Development of experimental chronic intraocular hypertension in the rabbit

The Anti-Inflammatory and Antioxidant Properties of Acebuche Oil Exert a Retinoprotective Effect in a Murine Model of High-Tension Glaucoma

Glaucoma is characterized by cupping of the optic disc, apoptotic degeneration of retinal ganglion cells (RGCs) and their axons, and thinning of the retinal nerve fiber layer, with patchy loss of vision. Elevated intraocular pressure (IOP) is a major risk factor for hypertensive glaucoma and the only modifiable one. There is a need to find novel compounds that counteract other risk factors contributing to RGC degeneration. The oil derived from the wild olive tree (Olea europaea var. sylvestris), also called Acebuche (ACE), shows powerful anti-inflammatory, antioxidant and retinoprotective effects. We evaluated whether ACE oil could counteract glaucoma-related detrimental effects. To this aim, we fed mice either a regular or an ACE oil-enriched diet and then induced IOP elevation through intraocular injection of methylcellulose. An ACE oil-enriched diet suppressed glaucoma-dependent retinal glia reactivity and inflammation. The redox status of the glaucomatous retinas was restored to a control-like situation, and ischemia was alleviated by an ACE oil-enriched diet. Notably, retinal apoptosis was suppressed in the glaucomatous animals fed ACE oil. Furthermore, as shown by electroretinogram analyses, RGC electrophysiological functions were almost completely preserved by the ACE oil-enriched diet. These ameliorative effects were IOP-independent and might depend on ACE oil's peculiar composition. Although additional studies are needed, nutritional supplementation with ACE oil might represent an adjuvant in the management of glaucoma.

Cationic liposomes as promising vehicles for timolol/brimonidine combination ocular delivery in glaucoma: formulation development and in vitro/in vivo evaluation

Glaucoma is a chronic eye disease in which the pressure inside the eye increases and leads to damage to the optic nerve, and eventually causes blindness. In this disease, it is often necessary to use a multi-drug treatment system. There is a fixed combination of timolol maleate and brimonidine tartrate among the combination drugs in glaucoma treatment. Liposomes are one of the most important targeted drug delivery systems to eye tissue, which leads to improved drug permeability and durability in ocular tissue. In this study, thin layer hydration was used to make liposomal formulations containing timolol maleate (TM) and brimonidine tartrate (BT). After the necessary evaluations, one of the eight initial formulations was selected as an optimization formulation. Then, characteristics such as drug loading percentage, particle size, pH, zeta potential, and drug release were performed on the optimized formulation. The study of reducing intraocular pressure was performed on the optimized formulation. This study in total was performed on 18 rabbits in three groups. Hydroxypropyl methylcellulose (HPMC) polymer was injected into the anterior chamber to experimental induce glaucoma. The selected formulation was within the acceptable range of ocular products in terms of physical properties. HPMC polymer injection successfully induced glaucoma in the animal model, resulting in a 79% increase in intraocular pressure. The results showed that the liposomal formulation significantly reduced the intraocular pressure compared to the simple formulation of the aqueous solution, and both formulations were able to significantly reduce the intraocular pressure compared to the control group (P < 0.001). The results also showed that liposomal formulation has a therapeutic effect in reducing intraocular pressure. It seems that the selected liposomal formulation made by thin layer hydration can act as a suitable drug carrier to increase the effectiveness of the fixed combination of timolol maleate and brimonidine tartrate and be proposed as a new drug formulation for targeted and controlled drug delivery in the treatment of glaucoma.

A Topical Formulation of Melatoninergic Compounds Exerts Strong Hypotensive and Neuroprotective Effects in a Rat Model of Hypertensive Glaucoma

Melatonin is of great importance for regulating several eye processes, including pressure homeostasis. Melatonin in combination with agomelatine has been recently reported to reduce intraocular pressure (IOP) with higher efficacy than each compound alone. Here, we used the methylcellulose (MCE) rat model of hypertensive glaucoma, an optic neuropathy characterized by the apoptotic death of retinal ganglion cells (RGCs), to evaluate the hypotensive and neuroprotective efficacy of an eye drop nanomicellar formulation containing melatonin/agomelatine. Eye tissue distribution of melatonin/agomelatine in healthy rats was evaluated by HPLC/MS/MS. In the MCE model, we assessed by tonometry the hypotensive efficacy of melatonin/agomelatine. Neuroprotection was revealed by electroretinography; by levels of inflammatory and apoptotic markers; and by RGC density. The effects of melatonin/agomelatine were compared with those of timolol (a beta blocker with prevalent hypotensive activity) or brimonidine (an alpha 2 adrenergic agonist with potential neuroprotective efficacy), two drugs commonly used to treat glaucoma. Both melatonin and agomelatine penetrate the posterior segment of the eye. In the MCE model, IOP elevation was drastically reduced by melatonin/agomelatine with higher efficacy than that of timolol or brimonidine. Concomitantly, gliosis-related inflammation and the Bax-associated apoptosis were partially prevented, thus leading to RGC survival and recovered retinal dysfunction. We suggest that topical melatoninergic compounds might be beneficial for ocular health.

Evaluation of efficacy of Aloe vera (L.) Burm. f. gel solution in methylcellulose-induced ocular hypertension in New Zealand white rabbits

Objectives The present study aimed to evaluate the efficacy of Aloe vera in the methylcellulose-induced ocular hypertension model. Methods Fifty-six rabbits were randomly divided into seven groups. Intraocular pressure (IOP) was raised by anterior chamber injection of 2% methylcellulose in all the groups except the normal control group. Disease control animals were treated with sterile water and active control with topical 0.5% timolol 12 hourly; 6 and 12% A. vera gel topical solutions 8 hourly were given in group IV and V, respectively; 6 and 12% A. vera gel solutions along with timolol were given in group VI and VII animals, respectively. Mean IOP values and percentage of reduction in IOP were compared at 15 min, 30 min, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 36 h, and 48 h. Results A. vera gel solutions (6 and 12%) showed a significant reduction in mean IOP from 4 to 2 h time points, respectively, whereas, A. vera gel solutions (6 and 12%) + timolol showed significant less mean IOP from a 30 min time point as compared with disease control. A. vera gel solutions (6 and 12%) showed 8.6 and 10.4% more reduction in IOP, respectively (66.8 ± 4.9% and 68.6 ± 5.4% vs. 58.2 ± 2.3%; p > 0.05), whereas 6 and 12% A. vera gel solutions along with timolol showed 14.5 and 16.2% more reduction in IOP, respectively (72.7 ± 4.7% and 74.4 ± 4.1% vs. 58.2 ± 2.3%; p < 0.05), than disease control group at 48 h. Conclusions Six and twelve percent A. vera gel solutions reduced the IOP effectively. Concurrent treatment with 12% A. vera gel and timolol produced the maximum reduction in IOP.

A Dietary Combination of Forskolin with Homotaurine, Spearmint and B Vitamins Protects Injured Retinal Ganglion Cells in a Rodent Model of Hypertensive Glaucoma

There is indication that nutritional supplements protect retinal cells from degeneration. In a previous study, we demonstrated that dietary supplementation with an association of forskolin, homotaurine, spearmint extract and B vitamins efficiently counteracts retinal dysfunction associated with retinal ganglion cell (RGC) death caused by optic nerve crush. We extended our investigation on the efficacy of dietary supplementation with the use of a mouse model in which RGC degeneration depends as closely as possible on intraocular pressure (IOP) elevation. In this model, injecting the anterior chamber of the eye with methylcellulose (MCE) causes IOP elevation leading to RGC dysfunction. The MCE model was characterized in terms of IOP elevation, retinal dysfunction as determined by electrophysiological recordings, RGC loss as determined by brain-specific homeobox/POU domain protein 3A immunoreactivity and dysregulated levels of inflammatory and apoptotic markers. Except for IOP elevation, dysfunctional retinal parameters were all recovered by dietary supplementation indicating the involvement of non-IOP-related neuroprotective mechanisms of action. Our hypothesis is that the diet supplement may be used to counteract the inflammatory processes triggered by glial cell activation, thus leading to spared RGC loss and the preservation of visual dysfunction. In this respect, the present compound may be viewed as a potential remedy to be added to the currently approved drug therapies for improving RGC protection.

Hypotensive Effect of Nanomicellar Formulation of Melatonin and Agomelatine in a Rat Model: Significance for Glaucoma Therapy

BACKGROUND

Melatoninergic agents are known to reduce intraocular pressure (IOP). The present study was performed to evaluate the effect of nanomicellar formulations of melatoninergic agents on IOP in the rat.

METHODS

Tonometry was used to measure IOP in eyes instilled with melatonin or agomelatine. Ocular hypertension was induced by the injection of methylcellulose in the anterior chamber.

RESULTS

Melatonin formulated in nanomicelles had a longer lasting hypotonizing effect on IOP with respect to melatonin in saline. Nanomicellar formulations of melatonin and agomelatine, either alone or in combination, had lowering effects that did not depend on their concentration or their combination, which, however, resulted in an increased duration of the hypotonizing effect. The duration of the lowering effect was further increased by the addition of lipoic acid.

CONCLUSIONS

We demonstrated the effective hypotonizing activity of melatonin and agomelatine in combination with lipoic acid. Although results in animals cannot be directly translated to humans, the possibility of developing novel therapeutical approaches for patients suffering from hypertensive glaucoma should be considered.

Enhancement of pharmacokinetic and pharmacological behavior of ocular dorzolamide after factorial optimization of self-assembled nanostructures

Dorzolamide hydrochloride is frequently administered for the control of the intra-ocular pressure associated with glaucoma. The aim of this study is to develop and optimize self-assembled nanostructures of dorzolamide hydrochloride and L-α-Phosphatidylcholine to improve the pharmacokinetic parameters and extend the drug pharmacological action. Self-assembled nanostructures were prepared using a modified thin-film hydration technique. The formulae compositions were designed based on response surface statistical design. The prepared self-assembled nanostructures were characterized by testing their drug content, particle size, polydispersity index, zeta potential, partition coefficient, release half-life and extent. The optimized formulae having the highest drug content, zeta potential, partition coefficient, release half-life and extent with the lowest particle size and polydispersity index were subjected to further investigations including investigation of their physicochemical, morphological characteristics, in vivo pharmacokinetic and pharmacodynamic profiles. The optimized formulae were prepared at pH 8.7 (F5 and F6) and composed of L-α-Phosphatidylcholine and drug mixed in a ratio of 1:1 and 2:1 w/w, respectively. They showed significantly higher Cmax, [Formula: see text] and [Formula: see text] at the aqueous humor with extended control over the intra-ocular pressure, when compared to the marketed product; Trusopt®. The study introduced novel and promising self-assembled formulae able to permeate higher drug amount through the cornea and achieve sustained pharmacological effect at the site of action.

Neuroprotective effect of Erigeron Breviscapus (vant) Hand-mazz extract on retinal ganglion cells in rabbits with chronic elevated intraocular pressure

Background: Retinal ganglion cells (RGCs) are protected in rats with acute elevated intraocular pressure (IOP) by Erigeron breviscapus (vant.) hand-mazz (EBHM). However, it is unclear whether EBHM has neuroprotective effect on RGCs in animal with chronic elevated IOP.

Objective: Investigate the protective effect of EBHM extract on RGCs in rabbits with chronic elevated IOP.

Methods: Unilateral chronic elevated IOP was produced in rabbits by repeated injection of 2% methylcellulose into the anterior chamber. Secondary degeneration was measured with and without EBHM extract treatment for 60 days. At 60 days, the cells density of the RGCs layer, the thickness of retinal nerve fiber layer (RNFL), and the optic nerve axons were observed and analyzed using an image analysis system. The ultrastructural changes of RGCs and optic nerve axons were observed using transmission electron microscopy.

Results: Compared with their contralateral control eyes with normal IOP, in the retinas of 3-4 mm from the optic disc, the cells density of the RGCs layer in the eyes with chronic elevated IOP was 23.2±6.5 cells (n = 6) and 36.0±8.9 cells (n = 10) per three 400x fields at 60 days in untreated and EBHM-treated group, respectively. The RNFL thickness in eyes with chronic elevated IOP was 3.4±0.4 μm (n = 6) and 5.0±1.0 μm (n = 10) at 60 days in untreated and EBHM-treated group, respectively. The axons number per 15057.8 μm2 in eyes with chronic elevated IOP was 370.4±41.0 (n = 6) and 439.0±50.8 (n = 10) at 60 days in untreated and EBHM-treated group, respectively. The number of the organelles in RGCs plasm appeared decreased and mitochondrion vacuolated in the elevated IOP eyes of EBHM-treated group, while some dispersive mitochondrion and rough surfaced endoplasmic reticulum and ribosome still existed in the RGCs plasm. The myelin sheath plates condensed and degenerated, and the microfilaments and microtubules decreased or disappeared in the elevated IOP eyes, but the axons degeneration in the chronic elevated IOP with EBHM treatment was less than that in the chronic elevated IOP without treatment.

Conclusion: EBHM extract provided a neuroprotective effect on retinal ganglion cells in rabbits with chronic elevated IOP.

Preparation, pharmacokinetics and pharmacodynamics of ophthalmic thermosensitive in situ hydrogel of betaxolol hydrochloride

Conventional ophthalmic formulations often eliminate rapidly after administration and cannot provide and maintain an adequate concentration of the drug in the precorneal area. To solve those problems, a thermosensitive in situ gelling and mucoadhesive ophthalmic drug delivery system was prepared and evaluated, the system was composed of poloxamer analogs and polycarbophil (PCP) and betaxolol hydrochloride (BH) was selected as model drug. The concentrations of poloxamer 407 (P407) (22% (w/v)) and poloxamer 188 (P188) (3.5% (w/v)) were identified through central composite design-response surface methodology (CCD-RSM). The BH in situ hydrogel (BH-HG) was liquid solution at low temperature and turned to semisolid at eye temperature. BH-HG showed good stability and biocompatibility, which fulfilled the requirements of ocular application. In vitro studies indicated that addition of PCP enhanced the viscosity of BH-HG and the release results of BH from BH-HG demonstrated a sustained release behavior of BH because of the gel dissolution. In vivo pharmacokinetics and pharmacodynamics studies indicated that the BH-HG formulation resulted in an improved bioavailability and a significantly lower intraocular pressure (IOP). The results suggested BH-HG could be potentially used as an in situ gelling system for ophthalmic delivery to enhance the bioavailability and efficacy.

Clinical application of 11-deoxycortisol in visualizing prolapsed vitreous body after posterior capsule rupture in cataract surgery

PURPOSE

To evaluate the clinical usefulness of 11-deoxycortisol, a precursor of cortisol in steroid metabolism, in visualizing the vitreous body in the anterior chamber after posterior capsule rupture during cataract surgery.

SETTING

Department of Ophthalmology, Tsukuba University Hospital, Ibaraki, Japan.

METHODS

Eight eyes had anterior vitrectomy during cataract surgery using this new technique. A suspension of 11-deoxycortisol was prepared by dilution in balanced salt solution without preservatives or emulsifying agents. After a posterior capsule rupture, the suspension was injected into the anterior chamber. The visual and anatomical outcomes of surgery were evaluated during a follow-up of 7 to 9 months.

RESULTS

After the 11-deoxycortisol injection, the vitreous body that had prolapsed through the torn posterior capsule, with white particles entrapped on its surface, became clearly visible. Complete removal of the prolapsed vitreous body was achieved easily and safely using an anterior vitrectomy system. No postoperative complications related to the use of 11-deoxycortisol were observed.

CONCLUSION

Injection of 11-deoxycortisol helped visualize the vitreous body in the anterior chamber after posterior capsule rupture. The technique minimized intraoperative and postoperative complications related to posterior capsule rupture and vitreous loss during cataract surgery [corrected]

Stereoselectivity of satropane, a novel tropane analog, on iris muscarinic receptor activation and intraocular hypotension

AIM

To study the stereoselectivity of satropane (3-paramethylbenzene sulfonyloxy-6-acetoxy tropane), a novel tropane analog, on iris muscarinic receptor activation and intraocular hypotension.

METHODS

The assays for radioligand-receptor binding, the contractile responses of isolated iris muscle, the miosis response, and the intraocular hypotension of the enantiomers of satropane were investigated.

RESULTS

In the binding analysis, S(-)satropane (lesatropane) completely competed against the [3H]quinuclydinyl benzilate-labeled ligand at muscarinic receptors in the iris muscle, whereas R(+)satropane failed to completely compete. In an isolated iris contractile assay, R,S(+/-)satropane and S(-)satropane produced a concentration-dependent contractile response with similar efficacy and potency to that of carbachol. R(+)satropane did not induce any contractile response. In the pupil diameter measurement assay in vivo, S(-)satropane induced miosis much more effectively than pilocarpine, while R(+)satropane failed to produce any miosis. In the water loading-induced and methylcellulose-induced ocular hypertensive models, S(-)satropane, but not R(+)satropane, significantly suppressed intraocular pressure at a much lower concentration than pilocarpine.

CONCLUSION

The agonistic and hypotensive properties of satropane on rabbit eyes are stereoselective, with the S(-)isomer being its active form.

Degenerative and apoptotic events at retinal and optic nerve level after experimental induction of ocular hypertension

Ocular hypertension is a symptom of a glaucomatous condition characterized by a severe vision decrease. Blindness caused by the apoptotic death of the retinal ganglion cells and of the astrocytes of the optic nerve may eventually result. Experimental hypertension was induced by inoculation of methylcellulose in the anterior chamber. Chromatin staining, TUNEL assay, and inter-nucleosomal DNA fragmentation observed in retina and optic nerve strongly suggest that hypertension causes apoptosis. Immunolocalization of the fibrillary acidic glial protein, specific of cell stress, and caspase-3 in the same tissues, further support this mode of cell death. Activation of the ubiquitin dependent proteolytic system was also observed. Protection from apoptosis exerted by administration of the peroxide scavenger trolox, suggests that the apoptotic pathway is activated by an oxidative stress. The data presented here show that the experimental hypertensive insult induces degenerative and apoptotic events comparable to those observed in human glaucoma.

Clinical outcomes of combined sutureless vitrectomy with triamcinolone stain to manage vitreous loss resulting from posterior capsule rupture during phacoemulsification

PURPOSE

To investigate the efficacy of sutureless pars plana vitrectomy (PPV) combined with intracameral triamcinolone stain in the management of vitreous loss associated with phacoemulsification.

SETTING

Department of Ophthalmology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China.

METHODS

This retrospective review comprised the charts of 21 patients who had sutureless PPV combined with intracameral triamcinolone stain to manage vitreous loss resulting from posterior capsule rupture during phacoemulsification. The charts were analyzed for type of cataract, posterior segment pathology, methods of anesthesia, intraocular lens (IOL) placement, postoperative visual acuity, intraocular pressure, and complications. Additional outcome measurements were duration of the surgical procedures, period of postoperative corneal edema, and time to achieve stable vision.

RESULTS

Excluding 2 eyes with preexisting conditions, 18 of 19 eyes (94.7%) had a final best corrected visual acuity (BCVA) of 20/40 or better and 42.1% (8/19) had a final BCVA of 20/20 or better. The mean duration of the surgery was 25.3 minutes (range 16 to 40 minutes). Corneal edema was noted in 12 eyes (57.1%) 3 days postoperatively and 3 eyes (14.3%) at 7 days. Eleven eyes (52.4%) had stable vision at 1 week, and 16 eyes (76.2%) had stable vision within 1 month postoperatively. Four eyes (19.0%) had postoperative complications that included a displaced IOL in 3 eyes (14.3%) and cystoid macular edema in 1 eye (4.8%).

CONCLUSIONS

Self-sealing, sutureless PPV combined with intracameral triamcinolone stain was a safe, reliable adjunct to manage vitreous loss during phacoemulsification. The surgery led to rapid visual recovery.

Visualizing the vitreous body in the anterior chamber using 11-deoxycortisol after posterior capsule rupture in an animal model

OBJECTIVE

To develop a new technique to visualize vitreous body prolapsed in the anterior chamber using 11-deoxycortisol.

STUDY DESIGN

Experimental study.

METHODS

An animal model of posterior capsule rupture was developed to investigate the usefulness of 11-deoxycortisol, a precursor of cortisol without steroid activity. After the intentional creation of posterior capsule rupture, the suspension of 11-deoxycortisol was injected into the anterior chamber of rabbit eyes. After gentle irrigation and aspiration, the vitreous body that had prolapsed into the anterior chamber was removed using an anterior vitrectomy cutter. To investigate the safety of 11-deoxycortisol, the biomicroscopic appearance, intraocular pressure (IOP), corneal endothelial count, and microstructure of the corneal endothelium were examined in the rabbits that received injections of 11-deoxycortisol in the anterior chamber.

RESULTS

In our posterior capsule rupture model, the vitreous in the anterior chamber became clearly visible, with 11-deoxycortisol showing white particles entrapped on its surface. The injection of 11-deoxycortisol facilitated the complete removal of the vitreous body from the anterior chamber. In intact rabbit eyes, most of the injected 11-deoxycortisol had disappeared from the anterior chamber by 12 hours after injection. The injection of 11-deoxycortisol had no effect on IOP, corneal endothelial density, or the microstructure of the corneal endothelium.

CONCLUSIONS

The injection of 11-deoxycortisol in the anterior chamber is useful in visualizing the vitreous body and has no significant side effects. This technique might reduce the intraoperative and postoperative complications of anterior vitrectomy after posterior capsule rupture.

Ophthalmic drug discovery

Millions of people suffer from a wide variety of ocular diseases, many of which lead to irreversible blindness. The leading causes of irreversible blindness in the elderly--age-related macular degeneration and glaucoma--will continue to effect more individuals as the worldwide population continues to age. Although there are therapies for treating glaucoma, as well as ongoing clinical trials of treatments for age-related macular degeneration, there still is a great need for more efficacious treatments that halt or even reverse ocular diseases. The eye has special attributes that allow local drug delivery and non-invasive clinical assessment of disease, but it is also a highly complex and unique organ, which makes understanding disease pathogenesis and ocular drug discovery challenging. As we learn more about the cellular mechanisms involved in age-related macular degeneration and glaucoma, potentially, new drug targets will emerge. This review provides insight into some of the new approaches to therapy.

Induced acute ocular hypertension: mode of retinal cell degeneration

The effects of experimental hypertension on retinal cells were studied. Evaluation was made of IOP levels and degree of cell damage by cytochemical and DNA analysis, and degeneration modes: necrosis and apoptosis.

Nerve growth factor (NGF) reduces and NGF antibody exacerbates retinal damage induced in rabbit by experimental ocular hypertension

BACKGROUND

It has been shown that intravitreal injection of NGF inhibits ganglion cell degeneration after optic nerve transection and ischemic injury. The aim of our study was to investigate the presence of NGF in aqueous humor and its involvement in retinal damage during ocular hypertension.

METHODS

We used an experimental model of ocular hypertension in rabbit. Before treatment and 4, 10 and 15 days after induction of hypertension, we evaluated histological retinal damage and NGF levels in aqueous humor using an immunoenzymatic assay. Polyclonal anti-NGF antibodies were injected intravitreally into one eye of each rabbit (n = 6), and the animals were killed after 4 days of hypertension. Another group of rabbits (n = 12) was injected retro-ocularly with NGF and killed after 10 or 15 days of treatment for histologic evaluation of the retina.

RESULTS

Our data show that experimental ocular hypertension in adult rabbits induces retinal damage and enhances local NGF levels. The highest NGF value was found after 4 days of intraocular hypertension: high levels persisted, though to a lesser extent, for up to 15 days. Histological examination revealed that the number of retinal ganglion cells (RGC) remained unchanged during the first 4 days but decreased at 10 days. These studies also showed that retro-ocular administration of NGF reduced RGC loss, whereas intraocular injection of NGF antibodies, which inhibited the endogenous NGF, exacerbated the retinal insult.

CONCLUSION

These findings demonstrate a protective effect of NGF on RGC damaged by ocular hypertension and prompt further investigations to evaluate a possible therapeutic use of NGF to retard RGC death in humans.

Histopathological evaluation of retinal damage during intraocular hypertension in rabbit: involvement of ganglion cells and nerve fiber layer

BACKGROUND

Current clinical tests do not detect glaucomatous signs until the onset of substantial retinal damage. Therefore animal models are required to investigate the very early histopathological alterations in glaucoma disease. We used an experimental model of intraocular hypertension to compare early changes in retinal ganglion cell (RGC) density with the thickness of the nerve fiber layer (NFL).

METHODS

Methylcellulose 2% was injected into the anterior chamber of 18 eyes of 18 New Zealand albino rabbits. Intraocular pressure was measured 6 h after the injection and thenceforth once a day using a Shiötz tonometer. Histopathological analysis was performed on days 4, 10, and 15 following the induction of hypertension (six eyes for each group). Sections from the upper temporal retina were stained with hematoxylin-eosin and immunohistochemically using a polyclonal antibody PGP 9.5 to identify RGC. An image analysis system was used to evaluate the RGC and the thickness of the NFL.

RESULTS

We observed a significant increase in intraocular pressure until the end of the experiment. Histological analysis showed, after 10 days of ocular hypertension, a significant decrease in RGC density (P < 0.05) and a significant increase (P < 0.05) in glial cell density. We found a significant correlation between RGC loss and cell area at 4 days (P < 0.01; Cc = 0.86) and at 10 days (P < 0.002; Cc = 0.91) of intraocular hypertension. We did not observe a significant decrease in the NFL thickness until 10 days of intraocular hypertension.

CONCLUSIONS

Our study confirms the size-dependent RGC loss during intraocular hypertension and shows no early decrease in NFL thickness.