Does nose height decrease after surgery with silicone?

Given the amount of time that has passed since your rhinoplasty, what you see now is likely to be what your nose will look like.

After over two years, the swelling is likely completely resolved. If you feel like your nasal bridge is too high, you can undergo secondary rhinoplasty to change it.

From the front view, the bridge appears a little too narrow. Additionally, you can see the outline of the implant from your side view photo which can happen with silicone implants. I would recommend considering a DCF graft to provide a more natural (less operated on) look to your nose.

These Asian (Philippine, Malaysian, Thai, Chinese, Korean, etc) ethnic noses may present different genetical issues the patients might wish to modify, among which worth mentioning sometimes thin (Thai, Chinese, Korean) and sometimes thick (Philippine, Malaysian) skin but always a severe cutaneous shortfall, low dorsum, broad dorsum, flat dorsum, broad nose, short nose, short septum, short tip, eventually bulbous tip (not a constant feature), poorly defined tip, sometimes real alar flare (others is a virtual or fake alar flare caused by the lack of tip support), poorly supported tip, overrotated tip, alar rim retraction, etc.
Its treatment is based on the principles of structure rhinoplasty although upgraded and extended to a higher and larger level of complexity and technical options, with massive cartilage supply from nasal septum, ears concha and very often from rib cartilages, to restore the enormous lack of support, the weakness and the underdevelopment of the nasal skeleton.
Your case allows understanding the majority of anatomical features and technical requirements of such ethnic rhinoplasties, keeping in mind that great part of their features are common to other ethnicities like the African, Afroamerican, Afrocaribbean, etc; the underlying skeletal peculiarities cause the characteristic shape in this ethnicity noses and are the reasons behind their very high surgical difficulty, which explains why there are very few surgeons really trained, capacitated and skilled in such ethnic rhinoplasties and why most surgeons are tempted to employ simpler but disappointing, when not failed or even problematic, resolution methods.
Three key aspects feature Asian noses; the barely existent dorsum and the truncated nasal pyramid, from which half or more is missing; the totally collapsed nasal tip which lacks any kind of support due to totally incompetent filmy alar cartilages, tip which is also disproportionately augmented by a huge fibrofatty pad; and sometimes the large nostrils and excessively protruding alar flare.
The first stage after the open approach dissection of the nose is defatting the massive pad which typically makes these noses bulbous and large; this adipose mass is not only located above and in between the alar cartilage domes, like in any other ethnicity, but also extends between the medial cruras of the columella and spreads over the lateral cruras, the supratip dorsum and the sides of the lower nasal wall; a very meticulous defatting is a must, a very delicate maneuver that must be carried out with great care not to damage the cartilaginous structures and the overlying skin.
Another common finding is how weak, filmy and thin are the alar cartilages in this ethnicity, they play almost no structural role, if any, in the tip and alae shape, being the whole tip unsupported, collapsed and its shape made out of the fibrofatty mass and the skin itself; additionally the tip has no definition is too short and its cartilages lack sufficient length to comply with the required lengthening of the tip and the nose; for all these reasons the lateral cruras are frequently discarded and replaced by new ones made out of the cartilage grafts.
The tip and the columella also needed full replacement, therefore an en bloc tip and columella extended graft can be sculpted out from the rib or other source cartilage grafting.
Also septocolumellar or dorsocolumellar replacement graft augmented with one extension to build the tip and another extension to lengthen the columellar support down to the nasal septum; this structure achieves longitudinal and lateral blockage with stability by pressure forces between the radix, the dorsum, the septum and the interlocking between the dorsal and tip columella parts, with lateral assistance at the tip by means of the side pods formed by the new lateral cruras; no suturing is required to achieve stability of this dorsocolumellar structure.
In the end, the whole dorsum, tip, columella, medial cruras and lateral cruras are reinforced, supplemented or literally replaced by handmade brand new anatomical elements allowing the expansion of the skin cover.
It is remarkable how the septum is also massively short in these ethnicities; this makes the septum insufficient as donor of grafting in most cases and technically forces to some kind of septal lengthening and nose lengthening maneuvers; this is sometimes accomplished by the septocolumellar or dorsocolumellar structure which bridges over the missing gap of septum, thus in such a case there is no need for direct septal lengthening grafting.
Several methods allow rebuilding a massively missing nasal dorsum, either by congenital causes like ethnicity or by acquired traumatisms or iatrogenic dorsal over resections during previous rhinoplasties.
The alloplastic or synthetic prosthesis, made from Gore Tex, Medpor, Silastic, silicone, polyurethane, etc., is a tempting option since it is as easy as an out of the box solution, the surgeon only has to open the sterile sealed package and insert into the nose, only in few cases a slight shaving may be necessary to adapt the prosthetic dorsum to the patient's nose; however this is the worst of all the available technical solutions, to begin with it is unfeasible achieving an optimal fitting on the dorsum, the prosthesis is noticeable through the skin, they look pretty fake and unnatural, the rate of complications like infections, displacement or extrusion are terribly high, they are prone to dislocate, develop capsular contracture, extrude or become secondarily infected during their lifetime, which actually is not indefinite and will need replacement after a few years.
Fat transfer and dermal or fascial rolls are not suitable, they lack volume to rebuild such noses, their look is weird, it is impossible to shape the dorsum with precision and they are not consistent enough; apart from the former they are prone to complications, infection and resorption; they'll likely disappear in the postoperative or be short lasting.
Bone grafting is not recommended, the rates of resorption are very high and the look is not natural; the ideal material to rebuild massive dorsal shortfalls is cartilage grafting, being several the modalities.
Irradiated human or animal cartilage from a tissue bank is not a recommended option; firstly because it is not own patient's tissue, making no sense when there are excellent donors sites available of safer quality, however mainly because the rates of resorption, infection and dislocation with deformities are very high with irradiated cartilage, which in practical terms is a cartilage biologically destroyed by radiation.
Ear and septum cartilage harvested from the patient's tissues are excellent donors biologically but in the vast majority of cases not valid because the available amount is scarce or their shape might not be optimal; notwithstanding their use may be suitable in selected cases.
One popular option which deserves severe criticism is the so called Turkish Delight technique or better named as diced cartilage wrapped in fascia; it essentially consists in harvesting cartilage from the patient's donor sites, commonly the rib, and crush down to tiny bits, which means destroying the chondrocytes or cartilage cells and annihilating any biological viability; once this jelly mass is obtained the surgeon sticks the bits together by applying a synthetic fibrin glue, rolling them in temporalis fascia or both; this roll is inserted as neo dorsum, however the result is an avascular cylinder in which this mass of crushed tissue develops necrosis, resorption, eventually infection, irregularities, deformities, cystic phenomena, etc.; the results are between poor and disastrous in the mid and long term, the touch is fake like jelly and the dorsum experiences molding like it would be clay with palpation or bearing the glasses pads.
The ideal option to massively rebuild nasal dorsums is own patient's rib cartilage; in relative terms to the nose size it is an unlimited source of cartilage, it is biologically compatible and safe since it belongs to the patient, the likeliness o resorption, infection and displacement are terribly low, is firm and strong enough to expand the skin, is form stable, the touch and feel is natural, when it is well tailored the look is totally natural, it should be lifetime lasting and totally opposite to what many surgeons think it does not warp; the only caution to be taken is harvesting straight fragments of rib cartilage and not the curvy ones, and as additional caution peel off the cortex and use mainly the core or central shaft of the cartilage, since the cortex or outer layers have curvaceous streaks of cartilage making it prone to warp.
In the case you post here the rib cartilage not only is an excellent option to rebuild the dorsum but also may serve as donor for other grafts required, like the tip and columella replacement graft and the lateral cruras replacement grafts; the septum, otherwise very short, and the ears remained untouched.
Once the rib cartilage is freed and the donor site meticulously closed by means of layered sutures, the sculpting stage starts so that the necessary anatomical elements can be restored in this kind of noses.
With the personal design I follow in these cases, one single fragment of cartilage is shaped as dorsal rebuild graft with a hollow cylinder carved in at the undersurface of such dorsal graft; this cylinder has the purpose of providing stability by blockage obtained when the patient's natural dorsum would be inserted within; this dorsal graft has other very tricky and interesting geometrical features in its design, like the beveled upper end to match the contour of the nasal radix and the frontalis bone at the frontonasal sulcus, the slope gradient at its lower end to prevent a supratip prominence or polly beak deformity, the somehow imperfect broken contour at its sides in a very slightly rhomboid shape to mimic a natural bridge and avoid a plasticized nasal look, and the thin on top towards thick on bottom of dorsum gradient of dorsal raise in order to create a correct nasal profile; at its caudal end this dorsal graft is shaped featuring a cubic prong matching the tip and columella extended graft in order to achieve interlocking stability by perfect pressure effect.
Once the dorsocolumellar grafting structure is thoroughly tested and deemed as definitive in terms of aesthetic effect and mechanical stability, the final closure of the skin allows the assessment and planning of the nostril sills resection and the alar flare wedge reduction, is they are deemed indicated.
The smooth contour and the perfection of the tailoring of the dorsal block makes often unnecessary additional camouflage with temporalis fascia or specific blockage gestures to prevent its displacement, since the final assembly is a perfect puzzle matching under pressure between the frontalis bone, the original dorsum and the caudal septum.
Experience, fine skills and large amounts of creativity are of paramount importance in order to successfully approach these complex rib cartilage ethnic rhinoplasties.
See the link below to view a full series of images explaining the procedure with real intraoperative and before & after photos.
If you wish better grounded opinion well lit, focused and standard images have to be assessed: frontal, both lateral and both oblique views, from underneath too.
Feel free to request any additional information from me.

You have to give yourself some more healing time.  Your nose and surrounding areas are going to be swollen for a while and you should be consulting the surgeon that performed the procedure but give yourself some time before going back in so some of it can subside. It can take up to a year for final results.As a specialist in rhinoplasty surgery as it pertains to ethnic rhinoplasty, I can tell you that these are the most common issues I hear patients discuss with me regarding their reasons for wanting to alter the appearance of their nose while still maintaining their ethnic identity:
Asian rhinoplasty patients discuss their dissatisfaction with the following: 
Flat nasal profileSlight nasal bridgeFlared nostrilsWide nasal tipPoor nasal tip strengthI employ specialized surgical techniques for Asian Rhinoplasty and my number one goal is to have a unified vision with my patient. I do not want to harm a patient's ethnic identity, however, I want to allow for each patient achieve the very best results they can and that occurs by having a highly personalized and customized surgical plan. I have over two decades of experience in facial plastic surgery and am able to preserve the ethnic characteristics of my patients while delivering the results they desire. 
When selecting a rhinoplasty surgeon, it is of the utmost importance that you choose a surgeon who is board certified in facial plastic surgery. Board certification matters. Especially, when you are considering ethnic rhinoplasty. You want your face and nose in the hands of an experienced and qualified surgeon. 
I am including a website link about Asian Rhinoplasty as well as video that discusses in detail the specifics of this procedure. I hope you find this information helpful. Please feel free to reach out to our New York City office if we can help answer any questions you might have in your decision making process.
Sincerely,
Philip J. Miller, MD, FACS
Double Board Certified Facial Plastic Surgeon

It's difficult to make an accurate assessment without an in-person exam. 
Consultation with an Asian rhinoplasty specialist experienced with autologous grafts will help you to carefully weigh the available options. 

No, silicone does not change over time so the height would not reduce because of this. I would advise going back to your surgeon to discuss possible options. 

Given that you're currently about 9 months out from surgery, a majority of the swelling has likely resolved (though you can see residual swelling in patients up to and beyond a year so without examining you in person it would be hard to say) and I wouldn't expect the bridge to lower too much more than it already has.  
The "starting point" of the nose on the frontal view is typically higher in caucasian patients than Asian patients, and when you use dorsal augmentation in Asian patients, its important to consider how the dorsal height may westernize some of the facial features.  If your goal is to create a more natural Asian look, then you may require revision surgery.  I personally am not a fan of silicone implants but they are used frequently by many surgeons.  It may be best for you to have a consultation with a facial plastic surgeon who specializes in revision rhinoplasty/Asian rhinoplasty for a discussion of your best options and when dealing with revisions, multiple consultations is always a good idea.  Good luck!