ABSTRACT
Keratoconus is a corneal ectatic disease characterized by progressive corneal thinning and protrusion. Its pathogenesis remains unclear. In vitro experiments have shown that mechanical stimulation may damage corneal stromal cells by increasing oxidative stress level and inflammatory factor concentration, resulting in a series of changes such as degradation of corneal extracellular matrix. Numerous clinical studies have confirmed that mechanical factors, including eye rubbing and eyeball compression caused by sleeping position, may play an important role in the process of keratoconus occurrence and development. They may affect the cornea by increasing the level of inflammatory factors in tear, causing changes in intraocular pressure, changing the biomechanical properties of the cornea, directly damaging corneal tissue by mechanical friction, and increasing the temperature of corneal epithelium. The main aim of this review was to describe the efforts of mechanical factors on corneal stromal cells, corneal tissue, and the possible role of mechanical factors in the pathogenesis of keratoconus, so as to provide a reference for the prevention and management of keratoconus.
ABSTRACT
AIM:To compare the early results of different kinds of transepithelial corneal collagen cross-linking (TE-CXL) in the treatment of progressive keratoconus.METHODS:Retrospective study.Twenty four patients (34 eyes) who were diagnosed with progressive keratoconus were divided into three groups.And 10 eyes in hypotonic CXL group received the treatment of hypotonic corneal collagen cross-linking;14 eyes in Ⅰ-CXL 5min group received the treatment of iontophoresis corneal collagen cross-linking for 5min,and 10 eyes from the Ⅰ-CXL 10min group received the treatment of iontophoresis corneal collagen cross-linking for 10min.Uncorrected distance visual acuity,corrected distance visual acuity,Pentacam,in vivo scanning laser confocal microscopy and anterior segment optical coherence tomography were examined before and after 1wk,1,3 and 6mo postoperatively.RESULTS:Six months postoperatively,corrected distance visual acuity (CDVA) (LogMAR) in Ⅰ-CXL 10min group increased by-0.21 ± 0.23 (t =2.735,P=0.026);Kmax decreased by 2.32± 5.21D (t=1.40,P=0.193),but the differences were not statistically significant.Uncorrected distance visual acuity (UDVA),CDVA and Kmax in hypotonic CXL group and Ⅰ-CXL 5min group were stable,the differences were not statistically significant.The depth of demarcation line was 152.7±42.9μ m in hypotonic CXL group,213.6±42.3μ m in Ⅰ-CXL 5min group and 237.0±46.4μ m in Ⅰ-CXL 10min group 1wk after the surgery,the differences among groups were statistically significant (F =7.111,P =0.006).The phenomenon of stroma cell apotosis-activate regeneration in Ⅰ-CXL 10min group was the most significant after the surgery.The changes of corneal thinnest thickness and endothelial cell density in three groups were stable.CONCLUSION:Three kinds of transepithelial CXL can halt the progression of keratoconus,among which the reaction of corneal tissue in iontophoresis CXL for 10min is the most obvious.
ABSTRACT
Objective To study normal flora components of conjunctiva, explore the relationship between normal flora and ocu- lar bacterial infections.Methods The data of 1 198 bacterial cultures of conjunctiva in non-infectious cataract patients were re- viewed and compared with the results of 985 specimens of conjunctivitis, keratitis and endophthalmitis from January 2000 to December 2004.Results Positive culture of conjunctiva in non-infectious cataract patients was 628 in 1 198 specimens (52.4%).These bacteria including gram-positive cocci and gram-neganve bacilli constituted the normal flora of conjunctiva. Staphylococcus epidermidis was the predominant bacteria (51.1%, 341/667) and its prevalence increased during this 5-year period.S.epidermidis and S.aureus were also the most frequently isolated pathogens in specimens of conjunctivitis, keratitis and endophthalmitis.The correlation was statistically significant between the positive rate in normal eye and conjunctivitis or keratitis in terms of these two species, but not statistically significant between normal eye and endophthalmitis.The resistance rate of normal flora of conjunctiva to ampicillin, amikacin, tobramycin, ciprofloxacin, and ofloxacin increased year by year. The resistance rate to gentamicin and the combination of two drugs decreased.The changing resistant pattern was similar in pa- tients with eye infection.Conclusions There is a close relationship between the normal flora S.aureus and S.epidermidis of conjunctiva and the bacterial infection of ocular surface, but no significant correlation between normal flora and the pathogen of endophthalmitis.