Comparison of bursting pressure after scleral tunnel incision sealed with sutures or an adherent ocular bandage in human globes.

OBJECTIVE: To evaluate the efficiency of a hydrogel adherent ocular bandage for sealing of scleral tunnel incisions in human eye globes. METHODS: A 4-mm scleral tunnel incision was made in each of 10 globes and bursting pressure was measured using the Seidel test to check for wound leakage. Globes were sealed using either two interrupted 10-0 nylon sutures (n = 5) or an adherent ocular bandage in the form of polyethylene glycol hydrogel (n = 5). Bursting pressure was then measured for a second time. RESULTS: Bursting pressure was significantly higher after wound sealing in both groups. There were no statistically significant differences in bursting pressure between the two groups before or after sealing. CONCLUSIONS: The adherent ocular bandage successfully protected the incision in ex vivo human globes immediately after surgery, with a sealing efficiency comparable to two nylon sutures, suggesting that it is a safe and effective alternative to conventional suturing.

A phase III, placebo controlled clinical trial of 0.5% levofloxacin ophthalmic solution for the treatment of bacterial conjunctivitis.

AIM: To compare the efficacy and safety of levofloxacin 0.5% ophthalmic solution (Quixin) with placebo for treatment of bacterial conjunctivitis. METHODS: In this prospective, randomised, placebo controlled, double masked, multicentre study, 249 patients with bacterial conjunctivitis received either 0.5% levofloxacin (n = 126) or placebo (n = 123) for 5 days, administered every 2 hours on days 1-2, then every 4 hours on days 3-5. Cultures were obtained and signs/symptoms evaluated at baseline, interim, and final visits. The end point was the last evaluable observation. Primary microbial outcomes were based on culture results; clinical outcomes were based on resolution of cardinal signs. RESULTS: 117 patients (60 levofloxacin, 57 placebo) were evaluated. Microbial eradication rates were significantly greater with levofloxacin at all time points, reaching 90% at end point. In a subgroup analysis, differences in eradication rates at end point were most pronounced in children but were also statistically significant for levofloxacin in adults. Clinical cure rates were significantly greater with levofloxacin at final visit and end point. Statistically significant differences favouring levofloxacin were measured at end point for resolution of conjunctival discharge, bulbar conjunctival injection, palpebral conjunctival injection, burning/stinging, itching, and photophobia. Adverse events were similar between groups. Safety composite scores analysed by age indicated significantly fewer children on levofloxacin experienced worsening symptoms. CONCLUSIONS: Levofloxacin 0.5% ophthalmic solution is safe and effective for treatment of bacterial conjunctivitis.

Two-year outcomes of intrastromal corneal ring segments for the correction of myopia.

OBJECTIVE: To evaluate the safety and efficacy of Intrastromal Corneal Ring Segments (ICRS) for the correction of myopia. DESIGN: Nonrandomized, comparative trial. PARTICIPANTS: Patients enrolled in the United States Food and Drug Administration phase II and phase III clinical trials of the ICRS had best spectacle-corrected visual acuity (BSCVA) of 20/20 or better, myopia of -1.00 to -3.50 diopters (D), and a cylindrical correction of 1.00 D or less as measured by manifest refraction. INTERVENTION: Surgical correction of myopia with an ICRS. MAIN OUTCOME MEASURES: Efficacy was assessed by predictability of refractive outcome (deviation from predicted cycloplegic refraction spherical equivalent), stability of refractive effect, and postoperative uncorrected visual acuity. Safety was assessed by adverse events, maintenance or loss of preoperative BSCVA, and induced manifest refraction cylinder. RESULTS: Four hundred fifty-two patients were enrolled at 11 investigational sites in both studies. Of the 454 surgical attempts, 449 received an ICRS in one eye (0.25, 0.30, and 0.35 mm in 148, 151, and 150 eyes, respectively). First surgeries were attempted in 452 patients. An ICRS was successfully implanted in 447 initial eyes, and 5 surgeries were discontinued. Of the five discontinued surgeries, three patients subsequently exited from the study, and two patients went on to have the ICRS implanted in the second eye, bringing the total number of successful implants to 449 patient eyes. Month 24 postoperative follow-up was completed on 358 patients (80%). At month 24, 328 of 354 eyes (93%) were within +/-1.00 D of predicted refractive outcome. Refraction changed by 1 D or less in 97% of eyes (421/435) between 3 and 6 months after implantation and in 99% (343/348) between months 18 and 24. Before surgery, 87% of eyes (390/448) saw worse than 20/40 uncorrected; 24 months after surgery, 55% of eyes (196/358) saw 20/16 or better, 76% (271/358) saw 20/20 or better, and 97% (346/358) saw 20/40 or better. Although two eyes (2/358; 0.5%) lost two or more lines of BSCVA at 24 months; visual acuity in both was 20/20 or better. Intraoperative complications included anterior corneal surface perforation (three eyes) and anterior chamber perforations (two eyes, one during an attempted exchange procedure); all healed spontaneously without suturing and without loss of BSCVA. The ICRS was repositioned in five eyes to increase correction. Postoperative complications in one eye each were infectious keratitis, shallow segment placement, and loss of two lines of BSCVA at two or more consecutive examinations (subsequently regained). CONCLUSIONS: The ICRS safely, predictably, and effectively reduced or eliminated myopia of -1.00 to -3.50 D. The refractive effect was stable over time.

Intrastomal corneal ring segments: reversibility of refractive effect.

PURPOSE: To evaluate the reversibility of refractive effect following removal of the ICRS (intrastromal corneal ring segments; Intacs). METHODS: Data from 34 eyes from which ICRS were removed during United States FDA Phase II and III clinical trials were evaluated with regard to segment size, loss or change of best spectacle-corrected visual acuity (BSCVA), any change of uncorrected visual acuity (UCVA), manifest spherical equivalent refraction, manifest cylinder refraction, stability of manifest cylinder refraction, and subjective visual symptoms. RESULTS: Out of 725 initial or contralateral eyes placed with the ICRS during Phase II and III clinical trials, segments were removed from 34 eyes (4.7%). Other than one (1/725, 0.1%) safety related ICRS removal, 30/725 (4.1%) were due to visual symptoms. ICRS removal was accomplished under topical anesthesia without complications in all eyes. The mean length of time the segments remained in the cornea after initial surgery was 10.3 +/- 5.4 months. At 3 months after ICRS removal, 21 eyes had monitored data available and were within +/-1 line or 10 letters of their preoperative BSCVA. Twenty eyes (20/21, 95%) returned to within +/-1.00 D of their preoperative manifest spherical equivalent refraction. All eyes had a stable refraction at the 3-month examination after removal, and a manifest spherical equivalent refraction within +/-1.00 D of their 1-month examination after removal. Nineteen eyes (19/21, 90%) returned to within +/-2 lines and 16 eyes (16/21, 76%) returned to within +/-1 line of preoperative UCVA. CONCLUSION: The ICRS (Intacs) was easily and safely removed, and eyes returned to preoperative refractive status within 3 months.

Goldmann applanation tonometry after intacs corneal ring segments(1).

PURPOSE: To evaluate the change of intraocular pressure (IOP) after implantation of Intacs (KeraVision) corneal ring segments using Goldmann applanation tonometry (GAT). SETTING: Multicenter clinical trial for U.S. Food and Drug Administration application conducted at 10 U.S. sites. METHODS: One-year follow-up data from a phase III clinical trial (n = 359) were reviewed. Intraocular pressure was measured by GAT preoperatively and 1 week and 1, 3, 6, and 12 months after Intacs implantation. The untreated fellow eyes were controls. Change from baseline (preoperative) IOP was calculated and tested for correlation with age and change from baseline in mean keratometry, manifest refraction spherical equivalent (MRSE), and pachymetry (central corneal thickness). Mean IOP in treated and control groups was compared through month 6. RESULTS: At all postoperative examinations, mean IOP in the Intacs eyes was significantly lower (-0.39 to -1.75 mm Hg; all P

Clinical characteristics of lamellar channel deposits after implantation of intacs.

PURPOSE: To report the frequency, location, and severity of biomicroscopically evident intrastromal deposits that may accumulate in the lamellar channel after implantation of Intacs corneal ring segments. SETTING: United States Food and Drug Administration multicenter clinical trial conducted at 10 sites. METHODS: Two-year follow-up data from a phase III clinical trial (N = 359) were reviewed. Examiners at 10 study sites described the location and severity (density) of deposits, grading severity on a standardized scale from absent (0) to severe (4). At 24 months, the incidence of deposits was 74% overall and 61%, 73%, and 89% with the 0.25, 0.30, and 0.35 mm Intacs, respectively (P <.001). The incidence increased sharply at first and more slowly after 6 months. RESULTS: At 12 months, deposits were located along the inner curvature of the segments in 47% of patients, along the outer curvature in 5%, along both inner and outer curvatures in 38%, and anterior to the segments in 10%. The severity of the deposits increased with segment thickness (P <.001 at 6, 12, and 24 months). CONCLUSIONS: Lamellar channel deposits occurred frequently after Intacs implantation. The incidence and density of deposits increased with segment thickness and duration of implantation. The presence of this material did not result in alteration of the optical performance of Intacs or anatomical or physiological corneal deterioration.

Diurnal stability of refraction after implantation with intracorneal ring segments.

PURPOSE: To investigate diurnal changes in visual acuity and refraction in myopic eyes implanted with intracorneal ring segments (ICRS). SETTING: University of California San Diego Shiley Eye Center, La Jolla, California, and Emory University Vision Correction Center, Atlanta, Georgia, USA. METHODS: This prospective study involved 2 groups of patients who had ICRS (Intacs) implantation and a follow-up of at least 6 months. The first group included 102 eyes of 51 bilaterally treated patients; the second group, 32 eyes of 16 unilaterally treated patients. Examinations including visual acuity, manifest refraction, and videokeratography were done in the morning and evening at least 9 hours apart on a single day. Refractive changes were analyzed by power vectors; multivariate statistics were used to determine the significance of change in any component of the spectacle prescription. RESULTS: In the bilateral treatment group, 97 eyes (95%) were within 1 line of spectacle-corrected visual acuity from morning to evening. The mean change in manifest refraction was -0.14 +0.08 x 4 and in spherical equivalent, -0.10 diopters (D) (sigma = 0.3; range -0.750 to +0.875 D). Ninety-six eyes (94%) had a change in refraction within 0.50 D of spherical equivalent. There was no significant change in corneal power (P =.20). In the unilateral treatment group, there was no significant difference between treated and untreated eyes in changes in spectacle-corrected visual acuity, manifest refraction, or corneal power and toricity (P.05). CONCLUSION: No clinically significant diurnal variation in visual acuity or manifest refraction was observed after ICRS implantation or in untreated paired eyes. Moreover, the data suggest less diurnal change in visual acuity and refraction after ICRS implantation.

A comparison of visual acuity, predictability, and visual function outcomes after intracorneal ring segments and laser in situ keratomileusis.

PURPOSE: To compare correction of low myopia by intrastromal corneal ring segments (ICRS) and by laser in situ keratomileusis (LASIK) with respect to early visual recovery and refractive outcomes. METHODS: Eighty-two eyes implanted with ICRS in a phase III study for US Food and Drug Administration review were matched with 133 eyes treated with LASIK by criteria of age (> 18 years, < 65 years), preoperative myopia (-1.00 to -3.50 diopters [D]), astigmatism (< or = 1.00 D), single treatment, and attempted full correction. Examinations were performed preoperatively and postoperatively at days 1 and 7 and months 1 and 3. Visual acuity and manifest refraction data were collected retrospectively. Visual function scores were assigned, and summarized results were compared. RESULTS: Uncorrected visual acuity was 20/20 or better at day 1 in 24% of eyes (20/82) after ICRS and in 55% of eyes (73/133) after LASIK, and at month 3 in 75% of eyes (58/77) after ICRS and in 67% of eyes (84/126) after LASIK. Spherical equivalent refraction at month 3 was within +/- 1.00 D of intended correction in 99% of eyes (76/77) after ICRS and in 96% of eyes (121/126) after LASIK. Excellent visual function scores were noted at month 3 in 90% of eyes (69/77) after ICRS and in 78% of eyes (98/126) after LASIK. CONCLUSION: Patients treated with LASIK showed better uncorrected visual acuity immediately following surgery; however, beyond 1 month, patients treated with ICRS achieved better uncorrected visual acuity that continued to improve with time. Visual function scores indicate that ICRS eyes see at higher levels of uncorrected visual acuity than LASIK eyes do with the same refractive error. The ICRS and LASIK were comparable in the correction of mild myopia.

One-year results from the phase III investigation of the KeraVision Intacs.

BACKGROUND: Limitations of the surgical correction for myopia include inaccuracy, instability, treatment of the central optical zone, and lack of reversibility. KeraVision Intacs offer an alternative that addresses these shortcomings. METHODS: We present 1 year of follow-up information on 95 subjects enrolled in the United States Food and Drug Administration Phase III clinical trials. RESULTS: At 1 year, 99% of patients (89 of 90) had 20/40 uncorrected vision or better. Ninety-two percent of eyes (83 of 90) were within 1.00 D of intended correction and 76% of eyes (68 of 90) were within 0.50 D of intended correction. Stability was achieved at 3 months, with 96% of subjects (86 of 90) having less than 1.00 D of change from their previous examination. In a substudy, 89% eyes (58 of 65) varied within +/- 0.50 D over the course of a day. Corneal curvature changed as predicted, resulting in a prolate aspheric shape within the central optical zone. Most complications or adverse events experienced were managed with additional medication or surgical intervention, resulting in a favorable outcome for subjects. CONCLUSIONS: KeraVision Intacs are effective, predictable, stable, and safe. This additive technique may also offer reversibility.

Pneumotonometry versus Goldmann tonometry after laser in situ keratomileusis for myopia.

PURPOSE: To assess the reliability of intraocular pressure (IOP) measurement by Goldmann applanation tonometry (GAT) versus pneumotonometry in patients after laser in situ keratomileusis (LASIK) for myopia. SETTING: Shiley Eye Center, University of California San Diego, La Jolla, California, USA. METHODS: In this prospective study, 31 eyes of 17 patients were evaluated before and 1 month after having LASIK for myopia. A masked observer measured preoperative and postoperative IOP by GAT centrally and by pneumotonometry at the center and the periphery of the cornea. Central corneal thickness and curvature were evaluated. RESULTS: Preoperative IOP showed a good correlation between GAT and pneumotonometry values (r = 0.82). Mean postoperative IOP by GAT was lower by 3.8 mm Hg +/- 2.2 (SD) (26.3% +/- 15.2%) than by pneumotonometry: 2.3 +/- 2.8 mm Hg (15.4% +/- 10.7%) (P = .01). There were no statistically significant differences in central IOP versus peripheral IOP measured by pneumotonometry (P = .4). Regression analysis showed no statistically significant differences in IOP as a function of change in corneal thickness or change in corneal curvature with either device. CONCLUSION: Postoperatively, there was a decrease in IOP measured by central GAT that was statstically significant. Differences in pneumotonometry were less substantial, with greater reliability of pneumotonometry than GAT after LASIK.

Intraocular pressure measurement in patients with instrastromal corneal ring segments.

PURPOSE: To study the measurement of intraocular pressure after implantation of Intacs (ICRS) intrastromal corneal ring segment, a device that is positioned circumferentially in the peripheral corneal stroma to correct myopia. The device changes the corneal curvature by shortening arc length. Since the ring segments are made of polymethylmethacrylate, this may cause localized changes in corneal elasticity so intraocular pressure measurement may be affected. METHODS: We measured the intraocular pressure of 12 eyes in which the ICRS had been in place longer than 6 months. We used Goldmann applanation and Tono-Pen tonometers over the central corneal and the paracentral corneal areas. We also measured the intraocular pressure with the Tono-Pen applanated directly over the intrastromal corneal ring segments. RESULTS: The resulting intraocular pressure measurements were similar for the Tono-Pen tonometer readings over the central cornea, paracentral cornea, and the Goldmann applanation tonometer readings over the central cornea (P < .01). Our measurements using the Goldmann applanation tonometer on the paracentral corneal area showed artificially elevated intraocular pressure in the 40 to 60 mmHg range. We were not able to obtain consistent results when we measured the intraocular pressure using the Tono-Pen on the corneal area directly overlying the intrastromal corneal ring segment implants. CONCLUSION: Consistent intraocular pressure measurements on eyes with the ICRS can be obtained with the Goldmann applanation tonometer over the central corneal area or with the Tono-Pen tonometer over the central or paracentral corneal areas.

Topographic predicted corneal acuity with intrastromal corneal ring segments.

PURPOSE: To evaluate predicted optical quality of the central anterior corneal surface before and after the intrastromal corneal ring segment (ICRS) refractive procedure using a clinical videokeratoscope and software index developed for that purpose. METHODS: Predicted corneal acuity, a topographically derived index provided with the EyeSys System 2000 videokeratscope, representing potential optical quality of the cornea, was assessed preoperatively and at postoperative month 3 in 94 eyes that received an ICRS to treat -1.00 to -6.00 D of myopia. Predicted corneal acuity was calculated by determining the difference between a measured cornea and its best-fit ellipses for reflected ring circumferences within the central 3 mm diameter zone. RESULTS: Preoperative predicted corneal acuity was 20/10 in 92 of 94 eyes (98%). At month 3 after the ICRS procedure, 48 (51%) of moderately myopic eyes were corrected to 20/20 or better, 96% (90 eyes) were corrected to 20/40 or better, and 98% of eyes (92 eyes) had a predicted corneal acuity of 20/10. For the eyes with a predicted corneal acuity of 20/10, spectacle-corrected visual acuity was normally distributed between 20/10 and 20/25. CONCLUSION: Predicted corneal acuity did not change significantly from baseline in eyes with an ICRS. This suggests that topographic irregularities in the central 3 mm of the cornea detectable by predicted corneal acuity software were not induced in the central cornea with the ICRS.

Comparison of contrast sensitivity in different soft contact lenses and spectacles.

PURPOSE: To compare the visual performance of soft contact lenses and spectacles. METHODS: Twenty eyes of ten patients were examined. Each patient was fit with Acuvue, Cibasoft, and Biomedics contact lenses in random order. LogMar visual acuity and contrast sensitivity using the VectorVision CSV-1000 were measured. RESULTS: There was no significant difference in visual acuity between any contact lenses (P=.15). Contrast sensitivity at 12 cycles/degree was significantly lower for the Cibasoft lens compared to spectacles (P=.04). There was no significant difference between spectacles and contact lenses for remaining spatial frequencies (P=.07-.35). CONCLUSIONS: Visual acuity appears to be an insensitive method for evaluating soft contact lenses. The lathe-cut manufacturing process may be responsible for reduced visual function compared to cast-molded lenses. Further study in this area is needed.

Studies of intrastromal corneal ring segments for the correction of low to moderate myopic refractive errors.

PURPOSE: Intrastromal corneal ring segments (ICRS) were investigated for safety and reliability in the correction of low to moderate myopic refractive errors. METHODS: Initially, 74 patients with spherical equivalent refractive errors between -1.00 and -4.25 diopters (D) received the ICRS in 1 eye. After 6 months, 51 of these patients received the ICRS in the contralateral eye. The total number of eyes investigated was 125. The outcome measures were uncorrected and best-corrected visual acuity, predictability and stability of the refraction, refractive astigmatism, contrast sensitivity, and endothelial cell morphology. RESULTS: The 89 eyes with 12-month follow-up showed significant improvement with uncorrected visual acuities of 20/16 or better in 37%, 20/20 or better in 62%, and 20/40 or better in 97%. Cycloplegic refraction spherical equivalents showed that 68% of the eyes were within +/- 0.50 D and 90% within +/- 1.00 D of the intended correction. Refractive stability was present by 3 months after the surgery. Only 1 patients had a loss greater than 2 lines or 10 letters of best spectacle-corrected visual acuity, but the patient's acuity was 20/20. Refractive cylinder, contrast sensitivity, and endothelial cell morphology were not adversely affected. The ICRS was removed from the eyes of 6 patients. Three removals were prompted by glare and double images occurring at night; 3 were for nonmedical reasons. All patients returned to within +/- 1.00 D of their preoperative refractive spherical equivalent, and no patients lost more than 1 line of best corrected visual acuity by 3 months after ICRS removal. CONCLUSION: The ICRS safely and reliably corrects myopic refractive errors between -1.00 and -4.50 D.

A synchrotron x-ray diffraction study of developing chick corneas.

To study some ultrastructural aspects of developing chick corneas we performed a synchrotron x-ray diffraction analysis of 22 specimens obtained daily from developmental day 10 through day 19. Before day 12 of development in chicks we were unable to detect a meridional x-ray diffraction pattern from cornea. Neither were we able to record a first-order equatorial x-ray reflection at this time. Normally, these reflections are present in corneal x-ray patterns, arising from, respectively, the periodic axial electron density of fibrillar collagen and the lattice-like arrangement of the fibrils. By day 12 of development we could detect the third- and fifth-order meridional reflections (indicating increased amounts of collagen) and a first-order equatorial reflection (implying that more collagen was regularly arranged). The third- and fifth-order meridional reflections became more intense as the tissue matured, suggestive of a continued deposition of fibrillar collagen, and the scattering angle of the interfibrillar maximum increased, suggesting that regularly arranged collagen was becoming more closely packed with maturation. In embryonic chick corneas, the establishment of an orderly, fairly compacted matrix of collagen fibrils may be one of the main events underlying the acquisition of corneal transparency.

The intrastromal corneal ring segments. Phase II results for the correction of myopia.

OBJECTIVE: The purpose of the study was to evaluate the safety and efficacy of the intrastromal corneal ring segments (ICRS) for the correction of myopia. DESIGN: A 2-year phase II clinical trial of ICRS was initiated in May 1995. The investigational plan specifies that 150 patients with sighted eyes, requiring myopic corrections from -1.00 to -6.00 diopters (D), will each receive ICRS in 1 eye. The patient population will be divided into approximately five patients per ICRS thickness (0.25, 0.30, 0.35, 0.40, and 0.45 mm) per site. Six investigational sites are participating in the trial. PARTICIPANTS: Fifty-nine men and 43 women requiring myopic corrections were enrolled at four U.S. investigational sites. These 102 patients each received the ICRS product in 1 eye. INTERVENTION: Correction of myopia. MAIN OUTCOME MEASURES: Efficacy of ICRS was assessed with respect to the trial endpoints of predictability of refractive effect, uncorrected visual acuity (UCVA), stability of UCVA, maintenance of best spectacle-corrected visual acuity and stability of refractive effect. RESULTS: As shown by the available month-3 data (99 patients; all device thicknesses), 95 (96%) of 99 patients had a UCVA of 20/40 or better. Ninety-eight (99%) of 99 patients were within 2 lines of their preoperative best spectacle-corrected visual acuity. The average change (with standard error) in cycloplegic refraction (spherical equivalent) achieved by ICRS thickness was -1.27 +/- 0.09 D (0.25 mm), -2.13 +/- 0.16 D (0.30 mm), -2.56 +/- 0.15 D (0.35 mm), -3.77 +/- 0.37 D (0.40 mm) and -4.16 +/- 0.24 D (0.45 mm). Seventy-seven percent (76/99) of the patients were within +/-1.00 D of their intended correction. When the ICRS was removed in two cases, both patients returned to within 0.75 D of their preoperative manifest refraction. CONCLUSIONS: The ICRS appears to be a viable and effective alternative for the treatment of myopia. Additionally, as indicated by the explant data, the ICRS's refractive effect may be reversible upon removal of the device.

Proteoglycans contain a 4.6-A repeat in corneas with macular dystrophy: II. Histochemical evidence.

PURPOSE: Synchrotron x-ray diffraction experiments indicate that corneas with macular corneal dystrophy (MCD) contain unusual 4.6-A periodic repeats thought to reside in proteoglycans or glycosaminoglycans. Recently the 4.6-A x-ray reflection was found to be significantly diminished after incubation of MCD specimens in buffer containing chondroitinase ABC or N-glycanase. We examined the sulfated proteoglycans in these glycosidase-digested MCD corneas. METHODS: Transmission electron microscopy was used in conjunction with cuprolinic blue-staining for sulfated proteoglycans. RESULTS: Incubation of an MCD specimen in enzyme buffer left both small and large proteoglycan filaments in the stromal matrix, whereas incubation in the presence of chondroitinase ABC removed these molecules from the tissue. Incubation in buffer containing N-glycanase, on the other hand, removed the large proteoglycan filaments from the MCD stroma but left unaffected the small collagen-associated proteoglycans. CONCLUSION: These results are consistent with the interpretation that 4.6-A periodic repeats in MCD corneas reside in large sulfated proteoglycan filaments (or aggregates thereof) that may contain chondroitin/dermatan sulfate and keratan sulfate or keratan components.

Organization of collagen in the lyophilized cornea.

PURPOSE: To investigate the organization of collagen fibrils in the lyophilized cornea. METHODS: Freshly harvested porcine corneas (n = 10) were lyophilized and examined by synchrotron x-ray diffraction and transmission electron microscopy. RESULTS: Collagen fibrils are highly compacted in lyophilized corneas. They become more widely spaced when the tissue is rehydrated, however, the distribution of imbibed water throughout the stroma is not necessarily homogeneous within an individual cornea, nor is it always similar in specimens that have been rehydrated to similar levels. In lyophilized corneas, the mean center-to-center interfibrilar spacing of the regularly arranged collagen reaches levels found in freshly thawed porcine corneas (between 74% and 78% water by weight) when between 74.3% and 81.6% of the rehydrated lyophilized cornea's weight is water. CONCLUSION: Regularly arranged collagen fibrils are able to reapproximate their original spacings if lyophilized corneal tissue is rehydrated, although the manner in which imbibed water is distributed is somewhat unpredictable.

Macular corneal dystrophy type II: multiple studies on a cornea with low levels of sulphated keratan sulphate.

We investigated an individual macular corneal dystrophy (MCD) type II cornea from a 42-year-old woman with markedly reduced antigenic keratan sulphate levels. A characteristic 4.6 A X-ray reflection was evident, and the mid-stroma contained 30% less sulphur than normal. Close packing of collagen was restricted to the superficial stroma. Abnormally large proteoglycan filaments were noted throughout the extracellular matrix and Descemet's membrane's posterior non-banded zone, but not its anterior banded zone. Small, collagen-associated stromal proteoglycans were susceptible to digestion with chondroitinase ABC, but not keratanase I or N-glycanase. On occasion, collagen fibrils ranged in size from 20 nm to 58 nm, with preferential diameters of 34 nm and 42 nm. Corneal guttae were evident, as were numerous endothelial inclusions, most probably due to intracellular fibrillogranular vacuoles similar to those found in the stroma. The endothelium expressed reduced anti-keratan sulphate labelling.