The mean IOPs at baseline and each assessment time point are summarised in table 1. The mean reduction at day 1 was statistically significant for both TCP and ECP. Although the pressures at week 1 and month 1 suggested a general trend towards reduction, IOPs in treated eyes were not significantly different when compared to baseline with both types of lasers.
Table 1Intraocular pressures (IOP) prelaser and post‐laser treatment among eyes treated by endoscopic cyclophotocoagulation (ECP) and trans‐scleral cyclophotocoagulation (TCP)
Normal, untreated ciliary processes demonstrated fluorescence within 10 seconds of fluorescein injection (fig 1). Both TCP and ECP treatment resulted in severely reduced or nonexistent blood flow at the immediate and 1 day time points (fig 2A and C). The ciliary tissues of TCP eyes exhibited areas of central hypofluorescence with surrounding zones of hyperfluorescence, corresponding to focal points of laser and adjacent “skip areas” between treatment spots. The areas of hypofluorescence were shaped irregularly over the iris root, ciliary processes, and the pars plana, demonstrating an extensive target area from external treatment. In comparison, ECP eyes showed continuous areas of dense hypofluorescence over the ciliary tissues (fig 2C). At 1 week, both TCP and ECP eyes had similar angiographic findings as the immediate and 1 day eyes. At 1 month, TCP eyes showed persistent sites of marked hypofluorescence, which corresponded to sites of laser treatment (fig 2B). By contrast, ECP eyes demonstrated partial reperfusion of the ciliary processes that was uniform but of lower intensity when compared to adjacent untreated tissue (fig 2D).
Figure 1Endoscopic fluorescein angiography of untreated ciliary processes, 10 seconds after intravenous injection of 10% fluorescein. NIH Image software was used to trace around ciliary processes (seen as white line tracing) to (more ...)
Figure 2Endoscopic fluorescein angiography of the ciliary processes in eyes treated by cyclophotocoagulation. (A) Trans‐scleral cyclophotocoagulation (TCP) treated eye, 1 day. Junction between treated and untreated processes, (more ...)
The average intensity of the fluorescence over the area analysed on EFA was determined using NIH Image software. A sample tracing of ciliary processes is shown in figure 1. The mean pixel intensity was reduced to less than half of controls in both TCP and ECP groups at the acute and 1 day time points (table 2). At 1 month, the treatment spots in TCP eyes remained severely underperfused with a similarly depressed intensity of fluorescence (36% of control levels), whereas the ECP eyes showed some degree of reperfusion, with the intensity increased to 80% of control levels. It should be noted that scarred, white ciliary processes exhibited a baseline autofluorescence, which accounted for a substantial amount of intensity in tissues that had very minimal subjective fluorescein perfusion. This autofluorescence is similar to that observed clinically from optic nerve drusen, in which the white autofluorescence includes the wavelengths which pass through the yellow detection filter for fluorescein. It was controlled for by subtracting the autofluorescence values from the measured values after fluorescein injection, as described in the Methods section.
Table 2Fluorescence intensity of ciliary process with endoscopic fluorescein angiography, determined using NIH Image software
Histopathology of the ECP treated eyes showed substantial shrinkage, coagulation necrosis, and disorganisation of the architecture of the ciliary processes at 1 day, with loss of epithelium and shrinkage and avascularity of the stroma (fig 4C). For comparison, a histological section from an untreated eye is provided in figure 3. By 1 month after ECP, deeper ciliary vessels appeared patent, consistent with the physiological reperfusion seen with EFA (fig 4D). At 1 day post‐laser, TCP treated eyes demonstrated severe ciliary tissue damage, closure of many of the large and small vessels, and vascular stasis within the remaining vessels (fig 4A). In addition, adjacent anatomical structures such as the pars plana demonstrated damage and disorganisation, especially in histological sections through areas in which the laser probe was not well centred over the ciliary tissue (not shown). Examination of the gross anatomy of the ciliary processes at day 1 also supported the anatomical variability of the coagulation necrosis from TCP, whereas the whitening of the processes after ECP appeared more consistent across the area of treatment. By 1 month, processes showed sclerosis of the stromal tissue and absence of normal epithelial architecture with a continuing exudative response (fig 4B).
Figure 4(A) Histology of trans‐scleral cyclophotocoagulation (TCP) treated eye, 1 day. Severe disruption of individual processes can be observed. Pigment and cellular dispersion is evident (40× magnification). (B) Histology (more ...)
Figure 3Histology of the ciliary region from a normal, untreated eye. Small capillary‐like vessels can be observed in the stroma of the ciliary process, and larger vessels are present in the deeper stroma (100× magnification). (more ...)