Hello, everyone.
Unfortunately I don't have any definite information about either the T-Rex Active UV Heat OR the ExoTerra Solar Glo mercury vapour lamps. I wish I did....
When the problem first appeared with the ReptileUV MegaRays, I sent an email to the Director of Research at T-Rex, and also to the owner of Komodo Reptile Products in the UK, whose mercury vapour bulb is also a Westron bulb, asking for information; neither of them have replied.
I then emailed Westron directly and asked them directly, whether their other mercury vapour lamps (which appear to be absolutely identical to the MegaRays) were affected. Again, I have received no reply.
However, I have been told by ReptileUV that the white external "overspray" was something specific to ReptileUV; an extra, protective measure carried out after a double-check of the UV readings led them to believe some lamps were coming off the production line with too high a reading.
As far as I know, no "overspray" has been applied to any T-Rex or Komodo lamps; or if it has, no-one has mentioned it that I'm aware of.
I've only ever seen one single report (on this forum, in fact) of a T-Rex lamp causing what sounds like photo-kerato-conjunctivitis. (PKC)
Soooo... and THIS IS JUST A GUESS I'm afraid .... maybe these lamps are lower-UVB output anyway? So even if the glass was the same, there is a lower risk of eye problems developing? As I say, this is just a guess. If I hear from anyone with any facts, I'll post something here.
It's very clear from the continuing saga with the compact lamps, that if a lamp is placed far enough away from the reptile, or the output of the wavelengths causing PKC is low enough at normal basking distances, then PKC is avoided. Reducing the overall output from the compact lamps reaching the reptile, by (a) burning them for 150 hours before leaving the factory and (b) setting a greater minimum distance from the lamps on the instruction leaflet virtually eliminated cases of PKC from ZooMed's compact Reptisun lamps....
I have always maintained that this is not an ideal approach because the unwanted wavelengths are still in the light ... just too weak to cause acute eye problems. I think most people agree with me on this and that is why ZooMed are slowly replacing their stock with lamps having the new phosphor.
But it is certainly worth bearing in mind that of the hundreds, maybe thousands of ReptileUV and T-Rex lamps sold since October, this forum is the only place on the internet where I've picked up information about a problem (try Googling combinations like "eye problem, MegaRay") and so far I've counted 42 possible cases. (I say "possible" not because I doubt anyone's word, but because scientifically-speaking, these cases haven't been confirmed as definitely PKC caused by the lamp; actually, scientific proof is rarely possible in clinical veterinary medicine, let alone on a hobbyists' forum.)
Of course, that's 42 too many. ReptileUV have acknowledged this and seem to be working day and night to solve it. I understand they are researching a coating which selectively blocks more of the shorter-wavelength light.
But it is possible that some cases are occurring because ReptileUV have always pioneered "sunlight" levels of UVB, ie. with UV Index higher than many other brands (e.g., ZooMed Powersun info leaflets used to say that their UVB output was equivalent to the light in outdoor shade) and as a result, if a problem like this glass crops up, the first PKC will occur in lizards basking really close to the most high-output lamps.
I have noticed that in some of the reports, the MegaRay has been at the absolute minimum safe distance or even closer.... If you have a lamp 12" from the basking shelf an adult dragon's head could be only 9" from the lamp... I think the recommended distance is about 14" above the reptile's head? I guess in the past, having them too close has not been an issue. But now, it is.
Now...About the ExoTerra Solar Glo mercury vapour lamps.
Again, I don't have a definite answer here. I have only ever received four sample lamps, and one arrived broken, so my testing of these is limited to only three lamps.
ExoTerra seem to change the specs on their products very often - if their tubes and compact lamps are anything to go by - so without testing some more, I can't say what's "out there" right now...
The UVB output of two of the lamps (the first 125W and a 160W, tested back in October - November 2007) was about the same; they both gave a UV Index of about 5.0 at 30cm distance, falling to about 4.0 after 100hours use. This is a good UVB output, for sun-loving basking species such as bearded dragons. The difference between the two lamps was that the higher wattage lamp gave out more visible light and more heat.
The spectral analysis showed that the UVB output was in the correct range of wavelengths for vitamin D3 synthesis with no dangerous low wavelength light. The beam was not very wide; when newly burned-in, the 125W made a "footprint" of UVB with a UV Index of 1.0 or more, in a circle of diameter just under 20cm.
I tried to put the 160W on long-term testing but when I put it in a dome, to go over a vivarium, it kept cutting out - I think it was overheating, but I'm not sure.
I used the 125W instead, and had no problems with it. After 1,000 hours, (3 months) the 125W on longterm test decayed to UVI 3.8; after 2,000 hrs (6 months) it was still UVI 3.4. I think that's really quite good...
The second 125W lamp I received was in March 2009, and the result was disappointing, however. It started with a UV Index of 3.6 at 30cm, which seemed a bit low compared to the other two, but still ok; but after only 100 hours this had fallen to only 2.2. That is a very significant decay and a much lower output than before; you can get that with a ZooMed Reptisun 10.0 tube fitted with a reflector. I have not put that lamp on long-term testing.
I don't have any way of knowing which of the two 125W lamps is more typical; or whether they are now different again. Maybe they are all very variable; it's a common situation with mercury vapour lamps. I ought to test some new ExoTerra Solar Glo samples, but I don't have a budget to do that I'm afraid.
But I hope that helps...
Frances