Rho-associated coiled-coil containing protein kinase (ROCK) is a serine/threonine kinase that acts downstream of the small GTPase RhoA2). Two isoforms, ROCK1 and ROCK2, have been identified, sharing 92% homology in their kinase domains2). They are expressed in the corneal epithelium, stroma, and endothelium, and are involved in cytoskeletal reorganization, cell proliferation, migration, adhesion, and apoptosis regulation2).
Corneal endothelial cells (CECs) express ROCK, and ROCK inhibitors (RKIs) promote wound healing and regeneration of CECs3)4). Due to this property, RKIs have attracted attention as a promising pharmacological approach for corneal endothelial diseases1).
The RKIs used clinically are ripasudil and netarsudil. Both were originally developed as glaucoma treatments, but their effect of promoting corneal endothelial regeneration has been confirmed, expanding their application to corneal diseases1)2).
Drug
Formulation/Dosage
Approved Regions
Ripasudil
0.4% ophthalmic solution, twice daily
Japan, China
Netarsudil
0.02% ophthalmic solution, once daily
United States and Europe
Y-27632
Research reagent
Not approved
Y-27632 is the most widely used research RKI and plays an important role in cultured CEC technology and preclinical studies3).
QWhy are glaucoma drugs also effective for corneal diseases?
A
ROCK inhibitors were developed as glaucoma treatments that lower intraocular pressure by improving the permeability of the trabecular meshwork and Schlemm’s canal. However, ROCK is also expressed in corneal endothelial cells, and its inhibition has been found to promote CEC proliferation, migration, and adhesion, and suppress apoptosis3). Through the different mechanism of corneal endothelial regeneration, they are also applied to corneal diseases.
Fuchs endothelial corneal dystrophy (FECD): The most studied indication. Combined with Descemet stripping only (DSO), it has been reported to promote corneal clearance, reduce central corneal thickness, and improve visual acuity1).
Bullous keratopathy (PBK): Intracameral injection of cultured CECs plus ROCK inhibitor achieved CEC density ≥1,000 cells/mm² at 24 weeks postoperatively in 10 of 11 cases4).
CEC protection after cataract surgery: In cataract surgery for FECD patients, perioperative use of RKI has been reported to maintain corneal endothelial cell density (ECD) and reduce corneal thickness1)
Enhanced recovery after corneal transplantation: May promote endothelial cell regeneration after corneal transplantation2)
The following clinical changes are observed after ROCK inhibitor administration.
Corneal clearance: In the DSO + ripasudil combination group, corneal clearance was achieved in 22 of 23 cases. Compared to the DSO alone group, clearance was achieved faster, with significant improvement in best-corrected visual acuity (BCVA) and significant reduction in central corneal thickness (CCT)1)
Morphological changes in corneal endothelial cells: Transient cell border blurring and pseudo-guttae are observed after ripasudil administration. This is thought to be caused by protrusion formation due to decreased actomyosin contraction3)
Side effect findings: Conjunctival hyperemia is the most common. Cornea verticillata is characteristic of netarsudil2)
QIn which patients can ROCK inhibitors be expected to be effective?
A
ROCK inhibitors are considered most effective in cases where a reservoir of healthy endothelial cells remains in the peripheral cornea1). They are useful when combined with DSO for early to moderate FECD, or for protecting the corneal endothelium during cataract surgery. In cases of severe endothelial cell loss, corneal transplantation remains the definitive treatment1).
When RhoA becomes GTP-bound (active), it binds to the Rho-binding domain of ROCK, activating ROCK through a conformational change2). Activated ROCK directly phosphorylates myosin light chain (MLC) and inhibits myosin phosphatase by phosphorylating myosin phosphatase target subunit 1 (MYPT1)2). This enhances cell contractility, stress fiber formation, and focal adhesion.
ROCK also activates LIM kinase, which phosphorylates and inactivates cofilin, inhibiting actin filament depolymerization2).
Corneal epithelium: ROCK inhibition reduces actomyosin tension, promoting cell spreading and migration. Wound closure is accelerated2)
Corneal stroma: Suppresses TGF-β-induced differentiation of keratocytes into myofibroblasts. Y-27632 reduced α-SMA-positive cells from 4% to 0.3%2). Inhibits fibrotic scar formation
Corneal endothelium: Under physiological conditions, contributes to cytoskeletal stabilization and barrier function maintenance. Under oxidative stress or inflammation, ROCK hyperactivation causes cell contraction, junctional disruption, and apoptosis2). RKI promotes G1/S phase progression by increasing cyclin D and suppressing p27Kip1 phosphorylation, inducing CEC proliferation3)
ROCK promotes cytokine production and immune cell recruitment via NF-κB. RKI inhibits this pathway, reducing inflammation and fibrosis2). In animal models, it has also been reported to suppress corneal neovascularization2). In corneal transplant models, it reduced rejection by increasing regulatory T cells and suppressing Th17 responses2).
Characteristics: Non-selective ROCK1/ROCK2 inhibitor. Approved in Japan in 2014 for glaucoma and ocular hypertension3). Rapid corneal penetration and approximately 6-hour intra-corneal effect2)
Corneal application: Used to promote corneal clearance after DSO. Patients treated with ripasudil showed higher ECD at 3, 6, and 12 months post-DSO compared to the control group1)
Netarsudil (Rhopressa®)
Formulation: 0.02% ophthalmic solution. Administered once daily
Characteristics: Dual-action drug with ROCK1/ROCK2 inhibition and norepinephrine transporter (NET) inhibition2). Approved for glaucoma treatment in the US and Europe
Clinical trials: In a placebo-controlled double-blind study of FECD patients, a significant reduction in central corneal thickness and a significant improvement in BCVA were reported1).
Conjunctival hyperemia: The most common side effect. Occurs in 50–55% of patients with netarsudil and 60–65% with ripasudil2). Usually mild and transient, diminishing with continued use.
Blepharitis: More common with ripasudil. Develops in about 25% of patients at 12 months and is the most common reason for discontinuation2). Atopic predisposition is a risk factor.
Cornea verticillata: Occurs in about 20% of patients with netarsudil2). These are light brown, whorl-like epithelial deposits that do not cause vision loss and resolve after discontinuation. Not reported with ripasudil.
Honeycomb keratopathy: Reported with both drugs1)5). More likely to occur in cases of corneal decompensation. Usually reversible after drug discontinuation.
QAre there any side effects of ROCK inhibitors that affect vision?
A
Conjunctival hyperemia is transient and does not affect vision. Cornea verticillata, seen in about 20% of netarsudil users, does not cause vision loss2). Honeycomb keratopathy can occur in patients with a history of corneal decompensation but is usually reversible after drug discontinuation1). Severe visual impairment is rare with any of these.
Descemet Stripping Only (DSO) is a procedure that removes the central Descemet membrane, expecting endothelial regeneration via migration of healthy CECs from the periphery3). Combination with ROCK inhibitors promotes CEC migration and accelerates corneal clearance1).
In a study of DSO + ROCK inhibitor combination therapy, corneal clearance was achieved in 22 of 23 eyes in the DSO + ripasudil group1). Compared to the DSO-only group (9 eyes), the RKI group achieved clearance significantly faster, with significant improvements in BCVA and central corneal thickness1).
In a groundbreaking clinical trial by Kinoshita et al., cell therapy was performed by injecting cultured human CECs supplemented with Y-27632 into the anterior chamber4). In 11 patients with bullous keratopathy, CEC density reached ≥1,000 cells/mm² in 10 cases at 24 weeks postoperatively 4). Corneal edema improved to ≤630 μm in 10 of 11 cases 4). Good corneal clarity was maintained without immune reactions during 2-year follow-up 3).
Perioperative Use in Cataract Surgery for FECD Patients
Cataract surgery in FECD patients is a high-risk procedure for corneal endothelial damage, with 70% requiring subsequent corneal transplantation 1). Perioperative administration of RKI has been reported to improve ECD and reduce central corneal thickness 1). In a randomized trial of 48 eyes, the RKI group showed significant differences in ECD and central corneal thickness compared to the control group 1).
QCan ROCK inhibitors avoid corneal transplantation?
A
In patients with early to moderate FECD, combined DSO and ROCK inhibitor therapy can achieve corneal clearance, delaying or avoiding corneal transplantation in some cases 1). However, for advanced cases with severe CEC loss, corneal transplantation (EK) remains the definitive treatment 1). ROCK inhibitors are also a key component of cell therapy aimed at addressing donor cornea shortages 4).
In FECD corneal endothelium, ROCK signaling is hyperactivated, leading to increased cell contractility and reduced proliferation and migration capacity 1). Oxidative stress, mitochondrial dysfunction, and abnormal protein/RNA processing are involved, progressing to caspase-3-dependent apoptosis1)2).
Increased ROCK activity also contributes to extracellular matrix (ECM) abnormalities. FECD endothelial cells abnormally secrete matrix proteins such as collagen, which deposit as guttae on Descemet’s membrane 1). ROCK inhibition can suppress this pathological ECM production 1).
Endothelial Regeneration Mechanism by ROCK Inhibition
RKIs relax actomyosin contraction and promote cell spreading. Upregulation of cyclin D activates G1/S phase progression, inducing CEC proliferation 3). Ripasudil stimulates Rac1 and upregulates Snail and Vimentin, markedly enhancing CEC motility 2). This converts the normally quiescent corneal endothelium into a reparative phenotype 2).
Y-27632 contributed to the establishment of an animal-derived pathogen-free CEC culture system 3). Addition of RKI increases CEC yield by 1.96- to 3.36-fold 3). Enhanced cell-substrate adhesion, proliferation promotion, improved survival, and better cryopreservation outcomes have been confirmed 3).
The application of ROCK inhibitors to corneal diseases is rapidly expanding. In addition to ripasudil and netarsudil, novel ROCK inhibitors with higher selectivity (e.g., ITRI-E-212, NRL-1049) are under development 2). ROCK2-selective inhibitors are expected to improve tissue specificity and reduce off-target effects 2).
Development of sustained-release formulations (nanocarriers, in situ gelling systems) is also progressing, enabling reduced dosing frequency and long-term application for chronic corneal diseases 2).
Cell therapy using cultured CECs plus ROCK inhibitors is positioned as an innovative approach to overcome the global shortage of donor corneas 3)4). Multiple clinical trials are ongoing, and long-term safety and efficacy data are awaited 1).
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Leong EYX, Ding J, Wu D, Lim BXH, Ang A, Wong E, Morlet N, Mehta JS, Lim CHL. A Comprehensive Review of the Role of Rho-Kinase Inhibitors in Corneal Diseases. Life. 2025;15(8):1283.
Tone SO, Kocaba V, Böhm M, Wyber A, Kinoshita S, Jurkunas UV. Fuchs endothelial corneal dystrophy: A review. Prog Retin Eye Res. 2021;80:100898.
Patel SV. Graft survival and endothelial outcomes in the new era of endothelial keratoplasty. Annu Rev Vis Sci. 2020;6:255-267.
American Academy of Ophthalmology. Corneal Edema and Opacification Preferred Practice Pattern. Ophthalmology. 2019;126(1):P216-P285.
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