Targeting Very Low IOPs: Achieving Single‑Digit Pressures Safely

Targeting Very Low IOPs: Achieving Single‑Digit Pressures Safely

This audio article is from VisualFieldTest.com [https://visualfieldtest.com]. Read the full article here: https://visualfieldtest.com/en/targeting-very-low-iops-achieving-single-digit-pressures-safely [https://visualfieldtest.com/en/targeting-very-low-iops-achieving-single-digit-pressures-safely] Test your visual field online: https://visualfieldtest.com [https://visualfieldtest.com] Support the show so new episodes keep coming: https://www.buzzsprout.com/2563091/support [https://www.buzzsprout.com/2563091/support] Excerpt: Introduction In advanced glaucoma, doctors often set very low target pressures (often 10 mmHg or lower) to protect remaining vision () (). “Single-digit” pressures mean an eye pressure under 10 mmHg (normal pressure is 12–22 mmHg). Achieving such low pressure can slow or stop glaucoma damage, but requires strong surgery. This article explains the main surgical approaches—trabeculectomy with antimetabolites, tube shunts with flow restriction, and cyclodestruction—along with how doctors balance the benefits against risks like hypotony (too-low pressure) and vision problems. We will also cover what factors predict a surgery’s success or failure, how surgeons fine-tune eye pressure after surgery, and how to spot and treat complications early. Surgical Strategies to Achieve Low IOP Trabeculectomy with Tailored Antimetabolites Trabeculectomy (filtering surgery) creates a new drainage path for fluid (aqueous humor) to leave the eye under the eyelid. Surgeons remove a small piece of the eye’s internal drainage tissue (trabecular meshwork) and make a tiny hole into the white of the eye. A flap of tissue is sewn loosely over this opening so fluid can seep out gradually. As the fluid drains, it forms a bubble or “bleb” under the conjunctiva (the transparent tissue covering the eye). To keep this new drainage channel open long-term, surgeons often use antimetabolites (anti-scarring drugs) like mitomycin C (MMC) or 5-fluorouracil (5-FU) at the time of surgery. These drugs slow down healing so scar tissue doesn’t seal the flap shut. By carefully choosing the dose and duration of MMC, doctors can tailor how much drainage occurs. Stronger or longer MMC treatment generally increases the chance of a very low pressure, but also raises the risk of over-drainage. For example, using a high concentration of MMC (0.4 mg/ml for 4 minutes) led to hypotony (dangerously low pressure) in about 13% of cases (), whereas a lower dose (0.2 mg/ml) in a similar setting reduced that risk to 3–5% (). Modern techniques (such as injecting MMC under the conjunctiva instead of placing sponges) can achieve low pressures without excessively high hypotony rates (). Key points about trabeculectomy: It can often achieve mid-to-low single-digit pressures, especially in experienced hands () (). Surgeons use antimetabolites (usually MMC) to prevent scarring. Tuning the concentration and time of application helps find the balance between pressure lowering and safety (). The surgery can include adjustable or releasable sutures in the scleral flap. This means sutures (stitches) can be loosened or removed after surgery to increase drainage if IOP is still high, or they can be partially cut with a laser (suture lysis) if pressure is too low () (). Tube Shunts with Flow Restriction Glaucoma drainage devices (tube shunts) are small implants comprising a drainage tube and a plate. The tube is placed into the front chamber of the eye, and the plate sits under the conjunctiva on the outside. Fluid flows through the tube into a reservoir (the plate) where it is absorbed by surrounding tissues. Tube shunts are often used when previous surgeries have failed or in severe secondary glaucomas, but they can also achieve very low pressures when carefully managed. There are two main types of shunts: Valved shunts (e.g., Ahmed valve) have a built-in mechanism that partially blocks flow when pressure is low. This means they limit how low the pressure can drop automatically. Ahmed valves typically control pressure into the mid-teens. They often still require glaucoma drops after surgery. Because of the valve, deep hypotony is rare (), but extreme low targets (<10 mmHg) often need additional medications or procedures. Non-valved shunts (e.g., Baerveldt, Molteno) have no built-in valve, so by default they would drain too much fluid at first. To prevent early hypotony, surgeons temporarily occlude these tubes. The standard method is to tie (ligate) the tube shut with an absorbable suture (like 6-0 or 7-0 Vicryl) around the outside of the tube. Some also place an internal stent (a thick nylon thread called Supramid®) inside the tube. As time passes (weeks to months), the ligature dissolves or the stent is removed, gradually allowing fluid out. This staged approach yields very low pressures once the eye has formed a capsule around the plate. Flow restriction techniques for tube shunts: External ligature: Tying the tube with a dissolvable suture (typically Vicryl) prevents flow for the first 4–6 weeks until the ligature softens. Some surgeons leave multiple fine sutures inside or outside that can be cut with a laser in clinic to increase flow gradually later (). Internal stent: A nylon or prolene suture (3-0 “Supramid”) is placed inside the tube lumen. This blocks most flow but can be left protruding so it can be pulled out or lasered when needed (). Fenestrations: Some surgeons create tiny slits (“Sherwood slits”) in the tube before it enters the eye. These allow a small amount of fluid to bypass the ligature early on. Because non-valved shunts ultimately allow higher flow (once fully open), they can reach lower pressures than valves, but they require careful follow-up to adjust flow. For example, one technique is to tie a Baerveldt with a loose nylon suture (10-0) that provides just ~10% occlusion on top of the main ligature. In clinic, the physician can then use a laser to cut one nylon suture at a time and “stage” the drop in pressure (). Key points about tube shunts: Valved devices (Ahmed) limit extra-low pressures but are easier to control; they often result in moderate pressure (high-teens) and usually need glaucoma drops after surgery (). Non-valved devices (Baerveldt/Molteno) can achieve very low single-digit pressures after the occluding ligature dissolves, but require temporary blocking to keep pressure safe early on () (). Post-surgical adjustments (cutting sutures, pulling stents) allow fine-tuning of IOP without major surgery. Adjunctive Cyclodestruction Cyclodestructive procedures use energy (laser or ultrasound) to partially destroy the ciliary body – the tissue that produces aqueous fluid. By reducing fluid production, these treatments help lower eye pressure. Cyclodestruction is generally used in advanced, refractory glaucoma or when other surgeries have failed or are not possible. Newer methods (like micropulse cyclophotocoagulation) aim to reduce side effects by delivering short, repeated laser pulses that heat the tissue gently (). Common cyclodestructive techniques include: Transscleral cyclodiode laser: A diode laser probe is applied on the white of the eye (sclera) over the ciliary body. It delivers burns through the sclera, shrinking fluid-producing cells (). Patients often get topical or general anesthesia for comfort. Micropulse cyclophotocoagulation: Delivers the same diode laser energy in very brief pulses, allowing the tissue to cool between bursts. This tends to cause less inflammation and pain () (). Endoscopic cyclophotocoagulation (ECP): Performed during cataract or other eye surgery, a tiny camera and laser are inserted into the eye via a small incision to directly target ciliary processes. Cyclodestruction is less predictable and generally less powerful than filtration surgery. It often lowers IOP by 20–30% on average, and is not usually enough to reach very low single digits by itself, but it can supplement other treatments. For eyes with remaining vision, doctors typically use conservative settings or micropulse to balance efficacy and safety. Key points about cyclodestruction: It is a non-incisional approach that “turns down the tap” by reducing fluid production () (). Micropulse methods cause less inflammation and usually fewer complications like pain or damage than traditional continuous-wave cyclodiode () (). Common side effects include inflammation (iritis) and potential vision loss if overtreatment occurs. Severe complications (retinal detachment, vision loss, or even phthisis) are rare with modern protocols, especially micropulse. Nonetheless, cyclodestruction is often reserved for eyes where vision is already limited or other surgeries have failed. Balancing Safety, Risks, and Follow-up Lowering eye pressure to single digits can protect vision in progressing glaucoma, but it also raises the chances of complications. Each procedure has trade-offs: Trabeculectomy: Can achieve low IOP without long-term implants, but it carries risks of overfiltration. Wounds can leak, and blebs can become too thin. Hypotony (too low pressure) after trabeculectomy can cause hypotony maculopathy – retinal folds and distorted vision (). There is also a lifelong risk of bleb-related infection (blebitis or endophthalmitis) if bacteria enter the eye through the bleb. On the plus side, trabeculectomy often achieves the lowest pressures of all procedures, especially with MMC (). Tube shunts: Generally have a safer early postoperative course regarding hypotony, especially valved implants. They also avoid an external bleb (so no bleb infection, though tubes have other risks like corneal touch or tube blockage). Non-valved shunts, once open, can still over-drain, but the staged occlusion techniques help prevent catastrophic hypotony early (). Support the show [https://www.buzzsprout.com/2563091/support]

SLT’s Evolving Role Relative to MIGS and Surgery

This audio article is from VisualFieldTest.com [https://visualfieldtest.com]. Read the full article here: https://visualfieldtest.com/en/slt-s-evolving-role-relative-to-migs-and-surgery [https://visualfieldtest.com/en/slt-s-evolving-role-relative-to-migs-and-surgery] Test your visual field online: https://visualfieldtest.com [https://visualfieldtest.com] Support the show so new episodes keep coming: https://www.buzzsprout.com/2563091/support [https://www.buzzsprout.com/2563091/support] Excerpt: Selective Laser Trabeculoplasty (SLT) in Modern Glaucoma Care Glaucoma treatment has evolved beyond just daily eye drops or major surgery. Selective laser trabeculoplasty (SLT) is a gentle office laser procedure that helps lower eye pressure by improving fluid drainage through the eye’s natural pathway. In recent years, SLT’s role has grown – sometimes used as an initial therapy, other times added later – especially alongside newer minimally invasive glaucoma surgeries (MIGS). Patient-friendly studies now suggest SLT can safely reduce or delay the need for medications and surgery. For example, a large trial (the LiGHT study) found that when open-angle glaucoma patients started treatment with SLT instead of drops, 74% of them remained off all medications three years later and none needed incisional surgery (). Leading eye care organizations (like NICE in the UK and the American Glaucoma Society) now list SLT as an option for first-line treatment, recognizing its benefit in early glaucoma care (). SLT as Primary or Adjunct Therapy SLT is often recommended either before starting drops or after medications alone can’t reach the target pressure. Being “selective,” the laser targets pigment cells in the drainage meshwork without scarring it, so it leaves the drainage pathway intact. As a result, SLT can be repeated if needed (). Per the Glaucoma Research Foundation, a single SLT session typically lowers pressure for about 2–3 years (often longer), and then can be repeated (). Many patients on multiple eye drops can do very well with SLT: it often allows them to reduce or stop medications. In contrast, MIGS procedures (such as tiny stents or implants like the iStent or Hydrus) are newer surgical methods done in the operating room, often together with cataract surgery. MIGS also aim to drop pressure or cut down medications, and are especially used in mild-to-moderate glaucoma. For example, one study found that combining a Hydrus microstent with cataract surgery gave the same IOP drop as SLT alone, but allowed many more patients to go medication-free (47% versus only 4% with SLT) (). However, that MIGS group did have a few more short-term issues (temporary blurred vision or IOP spikes) that weren’t seen in the SLT group (). In practice, doctors may choose MIGS when slightly lower pressures are needed than SLT can usually achieve, or when a patient is already getting cataract surgery. MIGS generally have a good safety profile and modest pressure drops (), filling a gap between simple drops/laser and major glaucoma surgery. SLT can also be used after a MIGS or vice versa. Notably, SLT still helps even if a stent is already in place. One study showed that glaucoma patients who had an iStent implant and then received SLT got about the same eye-pressure reduction as others – but importantly, the previous stent group ended up on fewer medications afterwards (). (This suggests SLT adds benefit in terms of med reduction even after MIGS.) In all cases, SLT is a quick outpatient procedure and may be tried first in suitable patients because it has minimal downsides. If it does not achieve the needed pressure, doctors can then consider stepping up to MIGS or traditional surgery. Durability and Retreatment SLT’s effects wear off over time. In general, about half to three-quarters of eyes have successful pressure control at one year, but many lose enough effect by 3–5 years that retreatment is needed. A review of studies reported SLT success rates ranging roughly 45–87% at 1 year, falling to only ~25% by five years (). In practice, nearly 44–45% of eyes in a 3-year study eventually needed a second SLT treatment (). Fortunately, SLT is repeatable because it does not scar the meshwork. A repeated SLT (often covering 360° of the angle) can regain pressure control and typically gives another 1–2 years of effect (). However, each time tends to give a slightly smaller drop, so the benefit diminishes with more repeats (). Several factors predict how well SLT will work for a patient. The baseline eye pressure is the strongest predictor: patients with higher starting pressures tend to get bigger pressure drops and higher success rates, simply because there’s more to reduce (). In fact, eyes with very low pressure to start (such as normal-tension glaucoma) may see little benefit at all (). Other features like pigment in the drainage angle or pseudoexfoliation may slightly alter response, but results are quite individual (). Age, race, or severity do not strongly predict outcomes beyond their effect on baseline IOP. In short, entering SLT with a pressure well above target usually means a better absolute drop, while eyes already very low may need more aggressive treatment. When monitoring SLT, doctors watch for pressure creep. If target pressure is lost or disease progresses (for example, worsening visual field loss), it’s time to step up therapy. Modern guidelines emphasize not waiting for a very high pressure before acting: any sign of glaucoma worsening warrants additional treatment, whether that is repeating SLT, adding MIGS, or moving to incisional surgery (). Importantly, data show that patients started on SLT often avoid surgeries longer: in the LiGHT trial, none of the SLT-first patients needed glaucoma surgery by year 3 (versus several who started on drops) (). Safety and Side Effects SLT is exceptionally safe for patients. It is done in the clinic under topical anesthesia and causes minimal discomfort. The most common side effects are mild and short-lived. Nearly all patients have some mild eye inflammation (seen as a few cells in the front chamber) for a day or two after the laser, which usually helps the pressure drop before it resolves (). Many patients also take a few anti-inflammatory drops for a week. Some people might notice a bit of redness or eye irritation right after. A known effect is a transient pressure spike: in roughly 20–30% of eyes, the IOP temporarily rises by about 5 mmHg or more in the first few hours (especially if a lot of angle pigment is present) (). This spike usually takes a day to 48 hours to go away, and doctors often give a preventive drop (like brimonidine or acetazolamide) to blunt it. Rarely, a spike can be higher and take a few days to settle. Serious complications from SLT are very rare. There have been isolated reports of extended inflammation or even cystoid macular swelling, especially in patients with other eye problems, but these are exceptional cases. By contrast, incisional surgeries (trabeculectomy or tube shunts) carry risks like infection, chronic hypotony, or bleb complications. MIGS are generally safer than classic surgery, but they still involve incisions inside the eye and have their own issues (transient blood or fluid in the eye, needling revisions of stents, etc.). In one head-to-head comparison, a Hydrus MIGS implant and SLT gave similar IOP-lowering, but the MIGS eyes had a few more side effects (temporary blurred vision or early pressure spikes) that did not happen with SLT (). In summary, SLT’s advantages are its simplicity and safety: it carries none of the risks of a later trabeculectomy (no bleb to worry about) and can be done as often as needed. Its limitations are that it typically cannot achieve very low “target” pressures (often only into the mid-teens) and it may need repeating. MIGS falls in between: it is more invasive, so has somewhat more risk, but it can sometimes reach a bit lower pressure and substantially reduce medications (). The choice between them depends on how much pressure lowering is needed and patient preferences. Sequencing SLT and MIGS: Proposed Treatment Pathways The best order of treatments depends on disease severity, resource goals, and patient wishes. Here are evidence-based approaches to lining them up: Early (mild) glaucoma: Consider SLT first to delay drops. A patient with newly diagnosed mild open-angle glaucoma and a target pressure in the mid-teens can often do well with one SLT treatment (). If the patient is already undergoing cataract surgery, a surgeon might instead or additionally place a MIGS stent during the same operation (for example, an iStent or Hydrus). If SLT is used and later pressure rises, re-treat SLT once or twice more before moving on. If additional lowering is needed, MIGS procedures or adding a single medication may be the next step. Several guidelines now endorse using laser early exactly for these patients. Moderate glaucoma or patients on multiple drops: Many surgeons consider MIGS (with cataract if indicated) at this stage, especially if target IOP is not reached by medicines and lens changes allow. For example, an eye needing to go from 18 to 15 mmHg might handle SLT, but an eye needing 12–13 mmHg may require a stent or micro-shunt. SLT can still be done either before or after MIGS to shave off a few more points or reduce meds. Indeed, even after an unsuccessful MIGS, applying SLT later can add some benefit (). If MIGS itself is insufficient, the patient may ultimately need a full trabeculectomy or tube shunt, especially if disease is progressing. Advanced glaucoma: Here the target pressure is very low (often mid-teens or below). Neither SLT nor most MIGS will reliably hit those levels. In such cases, many doctors proceed directly to tra Support the show [https://www.buzzsprout.com/2563091/support]

Trabeculectomy vs Tube Shunts in the Modern Era: Long-Term Safety and Durability

This audio article is from VisualFieldTest.com [https://visualfieldtest.com]. Read the full article here: https://visualfieldtest.com/en/trabeculectomy-vs-tube-shunts-in-the-modern-era-long-term-safety-and-durability [https://visualfieldtest.com/en/trabeculectomy-vs-tube-shunts-in-the-modern-era-long-term-safety-and-durability] Test your visual field online: https://visualfieldtest.com [https://visualfieldtest.com] Support the show so new episodes keep coming: https://www.buzzsprout.com/2563091/support [https://www.buzzsprout.com/2563091/support] Excerpt: Trabeculectomy vs Tube Shunts in the Modern Era: Long-Term Safety and Durability Glaucoma is often treated surgically by creating a new pathway for fluid to drain out of the eye. Two main approaches exist: trabeculectomy (making a new small flap/“bleb” in the eye’s wall) and tube shunt implants (silicone tubes that divert fluid to a distant reservoir). Over the past decades, doctors have shifted increasingly toward tube shunts, especially in complex cases (). However, patients and surgeons still debate which is safer and more durable in the long run. Large clinical trials and patient series have compared these surgeries. In general, tubes tend to be more reliable at keeping pressure from jumping up, whereas trabeculectomies often achieve lower pressure with less medication. Each method has different risks: for instance, trabeculectomy blebs can leak or get infected, while tubes can cause double vision or corneal problems. Importantly, how the surgery is done – the dose of antifibrotic medication, suture techniques, and careful follow-up – can greatly affect outcomes. This article will summarize the key long-term findings from major studies, detail typical complications, and explain how technique and postoperative care influence safety. We will also offer guidance on which procedure may be best suited for eyes needing very low target pressure or eyes with “refractory” glaucoma (e.g. after failed prior surgery). Comparing Long-Term Results of Trabeculectomy and Tube Shunts Tube versus Trabeculectomy (TVT) Study – Eyes with Prior Surgery An important trial known as the Tube Versus Trabeculectomy (TVT) Study looked at patients who had already had cataract or glaucoma surgery that failed () (). Here, one group received a large Baerveldt tube implant (350 mm² endplate), and the other had a trabeculectomy with mitomycin C (MMC). In the first year, both surgeries lowered eye pressure (intraocular pressure, IOP) similarly. However, tubes were more likely to maintain good pressure control long-term and needed fewer repeat surgeries. For example, at 1 year the failure rate (by strict criteria including high IOP, very low IOP, or need for more surgery) was significantly lower with tubes (3.9%) than with trabeculectomy (13.5%) (). In practical terms, tube patients were less likely to need another glaucoma surgery or to have dangerously low pressure. Both groups lost vision at similar rates (about 32–33% lost ≥2 lines of vision, usually due to non-surgical causes) (). Over longer follow-up, the advantage for tubes continued. At 3 years, IOPs were effectively the same (around 13 mmHg on average) between the groups, and use of glaucoma medicines was similar (). But tubes failed less often: the 3-year chance of failure was 15% with tube versus 31% with trabeculectomy (a statistically significant difference) (). Postoperative complications (mostly mild and transient) were also more common after trabeculectomy. In the first year 60% of trabeculectomy patients had some complication versus 39% with a tube (). Notably though, severe complications harming vision occurred at about the same rate (~20–27%) in both groups (). Key findings of the TVT Studies can thus be summarized as: Both surgeries significantly lowered IOP long-term, but tubes required slightly more medical therapy initially (). Tube shunts had higher success rates (fewer failures and reoperations) in eyes with prior surgery (). Trabeculectomy achieved lower IOP without meds, but had more postoperative problems like bleb leaks (). Over 5 years, there was no clear winner for vision loss or glaucoma control – other factors like patient/doctor preference and follow-up patterns matter (). (For completeness, a more recent “Primary Tube vs Trabeculectomy (PTVT)” trial in eyes without prior surgery found somewhat different results. At 1 year in that trial, trabeculectomy with MMC actually had a higher success rate and lower IOP (mean 12.4 mmHg vs 13.8 mmHg) than tubes (). However, most serious complications occurred in the trabeculectomy group (7% vs 1% for tubes) (). This suggests that in eyes where healing is normal, trabeculectomy can give a lower pressure but may carry more risk. By contrast, in complex eyes (like in TVT), tubes had the edge.) Ahmed vs Baerveldt (Tube versus Tube) There have also been head-to-head trials comparing different types of tube shunts. The two most common are the Ahmed valve (flow-restricted device) and the Baerveldt plate (non-valved, larger plate). The Ahmed Versus Baerveldt (AVB) Study randomized hundreds of refractory glaucoma patients to one of these devices. At 3 years, both implants had similar pressure control (mean IOP ~15 mmHg) (), but Baerveldt eyes needed fewer medicines (1.1 vs 1.8 meds on average) (). More importantly, failure (defined as inadequate IOP or vision loss) was lower with the Baerveldt (34% failure) than Ahmed (51% failure) at 3 years (). The main difference was pressure: the Baerveldt produced lower IOP (mean ~14.4 mmHg) than the Ahmed (~15.7 mmHg), though this just missed statistical significance (P=0.09) (). However, hypotony (too-low pressure) was more of an issue with the Baerveldt: by 3 years, 6% of Baerveldt patients had a vision-threatening hypotony complication, whereas none of the Ahmed patients did (P=0.005) (). At 5 years (follow-up of the same study), the pattern was similar: Baerveldt eyes continued to have lower IOP (mean 13.6 vs 16.6 mmHg, P=0.001) and fewer medications (). Cumulative failure at 5 years was 40% for Baerveldt vs 53% for Ahmed (P=0.04) (). Again, hypotony was seen only in Baerveldt eyes (4% of patients) while none of the Ahmed eyes failed due to hypotony (). Overall: Both Ahmed and Baerveldt implants effectively lower IOP, but Baerveldt typically achieves slightly better long-term pressure and medication reduction (). Baerveldt has a small risk of hypotony, whereas the Ahmed valve’s built-in resistor prevents this (none in Ahmed group) (). Serious complication rates were similar (around 60–69% had some complication, mostly minor, in either group) (). In one analysis, Ahmed eyes had about twice the risk of needing reoperation compared to Baerveldt by 3 years (). (However, note that definitions and patient mix vary between studies.) Other analyses and systematic reviews generally confirm that large plates (Baerveldt or Molteno) yield lower pressures than valved devices (Ahmed) or trabeculectomy, at the cost of slightly higher early hypotony rate. Common Complications and How to Manage Them Both trabeculectomy and tube shunts can cause complications. Understanding these helps patients and doctors avoid or treat them early. Four important issues are hypotony maculopathy, bleb leaks/infections, diplopia (double vision), and corneal endothelial loss. Hypotony and Hypotony Maculopathy What it is: Hypotony means an abnormally low IOP (often ≤5 mmHg). When pressure is too low, the back of the eye can wrinkle and the optic nerve can swell, a situation called hypotony maculopathy. This can permanently damage vision if not recognized. Modern use of anti-scarring drugs (like MMC) in trabeculectomies has made hypotony maculopathy more common than in the old days (). How often it happens: In general, hypotony is more associated with trabeculectomy (especially with high MMC dose) than with valved tubes. CIGTS (a glaucoma study) found a 5-year hypotony risk of about 1.5% after trabeculectomy (). Tube shunts (Baerveldt or Ahmed) rarely cause persistent hypotony because tubes have restricted flow (Ahmed) or require flow ligation (Baerveldt is often tied off initially). In the AVB study above, 4% of Baerveldt eyes failed from hypotony at 5 years, while Ahmed had none (). Risk factors: Young, myopic males with pliable sclera and first-time filtering surgery are at highest risk (). High doses of MMC (longer time or higher concentration) make the bleb “thinner” and prone to over-drain. Early overfiltration (for example from too-loose sutures or a large drainage) is also a big factor. Prevention strategies: Surgeons take several precautions: Titrating MMC dose: Use the lowest effective exposure (often 0.2 mg/ml for 1–2 minutes) in primary cases. Very high MMC doses increase hypotony risk (). Careful flap suturing: Place tight sutures on the scleral flap so it doesn't over-drain. Adjustable or releasable sutures allow gradual loosening in clinic. Staged release: Delay full flow in tubes (e.g. Baerveldt tubes are ligated at surgery and only released later, often with ripcord or tie suture removal) to prevent a huge pressure drop when scarring has occurred around the plate. Safety-valve techniques: Some surgeons add small “vent” incisions or partial thickness flaps that slow flow if necessary (). Controlled suture lysis: If laser suture lysis is needed post-op, do it gradually to avoid a sudden pressure crash (). If hypotony does occur, treating it promptly is crucial (). For example, one can apply a pressure patch or bandage contact lens to close leaks, inject autologous blood or fibrin glue under the bleb, or even revise the flap surgically (adding sutures or conjunctival stitches) (). The goal is to raise IOP and allow the eye tissues to re-expand. A number of techniques like conjunctival Support the show [https://www.buzzsprout.com/2563091/support]

Do Orally Ingested Collagen Peptides Reach the Eye

This audio article is from VisualFieldTest.com [https://visualfieldtest.com]. Read the full article here: https://visualfieldtest.com/en/do-orally-ingested-collagen-peptides-reach-the-eye [https://visualfieldtest.com/en/do-orally-ingested-collagen-peptides-reach-the-eye] Test your visual field online: https://visualfieldtest.com [https://visualfieldtest.com] Support the show so new episodes keep coming: https://www.buzzsprout.com/2563091/support [https://www.buzzsprout.com/2563091/support] Excerpt: Do Oral Collagen Supplements Reach the Eye? Many people take hydrolyzed collagen (collagen broken into small pieces) to support their joints, skin, and even eye health. Collagen is a structural protein found in the skin, bones, cartilage – and the eye’s connective tissues (like the cornea and sclera). A key question is whether collagen fragments eaten by mouth can travel through the body’s blood and actually get into eye tissues. This article reviews what we know about how collagen peptides behave in the body (their “pharmacokinetics”), whether small collagen pieces can cross the blood-aqueous and blood-retinal barriers, and what evidence animal or human studies provide. We also suggest how future experiments could directly test for collagen peptides in eye fluids and tissues. How Collagen Peptides Enter the Blood When you swallow hydrolyzed collagen (often from supplements or certain foods), your digestive system breaks it into very short chains of amino acids – mainly dipeptides and tripeptides (two or three amino acids linked together). Two common collagen dipeptides are Proline-Hydroxyproline (Pro-Hyp) and Hydroxyproline-Glycine (Hyp-Gly). These small peptides are unusually resistant to digestion because their amino acids (proline and hydroxyproline) form a rigid ring structure. Studies in humans show that after eating collagen hydrolysate, these collagen-derived peptides do appear in the blood. For example, Virgilio et al. (2024) gave people a collagen supplement and found high blood levels of Pro-Hyp, Hyp-Gly, and related collagen peptides within 1–2 hours (). In fact, they reported that “all collagen products yielded relevant plasma concentrations of the investigated metabolites” (meaning collagen breakdown products) (). In practical terms, this means that when you ingest collagen hydrolysate, enzymes in the gut produce a mix of small peptides (and free amino acids), some of which enter the bloodstream intact. The peak blood levels of peptides like Pro-Hyp typically occur around 60–120 minutes after ingestion, according to multiple studies (). After peaking, these peptide levels fall over the next few hours. For instance, one study found that Pro-Hyp (which contains the common hydroxyproline, 4Hyp) returned to its baseline (undetectable) level by about 4 hours after ingestion (). In contrast, a more unusual collagen peptide (Gly-3Hyp-4Hyp, containing 3-hydroxyproline and 4-hydroxyproline) stayed at its peak blood concentration through around 4 hours due to exceptional stability (). In summary, collagen peptides appear in the blood quickly and then are cleared within a few hours () (). What Happens to Collagen Peptides in the Body Once in circulation, collagen peptides distribute to various tissues. Animal tracer studies using radio-labeled collagen fragments show that ingested collagen tends to accumulate in collagen-rich tissues. For example, Kawaguchi et al. (2012) gave rats an oral dose of radioactively labeled Pro-Hyp and found it widely distributed in the body after 30 minutes. The highest radioactivity was in the digestive tract (stomach and intestines, understandable as the site of absorption) and surprisingly also in skin and cartilage – tissues built of collagen (). Cells like skin fibroblasts, cartilage cells, bone cells, and others that normally respond to collagen peptides actually took up these labeled fragments (). This suggests that after absorption, collagen peptides can travel through blood to reach collagen-containing tissues. Another rat study found that collagen tripeptides like Gly-Pro-Hyp remained in the blood and deposited mainly in the kidney (for excretion) and skin for days after dosing (). Importantly, these animal studies did not examine the eye. They show that collagen fragments in blood can end up in tissues with high collagen content (bone, cartilage, skin), but eyes were not tested. This leaves a data gap on whether any of the orally derived collagen peptides reach the eye. The Eye’s Protective Barriers Before considering if collagen peptides reach the eye, it helps to understand the eye’s blood-barrier systems. The eye has two major “blood-ocular” barriers: Blood-Aqueous Barrier (BAB): This is at the front of the eye (between the blood and the fluid in the front chamber called the aqueous humor). It is formed by the lining of the iris and ciliary body. The BAB restricts entry of many substances from the bloodstream into the anterior chamber (). Blood-Retinal Barrier (BRB): This is at the back of the eye (between blood and the retina/vitreous). The BRB is formed by tight junctions in the retinal blood vessels (inner BRB) and by the retinal pigment epithelium (outer BRB). It severely limits movement of molecules from the blood into the retina (). These barriers block large molecules (like most proteins) and many drugs. Only small, lipid-soluble, or actively transported molecules cross easily. In fact, drug delivery reviews stress that the BRB’s limited permeability is a major challenge for systemic eye treatments (). Could collagen peptides cross these barriers? Collagen peptides are small (di- or tri-peptides), but they are hydrophilic, so they usually would not passively diffuse through these barriers. However, the body does have specialized peptide transporters. In the gut and kidneys, transporters PepT1 and PepT2 carry di- and tri-peptides. There is evidence that similar carriers exist on ocular barriers. Notably, Atluri et al. (2004) showed in rabbits that a model dipeptide (glycylsarcosine) injected into the blood did reach the vitreous, retina, and aqueous humor within minutes (). The uptake was time-dependent and could be blocked by other peptides, indicating a carrier-mediated transport. In other words, the rabbit eye has peptide transporters at its blood barriers that can shuttle small peptides from blood into ocular fluids (). In summary, small collagen-derived dipeptides could cross into the eye if they fit those transporters. This has been shown with model substrates (like glycylsarcosine); natural collagen peptides like Pro-Hyp may also use the same pathways. However, direct evidence that oral collagen peptides enter the eye is still missing. What Studies Show (and Don’t Show) About Eye Uptake To date, no published human or animal study has directly measured collagen peptides in eye tissues or fluids after oral dosing. We have hints but no definitive tracking for the eye itself. The earliest evidence comes from the rabbit glycylsarcosine experiment (): it proves an oligopeptide can cross both anterior (blood-aqueous) and posterior (blood-retinal) barriers in healthy eyes. But glycylsarcosine is a simple model peptide, not derived from collagen. For actual collagen fragments, we only have general distribution studies (like Kawaguchi’s rat autoradiography ()). Those showed radioactivity in skin, cartilage, bone marrow, etc., but made no mention of eyes. It may mean the eye’s radioactivity was low or unmeasured, or simply not reported. If collagen peptides did not accumulate in the eye as much as in skin, the study might not have noted it. Because of the blood-ocular barriers, it seems unlikely that large fractions of orally ingested collagen peptides get into eye fluids. But we cannot rule it out. For example, any collagen peptides in the blood will eventually pass through the blood vessels of the choroid and iris; some fraction might slip through transporters into the sclera, retina, or aqueous. We just lack measurements. In short, evidence is very limited. No study has given people labeled collagen and then sampled their aqueous humor, vitreous, or optic nerve tissue to look for peptides. This is a key data gap. We can only infer from related work that entry is biochemically possible but probably low in quantity. Designing Experiments to Find Collagen Peptides in the Eye Future experiments could directly answer the question by measuring peptide levels in ocular compartments after tracer dosing. For example: Animal Tracer Studies: Give animals (e.g. rabbits or mice) collagen hydrolysate labeled with a heavy isotope or a radioactive tag (such as ^14C or ^3H on an amino acid). After dosing, at various times collect samples of aqueous humor (via needle tap), vitreous humor, and dissect tissues like the trabecular meshwork, sclera, retina, and optic nerve head. Measure radioactivity or use sensitive mass spectrometry to detect labeled peptides in those samples. Autoradiography (exposing eye sections to film) could visually show peptide distribution in ocular tissues. This would directly test if any collagen-derived peptides cross into the eye. Ocular Microdialysis: In larger animals (rabbits or dogs), tiny probes called microdialysis fibers can sample fluid from inside the eye over time. If animals are fed labeled collagen, the microdialysis samples from anterior or posterior chamber could be analyzed for labeled peptides. This technique has been used in ocular drug studies and could reveal time-courses of any peptide reaching the eye fluid. Human Surgical Sampling: Make use of eye operations to sample fluids. For example, prior to routine cataract surgery, a patient could take a dose of collagen hydrolysate containing a non-radioactive stable isotope label. Just before surgery, the surgeon Support the show [https://www.buzzsprout.com/2563091/support]

Collagen Peptides and the Trabecular Meshwork: Mechanistic Links to Intraocular Pressure

This audio article is from VisualFieldTest.com [https://visualfieldtest.com]. Read the full article here: https://visualfieldtest.com/en/collagen-peptides-and-the-trabecular-meshwork-mechanistic-links-to-intraocular-pressure [https://visualfieldtest.com/en/collagen-peptides-and-the-trabecular-meshwork-mechanistic-links-to-intraocular-pressure] Test your visual field online: https://visualfieldtest.com [https://visualfieldtest.com] Support the show so new episodes keep coming: https://www.buzzsprout.com/2563091/support [https://www.buzzsprout.com/2563091/support] Excerpt: Glaucoma and Intraocular Pressure: The Role of the Outflow Pathway Glaucoma is a group of eye diseases that can cause vision loss by damaging the optic nerve. High intraocular pressure (IOP) – the fluid pressure inside the eye – is a major risk factor for glaucoma. Normally, fluid made inside the eye (aqueous humor) drains out through the trabecular meshwork (TM) and Schlemm’s canal (SC) at the front (anterior segment) of the eye. When this drainage becomes blocked or restricted, fluid builds up and pressure rises. In many forms of glaucoma, doctors see extra extracellular matrix (ECM) – the network of proteins and structural components outside cells – accumulating in the TM and SC. This thickened ECM acts like extra “debris” in the drainage channels, making it harder for fluid to exit. Over time, this increased resistance to outflow causes IOP to climb, which can damage the optic nerve and lead to loss of vision (). In a healthy eye, the TM and SC work together like a plumbing system. The TM is a spongy, porous tissue lined by endothelial cells, and it sits just in front of Schlemm’s canal (see illustration below). Fluid flows out through pores in the TM and the inner wall of SC into a blood vessel-like channel (Schlemm’s canal) to exit the eye. Research shows that most of the normal resistance to fluid outflow comes from the juxtacanalicular TM region (the deepest part of the TM right next to Schlemm’s canal) and from the basement membrane of the inner wall of Schlemm’s canal (). In glaucoma, the TM and SC basement membrane become abnormally thick and stiff, filled with extra collagen, fibronectin, and other ECM proteins (). These changes make the outflow paths narrower, like clogging a drain, which raises IOP. () Figure: Fluid drains from the anterior chamber through the trabecular meshwork (TM) and inner wall of Schlemm’s canal (SC). Most outflow resistance – the “bottleneck” – is in the deep TM and inner SC wall (). ECM Remodeling in the Trabecular Meshwork In glaucoma, the TM cells (which behave somewhat like fibroblasts, the connective tissue cells found in skin and other organs) produce extra matrix and fail to break it down properly. The balance of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) shifts so that more ECM is deposited. At the same time, powerful signaling proteins are at play. A key culprit is transforming growth factor-beta (TGF-β). Both TGF-β1 and TGF-β2 are growth factors that normally help tissues heal and regulate ECM, but in glaucoma the level of TGF-β2 in the eye’s fluid (aqueous humor) is abnormally high (). Experiments show that TGF-β2 stimulates TM cells to make more collagen and other matrix molecules, and to cross-link the fibers (via lysyl oxidase enzymes) (). This creates a fibrotic phenotype (like a scar) where the TM is filled with solid matrix and becomes stiffer. Another important factor is connective tissue growth factor (CTGF), also called CCN2. CTGF is induced by TGF-β and further promotes matrix production. Studies in human TM cells found that TGF-β increases CTGF, and that adding CTGF to TM cells causes them to deposit much more ECM (). Blocking CTGF (for example with an antibody) prevents these fibrosis-like changes (). In glaucoma patients, CTGF levels are elevated in the TM, and research suggests CTGF may create a positive feedback loop: as collagen builds up, CTGF drives even more collagen to be made (). In other words, thinner, normal TM becomes thicker and scarred. Integrins are surface receptors that let TM cells sense and bind to the ECM around them. When integrins bind to collagens or fibronectin, they send signals inside the cell that affect its shape, survival, and function. In the TM and Schlemm’s canal cells, many integrins connect to ECM proteins like collagen and laminin (). This “outside-in” signaling can, for example, activate enzymes like FAK (focal adhesion kinase) that influence the actin cytoskeleton. Abnormal ECM (like extra fibronectin or collagen) can therefore trigger inside-out signals too. For instance, when fibronectin is high in glaucoma, it may bind to RGD-recognizing integrins on TM cells, altering their behavior (). However, how collagen fragments or peptides might directly affect integrins in eye cells specifically is still being studied. Overall, the TM and Schlemm’s canal become more fibrotic in glaucoma due to a combination of excess ECM, increased cross-linking, and profibrotic signals (TGF-β, CTGF, cytokines) () (). This fibrotic remodeling raises outflow resistance and IOP. (For more details on TM pathophysiology, see reviews by Vranka et al. and others () ().) Collagen Peptides: Effects on Fibroblasts and ECM Collagen peptides are short chains of amino acids (small protein fragments) derived from collagen. They are commonly taken as dietary supplements for skin, joint, or bone health. In the lab, scientists have tested collagen peptides on various cell types (especially skin fibroblasts) to see what they do at the molecular level. Recent studies suggest that collagen peptides can stimulate fibroblasts and influence key pathways like integrins, TGF-β, CTGF, and MMPs. While data on ocular cells is limited, findings from skin and other tissues provide clues. Fibroblast proliferation and matrix production. Multiple studies have found that collagen peptides can make skin fibroblasts multiply and produce more collagen. For example, Brandão-Rangel et al. (2022) showed that adding collagen peptides to human dermal fibroblasts caused a significant increase in cell proliferation and in the expression of pro-collagen type I (the main collagen of skin) (). Similarly, another in vitro study found that collagen peptides at moderate concentrations boosted the genes for collagen type I (COL1A1), elastin (ELN), and proteoglycan versican (VCAN) in dermal fibroblasts (). In both cases, fibroblasts made more of the building blocks of the connective tissue matrix. A systematic review of studies on hydrolyzed collagen reported that doses of about 50–500 µg/mL of collagen peptides are enough to stimulate fibroblast activity and collagen synthesis in human cells (). In short, collagen peptides appear to help rebuild and strengthen the extracellular scaffolding by prompting fibroblasts to grow and make more matrix. Anti-inflammatory effects and TGF-β. Surprisingly, collagen peptides also have anti-inflammatory actions. In the Brandão-Rangel study, collagen peptides not only spurred collagen production but also suppressed inflammatory markers. When skin cells were exposed to a bacterial toxin (LPS), adding collagen peptides greatly lowered the induced levels of cytokines IL-6, IL-8, TNF-α and others (). At the same time, the peptides raised the levels of TGF-β (and VEGF) in the fibroblasts (). In other words, collagen peptides acted like a signal to calm inflammation and shift cells into a growth/repair mode. Because TGF-β is both anti-inflammatory and pro-fibrotic, this could be a double-edged sword: more TGF-β may help healing, but it could also drive fibrosis if unchecked. Indeed, in the same study the highest dose of collagen peptides (10 mg/mL) was needed to upregulate pro-collagen and TGF-β (). Another report in skin cells found that certain collagen-derived dipeptides (like ile-hydroxyproline) activated the TGF-β/Smad pathway, promoting collagen synthesis (). Thus, collagen peptides can engage the very pathways (TGF-β signaling, Smad) that normally control ECM production. Integrin signaling. Collagen is a natural ligand for certain integrins (notably α2β1 integrin binds collagen). Recent work in skin models shows that collagen peptides can increase the expression of collagen-binding integrins and activate associated signals. Mistry et al. (2024) found that porcine collagen peptides applied to skin cells significantly raised integrin α2β1 levels and triggered downstream signaling via ERK and FAK pathways (). (These pathways normally respond to the cell binding to the ECM.) In those experiments, blocking the β1 integrin subunit prevented the collagen peptide effects in keratinocytes, although fibroblasts still responded, suggesting multiple routes of activation (). The take-home is that collagen peptides can “prime” cells to sense and adhere to collagen. In a trabecular meshwork context, integrin α2β1 is present and mediates collagen binding (). If collagen peptides similarly boost α2β1 on TM cells, that might increase adhesion to the surrounding matrix, potentially influencing outflow. MMPs and TIMPs (matrix remodeling). The matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) control how fast the ECM is broken down. Excess MMP activity leads to ECM degradation, while too much TIMP can preserve ECM and lead to fibrosis. In skin models, collagen peptides seem to reduce the expression of some MMPs. Liu et al. (2019) showed that certain collagen peptide metabolites in culture suppressed activation of AP-1, lowered the protein levels of MMP-1 and MMP-3, and thereby depressed collagen degradation (). Another study noted that increased collagen accumulation in fibroblasts was linked not only to more collagen synthesis but also to Support the show [https://www.buzzsprout.com/2563091/support]