Biochemical studies on human corneal proteoglycans —a comparison of normal and keratoconic eyes

Human corneas from normal (healthy) donors and patients with keratoconus were either metabolically labelled under organ culture conditions or investigated without preincubation. The sulfated proteoglycans were isolated from a 4M guanidinium chloride/2% Triton X 100 extract. Two predominant proteoglycans were obtained from normal cornea after digestion of total sulfated proteoglycans with chondroitin ABC-lyase or endo--galactosidase. One had an overall mass of 150 kDa, two dermatan sulfate chains (M _r50 kDa) with an iduronic acid content of 24%–28% and, after chondroitin ABC-lyase digestion, a core protein of 48 kDa. The other proteoglycan had an overall mass of 110 kDa, one keratan sulfate chain of 60 kDa and, following endo--galactosidase (keratanase) digestion, a core protein of 46 kDa. Each proteoglycan population was further fractionated into two subpopulations by chromatography on concanavalin A-Sepharose. The dermatan sulfateand keratan sulfate-containing proteoglycans isolated from keratoconic and healthy cornea had comparableM _r values and core proteins with identical molecular weights, but the ratio of dermatan sulfate/keratan sulfate proteoglycan was increased in keratoconic cornea and the keratan sulfate chains of two keratan sulfate proteoglycans from keratoconic cornea were considerably shorter (M _r 44 and 33 kDa) than those from normal corneas.     

Monitoring of central corneal thickness after phacoemulsification—comparison of statical and rotating Scheimpflug pachymetry, and spectral-domain OCT

AIM: To explore the possibility of deploying three contactless devices (static and rotating Scheimpflug technology, spectral domain optical coherence tomography) for measuring central corneal thickness (CCT) in preoperative and postoperative examinations of cataract patients. METHODS: Totally 72 patients who had undergone surgery without complications were selected. The CCT was measured prior to the operation, as well as on the first, 5th-7th and 28th day following the operation using the Nidek NT 530-P, Sirius®, and Topcon OCT-2000 devices. RESULTS: A significant postoperative increase and subsequent decrease in CCT was identified with all three devices. The correlations were highly significant and thus reflect a very good degree of comparability at all times with the exception of the rotating Scheimpflug camera. The postoperative results from the latter differed significantly from the other devices. The correlations were Sirius/Topcon (P=0.010) and Sirius/Nidek (P<0.0005). No statistically significant difference could be identified in the comparison between Topcon and Nidek (P=0.056). CONCLUSION: All three devices are suitable for postoperative monitoring of CCT. The measurement results are only comparable to a limited extent and not interchangeable in the course of treating a single patient. This is due to the different imaging technology used in the devices and the resulting modalities for conducting the measurements.     

Repeatability， reproducibility and agreement when measuring central corneal thickness with SS-1000 swept-source optical coherence tomography and ultrasound pachymetry

ObjectiveTo assess the repeatability of central corneal thickness （CCT） measurements in healthy eyes by comparing measurements obtained with an SS-1000 swept-source optical coherence tomography （SS-1000 OCT） or by ultrasound pachymetry （USP）; to evaluate the agreement between these two devices. MethodsIn this prospective study, CCT was recorded after consecutive measurements with SS-1000 OCT and then with USP by a single skilled operator in 62 right eyes of healthy subjects. Intraclass correlation coefficient （ICC）, Bland-Altman plots and repeated-measures analysis of variance （ANOVA） were used to evaluate the repeatability of SS-1000 OCT. Paired t-tests and Bland-Altman plots were used to evaluate the agreement between the two devices. ResultsThe ICC of the SS-1000 OCT measurements was 0.999. Bland-Altman plots showed excellent agreement between any two of the three measurements （95％ limits of agreement were -2.4 to 1.8 µm, -2.8 to 2.1 µm, and -2.8 to 2.7 µm）. There was no statistical significance found with repeated-measures ANOVA. The mean values of CCT obtained from the SS-1000 OCT and USP were 534.38±24.52 µm and 538.40±25.36 µm, respectively. 95％ limits of agreement were -12.6 to 4.5 µm for these two devices. ConclusionThe SS-1000 OCT shows excellent repeatability of CCT measurements in healthy eyes. High agreement between CCT measurements suggests that SS-1000 OCT and USP can be used interchangeably in normal subjects.     

A five-year follow-up study of posterior corneal curvature and central corneal thickness after LASIK using OrbscanⅡ

Objective To study the long-term （five-year follow-up） changes in posterior corneal curvature and central corneal thickness by using the OrbscanⅡ topographer in patients who had undergone laser in situ keratomileusis （LASIK） for myopia. Methods Forty-eight eyes of 48 patients who had undergone LASIK for myopia were included in a retrospective observational case series study. The mean preoperative refractive error was -6.25±2.87 D. The preoperative and postoperative changes in the posterior corneal curvature and central corneal thickness of each eye were measured by OrbscanⅡ. The posterior corneal curvature was obtained from the central 6mm zone of the OrbscanⅡ. The postoperative follow-up period was at 1, 3, 6, 9, 12, 24, 36 and 60 months. Using SPSS 16.0 software, a comparison of the least-significant difference （LSD） pairwise was used to analyze the difference in the posterior corneal curvature and central corneal thickness at each follow-up visit. Results ①The posterior corneal curvature was higher in the 1st month postoperatively compared to preoperative curvature （t=8.211, P<0.01）. There was no statistically significant difference for the change in posterior corneal curvature from the 1st month to the 9th month （P>0.05）. The posterior corneal curvature slowly decreased over time from the 9th month to the 24th month （the values of t were -4.640 and -2.659, the values of P were <0.001 and 0.014）. The posterior corneal curvature did not become stable until after the 24th month （P>0.05）. ②The central corneal thickness was lower in the 1st month postoperatively than preoperative thickness （t=10.08, P<0.01）. The central corneal thickness slowly increased over time from the 1st month to the 9th month （the values of t were -5.402, -4.428 and -2.334, the values of P were <0.001, <0.001 and 0.027）. The central corneal thickness did not become stable until after the 9th month （P>0.05）.③The posterior corneal curvature was correlated with corneal thickness （r=-0.703, P<0.01）. Conclusion The posterior corneal curvature and the central corneal thickness both increase shortly after LASIK surgery and stabilize after this initial period. There is a negative correlation between posterior corneal curvature and central corneal thickness.     

Surgical Excision, Cryotherapy, Autolimbal Transplantation and Mitomycin-C in Treatment of Conjunctival–corneal Intraepithelial Neoplasia

Purpose To report surgical excision, cryotherapy, autologous conjunctival–limbal transplantation and topical mitomycin C (MMC) in the patient with extensive conjunctival–corneal intraepithelial neoplasia. Methods Case report and literature review. Results A 75-year-old woman was referred to our department with the diagnosis of conjunctival–corneal neoplasia. Slit-lamp microscopic examination revealed an extensive papilliform tumoral mass invading the limbus at 360-degrees, and bulbar conjunctiva and cornea. Visual acuity was finger counting from 2 m in the right eye and 20/20 in the left eye. We performed total surgical excision, cryotherapy and autologous conjunctival–limbal transplantation in the right eye. Mitomycin-C 0.02% eye drops four times a day were prescribed for 4 weeks after the surgery. After the treatment, the visual acuity increased to 0.7 in the right eye. Corneal epithelium completely healed within 1 week after the surgery. No corneal epithelium-related problem or neoplasia recurrence were noted during the 2-year follow-up period. Conclusions This technique may be useful in reconstruction of eyes with extensive neoplastic involvement of the conjunctiva, limbus, and cornea. In addition, mitomycin C drops may be useful in preventing postoperative recurrence of conjunctival–corneal intraepithelial neoplasia.