Single-cell RNA sequencing analysis of the retina under acute high intraocular pressure

High intraocular pressure causes retinal ganglion cell injury in primary and secondary glaucoma diseases,yet the molecular landscape characteristics of retinal cells under high intraocular pressure remain unknown.Rat models of acute hypertension ocular pressure were established by injection of cross-linked hyaluronic acid hydrogel(Healaflow■).Single-cell RNA sequencing was then used to describe the cellular composition and molecular profile of the retina following high intraocular pressure.Our results identified a total of 12 cell types,namely retinal pigment epithelial cells,rod-photoreceptor cells,bipolar cells,Müller cells,microglia,cone-photoreceptor cells,retinal ganglion cells,endothelial cells,retinal progenitor cells,oligodendrocytes,pericytes,and fibroblasts.The single-cell RNA sequencing analysis of the retina under acute high intraocular pressure revealed obvious changes in the proportions of various retinal cells,with ganglion cells decreased by 23%.Hematoxylin and eosin staining and TUNEL staining confirmed the damage to retinal ganglion cells under high intraocular pressure.We extracted data from retinal ganglion cells and analyzed the retinal ganglion cell cluster with the most distinct expression.We found upregulation of the B3gat2 gene,which is associated with neuronal migration and adhesion,and downregulation of the Tsc22d gene,which participates in inhibition of inflammation.This study is the first to reveal molecular changes and intercellular interactions in the retina under high intraocular pressure.These data contribute to understanding of the molecular mechanism of retinal injury induced by high intraocular pressure and will benefit the development of novel therapies.

Casein kinase-2 inhibition promotes retinal ganglion cell survival after acute intraocular pressure elevation

Intraocular pressure elevation can induce retinal ganglion cell death and is a clinically reversible risk factor for glaucoma,the leading cause of irreversible blindness.We previously demonstrated that casein kinase-2 inhibition can promote retinal ganglion cell survival and axonal regeneration in rats after optic nerve injury.To investigate the underlying mechanism,in the current study we increased the intraocular pressure of adult rats to 75 mmHg for 2 hours and then administered a casein kinase-2 inhibitor(4,5,6,7-tetrabromo-2-azabenzimidazole or 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole)by intravitreal injection.We found that intravitreal injection of 4,5,6,7-tetrabromo-2-azabenzimidazole or 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole promoted retinal ganglion cell survival and reduced the number of infiltrating macrophages.Transcriptomic analysis showed that the mitogen activated protein kinase signaling pathway was involved in the response to intraocular pressure elevation but was not modulated by the casein kinase-2 inhibitors.Furthermore,casein kinase-2 inhibition downregulated the expression of genes(Cck,Htrsa,Nef1,Htrlb,Prph,Chat,Slc18a3,Slc5a7,Scn1b,Crybb2,Tsga10ip,and Vstm21)involved in intraocular pressure elevation.Our data indicate that inhibition of casein kinase-2 can enhance retinal ganglion cell survival in rats after acute intraocular pressure elevation via macrophage inactivation.

Corneal and intraocular pressure changes associated to the circadian rhythms:a narrative review

AIM:To synthesize the current body of research regarding the diurnal variations in intraocular pressure(IOP)and corneal biomechanical and morphological parameters,highlighting their significance in various eye conditions.METHODS:A comprehensive review of studies on the diurnal variations of IOP and corneal parameters was conducted.Tonometry findings from various studies were assessed,including the Goldmann applanation tonometry(GAT)and non-contact tonometers.Data on the variations in central corneal thickness(CCT),corneal curvature,and corneal biomechanics measured by the Ocular Response Analyzer system across different population groups was extracted and analyzed.RESULTS:In both healthy subjects and those with Fuchs dystrophy,IOP and CCT demonstrate marked diurnal declines.GAT remains the gold standard for tonometry,with the highest reliability.However,its measurements are influenced by CCT.Keratoconus patients and those with pseudoexfoliation showed significant diurnal variations in IOP.The biomechanical parameters,especially corneal hysteresis(CH)and the corneal resistance factor(CRF),largely remain stable throughout the day for most of eye conditions,with some exceptions.Notably,the corneal morphology diurnal variation,particularly curvature,yielded mixed conclusions across studies.CONCLUSION:Circadian rhythms significantly influence various corneal parameters,most notably IOP and CCT.Further studies should emphasize standardized approaches larger sample sizes,and delve deeper into less-explored areas,such as the effects of orthokeratology lenses on diurnal biomechanical shifts.

Intraocular pressure before and after capsulorhexis using two viscoelastic substances and two surgical approaches in enucleated porcine eyes

AIM:To investigate the influence of ophthalmic viscoelastic devices(OVDs)and different surgical approaches on the intraocular pressure(IOP)before and after creation of the curvilinear circular capsulorhexis(CCC)as a measure for anterior chamber stability during this maneuver.METHODS:Prospective experimental WetLab study carried out on enucleated porcine eyes.IOP was measured before and after CCC with the iCare Rebound tonometer(iCare ic200;iCare Finland Oy,Vantaa,Finland).The OVDs used were a cohesive one[Z-Hyalin,Carl Zeiss Meditec AG,Germany;hyaluronic acid(HA)]and a dispersive[Z-Celcoat,Carl Zeiss Meditec AG,Germany;hydroxy propylmethylcellulosis(HPMC)].The CCC was created using Utrata forceps or 23 g microforceps in different combinations with the OVDs.RESULTS:Using the Utrata forceps the IOP dropped from 63.65±6.44 to 11.25±3.63 mm Hg during the CCC.The use of different OVDs made no difference.Using the 23 g microforceps the IOP dropped from 65.35±8.15 to 36.55±6.09 mm Hg.The difference between IOP drop using either Utrata forceps or 23 g microforceps was highly significant regardless of the OVD used.CONCLUSION:Using the sideport for the creation of the capsulorhexis leads to a lesser drop in IOP during this maneuver compared to the main incision in enucleated porcine eyes.The use of different OVD has no significant influence on IOP drop.

Intraocular pressure and gonioscopic findings in primary angle-closure disease in India—a big data study

AIM:To describe the gonioscopic profile and intraocular pressure(IOP)in primary angle-closure(PAC)disease in patients presenting to a tertiary eye care network in India.METHODS:A cross-sectional hospital-based study that included 31484 new patients presenting between 2011 and 2021.Patients with a clinical diagnosis of PAC/suspect/glaucoma were included.The data was collected from an electronic medical record system.RESULTS:PAC glaucoma(PACG)(47.55%)was the most common diagnosis followed by PAC(39.49%)and PAC suspect(PACS;12.96%).Female preponderance(54.6%)was noted with higher mean age at presentation among males(P<0.0001).PACS and PAC showed the highest prevalence in 6th decade but PACG was higher at 7th decade.The probability of angle opening was 95.93%,90.32%and 63.36%in PACS,PAC and PACG eyes respectively post peripheral iridotomy(PI).Plateau iris syndrome(PIS)was noted in 252 eyes and all showed post dilated rise of IOP.A post dilated IOP rise was also noted with 8.86%,33.95%and 57.19%eyes with PACS,PAC and PACG respectively with IOP rise between 6-8 mm Hg across the disease spectrum.CONCLUSION:The superior quadrant is the narrowest angle and difficult to open with indentation and post PI.The probability of angle opening is less in PIS especially the complete variety along with post dilated IOP rise.The post dilated IOP rise in angle closure eyes warrants a careful dilatation,especially with PIS.

Background diseases and the number of previous intravitreal aflibercept injections on immediate intraocular pressure increase and vitreous reflux rate in phakic eyes

●AIM:To evaluate the effect of background diseases and number of previous intravitreal aflibercept injections(IVAIs)on immediate intraocular pressure(IOP)increase and vitreous reflux(VR)rate and to evaluate the correlation of both age and axial length with immediate IOP increase and VR rate.●METHODS:This study included 105 patients with cystoid macular edema secondary to retinal vein occlusion,35 patients with diabetic macular edema,69 patients with neovascular age-related macular degeneration(nAMD),and 12 patients with myopic choroidal neovascularization,which underwent first-time IVAI.The correlation of immediate IOP increase and VR rates with the four background diseases was investigated.Moreover,the correlation of age with immediate IOP increase and VR rate as well as correlation of axial length with immediate IOP increase and VR rate were evaluated.Further,54 patients with nAMD were treated with IVAI>10 times(multiple IVAIs).Moreover,the correlation of immediate IOP increase and VR rates with first-time and multiple IVAIs in nAMD was determined.●RESULTS:The immediate IOP increase(P=0.16)and VR rates(P=0.50)were almost similar among the four background diseases.The immediate postinjection IOP and age,VR rate and age,immediate postinjection IOP and axial length,or VR rate and axial length were not correlated in the four background diseases.The immediate IOP increase(P=0.66)and VR rates(P=0.28)did not significantly differ between first-time and multiple IVAIs in nAMD.●CONCLUSION:Background diseases and number of previous IVAIs have no effect on immediate IOP increase and VR rate.Further,age and axial length have no correlation on immediate IOP increase and VR rate.

Transpalpebral intraocular pressure measurement by Diaton compared to Goldman applanation tonometer in myopic eyes before and after transepithelial photorefractive keratectomy in Saudi Arabia

AIM:To compare intraocular pressure(IOP)measured via the trans palpebral IOP(tp IOP)method using a Diaton or with a Goldman applanation tonometer(GAT)and study the determinants of IOP difference in eyes undergoing transepithelial photorefractive keratectomy(TPRK)for myopia.METHODS:This cross-sectional validation study was held in 2020 in an eye hospital in Saudi Arabia.IOP was measured by Diaton and GAT before treatment,after one week,and one month of TPRK.It is considered if IOP difference by Diaton and GAT was less than±2 mm Hg acceptable.The IOP difference was tested if correlated to spherical equivalent(SE),central corneal thickness(CCT),age,gender,or tp IOP.RESULTS:Totolly 200 myopic eyes of 100 patients were included in the study.The mean difference of IOP measured by two methods before TPRK,1wk,and 1mo after TPRK were 0.790,-0.790,and-0.920 mm Hg,respectively(P<0.001).Diaton could measure IOP effectively 89.5%eyes before TPRK and 82%and 84%at 1wk and 1mo after TPTK,respectively.At week 1,IOP differences were significantly correlated to baseline CCT(P=0.02)and tp IOP at week 1(P<0.001).One month after TPRK,only tp IOP was significantly correlated to the difference in IOP(P<0.001).CONCLUSION:Diaton is a good screening tool for IOP before TPRK.It helps in monitoring IOP after surgery.Although more practical,it is less efficient than GAT.In eyes with high myopia and low tp IOP before surgery,IOP post-TPRK by Diaton and GAT could differ.

Distribution and associated factors of intraocular pressure in the older population:Tehran Geriatric Eye Study

AIM:To determine the distribution and associated factors of intraocular pressure(IOP) in an Iranian elderly population 60 years of age and above.METHODS:The present report is part of the Tehran Geriatric Eye study(TGES),a population-based cross-sectional study that was conducted on the residents of Tehran 60 years of age and above.The sampling was performed using multistage stratified random cluster sampling methods from 22 districts of Tehran,Iran.Demographic and history information,blood samples,and blood pressure were collected from all participants.Ocular examinations included measurement of uncorrected and best-corrected visual acuity,objective and subjective refraction,and slit-lamp biomicroscopy.The IOP was measured using Goldmann applanation tonometry(GAT).Corneal imaging and ocular biometry were performed using Pentacam AXL.RESULTS:The data of 3892 eyes of 2124 individuals were analyzed for this report.The mean age of the study participants was 66.49±5.31y(range:60 to 95y).The mean IOP was 15.2 mm Hg(95%CI:15.1 to 15.4),15.3 mm Hg(95%CI:15.1 to 15.5) and 15.1 mm Hg(95%CI:15.0 to 15.3) in all participants,males,and females,respectively.Of the study participants,1.3% had an IOP of ≥20 mm Hg.The mean IOP increased from 15.1 mm Hg in the age group 60-64y to 16.3 mm Hg in the age group ≥80y.According to the final multiple GEE model,the IOP was statistically significantly higher in men than in women.All the studied age groups,except for the 75-79-year-old age group,had significantly higher IOP compared to the 60-64-year-old age group.The IOP was significantly higher in underweight compared to other body mass index groups.Moreover,the IOP had a statistically significant direct relationship with the mean corneal power(mean CP),central corneal thickness(CCT),and systolic blood pressure.CONCLUSION:The present study presents the distribution of IOP in an Iranian elderly population.A higher IOP(within the range 14 to 17 mm Hg) is significantly associated with older age,male sex,high systolic blood pressure,increased mean CP,and CCT.These factors should be considered in the clinical interpretation of IOP.

Efficacy of ripasudil in reducing intraocular pressure and medication score for ocular hypertension with inflammation and corticosteroid

·AIM:To investigate the efficacy of ripasudil,a Rho kinase inhibitor,in reducing intraocular pressure(IOP)and medication scores of anti-glaucoma drugs in patients with ocular hypertension with inflammation and corticosteroid.·METHODS:The study included 11 patients diagnosed with ocular hypertension with inflammation and corticosteroid,all of whom were prescribed ripasudil eye drops and followed up for at least 2y after the initiation of treatment.IOP was measured using a non-contact tonometer before enrollment and at each follow-up visit.The medication score of glaucoma eye drops was calculated for each patient.·RESULTS:The mean IOP(26.4±2.9 mm Hg before treatment)significantly decreased after ripasudil therapy(13.7±3.3 mm Hg at 3mo)and remained stable in the low-teens during the 2-year follow-up period(P<0.0001).A significant decrease in the medication score was observed at 12mo or later after the initiation of ripasudil therapy(P<0.05).Both baseline medication scores and glaucomatous optic disc change rates were significantly higher in the five eyes that required glaucoma surgery during the 2-year observation period than the 10 eyes that did not require surgery.·CONCLUSION:Our results demonstrate the efficacy of ripasudil,in reducing IOP and the medication score over a 2-year treatment period in patients with ocular hypertension with inflammation and corticosteroid.Our findings also suggest that ripasudil could reduce the IOP in uveitic glaucoma patients with both lower baseline medication score and lower glaucomatous optic disc change rate.

Effects of propofol versus urapidil on perioperative hemodynamics and intraocular pressure during anesthesia and extubation in ophthalmic patients

AIM: To compare the effect of propofol versus urapidil on hemodynamics and intraocular pressure during anesthesia and extubation for ophthalmic patients. METHODS: Eighty-two surgical patients (Class: ASA I-II) were randomly assigned to propofol (n = 41) and urapidil groups (n = 41). Their gender, age, body mass, operation time and dosage of anesthetics had no significant difference between the two groups (P > 0.05). The patients of propofol and urapidil groups were given propofol (1.5mg/kg) and urapidil (2.5mg/kg) respectively; and two drugs were all diluted with normal saline to 8mL. Then the drugs were given to patients by slow intravenous injection. After treatment, the patients were conducted immediate suction, tracheal extubation, and then patients wore oxygen masks for 10 minutes. By double-blind methods, before the induction medication, at the suction, and 5, 10 minutes after the extubation, we recorded the systolic and diastolic blood pressure (BP), heart rate (HR), pH, PaO2, PaCO2, SaO(2) and intraocular pressure (TOP) respectively. The complete recovery time of the patients with restlessness (on the command they could open eyes and shaking hands) was also recorded during the extubation. The data were analyzed by using a professional SPSS 15.0 statistical software. RESULTS: The incidence of cough, restlessness and glossocoma was significantly lower in the propofol group than that in the urapidil group after extubation (P < 0.05). There were no episodes of hypotension, laryngospasm, or severe respiratory depression. There was no statistical difference in recovery time between two groups (P > 0.05). In propofol group, the BP and HR during extubation and thereafter had no significant difference compared with those before induction, while they were significantly lower than those before giving propofol (P < 0.05), and had significant difference compared with those in urapidil group (P < 0.05). Compared to preinduction, the BP of urapidil group showed no obvious increase during aspiration and extubation. The HR of urapidil group had little changes after being given urapidil, and it was obviously increased compared with that before induction. The stimulation of aspiration and extubation caused less cough and agitation in propofol group than that in urapidil group (P < 0.05). The IOP of propofol group showed no obvious increase during extubation compared with that in preinduction, while in the urpidil group, extubation caused IOP significantly increased (P < 0.05). The changes in these indicators between the two groups had no significant difference (P > 0.05). CONCLUSION: Compared to urapidil, propofol is superior for preventing the cardiovascular and stress responses and IOP increases during emergence and extubation for the ophthalmic patients. Moreover, it has no effects on patient's recovery.

Complications of intravitreal triamcinolone acetonide for macular edema and predictive factors for intraocular pressure elevation

AIM: To investigate the complications of intravitreal triamcinolone acetonide (IVTA) for the treatment of macular edema, and to determine the risk factors for intraocular pressure (IOP) elevation. METHODS: Charts of patients with macular edema secondary to branch retinal vein occlusion (BRVO), diabetic retinopathy and uveitis who had received IVTA injections were reviewed to document its complications. IOP elevation was defined as a pressure of ≥24mmHg at some point during follow-up. Multivariate logistic regression analysis was performed to characterize baseline risk factors for this elevation. RESULTS: The study included 111 eyes of 65 female and 46 male patients with a mean follow-up of (11.6±5.1) months. Of the 111 eyes, 52 (46.8%) had macular edema secondary to BRVO, 44 (39.6%) had clinically significant diabetic macular edema (CSDME) and 15 (13.5%) had non-infectious uveitis with macular edema. IOP was recorded ≥24mmHg in 38 eyes (34.2%) during the follow-up. Higher baseline IOP (P =0.022), younger age (P =0.003), and male gender (P = 0.014) were significant risk factors for IOP elevation after IVTA injection. Eyes with prior vitrectomy were less likely to have IOP elevation (P =0.054). Two eyes (5.2% of eyes with increased IOP) underwent trabeculectomy, and 9 eyes (16.3% of the phakic eyes) necessitated cataract surgery. Other complications included branch vein occlusion (1.8%), sterile endophthalmitis (0.9%) and pseudohypopyon (0.9%). CONCLUSION: IVTA has side effects with IOP elevation and cataract formation being the two most common. A subset of patients is more prone to developing increased IOP following IVTA, namely, younger male patients with higher baseline IOP.

Immediate intraocular pressure rise after intravitreal injection of ranibizumab and two doses of triamcinolone acetonide

AIM: To evaluate prospectively immediate intraocular pressure (IOP) changes after the intravitreal injection of ranibizumab, 2 and 4mg triamcinolone acetonide. METHODS: Patients who underwent intravitreal injection of 0.1mL (4mg) triamcinolone acetonide (TA, Group T4), 0.05mL (2mg) TA (Group T2) and 0.05mL (0.5mg) ranibizumab (Group R) comprised the study population. Overall, 229 eyes of 205 patients were injected. Fifty-four eyes (23.6%) were in Group T4, 69 eyes (30.1%) in Group T2 and 106 eyes (46.3%) in Group R. If IOP was less than 26mmHg immediately after the injection no further measurement was performed. If IOP was ≥26mmHg, IOP was remeasured till the reading was below 26mmHg at 5, 15 and 30 minutes. RESULTS: Immediately after the injection, the IOP of 28 eyes (51.9%) in Group T4, 22 eyes (31.9%) in Group T2 and 51 eyes (48.1%) in Group R were over 25mmHg. At 30 minutes, IOP of one eye (1.9%) in group T4, two eyes (2.9%) in group T2 and two eyes (1.9 %) in Group R were over 25mmHg. Immediate post-injection IOP was significantly higher in Group T4 and Group R when compared to Group T2 (P <0.001 and P <0.001, respectively). IOP was significantly higher in eyes without vitreous reflux when compared to those with vitreous reflux in all groups (P <0.001). CONCLUSION: IOP may remarkably increase immediately after the intravitreal injection of 2 or 4mg triamcinolone acetonide, and 0.5mg ranibizumab. Absence of vitreous reflux is the most important predicting factor for immediate IOP rise after the injection.

Impact of corneal parameters on intraocular pressure measurements in different tonometry methods

AIM: To evaluate the impact of central corneal thickness(CCT) and corneal curvature on intraocular pressure(IOP) measurements performed by three different tonometers. METHODS: IOP in 132 healthy eyes of 66 participants was measured using three different tonometry techniques: Goldmann applanation tonometer(GAT), Pascal dynamic contour tonometer(DCT), and ICare rebound tonometer(RT). CCT and corneal curvature were assessed. RESULTS: In healthy eyes, DCT presents significantly higher values of IOP than GAT(17.34±3.69 and 15.27±4.06 mm Hg, P<0.0001). RT measurements are significantly lower than GAT(13.56±4.33 mm Hg, P<0.0001). Compared with GAT, DCT presented on average 2.51 mm Hg higher values in eyes with CCT<600 μm and 0.99 mm Hg higher results in eyes with CCT≥600 μm. The RT results were lower on average by 1.61 and 1.95 mm Hg than those obtained by GAT, respectively. Positive correlations between CCT in eyes with CCT<600 μm were detected for all IOP measurement techniques, whereas a similar relationship was not observed in eyes with thicker corneas. A correlation between IOP values and keratometry in the group with CCT<600 μm was not detected with any of the tonometry methods. In thicker corneas, a positive correlation was found for GAT and mean keratometry values(R=0.369, P=0.005). CONCLUSION: The same method should always be chosen for routine IOP control, and measurements obtained by different methods cannot be compared. All analysed tonometry methods are dependent on CCT;thus, CCT should be taken into consideration for both diagnostics and monitoring.

Intraocular pressure elevation after intravitreal triamcinolone acetonide injection: a Meta-analysis

AIM：To report on intraocular pressure（IOP）after intravitreal injections of triamcinolone acetonide.·M ETHODS：Systematic literature review of studies that investigated the effects of an injection of triamcinolone Intravitreal triamcinolone acetonide on IOP was conducted according to the Cochrane Collaboration methodology and the reported effects have been analyzed with Meta-analysis.·RESULTS：We found that the IOP follows an inverted-U shape pattern over time starting with an average value of14.81±1.22 mm Hg before the injection,rising to a maximum of 19.48±2.15 mm Hg after one month of injection and falling down to 16.16±1.92 mm Hg after6mo.Moreover,country of study,age,previous history of glaucoma and gender compositions matter for crossstudy were different in reported IOP changes.·CONCLUSION：Our findings may be helpful in determining pressure elevation risk of intravitreal triamcinolone acetonide therapy as well as comparing it with those of more recent therapies such as the antivascular endothelial growth factor agents.

Surgical induced astigmatism correlated with corneal pachymetry and intraocular pressure: transconjunctival sutureless 23-gauge versus 20-gauge sutured vitrectomy in diabetes mellitus

AIM: To determine the difference of surgical induced astigmatism between conventional 20-gauge sutured vitrectomy and 23-gauge transconjunctival sutureless vitrectomy, and the influence of corneal pachymetry and intraocular pressure(IOP) on surgical induced astigmatism in diabetic patients.METHODS: This retrospective, consecutive case series consisted of 40 eyes of 38 diabetic subjects who underwent either 20-gauge or 23-gauge vitrectomy. The corneal curvature and thickness were measured with Scheimpflug imaging before surgery and 1wk; 1, 3mo after surgery. We compared the surgical induced astigmatism(SIA) on the true net power in 23-gauge group with that in 20-gauge group. We determined the correlation between corneal thickness change ratio, IOP and SIA measured by Pentacam. RESULTS: The mean SIAs were 1.082 ±0.085 D( mean ± SEM), 0.689 ±0.070 D and 0.459 ±0.063 D at postoperative 1wk; 1, 3mo respectively in diabetic subjects. The vitrectomy induced astigmatisms were declined significantly with time(F2,36=33.629, P =0.000)postoperatively. The 23-gauge surgery group induced significantly less astigmatism than 20-gauge surgery group(F1,37=11.046, P =0.020). Corneal thickness in diabetes elevated after surgery(F3,78=10.532, P =0.000).The linear regression analysis at postoperatively 1wk went as: SIA =-4.519 +4.931 change ratio(Port3) +0.026IOP(R2=0.46, P =0.000), whereas the rate of cornealthickness change and IOP showed no correlation with the change of astigmatism at postoperatively 1 and 3mo.CONCLUSION: There are significant serial changes in both 20-gauge and 23-gauge group in diabetic subjects.23-gauge induce less astigmatism than 20-gauge and become stable more rapidly than 20-gauge. The elevation of corneal thickness and IOP was associated with increased astigmatim at the early postoperative stage both in 23-gauge and 20-gauge surgery group.

Effect of simulated dynamic intraocular pressure on retinal thickness measured by optical coherence tomography after cataract surgery

AIM: To investigate the effect of simulated dynamic intraocular pressure (SDIOP) during uncomplicated phacoemulsification on postoperative macular and peripapillary retinal nerve fiber layer (RNFL) thickness. METHODS: Macular and RNFL thicknesses in one eye of patients (n=30) undergoing uncomplicated phacoemulsification were measured by optical coherence tomography preoperatively and 1 week postoperatively. The best-corrected visual acuity, SDIOP, irrigation time (IT), effective phacoemulsification lime, entire surgical duration, blood pressure, and heart rate were recorded. RESULTS: The mean SDIOP and IT was (74.9 +/- 27.4)cmH(2)O and (178.4 +/- 21.6) seconds respectively. We divided our patients into two groups based upon IT with greater than 90cmH(2)O (P>90IT). In Group A (n= 14), the P>90IT was greater than the mean P>90IT, and in Group B (n=16), the P>90IT was less than the mean P>90IT. For all patients there was a significant increase in macular thickness one week after cataract surgery (P=0.001). While the RNFL thickness tended to increase, the change was not significant. The postoperative macular thickness of Group A,(277.8 +/- 13.7)mu m, was significantly thicker than that of Group B, (267.9 +/- 15.0)mu m (P=0.004). The postoperative peripapillary RNFL thickness of Group A, (96.8 +/- 10.8)mu m, was not significantly different from Group B. For Group A, the change in macular thickness was positively correlated with P>90IT (R-2=0.524, P =0.02). There was no statistical difference in postoperative visual acuity between Groups A and B. CONCLUSION: After uncomplicated phacoemulsification, increased macular thickness is associated with the IT under high SDIOP. The effect of high SDIOP is limited to the sub-clinical level.

Influence of transient intraocular pressure elevation during laser in situ keratomileusis on rabbit retina thickness

AIMTo utilize tissue micro measurement to study the effect of transient high intraocular pressure (IOP) induced by different durations of suction during laser in situ keratomileusis (LASIK) on rabbit retina thickness.METHODSSixty healthy New Zealand white rabbits were randomly divided into a control group, and 3 negative-pressure suction groups (20s group, 45s group, and 3min group) and each group was comprised of 15 rabbits (30 eyes); the latter 3 groups were the transient high IOP models. The retinal tissue around the papilledema was separated. Hematoxylin and eosin (HE) staining was carried out to generate slices for light microscopy. The changes in the retina thickness values of each layer were measured for all animals in each group at different postoperative recovery periods and compared with the values recorded for the animals in the control group. The thickness of the retinal tissue showed a normal distribution. The ANOVA was performed by using SPSS13.0 statistic software.RESULTSIn the comparison between the 20s and 45s negative-pressure suction groups and the control group, no significant differences were observed, except at 14d. Significant difference was observed between the 3min negative-pressure suction group and the control group, and the retina thickness value of each layer reached a peak at 14d after repair.CONCLUSIONConventional negative suction during LASIK may not lead to significant changes in retinal tissue thickness; however, if the suction duration is increased to 3min, it will cause significant changes in retinal tissue thickness.

Eye rubbing-induced changes in intraocular pressure and corneal thickness measured at five locations, in subjects with ocular allergy

AIM: To assess the effects of eye rubbing on corneal thickness(CT) and intraocular pressure(IOP)measurements obtained 0-30 min after habitual eye rubbing in symptomatic patients.METHODS: Measurements of IOP and CT were obtained at five locations(central, temporal, superior,nasal and inferior) before, and every 5min for 30 min interval after 30 s of eye rubbing, for 25 randomly selected eyes of 14 subjects with ocular allergy and 11age-matched normals. Differences in measurements were calculated in each group [Baseline measurements minus measurements recorded at each time interval after eye rubbing(for IOP), and for each corneal location(for CT)]and comparison were then made between groups(allergic versus control) for differences in any observed effects.RESULTS: Within groups, baseline mean IOPs in the allergic patient-group(14.2 ±3.0 mm Hg) and in the control group(13.1±1.9 mm Hg) were similar at all times,after eye rubbing(P 】0.05, for all). The maximum reduction in IOP was 0.8 mm Hg in the control subjects and the maximum increase was also 0.8 mm Hg in the allergic subjects. Between groups(allergic versus control), the changes in IOP remained under 1 mm Hg at all times(P =0.2) after 30 min of eye rubbing. Between 0and 30 min of CT measurements after eye rubbing, the mean central CT(CCT), inferior CT(ICT), superior CT(SCT), temporal CT(TCT) and nasal CT(NCT) did not vary significantly from baseline values in the control and allergic-subject groups(P 】0.05, for both). Between both groups, changes in CT were similar at all locations(P 】0.05)except for the TC which was minimally thinner by about4.4 μm(P =0.001) in the allergic subjects than in the control subjects, 30 min following 30 s of eye rubbing.CONCLUSION: IOP measured in allergic subjects after30 s of habitual eye rubbing was comparable with that obtained in normal subjects at all times between 0 and30 min. Although, CT in the allergic subjects were similar to those of the control subjects at all times, it varied between +10 and-7.5 μm following eye rubbing, with the temporal cornea showing consistent reductions in thickness in the subjects with allergy. However, this reduction was minimal and was considered to not be clinically relevant.

Observation seasonal variation of intraocular pressure in young healthy volunteers

AIM:To investigate fluctuation of intraocular pressure(IOP)and seasonal variation of 24-hour IOP during one year in healthy participantsMETHODS:Totally 13 young healthy volunteers participated in this study.IOP was measured with Canon TX-20 at about 8:00-9:00 a.m.from Monday to Friday every week for a whole year.They also underwent 24-hour IOP examination every three months.Blood pressure,heart rate,temperature,humidity,atmosphere pressure,sunshine duration and other environment parameters were recorded.RESULTS:The yearly fluctuation curve showed IOP in the summer months were lower than other seasons.In the multivariable generalized estimating equation analysis,IOP had a negative correlation with both temperature and sunshine duration(P<0.05).There also was a seasonal effect on 24-hour IOP.However,all intraclass correlation coefficients values of minimum,maximum and average of the 24-hour IOP and each individual IOP were less than 0.30.CONCLUSION:IOP is trend to be higher in cold days than warm days.IOP have negative association with both environmental temperature and duration of sunshine.On a season-to-season basis,24-hour IOP is not highly reproducible in healthy volunteers.

Effect of persistent high intraocular pressure on microstructure and hydraulic permeability of trabecular meshwork

As the aqueous humor leaves the eye, it first passes through the trabecular meshwork （TM）. Increased flow resistance in this region causes elevation of intraocular pressure （IOP）, which leads to the occurrence of glaucoma. To quantitatively evaluate the effect of high IOP on the configuration and hydraulic permeability of the TM, second harmonic generation （SHG） microscopy was used to image the microstructures of the TM and adjacent tissues in control （normal） and high IOP conditions. Enucleated rabbit eyes were perfused at a pressure of 60 mmHg to achieve the high lOP. Through the anterior chamber of the eye, in situ images were obtained from different depths beneath the surface of the TM. Porosity and specific surface area of the TM in control and high IOP conditions were then calculated to estimate the effect of the high pressure on the permeability of tissue in different depths. We further photographed the histological sections of the TM and compared the in situ images. The following results were obtained in the control condition, where the region of depth was less than 55 μm with crossed branching beams and large pores in the superficial TM. The deeper meshwork is a silk-like tissue with abundant fluorescence separating the small size of pores. The total thickness of pathway tissues composed of TM and juxtacanalicular （JCT） is more than 100 p.m. After putting a high pressure on the inner wall of the eye, the TM region progressively collapses and decreases to be less than 40 μm. Fibers of the TM became dense, and the porosity at 34 μm in the high IOP condition is comparable to that at 105 μm in the control condition. As a consequent result, the permeability of the superficial TM decreases rapidly from 120 μm2 to 49.6 μm2 and that of deeper TM decreases from 1.66 μm2 to 0.57 μm2. Heterogeneity reflected by descent in permeability reduces from 12.4 μm of the control condition to 3.74 μm of the high IOP condition. The persistently high IOP makes the TM region collapse from its normal state, in which the collagen fibers of the TM are arranged in regular to maintain the physiological permeability of the outflow pathway. In the scope of pathologically high IOP, the microstructure of the TM is sensitive to pressure and hydraulic permeability can be significantly affected by IOP.