Visual acuity chart is an important tool in ophthalmic clinic and vision research. This paper aims to expound the misunderstanding of vision records and the vision statistical issues in some of the research papers， and to further interpret the core design of visual acuity chart. This would be helpful to make the use of visual acuity chart more scientific and standard， and to get more accurate visual records and statistical results， so as to make the visual acuity chart to be better served in the vision screen， ophthalmic clinic， and vision research.

Corneal collagen cross-linking （CXL） technique has evolved for more than 10 years and used for ectasia disease as a routine treatment in Europe. It has been proved to be a very effective technique to halt the progression of cornea ectasia diseases as well as a very promising technique for other clinical applications in ophthalmology. Currently the treatment is under the approval by SFDA. Being a nation， extremely lacking of donor corneas， high volume of corneal refractive surgery， sever infective keratitis still being one of the main cause to blindness， we should attach importance to understand CXL technique as well as advocate and promote its clinical application and research.

Objective  To discuss the critical issues of the dynamics of UV-light-photoinitiated cross-linking in corneal collagen （CXL） and to confirm the dynamics of riboflavin （vitamin-B2） absorption under UV light. Methods  Coupled dynamic equations are numerically solved and analytic formulas are derived for three critical parameters： the safe depth （z*）， the safe dose （E*） and the cross-linking time （t*）. Time-dependent absorption of UV light due to the depletion of the initiator is measured and shown by a dynamic spectrum of riboflavin. The critical issues of CXL are explored by seven parameters： the extinction coefficient， concentration， the penetration depth of the riboflavin， the UV light intensity and dose， irradiation duration， and corneal thickness. Results The safe dose （E*） has a wide range from 2.3 to 8.2 （J/cm2） for riboflavin concentrations of 0.1% to 0.2% and penetration depths of 0.02 to 0.04 cm. It is shown by mathematical modeling that a higher light intensity and extinction coefficient lead to shorter t* for a given cross-linking depth， while t* increases with corneal thickness （z*）. The safety depth decreases as a function of the extinction coefficient and initiator concentration. Conclusion  A new cross-linking protocol is suggested based on new findings， which include the safe depth （z*）， the safe dose （E*）， the cross-linking time （T*）， and the safe riboflavin concentration.

Objective  To evaluate the efficacy of corneal collagen cross-linking （CXL） with a hypo-osmolar riboflavin in keratoconic corneas （corneal thickness less than 400 μm）. Methods This retrospective study collected a total of eight eyes of eight keratoconic patients. All patients underwent CXL used a hypo-osmolar riboflavin solution after epithelial removal. The best corrected visual acuity （BCVA）， manifest refraction， the thinnest corneal thickness （TCT）， and the endothelial cell density （ECD） were evaluated at before and 6， 12 months after CXL. Results The TCT was 418.0 μm before treatment and reduced to 383.5 μm after the removal of the epithelium. After CXL， the thickness decreased to 414.0 μm at the last follow up. Before treatment， the K-value of the apex of the keratoconus corneas was 58.2 D， and was 58.9 D at 12-month. The BCVA was 0.52 logarithm of the minimal angle of resolution before treatment， and increased to 0.46 logarithm at the last follow up. The ECD was 2 698.5 cells/mm2 before treatment， and was 2 685.9 cells/mm2 at 12-month after treatment. Conclusion CXL with a hypo-osmolar riboflavin is one of safe and effective treatment in keratoconic eyes with thin corneas （corneal thickness less than 400 μm）.

Objective  Evaluate the safety and effectiveness of transepithelial， very high fluence accelerated corneal collagen cross-linking （A-CXL） in primary keratoconus. Methods  Self-control study. Thirteen primary keratoconus eyes of 13 patients were treated with transepthelial， very high fluence A-CXL with a UVA intensity of 45 mW/cm2， an irradiation time of 2 min 40 s， and a total energy of 7.2 J/cm2. Routine ophthalmologic examination， UCVA， BCVA， refractive error， corneal keratometry， anterior and posterior elevation （AE and PE）， index of vertical asymmetry （IVA）， minimum corneal thickness （CT）， compensated intraocular pressure （IOPcc）， endothelial cell density （ECD） were evaluated pre-operatively and 7-day， 1-month， 3-month， 6-month， 12-month post-operatively. Results  The UCVA （F=6.111， P＜0.01） and BCVA （F=9.734， P＜0.01） showed a statistically significant improvement by 12-month post-operatively. The decrease in spherical lens （F=5.871， P＜0.05）， steeper K-value （F=19.651， P＜0.05）， Kmax （F=3.253， P＜0.05）， AE （F=23.958， P＜0.01）， PE （F=20.832， P＜0.01） and IVA （F=4.068， P＜0.05） were statistically significant. CT （F=4.180， P＞0.05）， ECD （F=1.812， P＞0.05） and IOPcc （F=0.332， P＞0.05） were without significant change. Conclusion  Transepithelial， very high fluence A-CXL is safe and effective in treating primary keratoconus.

Objective  To observe the therapeutic effects of riboflavin-ultraviolet A（UVA） corneal collagen cross-linking （CXL） performed with a transepithelial method for progressive keratoconus. Methods  This was a prospective case series study. Thirty-six patients （54 eyes） with progressive keratoconus who underwent transepithelial corneal collagen cross-linking surgery were reviewed. The procedure was performed under topical anesthesia using a transepithelial corneal collagen cross-linking instrument （SOFT， Italy）. riboflavin （0.25%） was imported into the cornea for 10 minutes （current 1.0 mA）. The irradiation was performed for 9 minutes using a solid-state UVA illuminator at 370 nm and an irradiance of 10 mW/cm2. The average follow-up time was 14.1±2.3 months. Corneal epithelium healing was observed 1 day after surgery. There were no complications such as corneal ulcer， corneal dissolution， corneal epithelium mist opacity （haze） or severe pain. Uncorrected visual acuity （UCVA）； best corrected visual acuity （BCVA）； intraocular pressure； corneal curvature； corneal thickness； corneal topography； endothelial cell count； corneal biomechanical properties and in vivo confocal microscopy were evaluated at baseline and at 1， 3， 6， 12 months postoperatively. Data were analyzed using a paired samples t test. Results  The day after surgery， the corneal epithelium had opaque spots due to edema but the condition improved by the second day. Postoperative 12 months， UCVA and BCVA increased from 4.27±0.23 to 4.41±0.20 （t=3.962， P<0.01） and from 4.69±0.23 to 4.82±0.14 （t=3.507， P<0.01）， respectively. Interim analysis of treated eyes showed a flattening of the steepest simulated keratometry value （K-max） and astigmatism by an average of 1.25±0.68 diopters （t=9.351， P<0.01） and 0.30±0.21 diopters （t=7.227， P<0.01）. The deformation amplitude decreased from 1.21±0.11 mm to 1.16±0.12 mm（t=4.131， P<0.01）. Intraocular pressure， endothelial cell count and central corneal thickness did not change significantly. Conclusion  Transepithelial cornea

Objective  To evaluate the efficacy of accelerated corneal collagen cross-linking （a-CXL） in patients with incurable bullous keratopathy. Methods  This was a retrospective， nonrandomized study. Patients with incurable bullous keratopathy who were consecutively diagnosed at the hospital of the Affiliated Xiamen Eye Center of Xiamen University from March 2011 to March 2013 were included in the study. Patients received accelerated CXL surgery. The following parameters were accessed preoperatively and 1 week， 1 month and 3 months postoperatively： ocular pain index using the Numeric Rating Scale （NRS）， visual acuity， noncontact tonometer measurement， slit-lamp examination for corneal epithelium defects and corneal opacity， and anterior-segment OCT for corneal thickness. Differences between groups were analyzed using one-way ANOVA. Results  Thirteen eyes were chosen and underwent a-CXL. The ocular pain index was 7.6±1.2 on average preoperatively and significantly decreased to 5.3±1.6 at 1 month and to 5.5±1.7 at 3 months postoperatively （F=8.593， P<0.01）. The corneal epithelial staining score was 4.5±0.5 preoperatively and was significantly reduced to 3.4±0.6 at 1 week and to 2.8±0.9 at 1 month （F=12.580， P<0.01） postoperatively. The corneal transparency score was 2.7±0.5 preoperatively and improved significantly to 1.9±0.5 at 1 week and 2.2±0.6 at 1 month （F=6.122， P<0.01） postoperatively. Preoperative corneal thickness was 862.2±146.4 μm and decreased significantly to 707.5±92.7 μm at 1 week and 718.8±47.2 μm at 1 month （F=5.859， P<0.01） postoperatively. At 3 months postoperatively， the corneal epithelial staining score， corneal transparency score and corneal thickness were not significantly different from preoperative conditions. Conclusion  Accelerated CXL significantly reduces ocular pain， improves corneal epithelium defects， corneal transparency and corneal thickness within a short period postoperatively. However， a-CXL do not seem to have long-lasting effects in patients with bullous keratopathy.

Objective  To investigate the clinical characteristics and evaluate photodynamic therapy treatment combined with intravitreal injection of Lucentis for choroidal neovascularization secondary to angioid streaks. Methods  This was an interventional retrospective analysis of 21 patients （42 eyes）. For clinical data， best corrected visual acuity （BCVA）， fundus appearance， fundus fluorescence angiography （FFA）， indocyanine green angiography （ICGA） and optical coherence tomography （OCT） were assessed. Twenty-two eyes of 18 patients with macular choroidal neovascularizaiton （CNV） were treated first with photodynamic therapy （PDT） and then with an intravitreal injection of Lucentis. The patients were followed up for at least 12 months. Another injection was given if one of the following appeared： decreased visual acuity， new macular lesions， subretinal or intraretinal fluid， or CNV leakage. Data were analyzed using an independent-samples t test or a paired-samples t test. Results  Both eyes of all 21 patients were involved. Only 5 patients （24%） had complications with hologathy. Males were more affected （76%）. Of all the patients， 18 cases （86%） were diagnosed with CNV secondary to AS. BCVA was much worse in eyes with CNV. At the final follow-up after the combination treatment， BCVA had improved 10.4 characters. OCT showed macular retinal thickness decreased from 338.4±55.2 μm at baseline to 212.6±36.2 μm. FFA（ICGA） showed CNV leakage in 15 eyes （68%） had disappeared completely， and 5 eyes had scar staining. All patients received 1 treatment of PDT and a mean 3.2 intravitreal injections. Macular subretinal hemorrhage presented in 1 patient after PDT， but was absorbed completely after intravitreal injection. Five patients presented with transient elevated intraocular pressure and 4 patients had subconjunctival hemorrhage but all recovered quickly. No other ocular or adverse reactions occurred. Conclusion  Angioid streaks present a special fundus appearance， and FFA（ICGA） is valuable in the diagnosis. A considerable propo

Objective  To assess the clinical application of the Keratograph 5M in dry eye patients. Methods  In a noninterventional， cross-sectional study， 135 eyes from 70 patients who were diagnosed with dry eye from October to November 2013 were recruited. The ocular surface disease index （OSDI）， Schirmer Ⅰ test （SⅠT） and meibomian secretion were measured. Tear meniscus height， tear film break-up time （BUT） and the meibomian glands were observed with the Keratograph 5M. A Pearson correlation and linear regression were used to study the correlation between the Keratograph 5M and traditional examinations， and the relationship between scores for the meibomian gland status compared to the ocular surface disease index and tear film break-up time. An interclass correlation coefficient was used to evaluate the repeatability of the Keratograph 5M. Results  Scores for all subjects were OSDI， 15.8±3.4； SⅠT， 6.0±7.7 mm； tear meniscus height， 0.27±0.13 mm； BUT， 7.9±5.5 s； the meibomian secretion score， 3.3±1.4； and meiboscore 3.4±1.6. Both BUT and tear meniscus height were positively correlated with SⅠT （r=0.474， 0.432， P<0.01）. Both the meibomian secretion score and meiboscore had a positive correlation with OSDI （r=0.673， 0.752， P<0.05） and a negative correlation with BUT （r=-0.638， -0.603， P<0.05）. The Keratograph 5M showed fine test-retest reliability （ICC=0.84-0.89）. Conclusion  The Keratograph 5M can directly evaluate the ocular surface condition of dry eye patients. The Keratograph 5M is a non-contact， noninvasive and reliable examination with practical clinical application.

Objective  To evaluate the effect of early damage to the retina caused by impaired glucose tolerance （IGT） by studying the changes in visual function and the retinal nerve fiber layer （RNFL）. Methods  This was a cross-sectional study. Patients who visited Cangzhou Center Hospital from June 2012 to 2013 were randomly selected to be assigned to 3 groups： the diabetes mellitus （DM） group （76 patients with type 2 diabetes mellitus for 10 to 20 years without diabetic retinopathy）， the IGT group （79 patients with IGT for 3 or more years who have not yet progressed to DM） and a normal control group （80 healthy people）. All groups underwent optical coherence tomography （OCT）， contrast sensitivity （CS）， visual acuity tests， and ophthalmoscope examination. In the DM group， patients were further checked by FFA. Differences in these results， including RNFL thickness of the optic disk and CS measurements， were statistically compared between the different groups （one-way ANOVA）. In addition， the correlation of RNFL thickness and CS measurements were analyzed. Results  The RNFL thicknesses of patients in the DM group were much lower than in the normal controls in an average 360° circumference （98.3±10.3， P<0.01）， in the quadrant above the optic disk （114.8±14.7， P<0.01）， beneath the optic disk （128.5±15.4， P<0.01） and in the nasal quadrant （71.4±8.6， P<0.05）. No significant difference was found between the IGT group and normal control group. At the same time， there was a significant difference in CS measurements between the DM group and normal controls， including patients in their 40s at 6 c/d， 12 c/d and 18 c/d （P<0.01）， in their 50s at 3 c/d， 6 c/d， 12 c/d and 18 c/d （P<0.05）， and in their 60s and 70s at 3 c/d， 6 c/d， 12 c/d， and 18 c/d （P<0.05）. Obvious differences were found in the IGT group for patients in their 40s at 12 c/d and 18 c/d （P<0.05）， in their 50s at 6 c/d， 12 c/d and 18 c/d （P<0.05） and in their 60s and 70s at 6 c/d and 12 c/d （P<0.05）. There was also a positive correlation between CS measurements at the inte

Objective  To evaluate the damage to retinal function in patients receiving hydroxychloroquine （HCQ） by observing the changes in the retinal nerve fiber layer （RNFL）. Methods  A retrospective study was performed on 30 patients with rheumatoid arthritis who were treated with HCQ therapy and 30 healthy people. Visual acuity， visual field and fundus examinations as well as optical coherence tomography （OCT） were compared between the two groups. Results  Visual acuity， visual field and fundus examinations were normal. Decreases were noted with OCT. Conclusion  OCT can detect early retinal toxicity due to hydroxychloroquine.

Ultraviolet A and blue lights in riboflavin cross-linking are effective approaches to increase the mechanical and biochemical rigidity of collagen fibers. The effect of cross-linking and the safety of the eye are affected by riboflavin， which acts as a photosensitizer and protective agent. The riboflavin content in the cornea and sclera relates to many factors and needs to be detected by reasonable methods. This article focuses on the two methods mentioned above.