Effect of Latanoprost on Cultured Porcine Corneal Stromal Cells

Effects of topical prostaglandin therapy on corneal layers thickness in primary open-angle glaucoma patients using anterior segment optical coherence tomography

PURPOSE

To evaluate the effects of latanoprost, bimatoprost, and travoprost eye drops and their preservatives on each corneal layer thickness in patients with primary open-angle glaucoma (POAG).

METHODS

We retrospectively analyzed 79 eyes of 79 patients with POAG who were receiving prostaglandin therapy. Patients were divided into three subgroups according to monotherapy with latanoprost, bimatoprost, and travoprost during a mean of 43.14 ± 19.12 months follow-up period. In addition, the central corneal epithelial thickness (CET), central corneal stromal thickness (CST), and total central corneal thickness (CCT) were measured by anterior segment optical coherence tomography (AS-OCT) at baseline and every six months after treatment initiation at each visit between 9 and 12 o'clock in the morning. Furthermore, intraocular pressure (IOP) was measured with Goldmann applanation tonometry (GAT) after AS-OCT measurements at each visit.

RESULTS

All three groups were not significantly different in age, gender, follow-up period, and mean intraocular pressure values (p > 0.05 for all). The reduction of CCT in the latanoprost, bimatoprost, and travoprost groups was 6.53 ± 3.17, 18.59 ± 8.42, and 10.1 ± 1.13 µm, respectively. The decrease in CST values was 4.65 ± 1.54, 15.84 ± 7.47, 9.69 ± 1.45 µm, and CET values were 1.88 ± 1.66, 2.75 ± 0.73, 0.41 ± 0.54 µm in all groups, respectively. A statistically significant thinning was observed in all corneal layers (p < 0.05) except the CST values in the latanoprost group and CET values in the travoprost group. However, no significant difference was found in the average reduction of CET, CST, and CCT values among the three groups (p > 0.05).

CONCLUSION

Topical treatment with latanoprost, bimatoprost, and travoprost affects each layer of the cornea separately according to the active and protective substances contained in these eye drops. On the other hand, the thinning effect on the corneal layers was similar in these three drugs because there was no significant difference between the three groups in the total amount of thinning of the corneal layers during the follow-up period.

Effect of travoprost, latanoprost and bimatoprost PGF2α treatments on the biomechanical properties of in-vivo rabbit cornea

Prostaglandin F2α analogues (PGF2α), one of the most commonly prescribed classes of hypotensive agents, could decrease collagen fibril density and remodel the extracellular matrix in cornea. We hypothesized that PGF2α's would induce corneal softening, reduce the accuracy of intraocular pressure (IOP) measurement and lead to uncertainty in the effectiveness of the therapy. We determined the stress-strain behavior of rabbit cornea after PGF2α usage and evaluated the effect of biomechanical changes associated with PGF2α treatment on IOP measurements by Goldmann Applanation Tonometry (GAT). The tangent modulus decreased after PGF2α treatment, while the stromal interfibrillar spacing increased. PGF2α was shown to also affect the lateral eye with lower effect, which did not undergo direct eyedrop treatment. Significant decreases in the numerical predictions of GAT-IOP were predicted in all treated groups relative to control groups. Different PGF2α's (travoprost, latanoprost and bimatoprost) were associated with different extents of reduction in tissue stiffness and changes in corneal microstructure. PGF2α-induced changes in corneal mechanical properties could reduce the accuracy of IOP measurement and may cause an overestimation of the effect of PGF2α in lowering IOP, possibly leading to uncertainties in glaucoma management.

Do topical antiglaucoma drugs affect the cornea?

To investigate effects of beta blocker (BB; timolol or betaxolol), latanoprost, and latanoprost-timolol combination (LTC) drugs on corneal endothelial cell density (ECD) and central corneal thickness (CCT) in primary open-angle glaucoma (POAG) patients. Sixty-one patients in BB group, 64 patients in latanoprost group, 59 patients in LTC group, and 58 healthy cases in control group were included. Intraocular pressures (IOP), ECDs, and CCTs of groups were recorded at initial (pre-treatment) period, first and third years after treatment, and comparisons were done. In groups, changes of ECDs according to time were not significant (p > 0.05). In BB and control groups, changes of CCTs according to time were not significant (p > 0.05). In latanoprost and LTC groups, CCTs in both first and third years were significantly thinner than initial CCTs (p = 0.039 for latanoprost, p = 0.041 for LTC at first year; p = 0.018 for latanoprost, p = 0.032 for LTC at third year). In latanoprost and LTC groups, CCTs of patients using drugs for 1 year were similar to those of patients using drugs for 3 years (p > 0.05). In our study, uses of BB, latanoprost or LTC did not affect ECD. BB drugs had no effect on CCT. Although latanoprost and LTC appeared to reduce CCT at 3-year follow-up from the statistical point of view, this 8-10 μm difference in CCT was not clinically significant.

Omidenepag Isopropyl Versus Latanoprost in Primary Open-Angle Glaucoma and Ocular Hypertension: The Phase 3 AYAME Study

PURPOSE

To evaluate the efficacy and safety of omidenepag isopropyl (OMDI), a selective, non-prostaglandin, prostanoid EP2 receptor agonist, in Japanese patients with primary open-angle glaucoma (POAG) or ocular hypertension (OHT).

DESIGN

Phase III, randomized, investigator-masked, active-controlled, parallel-group, noninferiority study (ClinicalTrials.govNCT02623738).

METHODS

After a washout period of 1-4 weeks, eligible patients were randomized (1:1) to OMDI 0.002% or latanoprost 0.005% once daily for 4 weeks. Intraocular pressure (IOP) was measured at 9:00 AM, 1:00 PM, and 5:00 PM at weeks 1, 2, and 4. The primary endpoint was the change from baseline in mean diurnal IOP at week 4. The noninferiority margin for OMDI versus latanoprost was 1.5 mm Hg. Adverse events (AEs) were recorded.

RESULTS

Of the 190 patients randomized, 189 had at least 1 post-baseline IOP measurement. At baseline, patients who received OMDI or latanoprost had a mean ± SD diurnal IOP of 23.78 ± 1.73 mm Hg and 23.40 ± 1.51 mm Hg, respectively. At week 4, least-squares mean ± SE reduction in IOP from baseline with OMDI (-5.93 ± 0.23 mm Hg) was noninferior to that of latanoprost (-6.56 ± 0.22 mm Hg; 95% confidence interval between groups: 0.01-1.26). The most frequently reported treatment-related ocular AEs (OMDI vs latanoprost) were conjunctival hyperemia (23/94 patients [24.5%] vs 10/96 patients [10.4%]), corneal thickening (11/94 patients [11.7%] vs 1/96 patients [1.0%]), and punctate keratitis (0/94 patients vs 5/96 patients [5.2%]). No serious AEs were observed in either group, and there were no discontinuations related to the study drug.

CONCLUSIONS

OMDI 0.002% was noninferior to latanoprost 0.005% in reducing IOP in patients with OHT or POAG and was well tolerated.

The changes of corneal biomechanical properties with long-term treatment of prostaglandin analogue measured by Corvis ST

BACKGROUND

To investigate the corneal biomechanical changes in primary open angle glaucoma (POAG) patients treated with long-term prostaglandin analogue (PGA).

METHODS

One hundred eleven newly diagnosed POAG patients, including 43 high tension glaucoma (HTG) and 68 normal tension glaucoma (NTG), were measured by Corvis ST to obtain intraocular pressure (IOP), central corneal thickness (CCT) and corneal biomechanical parameters at baseline and at each follow-up visit after initiation of PGA treatment. The follow-up measurements were analyzed by the generalized estimate equation model with an exchangeable correlation structure. Restricted cubic spline was employed to estimate the dose-response relation between follow-up time and corneal biomechanics.

RESULTS

The mean follow-up time was 10.3 ± 7.02 months. Deformation amplitude (β = -0.0015, P = 0.016), the first applanation velocity (AV1, β = -0.0004, P = 0.00058) decreased and the first applanation time (AT1, β = 0.0089, P < 0.000001) increased statistically significantly with PGA therapy over time after adjusting for age, gender, axial length, corneal curvature, IOP and CCT. In addition, AT1 was lower (7.2950 ± 0.2707 in NTG and 7.5889 ± 0.2873 in HTG, P = 0.00011) and AV1 was greater (0.1478 ± 0.0187 in NTG and 0.1314 ± 0.0191 in HTG, P = 0.00002) in NTG than in HTG after adjusting for confounding factors.

CONCLUSIONS

Chronic use of PGA probably influences the corneal biomechanical properties directly, which is to make cornea less deformable. Besides, corneas in NTG tended to be more deformable compared to those in HTG with long-term treatment of PGA.

Biomechanical Effects of Two Forms of PGF2α on Ex-vivo Rabbit Cornea

PURPOSE

To investigate the biomechanical effects of two synthetic prostaglandin F2α analogues (PGF2α), namely Travoprost and Tafluprost, on the ex-vivo rabbit cornea.

MATERIALS AND METHODS

Ninety-six eyes of 48 Japanese white rabbits were divided into 3 equal groups randomly; the Travoprost treated group (Tra), the Tafluprost treated group (Taf) and the control group (Co). Eyes in Tra and Taf groups were preserved in storage medium for 10 days with 1:10 Travoprost and Tafluprost diluents, respectively; while the Co eyes were preserved in a similar but PGF2α-free medium. Twenty-four corneas of each group were tested under inflation conditions with up to 30 mmHg posterior pressure. The pressure-deformation data obtained experimentally were used in an inverse analysis process to derive the stress-strain behavior of the tissue, using which the tangent modulus, a direct measure of the tissue's material stiffness, was calculated. The remaining eight specimens of each group were analyzed using electron microscopy for fibril diameter and interfibrillar spacing.

RESULTS

Although the central corneal thickness increased significantly in the three groups after storage (p < .01), it was similar in all groups both before (p = .598) and after storage (p = .181). After treatment with Travoprost and Tafluprost, the corneas exhibited lower tangent modulus (by 29.2% and 29.8%, respectively, at 6 kPa stress) and larger stromal interfibril spacing (by 21.9% and 23.6%) compared with the control group. There was no significant change in fibril diameter with either Travoprost or Tafluprost treatment (p = .769).

CONCLUSIONS

The results demonstrated significant reductions in tangent modulus and increases in interfibrillar spacing, which were of similar magnitudes, with the application of two different forms of PGF2α.

Matrix Metalloproteinases and Glaucoma Treatment

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade extracellular matrix (ECM) components such as collagen and have important roles in multiple biological processes, including development and tissue remodeling, both in health and disease. The activity of MMPs is influenced by the expression of MMPs and tissue inhibitors of metalloproteinase (TIMPs). In the eye, MMP-mediated ECM turnover in the juxtacanalicular region of the trabecular meshwork (TM) reduces outflow resistance in the conventional outflow pathway and helps maintain intraocular pressure (IOP) homeostasis. An imbalance in the MMP/TIMP ratio may be involved in the elevated IOP often associated with glaucoma. The prostaglandin analog/prostamide (PGA) class of topical ocular hypotensive medications used in glaucoma treatment reduces IOP by increasing outflow through both conventional and unconventional (uveoscleral) outflow pathways. Evidence from in vivo and in vitro studies using animal models and anterior segment explant and cell cultures indicates that the mechanism of IOP lowering by PGAs involves increased MMP expression in the TM and ciliary body, leading to tissue remodeling that enhances conventional and unconventional outflow. PGA effects on MMP expression are dependent on the identity and concentration of the PGA. An intracameral sustained-release PGA implant (Bimatoprost SR) in development for glaucoma treatment can reduce IOP for many months after expected intraocular drug bioavailability. We hypothesize that the higher concentrations of bimatoprost achieved in ocular outflow tissues with the implant produce greater MMP upregulation and more extensive, sustained MMP-mediated target tissue remodeling, providing an extended duration of effect.

Changes in spectral parameters of corneal pulse following canaloplasty

PURPOSE

To ascertain whether changes in the spectral content of the corneal pulse (CP) signal, measured in vivo in primary open-angle glaucoma (POAG) patients, indirectly reflect changes in corneal biomechanics after canaloplasty.

METHODS

Fifteen eyes of 15 POAG patients who underwent canaloplasty combined with phacoemulsification were enrolled. Standard ophthalmic examinations were conducted before washout, pre-operatively, at days 1, 7, and 1, 3, 6, and 12 months after surgery. Non-contact measurements of the CP signal were performed at pre-washout, pre-operatively, and at 3, 6, and 12 months post-operatively. Then, amplitudes of the CP first five harmonics associated with the heart rate were estimated. Temporal changes of all considered parameters were tested at a Bonferroni-adjusted significance level set to 0.005.

RESULTS

A decrease in the amplitude of the first harmonic and an increase in the normalized amplitude of the third harmonic (A_CP3n) of the CP signal were noticed between the pre-washout and the pre-operative stages (p = 0.003 and p = 0.004, respectively). This corresponds to an increase in median intraocular pressure (IOP) values by 6.0 mmHg (p = 0.0045). After surgery, A_CP3n reached the highest value at 3 months post-operatively, compared with pre-washout level (p = 0.0045).

CONCLUSIONS

Alterations in corneoscleral stiffness caused by surgery are reflected in changes in the A_CP3n value. Hence, post-operative corneal biomechanics could be monitored indirectly by this supporting indicator that can be used to estimate the time at which measures of IOP are no longer biased by the changed cornea boundary conditions caused by canaloplasty.

CLINICAL TRIALS REGISTRATION

NCT02908633.

Comparison of intraocular pressure adjusted by central corneal thickness or corneal biomechanical properties as measured in glaucomatous eyes using noncontact tonometers and the Goldmann applanation tonometer

Purpose

To investigate the correlation coefficients between intraocular pressure (IOP) before and after adjusting for central corneal thickness (CCT) and corneal biomechanical properties.

Patients and methods

A total of 218 eyes of 218 patients with primary open-angle glaucoma (mean age =71.5 years; mean spherical equivalent =−0.51 D; mean deviation determined by Humphrey visual field analyzer =−3.22 dB) were included in this study. The tIOP and tIOPCCT, which were adjusted by the CCT (with tIOP meaning IOP not adjusted by CCT, as determined using the CT-1P; and tIOPCCT meaning IOP adjusted by CCT, as determined using the CT-1P), were determined using a noncontact tonometer. The IOPg and IOPCCT, which were adjusted by CCT, and IOPcc adjusted by corneal biomechanical properties were determined using a Reichert 7CR (with IOPg meaning IOP not adjusted by CCT or corneal biomechanical properties, as determined using the Reichert 7CR; IOPCCT meaning IOP adjusted by CCT, as determined using the Reichert 7CR; and IOPcc meaning IOP adjusted by corneal biomechanical properties, as determined using the Reichert 7CR). The GT and GTCCT adjusted by CCT were determined using a Goldmann applanation tonometer (with GT meaning IOP not adjusted by CCT, as determined using the Goldmann applanation tonometer; and with GTCCT meaning IOP adjusted by CCT, as determined using the GAT). Pearson’s correlation coefficients among the IOPs were calculated and compared. P-values <0.05 were considered as statistically significant.

Results

The tIOP, tIOPCCT, IOPg, IOPCCT, IOPcc, GT, and GTCCT were 14.8±2.5, 15.0±2.4, 13.1±3.2, 13.3±3.1, 13.7±2.9, 13.2±2.4, and 13.4±2.3 mmHg (mean ± standard deviation), respectively. The correlation coefficient between tIOPCCT and tIOP (r=0.979) was significantly higher than that between tIOPCCT and the other IOPs (r=0.668–0.852; P<0.001, respectively). The correlation coefficient between IOPCCT and IOPg (r=0.994) or IOPcc and IOPg (r=0.892) was significantly higher than that between IOPCCT or IOPcc and the other IOPs (r=0.669–0.740; P<0.001, respectively). The correlation coefficient between GTCCT and GT (r=0.989) was significantly higher than that between GTCCT and the other IOPs (r=0.669–0.740; P<0.001, respectively).

Conclusion

The IOP adjusted by CCT or corneal biomechanical properties depends on the measurement instrument itself, rather than the adjustment methods, for eyes of patients with primary open-angle glaucoma.

5-Fluorouracil-Induced Apoptosis Changes in Cultured Corneal Epithelial Cells

PURPOSE

Repeated subconjunctival injections with 5-fluorouracil (5-FU) after trabeculectomy are used in glaucoma patients for the inhibition of overproliferation in wound site. Thus, a certain amount of the drug may penetrate into epithelial layer, where it causes toxicity to corneal epithelial cells. The aim of this study was to evaluate the toxic effects of 5-FU and mechanisms of drug-induced apoptosis in cultured corneal epithelial cells.

METHODS

Cellular damage and the caspase pathway were estimated with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The apoptotic characteristics were detected by flow cytometry, a TUNEL test, and western blotting in cultured corneal epithelial cells.

RESULTS

The results indicated that 5-FU was toxic to corneal epithelial cells in a time- and dose-dependent manner. Pretreatment with a general caspase inhibitor (Z-VAD-FMK), a caspase-8 inhibitor (Z-IETD-FMK), and a caspase-9 inhibitor (Z-LEHD-FMK) reversed 5-FU-induced cellular damage. Following exposure to 5-FU, a flow cytometric assay with MitoLight dye demonstrated the significant loss of mitochondrial membrane potential. A positive TUNEL test revealed that cellular DNA apoptosis occurred following exposure to 0.5, 1, and 5 mg/mL 5-FU for 15 h. Positive annexin V-FITC and negative propidium iodide (PI) staining indicated that the cell membrane exhibited apoptosis upon exposure to 1 and 5 mg/mL 5-FU for 15 h. The western blot assay demonstrated upregulation of the p21 protein but downregulation of the Bcl-2 proteins induced by 5-FU.

CONCLUSION

These data reveal that 5-FU-induced cellular apoptosis in corneal epithelial cells may be mediated through caspase-8, caspase-9, and mitochondria-regulated pathways, as well as by upregulation of p21 and downregulation of Bcl-2-dependent signal transduction pathways.

Decreased keratocyte density and central corneal thickness in primary open-angle glaucoma patients undergoing treatment with topical prostaglandin analogues

Purpose:

To evaluate whether prostaglandin (PG) analogue use is associated with alterations in keratocyte density and central corneal thickness (CCT) in subjects with primary open-angle glaucoma (POAG).

Materials and Methods:

Thirty-five POAG patients treated with PG analogues for >2 years and 35 control subjects without glaucoma were included in this cross-sectional study. All subjects were underwent CCT measurements using ultrasound pachymetry. Keratocyte densities of each stromal layer were determined by in vivo confocal microscopy. Student's t-test and Chi-square test were used for statistical evaluations. Correlations between keratocyte densities and CCT were analyzed using Pearson's correlation analysis.

Results:

Keratocyte densities in each stromal layer were significantly lower in glaucoma patients receiving PG analogues as compared to those of controls (P < 0.001). The mean CCT was also lower in glaucoma patients (515.2 ± 18.8 μ) than control subjects (549.6 ± 21.1 μ, P < 0.001). A positive correlation between keratocyte densities in each stromal layer and CCT was observed in POAG patients.

Conclusions:

Long-term administration of topical PG analogues may adversely influence keratocyte densities and CCT. Further prospective studies are required clarify the relationship between PG analogues and their effects on the cornea.

The effect of corneal biomechanical properties on rebound tonometer in patients with normal-tension glaucoma

PURPOSE

To evaluate the effects of corneal biomechanical properties on intraocular pressure (IOP) measured with the ICare, and to compare IOP readings obtained with ICare, Ocular Response Analyzer (ORA), and Goldmann applanation tonometry (GAT) in normal-tension glaucoma (NTG) and normal subjects.

DESIGN

Prospective, cross-sectional, comparative study.

METHODS

IOP was measured with ICare, ORA, and GAT. All subjects had corneal hysteresis (CH) and corneal resistance factor (CRF), which were measured with ORA; and central corneal thickness (CCT), axial length, spherical equivalent, and keratometry.

RESULTS

This study enrolled 97 eyes of 97 NTG patients and 89 eyes of 89 normal subjects. CCT, CH, and CRF in NTG patients were significantly lower than those in normal subjects (P = .033, P = .006, and P = .003). The difference in IOP between techniques was highly significant in NTG patients (P < .001), while there was no significant difference in IOP values between techniques in normal controls (P = .931). ICare readings were significantly lower than corneal-compensated IOP in NTG patients (P = .014). CH and CRF were significantly associated with IOP measurements with ICare in NTG and normal subjects (P < .001). The greater difference between IOPcc and ICare in NTG patients was significantly influenced by the lower CH (P < .001).

CONCLUSIONS

Since ICare is a convenient way to measure IOP, ICare is a reasonable option as an alternative tonometer in NTG patients. However, the clinician must consider that the corneal biomechanical characteristics in NTG can cause ICare to underestimate IOP.

The effect of prostaglandin analogs on the biomechanical properties and central thickness of the cornea of patients with open-angle glaucoma: a 3-year study on 108 eyes

Purpose

To evaluate the effect of prostaglandin analogs (PGAs) on the biomechanical properties (corneal hysteresis [CH], corneal resistance factor [CRF]) and central corneal thickness (CCT) of patients with open-angle glaucoma.

Methods

A total of 108 eyes were prospectively included for repeated measurements of intraocular pressure (IOP) with Goldmann applanation tonometry (GAT) and ocular response analyzer (ORA), CCT, followed by CH and CRF measurements by the ORA, during the same visit. Of these, 66 were treated with latanoprost, and 42 were treated with latanoprost and timolol. IOP, CH, CRF, and CCT were measured before treatment and at 6-month intervals.

Results

It appears that under local PGA treatment, IOP values decreased and CH and CCT significantly increased, whereas CRF did not. CCT slightly but significantly increased at all time points of the study (0.50–3.00 μm and 1.50–5.50 μm), and we observed a constant significant increase in CH (0.4–0.7 mmHg and 0.65–0.95 mmHg). Concerning the correlation of GAT IOP with CCT and CH, it was found that at the time points 0, 1, and 2 there were statistically significant correlations.

Conclusion

The changes of CCT and CH under PGA treatment in clinical practice may influence IOP measurements and patient follow-up significantly. This should be investigated further to confirm the relationship between corneal properties and treatment of open-angle glaucoma.

Novel usage of intraocular pressure-lowering drugs as wound-healing inhibitors after trabeculectomy with cell culture and animal models

Inhibiting the healing of wounds to ensure that the aqueous humor can drain into the scleral space unimpeded and form a filtering bleb plays a crucial role in determining the success rate of glaucoma surgery. The aim of this study was to investigate the novel use, with cell culture and animal models, of some commercial intraocular pressure (IOP)-lowering drugs in inhibiting the healing of fibroblast wounds. The Tenon's fibroblasts of rabbits were cultured to evaluate 13 IOP-lowering drugs for cellular proliferation, collagen formation, and migration. These were measured using [(3)H]thymidine and [(3)H]proline uptake, and Transwell chambers. A preservative of benzalkonium chloride (BAK) was initially used, with 0.02% as a maximal original concentration. All of the drugs and the BAK were diluted from original commercial concentrations to 1/10, 1/100, and 1/1000. The more inhibitive drugs screened from the cell cultures were then selected for further short-term application during and after trabeculectomy surgeries had been performed on the rabbits. Expression of the proliferative cell nuclear antigen was immunohistochemically examined 3 and 7 days after surgery. The results revealed that the inhibitive effects of BAK in cellular [(3)H]thymidine and [(3)H]proline uptake, and cellular migration were only evident at 0.002% concentrations. Based on the results of the cell cultures, timolol, latanoprost, and unoprostone exhibited a greater inhibitory effect than the other drugs. Moreover, the animal studies showed that latanoprost and unoprostone significantly suppressed the positive expression of proliferative cell nuclear antigen around the operative excision area 7 days after the trabeculectomy surgeries. The results indicate that short-term use of some IOP-lowering drugs, such as latanoprost and unoprostone, may inhibit postoperative wound healing after glaucoma surgery.

Relationship between corneal biomechanical properties, central corneal thickness, and intraocular pressure across the spectrum of glaucoma

PURPOSE

To evaluate corneal biomechanical properties across the glaucoma spectrum and study the relationship between these measurements and intraocular pressure measured by Goldmann applanation tonometry (GAT-IOP) and central corneal thickness (CCT).

DESIGN

Prospective cross-sectional study.

METHODS

SETTING

Tertiary-care teaching institute.

STUDY POPULATION

A total of 323 eyes of 323 participants (71 normal, 101 glaucoma suspect [GS], 38 ocular hypertension [OHT], 59 primary angle-closure disease [PACD], 36 primary open-angle glaucoma [POAG], and 18 normal-tension glaucoma [NTG]) who had received no ophthalmic treatment.

OBSERVATION PROCEDURES

Corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated IOP (IOPcc), and Goldmann-correlated IOP (IOPg) measured by the Ocular Response Analyzer (ORA). GAT-IOP and CCT recorded in all subjects.

MAIN OUTCOME MEASURES

Regression analysis used to determine the relationship between GAT-IOP, CCT, age, CRF, and CH. Bland-Altman plots used to assess agreement between IOP measured by GAT and the ORA (IOPg).

RESULTS

CH measurements were significantly less in POAG and NTG compared to normal subjects (P = .034 and P = .030 respectively), regardless of the IOP. The CRF was significantly less in NTG and maximum in POAG and OHT. Regression analysis with CH as dependant variable showed significant association with GAT-IOP and CRF (P < .001) but not CCT, persisting on multivariate analysis (adjusted R(2) = 0.483). GAT-IOP correlated strongly with Goldmann-correlated IOP on the ORA (IOPg) (r = 0.82; P < .001), but limits of agreement between the measurements were poor.

CONCLUSIONS

CH and CRF may constitute a pressure-independent risk factor for glaucoma. CRF appears to influence GAT-IOP measurements more than simple geometric thickness measured by CCT. However, IOP measurements from the ORA are not interchangeable with, and are unlikely to replace, Goldmann applanation tonometry at the present time.

Preservative use in topical glaucoma medications

Benzalkonium chloride (BAK) is the principal preservative employed in topical ocular hypotensive medications, although alternative compounds recently have begun to be employed or examined. Individual clinical trials have shown that exposure to BAK concentrations contained in ophthalmic solutions does not produce adverse sequelae in the majority of glaucoma patients, but concerns continue with regard to its long-term use. These concerns have resulted from an extensive research effort, including preclinical studies with in vitro and in vivo models, as well as recent clinical investigations dedicated specifically to this issue. The aim of this systematic literature review of both preclinical and clinical data was to determine the relevance of these findings to clinical practice. Most preclinical studies reported negative effects of BAK exposure, but with few exceptions, BAK concentrations and exposure times greatly exceeded those likely to be experienced by patients, given the normal physiological dilution by the tear film. In addition, consistent evidence of BAK-related toxicity did not emerge from our review of dedicated clinical investigations. Thus, taken together, current evidence supports the safety of BAK for most glaucoma patients, although subpopulations with abnormal tearing may benefit from alternative preservative compounds or preservative-free formulations. Further studies to identify these populations are needed.

The effect of prostaglandin analogues on central corneal thickness of patients with chronic open-angle glaucoma: a 2-year study on 129 eyes

PURPOSE

To evaluate the effect of prostaglandin analogues on the central corneal thickness (CCT) of patients with chronic open-angle glaucoma (COAG).

METHODS

One hundred and twenty-nine eyes were included in this study. Of these, 108 were treated with prostaglandin analogues (latanoprost, travoprost and bimatoprost), while 21 eyes treated with β-blockers were used as controls. CCT was measured before treatment and at 3-month intervals.

RESULTS

A slight but significant increase in CCT was recorded in the bimatoprost and latanoprost groups. Treatment with bimatoprost produced a constant increase (1.85-8.83 μm) in CCT at all time-points of the study. The CCT rise found in the latanoprost group was significant for the first year. Treatment with travoprost did not affect CCT.

CONCLUSION

The possibility of corneal thickening under prolonged, local prostaglandin treatment should be investigated further. However, in clinical practice, CCT changes may sometimes influence intraocular pressure measurements significantly.