Since the end of 2019, the novel coronavirus pneumonia(COVID-19)has rapidly spread in Wuhan City, Hubei Province of China. This has aroused great concern of the Chinese government and the international community. There have been unconfirmed threads of COVID-19 patients with conjunctivitis as the first symptom. Therefore, the issue that whether and how the novel coronavirus strain SARS-CoV-2 infection is transmitted through the ocular surface has become a new concern. In the absence of clinical and experimental evidence of COVID-19 in ocular infection, we have conducted a retrospective literature analysis of viral pathogens that simultaneously trigger ocular lesions during the onset of epidemic diseases. The purpose of this paper is to provide some reference and suggestions for appropriately understanding of ocular protection in the prevention and control of the COVID-19.

Age-related cataract is a blinding eye disease that affects vision due to opacity of intraocular lens, ranking first in the world. Under oxidative stress, the activation of apoptosis related signal transduction pathways in lens epithelial cells is the main mechanism mediating age-related cataract. There are many related signaling pathways for apoptosis, and it is a complex network system. The purpose of this literature review is to summarize different apoptotic cell signal transduction pathways that mediate age-related cataract, laying the foundation for further researching.

AIM: To evaluate the changes in corneal epithelial thickness in corneal grafts following penetrating keratoplasty(PK)using anterior segment optical coherence tomography(AS-OCT), and to determine the role of epithelial thickness mapping in the early detection of graft rejection.

METHODS: This prospective comparative observational study included 20 patients(20 eyes)who underwent PK as study group and 16 patients(16 eyes)as control group. Corneal epithelial thickness mapping using AS-OCT was performed at 2wk, 1 and 3mo postoperatively. The parameters of epithelial thickness and distribution at the 3mo were compared to 16 patients(16 eyes)with allograft rejection following PK.

RESULTS: There was significant decline in the superior, inferior, maximum, and minimum epithelial thickness values of the study group at 1mo compared to 2wk(P=0.0004, 0.0001, 0.0001, 0.04 respectively)with no significant differences at 3mo compared to 1mo(P=0.4, 0.1, 0.8)respectively. Percentage of reduction in epithelial thickness was significantly higher than that of stromal thickness at 1mo compared to 2wk(P=0.04). The epithelial thickness maps showed a similar pattern of epithelial thickness distribution in the study group and in the rejection group showing considerable corneal edema. However, the allograft rejection group showed irregular pattern of epithelial thickness distribution in patients showing relatively higher central corneal thickness(CCT)as measured by pachymetry map.

CONCLUSION: Quantitative assessment of graft epithelial remodeling following PK shows early changes that contribute to significant corneal graft thickness changes. Changes in corneal epithelial thickness and pattern of distribution could be used as an indicator for corneal graft rejection.

AIM: To find out the prevalence of inherited color vision deficiency(CVD)among Palestinian male-school children aged 14-18 and compare it with other eastern and western countries.

METHODS: Six hundred and thirty-four male subjects(n=634)aged 14-18 from Palestinian Governorate of Nablus were randomly selected and screened using Ishihara pseudoisochromatic plates. Subjects who failed Ishihara screening were tested further with computer software of Farnsworth-Munsell 100 Hue test.

RESULTS: Out of the 634 male participants, 597 were included in the study and 8.0% of them(48 males)demonstrated red-green CVD. 5.4%, 2.3% and 0.3% of the 48 males exhibited deutan, protan and total color vision deficiency(monochromacy), respectively.

CONCLUSION: The results show that the prevalence of red-green CVD among the male school children from Palestinian Governorate of Nablus is not significantly different from that of male populations in nearby and Western countries.

AIM: To examine the morphological and biochemical alterations in the eyes of Thioltransferase knockout(TTase KO)mouse model as a function of age, and to explore the important function in redox homeostasis in the lens and in the age-related cataractogenesis.

METHODS: TTase KO model was established in this laboratory. TTase KO and WT mice were examined and the lens opacity was classified by using a slit lamp. Each lens was homogenized in lysis buffer and processed for measurement of glutathione(GSH)level. Examination of Protein-GSH mixed disulfides(PSSG)formation in the lens by Western blot analysis. Immunoprecipitation was used to identify the proteins formed PSSG. Dethiolation of lens proteins was carried out using purified recombinant human lens TTase(RHLT).

RESULTS: The slit lamp examination showed an age-dependent nuclear cataract development in both eyes of the WT and TTase KO mice. The onset of cataract was 4mo in the KO mice and 9mo in the WT mice. The GSH loss showed in both groups during aging and was prominent in the TTase KO mice after 9mo old. PSSG in the lenses of both groups showed progressive elevation, whereas the lenses of the KO group had a higher level of PSSG after 9mo. These GSH-conjugated proteins were confirmed as actin and glyceraldehyes 3-phosphate dehydrogenase(GAPDH)by immunoprecipitation and they could be eliminated when the homogenates were treated with RHLT.

CONCLUSION: The results showed that deletion of TTase gene in the mouse could lead to an early age-dependent cataract formation and the PSSG formation in these lenses appeared to link directly to lens opacity. The PSSG could be dethiolated by TTase. This data strengthens that TTase plays an essential role in maintaining lens clarity.

AIM: To observe the effects of butterflybush flower eye drops at different concentrations on expression of inflammatory crtokines IL-1β, Mucin 5AC(MUC5AC)and P38MAPK in castrated male rabbits, and to explore the therapeutic effect of that drops on dry eyes.

METHODS: Thirty-six male rabbits were randomly divided into blank group(A), model group(B), low concentrations butterflybush flower eye drops group(C, 1mg/mL), the medium concentrations drops group(D, 1.5mg/mL), the high concentrations drops group(E, 3mg/mL), and testosterone group(F). In addition to group A, the testes and epididymis were removed from each group to establish a dry eye animal model. After successful modeling, groups A and B remain unchanged. Groups C, D, and E were given different concentrations of butterflybush flower eye drops, 3 times/d. In group F, testosterone propionate was injected into the muscles of the thigh at a dose of 0.5mL/kg once every 3d. Fluorescein staining, Schirmer I test(SⅠt)and tear film break time(BUT)were measured under general anesthesia in each group, eatment. After 4wk of treatment, the rabbits were sacrificed and the conjunctival tissues of the eyes were taken. The expression of IL-1β, mucin 5AC and P38MAPK in the conjunctiva was detected by immunohistochemical staining.

RESULTS: Among low concentrations butterflybush flower eye drops group, the medium concentrations drops group and the high concentrations drops group, the SⅠt value was significantly higher than that of model group, and BUT was significantly longer than model group. The positive staining of corneal fluorescein was significantly improved compared with model group, which was statistically significant(P<0.01). Among IL-1β and P38MAPK in the conjunctiva of high concentrations butterflybush flower eye drops group, the medium concentrations drops group and the low concentrations drops group, the positive expressions were lower than those in model group, and the expression of MUC5AC was higher than that in group model group(P<0.01). In addition, the high concentrations drops group was superior to the low and the medium concentrations drops group.

CONCLUSION: Butterflybush flower eye drops have androgen-like effect. For castrated dry eyes of male rabbits, they can down-regulate the expression of IL-1beta and P38MAPK in dry conjunctival tissue and increase the expression of MUC5AC, thus reducing inflammation infiltration in dry conjunctival tissue and maintaining tear film stability, but their effect is weaker than that of androgen. To the treatment of dry eyes, the middle and high concentration groups of the drops had stronger effects than the low one, and the high concentration group was better than the medium one.

AIM: To investigate the therapeutic efficiency of Mulberry eye drops on dry eye in perimenopausal female rabbit model.

METHODS: Totally 36 female New Zealand white rabbits were selected and operated with bilateral ovariectomy and fed for 60d postoperatively to make perimenopausal female rabbit dry eye model(36 eyes, all right eyes). And 24 of them were randomly divided into control group and experimental group(12 for each): the control group used PBS, the experimental group used Mulberry eye drops, the other 12 did not use any eye drops. The Schirmer I tests(SⅠt)and corneal fluorescein(FL)were made, and the tear total protein content, amylase activity, lactoferrin and lysozyme contents and confocal scanning microscopy were performed in two groups before treatment and 2, 4, 6wk after treatment.

RESULTS: There was no significant difference in SⅠt,FL scores,total proteins,lysozyme,lactoferrin contents and amylase activity between two groups at pre-therapy(all P>0.05).After 2, 4 and 6wk of treatment, there were significant changes in SⅠt and FL scores in the two groups(P<0.05). There were no significant changes in lysozyme content, lactoferrin, amylase activity and total tear protein in the experimental group compared with those before treatment(all P>0.05), while there were significant changes in lysozyme content, lactoferrin, amylase activity and total tear protein in the control group(all P<0.05). At 2, 4 and 6wk after treatment, there were differences in the scores of SⅠt and FL, lysozyme content, lactoferrin, amylase activity and total protein content in tear between the two groups(P<0.05). At 6 wk after treatment, the mean number of corneal basal cells and inflammatory cells in control group were 4436±289mm2 and 321±91mm2,respectively,which in experimental group were 3219±223mm2 and 36±11mm2, respectively,there were statistical differences between two groups( all P<0.05). After 6wk treatment, there were no change of corneal nerve bending and less density in control group while the nerve fiber bending and density decreased significantly in experimental group,there were statistical differences between two groups(all P<0.05).

CONCLUSION: Mulberry eye drops has significantly therapy effects on the dry eye induced by decreased androgen and it has a definite clinical application value.

AIM: To investigate the protective effect of the antioxidant N-acetylcysteine(NAC)on retina in early diabetic rats.

METHODS: Thirty healthy adult male SD rats were randomly assigned to the normal control group(CON group, n=10)and the diabetes group(DM group, n=20). After fasting for 12h, the DM group was injected with 1% streptozotocin(STZ)solution, according to 60mg/kg disposable left lower abdominal injection. After 72h, blood was taken from the rat tail vein to detect blood glucose, diabetic model animals were defined as ≥16.7mmol/L. Model rats were randomly divided into diabetes control group(group D)and NAC treatment group(group N). After the model was established, N group of rats were injected with 4μL 1.6μg/μL NAC through the vitreous cavity every week. Rats in CON group and D group were injected with 4μL 0.01mmol/L phosphate buffer saline. All the rats no diet water, group feeding. Body mass and blood glucose were recorded weekly. After the diabetes was modeled, 2mo killed the experimental animals. The thickness of the inner layer of the retina of rats in each group was determined by HE staining. The number of retinal ganglion cells and the level of pigment epithelial derived factor in the retina were measured by immunofluorescence.

RESULTS: The thickness of retinal kernel layer increased in group N compared with group D(P<0.01), and there was no difference between group CON and group(P>0.05). Compared with CON group, the number of retinal ganglion cells decreased in group D(P<0.01), and decreased slightly in group N(P>0.05). Retinal ganglion cells decreased in group D compared with group N(P<0.01). Compared with CON group, PEDF expression decreased in group D(P<0.01), and decreased slightly in group N(P>0.05). The expression of PEDF in group D decreased compared with group N(P<0.01).

CONCLUSION: The protective effect of antioxidant NAC on retinal tissue in early diabetic rats may be due to the up-regulation of PEDF levels in the retina.

AIM: To explore the relationship between HbA1c and the changes of retinal and choroidal structures in macular region, and between HbA1c and corrected distant visual acuity before and after cataract surgery in diabetic patients.

METHODS: It is a prospective randomized clinical trial. According to the patient's history, the subjects were divided into the non-diabetes group and the diabetic group. According to the level of HbA1c before operation, the diabetic group was divided into the high HbA1c group(HbA1c>7.0%)and the normal HbA1c group(HbA1c≤7.0%). All 87 eyes from 82 patients who met the criteria from October 2016 to December 2017 in the Department of Ophthalmology at Qingdao Municipal Hospital were enrolled in this study. There were 30 eyes from 28 patients in the non-diabetes group(4%≤HbA1c≤6.0%), 29 eyes from 28 patients in the high HbA1c group and 28 eyes from 26 patients in the normal HbA1c group. Spectral-domain optical coherence tomography(SD-OCT)was used to examine central subifield thickness(CST), central volume(CV)and subfoveal choroidal thickness(SFCT)at 1d before surgery, 1d after surgery, 1wk after surgery, 1mo after surgery and 3mo after surgery. The variance analysis and Pearson correlation analysis were used to analyze the changes and the correlation with HbA1c value. At the same time, the incidence of macular edema after surgery(PCME)was compared among the groups, and the relationship between HbA1c and postoperative corrected distance visual acuity(CDVA)in diabetes patients was also analyzed.

RESULTS: In non diabetic group, high HbA1c group and normal HbA1c group, CST was 239.03+11.55μm, 254.38+26.44μm, 247.07+19.51μm at 1wk after cataract surgery. Their CST was 241.00±11.15μm, 271.55±61.05μm, 248.64±38.28μm at 1mo after cataract surgery(F=3.001, P=0.048). Besides, there was a positive correlation between HbA1c and CST at 1wk and 1mo after operation in the two groups at P=0.01 level(r1wk=0.338, r1mo=0.297)(P<0.05). The postoperative macular cystoid edema in non-diabetic group, high HbA1c group and normal HbA1c group were 0, 5(5 eyes, 17%)and 1(1 eye, 4%)respectively. In non diabetic group, high HbA1c group and normal HbA1c group, CDVA was 0.07±0.06, 0.12±0.10, 0.09±0.08 at 1wk after cataract surgery. Their CDVA was 0.03±0.06, 0.11±0.15, 0.11±0.09 at 1mo after cataract surgery. Their CDVA was 0.02±0.04, 0.08±0.12, 0.06±0.06 at 3mo after cataract surgery(F=3.272, P=0.045). The differences among three groups in the CDVA were statistically significant at 1wk, 1mo and 3mo after surgery. There was no significant difference between the high HbA1c group and the normal HbA1c group(P>0.05). However, CDVA(LogMAR)of the two groups was positively correlated with HbA1c at P=0.01 level(r1wk=0.425, r1mo=0.235, r3mo=0.332). There was no statistically significant difference in the changes of CV and SFCT among the three groups, and the trend of changes among these groups was approximately the same.

CONCLUSION: There is a close relationship between the microscopic structure of macula and HbA1c before phacoemulsification in diabetic patients. The risk of macular edema increased in patients with hba1c >7.0% before surgery. The best corrected visual acuity of diabetes patients after surgery was significantly related to the hba1c value before surgery. The higher the hba1c value before surgery, the poorer the improvement of vision after surgery. The level of HbA1c before surgery in diabetic patients is related to the anatomical structure of macular after cataract surgery. The risk of macular edema after surgery is increased in patients with high HbA1c(HbA1c>7.0%)before surgery. Meanwhile, the preoperative HbA1c of diabetic patients is closely related to CDVA after cataract surgery. The higher the preoperative HbA1c value, the worse the CDVA in diabetics after surgery.

AIM: To analyze the correlation between tear film lipid layer thickness(LLT)and macular microvascular parameters in diabetic retinopathy.

METHODS: Totally 60 eyes of type 2 diabetes patients with non-proliferative stage(NPDR group)and 60 eyes of proliferative stage(PDR group)with diabetic retinopathy diagnosed in our hospital from 2018-01/12 were selected, and 60 eyes of healthy volunteers with appropriate age and gender were selected as the normal control group. The tear film lipid layer thickness(LLT)was examined by Lipiview eye surface interferometer, while the foveal avascular zone(FAZ), superficial capillary layer(SCL)vessel density and deep capillary layer(DCL)vessel density were measured by optical coherence tomography angiography(OCTA)in three groups. The differences and correlations between the parameters were compared.

RESULTS: LLT(69.87±11.401nm)in normal control group was higher than that in NPDR(54.87±7.453nm)and PDR group(42.67±5.246nm), and FAZ(0.312±0.021mm2)was lower than that in NDPR group(0.389±0.037mm2)and PDR group(0.437±0.032mm2). The vascular density of SCL(51.977%±4.164%)was significantly higher than that of NPDR(47.067%±4.757%)and PDR(41.865%±5.512%), and that of DCL(49.578%±2.619%)was higher than that of NPDR(46.032%±2.622%)and PDR(40.598%±2.671%)(all P<0.01). There was no correlation between LLT, FAZ, SCL and DCL in normal subjects. LLT was negatively correlated with FAZ in both NPDR group and PDR group(r=-0.922, r=-0.923, all P<0.01), positively correlated with SCL(r=0.798, r=0.902, all P<0.01), and had no correlation with DCL(r=0.140, r=0.073, P=0.285, P=0.581).

CONCLUSION: In diabetic retinopathy, the lipid layer of tear film is lower and the stability of tear film is decreased, and there is a correlation between diabetic dry eye and macular microvascular changes.