Keratoconus is a complicated refractive disease， and is more common in adolescents and young adults around the age of 15-25 years. The prevalence of domestic and international surveys shows an average of about 1/2 000. This age range is a critical period of ones life， when rapid growth and development occur， laying down a foundation and broadening horizons. Therefore， recognizing the harmful impact of this kind of disease for young people′s visual development and the benefits of non-surgical treatment for optical correction and treatment are particularly important. This article combines research progress both locally and internationally， from the improvement of visual quality and function， the stability of the treatment， the influence on physical and mental development and the impact on studying and living. This article also analyzes the advantages of using non-surgical optical correction treatments by a specially designed contact lens and existing problems involving convenience， operability and safety aspects.

Keratoconus is a common degenerative disorder of the cornea. This article describes new methods for the diagnosis and treatment of keratoconus. Since corneal refractive surgery is widely used， the early diagnosis and rational treatment of keratoconus have become more important. Traditional diagnosis always depends on clinical manifestations and changes in corneal topography but it cannot stop the progression of the disorder. Currently， in addition to corneal topography， a three-dimensional anterior segment analyzer， confocal microscope， ocular response analyzer， OCT and other instruments are being used to screen keratoconus or suspected keratoconus. Active， preventive treatments like corneal collagen cross-linking can stop progression.

Objective To investigate the role of the corneal epithelial thickness （EP） parameters measured with ultra-high resolution optical coherence tomography （UHR-OCT） in the diagnosis of keratoconus. Methods In this cross-sectional observational study， 20 patients with keratoconus （20 eyes） and 20 normal volunteers （20 eyes） were recruited in the study. Corneal epithelial thickness profiles were taken from all subjects. The parameters included mean thickness （MEAN）， minimum thickness （MIN）， epithelial ectasia index （EEI）， defined as epithelial thickness minimum thickness of the inferior half of the cornea divided by corneal epithelial thickness average thickness of the superior half of the cornea multiplied by 100， maximal epithelial ectasia index （EEI-MAX）， defined as corneal epithelial thickness minimum thickness of the inferior half of the cornea divided by corneal epithelial thickness maximum thickness of the superior half of the cornea multiplied by 100， epthetlium standard variation （ESV）. Statistical analysis methods included independent samples t-test and receiver operating characteristic （ROC） curves. Results In normal eyes， the MEAN， MIN， EEI， EEI-MAX， ESV were 52.52±2.64 ?滋ｍ， 50.05±3.38 ?滋ｍ， 97.93±4.59， 91.60±4.54， 2.94±0.56. In keratoconic eyes， they were 51.33±3.78 ?滋ｍ， 38.86±5.45 ?滋ｍ， 77.13±10.59， 67.45±12.64， 7.02±2.55. Among the epithelial pachymetry parameters， ESV showed highest diagnostic efficiency and diagnostic value for keratoconus， the area under the ROC curve （AUC） was 1.000 and the positive predictive value was 1.000. MIN， EEI， EEI-MAX also have high diagnostic efficiency and diagnostic value， the AUC were 0.955， 0.945， 0.950， and the positive predictive value were 0.900， 0.900， 0.950. Conclusion keratoconus is characterized by central and inferior epithelial thinning surrounded by thickened epithelium. The epithelial pachymetry parameters show excellent accuracy， sensitivity， and specificity in the diagnosis of keratoconus， especially the ESV.

Objective To observe the changes in corneal shape， corneal thickness and corneal biomechanics in keratoconus patients who wore RGPCL for more than 1 year. Methods In this retrospective case series study， 15 patients （30 eyes） with moderate or worse keratoconus were recruited. Average spherical and astigmatic powers were -9.53±3.60 D and -3.42±2.13 D， respectively. The RGPCL were fitted for diagnosed keratoconus eyes， and a paired t-test was used to compare corneal parameters between before and after 1 year of lens wear. Measured parameters included spherical and astigmatism power， corneal flat and steep K values， corneal thickness， corneal hysteresis （CH） and the corneal resistance factor （CRF）. Results Some changes occurred to keratoconus eyes after 1 year of wear： corneal steep K values decreased from 49.21±4.06 D to 47.95±3.16 D （t=3.156， P<0.05）； the corneal surface regularity index （SRI） and surface asymmetry index （SAI） decreased from 0.47±0.15 and 0.49±0.16 to 0.36±0.14 and 0.38±0.19 （t=2.314， 2.253， P<0.05）； corneal astigmatism decreased from -3.42±2.13 D to -2.63±1.57 D （t=-5.270， P<0.01）； corneal thickness had no significant change； corneal biomechanical CH increased from 8.26±0.39 mmHg to 10.23±0.49 mmHg （t=-5.954， P<0.01）； and corneal biomechanical CRF increased from 7.53±0.56 mmHg to 9.05±0.58 mmHg （t=-5.340， P<0.01）. Conclusion By following the change in corneal shape after 1 year of RGPCL wear， corneal biomechanical properties have significant increases in eyes with moderate or worse keratoconus. The patient′s condition and corneal biomechanics can be the key indicators for the efficacy of treating keratoconus patients with RGPCLs.

Objective To evaluate the clinical results and safety of big bubble deep anterior lamellar keratoplasty assisted by a femtosecond laser for keratoconus. Methods A case series of 11 eyes of 9 keratoconus patients were enrolled in the study. A 500 kHz VisuMax femtosecond laser （Carl Zeiss Meditec AG， Jena， Germany） was used to create a vertical side cut on both donor and recipient corneas. The mean thinnest corneal thickness measured with ultrasound corneal pachymetry， was 359.7±49.8 μm. Preoperative UCVA was counting fingers （CF） to -0.1 and preoperative BCVA was CF to -0.12. The mean donor diameter was 7.51±0.14 mm and mean recipient diameter was 7.38±0.10 mm. Mean follow-up was 7.70±2.88 months. Results All eyes were successfully treated without intraoperative complications. Early postoperative evaluation showed a clear graft in all cases. Mean corneal thickness was 481.4±51.3 μm. A normal corneal topographic pattern was restored. At the last postoperative examination， UCVA was 0.15 to 0.40 and the BCVA was 0.30 to 0.80. Conclusion Our early results indicate that femtosecond laser-assisted deep anterior lamellar keratoplasty using the big bubble technique shows promise as a safe and effective surgical choice in the treatment of keratoconus.

Objective To analyze the difference in corneal topography between primary keratoconus and secondary keratoconus after LASIK； to provide a reference for the clinical diagnosis and analysis of risk factors in secondary keratoconus． Methods In this retrospective case analysis， 13 secondary keratoconus patients （20 eyes， secondary group） were diagnosed and accepted for treatment in Shandong Eye Institute between January 1997 and December 2012． Correspondingly， 18 primary keratoconus patients （25 eyes， primary group） were randomly selected during the same period． The mean ages of the primary group and secondary group were 18.9±2.8 years （15-28 years） and 24.3±9.1 years （19-48 years）， respectively. The mean axial lengths were 25.39±1.33 mm（23.3-27.8 mm） and 27.09±2.43 mm（25.3-30.1 mm）， and the differences were statistically significant （t=3.942， P<0.01）． The morphological features of the topography were observed with an Orbscan Ⅱ system， which primarily included the position of the thinnest point of the cornea， the maximum simulation curvature of the anterior corneal surface （Kmax）， astigmatism， the average power and astigmatism in the central 3 mm region of the cornea， the Diff-values of the anterior and posterior corneal surfaces， and the morphology of the elevation map pattern． The collected data were analyzed with a t-test， one-way ANOVA and Pearson correlation coefficient． Results The distribution of the thinnest points in the corneal quadrants for the primary group were 18 eyes （72%） infratemporal， 4 eyes （16%） supertemporal， 1 eyes （4%） intranasal， 2 eyes （8%） supernasal， and the distributions for the secondary group were 8 eyes （40%），4 eyes （20%）， 4 eyes （20%） and 4 eyes （20%）， respectively． Corneal astigmatisms in the primary and secondary groups were 5.85±3.26 D and 3.95±2.51 D， and the astigmatism values in the 3 mm region were 4.12±2.11 D and 2.82±1.50 D. The differences were statistically significant （t=-2.142， -2.187， P<0.05）． There was no significant difference in posterior surface morphology between the 2 groups of patients （P>0.05）． Conclusion Compared to primary keratoconus， the morphological features of the corneal topography follow the same rules， and the astigmatism value is smaller． In addition， the thinnest point of the cornea is uniformly distributed near the central corneal area， which points out that excessive cutting may be a risk factor for secondary keratoconus.

Objective To evaluate the clinical outcome of epipolis LASIK （Epi-LASIK） combined with UVA/riboflavin crosslinking in patients with mild to moderate keratoconus. Methods A total of 31 eyes in 18 patients with mild to moderate keratoconus were recruited for this prospective study. Epi-LASIK was performed using the Ziemers Microkeratome and Wavelight EX500 excimer laser. UVA/riboflavin crosslinking was applied immediately after Epi-LASIK. UCVA and BCVA and corneal topography were assessed before treatment and at 1， 3， and 6 months after treatment. Results The average K value in the center of the cornea was 46.65±2.91 D before treatment， and was 42.94±3.88 D， 41.72±4.38 D and 41.99±3.84 D at 1， 3， and 6 months after treatment. Visual acuity was 0.70±0.24 before treatment， and 0.09±0.16， 0.06±0.20 and -0.06±0.03 at 1， 3， and 6 months after treatment. There was significant improvement in UCVA （F=3.39， P<0.01） and in the reduction of the K value （F=3.57， P<0.05） when measurements before treatment were compared to measurements after treatment at months 1， 3， and 6. Conclusion Epi-LASIK combined with UVA/riboflavin crosslinking is effective in improving visual acuity in mild to moderate keratoconus patients.

Objective To evaluate the distribution characteristics of the asphericity （Q-value） of the corneal surfaces in a Chinese population who were candidates for excimer laser surgery； to provide some theoretical bases for clinical diagnosis and treatment. Methods This was a perspective study. Using the Pentacam HR measuring and analyzing system based on Scheimpflug photography， the right eyes of 75 Chinese myopes were evaluated for excimer laser surgery. Patients were divided into a low corneal astigmatism （<+1.00 D） group and a medium-high corneal astigmatism （≥+1.00 D） group according to the anterior corneal surface astigmatism. The analysis was based on the distribution characteristics of the mean Q-values of both the anterior and posterior corneal surfaces and the distribution characteristics of the Q-value at different angles （20°， 25° and 30°） and along different semi-meridians （superior， inferior， nasal and temporal）. Single factor analysis of variance was used to determine if there was a difference among Q-values within a particular group. The differences between the two groups were analyzed by an independent samples t-test. Results The mean Q-values of the 30° angle in Chinese myopes evaluated for excimer laser surgery were -0.17±0.09 and -0.02±0.16 on the anterior and posterior corneal surfaces， respectively. The mean Q-values of the anterior corneal surface at different angles were negative and there was no statistically significant difference between the low corneal astigmatism group and medium-high corneal astigmatism group. There was a significant difference between the Q-values of the 2 groups at different angles （F=6.340， 9.963， P＜0.01）， and in both groups Q20 was significantly larger than Q30 and Q25 （P＜0.05） but there was no statistically significant difference between Q30 and Q25. The mean Q-values of the posterior corneal surface were positive at the 20° and 25° angles and approached zero at the 30° angle. Comparisons between the 3 angles showed statistically significant differences （F=54.614， P＜0.01）. The comparisons showed that Q30<Q25<Q20. All mean Q-values along different semi-meridians of the anterior corneal surface were negative and there was no statistically significant difference between the 2 groups. There was a significant difference between Q-values along different semi-meridians in the 2 groups （F=19.262， 31.935， P＜0.01）. In the low corneal astigmatism group， QN30 was significantly smaller than QT30， QS30 and QI30 （P＜0.05） but there was no statistically significant difference between QT30， QS30 and QI30 （P＞0.05）. In the medium-high corneal astigmatism group， QT30 was significantly bigger than QN30 （P＜0.05） but there was no statistically significant difference between QS30 and QI30. In addition， QN30 and QT30 were significantly smaller than QS30 and QI30 （P＜0.05）. The Q-values of the posterior surface were positive along the inferior semi-meridian， negative along the nasal and temporal semi-meridians， and approached zero along the superior semi-meridian. There was also a significant difference between Q-values along different semi-meridians on the posterior surface（F=31.750， P＜0.01）. There were statistically significant differences between QT30 and QN30 （P＜0.05） and QI30 and QS30 （P＜0.05）. Comparisons showed that QT30>QN30 and QI30>QS30， but there was no statistically significant difference between QT30 and QS30. Conclusion The curvature along the anterior corneal surface becomes flatter from the center to the periphery， while it becomes steeper from the center to the periphery at the posterior corneal surface. The rate of the flattening of the anterior corneal surface increased as the range of the angle increased， while the rate decreased as the posterior corneal surface decreased. All the shapes on the anterior surface along different semi-meridians were long ovals. Corneal astigmatism does not affect corneal shape. The shapes of the posterior surface along the superior and inferior semi-meridians were short ovals， but were long ovals along the nasal and temporal semi-meridians.

Objective To evaluate visual quality before and after screen-reading using double-pass retinal images， and to analyze the relationship between refractive error and the stability of tear film and the amplitude of accommodation. Methods This was a prospective self-controlled study based on 53 college students （106 consecutive eyes）. Tear film and accommodation were assessed before and 1 hour after screen-reading with double-pass retinal images. The differences in the measurement data were compared with paired t tests and independent samples t tests. A one-way ANOVA was used to compare the differences among three diefferent refractive error groups. Results Tear-film stability （t=-7.464， P＜0.01） and the amplitude of accommodation （t=4.881， P＜0.01） of the subjects showed a decrease after 1 hour of screen-reading， but there were no differences between genders （P>0.05）. Tear film was more unstable before screen-reading and was correlated with an increase in refractive error， but the difference was not statistically significant. However， there was a statistically significant difference in accommodation between refractive groups （F=3.349， P＜0.05）， and the higher the refractive error， the lower the amplitude of accommodation. After 1 hour of screening-reading， tear film became more unstable and accommodation decreased as refractive error increased， but the difference was not significant （P>0.05）. Conclusion Screen-reading causes a decrease in tear film stability and worsens accommodation， and the extent of these problems is related to the degree of myopia.

Objective To comprehensively analyze the clinical efficacy of wavefront guided epipolis LASIK （Epi-LASIK） combined with iris recognition. Methods In a prospective study of wavefront guided Epi-LASIK combined with iris recognition， 37 patients （73 eyes） with myopia underwent treatment. The patients were divided into a low-to-moderate myopia group （SE＜-6.00 D， 30 eyes） and a high myopia group （SE≥-6.00 D， 43 eyes）. All patients were required to undergo preoperative and postoperative examinations that included UCVA， BCVA， refractive status， intraocular pressure， anterior segment slit lamp examinations， corneal topographic tests， WaveScan aberrometer tests， contrast sensitivity （CS） tests， etc. Patients were evaluated at 1 day， 1 week， and 1 month， 3 months and 6 months postoperatively. A t test， ANOVA and chi-square test were used to compare results. Results ?譹?訛Postoperative UCVA： Low-to-moderate myopia patients improved and recovered UCVA faster and better than high myopia patients. At 6 months postoperatively， UCVA in low-to-moderate myopia patients was 5.05±0.11 and was 5.01±0.11 in high myopia patients. There was no significant difference between the groups （t=1.69， P＞0.05）. ?譺?訛Refraction accuracy： refraction in all patients stabilized within 6 months postoperatively. At 6 months postoperatively， refraction in low-to-moderate myopia patients was +0.16±0.43 D and was -0.21±0.64 D in high myopia patients. ?譻?訛The height of the corneal posterior surface： there was a noticeable drop in height after refractive surgery and the surface remained stable postoperatively in all patients. There was no significant difference between the 2 groups. ?譼?訛Higher order aberrations （HOA）： there was an increase in total HOA， coma and spherical aberration in all patients postoperatively. Only trefoil conversely decreased. High myopia patients developed more aberrations than low-to-moderate myopia patients. ?譽?訛CS： the vast majority of patients had a gradual increase in CS and glare sensitivity （GS） postoperatively， reaching a peak at 3 months. Preoperative comparisons showed that CS and GS did not significantly drop in any patients postoperatively. Low-to-moderate myopia patients had better CS and GS for each spatial frequency than high myopia patients. ?譾?訛No patient had serious postoperative complications. Conclusion Wavefront-guided Epi-LASIK combined with iris recognition is more accurate， predictable and stable and results in better visual quality. Clinical efficacy is better for low-to-moderate myopia patients than for high myopia patients.

Objective To evaluate differences between the prism bar and synoptophore methods in the measurement of fusional convergence and fusional divergence in normal children. Methods This was a prospective research study. Children aged 8 to 15 years who had no ocular disease were recruited and tested with their prescribed refractions. The break and recovery points of fusional convergence and fusional divergence were measured by the prism bar and synoptophore methods respectively. Each test was repeated 3 times. An independent samples t-test was used to compare the difference between the 2 methods. Correlation between the two methods was analyzed by a Spearman rank correlation. Results There were no differences in break and recovery points of fusional vergences between dominant eye and non-dominant eye. There were positive correlations between break point values measured by the synoptophore and prism bar （convergence r=0.60， P＜0.01； divergence r=0.46， P<0.05）. When measured by the prism bar and synoptophore respectively， no significant differences could be found for either the values of the break points or that of recovery points of the 2 methods. Conclusion When measuring the distance fusional vergences， prism bar and synoptophore with similar effect.

Objective To study the impact of distance myoporthosis spectacles on reading position among myopic children. Methods A cross-sectional survey of 148 cases was carried out. Children with refractive errors between -0.50 and -6.50 D and astigmatism less than -0.75 D were involved in the study. We recorded the reading posture of children by using a camera and measured head and eye movement patterns under near reading conditions for both uncorrected and corrected conditions. The effect of correction and no correction on the above patterns was also investigated. Data were analyzed using paired t test and Pearson correlation. Results ?譹?訛Uncorrected myopia influenced reading position， that is， head and eye positions. Refractive correcting spectacles can reduce both the scope of head movement （t=10.661， P<0.01） and eye movement （t=-4.079， P＜0.01）； ?譺?訛Since eyes and lenses are non-coaxial and away from the optical center， spectacles for distance do not adapt to the change in eye position while reading. Conclusion Spectacles for distance can help myopic children correct their reading position to a certain extent but cannot fully meet the requirements of reading.

Cataract is a common complication after corneal transplantation， with a higher risk in cataract surgery. Cataract surgery has a significant effect on the corneal endothelium after corneal transplantation. By evaluating the condition of the corneal endothelium and the safety of the cataract surgery after corneal transplantation， patients can receive more appropriate treatment and achieve the best vision outcomes. This is accomplished by using advanced cataract surgical equipment and proper surgical techniques combined with long-term postoperative follow-up.