Recent Developments in Glaucoma

Central corneal thickness in children—does it help or hinder our evaluation of eyes at risk for glaucoma?

Open-angle glaucoma and systemic hypertension: The Blue Mountains eye study. Mitchell P, Lee AJ, Rochtchina E, Wang JJ. J Glaucoma 2004;13:319–326.

Background: Schlemm’s canal collaps and increased trabecular (especially juxtacalanicular) resistance play an important role in the development of glaucoma. Dilation of Schlemm’s canal and moderate trabecular extension promote restoration of natural aqueous outflow pathways. Previously we had developed first generation Schlemm’s canal expander (SKE-1) and proved its efficacy in decreasing intraocular pressure in open-angle glaucoma. Though, inappropriate size of the expander results in traumatic implantation. Thus, we developed second generation Schlemm’s canal expander (SKE-2) characterized by smaller length and diameter. Aim: To evaluate effectiveness of SKE-2 in decreasing intraocular pressure in open-angle glaucoma. Materials and methods: 25 patients (25 eye) were included. 13 patients (13 eyes) in the intervention group underwent glaucoma surgery with SKE-2 implantation. The results were compared with SKE-1 implantation in the control group (12 patients, 12 eyes). The groups were age-, sex and glaucoma stage-matched (p > 0.05). The patients were followed for 1 year. Outcome measures included intraocular pressure changes, complication rate, need for additional hypotensive therapies and repeat surgery. Results: Intraocular pressure changes, need for additional hypotensive therapies frequency of intra- and postoperative complications didn’t differ between the groups. Trabeculopuncture with yttrium aluminum garnet (YAG) laser as a second step procedure was needed in 2 cases (16%) in the control group and in 5 cases (38%) in the intervention group (p = 0.002). Conclusion: SKE-1 and SKE-2 are equally effective in reducing intraocular pressure in open-angle glaucoma. Though, after SKE-2 implantation, YAG laser goniopuncture is more frequently needed as a second step procedure.

Background: Glaucoma, the second most common cause of blindness and the main cause of irreversible blindness, has a significant impact on people all over the world. Primary open-angle glaucoma is the most prevalent glaucoma subtype among adults (40-80 years old). Primary angle-closure glaucoma is linked to the closure of the anterior chamber angle of the eye and is known to have a higher risk of bilateral blindness, which places a severe burden on families and society. Objectives: To determine the prevalence of glaucoma in adult patients and to determine common types of glaucoma and to find out the relationship between glaucoma and demographic characteristics of patients and determine common causes of glaucoma. Methods: Cross-sectional study design was adopted from 15 September 2024 to 15 April 2025 at Tikrit Teaching Hospital in Tikrit District, Salah Eden. To achieve the objectives of the present study. A purposive sample involving 300 glaucoma patients. Data collection tools composed from (6) parts, which includes the following: Part one demographic information of patients, Part two medical history, Part three lifestyle of patients with glaucoma, Part four signs and Symptoms of patients with glaucoma, Part five risk factors of patients with glaucoma, Part six daily activities of patients with glaucoma. The study results were examined using both a descriptive analysis and an inferential analysis procedure (e.g., Binomial test, Chi-Square test and Contingency Coefficients) a p-value of <0.05 was detected to be statistically significant. Result: The results shows 143(53.0%) from sample were male and 127(47.0 %) were female. With regard to the age group high numbers at the ages falling within the third, fourth and fifth age groups, since they are accounted 174(64.44%), most of them were a housewife and they are accounted 106(39.3%) and of them having high numbers at the low education levels of under a primary school, since they are accounted 151(55.9%). More than half of studied sampled have a prevalence of "Primary (Idiopathic) open angle glaucoma" and represent 138(51.1%), while prevalence of "Pesudoexfoliation related open angle glaucoma" type are accounted 35(13.0%). Also the results shows 103(38.1%) have Diabetes Mellitus, 139(51.5%) have increase Blood Pressure item, 120(44.4%) have previous eye surgery and 253(93.7%) have elevated of intraocular pressure (IOP). Conclusion: This study concludes risk factors and prevalence of glaucoma may increase with age and most risk factors for glaucoma were diabetes mellitus, increase blood pressure, previous eye surgery and increase intra ocular pressure while the most prevalence types were Primary (Idiopathic) open angle glaucoma and Pesudoexfoliation related open angle glaucoma.

The Ocular Response Analyzer (ORA) is a new instrument that measures the corneal biomechanical response (corneal hysteresis, CH) to rapid indentation by an air jet. CH is the difference in applanation pressures (P1, P2) between the rising and falling phases of the air jet. The investigation had two parts: a characterization study and a validation study. In the characterization study, the purposes were to investigate the intraocular pressure (IOP)-dependence of CH and to characterize the performance of the ORA. In the validation study, the purposes were to investigate the association between CH and both age and central corneal thickness (CCT) and the agreement between ORA and Goldmann applanation tonometer (GAT) IOP measurements. For the characterization study, data were collected from 105 untreated subjects (45 ocular hypertensive patients and 60 normal subjects; mean age, 60 years, range, 26-82). GAT and ORA measurements were performed before and after IOP lowering of one randomly selected eye with apraclonidine drops. The change in P1 and P2 (arbitrary units) in relation to change in GAT IOP was analyzed to calibrate the instrument. The relation between P1, P2, and CCT was explored and ORA IOP was derived from the analyses. For the validation study, ORA and GAT IOP and CCT were measured in 144 eyes of 144 untreated subjects (mean age, 58 years; range, 19-83). The characterization calculations were applied to the dataset and values of CH and ORA IOP were calculated. The relationship between CH and both subject age and CCT was determined. The associations between CH and CCT and between ORA and GAT IOPs, were investigated by linear regression analysis. The agreement between measuring devices was calculated. In the characterization study, P1 changed by 6.41 arbitrary units for every 1-mm Hg change in GAT IOP. CH (P1 - P2) changed by -1.60 arbitrary units for every 1-mm Hg change in GAT IOP. For each unit change in P2, P1 changed by 1.27 units. From this association a new IOP-independent corneal factor was derived [P1 - (P2/1.27)] and is termed the corneal constant factor (CCF; mm Hg). ORA IOP normalized for CCF was defined as P2 - CCF (mm Hg). The CCF (mm Hg) was associated with CCT (micrometers) and with age: CCF = [(0.036 . CCT) - (0.028 . age)] + 1.06 (adjusted r2 = 0.34; P < 0.0001 for CCT, P = 0.007 for age). Normalized ORA IOP measurements were not associated with CCT. GAT IOP was associated with CCT and CCF-more strongly with the latter: GAT IOP = (0.03 . CCT)+1.52 (r2 = 0.06, P = 0.002); GAT IOP = (0.65 . CCF) + 4.5 (r2 = 0.13, P < 0.0001). The mean difference (95% limits of agreement) between GAT and normalized ORA IOP was 0.1 (-6.6 to +6.8) mm Hg. The CCF describes an IOP-independent biomechanical property of the cornea that increases with thicker CCT and decreases with greater age. It is moderately strongly associated with CCT and yet explains more of the interindividual variation in GAT IOP than does CCT. Normalized ORA IOP measurements are not associated with CCT.

To compare intraocular pressure (IOP) control in eyes with or without clear corneal phacoemulsification following trabeculectomy. The study group included 30 eyes that underwent uneventful clear corneal phacoemulsification and foldable intraocular lens implantation following trabeculectomy without antimetabolites. Thirty eyes that had undergone filtering surgery without cataract extraction were selected as controls. Case and control groups were matched with respect to age, gender, IOP, number of glaucoma medications, glaucoma type (primary open-angle glaucoma/pseudoexfoliative glaucoma), trabeculectomy time and follow-up. Comparisons between the study and control groups (intergroup) and within the same group at different time-points (intragroup) were performed for IOP, glaucoma medications and bleb morphology. Success rates were investigated by Kaplan-Meier survival analysis and the factors influencing final success by logistic regression. Intraocular pressure (p = 0.04) and glaucoma medications (p = 0.001) increased during an average follow-up of 26.1 +/- 9.9 months in both groups. Intragroup differences became statistically significant after the 6-month visit, but intergroup differences remained insignificant. Bleb height decreased significantly following phacoemulsification in the study group (p = 0.017). Success rates decreased with time in both groups, with no intergroup difference (p = 0.46). The final success rate was negatively correlated with IOP and number of glaucoma medications used at the study entry, while there was a positive correlation between the baseline and final success rates. Trabeculectomy success decreased in a time-dependent manner in eyes with and without subsequent phacoemulsification. Uncomplicated clear corneal phacoemulsification was not found to have any additional unfavorable influence on IOP control in eyes with filtering blebs.

Background Measurement of intraocular pressure (IOP) plays a central role throughout ophthalmology. It is part of routine ophthalmologic examinations and important in the management and follow-up of patients with glaucoma. While elevated IOP remains the most important risk factor for development and progression of open angle glaucoma, at least half of the population diagnosed with open angle glaucoma is asymptomatic. Objectives The aim of our study is to compare the accuracy of intraocular pressure measurement before and after Laser in situ keratomeulsis (LASIK) surgery using three different types of Tonometers: Goldmann Applanation tonometry (GAT), Non contact tonometry (NCT) and Rebound tonometry (I care), considering the change in the central corneal thickness (CCT). Patients and Methods In this study Eighty eyes of 40 patients with mean age of 27.00±6.00 years were scheduled for LASIK..Central corneal thickness before and after surgery was obtained by Ultrasound (US) pachymetry.IOP values were measured before and after surgery using three different types of Tonometers: Goldmann Applanation tonometry, Non contact tonometry and Rebound tonometry. Results The results revealed that lower post-operative IOP measurements using all techniques. The least affected technique was Non –contact with IOP change 16%, followed by GAT with IOP change 18%, and finally Rebound with IOP change 19 %, respectively. The percentage of change in CCT between pre- and post- LASIK surgery measured with the Ultrasound pachymetry was statistically highly significant. There was a clinical significant correlation between Percentage of tissue ablation (PTA) and IOP change for GAT, NCT and rebound tonometry. Also, there was a significant correlation between Residual stromal bed (RSB) and IOP change for GAT and NCT. There was no clinical significant correlation between Ablation depth (AD) and percentage of change of IOP measurements pre and post LASIK, except for IOP measured with GAT when AD &amp;lt; 40.00 µm. Conclusion Refractive surgery causes significant lowering of IOP as measured using Goldmann applanation tonometry, non contact tonometry and rebound tonometry. The least affected tonometry post LASIK is non contact tonometry. The reduction was correlated to the percentage of tissue ablated. The ideal method to measure IOP in post-LASIK patients would be a device that is free of corneal factors.

The most frequent cause for glaucoma surgery failure apart from the progression of dystrophic changes in the eye’s drainage system is morphological changes in connective tissue structures that increase the risk of scarring at the operation site. Since currently available preventive measures, that are either based on medically affecting the wound healing process (e.g. metabolic antagonists) or method improvements, do not always give the intended result, there are also other directions of glaucoma research, one of which focuses on the application of drainage devices and systems. PURPOSE: to study the efficacy and safety of iGen drainage device in primary open-angle glaucoma surgery. METHODS: The study group included 35 male and 51 female patients aged 55 to 79 years (mean age 65.9±9 years). All the patients of the study group (86 patients, 86 eyes) underwent an iGen drainage device implant. Among the patients, 37 (43.1%) had stage II glaucoma, 49 (56.9%) — stage III. Intraocular pressure (IOP) was moderately elevated in 52 patients (60.5%) and significantly elevated in 34 patients (39.5%). Mean IOP prior to the operation was 34.6±9.2 mm Hg with the minimum of24.7 mm Hg and the maximum of56.5 mm Hg. RESULTS. One week follow-up showed mean IOP levels of 15.1±11.3 mm Hg. At day 30 of the post-surgical followup, IOP in the study group increased by 2–3 mm Hg and in average amounted to 17.8±6.4 mm Hg. Further observation showed no IOP increase, and at 12 months it equaled 18.8±2.3 mm Hg. Absolute success of iGen implantation was accomplished in 37 (42.9%) patients. Qualified success (IOP normalization without additional antihypertensive therapy + IOP normalization with additional antihypertensive therapy by 1.8 medications in average) was achieved in 71 (82.1%) patients. Complications frequency and characteristics depended on the initial clinical status and included ciliochoroidal detachment (10.4%), hyphema (10.4%), transient hypertension (1.2%). CONCLUSION: The choice of explant drainage in repeated glaucoma surgery depends on predominant localization of cicatricial blockade of the outflow tracts created during previous surgeries. In cases when conjunctival-scleral adhesions served as the obvious cause of the surgery failure, iGen collagen drainage is preferable as having integral success rate of 82.1%.

Background: Primary open-angle glaucoma (POAG) is the most common type of glaucoma. Increasing age, elevated intraocular pressure (IOP), and a positive family history are risk factors for POAG incidence. Elevated IOP is a major risk factor for glaucoma development and progression. The mechanism for IOP changes with body position is not completely understood. Objective: The present study was aimed to investigate the effects of different body positions on IOP in patients with primary open-angle glaucoma. Patients and methods: This prospective study included a total of 60 glaucoma and glaucoma suspect patients and 30 normal subjects, attending at Aswan University Hospital. Subjects were divided into 3 groups (normal, glaucoma suspect and primary open angle glaucoma). Each subject underwent thorough ophthalmological evaluation including best corrected visual acuity, slit lamp biomicroscopy, tonometry, gonioscopy, and dilated fundus evaluation. The Perkin's tonometer was used to measure IOP in different sleeping positions (at zero o degree, at 30o degree and 45o) positions. In all these positions, baseline IOP as well as after 30 minutes IOP was measured. Results: Comparison of both age and gender across different groups showed that there were no statistically significant differences among them. In terms of the IOP, comparing all of the three groups at baseline showed that there was a statistically significant difference across groups (p < 0.0001). There was a statistically significant reduction of IOP in 30 and 45 degree semi sitting positions compared to supine positions in all study groups. Conclusion: It could be concluded that certain sleeping positions appear to be associated with changes in intraocular pressure. It is essential not to overlook these short term fluctuations particularly in patients with primary open angle glaucoma as they can affect progression of the disease.

Effects of Corneal Thickness, Corneal Curvature, and Intraocular Pressure Level on Goldmann Applanation Tonometry and Dynamic Contour Tonometry

Ocular perfusion pressure (OPP) has been suggested as a possible risk factor for the development and progression of primary open angle glaucoma (POAG). To determine the distribution of OPP and its relationship with intraocular pressure (IOP) in Nigerian patients with POAG. : A descriptive and comparative survey was adopted. A total of 120 subjects, 60 newly diagnosed POAG and 60 non-glaucomatous (NG) subjects, aged 40 years and above, who attended the ophthalmic clinic of University of Nigeria Teaching Hospital Enugu were recruited over a six-month period in 2019. All the subjects had ocular examination, blood pressure and IOP measurements. Statistical package for social sciences software version 25 was used for data analysis. Chi-square test, independent samples t-test, and Mann-Whitney U test were used for comparison while Pearson correlation and simple linear regression were used to ascertain the relationship. A P value of <0.05 was considered significant. The mean age of the participants was 57.9 + 11.9 years. The mean OPP was found to be significantly lower in the POAG subjects (Right eye, R = 43.6 ± 12.6, Left eye, L = 41.9 ± 13.3) mmHg compared with the NG group (R = 53.9 ± 10.9, L = 53.7 ± 10.9) mmHg (p < 0.001 for both eyes). A significant inverse relationship was observed between OPP and IOP in POAG subjects (p < 0.001), while there was none in NG subjects. OPP was lower in POAG subjects than in NG subjects. The observed relationship suggests that reduced OPP may play a role in the development of POAG.

Lowering of Intraocular Pressure After Phacoemulsification in Primary Open-Angle and Angle-Closure Glaucoma: A Bayesian Analysis.

To observe the diurnal variations of intraocular pressure (IOP) measured with dynamic contour tonometer (DCT) in primary open angle glaucoma (POAG) patients, normal tension glaucoma (NTG) patients, and healthy controls, and to compare the differences of diurnal variation curves between the two eyes of each subject and define the distribution of the peak of IOP; to analyze the diurnal variation range of ocular pulse amplitude (OPA) and compare the differences among the POAG and NTG patients and healthy controls. DCT was used to measure the diurnal variations of IOP and OPA in the two eyes of 18 POAG patients, 17 NTG patients and 30 normal controls at 5:00, 7:00, 10:00, 14:00, 18:00, and 22:00 and the distribution of the peak IOP was observed. The range of the diurnal variation of OPA was identified. The diurnal variation curves of IOP were different among the POAG patients, NTG patients, and normal people, and also between the two eyes of each subject. Four right eyes (13.3%) and 6 left eyes (20.0%) of the healthy controls, 4 right eyes (23.5%) and 5 left eyes (29.4%) of the NTG patients, and 5 right eyes (27.8%) and 4 left eyes (22.2%) of the POAG patients reached the peak IOP values in out-office period. Diurnal variation of OPA was detected in both the patients and controls, and the variation curves were different within different groups sampled and between the two eyes of each subject. The diurnal OPA range of the right and left eyes of the POAG group were (2.1 +/- 1.3) mm Hg, and (2.4 +/- 1.9) mm Hg respectively, significantly larger than those of the normal controls [(1.1 +/- 0.5) mm Hg and 1.2 +/- 0.5) mm Hg respectively], and those of the NTG group [(1.1 +/- 0.8) mm Hg and (1.0 +/- 0.5) mm Hg) respectively] (all P < 0.01). OPA has diurnal variation. The diurnal variation of the POAG patients is the largest. NTG patients and normal controls have asymmetric IOP and OPA diurnal variations. The two eyes of the same individual cannot always be treated as the same. The value of IOP measured in the office-time cannot completely represents the 1 d IOP.

The effect of the design and fitting ofsoft lenses on corneal physiology

Background Rabbits are commonly used as animal models for the evaluation of drugs and surgery to lower intraocular pressure (IOP).The accuracy of IOP measurement is therefore critical in the analysis of data and subsequent extrapolation to humans.An accurate method to measure rabbit IOP is intracameral manometry,but it is an invasive way.Schiotz,Perkins and Rebound were often used in clinic.However,their accuracy in measuring rabbit IOP in experimental study is unclear. Objective The purpose of this study was to investigate the accuracy of IOP measured by Schiotz tonometer,Perkins tonometer and Rebound tonometer relative to intracameral manometry in New Zealand white rabbits. Methods The central corneal thickness (CCT),corneal curvature (CC),axial length (AL),anterior chamber depth (ACD), lens thickness (LT) and scleral thickness (ST) were respectively measured in 8 eyes of 8 healthy New Zealand white rabbits with lenstar900 and ultrasound biomicroscopy (UBM).The actual IOP was measured with a 24G needle inserted the anterior chamber and connected to a pressure transducer under the general anesthesia,the IOP gradient was set with a 24G needle inserting the vitreous cavity and connecting to a container with balanced salt solution(BSS).Then,comparative measurements at the same pressures were performed with three types of tonometers.The IOP values from Schiotz tonometer,Perkins tonometer and Rebound tonometer were calibrated based on actual IOP from intracameral manometry and eyeball physiological parameters by multiple regression equation. Results The mean of CCT,CC,AL,ACD,LT and ST was (338.96±21.52) μm,(51.68±1.66) D,(14.63±0.19) mm,(2.22±0.04) mm,(6.15±0.10) mm and (339.80±47.41) μm.Compared with the intracameral manometry value (IMV),the error range was (17.08±11.22) mmHg in the Schiotz tonometer value (STV),(25.81±12.43) mmHg in the Perkins tonometer value (PTV) and (22.50±11.47) mmHg in the Rebound tonometer value (RTV),with significant differences between them(t=10.54,14.39,13.59,all at P<0.05).Compared with IMV,the 95% limits of agreement of three portable tonometer values is larger,and three portable tonometer values had the greater measurement error with elevated IOP gradient.The regression equations was IOP=141.015+1.570×STV+0.122×CCT-3.480×CC between actual IOP and STV (R=0.92,P=0.00),IOP=-33.323+1.914×PTV+0.133×CCT between actual IOP and PTV(R=0.88,P=0.00),IOP=160.395+1.866×RTV+0.201×CCT+34.554×LT-2.649×CC+0.063×ST between actual IOP and RTV (R=0.95,P=0.00). Conclusions The physiological parameters of rabbit eyeball are obviously different from human. The STV, PTV and RTV have a great measuring error in comparson with actual IOP, and therefore it is necessary to correct STV, PTV and RTV based on the ocular physiology parameters in experimental study. Key words: Bio-measurment; Intraocular pressure; Intracameral manometry; Tonometer; Regression equation; Rabbit