Sir,

First of all, we would like to express our appreciation for Dr Fry's valuable comments.

Safety doses of midazolam are between 0.01 and 0.1 mg/kg.1 A total of 1–1.5 mg doses may be more suitable in senile cataract patients as noticed by Fry. In our study, a single dose of 3 mg midazolam was given 15 min before operation also utilizing the premedication effect, and another agent was not given during the entire course. The dose was given under monitoring and no sign of hypoventilation was observed until draping. Therefore, we did not think that hypoventilation observed after draping was related to the dose of midazolam used. Additionally, the patients may overcome the stage of local block more comfortably in the dose used. Fry states that there had been a drop in the rate of sedation for cataract surgery in recent years. A dichotomy between North American practice, in which i.v. sedation appears to be used routinely, and northern European practice, in which sedation is used less frequently, has been reported.2 The choice of sedation may change according to trends and regions. Nowadays, use of topical anaesthesia in cataract surgery is being increased and the routine use of sedation is being abandoned at our clinic.

In our study, a significant reduction in oxygen saturation was not observed in the treatment group. We agree that the draping duration was longer than an average time especially for phacosurgeons. The cases of transition to phacoemulsification had been included in the study. The duration of draping may be an example of several conditions such as resident cases, hard or complicated cases, etc. The study may also be a guide to other ophthalmic surgeries such as cataract surgery combined with glaucoma surgery, vitreoretinal surgery, etc. It has been shown that carbon dioxide concentration under the drape 15 min after covering reached 3.5% in unsedated subjects.3 This means that even in shorter-time cataract surgery, CO2 retention under surgical drape is quite possible. Without suction system, 5–10 l O2, which can cause drying in mucous membranes and air insufflation may disturb the patients, may be preferred, but with suction system high O2 flow is not needed and CO2 is removed off from the environment.4, 5, 6 As seen in previous studies, not even fresh gas flows up to 10 l/min prevented the accumulation of CO2 under the drapes. The rate of CO2 in expired air, and thus CO2 rate in inspired air is reduced.3, 7 Suction system is a simple equipment, easy to handle and does not necessitate so much effort. Suction of surrounding air combined with low-dose oxygen supply seems to be an adequate means of preventing CO2 retention.3, 4, 5, 6 The suction system will be especially helpful in patients with pre-existing severe cardiovascular and pulmonary disorders that were not included in our study or in patients having prolonged draping duration.