Incidence of posttrabeculectomy cataract among Arabs in Kuwait

Chronic Antioxidant Capacity Loss in Anterior Chamber Environment After Iridectomy

Purpose

To compare the ascorbic acid concentration and total antioxidant capacity in the aqueous humor of pigmented Rex rabbits after sham operation (control), iridectomy, and trabeculectomy.

Methods

Pigmented Rex rabbits were divided into control, iridectomy, and trabeculectomy groups and followed up for 12 months after surgery. Ascorbic acid concentration and total antioxidant capacity in the aqueous humor, intraocular pressure, and the occurrence of cataracts were examined in each group.

Results

The ascorbic acid concentration and total antioxidant capacity after iridectomy and trabeculectomy were significantly lower at one week and at one, six, and 12 months after operation than those in the control group (P ≤ 0.03). Ascorbic acid concentration was positively and significantly correlated with total antioxidant capacity in the aqueous humor (P < 0.01). Compared to the control and the iridectomy groups, intraocular pressure in the trabeculectomy group was significantly lower at one week and at one and six months after surgery (one week: P < 0.01 and P < 0.01, respectively; one month: P < 0.01 and P = 0.03, respectively; six months: P = 0.03). Histological findings in the iridectomy and trabeculectomy groups included the appearance of vacuoles in the lens at six and 12 months after surgery.

Conclusions

Iridectomy causes a sustained decrease in ascorbic acid concentration, followed by a long-term decrease in the total antioxidant capacity within the aqueous humor.

Translational Relevance

The animal model possibly predicts the vulnerability focusing on the antioxidant level in the anterior chamber environment after trabeculectomy and iridectomy per se in clinical settings.

Biometric Changes After Trabeculectomy with Contact and Non-contact Biometry

PURPOSE

To compare biometric changes measured with contact and noncontact methods after mitomycin-C-augmented trabeculectomy.

METHODS

In this prospective study, 31 eyes from 31 glaucoma patients scheduled for primary trabeculectomy were enrolled. Biometric parameters including axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) were measured using contact ultrasound biometry (UD-6000 Ultrasonic A/B scanner biometer; Tomey Corporation, Nagoya, Japan) and a noncontact optical biometry device (Lenstar; Haag-Streit AG, Koeniz, Switzerland). Measurements were taken the day before trabeculectomy and then compared with measurements obtained 3 and 6 months after surgery.

RESULTS

The AL and ACD were significantly decreased at 3 and 6 months compared with baseline values taken with each biometry method. There was a significant increase in LT measured by the Lenstar device at the 3- and 6-month follow-up. At both the 3- and 6-month follow-up, the mean AL measurement reduction with the Lenstar device was significantly lower than that of the A-scan ultrasound measurements. The mean ACD changes between the two devices were not significantly different.

CONCLUSIONS

There is a small but significant decrease in the AL and ACD after trabeculectomy as measured with both the contact and noncontact methods. The amount of AL reduction measured is significantly smaller using the noncontact method, making it the preferable method for intraocular lens power calculation for patients who need cataract surgery combined with or after trabeculectomy. The LT measured by the Lenstar device increased significantly after the operation, which can be an early sign of the progression of cataractous changes after trabeculectomy.

Physiology of vitreous surgery

Vitreous surgery has various physiological and clinical consequences, both beneficial and harmful. Vitrectomy reduces the risk of retinal neovascularization, while increasing the risk of iris neovascularization, reduces macular edema and stimulates cataract formation. These clinical consequences may be understood with the help of classical laws of physics and physiology. The laws of Fick, Stokes-Einstein and Hagen-Poiseuille state that molecular transport by diffusion or convection is inversely related to the viscosity of the medium. When the vitreous gel is replaced with less viscous saline, the transport of all molecules, including oxygen and cytokines, is facilitated. Oxygen transport to ischemic retinal areas is improved, as is clearance of VEGF and other cytokines from these areas, thus reducing edema and neovascularization. At the same time, oxygen is transported faster down a concentration gradient from the anterior to the posterior segment, while VEGF moves in the opposite direction, making the anterior segment less oxygenated and with more VEGF, stimulating iris neovascularization. Silicone oil is the exception that proves the rule: it is more viscous than vitreous humour, re-establishes the transport barrier to oxygen and VEGF, and reduces the risk for iris neovascularization in the vitrectomized-lentectomized eye. Modern vitreous surgery involves a variety of treatment options in addition to vitrectomy itself, such as photocoagulation, anti-VEGF drugs, intravitreal steroids and release of vitreoretinal traction. A full understanding of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and improves retinal hemodynamics. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and the permeability effect of VEGF reduced with corticosteroids. Starling's law explains vasogenic edema, which is controlled by osmotic and hydrostatic gradients between vessel and tissue. It explains the effect of VEGF-induced vascular permeability changes on plasma protein leakage and the osmotic gradient between vessel and tissue. At the same time, it takes into account hemodynamic changes that affect the hydrostatic gradient. This includes the influence of arterial blood pressure, and the effect oxygen (laser treatment) has in constricting retinal arterioles, increasing their resistance, and thus reducing the hydrostatic pressure in the microcirculation. Reduced capillary hydrostatic pressure and increased osmotic gradient reduce water fluxes from vessel to tissue and reduce edema. Finally, Newton's third law explains that vitreoretinal traction decreases hydrostatic tissue pressure in the retina, increases the pressure gradient between vessel and tissue, and stimulates water fluxes from vessel into tissue, leading to edema.

Cataract formation after initial trabeculectomy in young patients

OBJECTIVE

To evaluate the risk of cataract formation in young patients after initial trabeculectomy.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Thirty-four eyes from 27 patients undergoing initial trabeculectomy at the Glaucoma Consultation Service, Massachusetts Eye and Ear Infirmary (mean age, 43.7 years; range, 12-54 years).

INTERVENTION

Follow-up averaged 42.6 months (range, 11-90 months).

METHODS

Lens status was observed before surgery and at 3 months; 6 months; and 1, 2, 3, 4, 5, and 6 years after initial trabeculectomy.

MAIN OUTCOME MEASURE

The main outcome measure was defined as cataract extraction for visually significant lenticular opacifications that developed after trabeculectomy.

RESULTS

The rate of cataract extraction after initial trabeculectomy was 24% (n = 8). The average time from trabeculectomy to cataract extraction was 26 months (range, 5-58 months). Progression of lenticular opacities occurred throughout the follow-up period. There was no increased rate of cataract formation in subjects with uveitic and steroid-induced glaucoma when compared with all other types of glaucoma. In the patients with both eyes in the study, the first eye was a predictor of cataract progression in the fellow eye.

CONCLUSIONS

Cataract is a common complication after trabeculectomy in young patients. The 24% rate of cataract extraction after trabeculectomy reported in this study is a significant risk of which young patients contemplating surgery should be aware.

Short-term effect of mitomycin-C augmented trabeculectomy on axial length and corneal astigmatism

PURPOSE

To evaluate the short-term effect of trabeculectomy with adjunctive mitomycin-C (MMC) on corneal astigmatism and axial length.

SETTING

Asan Medical Center, University of Ulsan, Department of Ophthalmology, Seoul, Korea.

METHODS

Eighteen consecutive eyes of 16 patients having trabeculectomy with adjunctive MMC were prospectively analyzed. Intraocular pressure (IOP) and axial length were evaluated preoperatively and 1, 3, 6, and 12 months postoperatively. Postoperative changes in corneal astigmatism were evaluated using vector analysis.

RESULTS

The overall mean induced astigmatism showed with-the-rule change up to 3 months postoperatively followed by an against-the-rule shift. The mean axial length was significantly less postoperatively and changed throughout the 12 month follow-up. There was a positive correlation between postoperative axial length and IOP. Eyes with higher preoperative IOP had a greater decrease in axial length after trabeculectomy with MMC.

CONCLUSION

The induced corneal astigmatism after trabeculectomy with MMC was long lasting, although less than that in previous studies. The change in axial length after surgery was significant, especially in eyes with a high preoperative IOP. The decrease in axial length persisted throughout the follow-up.

Cataract development after implantation of the Staar Collamer posterior chamber phakic lens

Implantation of a posterior chamber phakic intraocular lens is an effective refractive procedure with a good safety record in the short-term follow-ups reported in the literature. Cataract formation is a potential complication of the procedure. Two patients developed lens opacities in 3 eyes after the procedure was performed for myopic astigmatism. The possible causes are discussed. This is not a dangerous complication as cataract extraction is easily achieved if necessary. However, it is undesirable and further research is required to assess the long-term incidence, causes, and ways to prevent its occurrence.

Nuclear sclerotic cataract after vitrectomy in patients younger than 50 years of age

PURPOSE

To evaluate the occurrence of cataract formation after pars plana vitrectomy and gas-fluid exchange in patients younger than 50 years of age.

METHODS

Twenty-eight patients younger than 50 years of age with bilaterally symmetric crystalline lenses underwent pars plana vitrectomy and gas-fluid exchange in one eye. Postoperatively, lens photographs were used to assess any asymmetry between the surgical and nonsurgical eye. Lens photographs were graded by three independent masked observers using the Lens Opacities Classification System III (LOCS III). Significant cataract progression was defined as either cataract extraction in the surgical eye or a greater than a 0.9 LOCS III unit difference in lens opacity between the surgical and nonsurgical eye. Results were compared with 28 patients older than 50 years of age who had undergone identical surgery.

RESULTS

In only 7% of patients younger than 50 years of age (mean age, 36.5 years; range, 16-47 years) did significant lens opacity develop in the surgical eye compared with the nonsurgical eye during the follow-up period (mean follow-up, 25.4 months; range, 12-43 months). Of patients older than 50 years of age (mean age, 68.2 years; range, 51-85 years), 79% developed significant lens opacity in the surgical eye compared with the nonsurgical eye during the follow-up period (mean follow-up 27.3 months; range, 12-49 months). The difference in cataract progression between patients younger than 50 years of age and patients older than 50 years of age was statistically significant (P < 0.0000001).

CONCLUSION

Pars plana vitrectomy with gas-fluid exchange is minimally cataractogenic within the first few years in patients younger than 50 years of age.

Loss of visual acuity after trabeculectomy

BACKGROUND

Glaucoma filtration surgery can result in loss of visual acuity by a variety of mechanisms. The existence of "wipe-out" (loss of the central visual field in the absence of other explanation) as a cause of postoperative loss of visual acuity has been debated. This study defines the incidence and etiology of visual acuity loss within 3 months of trabeculectomy.

METHODS

The authors reviewed 508 eyes of 440 patients who underwent trabeculectomy to find cases of postoperative visual acuity loss (2 or more Snellen lines or a category change) and randomly selected a control group of 85 eyes to analyze the risk factors for each cause of visual acuity loss.

RESULTS

Forty-two eyes (8.3%) showed loss of visual acuity after 3 months, caused mainly by lens opacification (n = 16), hypotony maculopathy (n = 6), and "wipe-out" (n = 4). Older patients (P = 0.0108), those in whom the visual field preoperatively showed macular splitting (P = 0.0084) and those who had severe hypotony (intraocular pressure [IOP] < or = 2 mmHg) on the first postoperative day (P = 0.0246) were more likely to experience "wipe-out." Older age (P = 0.0495) and shallow anterior chamber (P = 0.0003) were correlated to the development of lens opacification. Hypotony maculopathy was associated with coronary artery disease (P = 0.0397) and systemic hypertension (P = 0.0118).

CONCLUSIONS

Lens opacification was the main cause of early visual acuity loss after trabeculectomy, followed by hypotony maculopathy. "Wipe-out," although rare, does exist, and older patients with advanced visual field defects are at increased risk.