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Editors Selection IGR 9-1

Surgical Treatment: Trabectome and Trabeculectomy effects on Visual Acuity

Comment by Sameh Mosaed on:

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In a recent report on visual acuity changes within six months of trabeculectomy ab-externo (TAE) vs trabeculotomy ab-interno (TAI), Kono et al. retrospectively reviewed the charts of psuedophakic patients who underwent either of those procedures and compared visual acuity changes, IOP, and risk factors for sustained decrease in vision. Unsurprisingly, they found that visual acuity is significantly decreased with TAE for three months following surgery, whereas TAI did not result in a significant decrease in visual acuity post operatively. Factors identified as risks for vision decline were baseline split-fixation and post-operative hypotony. As expected, the mean IOP at six months post-op was significantly lower in the TAE group (11.4 mmHg ) compared to TAI (16.0 mmHg). The authors conclude that in patients with IOP target in the mid-teens, that a stepwise approach beginning with TAI should be considered to avoid vision decline in the early post-operative period.

While one would argue that patients selected for TAE typically have more advanced disease and are therefore more susceptible to vision loss, the baseline mean deviation on 24-2 visual field testing was not significantly different between the groups (-15.2dB in TAI vs -17.2dB for TAE). However, the authors excluded subjects with baseline vision worse than 20/70 or advanced visual field loss with mean deviation greater than -25dB.

Vision after ab-interno procedures is less prone to early post -op fluctuation, but with typically less IOP reduction as the compromise

While not surprising, these findings do confirm what decades of experience with trabeculectomy have suggested: that best-corrected visual acuity does decline for about three months until returning to baseline, barring any hypotony-related complications. In addition, vision after ab-interno procedures is less prone to early post -op fluctuation, but with typically less IOP reduction as the compromise. These results should be interpreted with some caution as they cannot be applied to patients with more advanced disease.

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