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Page 4 of 12 Diaspro et al. Plast Aesthet Res 2020;7:62 I http://dx.doi.org/10.20517/2347-9264.2020.143

Anatomy
Since 2012, three papers have been published with regard to anatomical topics: interestingly, those
[61]
[58]
[60]
published in 2012 and 2013 were both focused on the tear trough region, whilst that in 2015 was
targeted at anatomical knowledge applied to the midface and not only the lower eyelid.
Classification
Two articles provided a classification system for tear trough deformities, along with a review of the available
treatments , and presented a series of treated patients in order to establish correlation with achieved
[45]
[62]
outcomes .

Complications
Complication-related papers have been published since 2012 [25,39] , and have been reported consistently
[68]
[70]
[69]
in 2014 , 2016 [51,69] , 2017 [29,53,54] , 2018 , 2019 [20,55-57,63] and 2020 . These are either case reports or case
series, and one did not mention the size of the study population. The reported follow-up duration, when
[29]
mentioned, ranged from 12 months to 5 years [39,69] , with prolonged edema, the Tyndall effect and contour
[25]
irregularities as the most commonly reported complications, along with diplopia , and xanthelasma-like
[53]
reactions as a rare occurrence. Complications were also reported in several articles, even if not the focus
of the study [13,17,22,28,32,71-75] , and included two cases of cellulitis and one of migraine .
[13]
Technique
Research focused on personal techniques purposed by the authors have been published since 2005. Airan
[12]
and Born and Kane wrote the first articles ever about this topic, both in 2005; technique refinement
[11]
[73]
[43]
and new trends have been published in 2006 [22,23] , 2007 [24,33] , 2011 [16,32,76] , 2012 [26,41,42,66] , 2013 , 2014 ,
[21]
2015 [48-50] , 2016 [27,28] , 2017 [17,52] , 2018 [19,71,74] and 2019 .
Anaesthesia has been used both by local infiltration [11,19,24,31] or by topical application [13-17,48,52] .
Injections performed by needle have been described since 2005 up to 2019 [11-16,21,28,33,74] , while cannula use
has been reported since 2017 [19,30,31,52,71] and only two studies reported both techniques [17,62] .

The injection depth is reported to be carried out directly at the orbital bony border [11,13,15,16,19,27,48,71,73,74] ,
either under the orbicularis oculi muscle [14,24,31,32,50,66,71,74] or subcutaneously [12,33] . The average amount of HA
[12]
[44]
injected into each side is 0.56 mL and ranges from 0.2 mL to 2.0 mL .
Endpoint
Of the 66 studies included for analysis, the majority [19,24,30,31,33,36,62,69,71,74] were focused on tear trough
rejuvenation whilst 10 reported HA injections to treat functional impairments such as lower eyelid
[18]
retraction [23,35,37,67] , cicatricial [34,41,75] and involutive ectropion , and suprachoroidal buckling [40,58] .
Outcome evaluation
In 2010, two papers on objective and validated measurements of the achievable results of non-surgical tear
trough rejuvenation as assessed by digital 3D photographs and cutometer were published [14-16,76] . The papers
[74]
had not been presented up to 2018 and this topic has not been further investigated.

DATA REVISION
This review of the medical literature on HA use for lower eyelid and tear trough rejuvenation identified a
large number of related studies.