Effect of prostaglandin analogues on the biomechanical corneal properties in patients with open-angle glaucoma and ocular hypertension measured with dynamic scheimpflug analyzer.

PURPOSE: The aim of the study is to evaluate the effect of topical prostaglandin (PG) treatment on the corneal biomechanical properties in treatment-naïve patients with either primary open-angle glaucoma (POAG) or ocular hypertension (OHT) using the Corvis ST device. METHODS: This is an observational study. We analyzed the Corvis ST dynamic corneal response parameters of our database using the newest software available. Thirty-four eyes of 34 patients were included. They were all newly diagnosed and treatment-naïve. Patients were evaluated at baseline and after 6 months of treatment with prostaglandin analogues. Ultrasound pachymetry, Optical Coherence Tomography (OCT) and a 24-2 visual field test were performed in baseline visit. Goldman Applanation Tonometry (GAT-IOP) and Corvis ST dynamic corneal response parameters were registered at baseline and at the 6-month visit. RESULTS: After 6 months of treatment, the IOP decrease (Δ) values obtained with the different tonometers were ΔGAT -6.5 ± 3.7, ΔIOPnct -4.4 ± 5.7 and ΔbIOP -3.8 ± 5.4. The differences between ΔGAT vs ΔIOPnct, ΔGAT vs ΔbIOP, and ΔIOPnct vs ΔbIOP, were statistically significant (p < 0.05 for all comparisons). Statistically significant lower values of the stress-strain index (SSI) (1.77 ± 0.3 at baseline vs 1.54 ± 0.27 at the 6-month visit) were found (p = 0.0002). CONCLUSION: The SSI provided by the Corvis ST seems to decrease significantly after topical prostaglandin therapy. We believe that our results support the hypothesis that topical PG therapy does decrease the corneal stiffness and thus, that the ocular hypotensive effect of these drugs is overestimated if GAT is used for IOP measurement.

Optical coherence tomography analysis of filtering blebs after long-term, functioning trabeculectomy and XEN® stent implant.

PURPOSE: The purpose of this study was to use Triton® SweptSource OCT to evaluate the morphology of blebs formed when eyes are treated with XEN® implants and to compare these with the blebs in successfully functioning eyes after trabeculectomy (TB) and with eyes of healthy controls. METHODS: A cross-sectional, observational study. We analyzed 25 eyes, 15 after TB and 10 with XEN® implants, comparing them with 23 healthy eyes (controls). We evaluated the conjunctival morphology of the eyes using AS-OCT. The main parameters evaluated were bleb height, sub-epithelial fibrosis, epithelial thickness, and changes in intraocular pressure (IOP). RESULTS: We found that the filtering blebs formed in eyes in which a XEN® stent was implanted were significantly flatter (bleb height 417 ± 183 µm) than the blebs formed in TB eyes (bleb height 618 ± 256 µm, p < 0.05). Moreover, sub-epithelial fibrosis did not develop in any of the blebs produced by the XEN stent, whereas some fibrosis was evident in 40% of the blebs that formed after TB (p < 0.05). The epithelium was thicker when the XEN implant was used (65 ± 18.5 µm) than when eyes underwent TB (60 ± 17.7 µm), and it was thicker than in control eyes (51 ± 9.7 µm, p < 0.05). Moreover, the decrease in the IOP induced by the XEN® stent (- 8.5 ± 5.3 mmHg) was similar to that produced by TB (- 8.8 ± 5.2 mmHg, p > 0.05). CONCLUSIONS: Filtering blebs obtained after the introduction of a XEN® stent were morphologically distinct to those produced by TB, and they are more similar to the healthy conjunctiva.

Orbscan topography in primary open-angle glaucoma.

PURPOSE: To compare anterior and posterior corneal curvatures between eyes with primary open-angle glaucoma (POAG) and healthy eyes. METHODS: This is a prospective, cross-sectional, observer-masked study. A total of 138 white subjects (one eye per patient) were consecutively recruited; 69 eyes had POAG (study group), and the other 69 comprised a group of healthy control eyes matched for age and central corneal pachymetry with the study ones. Exclusion criteria included any corneal or ocular inflammatory disease, previous ocular surgery, or treatment with carbonic anhydrase inhibitors. The same masked observer performed Goldmann applanation tonometry, ultrasound pachymetry, and Orbscan II topography in all cases. Central corneal thickness, intraocular pressure, and anterior and posterior topographic elevation maps were analyzed and compared between both groups. RESULTS: Patients with POAG had greater forward shifting of the posterior corneal surface than that in healthy control eyes (p < 0.01). Significant differences in anterior corneal elevation between controls and POAG eyes were also found (p < 0.01). CONCLUSIONS: Primary open-angle glaucoma eyes have a higher elevation of the posterior corneal surface than that in central corneal thickness-matched nonglaucomatous eyes.

Predictive Value of Dynamic Corneal Response Parameters Evaluated with Scheimpflug High-Speed Video (Corvis ST) on the Visual Field Progression in Prostaglandin Treated Ocular Hypertension and Open-Angle Glaucoma Patients.

INTRODUCTION: The aim of this work is to compare the Corvis ST stress-strain index (SSI) and highest concavity (HC) parameters at baseline and 1 month after initiating monotherapy with prostaglandin analogues (PGs) in eyes showing visual field (VF) progression or stability. METHODS: In this prospective, single-center, observational study, newly diagnosed and treatment-naïve OAG patients were examined at baseline and 1 month after beginning monotherapy with topical PGs monotherapy. Goldmann applanation tonometry pressure readings, Corneal Hysteresis (ORA-CH), and the Corvis ST measurements were obtained at both visits. VF progression (Humphrey) was evaluated based on data from 6 years of follow-up after the baseline visit. Stress-strain index (SSI) and HC parameters in progressing (P) and non-progressing (NP) eyes were the main outcome measures. RESULTS: Sixty-three eyes were analyzed; mean age was 64.63 ± 11.26 years; 47 eyes were NP and 16 eyes were P according to the event analysis performed by the Humphrey device. There were no significant differences in IOP, CCT, or Corvis parameters between NP and P groups at baseline. Nevertheless, at 1 month, the SSI index was 1.60 ± 0.34 vs. 1.80 ± 0.34 (p = 0.003) in NP vs. P eyes, respectively. HC parameters were different between the groups at 1 month (p < 0.05) suggesting an increased scleral rigidity in the P group. There was no significant difference in IOP between groups at 1 month. CONCLUSIONS: The Corvis ST provides a corneal rigidity index (SSI) that seems to be related to VF progression when measured 1 month after initiating PGs monotherapy. Differences in HC parameters, indicative of increased scleral stiffness, are also evident at 1 month on latanoprost in the P eyes.

Charles Bonnet syndrome as first manifestation of occipital infarction.

PURPOSE: To describe a case of Charles Bonnet syndrome as the first manifestation of occipital infarction in a patient with preserved visual acuity. OBSERVATIONS: We report a 78-year-old man followed in our department with a two-month-long history of visual hallucinations based on the vision of flowers and fruits intermittently, being perceived as unreal images. Best-corrected visual acuity was stable in the follow-up time being 20/20 in the right eye and 20/25 in the left eye. Extraocular muscle function testing, pupillary reflexes, biomicroscopy, fundus and optical coherence tomography examinations did not reveal any interesting findings. In order to rule out occipital pathology, orbital-cerebral magnetic resonance imaging was performed, showing an image compatible with the chronic ischemic right occipital lesion. The patient was diagnosed with Charles Bonnet syndrome secondary to occipital infarction and neurology decided that no treatment was required. 24-2 and 10-2 visual field tests showed no remarkable alterations and Full-field 120 point screening test showed nonspecific peripheral defects. Hallucinations improved over the months, being described as not annoying and increasingly infrequent. CONCLUSIONS AND IMPORTANCE: Charles Bonnet syndrome is a condition characterized by the presence of recurrent and complex visual hallucinations in patients with visual pathway pathologic defects. Visual acuity or visual field loss is not a requirement for diagnosis. Charles Bonnet syndrome should be suspected in all patients with non-disturbing visual hallucinations, even though they present good visual acuteness. It will be essential to perform complementary explorations to identify the underlying pathology that allows the starting of a correct treatment option.

Corneal Factors Associated with the Amount of Visual Field Damage in Eyes with Newly Diagnosed, Untreated, Open-angle Glaucoma.

INTRODUCTION: The aim of this study was to evaluate the correlation between several ocular parameters (intraocular pressure [IOP], corneal biomechanical properties) and the visual field (VF) mean deviation (VF MD) in eyes with open-angle glaucoma (OAG). METHODS: We conducted a cross-sectional, observational study in which we measured the IOP with Goldmann applanation tonometry, the central corneal thickness (CCT), and the corneal parameters obtained from the Ocular Response Analyzer® (ORA®) and the Corvis® ST non-contact tonometer, in newly diagnosed and treatment-naïve eyes with OAG, to investigate whether there was any correlation between these ocular parameters and the VF MD. RESULTS: A total of 51 eyes were analyzed. A statistically significant correlation was found only between the VF MD and corneal hysteresis (CH) (P = 0.003, r2 = 0.16) and CCT (P = 0.03, r2 = 0.08). CONCLUSIONS: These results demonstrate that CH and CCT are associated with the amount of VF damage in treatment-naïve OAG eyes.

Measurement of the Intraocular Pressure Elevation During Laser-Assisted In Situ Keratomileusis Flap Creation Using a Femtosecond Laser Platform.

Purpose: The purpose of this study was to measure the intraocular pressure (IOP) elevation during laser assisted in situ keratomileusis (LASIK) flap creation using the WaveLight FS200 femtosecond (FS) laser platform. Methods: We conducted an ex vivo experimental study in an animal model. The WaveLight FS200 FS laser platform was used to perform the corneal LASIK flap in freshly enucleated porcine eyes. We measured the changes in IOP from the application of the suction ring (suctioning phase) through the creation of the lamellar corneal flap (cutting phase). The IOP was recorded using a manometric technique with direct cannulation to the anterior chamber. Results: Nine freshly enucleated porcine eyes were included in the study. The mean baseline IOP before the procedure was 20.33 ± 5.9 mm Hg. The mean IOP increase over baseline IOP was 32.33 ± 11.3 mm Hg at the suctioning phase, and 38.22 ± 11.3 mm Hg at the cutting phase. The total surgical time needed to complete the procedure was 29.5 ± 4.4 seconds. Conclusions: The WaveLight FS200 FS laser platform produces a low to moderate increase in IOP during LASIK flap creation. Translational Relevance: The WaveLight FS200 is a safe FS laser platform because it induces a low to moderate IOP increase during LASIK flap creation.

Short-term effect of topical brimonidine tartrate on intrastromal corneal pressure in rabbits.

PURPOSE: Because topical brimonidine tartrate has been reported to decrease flap adherence in the early postoperative period after LASIK, its effect on the intrastromal corneal pressure (ICP) was evaluated. METHODS: An interventional, prospective, animal study was performed. Intrastromal corneal pressure was recorded for 45 minutes in eight eyes of rabbits treated with topical brimonidine tartrate three times daily for 3 consecutive days (study group); eight contralateral eyes were treated with artificial tears (control group). All measurements were performed by the same, masked investigator. RESULTS: Mean ICP was -4.00 +/- 2.90 mmHg, -6.70 +/- 3.00 mmHg, and -9.00 +/- 4.50 mmHg at 15, 30, and 45 minutes, respectively, in the control group. In the study group (brimonidine-treated eyes), the ICP readings were +2.75 +/- 2.90 mmHg, -2.50 +/- 13.00 mmHg, and -8.50 +/- 5.00 mmHg at the same time points, respectively. The differences in the ICP between both groups were statistically significant at 15 minutes (P = .01), but no significant difference was found at 30 or 45 minutes (P = .20 and P = .80, respectively). CONCLUSIONS: Topical treatment with brimonidine tartrate induces a significant decrease in ICP at 15 minutes. This effect on ICP may explain the decreased corneal flap adherence reported in eyes treated with this drug.

Corneal Ectasia Induced by Prostaglandin Analogues.

Our purpose is to document the first case of unilateral mild corneal ectasia developed in an apparently nonpredisposed cornea after topical latanoprost treatment, and its regression after treatment withdrawal. We describe a 44-year-old man with visual impairment in his left eye (OS) and a past medical history of myopic refraction and ocular hypertension with latanoprost treatment, the rest of ocular examination was normal. A decrease in visual acuity was observed with a refractive change. Corneal tomography showed features of mild corneal ectasia in his OS. Topical prostaglandin analogue therapy was removed and replaced by other antiglaucoma topical treatment. Corneal tomography returned to normal, an improvement in the quality of vision was observed and refractive astigmatism recovered to baseline values. This case illustrates that topical latanoprost does affect the matrix metalloproteinases balance in corneal extracellular matrix, and subsequently may produce a corneal weakening. Corneal biomechanical features and corneal stiffness do probably recover after topical prostaglandin analogues withdrawal.

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.

Intraocular pressure rises during laser in situ keratomileusis: Comparison of 3 femtosecond laser platforms.

PURPOSE: To measure intraocular pressure (IOP) elevations in porcine eyes during laser in situ keratomileusis (LASIK) performed using 3 femtosecond laser platforms. SETTING: Clínica Novovisión, Madrid, Spain. DESIGN: Experimental study. METHODS: Three femtosecond devices, the iFS 150 kHz, which is the newest-generation IntraLase with a flat interface, and the Victus and LenSx, which are both dual femtosecond lasers with curved interfaces, were used to create lamellar corneal flaps in freshly enucleated porcine eyes. The IOP was recorded during placement of the suction ring on the eye (suctioning phase) and during the intrastromal laser application for flap creation (cutting phase) using a manometric technique with direct cannulation to the anterior chamber. RESULTS: Twenty-one eyes were analyzed (7 per group). The mean IOP increase during suctioning was significantly higher with the iFS system (78.14 mm Hg ± 23.6 [SD]) than with the Victus system (20.28 ± 6.7 mm Hg) (P = .0001). The LenSx system performed the suctioning and applanation phases simultaneously, making it impossible to obtain the results of the suctioning phase alone. The mean IOP elevation during the cutting phase was significantly lower with the LenSx system (20 ± 5.3 mm Hg) than with the iFS (108.1 ± 17.0 mm Hg) and Victus (96.4 ± 16.8 mm Hg) systems (P = .0001). The total surgical time was significantly lower with the LenSx system (17.21 ± 0.7 seconds) than with the iFS (25.10 ± 4.3 seconds) and Victus (33.40 ± 0.7 seconds) systems (P = .0001). CONCLUSION: The preliminary results suggest that the iFS and Victus systems induced higher IOP increases and required longer surgical times to cut a LASIK flap than the LenSx system.

Outcomes of Trabeculectomy and Phacotrabeculectomy With Collagen Matrix Implant (Ologen) and Low-dose Mitomycin C: 2-Year Follow-up.

PURPOSE: The purpose of this article is to analyze the results achieved in lowering intraocular pressure (IOP) after trabeculectomy or combined surgery (phacotrabeculectomy) with low-dose mitomycin C (MMC) using the Ologen Collagen Matrix (Ologen CM) implant. MATERIALS AND METHODS: This retrospective study included 58 eyes from 47 consecutive patients with glaucoma who underwent filtering surgery alone or combined with cataract surgery. The study group included 29 eyes that underwent trabeculectomy (14 eyes) or phacotrabeculectomy (15 eyes) with low-dose MMC (0.1 mg/mL×1 min) and subconjunctival Ologen CM implant at the end of surgery. The control group included 29 eyes, 12 that underwent trabeculectomy and 17 that underwent phacotrabeculectomy, with the same MMC dose but without the collagen matrix implant. All surgical procedures were performed by the same surgeon. The follow-up period for the patients was 2 years. RESULTS: We found statistically significant differences between the 2 groups in the age of the patients (P=0.02). We found no statistically significant differences in the baseline IOP (P=0.37) or preoperative IOP (P=0.5), nor in the visual field damage measured with mean deviation (P=0.2). The number of hypotensive medications used preoperatively was higher in the study group (P=0.0001). At 1 and 2 years after surgery, we only found statistically significant differences in favor of the study group in patients who underwent phacotrabeculectomy (P=0.0008 and 0.02, respectivily). CONCLUSION: The Ologen CM implant can be considered as an adjunct to MMC in patients undergoing filtering surgery combined with phacoemulsification to improve postoperative IOP results over the long term.

Porcine model to compare real-time intraocular pressure during LASIK with a mechanical microkeratome and femtosecond laser.

PURPOSE: To compare real-time intraocular pressure (IOP) during laser in situ keratomileusis (LASIK) in porcine eyes using two types of microkeratomes. METHODS: An interventional, prospective study of two microkeratomes: a Moria 2 (Moria group) and an IntraLase femtosecond laser (IntraLase Corp., Irvine, CA; IntraLase group). These devices were used to create lamellar corneal flaps in freshly enucleated porcine eyes. The IOP changes induced by the procedures were recorded with a reusable blood pressure transducer connected to the anterior chamber by direct cannulation. RESULTS: Seven porcine eyes were studied in each group. The IOP increased during the suctioning phase, reaching a mean of 122.52 +/- 30.40 and 160.52 +/- 22.73 mm Hg during the cutting phase in the Moria group (the total time in this group was 36.42 +/- 7.48 seconds; suctioning required 21.42 +/- 7.48 seconds and the cutting phase, 15 +/- 2.88 seconds). In the IntraLase group, the IOP reached 89.24 +/- 24.26 mm Hg during the suctioning phase and 119.33 +/- 15.88 mm Hg during the intrastromal laser application (the total time was 92.85 +/- 13.49 seconds; suctioning required 40.00 +/- 9.57 seconds and the cutting phase 52.85 +/- 5.66 seconds). Both IOPs during both phases differed significantly between the two groups (P = 0.01 for all comparisons). CONCLUSIONS: Real-time IOP can be measured during LASIK using a transducer connected to the anterior chamber. The results showed a significant increase in IOP during the procedure in both groups, although with the IntraLase the IOP seemed to increase to a lesser extent than with the conventional mechanical microkeratome.

Short-term effects of latanoprost on anterior chamber depth in patients with glaucoma or ocular hypertension.

PURPOSE: Prostaglandin F(2alpha) analogues, such as latanoprost, may cause a decrease in the extracellular matrices, such as collagen, and changes in fibrillin-1; both are components of the ciliary zonules. However, the mechanical effect of these changes on the dynamics of the ciliary zonules is unknown. This study was conducted to evaluate the effect of latanoprost 0.005% on anterior chamber depth (ACD), best corrected visual acuity (BCVA), lens thickness, and anterior chamber dynamics in patients with glaucoma or ocular hypertension. METHODS: This was a prospective, nonrandomized, autocomparative trial that included 40 patients (40 eyes) with glaucoma or ocular hypertension. ACD was measured with ultrasonography before and after 1 month of treatment with latanoprost. In addition, ACD was measured before and 1 hour after instillation of pilocarpine 2% at baseline and 1 month after treatment with latanoprost. To assess the reproducibility of the ultrasonic measurements, a control group of 20 patients (20 eyes) who did not receive latanoprost was also analyzed. RESULTS: The mean ACD before treatment with latanoprost and before the instillation of pilocarpine was 3.14 +/- 0.46 mm (SD) and after the instillation of pilocarpine, 3.04 +/- 0.46 mm (SD). After 1 month of treatment with latanoprost, ACD was 2.98 +/- 0.44 mm (SD) before instillation of pilocarpine and 2.91 +/-0.49 mm (SD) after instillation of pilocarpine. P < or = 0.05 was reached for all comparisons. CONCLUSIONS: These findings suggest that latanoprost decreases ACD in patients with glaucoma or ocular hypertension after 1 month of treatment.

Porcine Model to Evaluate Real-Time Intraocular Pressure During Femtosecond Laser Cataract Surgery.

PURPOSE: To investigate the changes in intraocular pressure (IOP) in porcine eyes during femtosecond laser-assisted cataract surgery using a liquid-optic interface system. MATERIALS AND METHODS: Femtosecond laser cataract surgery with the Catalys™ was performed on freshly enucleated porcine eyes in Oftalvist Moncloa, Madrid, Spain. Capsulorhexis and lens fragmentation were completed in all the eyes without complications. IOP was measured with a reusable blood pressure transducer connected by direct cannulation to the anterior chamber, recording data before suction (basal), at the beginning of the suction phase, every five seconds during femtosecond procedure and after the removal of the suction ring from the eye. RESULTS: Nine porcine eyes were used in this study. Basal IOP before suction was 5.67 ± 2.39 mmHg, rising to 20.33 ± 4.18 mmHg at the beginning of the suction phase (p < 0.001). During femtosecond procedure, pressure reached a value of 19.74 ± 4.31 mmHg, remaining stable during the entire process. The IOP recorded prior to removal of the suction ring was 21.00 ± 6.93 mmHg, returning to basal values in all the eyes after the suction ring was removed, with no statistical differences between basal and post-suction IOPs. Total femtosecond procedure time was 125.9 ± 15.9 s. CONCLUSIONS: Real-time IOP can be measured during surgery using a transducer connected to the anterior chamber. The results showed a significant increase in IOP during the procedure due to the pressure exerted by the suction ring but not by the effect of the femtosecond laser.

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.

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.

Simultaneous measurement of intraocular pressure in the anterior chamber and the vitreous cavity.

PURPOSE: To simultaneously measure, using manometry, the changes of intraocular pressure (IOP) in the anterior chamber and in the vitreous cavity of a single porcine eye, induced by an external column of water. METHODS: We prospectively measured IOP simultaneously in seven freshly enucleated porcine eyes in both the anterior chamber and the vitreous cavity. Measurements were obtained through blood-pressure transducers connected to 21-gauge catheters. A third cannula was inserted into the anterior chamber to increase the IOP; when the cannula was connected to the water column, the pressure increased rapidly from 0 to 180 mmHg. Changes were registered every 5 seconds during the first minute. Statistical analysis was performed using the Wilcoxon signed-rank test. P ≤ 0.05 was considered significant. RESULTS: Before the IOP was increased, the median basal IOP value was 18 mmHg in the anterior chamber and 23 mmHg in the vitreous cavity (P > 0.05). Sixty seconds after the end of the experiment, the median IOP value was 135 mmHg (range 122-145) in the anterior chamber and 55 mmHg (range 16-68) in the vitreous cavity (P < 0.01). CONCLUSION: Cannulation of the anterior chamber measures the actual IOP; however, the IOP measured by cannulation in the vitreous cavity using the same catheter diameter was different, possibly because of the viscosity of the vitreous. The viscosity of the vitreous probably makes the cannulation method of IOP evaluation in the vitreous cavity inaccurate.

Short-term effect of topical dorzolamide hydrochloride on intrastromal corneal pressure in rabbit corneas in vivo.

PURPOSE: To evaluate the effect of topical dorzolamide on the intrastromal corneal pressure (ICP) in rabbit corneas in vivo. METHODS: This is an interventional prospective study. Topical dorzolamide was applied to 7 eyes of 7 male New Zealand rabbits 3 times daily for 3 consecutive days. The ICP changes were recorded with a pressure transducer connected to the midperipheral cornea. The ICP was measured in the same manner in 7 eyes of 7 male New Zealand rabbits that were treated with artificial tears (control group). RESULTS: The ICP values averaged -6.2 +/- 3.2, -10 +/- 5.8, and -12.5 +/- 8.7 mm Hg at 15, 30, and 45 minutes in the control group, respectively. In the dorzolamide-treated eyes, the ICP readings were 1.8 +/- 3.4, -0.28 +/- 4.3, and -1.8 +/- 5.3 mm Hg at the same time points, respectively. The differences in the ICP between both groups were significantly different at all time points (P = 0.004, P = 0.005, and P = 0.02). CONCLUSIONS: Measuring ICP is a valid and sensitive method to evaluate in vivo the endothelial function. This method seems to be more sensitive than measuring the central corneal thickness or the corneal deswelling rate in detecting changes in the corneal physiology with the use of topical dorzolamide.