I do not know the answer to the question, however, there was an explanation given about this particular image of Dorje Shugden,
This image of Dorje Shugden is unusually peaceful and has been repainted based on an old thangka from the 1960?s. Similar to another downloadable thangka, this thangka has a plain background, bringing out the main features of Dorje Shugden. Like many Dorje Shugden images, the facial features are said to resemble Kyabje Pabongka Rinpoche, who was one of the most influential Gelugpa lineage masters at the time.
Kyabje Pabongka Rinpoche was responsible for the spread of Dorje Shugden’s practice throughout the Gelugpas, which was continued by his student, Kyabje Trijang Rinpoche.
From: http://www.dorjeshugden.com/downloads/images/peaceful-dorje-shugden-plain/
You can see the original image of thangka painting from: http://www.dorjeshugden.com/downloads/images/peaceful-dorje-shugden/
Oh thanks Vajraprotector for the explanation! Wow I did not know that some of the peaceful form without the 3rd eye was a depiction of the facial features of Kyabje Pabongka Rinpoche! That is so awesome and I feel closer to Dorje Shugden even more with this new knowledge It is quite apt actually.
But in general, based on my own opinion, I think the peaceful form easier to accept to those who are new to the protector practice. The peaceful Dorje Shugden looks more welcoming I suppose LOL. Most people could get turn off with the wrathful aspect, though not for me, I like Dorje Shugden in wrathful form. I guess each to their own eh.
Images of Dorje Shugden without his 3rd eye are NOT meant to depict Kyabje Pabongkha's features. It is perhaps just a coincidence, nothing more, maybe even just referring to that particular image or artists inspiration.
To answer the original question about the 3rd eye - there are both peaceful and wrathful depictions of Dorje Shugden and within each type, further variations. The most wrathful iconography depicts Dorje Shugden with NINE EYES:
- 3 on the face (including the wisdom eye)
- one on the back of each hand
- one on each forearm
- one on each upper arm
This iconography is shown in the attached image yet many other images of him do not depict this full iconography. What's most important is for his practitioners to understand the meaning of the eyes, but ultimately, we can use whichever image of him we prefer for our personal shrines.