Sir,
This is the first report of diode laser transscleral photocoagulation (TSCPC)1, 2, 3, 4, 5 performed in an African setting by a local team. We retrospectively analysed the records of patients who underwent TSCPC at Dar es Salaam Comprehensive Community Based Rehabilitation for Tanzania Disability Hospital between 10/2007 and 02/2011.
All patients had glaucomatous optic disc changes and intraocular pressure (IOP) >21 mm Hg. All visual acuities were included. TSCPC (Oculight SLx) was performed by ophthalmologists or assistant medical officers, under retrobulbar anaesthesia, using a G-probe (Iris Medical Instruments, Mountain View, CA, USA). The probe was placed 1–2 mm posterior to the corneoscleral limbus. Power was initially set at 1500 mJ for 1500 msec. These parameters were increased until an audible ‘pop' and then adjusted to a subthreshold level. This practice ensured sufficient energy application since the probes were reused with consequent optic fiber damage.
In all, 179 patients underwent the procedure. In cases with bilateral laser (N=3), only the right eye was included. Forty-nine (27%) had follow-up (Figure 1). Twenty-eight (57%) were male. Mean age was 60±14 years and mean preoperative IOP was 53±12 mm Hg. Thirty-four patients (69%) had no perception of light, the others having vision between hand movements and 6/18 (Table 1). Twenty had two and eleven had three postoperative visits. Table 2 shows the interval between TSCPC and postoperative review. Nine (18%) eyes received two TSCPC treatments. The characteristics of laser treatments and the IOP levels at different follow-up visits are summarized in Table 3. Twenty-two patients (45%) had systemic hypertension (HTN) and eight (16%) had both HTN and diabetes mellitus.
Figure 1.
Flowchart of patients treated with diode laser TSCPC.
Table 1. Visual acuity in diode laser-treated eyes (NPL: no perception of light, HM: hand movements, CF: counting fingers).
| Frequency (N) | Percent (%) | |
|---|---|---|
| NPL | 34 | 69 |
| HM | 7 | 14 |
| CF 1 m | 3 | 6 |
| CF near | 2 | 4 |
| CF 2 m | 1 | 2 |
| 6/18 | 1 | 2 |
| No data | 1 | 2 |
| Total | 49 | 100 |
Table 2. Interval in months (N, %) between the 1st diode laser TSCPC treatment and the three postoperative visits and ratio of patients with IOP >21 mm Hg (n, %) for each postoperative visit.
| Time in months | Postoperative 1 N (%) IOP>21 n (%) | Postoperative 2 N (%) IOP>21 n (%) | Postoperative 3 N (%) IOP>21 n (%) |
|---|---|---|---|
| No data available | 6 (12%) 3/6 (50%) | 2 (11%) 2/2 (100%) | 2 (18%) 1/2 (50%) |
| <1 | 25 (51%) 12/25 (48%) | 7 (39%) 2/7 (28%) | 1 (9%) 0/1 (100%) |
| 1–3 | 6 (12%) 5/6 (83%) | 2 (9%) 1/2 (50%) | 2 (18%) 1/2 (50%) |
| 3–6 | 7 (14%) 5/7 (71%) | 4 (22%) 2/4 (50%) | 1 (9%) 1/1 (100%) |
| 6–9 | 2 (4%) 1/2 (50%) | 1 (5%) 1/1 (100%) | 2 (18%) 0/2 (0%) |
| 9–12 | 2 (4%) 1/2 (50%) | 1 (5%) 0/1 (0%) | — |
| 12–18 | — | — | 2 (18%) 2/2 (100%) |
| 18–24 | 1 (2%) 1/1 (100%) | 2 (11%) 0/2 (0%) | — |
| >24 | — | 1 (5%) 1/1 (100%) | 1 (9%) 1/1 (100%) |
| Total | 49 (100%) 28/49 (57%) | 20 (100%) 9/20 (45%) | 11 (100%) 6/11 (54%) |
Table 3. The characteristics of laser treatments and the IOP levels at different follow-up visits.
| N | Range | Min | Max | Mean | Std. deviation | |
|---|---|---|---|---|---|---|
| Age (years) | 49 | 70 | 12 | 82 | 60.4 | 14.2 |
| Preoperative IOP (mm Hg) | 47 | 55 | 20 | 75 | 53.1 | 12.1 |
| Power (mJ) 1st laser | 37 | 1900 | 900 | 2800 | 1567.0 | 301.0 |
| Duration (msec) 1st laser | 34 | 8800 | 200 | 9000 | 3335.2 | 2226.2 |
| Shots 1st laser | 39 | 47 | 4 | 51 | 30.7 | 12.3 |
| Total power (J) 1st laser | 32 | 510 | 15 | 525 | 155.6 | 106.7 |
| Power (mJ) 2nd laser | 6 | 700 | 1050 | 1750 | 1416.6 | 250.3 |
| Duration (msec) 2nd laser | 6 | 8700 | 300 | 9000 | 3800.0 | 3397.0 |
| Shots 2nd laser | 7 | 37 | 19 | 56 | 41.5 | 11.9 |
| Postoperative visit 1 IOP (mm Hg) | 49 | 64 | 0 | 64 | 26.5 | 17.1 |
| Postoperative visit 2 IOP (mm Hg) | 20 | 56 | 4 | 60 | 23.3 | 14.5 |
| Postoperative visit 3 IOP (mm Hg) | 11 | 58 | 2 | 60 | 25.0 | 19.0 |
Postoperative IOP was significantly lower (P<0.01). At the first postoperative visit, 21/49 (43%) patients had an IOP of ≤21 mm Hg and 25/49 (51%) had >50% reduction in IOP (Figure 2). There was a strong correlation between the energy used and the percent IOP reduction at postoperative visit 1 (Pearson correlation −0.443, P=0.016). Analysis of variance did not identify higher preoperative (F=0.7511, P=0.48) or postoperative IOP (F=1.449, P=0.25) in the groups with systemic disease. In all, 4/49 (8%) patients had IOP <5 mm Hg. Three of these eyes were NLP before TSCPC. No choroidal hemorrhage, retinal or choroidal detachment was recorded.
Figure 2.
Mean IOP and 95% confidence intervals before and after diode laser TSCPC.
The authors declare no conflict of interest.
References
- Egbert PR, Fiadoyor S, Budenz DL, Dadzie P, Byrd S. Diode laser transscleral cyclophotocoagulation as a primary surgical treatment for primary open-angle glaucoma. Arch Ophthalmol. 2001;119:345–350. doi: 10.1001/archopht.119.3.345. [DOI] [PubMed] [Google Scholar]
- Preussner PR, Ngounou F, Kouogan G. Controlled cyclophotocoagulation with the 940nm laser for primary open angle glaucoma in African eyes. Graefes Arch Clin Exp Ophthalmol. 2010;248:1473–1479. doi: 10.1007/s00417-010-1363-4. [DOI] [PubMed] [Google Scholar]
- Agrawal P, Dulku S, Nolan W, Sung V. The UK National Cyclodiode Laser Survey. Eye (Lond) 2011;25:168–173. doi: 10.1038/eye.2010.174. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Spencer AF, Vernon SA. “Cyclodiode”: results of a standard protocol. Br J Ophthalmol. 1999;83:311–316. doi: 10.1136/bjo.83.3.311. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lin P, Wollstein G, Glavas IP, Schuman JS. Contact transscleral neodymium:yttrium-aluminum-garnet laser cyclophotocoagulation Long-term outcome. Ophthalmology. 2004;111:2137–2143. doi: 10.1016/j.ophtha.2004.05.027. [DOI] [PMC free article] [PubMed] [Google Scholar]