Evaluation of Prostaglandin Analogue Effects on Corneal Keratocyte Density Using Scanning Laser Confocal Microscopy

Corneal Confocal and Specular Microscopic Characteristics in Primary Open-Angle Glaucoma: An Optical Coherence Tomography (OCT)-Based Case-Control Study

BACKGROUND

Glaucoma, particularly open-angle glaucoma (OAG), is a leading cause of irreversible blindness, associated with optic nerve damage, retinal ganglion cell death, and visual field defects. Corneal biomechanical properties and cellular components, such as corneal nerve and keratocyte densities assessed by in vivo confocal microscopy (IVCM), may serve as biomarkers for glaucoma progression. This study aimed to explore the relationship between corneal nerve parameters, keratocyte density, and optical coherence tomography (OCT)-derived retinal nerve fiber layer (RNFL) thickness in primary open-angle glaucoma (POAG) patients and controls.

METHODS

This case-control study was conducted at Al-Shifa Trust Eye Hospital, Rawalpindi, Pakistan, from January 2023 to October 2024. It included 26 eyes of 17 glaucoma patients and 28 eyes of 18 age-matched controls. POAG was diagnosed based on elevated intraocular pressure (IOP), optic disc changes, RNFL defects, and visual field abnormalities. Participants underwent full ophthalmic evaluation, including OCT for RNFL thickness, specular microscopy, and corneal confocal microscopy (CCM). Data were analyzed using IBM SPSS Statistics for Windows, Version 26.0 (Released 2019; IBM Corp., Armonk, New York, United States), with Spearman's correlation and linear regression for association analysis.

RESULTS

Anterior stromal keratocyte density was significantly lower in glaucoma patients (436.63±145.44 cells/mm²) compared to controls (546.54±141.20 cells/mm²; p=0.007). No significant difference was found in posterior stromal keratocyte density (p=0.788). Corneal nerve parameters showed a higher nerve fiber length in glaucoma patients (19.25±5.74 mm/mm²), but the difference was not significant (p=0.143). Nerve branch density was significantly higher in glaucoma patients (40.22±23.44 branches/mm²) compared to controls (26.12±10.17 branches/mm²; p=0.054). Specular microscopy revealed significantly lower endothelial cell density in glaucoma patients (2159.8±393.39 cells/mm²) compared to controls (2474.15±272.59 cells/mm²; p=0.002). OCT measurements showed a significantly thinner global RNFL in glaucoma patients (69.79±24.79 µm) compared to controls (98.86±9.04 µm; p<0.001). Spearman's correlation analysis showed that anterior keratocyte density was positively correlated with global (r=0.294; p=0.045), superior (r=0.312; p=0.031), and inferior quadrant RNFL thickness (r=0.285; p=0.049). It was also negatively correlated with central corneal thickness (CCT) (r=-0.367; p=0.039). In multivariate analysis, the duration of glaucoma was significantly associated with RNFL thickness (p=0.011).

CONCLUSION

This study found that anterior stromal keratocyte density was positively correlated with RNFL thickness, suggesting a potential link between corneal cellular changes and glaucoma severity. Endothelial cell density was significantly lower in glaucoma patients, which may reflect the disease's impact or the effect of medications on corneal health. While corneal nerve parameters did not show significant differences, these findings highlight the importance of corneal biomechanical properties in glaucoma pathophysiology. Further studies with larger sample sizes and longer follow-up periods are needed to confirm these findings and explore the role of corneal parameters in glaucoma progression.

Comparing corneal biomechanic changes among solo cataract surgery, microhook ab interno trabeculotomy and iStent implantation

Minimally invasive glaucoma surgery has expanded the surgical treatment options in glaucoma, particularly when combined with cataract surgery. It is clinically relevant to understand the associated postoperative changes in biomechanical properties because they are influential on the measurement of intraocular pressure (IOP) and play an important role in the pathogenesis of open-angle glaucoma (OAG). This retrospective case-control study included OAG patients who underwent cataract surgery combined with microhook ab interno trabeculotomy (µLOT group: 53 eyes of 36 patients) or iStent implantation (iStent group: 59 eyes of 37 patients) and 62 eyes of 42 solo cataract patients without glaucoma as a control group. Changes in ten biomechanical parameters measured with the Ocular Response Analyzer and Corneal Visualization Scheimpflug Technology (Corvis ST) at 3 and 6 months postoperatively relative to baseline were compared among the 3 groups. In all the groups, IOP significantly decreased postoperatively. In the µLOT and control groups, significant changes in Corvis ST-related parameters, including stiffness parameter A1 and stress‒strain index, indicated that the cornea became softer postoperatively. In contrast, these parameters were unchanged in the iStent group. Apart from IOP reduction, the results show variations in corneal biomechanical changes from minimally invasive glaucoma surgery combined with cataract surgery.

Comparison of Goldmann and ORA tonometers in newly diagnosed, untreated, POAG and OHT eyes

BACKGROUND AND OBJECTIVE

The corneal biomechanical properties in naïve, untreated glaucoma and ocular hypertension (OHT) eyes is interesting, because it may be a source of error in intraocular pressure (IOP) measurements by Goldmann applanation tonometer (GAT) and Ocular Response Analyzer (ORA) The main objective of this study was to evaluate the IOP values obtained using GAT and the ORA, in primary open angle glaucoma (POAG) and in OHT untreated eyes.

MATERIAL AND METHODS

Observational, masked, cross sectional observational study. Newly diagnosed, untreated POAG and OHT eyes were included.

RESULTS

51 POAG and 34 OHT eyes were analyzed. We found that IOPcc (IOP corneal-compensated) was significantly higher than GAT IOP in POAG (p = 0.0002) while we did not find any significant difference between both tonometers in OHT (p = 0.1).

CONCLUSIONS

GAT seems to underestimate the real IOP in untreated POAG eyes and it seems to be quite accurate in OHT eyes.

Correlations among Corneal Biomechanical Parameters, Stiffness, and Thickness Measured Using Corvis ST and Pentacam in Patients with Ocular Hypertension

Background

To preliminary explore the correlations among corneal biomechanical parameters, stiffness, and thickness in patients with ocular hypertension (OHT) before and after treatment with topical antiglaucoma medications.

Methods

This was a retrospective study that included 35 eyes with newly diagnosed OHT. Axial length (AL), apical corneal thickness, and minimum corneal thickness were measured using Pentacam. The lengths, velocities, and times of the first and second corneal applanations (A1L, A1V, A1T, A2L, A2V, and A2T, respectively); the highest concavity radius; highest concavity peak distance (PDHC); highest concavity deformation amplitude (DAHC); highest concavity time (HCT); pachymetry (PACH); stress-strain index (SSI); stiffness parameter-A1 (SP-A1); deformation amplitude ratio (DA ratio); integrated radius (IR); Ambrosio's relational thickness horizontal (ARTh); corneal biomechanical index; noncorrected intraocular pressure (IOPnct); and biomechanically corrected IOP (bIOP) values were measured using the corneal visualization Scheimpflug technology (Corvis ST/CST).

Results

After 5 weeks of treatment, Goldman applanation tonometer-IOP, IOPnct, bIOP, PACH, A1T, A2V, SSI, SP-A1, and ARTh decreased, but A1V, A2T, PDHC, DAHC, DA ratio, and IR increased significantly (all p < 0.05). SP-A1 and A1T were positively associated with premedication IOP and IOP changes, whereas A1V, A2T, PDHC, and IR were negatively associated (all p < 0.05). DAHC and DA ratio had significantly negative correlations with IOP variations. PDHC was found to be positively correlated with AL (p < 0.05). A positive relationship was noted between SP-A1 and HCT before medication (p < 0.05).

Conclusions

SP-A1 was significantly and consistently associated with IOP. HCT might be correlated with SP-A1. SP-A1 and CST parameters could serve as potential biomarkers for evaluating OHT treatment efficacy.

Differential impact of prostaglandin analogues on agreement of intraocular pressure measurements obtained by Goldmann applanation, rebound, and noncontact tonometry

Background

To evaluate the effect of topical prostaglandin analogues on agreement of IOP measurements obtained by Goldmann applanation tonometry (GAT), rebound tonometry (RBT), and noncontact tonometry (NCT) in eyes with primary open- angle glaucoma (POAG).

Methods

Intraocular pressure measurements were obtained using GAT, RBT, and NCT in patients with POAG with or without prostaglandin analogues. The agreement between each tonometry was analysed using Bland-Altman analyses in those with or without prostaglandin analogues. The effect of average IOP on IOP differences was also evaluated.

Results

Among a total of 86 subjects included in the study, 44 patients were using prostaglandin analogues. The difference in IOP measured by GAT and RBT was marginally greater in those with (GAT-RBT: − 0.94 ± 1.63 mmHg) prostaglandin analogues than in those without (− 0.33 ± 1.22 mmHg, P = 0.06). The difference in IOP measured by GAT and NCT was significantly greater in the prostaglandin group (GAT-NCT: 2.40 ± 2.89 mmHg) than in the group without prostaglandin analogues (0.41 ± 1.63 mmHg, P < 0.01). While there was no significant relationship between the average of all tonometries and the difference between tonometries in those without prostaglandin analogues, both RBT and NCT underestimated IOP relative to GAT at higher IOP in those using prostaglandin analogues.

Conclusion

Intraocular pressure measured by RBT and NCT was similar to that measured by GAT in those without prostaglandin analogues. RBT overestimated and NCT underestimated IOP compared to GAT in those using prostaglandin analogues.

The effect of topical bimatoprost on corneal clarity in primary open-angle glaucoma: a longitudinal prospective assessment

PURPOSE

To study the effect of topical bimatoprost on the corneal optical density values using a dual Scheimpflug Placido analysis system.

METHODS

This longitudinal case-control study included 18 patients with newly diagnosed primary open-angle glaucoma who received topical bimatoprost as a first-line treatment and 20 healthy individuals (age and sex-matched controls). Corneal densitometry data were obtained using the dual Scheimpflug analyzer at pre-treatment and 1st, 6th, 12th, 18th months of post-treatment. Repeated measures of ANOVA and Pearson correlation tests were used for statistical analysis.

RESULTS

There were statistically significant differences between pre-treatment and post-treatment 1st and 6th months corneal densitometry values (p < 0.001, p = 0.007, respectively). However, there was no statistically significant difference between the post-treatment 12th and 18th months (p > 0.05). Corneal densitometry values decreased during the 1st month. Intraocular pressure (IOP) differences were statistically significant between baseline and 1 month after treatment (P < 0.001), however not statistically significant between the 1st and 6th, 6th and 12th, 12th and 18th months after treatment (p > 0.05, for all). Corneal densitometry was not correlated with IOP (r = - 0.037, p = 0.44). In the control group, there was no statistically significant difference between baseline and post-baseline 18th-month corneal densitometry measurements (p > 0.05).

CONCLUSIONS

Topical bimatoprost administration might result in a decrease in corneal densitometry measurement. It is of clinical importance that topical bimatoprost administration can affect corneal transparency and cause a possible alteration in corneal properties.

Confocal Microscopy and Anterior Segment Optical Coherence Tomography Imaging of the Ocular Surface and Bleb Morphology in Medically and Surgically Treated Glaucoma Patients: A Review

Glaucoma patients often suffer from ocular surface disease (OSD) caused by the chronic administration of topical anti-glaucoma medications, especially in cases of long-term therapy with preserved or multiple drugs. Additionally, glaucoma surgery may determine ocular surface changes related to the formation and location of the filtering bleb, the application of anti-mitotic agents, and the post-operative wound-healing processes within the conjunctiva. Recently, several studies have evaluated the role of advanced diagnostic imaging technologies such as in vivo confocal microscopy (IVCM) and anterior segment-optical coherence tomography (AS-OCT) in detecting microscopic and macroscopic features of glaucoma therapy-related OSD. Their clinical applications are still being explored, with recent particular attention paid to analyzing the effects of new drug formulations and of minimally invasive surgical procedures on the ocular surface status. In this review, we summarize the current knowledge about the main changes of the ocular surface identified at IVCM and AS-OCT in glaucoma patients under medical therapy, or after surgical treatment.

Effect of Prostaglandin Analogues on Central Corneal Thickness: 3-Year Follow-up Results

PURPOSE

To evaluate the effects of each subgroup of prostaglandin analogues (PGAs) on central corneal thickness (CCT) in patients with normal tension glaucoma (NTG).

METHODS

We retrospectively reviewed 55 eyes of 55 patients with NTG who were receiving PGA therapy. Patients who were treated with 0.005% latanoprost (16 eyes), 0.0015% tafluprost (16 eyes), or 0.004% travoprost (23 eyes) monotherapy were included. CCT assessments were performed at baseline and 1, 2, and 3 years after initiation of treatment.

RESULTS

In the NTG group, the mean CCT showed a decreasing trend, and there was a significant difference in mean CCT at 1, 2, and 3 years compared with baseline (baseline, 538.16 ± 32.14; 1 year, 526.55 ± 37.30 µm [p = 0.00]; 2 years, 521.67 ± 36.79 µm [p = 0.00]; 3 years, 520.43 ± 36.88 µm [p = 0.00]). The reduction of CCT was confirmed by subgroup analysis. In the 0.005% latanoprost group, mean CCT was decreased at 1 year (p = 0.11), 2 years (p = 0.00), and 3 years (p = 0.02). In the 0.0015% tafluprost group and the 0.004% travoprost group, mean CCT was also significantly decreased at all years (p = 0.00). No statistical difference was observed between the NTG subgroups (p = 0.06).

CONCLUSIONS

Topical therapy with PGAs appeared to cause a significant decrease in CCT reduction in patients with NTG. A long-term follow-up study including more participants is needed.

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.

Using the entropy of the corneal pulse signal to distinguish healthy eyes from eyes affected by primary open-angle glaucoma

OBJECTIVE

The purpose of this study was to evaluate whether the complexity of the corneal pulse (CP) signal can be used to differentiate patients with primary open-angle glaucoma (POAG) from healthy subjects.

APPROACH

The study sample consisted of 28 patients with POAG and a control, age-matched group of 30 subjects. After standard ophthalmic examination, the CP signal from a randomly selected eye of each participant was measured using non-contact ultrasonic micro-displacement measurement technology. After pre-processing, the complexity of the CP signal was estimated using refined composite multiscale fuzzy entropy (RCMFE) up to scale factor 50. The average RCMFE values were computed from three repeated measurements of the CP signals for each participant and each scale factor.

MAIN RESULTS

The complexity of the CP signal in glaucomatous eyes was higher than that observed in healthy ones. Also, RCMFE of the CP signal was found to differentiate (statistically significantly) between the two groups for scales in the range from 26 to 43. For these scales, the one for which the lowest p-value (t-test, p = 0.017) was obtained when comparing RCMFE between the two groups was selected as the optimal scale. Next, a receiver operating characteristic analysis for the optimal scale showed that the proposed approach of calculating the multiscale entropy of the CP signal has some potential to discriminate between patients with POAG and healthy controls (sensitivity, specificity and accuracy of 0.643, 0.700 and 0.672, respectively).

SIGNIFICANCE

In conclusion, RCMFE, as a complexity measure, may be considered an auxiliary indicator to support glaucoma diagnostics.

Keratocyte biology

The study of corneal stromal keratocytes is motivated by its strong association with corneal health and visual function. They play a dominant role in the maintenance of corneal homeostasis and transparency through the production of collagens, proteoglycans and corneal crystallins. Trauma-induced apoptosis of keratocytes and replacement by fibroblasts and myofibroblasts disrupt the stromal matrix organization, resulting in corneal haze formation and vision loss. It is, therefore, important to understand the biology and behaviours of keratocytes and the associated stromal cell types (like fibroblasts, myofibroblasts, stromal stem cells) in wound healing, corneal pathologies (including keratoconus, keratitis, endothelial disorders) as well as different ophthalmic situations (such as collagen crosslinking/photodynamic treatment, keratoplasty and refractive surgery, and topical medications). The recent development of ex vivo propagation of keratocytes and stromal stem cells, and their translational applications, either via stromal injection or incorporated in bioscaffold, have been shown to restore the corneal transparency and regenerate native stromal tissue in animal models of corneal haze and other disorders.

Latanoprost treatment differentially affects intraocular pressure readings obtained with three different tonometers

PURPOSE

To evaluate the apparent intraocular pressure (IOP) change observed after treatment with latanoprost in naive eyes of patients with primary open-angle glaucoma (POAG) or ocular hypertension (OHT) using Goldmann applanation tonometer (GAT), ocular response analyzer (ORA) and Corvis ST tonometry.

METHODS

Prospective observational cohort study. One eye from each of 59 newly diagnosed patients with POAG or OHT in our institution was analysed. IOP readings obtained using GAT, ORA and Corvis at baseline and after a 3-month period of treatment with latanoprost were compared. Additionally, pre- and post-treatment biomechanical corneal parameters provided by the Corvis tonometer were analysed.

RESULTS

There was no statistically significant difference between the apparent treatment-induced IOP reductions when GAT and ORA were compared (p > 0.05). In contrast, the treatment-induced IOP reduction recorded using the Corvis tonometer was significantly smaller compared to the apparent IOP reduction observed with GAT and ORA (p = 0.0001 for both comparisons). With respect to biomechanical corneal properties, statistically significant changes were found after 3 months of treatment with latanoprost for the first corneal applanation time (AT1) (p = 0.001), second corneal applanation time (AT2) (p = 0.001) and deformation amplitude (DA) (p = 0.0003).

CONCLUSION

Following a 3-month course of latanoprost, the apparent treatment-induced IOP reduction in previously naïve patients with POAG or OHT differed depending on the tonometer used. Certain corneal biomechanical parameters assessed using Corvis ST exhibited a significant change. The ocular hypotensive effect of prostaglandin analogues may be overestimated when chronically treated patients are measured using GAT or ORA.

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.

In Vivo Analysis of Prostaglandins-induced Ocular Surface and Periocular Adnexa Modifications in Patients with Glaucoma

BACKGROUND/AIM

Prostaglandin analogues (PGAs) are a first-line medical treatment for glaucoma because of their powerful intraocular pressure (IOP) lowering effect, few systemic side-effects (SEs), and the once daily administration. Despite the high systemic safety profile, the chronic use of PGAs may induce periocular and ocular surface (OS)-related side effects, which affect a significant proportion of glaucomatous patients. In this review, we summarize the current knowledge about SEs of PGAs on periocular structures and OS, and their implications in clinical practice.

MATERIALS AND METHODS

A comprehensive literature search on the PubMed platform was performed. Two hundred fifty articles fulfilling key words were identified, of which 180 were excluded since they did not concern the effects of PGAs on the periocular tissues and OS, or because of their limited relevance. The following key words were used and combined, to narrow-down the literature: "prostaglandin" and "ocular surface," which identified 184 unique publications, of which 68 were selected; "prostaglandin" and "periocular" which identified 46 unique publications, of which 11 were selected. An additional search was conducted using "prostaglandin" and "Meibomian glands (MGs)", which identified twenty unique publications, of which 8 were selected. Thus, a total of 70 articles were chosen based on their relevance and were included in this review.

RESULTS

Prostaglandin-associated peri-orbitopathy, skin pigmentation and hypertrichosis, eyelash growth, and MGs dysfunction are the most frequent modifications of periocular tissues. They are induced by the tissue accumulation of PGAs, and FP receptor stimulation. Without preservatives, PGAs act as stimulators of conjunctival goblet cells, which are the main source of ocular surface mucoproteins, and seem to increase conjunctival epithelium microcysts proposed as in vivo hallmark of the trans-scleral aqueous humour outflow. Additional PGA-induced modifications can be recognized in the cornea, corneo-scleral limbus, conjunctival stroma and, conjunctiva-associated lymphoid tissue, mainly appearing as inflammatory changes. OS epithelia desquamation, chemosis, apoptosis, dendritic cell activation, conjunctival or episcleral vasodilation, and sub-basal nerve plexus disruption were also described in patients receiving preserved PGAs.

CONCLUSION

PGAs induce several modifications of the OS structures and adnexa; nonetheless, none of them significantly reduces the local safety profile of this class of drugs. Moreover, the OS changes do not affect the IOP lowering efficacy of PGAs. On these bases, local SEs of PGAs should not discourage clinicians in using this class of medications because of their efficacy, the systemic safety profile, and the better adherence.

Long term safety and tolerability of Tafluprost 0.0015% vs Timolol 0.1% preservative-free in ocular hypertensive and in primary open-angle glaucoma patients: a cross sectional study

BACKGROUND

The effects of preservatives of antiglaucoma medications on corneal surface and tear function have been widely shown in literature; it's not the same as regards the active compounds themselves. The purpose of our study was to compare Ocular Surface Disease (OSD) signs and symptoms of Tafluprost 0.0015% versus preservative free (PF) Timolol 0.1% eyedrops in ocular hypertensive (OH) and in primary open-angle glaucoma (POAG) patients.

METHODS

A cross-sectional study included patients in monotherapy for at least 36 months with Tafluprost 0.0015% (27) or PF Timolol 0.1% (24) and 20 healthy age and sex-matched volunteers. All subjects underwent clinical tests (Schirmer I and break-up time), in vivo confocal microscopy (IVCM) and were surveyed using Ocular Surface Disease Index (OSDI) and Glaucoma Symptoms Scale (GSS) questionnaires. The groups were compared with ANOVA, Kruskal-Wallis test, t-test, Mann-Whitney test and Bonferroni's adjustment of p-values.

RESULTS

No significant differences were found in questionnaires scores, clinical tests, IVCM variables between therapy groups. Tafluprost 0.0015% group showed significantly higher OSDI score, basal epithelial cells density, stromal reflectivity, sub-basal nerves tortuosity (p = 0.0000, 0.037, 0.006, 0.0000) and less GSS score, number of sub-basal nerves (p = 0.0000, 0.037) than controls but similar clinical tests results (p > 0.05). PF Timolol group had significantly higher OSDI score, basal epithelial cells density, stromal reflectivity and sub-basal nerve tortuosity (p = 0.000, 0.014, 0.008, 0.002), less GSS score, BUT and number of sub-basal nerves (p = 0.0000, 0.026, 0.003) than controls.

CONCLUSIONS

Compared to PF Timolol 0.1%, Tafluprost 0.0015% showed similar safety with regards to tear function and corneal status and a similar tolerability profile. Both therapy groups show some alterations in corneal microstructure but no side effects on tear function except for an increased tear instability in PF Timolol 0.1% group. Ophtalmologists should be aware that even PF formulations may lead to a mild ocular surface impairment.

Changes in Corneal Biomechanical Properties after Long-Term Topical Prostaglandin Therapy

OBJECTIVE

To compare corneal biomechanical properties, measured by a newly developed tonometer (Corneal Visualization Scheimpflug Technology, Corvis ST), in untreated primary open angle glaucoma (POAG) patients, POAG patients with long-term topical prostaglandin analog (PGA) therapy and in normal controls. Further is to investigate the potential effects of PGA on corneal biomechanics.

METHODS

In this case-control study, 35 consecutive medication naïve eyes with POAG, 34 POAG eyes with at least 2 years treatment by PGA and 19 normal eyes were included. Intraocular pressure (IOP), central corneal thickness (CCT) and corneal biomechanical parameters, including deformation amplitude (DA), applanation time (AT1 and AT2), applanation length (AL1 and AL2), applanation velocity (AV1 and AV2), and peak distance and radius were measured using Corvis ST. Axial length and corneal curvature were measured with partial coherence interferometry (IOLMaster, Zeiss, Germany). General linear model analysis was performed to investigate the corneal biomechanical property changes among the normal controls, newly diagnosed POAG patients and POAG patients with long-term PGA treatment, and among the subgroups of different types of PGA treatment, including bimatoprost, latanoprost and travoprost. Furthermore, pairwise comparisons using Bonferroni correction for least squares means were employed.

RESULTS

AT1 (p<0.0001), AV1 (p<0.0001), AT2 (p = 0.0001), AV2 (p<0.0001) and DA (p = 0.0004) in newly diagnosed glaucoma patients were significantly different from those in normal subjects and in patients underwent at least 2 years topical PGA therapy after adjusting for age and gender. After adjusting for age, gender, IOP, CCT, axial length and corneal curvature, a significant difference was detected for DA between glaucoma patients without PGA treatment and patients with long-term PGA therapy (p = 0.0387). Furthermore, there were no statistical significant differences in all of the corneal biomechanical parameters among the 3 types of PGA therapy subgroups, namely bimatoprost, latanoprost and travoprost.

CONCLUSIONS

Significant changes in corneal deformation parameters were found among untreated POAG patients, POAG patients with long-term topical PGA therapy and normal controls. Long-term topical PGA treatment might have a direct effect on corneal biomechanical properties in addition to the indirect effect owing to the PGA-induced IOP reduction and CCT decrease on corneal dynamic properties.

Effect of topical prostaglandin analogues on corneal hysteresis

PURPOSE

To evaluate possible changes in corneal hysteresis (CH) after topical treatment with a prostaglandin analogue in medication-naïve eyes.

METHODS

This was a prospective, observational cohort study. Sixty-eight eyes of 68 patients were prospectively included who were newly diagnosed with primary open-angle glaucoma or ocular hypertension in our institution. All patients were treatment-naïve. Patients were evaluated at baseline and after 6 months of treatment with latanoprost in the eye with the lower intraocular pressure (IOP) measured by Goldmann applanation tonometry (GAT). The ocular response analyzer was used to measure CH.

RESULTS

CH increased significantly (p = 0.0001) from 8.96 ± 2.3 mmHg to 9.79 ± 1.97 mmHg, and this increase was correlated significantly (p = 0.0001, r = 0.64, r(2) = 0.41) with the basal CH. We identified a weak but significant (r(2) = 0.06, p = 0.01) relationship between the basal CH and the drug-induced reduction of the GAT IOP. Nevertheless, the increase in the drug-induced CH was not correlated with the decrease in the GAT IOP.

CONCLUSION

Treatment with latanoprost increases CH. The CH increase was not correlated with the drug-induced decrease in the GAT IOP, which suggested a direct effect of latanoprost on the viscoelastic corneal properties.

A 1-year randomized study of the clinical and confocal effects of tafluprost and latanoprost in newly diagnosed glaucoma patients

Introduction

The aim of the present study was to compare the confocal and clinical features of newly diagnosed glaucoma patients receiving unpreserved prostaglandins (tafluprost) versus preserved prostaglandins (latanoprost).

Materials and Methods

40 patients were randomized to tafluprost 0.0015% (20 patients; 32 eyes) or latanoprost 0.005% + benzalkonium chloride 0.02% (20 patients; 35 eyes) once daily for 1 year. Inclusion criteria were new glaucoma diagnosis, and no ocular treatments for 6 months before the study. Patients were evaluated at baseline and every 3 months with a complete ophthalmologic evaluation, Schirmer’s test, break-up time test, confocal microscopy of the central cornea, and measurement of intraocular pressure (IOP). Investigators were masked to treatment. Both eyes were analyzed if they fulfilled inclusion criteria. Treatments and changes between follow-up and baseline were compared by analysis of variance (ANOVA), t test and Chi-square test.

Results

At baseline, the two groups had similar age, ocular surface and confocal findings; keratocyte activation was present in 40%, branching pattern in 85%, and beading in 75%, with no inter-group differences. At follow-up, no significant clinical changes were detected, apart from a drop of IOP by 3.6–4.2 mmHg in the two groups (p < 0.001, with no difference between treatments). Despite inter-treatment ANOVA for confocal microscopy being negative, subtle changes were present. During follow-up, all eyes without nerve branching pattern at baseline progressively developed it when treated with latanoprost, whereas no change occurred using tafluprost treatment (p = 0.05). None of the eyes without beading at baseline developed it at the end of the study in the tafluprost group, whereas beading did occur in 75% of patients treated with latanoprost (p = 0.05). Both treatments were associated with increased keratocyte activation at follow-up; the change from baseline was statistically significant after month 3 with latanoprost (p = 0.02) and after month 6 with tafluprost (p = 0.04).

Conclusions

The two study treatments had similar clinical effects, but tafluprost had a more favorable profile for some confocal parameters of the cornea.

Funding

Merck Sharp & Dohme International.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-015-0205-5) contains supplementary material, which is available to authorized users.

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.

In vivo laser scanning confocal microscopy of the ocular surface in glaucoma

Over the past decade, knowledge about the ocular surface in glaucoma has significantly increased through the use of in vivo laser scanning confocal microscopy (LSCM). This in vivo imaging method can show modifications at the cellular level induced by anti-glaucoma drugs on ocular surface structures and adnexa in the eye. High-quality images of the conjunctiva, cornea, limbus, meibomian glands, and lymphoid structures during therapy can be obtained. In addition, LSCM opened new fields of research on the patho-physiology of aqueous humor (AH) hydrodynamics in untreated, and in medically or surgically treated glaucomatous patients. In these conditions, an enhancement of the trans-scleral AH outflow contributed to clarification of the mechanism of action of different anti-glaucoma medications and surgical approaches. Finally, the use of LSCM represented a huge advance in evaluation of bleb functionality after filtration surgery, defining the hallmarks of AH filtration through the bleb-wall and distinguishing functional from nonfunctional blebs. Thus, signs seen with LSCM may anticipate clinical failure, guiding the clinician in planning the appropriate timing of the various steps in bleb management. In this review we summarize the current knowledge about in vivo LSCM of the ocular surface in glaucoma.

In vivo confocal microscopy of conjunctiva in preservative-free timolol 0.1% gel formulation therapy for glaucoma

PURPOSE

To evaluate the effects at 1 year of preservative-free timolol gel and preserved timolol eye drops on conjunctiva and tear parameters.

METHODS

Forty patients with primary open-angle glaucoma or ocular hypertension were randomized to the two treatment groups and compared with 20 healthy age-matched controls. Clinical tests (IOP, Schirmer I test, and lacrimal film break-up time BUT) and in vivo conjunctival confocal microscopy (IVCM) were performed in all patients at baseline and after 12 months. IVCM (HRT II Rostock Cornea Module; Heidelberg Engineering GmbH, Heidelberg, Germany) was performed after topical anaesthesia in the four cardinal locations and at the corresponding limbus to analyse conjunctiva cells. The main IVCM outcomes were goblet cell density and epithelial regularity.

RESULTS

IVCM and clinical parameters were similar in the three groups at baseline. After 12 months, intra-epithelial goblet cell density was significantly lower in the preserved (48.25 ± 7.70) than in the preservative-free beta-blocker group (86.83 ± 22.17, p < 0.001) and controls (88.9 ± 18.33, p < 0.001). The epithelial layer was significantly more regular in the preserved beta-blocker medication group than in the preservative-free beta-blocker group (p < 0.001) and the control group (p < 0.001). A significant reduction in both Schirmer I and BUT was found in the group of preserved timolol (respectively, 11.3 ± 2.97 and 8.12 ± 0.99) compared with preservative-free timolol (16.8 ± 1.83 and 11.27 ± 1.27, p < 0.001) and controls (17.8 ± 1.87 and 12.10 ± 1.28, p < 0.001).

CONCLUSIONS

Based on our IVCM data, preservative-free beta-blocker gel induces less changes at ocular surface than preserved beta-blockers, a fact that should be considered to obtain less adverse effects and maximal adherence to treatment in a chronic condition such as glaucoma.

Biomechanical profile of the cornea in primary congenital glaucoma

PURPOSE

The aim of our study was to investigate the biomechanical properties of the cornea in primary congenital glaucoma (PCG) and to identify the potential ocular determinants, which affect the corneal biomechanical metrics.

METHODS

Corneal hysteresis (CH), corneal resistance factor (CRF) and central corneal thickness (CCT) were measured in 26 patients with PCG (40 eyes) with the aid of ocular response analyser. In vivo laser-scanning confocal microscopy was used for the estimation of stromal keratocyte density (KD) and the evaluation of corneal endothelium. Twenty normal subjects (40 eyes) served as controls. Student's t-test and Pearson's correlation coefficients were used for statistical analysis. p Values <0.05 were considered statistically significant.

RESULTS

Corneal hysteresis, CRF and CCT were significantly reduced in patients with PCG (all p < 0.05). Corneal hysteresis and CRF negatively correlated with the corneal diameter in both groups (r(1) = -0.53, r(2) = -0.66, p < 0.001 for CH and r(1) = -0.61, r(2) = -0.69, p < 0.001 for CRF). Moreover, we identified a significant correlation between CH and CRF with CCT in both groups (r(1) = 0.51, r(2) = 0.48, p < 0.001 for CH and r(1)  = 0.45, r(2) = 0.44, p < 0.001 for CRF). Mean KD was significantly reduced both in the anterior and posterior corneal stroma in patients with PCG (764 ± 162 and 362 ± 112 cells/mm(2) , respectively) compared with controls (979 ± 208 and 581 ± 131 cells/mm(2) , respectively) (p < 0.001). There was no significant correlation between the keratocyte density in anterior and/or posterior stroma and CH or CRF in any group (r(1) = 0.29, r(2) = 0.31, p < 0.06). Mean endothelial cell density was also significantly reduced in PCG group (2920 ± 443 cells/mm(2) ) compared with control group (3421 ± 360 cells/mm(2) ) (p < 0.001). Pleomorphism and polymegalism were significantly increased in corneal endothelium of patients with PCG.

CONCLUSIONS

  Our results showed a significant reduction in CH and CRF in PCG. Both CH and CRF were negatively correlated with corneal diameter. A significant correlation of CH and CRF with CCT was identified in both groups. Keratocyte density was decreased in PCG, but did not have a significant impact on CH and CRF. Mean endothelial density was also decreased in PCG. Our results suggest that reduced CCT and increased corneal diameter are major ocular determinants for the modified corneal biomechanical profile in PCG, while cellular alterations in corneal stroma and endothelium have no significant biomechanical impact.

Effect of latanoprost on central corneal thickness in unilateral normal-tension glaucoma

PURPOSE

To evaluate the effect of latanoprost on central corneal thickness (CCT) in patients with unilateral normal-tension glaucoma (NTG).

METHODS

A total of 38 patients, with unilateral NTG, who were being treated in our glaucoma clinic and were receiving 0.005% latanoprost monotherapy over 24 months, were included in this study. The data were collected, retrospectively, with reviewing of the charts. The mean CCT and the CCT reduction from the baseline were assessed before the treatment, and at 3, 6, 9, 12, and 24 months after the initiation of the treatment. An unaffected eye was also evaluated for the control group. All the measurements were performed with a commercially available ultrasound pachymeter.

RESULTS

There were no significant differences between the eyes for the baseline intraocular pressure and CCT. The mean CCT trend decreased, except at 9 months after the treatment in the latanoprost group (affected eye), but only statistically significant after 24 months of treatment by using paired-sample t-test [544.6±38.4 vs. 540.3±37.8 μm (P=0.013)]. There was no statistically significant changes of CCT between the groups with repeated measures analysis of variance (P=0.635).

CONCLUSION

Topical therapy with latanoprost may decrease the CCT, over a period of 24 months, in patients with NTG. These data should be taken into consideration in a long-standing latanoprost treatment of NTG.

Effect of acute increases of intraocular pressure on corneal pachymetry in eyes treated with travoprost: an animal study

PURPOSE

To evaluate "in vivo" the effect of topical travoprost on the central corneal thickness (CCT) of rabbit eyes, and the changes in the CCT after acute increases of intraocular pressure (IOP) in these eyes.

MATERIALS AND METHODS

This is an interventional, prospective, case-control, masked study. Topical travoprost was applied once daily for one month to the right eye of six New Zealand male rabbits, the left eye of each animal served as control. The baseline CCT and IOP were measured under general anesthesia. After the IOP was stabilized at 15 and 30 mmHg, as registered by direct cannulation of the anterior chamber, CCT measurements were measured again at both pressure levels.

RESULTS

The baseline CCT was thicker in eyes previously treated with travoprost (study group) than in control eyes (p < 0.01). The CCT decreased in both groups when IOP was raised to 15 and 30 mmHg, and there were no statistically significant difference in absolute CCT values between study and control eyes at any of the IOP levels (p = 0.5). However, the amount of CCT decrease from baseline values was greater in eyes previously treated with travoprost (study group) than in control ones, at both 15 and 30 mmHg IOP levels (p = 0.01 and 0.02, respectively).

CONCLUSIONS

Rabbit corneas treated with topical travoprost show a different strain response to acute increases in IOP than control eyes.