Upper Eyelid Blepharoplasty: Surgical Techniques and Results—Systematic Review and Meta-analysis

Background Upper eyelid blepharoplasty is a surgical procedure that aims to correct the typical changes that occur with aging to the periorbital area. The outcomes of this surgery are aesthetic, as well as functional. Many studies have described an impact on the cornea, intraocular pressure, dry eye syndrome, and visual quality. The aim of this systematic review is to compare the different surgical techniques and their outcomes. Methods The authors performed a literature review through online databases PubMed, Web of Science, Clinicaltrials.gov, and CENTRAL libraries. Information was collected about the surgery techniques and the functional and aesthetic outcomes as well as complications of the interventions. Six types of upper blepharoplasty surgery were studied. Data were analyzed using Cochrane RevMan. Results Twenty studies were included in our systematic review and nine in our meta-analysis. We presented results about intraocular pressure, central corneal thickness, flattest keratometry, steepest keratometry, corneal astigmatism, visual acuity, Schirmer test 1 and 2, tear film break-up time and the ocular surface disease index questionnaire, according to type of surgery. Our meta-analysis showed no significant results. Conclusions No significant results were found; however, many studies reported an impact of upper blepharoplasty surgery in the outcomes studied. Only a small number of complications were reported, and patients were satisfied with the aesthetic outcomes. Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/00266.


Introduction
The aging of the periorbita is characterized by a group of processes that can have an impact on eyelid aesthetics and function.Some typical changes that occur with aging are loss of volume in the upper eyelid and periorbita, a higher position of the eyelid crease, a lower position of the eyebrow, especially the lateral portion, reduction of skin elasticity [1], and dermatochalasis [2].
Dermatochalasis is a condition of the upper eyelid characterized by an excess of redundant skin [2].Commonly associated with dermatochalasis is the selective loss and prolapse of the periorbital fat pads through the orbital septum [3,4].This condition has cosmetic as well as functional outcomes, such as the impact on visual acuity, inefficient eyelid elevation, and excessive use of the frontalis and orbicular muscles which can lead to discomfort and a stronger pronunciation of forehead rhytids [5,6].
The upper eyelid has an anterior lamella, which includes the skin and the orbicularis muscle, and a posterior lamella, which includes the tarsal plate and the conjunctiva.Deep to the orbicularis muscle are located the nasal and central fat pads.Sometimes an accessory lateral fat pad can be found.These are different in texture and color.The nasal fat pad is located medially and is a lighter yellow in color while the central fat pad is located laterally to the nasal fat pad and is a darker yellow in color [4].Deep to these fat pads is located the levator palpebrae superioris muscle that inserts into the tarsal plate and creates de superior eyelid crease [7].
Upper blepharoplasty surgery aims to treat dermatochalasis and achieve a more rejuvenated look to the periorbita by correcting the typical changes that occur with aging.The techniques of upper blepharoplasty surgery have evolved with time and several types of procedures can be done depending on the objective and the final look that is desired to be achieved [8,9].
Firstly, blepharoplasty surgery can be done with resection of skin only [2,6,10,11].Another approach to this procedure is the resection of skin followed by the resection of a portion of the orbicularis oculi muscle as well [5,12].Another technique involves the resection of skin and herniated orbital fat, either from the central, the nasal, or from both fat pads.This can be done with or without resection of orbicularis muscle [8,[13][14][15][16]18].A distinct technique aiming for volume preservation in the upper eyelid can be performed by transposition and fixation of the nasal fat pad laterally, to the central eyelid area [9].A different approach, with transposition of a pedicle of excess fat from the central fat pad to the lateral upper eyelid area, can be performed for addressing the loss of fullness in that area that occurs with aging [8].Another technique that can be associated with blepharoplasty surgery is the brassiere suture where a suture is done from the lower and upper margins of the incision made on the orbicularis oculi muscle to the periosteum of the superolateral arcus marginalis.This suture is useful in repositioning the sub-brow fat pad and giving the eyebrow a lifted look [19].
Each surgery type has different outcomes that can be both positive and negative.While some outcomes are related to the aesthetic result and patient satisfaction with the final look, some studies have reported an impact on the cornea, visual acuity, intraocular pressure, and dry eye syndrome.With the development of such different approaches to this surgery, this systematic review aims to compare the different surgical techniques and their outcomes as well as discuss if certain results can be associated with upper blepharoplasty surgery or with a certain type of this procedure.

Methods
This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Study Selection
Two distinct database searches were performed for this study.
First, the authors searched for potentially relevant studies on PubMed, Web of Science, CENTRAL, and ClinicalTrials.govelectronic databases.The query "(blepharoplasty [MeSH Terms]) OR (eyelid/ surgery[MeSH Terms]) OR (blepharoplasty[Title/Abstract]) OR (dermatochalasis [MeSH Terms]) AND (upper[Title/Abstract])" was used for the PubMed database search.For the Web of Science search, the query "upper blepharoplasty (All Fields) or eyelid surgery (All Fields) and dermatochalasis (All Fields)" was used.The query "MeSH descriptor: [Blepharoplasty] explode all trees AND upper eyelid" was used for the CENTRAL search and, on ClinicalTrials.gov, the authors searched for the Condition or Disease: "Dermatochalasis" and Intervention/ Treatment: "Blepharoplasty".
The search was restricted to studies written in English and published in the Plastic and Reconstructive Surgery, Aesthetic Surgery Journal, and Aesthetic Plastic Surgery journals from January 2002 until October 2022.This restriction aimed to select good quality studies published in well-known journals with a high impact factor in plastic surgery, with a high amount of articles focused on aesthetic outcomes.
The eligibility assessment was carried out by two investigators independently.First, relevant studies were selected by title and abstract.Then, a more thorough selection was conducted by reading the full article.The selection was based on the inclusion and exclusion criteria primarily defined.Articles referred in the selected studies considered relevant to the study were also included.
Studies performed on patients who underwent upper blepharoplasty surgery for dermatochalasis or periorbital aging reasons were included.Exclusion criteria included patients with congenital malformations, ptosis, or Asian blepharoplasty.
The aim of this review was to study the positive and negative aesthetic outcomes of different types of upper eyelid blepharoplasty motivated by dermatochalasis or periorbital aging.The inclusion and exclusion criteria were designed to bring focus to this specific topic by excluding other possible reasons for upper eyelid blepharoplasty.The Asian population was excluded because of the surgical implications that the typical Asian eye shape and the Asian beauty standards would have, resulting in aesthetic outcomes that would not be comparable to those of the upper blepharoplasty techniques analyzed in this study.
The results obtained from this database search and selection were more qualitative in nature rather than quantitative, so, another database search was conducted.
For the second database search, the authors broadened the search criteria to include outcomes related to the impact of upper blepharoplasty surgery on intraocular pressure, dry eye syndrome, and corneal topography.Pubmed was searched using the queries "(blepharoplasty[MeSH Terms]) AND (intraocular pressure[MeSH Terms])", "(blepharoplasty[MeSH Terms]) AND (corneal topograpy[MeSH Terms])" and "(blepharoplasty[MeSH Terms]) AND (dry eye syndrome[MeSH Terms])".The queries used for Web of Science were "upper blepharoplasty (All Fields) and intraocular pressure (All Fields)", "upper blepharoplasty (All Fields) and corneal topograpy (All Fields)" and "upper blepharoplasty (All Fields) and dry eye syndrome (All Fields)".The queries used for the CENTRAL database search were "(MeSH descriptor: [Blepharoplasty] explode all trees) AND (MeSH descriptor: [Intraocular Pressure] explode all trees)", "(MeSH descriptor: [Blepharoplasty] explode all trees) AND (MeSH descriptor: [Corneal Topography] explode all trees)", and "(MeSH descriptor: [Blepharoplasty] explode all trees) AND (MeSH descriptor: [Dry Eye Syndromes] explode all trees)".
The search was restricted to articles published in English from January 2002 until October 2022.Due to a lower number of results, the eligibility criteria for this second search did not restrict studies according to publication journals and the Asian population was included.Apart from this, the eligibility assessment was performed similarly to the first database search.

Quality Assessment
Quality assessment was performed throughout the selection process.The risk of bias was calculated using the National Institute of Health.For most studies the Quality Assessment Tool for Before-After (Pre-Post) Studies With No Control Group was used where studies were classified as Poor if they scored 0-4, Fair if 5-8, and Good if 9-12.For two studies [11,21] the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies was used and for another two studies [12,22], the Quality Assessment of Controlled Intervention Studies was used.In both scales the article was considered Poor if it scored 0-4, Fine if 5-10, and Good if 11-14.For one study [23], the Quality Assessment Tool for Case Series Studies was used, where a study was considered Poor if it scored 0-3, Fine if 4-6, and Good if 7-9.

Data Items
Data extraction was performed by one reviewer and then revised by the other two authors.Information about the type of upper blepharoplasty surgery performed, surgical outcomes, and complications was extracted.
The following types of blepharoplasty surgery were included: (1)  Corneal topography and tomography are imaging techniques that analyze the shape and elevations of the cornea.Corneal topography describes the shape of the anterior surface of the cornea and corneal tomography performs a three-dimensional recreation of the anterior segment of the cornea while also providing information about the corneal thickness.These techniques describe the flattest (K1) and steepest (K2) meridians of the cornea which are used to calculate corneal astigmatism (CA).Corneal imaging techniques can also be used to measure central corneal thickness (CCT).CCT is a relevant factor to consider while assessing patients at risk for glaucoma since it can interfere with intraocular pressure (IOP) measurements [13,[24][25][26][27][28].
Intraocular pressure (IOP) can be calculated by tonometers.These estimate IOP by assessing the force needed to applanate the surface of the eye.The Goldmann applanation tonometry is considered the gold standard method for IOP measurement [29].
The Schirmer 1 and 2 tests and tear film break-up time (TF-BUT) are tests that can be performed to assess tear film production and stability.The Schirmer tests measure tear formation on a filter paper that is placed inside the lower eyelid.The difference between these tests is that the Schirmer 2 test is performed after the application of an anesthetic to the eye, measuring only the basal tear formation, while the Schirmer 1 test measures both the basal and reflex tear formation.Tear film break-up time (TF-BUT) is measured after the application of fluorescein into the tear film.The patients are asked to stop blinking and the TF-BUT is the time between a complete blink and the first break in the tear film [22,30,31].
The ocular surface disease index (OSDI) is a questionnaire formed of twelve questions used for patient assessment of dry eye symptoms [22].

Synthesis Methods
Data were organized by outcome.A written description and comparison of results was performed.A meta-analysis including flattest (K1), and steepest (K2) keratometry, corneal astigmatism (CA), intraocular pressure (IOP), and tear film break-up time (TF-BUT) was performed.For the meta-analysis, the Cochrane RevMan Version 5.4.1 (Cochrane Collaboration, Copenhagen) was used.The data analyzed were continuous variables in the form of mean differences and standard deviations.For the meta-analysis, the results were analyzed in a random effects model.Heterogeneity was measured via the I 2 test.A subgroup analysis was performed for skin only blepharoplasty and other surgery types.For all analyses p \ 0,05 was considered significant.

Results
Our first database search resulted in 2079 articles.After the selection process, 8 studies were selected for inclusion.Four relevant articles mentioned in the selected studies were also included.In total, 12 were selected for inclusion in our first database search.Figure 1 represents a flowchart of this selection process, according to PRISMA guidelines.
Our second database search resulted in 121 articles.After the selection process, 8 studies were included.In total, 20 studies were included in our systematic review and 9 studies were included in our meta-analysis.All of them were considered to have fine or good quality.Within these studies, sixteen were prospective and four were retrospective.Nine studies presented results about skin only blepharoplasties, five about skin and orbicularis resection, one about skin and orbicularis resection with pedicled central fat pad, two about skin and nasal fat pad resection, two about skin, nasal, and central fat pad resection, one about skin, orbicularis, and nasal and central fat pad resection with orbicularis suture and three studies did not specify the type of blepharoplasty performed.Information about included studies can be found in Table 1.Information about the outcomes can be found in Table 2.

Flattest Keratometry (K1)
Regarding skin only upper blepharoplasty, two studies found a significant increase in K1 values postoperatively [6,11].Two others found no statistically significant differences in this value [2,10].Ilhan et al. [6] found the variation of the keratometry values to be proportional to the severity of dermatochalasis presented preoperatively.
A study performing skin, nasal, and central fat pad resection found no significant difference in K1 [14].

Steepest Keratometry (K2)
Among the studies that performed skin only upper blepharoplasty, one found a significant increase in K2, proportional to the severity of dermatochalasis presented preoperatively [6], one found a significant reduction of K2 [2] and another one found no significant differences [10].
No significant differences were found in patients who underwent skin, nasal, and central fat pad resection [14].

Corneal Astigmatism (CA)
Regarding skin only resection, two studies showed a significant increase in CA [11,30], and one study showed an increase of CA in forty-one percent of eyes [13].One study showed a significant decrease in CA values [2].Two articles showed no significant differences [10,32].Another article divided patients into groups by severity of dermatochalasis and showed a significant increase of CA in all, except for the group who presented with less severe dermatochalasis.The variation of this value was found to be proportional to the severity of dermatochalasis presented preoperatively [6].
An increase in CA values was found in fifty-seven percent of eyes in patients who underwent skin and nasal fat pad resection and in sixty-eight percent of patients who underwent skin, nasal, and central fat pad resection [13].
Zinkernagel et al. [13] found the increase in CA values to be significantly higher in patients who underwent upper blepharoplasty surgery with central and nasal fat pad resection when compared to patients who underwent skin only upper blepharoplasty.
One study performing both skin and nasal fat pad resection, and skin, nasal, and central fat resection, also found no significant difference in CCT scores after surgery [13].

Visual Acuity
Two studies performing skin only blepharoplasty found no significant difference in visual acuity postoperatively [2,10].

Intraocular Pressure (IOP)
One study showed a significant increase in IOP after skin only upper blepharoplasty surgery [11], however, two other studies found no significant differences [6,32].

Tear Film Break-up Time (TF-BUT)
One study performing skin and orbicularis muscle resection found a significant increase in TF-BUT at six months postoperatively but not at twelve months [22].Two other studies found no significant differences [21,33].

Schirmer 1 and 2 Tests
Two studies found no significant difference in the Schirmer 1 test [22,33], and one study found no significant difference in the Schirmer 2 test [21] in patients who underwent skin and orbicularis muscle resection.
Ocular Surface Disease Index Questionnaire (OSDI) A significant increase in OSDI scores was found after upper blepharoplasty surgery with skin and orbicularis muscle resection by one study [21].However, another article performing the same surgical technique found a significant decrease in the OSDI values postoperatively [22].

Aesthetic Outcome
One study compared the aesthetic results of upper blepharoplasty with skin only resection and skin and orbicularis muscle resection.Three plastic surgeons scored the eyes on a scale from 0 (worst aesthetic result) to 10 (best aesthetic result) on the seventh, thirtieth, and ninetieth days postoperatively.Aesthetic scores were significantly higher in the skin only resection surgery group compared to those of the skin and orbicularis resection surgery group on the seventh day.No significant differences were found on the thirtieth and ninetieth days.All patients in this study were satisfied with the results [12].
In another article performing upper blepharoplasty with skin and orbicularis muscle resection patients also showed to be satisfied with the aesthetic results [21].
Sozer et al. [8] found that an upper blepharoplasty technique that performed skin and orbicularis resection with transposition of a pedicle of the central fat pad to the lateral upper eyelid area improved the lateral fullness of the periorbital area and achieved a more youthful look to the eyes.Both surgeons and patients showed satisfaction with the results and the increase in lateral volume remained stable during the two years follow-up time [8].
Ramella et al. [15] found all patients and surgeons to be satisfied with the postoperative symmetry of the eyes after skin and nasal fat resection upper blepharoplasty.
Thomas et al. [16] performed an upper blepharoplasty technique with skin, orbicularis, and nasal and central fat pad resection with orbicularis suture.Ninety-eight percent of patients were satisfied with this surgery.The other two percent represented a patient who wasn't satisfied with the reduction of orbital fat.This issue was resolved after reintervention and the patient was satisfied with the results.This technique achieved a symmetrical definition of the crease in both eyes.

Complications
One study compared skin only resection to skin and orbicularis muscle resection upper blepharoplasty.Patients rated edema, hematoma, itching, and pain from absent to severe on the seventh, thirtieth, and ninetieth days postoperatively.On the seventh day postoperatively, these results showed to be significantly lower in the skin only upper blepharoplasty surgery group.No significant differences were found on the thirtieth and ninetieth days.
Other than these symptoms, there were no other postoperative complications [12].Syniuta et al. [23] presented a case of a patient who developed strabismus with superior oblique palsy following skin only upper blepharoplasty surgery.
No complications were described in articles performing skin and orbicularis resection with transposition of a pedicle of the central fat pad [8], skin and nasal fat pad resection [13,15], skin, nasal, and central fat pad resection [13], and skin, orbicularis, and nasal and central fat pad resection with orbicularis suture [16].

Meta-analysis
A meta-analysis was performed for the following outcomes: flattest keratometry (K1), steepest keratometry (K2), corneal astigmatism (CA), intraocular pressure (IOP), and tear film break-up time (TF-BUT) scores.The mean difference between these values preoperatively and postoperatively was evaluated.
A subgroup analysis was performed comparing skin only upper blepharoplasties (two studies [2,11]) with the other blepharoplasty techniques (two studies [14,20]), and no significant differences in K1 were found between the subgroups (P=0,30).More information can be found in Table 3.
A subgroup analysis was performed to compare skin only upper blepharoplasties (one study [2]) with the other blepharoplasty techniques (two studies [14,20]) and no significant differences in K2 were found between subgroups (P=0.40).More information can be found in Table 4.

Discussion
Many studies have reported that upper blepharoplasty surgery can have an impact on visual quality [2,10,14,34].Some articles suggest that the alterations in the pressure the eyelid exerts on the cornea after upper blepharoplasty surgery could cause changes in its shape and refractive characteristics [13,20,30,35].
Two studies [6,11] reported a significant increase in K1 values postoperatively.However, our meta-analysis found no significant differences in K1 values when including all studies, skin only resection blepharoplasties, or different follow-up times.No significant differences were found between the skin only blepharoplasty group and the other surgical techniques.
Two studies [2,6,20] found a significant increase in K2, and one study [2] reported a significant decrease in this value postoperatively.No significant differences were found for K2 values on our meta-analysis when including all studies, skin only resection blepharoplasties, and no significant differences were found between the skin only blepharoplasty group and the other types of surgery.
Four studies [ 6,11,20,32] found a significant increase in CA.However, one [6] of these studies grouped patients by severity of dermatochalasis and found this increase to be significant in all groups except the one presenting with less severe dermatochalasis.One other study found a significant decrease in CA [2].Our meta-analysis found no significant differences when including all studies, skin only resection surgery, and different follow-up times.No differences were found when comparing skin only blepharoplasties with the other techniques.
In this systematic review, two studies [2,10] found no significant changes in visual acuity postoperatively.These results are concordant with the fact that no significant differences were found for K1, K2, and CA in our meta-analysis since important changes in these values could have an impact on visual acuity.
Ilhan et al. [6] found the increase of K1, K2, and CA values to be proportional to the severity of dermatochalasis presented preoperatively.Perhaps the reason for the lack of significant results in our analysis was not dividing patients into groups according to the severity of dermatochalasis.Such analysis could not be performed as most of the studies selected grouped all patients together.However, Zinkernagel et al. [13] found changes in CA values to be more significant in surgeries with a reduction of the nasal and central fat pads.Therefore, the lack of significance in our meta-analysis results could also be justified by most of the studies included having performed skin only blepharoplasties.
Regarding the biomechanical proprieties of the eye, some studies have presented results about the impact of upper blepharoplasty surgery on IOP [6,11,32,34] and CCT [2,6,13].
Intraocular pressure (IOP) is an important risk factor for open-angle glaucoma.The Goldmann applanation tonometry is the gold standard measurement for IOP.However, this measurement can be affected by central corneal thickness (CCT).A low CCT can lead to a falsely low IOP result and the contrary can happen with a high CCT.Moreover, some studies have suggested that CCT can be associated with a higher risk of developing glaucoma, even though the role CCT has on its progression and severity in patients with established glaucoma is still uncertain.[36][37][38].
Osaki et al. [11] suggested that the removal of excess skin causes the remaining eyelid skin to increase tension around the eye globe, which could be the cause of increased IOP.Ilhan et al. [6] demonstrated a non-significant increase in CCT values, higher in patients presenting with a more severe dermatochalasis.They stated that even though this increase was non-significant, patients presenting with a more severe dermatochalasis should have a closer follow-up postoperatively.
In our systematic review, three studies [6,11,32] investigated the impact this surgery has on IOP, being that one [11] of them reported a significant increase in IOP after skin only upper blepharoplasty surgery.Three studies [2,6,13] investigated the impact upper blepharoplasty surgery has on CCT and none of them presented significant results.
Our meta-analysis found no significant results for IOP when including all studies and when analyzing a follow-up of more than 6 weeks.No meta-analysis was performed for CCT values.
Our results suggest that upper blepharoplasty surgery doesn't significantly impact IOP or CCT values.Nevertheless, only three studies were included in our IOP meta-analysis, and the number of studies included in our systematic review was also small.Besides that, taking into consideration the results presented by Ilhan et al. [6], perhaps grouping patients by severity of dermatochalasis could lead to significant results in groups presenting with a more severe dermatochalasis preoperatively.Analysis of results according to the type of surgery would also be an interesting approach.This analysis could not be performed due to lack of data.
Transient dry eye symptoms are commonly reported after upper blepharoplasty.These can sometimes be attributed to corneal irritation from the surgery and appear in the first week postoperatively [39,40].Other reasons for these symptoms are the incomplete palpebral closure that occurs in the immediate postoperative period and the exposition of the cornea that was previously covered by the excess skin to external factors such as wind.During this time, it is commonly recommended the use of eye lubricants and sunglasses, and taping the eyes to remain closed during sleep [41].
The orbicularis oculi muscle plays an important role in eyelid closure, affecting tear distribution and tear pumping [39,40].Mak et al. [21] described that in upper blepharoplasty usually only a small strip of preseptal orbicularis is excised and since the pretarsal portion is the part that plays a bigger role in blinking, this surgical excision has a limited impact on blink dynamics.Symptoms of dry eye lasting more than a week can be caused by a weakened orbicularis muscle and usually resolve with time.If these symptoms become persistent, the patient is considered to have dry eye syndrome [39,40].It has also been described that dry eye symptoms can be alleviated after upper blepharoplasty due to the improvement of eyelid function and corneal irritation after excess skin removal [22,39].
Regarding dry eye tests, Schirmer testing measures tear film production, [42] tear film break-up time (TF-BUT) assesses tear film stability [22,31,42] and the ocular surface disease index (OSDI) is a questionnaire that assesses patient-reported dry eye symptoms [22].
In our systematic review, no studies reported a significant impact of upper blepharoplasty on the Schirmer 1 and 2 test.One study [21] found a significant increase and another one [22] found a significant decrease in the OSDI scores after surgery.Both studies performed skin and orbicularis removal.No significant differences in TF-BUT were found in our meta-analysis.
The authors suggest that since no difference was found in the tear film evaluation, the increase in dry eye symptoms reported by Mak et al. [21] could be attributed to the inflammation caused by the surgery.
Regarding aesthetic results, a few different approaches to upper blepharoplasty surgery have been described in this review and most patients were satisfied with the results.
However, there is a need for more studies comparing different types of surgery and the different aesthetic results that can be achieved with each approach.
Common complications associated with upper blepharoplasty include edema, itching, and hematoma.One study found these symptoms to be higher in patients who underwent upper blepharoplasty with skin and orbicularis resection compared to patients who underwent skin resection only, on the seventh day postoperatively [12].
One study described a case of strabismus following upper blepharoplasty.Syniuta et al. [23] consider that a possible cause for this could be trauma to the superior oblique muscle, anesthetic toxicity, or inflammation from trochlear trauma.They also described that blind cauterization could lead to trochlear damage or lesions to the superior oblique muscles [23].
Some limitations to mention in this review are the lack of objectivity regarding the analysis of the aesthetic results, based on patient satisfaction, and the limited number of studies included about the functional impact of upper eyelid blepharoplasty.
The development of an objective and standardized method of evaluating upper eyelid blepharoplasty aesthetic results is in demand.This necessity becomes even more relevant when taking into consideration the numerous surgical techniques currently performed in plastic surgery and the need for an accurate method of comparing their results.
Recently, Arslan et al. [43] performed a study where they divided participants into groups according to the severity of dermatochalasis presented preoperatively.They considered the patients to have mild dermatochalasis when the upper eyelid skin barely connected to the eyelashes, moderate dermatochalasis when the upper eyelid skin overlapped the eyelashes, and severe dermatochalasis when the upper eyelid skin hung over the eye.This subdivision could be useful in future investigations as a standardized method of analyzing the impact of dermatochalasis and aging to the upper eyelid preoperatively, as well as upper blepharoplasty aesthetic results.
The authors consider that there is a necessity for a deeper understanding of the surgical impact on crucial functional parameters.The development of prospective randomized multicenter studies focusing on the true impact of upper eyelid blepharoplasty on CA, CCT, IOP, and dry eye symptoms, as measured by the Schirmer tests, TF-BUT and OSDI, would be extremely beneficial to the future of upper blepharoplasty surgery.

Conclusions
Upper eyelid blepharoplasty was found to have no significant impact on visual acuity, intraocular pressure and dry eye symptoms in our meta-analysis.Regarding the aesthetic outcomes, most patients were satisfied with their results.In the studies included, the number of complications described was low.
To our understanding, there is a demand for an objective standardized method of evaluating and comparing aesthetic results between different surgical techniques and for the development of prospective randomized multicenter studies focusing on the true impact of upper eyelid blepharoplasty on CA, CCT, IOP, and dry eye symptoms.
Figure 2 represents a flowchart of this selection process, according to PRISMA guidelines.

Fig. 1
Fig. 1 Flowchart representing the first database search according to PRISMA guidelines

Fig. 2
Fig. 2 Flowchart representing the second database search according to PRISMA guidelines

Table 1
Study characteristics Number of eyes not mentioned; CA Corneal astigmatism, CCT Central corneal thickness, IOP Intraocular pressure, K1 Flattest keratometry, K2 Steepest keratometry, OSDI Ocular surface disease index questionnaire, TF-BUT Tear film break-up time

Table 2
Study results

Table 3
Meta-analysis results for K1

Table 4
Meta-analysis results for K2.

Table 5
Meta-analysis results for CA D: Diopters; SD: Standard deviation; 95% CI: Ninety-five percent confidence interval; I 2 : I 2 test for heterogeneity; P: P values

Table 6
Meta-analysis results for IOP.