Retinal laser photocoagulation, anaesthesia, and pain responses

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Sir,

We welcome the findings by Richardson and Waterman.1 Their work relates to pre-2006 laser techniques, and has several limitations in study design and results’ interpretation. We do not believe that there is a case any longer to support routine use of sub-tenons anaesthesia. We would like to clarify our clinical experience in using contemporary laser photocoagulation methods to treat patients at the Manchester Royal Eye Hospital (MREH).

Recent pathological work has demonstrated full-thickness retinal injury using conventional 100 ms laser photocoagulation that may contribute to pain associated with treatment of proliferative diabetic retinopathy (PDR).2 Since November 2006, we have treated patients routinely using medium-pulse Pascal 10–20 ms laser photocoagulation under topical anaesthesia (oxybuprocaine hydrochloride 0.5% or tetracaine hydrochloride 1% as per the MREH protocol), and associated painful complications are not problematic.3

Among ophthalmologists, it is widely recognised that sub-tenons anaesthesia may be associated with subconjunctival haemorrhage that may compromise retinal laser application, or create an open conjunctival wound with a potential infection risk.4 The authors found that 9% of the respondents used primary sub-tenons anaesthesia; however, this figure seems inconsistent and unrealistic with modern laser practice.1 We have conducted a randomised clinical trial that compared a 20-ms Pascal panretinal photocoagulation (PRP) with the conventional 100-ms PRP without sub-tenons anaesthesia, and no associated painful complications occurred.5

The authors included data regarding the ‘strength of burns per session’. Further clarification regarding these data would be welcomed from the authors. We presume that ‘strength’ is in reference to visible burn intensity that is related to laser power, whereby a significantly higher fluence (power × time/area) is required for the 100-ms PRP compared with the lower-fluence 20-ms PRP. The ETDRS recommended the standard burn intensity (grey-white) as the threshold for PRP laser.

The authors allude to the risks of secondary macular oedema in anaesthetised eyes; this statement is misleading. The risks of post-PRP macular oedema are associated with high-energy and long-pulse laser, underlying macular ischaemia, young type 1 diabetic PDR patients, and weekly multi-session PRP.5

We consider routine periocular anaesthesia for PRP to be an unnecessary extra step for most patients, with additional risks, discomfort, and extra financial cost. Pascal retinal laser may incur significant cost savings for NHS departments, as the treatment times, number of treatment sessions, and total required outpatient clinic sessions are significantly reduced. In the era of Pascal photocoagulation, multi-spot, short-pulse PRP may improve the comfort of the patient's laser journey, and increase the compliance with laser treatment over the long term.

References

  1. 1

    Richardson C, Waterman H . Pain relief during panretinal photocoagulation for diabetic retinopathy: a national survey. Eye (London) 2009; 23 (12): 2233–2237.

  2. 2

    Jain A, Blumenkranz MS, Paulus Y, Wiltberger MW, Andersen DE, Huie P et al. Effect of pulse duration on size and character of the lesion in retinal photocoagulation. Arch Ophthalmol 2008; 126: 78–85.

  3. 3

    Sanghvi C, McLauchlan R, Delgado C, Young L, Charles SJ, Marcellino G et al. Initial experience with the Pascal® photocoagulator: a pilot study of 75 procedures. Br J Ophthalmol 2008; 92: 1061–1064.

  4. 4

    Royal College of Anaesthetists nd the Royal College of Ophthalmologists. Local Anaesthesia for Intraocular Surgery. RCA, RCOphth: London, 2001.

  5. 5

    Stanga PE, Muqit MMK, Henson DB, Young LB, Charles SJ, Turner GS et al. Manchester Study of Pattern Scanning Laser (Pascal®) Panretinal Photocoagulation (PRP) in Proliferative Diabetic Retinopathy [MAPASS]: 1500 burns pattern single session vs single-spot multiple session PRP. Invest Ophthalmol Vis Sci 2009; 50: E-Abstract 196.

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Correspondence to P E Stanga.

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Competing interests

PES has received financial support from OptiMedica Corporation.

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Stanga, P., Muqit, M. Retinal laser photocoagulation, anaesthesia, and pain responses. Eye 24, 1415–1416 (2010) doi:10.1038/eye.2010.37

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