Fig. 8.44 Healon GV¨ was evacuated from the anterior chamber with bimanual irrigation/aspiration

72 months was 14.7 ± 1.8 mmHg (range 10Ð21 mmHg) for primary open-angle glaucoma and 13.2 ± 1.3 mmHg (range 12Ð15 mmHg) for juvenile glaucoma (Figs. 8.45 and 8.46). After 72 months 77% of treated patients in the open-angle glaucoma group achieved >30% reductions of the IOP, whereas 100% of treated patients with juvenile glaucoma achieved >30% reductions of the IOP. The complete success rate, deÞned as an IOP lower than 21 mmHg without medication, was 79.2% in the group of open-angle glaucoma group and 80% in the juvenile glaucoma group at 72 months.

The average preoperative administration of pressurereducing eye agents was 2.6 (±1.0) for the open-angle

glaucoma group and 3.0 (±1.2) for the juvenile glaucoma group. After surgery, this value decreased to 0.51 (±0.97) for open-angle glaucoma group (Fig. 8.47) and 0.2 (±0.44) for the juvenile glaucoma group at 72 months.

8.3.6 Complications and Management

8.3.6.1 General

This surgery is quite a safe and efÞcient technique with few postoperative complications. As for any Þltering procedure some complications can occur and these can be rapidly identiÞed and handled to reduce the extent of such mishaps. For instance, immediate postoperative hypotony, shallow A/C, hyphema, and choroidal detachment may be present, although to a lesser degree due to the intrinsic properties of the small drainage oriÞce made by the diathermy probe. The usual directives on how to avoid these complications in other Þltrations procedures are also applicable to the sclerothalamotomy ab interno.

8.3.6.2 Specific to the Technique

Temporary IOP elevation higher than 21mmHg can be observed. In the above-mentioned trial about 22.6% of all cases encountered such a complication. These patients a responded well to pressure-reducing treatment with one agent and medication could gradually be withdrawn

Fig. 8.45 Average level of intraocular pressure after sclerothalamotomy ab interno surgery for all 53 cases with open-angle glaucoma

50

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0

Fig. 8.46 Average level of intraocular pressure after sclerothalamotomy ab interno surgery for all Þve cases with juvenile glaucoma

mmHg

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time in months

Fig. 8.47 Administration of pressure-reducing eye agents during 72 months for the open-angle glaucoma group

time in months

in all of these patients. Conversely, hypotension may be present that can last for a few days after surgery.

The trabecular meshwork and SchlemmÕs canal are removed with the high-frequency diathermy probe. Despite the automatic cautery provided by the diathermy probe, it is possible that some small vessels from the iris vascular circle may be affected. Some hemorrhage will result from such insult. Mild hyphema can be observed for a few days after surgery which disappears within the Þrst 2 weeks after the procedure. Similarly the spooling of blood in the anterior chamber

can trigger transient Þbrin formation (Fig. 8.48). Fibrin can be cleared within 1 day after frequent application of topical corticosteroids.

Transient IOP elevation after sclerothalamotomy ab interno may occur in the Þrst 6 weeks and can be effectively brought under control with the use of a topical antiglaucoma medication. In most of the cases, this therapy can be gradually withdrawn after 3 weeks postsurgery. It is believed that moderate tissue swelling around the thalami could be the reason for transient postoperative IOP peaks.

To be efÞcient the high-frequency diathermy creates a thermal energy in the tissues surrounding the probe whereas the temperature at the tip can easily reach 130¡C. While the temperature is focused on a small area, we cannot rule out that some of this thermal energy may spread to the surrounding tissues. We cannot rule out that some of this thermal energy may affect the metabolism of the lens. Some degree of cataract development after sclerothalamotomy ab interno have been reported and some cases have resulted in a decrease in the visual acuity.

8.3.6.3 Conclusions

Sclerothalamotomy ab interno is a new surgical technique for treating open-angle glaucoma and juvenile glaucoma. This ab interno method creats a direct channel between the anterior chamber and the outer portion of SchlemmÕs canal. Persistence of the sclerotomy can be investigated with a three-mirror goniolens. Sclerothalamotomy ab interno creates a deep sclerotomy with subsequent access of aqueous to the scleral layer. Both aspects may facilitate a bypass effect of aqueous outßow. In light of the fact that about 85% of the aqueous humor drains through the trabecular meshwork, we suspect there is an additional route for aqueous humor absorption in the case of elevated IOP. There is evidence in the literature that such bypass effects which do not lead to the formation of Þltering blebs may be present after surgical intervention. In a previous study [11], it was ascertained that eyes without Þlter bleb exhibited very stable long-term IOP regulation postoperatively. In addition to the bypassing of trabecular outßow resistance caused by sclerothalamotomy ab interno treatment, outßow resistance may be further reduced by scleral thinning at the base of the thalamus. In addition, aqueous humor could perhaps be absorbed by the ciliary body [11, 13]. After early postoperative

reduction, the average IOP continues to decline gradually over a period of 6 months before reaching a relatively constant level. It can be speculated that newly formed blood vessels and lymph vessels close to the surgical site, may contribute to the decrease of IOP level during follow-up [10].

In the literature, the success rate for trabeculectomy ranges between 57 and 96% [2, 14Ð26], for deep sclerectomy without collagen device between 57 and 74%, and for deep sclerectomy with collagen device between 58 and 90% [14, 27Ð29]. The sclerothalamotomy ab interno technique with a complete success rate of 90.6% after 24-month follow-up [30], 83% after 48 months and 79.2% after 72 months for open-angle glaucoma is comparable with other so far published surgery methods. The complete success rate for juvenile glaucoma after 48-month follow-up is 80%.

Advantages of the sclerothalamotomy ab interno method, compared with trabeculectomy and perforating and nonperforating deep sclerectomy seem to be the low rate of postoperative complications and a constant level of reduced IOP. Hypotension, a frequent Þnding in trabeculectomy, perforating deep sclerectomy, and nonperforating deep sclerectomy, is a relatively rare postoperative complication. The most frequent early complications in trabeculectomy are hyphema (24.6%), shallow anterior chamber (23.9%), hypotony (24.3%), wound leak (17.8%), and choroidal detachment (14.1%). The most frequent late complications are cataract (20.2%), visual loss (18.8%), iris incarceration (5.1%), and encapsulated bleb (3.4%). After sclerothalamotomy ab interno cataract development was seen in 17% with only 5.7% loss of one line of visual acuity after 72 months for open-angle glaucoma. Compared with other techniques sclerothalamotomy ab interno seems to be a relatively safe surgical technique [14, 17, 27, 28, 31Ð33].

Transient IOP elevation after sclerothalamotomy ab interno may occur in the Þrst 6 weeks and can be