3.6. Discussion

The premature infants in our series who needed laser for the treatment of ROP had higher BW (1121 g) and older gestational ages (28 weeks) than their counterparts in the United States (830 g BW average and 26 weeks GA average). The oldest treated infant was born at 33 weeks PCA and the heaviest treated infant was 1700 g, both beyond the screening criteria in the United States. The practical impact of this observation is that each country/region has to apply its own screening criteria for ROP. If criteria from the USA or from Western Europe had been applied, many ROP cases had been lost with subsequent visual loss.

Because of the short window of opportunity during which the laser is effective, timely recognition of the disease is crucial for the positive result of the treatment. In our series, PCA and PNA at treatment were not statistically significantly different between the favorable outcome and unfavorable outcome groups.

Indirect diode laser photocoagulation proved its efficacy in ROP treatment. Our ROP regression rate is comparable to the ones cited in the literature [7]. The laser spots were applied on all the surface of the nonvascular retina, from the anterior margin of the ridge (when identifiable) up to ora serrata. In six eyes, we also placed laser posterior to the ridge for two reasons: to limit the extension of traction toward the posterior pole and to destroy an area, which is known to provide high levels of vasoproliferative factors because it is ischemic. We used this approach only in situations with advanced stage 3 disease in which we identified traction on the retina. All the six eyes had a good outcome (ROP regressed with no anatomical sequelae). Not all authors approve this strategy, arguing that it destroys more of the peripheral visual field with no proven benefit [2].

We delivered laser energy transpupillary in all cases. Laser can also be delivered through the sclera. In terms of efficacy, the two delivery methods are similar, but the transscleral approach is more traumatic. According to some authors, the transscleral approach carries no risk of cataract formation. However, in our series, we identified no case of cataract after laser delivered transpupillary. This is logic, taking into account that the absorption site of the infrared radiation is deep into the choroid, passing through the crystalline lens without being absorbed.

Literature shows that lower GA and BW are associated with poorer outcomes of ROP [6]. These observations could not be verified in our series in which statistical tests proved no significant difference in terms of outcome according to GA and BW.

Our study proves that the only factor with significant impact on ROP prognosis following laser was the ROP type. As such, AP-ROP cases had a significantly worse outcome as compared to the so-called classic ROP ones, which is in agreement with results cited in the literature [10]. The disappointing results that we obtained in AP-ROP cases with laser photocoagulation motivated us to start treatment in these cases with intravitreal Bevacizumab. This attitude significantly improved our results.
