Postoperative RNFL-Changes after Successful Trabeculectomy: 2-Year Outcomes

Abstract

Background The most important tool in glaucoma therapy is to lower the intraocular pressure to slow down the apoptosis of retinal ganglion cells. Trabeculectomy (TE) is considered the gold standard in glaucoma surgery. The aim of this study was to analyse the postoperative changes in retinal nerve fibre layer (RNFL) using optical coherence tomography (OCT) after TE.

Material and Methods We examined 40 patients naïve to prior glaucoma surgery retrospectively, who received a TE for medically uncontrolled primary open-angle glaucoma (POAG). Intraocular pressure (IOP), IOP-lowering medication, mean deviation of perimetry, visual acuity and peripapillary RNFL-thickness using OCT were evaluated during the first 24 month after TE.

Results In total 40 eyes from 40 patients were treated with TE. Mean IOP decreased from 25.0 ± 0,9 to 13.9 ± 0.6 (p < 0.01), and the mean number of IOP-lowering eye drops from 3.3 ± 0.2 to 0.5 ± 0.2 (p < 0.01). Visual acuity and mean deviation in perimetry remained stable while mean global RNFL-thickness decreased from 67.8 ± 2.9 to 63.7 ± 2.9 (p < 0.01) and 63.4 ± 2.9 µm (p < 0.01) 12 and 24 months after TE.

Conclusion The TE is an effective method to reduce the IOD and the amount of IOP-lowering medication. Nevertheless, a significant further loss in RNFL thickness was observed in the first 12 months after TE. Thus, RNFL changes seem to stabilise only after a protracted period.

Fazitbox

• Seit vielen Jahren sind der IOD und die Perimetrie wichtige Bausteine, um die Glaukomprogression zu beurteilen. In den letzten Jahren wurden jedoch ergänzende bildgebende Verfahren entwickelt, wie z. B. die optische Kohärenztomografie (OCT), um die peripapilläre retinale Nervenfaserschichtdicke (RNFL) besser darstellen und quantifizieren zu können.

• Ziel dieser Arbeit war es, die retinale Nervenfaserschichtdicke nach TE mittels OCT über einen Zeitraum von 24 Monaten zu beobachten.

• Trotz erfolgreicher postoperativer Senkung von IOD und der Anzahl applizierter Antiglaukomatosa nahm die mittlere globale RNFL-Dicke innerhalb der ersten 6 postoperativen Monate ab.

• Erst danach scheint sich die mittlere RNFL zu stabilisieren und blieb bis 24 Monate nach TE nahezu konstant. Aus diesem Grund scheinen die Ergebnisse der RNFL-Messungen erst nach dem 1. postoperativen Jahr für weitere Therapieentscheidungen bedeutsam zu sein.

Conclusion Box

• For many years now, IOP and perimetry have been important components in the assessment of glaucoma progression. In recent years, however, we have seen the development of supplementary imaging techniques, such as optical coherence tomography (OCT), which make it possible to better visualize and quantify the thickness of the peripapillary retinal nerve fiber layer (RNFL).

• The goal of this study was to observe RNFL thickness using OCT for a period of 24 months following TE.

• Despite a successful reduction in IOP and in the number of antiglaucoma medications applied, the mean global RNFL thickness decreased during the first 6 months after surgery.

• Only after this period did the mean RNFL appear to stabilize, and then remained virtually constant up to 24 months after TE. For this reason, it seems that results from RNFL measurements only become significant for treatment decisions after the first year following surgery.

Key words

trabeculectomy - peripapillary retinal nerve fiber layer - optical coherence tomography - primary open-angle glaucoma

Publication History

Received: 20 May 2023

Accepted: 30 October 2023

Article published online:
22 December 2023

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