Retrobulbar versus subconjunctival anesthesia for cataract surgery

To compare the effectiveness, in terms of pain relief and akinesia of retrobulbar and subconjunctival an aesthesia during cataract surgery and also to compare the degree of postoperative ptosis associated with each technique.

Consecutive adult patients undergoing cataract surgery between March and June 2008 at the Guinness Eye Center Onitsha, were randomized into retrobulbar and subconjunctival an aesthesia by simple random sampling. Patients' subjective perception of pain was graded into none, mild, moderate and severe; eyeball movement during surgery was graded into none, slight, moderate excessive. Two weeks after surgery, the palpebral fissure width was measured with the metre rule to determine the degree of post-operative ptosis.

Of the 90 patients studied, 55 (61.1%) patients had subconjunctival an anesthesia while 35(38.9%) had retrobulbar injection. In the retrobulbar injection group 25 (71.4%) patients had none or mild pains compared to 44 (80.0%) in the subconjunctival injection group; while 10 (28.6%) patients in the retrobulbar group experienced moderate to severe pains, 11 (20%) patients in the subconjunctival group had moderate pains and none experienced severe pains. But the difference in the degree of pain perception between the 2 groups is not statistically significant (χ2 = 0.01; df - 1; P>0.05 ). In the retrobulbar injection group, there was none or slight movement of the globe in 30 (85.7%) patients compared to 49 (89.1%) patients in the subconjunctival group. While 5 (14.3%) patients in the retrobulbar injection group had moderate globe movement, no patient in this group had excessive movement. In the subconjunctival injection group, 5 (9.1%) patients had moderate movement and 1 (1.8%) patient had excessive eyeball movement. The difference in the movement of the eyeball between the retrobulbar and the subconjunctival injections group was not significant (χ2 = 0.004; df - 1; P>0.05 ). In the retrobulbar injection group, the palpebral fissure width was within ≥ 10mm in 18 (51.0%) patients compared with 29 (53.0%) patients in the subconjunctival group. This difference was not statistically significant (χ2 = 0.0006; df - 1; P>0.05 ).

Both retrobulbar and subconjunctival an aesthetic techniques are effective and safe for cataract surgery although the pain experience may be slightly more for patients being operated upon under retrobulbar anaesthesia.