to senofilcon A (p < 0.01). When RevitaLens OcuTec was used, higher levels of active lysozyme were extracted from galyfilcon A compared to senofilcon A (p = 0.02). Conclusions The ability of lens care solutions to remove protein from lenses varies depending upon the care solution composition and also the polymeric make-up of the contact lens material.

Microbial Contamination of Contact Lens Storage Cases During Daily Wear Use.

Purpose To evaluate contact lens (CL) storage case contamination when used with four different CL care solutions during daily wear of three different CL materials. Methods A parallel, prospective, bilateral, randomized clinical trial (n = 38) was conducted. Subjects were randomly assigned to use one of three CL materials (etafilcon A, senofilcon A, or galyfilcon A) on a daily wear basis. Subsequently, each subject randomly used one of four different CL care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and CLEAR CARE) for 2 weeks, along with their respective storage cases. After every 2-week period, their storage cases were collected and the right and left wells of each storage case were randomized for two procedures: (1) microbial enumeration by swabbing the storage case surface and (2) evaluation of biofilm formation (multipurpose solution cases only) using a crystal violet staining assay. Results More than 80% of storage cases were contaminated when used in conjunction with the four CL care solutions, irrespective of the CL material worn. Storage cases maintained with CLEAR CARE (mean Log colony forming units (CFU)/well ± SD, 2.0 ± 1.0) revealed significantly (p < 0.001) greater levels of contamination, compared to those maintained with Biotrue (1.3 ± 0.8) and RevitaLens OcuTec (1.2 ± 0.8). Predominantly, storage cases were contaminated with Gram-positive bacteria (≥80%). There were significant differences (p = 0.013) for the levels of Gram-negative bacteria recovered from the storage cases maintained with different CL care solutions. Storage cases maintained with OPTI-FREE PureMoist (0.526 ± 0.629) showed significantly higher biofilm formation (p = 0.028) compared to those maintained with Biotrue (0.263 ± 0.197). Conclusions Levels of contamination ranged from 0 to 6.4 Log CFU/storage case well, which varied significantly (p < 0.001) between different CL care solutions, and storage case contamination was not modulated by CL materials.

Subjective Comfort and Physiology with Modern Contact Lens Care Products

Purpose To compare subjective comfort and ocular physiology with three multipurpose solutions (MPSs) to that of a peroxide-based system with three different soft contact lens materials. Methods Habitual soft contact lens wearers (n = 236) were enrolled at three sites and completed a washout period with no contact lens solution for ≥4 days. Subjects were randomly assigned to one of three lens types: etafilcon A, galyfilcon A, or senofilcon A. A new lens of the assigned type was worn for 10 to 14 days each while using one of four care solutions, in random order (A—polyaminopropyl biguanide + polyquaternium, B—POLYQUAD + Aldox, C—alexidine + polyquaternium-1, and D—hydrogen peroxide) with a washout period (≥4 days) between each solution. After each care solution, biomicroscopy was performed and subjective comfort was assessed using the Contact Lens User Experience (CLUE) questionnaire and other instruments including comfortable wear time (CWT). Linear mixed models were used for analysis. Comfort and biomicroscopy signs with each MPS were compared to that of the peroxide solution. Results Subjective CLUE Comfort score across all lens types with each MPS was not significantly different than with the peroxide solution (p = 0.98). There were no differences in CWT between each MPS and the peroxide solution for any lens type (range of differences: −0.8 to 0.8 h; all p ≥ 0.13). Six MPS/material combinations had no clinically meaningful change in corneal staining versus peroxide (<0.5 units); three combinations could increase staining by up to 0.57 units. Staining was <grade 1 for all combinations. Conclusions Comparable levels of comfort were found between the latest generation of MPSs compared to peroxide disinfection. Three MPS/material combinations tested could result in increased corneal staining of up to 0.57 units versus a peroxide solution. Overall, these data suggest the care systems investigated are generally appropriate for use with the contact lenses tested.