The development of cataract following trabeculectomy

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.

Pointwise linear progression criteria and the detection of visual field change in a glaucoma trial

BACKGROUND

Current pointwise linear regression (PLR) change criteria for visual field analysis are largely empirical.

METHODS

Two independent sets of Humphrey Field Analyzer fields were analysed using PLR. Set i, 56 patients, and set ii, 97 patients, were followed over 16 months. Criteria were tested against set i, and then validated using set ii. Each criterion specified a fixed critical slope of 1 dB/year and with a range of significance from P<0.001 to 0.05. The criteria were varied by altering location number, cluster arrangement, and by requiring points to show change over both 12 and 16 months. True glaucomatous change was differentiated from noise by looking for exclusive progression (EP), the detection of progression without detection of improvement.

RESULTS

Set i required 1 point to have a slope of 1 dB/year and P<0.05 labelled 64% progressing and 58% improving, whereas several stricter criteria were capable of detecting EP. Two points in a perimetric nerve fibre bundle (PNFB) cluster gave optimal EP detection, labelling 8.9% progressing in set i and 7.2% progressing in set ii with a cutoff P-value of 0.026 inset i and 0.013 inset ii.

CONCLUSION

Lax PLR criteria detect large amounts of change. Validating criteria using two data sets allow selection of better criteria, capable of detecting EP. The criterion involving 2 points changing in a PNFB cluster offers the best option for exclusively detecting progression.

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.

The National Survey of Trabeculectomy. III. Early and late complications

PURPOSE

There is a considerable body of literature relating to trabeculectomy, however there are no data representative of the national experience of trabeculectomy in the United Kingdom (UK). The Department of Health funded a national survey of trabeculectomy to establish current practice patterns and the outcome of trabeculectomy in the National Health Service (NHS). In this paper we present the reported complications of first-time trabeculectomy from a nationally representative cohort of patients with chronic open angle glaucoma.

METHODS

Cross-sectional study of consultant ophthalmologists performing trabeculectomy in the NHS. Participants recruited their four most recent consecutive first-time trabeculectomy cases with chronic open angle glaucoma according to study eligibility criteria and data were collected by self-administered questionnaire.

FOLLOW-UP

one year post-trabeculectomy.

MAIN OUTCOME MEASURES

occurrence of early and late complications.

RESULTS

Clinical outcome data were available for 1240 (85.3%) of cases. Early complications were reported in 578 (46.6%) cases and late complications in 512 (42.3%) cases. Some cases had more than one complication. The most frequent early complications were hyphaema (n = 304, 24.6%), shallow anterior chamber (n = 296, 23.9%), hypotony (n = 296, 24.3%), wound leak (n = 216, 17.8%) and choroidal detachment (n = 175, 14.1%). The most frequent late complications were cataract (n = 251, 20.2%), visual loss (n = 230, 18.8%) and encapsulated bleb (n = 42, 3.4%). The occurrence of most complications was not associated with a consultant's specialist interest, level of activity, type of hospital or region. Encapsulated bleb was reported more frequently in a university hospital setting.

CONCLUSIONS

The complication rates reported in this paper represent the national experience of first-time trabeculectomy for open angle glaucoma in the UK. These are similar to previous published studies and highlight in particular, the impact of trabeculectomy on visual acuity in the first year following surgery. This survey provides valid and clinically relevant data on the complications of trabeculectomy for the production of guidelines and standards for audit at regional, local and individual level.

Lens fluorophotometry after trabeculectomy in primary open-angle glaucoma

OBJECTIVE

To evaluate the loss of lens transparency incurred by patients undergoing trabeculectomy.

DESIGN

A prospective cohort study.

PARTICIPANTS AND CONTROLS

Data corresponding to 33 eyes of 33 consecutive patients with primary open-angle glaucoma (POAG) subjected to trabeculectomy (group 1) were compared with those corresponding to 12 eyes of 12 patients with POAG receiving topical antiglaucomatous treatment (group 2).

INTERVENTION

Lens fluorophotometry was performed on the group 1 patients before and 12 months after surgery. In group 2, fluorophotometry was conducted at the onset of the study and at 12 months of follow-up.

MAIN OUTCOME MEASURES

Starting and final lens autofluorescence and transmittance values corresponding to each subject group were compared.

RESULTS

In group 1, starting and final autofluorescence was 556.3 +/- 184.3 and 691.1 +/- 179.3 Eq ng/ml, and starting and final transmittance was 0.78 +/- 0.11 and 0.67 +/- 0.14, respectively. Respective values for group 2 were 574.3 +/- 94.8 and 595.2 +/- 107.0 Eq ng/ml and 0.72 +/- 0.17 and 0.71 +/- 0.16. The mean change between final and initial autofluorescence was statistically different between groups (134.7 +/- 123.7, group 1, 20.9 +/- 25.1 Eq ng/ml, group 2; P < 0.001). Similarly, a significant difference (P < 0.001) in transmittance change was observed between the surgery and control groups (-0.11 +/- 0.072, group 1; 0.02 +/- 0.008, group 2)

CONCLUSIONS

It was demonstrated by lens fluorophotometry that trabeculectomy in POAG leads to a loss in lens transparency.

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.

Viscocanalostomy for open-angle glaucoma in black African patients

PURPOSE

To study the clinical effectiveness of viscocanalostomy in a population of black African patients with open-angle glaucoma that was uncontrolled on medical treatment.

SETTING

Department of Ophthalmology, Medical University of Southern Africa, Medunsa, South Africa.

METHODS

In this prospective study viscocanalostomy was performed in 214 eyes of 157 black African patients with open-angle glaucoma that was poorly controlled by medical therapy. The procedure involves the production of superficial and deep scleral flaps. The deep flap is disserted to the plane of Schlemm's canal. From this plane, an intact window in Descemet's membrane is created by gentle pressure at the level of Schwalbe's line using a cellulose sponge. Aqueous humor diffuses through this window into a subscleral space (lake). Reflection of the inner flap unroofs Schlemm's canal, creating a trough leading to 2 entrances into Schlemm's canal (surgical ostia). A delicate cannula is introduced into the entrance of Schlemm's canal left and right and high-viscosity sodium hyaluronate is gently injected into the canal for 4 to 6 mm. The deeper scleral flap is excised (deep sclerectomy) and the superficial flap is sutured securely using 5, 11-0 polyester fiber (Mersilene) sutures. High-viscosity sodium hyaluronate is then injected into the subscleral lake to act as a physical barrier to fibrinogen migration postoperatively.

RESULTS

Postoperative intraocular pressure (IOP) of 22 mm Hg or less was achieved without medical therapy in 82.7% of eyes. If a beta blocker was added to the cases not achieving 22 mm Hg or less postoperatively, the success rate increased to 89.0%. The average follow-up was 35 months (range 6 to 64 months).

CONCLUSION

Viscocanalostomy produced an encouraging long-term reduction in the IOP of black African patients with glaucoma who would otherwise have had a poor prognosis.

Long-term follow-up of initially successful trabeculectomy

OBJECTIVE

The purpose was to study the long-term outcomes of primary trabeculectomies that were successful at 1 year.

DESIGN

A retrospective study of patients with various types of glaucoma who had trabeculectomies that were successful at 1 year and who had a follow-up of at least 10 years.

PARTICIPANTS

There were 40 patients (40 eyes) who had primary trabeculectomies that were successful at 1 year and who had a follow-up range of 10 to 21 years.

INTERVENTION

Control of intraocular pressure (IOP) and disease progression was evaluated at 5, 10, and 15 years and at the last obtainable follow-up.

MAIN OUTCOME MEASURES

Successful control of IOP was defined as IOP less than 21 mmHg or a reduction of 33% if preoperative IOP was less than 21 mmHg. Successful control of disease progression was defined as stable cup-disc ratios determined by examination, or color photographs or both, as well as stable visual fields.

RESULTS

If an eye was considered successful by IOP at 1 year, the probability of successful control of IOP was 82% at 5 years and 67% at 10 and 15 years. If an eye was considered successful by IOP at 1 year, the probability of successful control of disease progression at 5 years was 77%, at 10 years 61%, and at 15 years 48%. If an eye did not require further glaucoma surgery at 1 year, the probability that it still would not need further surgery at 5 years was 90%, at 10 years 75%, and at 15 years 67%. Forty percent of eyes had cataract extraction by the time of last follow-up examination.

CONCLUSIONS

Loss of IOP control and progression of glaucomatous damage occurs over time despite initial success at 1 year.

Long-term results of trabeculectomy in eyes that were initially successful

A number of published case series provide short-term and intermediate success rates for the surgical treatment of glaucoma with trabeculectomy. There is little information, however, regarding long-term outcomes that extend beyond 10 years. Therefore, we conducted a retrospective study to determine the long-term outcome of eyes that had successful trabeculectomy surgery at 1 year (IOP < 21 mmHg, or lowering by 33% if preoperative IOP was < 21 mm Hg) and had been followed up for at least 10 years. We found 40 such eyes. With respect to IOP control, 83% were still considered to be successful at 5 years, 73% at 10 years, but only 42% at 15 years. Ten percent required additional glaucoma surgery by 5 years, 25% by 10 years, and 58% by 15 years. Forty percent of the eyes had cataract surgery by the time of the last follow-up examination. It appears that there is a significant late failure rate of trabeculectomy in eyes that were initially successful.

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.

Early hypotony after trabeculectomy

The occurrence of early hypotony after trabeculectomy was analysed retrospectively in 60 glaucoma patients. Fifty-two per cent of the eyes had an intraocular pressure < or = 10 mmHg on the first postoperative day. In about one-third of the eyes, the intraocular pressure was < or = 5 mmHg at the first postoperative visit and in more than 70% of these eyes the hypotony was almost unchanged one week after operation. The hypotony one week after operation was not correlated to the age of the patients and the intraocular pressure at operation, nor to the glaucoma type, and showed no significant statistical dependence on the depth of anterior chamber and hyphema. The final untreated intraocular pressure and progression of the postoperative cataract were studied in four groups of patients, formed on the basis of the intraocular pressure level one week after operation: patients with marked hypotony, slight hypotony, normal pressure or with hypertension. The final untreated intraocular pressure in the eyes with early marked hypotony was not significantly different from the final untreated intraocular pressures in the slightly hypotonic and normotonic eyes. However, the untreated intraocular pressures in these three eye groups were significantly different from the untreated intraocular pressure in the eye group with hypertension. Fifty-two per cent of the eyes suffered from cataract progression during a mean follow-up period of 24 months. Postoperative cataract progression in the markedly hypotonic eyes was not significantly different from the cataract progression in the other groups of eyes.

Development of cataract after trabeculectomy

Cataract progression after trabeculectomy was investigated in a study of 47 eyes with exfoliative glaucoma (ExG) and in 20 eyes with primary open-angle glaucoma (POAG). Cataract progression was assessed from the need for cataract extraction, deterioration of visual acuity by > or = 2 Snellen lines, myopic change in the refraction and increase in the lens opacity value, measured with a Lens Opacity Meter 701. Measurements were made 6 and 12 months after trabeculectomy and at the follow-up visit at 26 +/- 11 months. ExG, age, hypotony (IOP < or = 5 mm Hg) lasting > or = 5 days and early postoperative IOP rise > 30 mm Hg were observed to be risk factors for cataract progression. In pairwise analysis of 14 patients, in which the unoperated eye served as the control, a myopic change of refraction was the most frequent indicator for a change in the structures of anterior segment, possibly indicating cataract progression.

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.

Diabetes, glaucoma, sex, and cataract: analysis of combined data from two case control studies

Data from two case control studies in Oxfordshire were combined and analysed. The combined study covered 1940 subjects, 723 cases, and 1217 controls, between the ages of 50 and 79 with a response rate of 97% for cases and 94% for controls. Diabetes was shown to be a powerful and highly significant risk factor for cataract with a relative risk of 5.04. More than 11% of cataracts in Oxfordshire are attributable to diabetes. The relative risk did not increase significantly with age within the range 50 to 79 years but was higher in females than in males. For females with diabetes the relative risk was 7.85 with 95% confidence interval from 4.30 to 14.3 compared with 3.42 with confidence interval from 2.05 to 5.71 for males with diabetes. Diabetes remained a powerful risk factor when other identified risk factors had been controlled for. No known mechanism for the development of diabetic complications provides an explanation for the excess risk in females. Combination of the two studies led to better estimates of the relative risk of glaucoma as a risk factor for cataract (3.96 with 95% confidence interval from 2.35 to 6.68). The relative risk appeared to be greater in women than in men but this difference was not statistically significant. There was no significant change in risk with age. Glaucoma is a powerful and independent risk factor for cataract in both sexes and may be responsible for 5% of all cataracts in our area.