interface fluid syndrome ( ifs ) can develop after laser in situ keratomileusis ( lasik ) . if ifs occurs , intraocular pressure ( iop ) measurements become unreliable . as a result ,
glaucomatous optic neuropathy progresses , followed by a detectable increase in iop and a rapid decline in visual function .
reports have described ifs cases resulting from increased iop secondary to postoperative steroid administration or to corneal endothelial dysfunction triggered by scleral buckling surgery for retinal detachment , a shallow anterior chamber after trabeculectomy , or uveitis . to our knowledge
, no reports have described the development of ifs because of uncontrolled iop after lasik during glaucoma management in the absence of these triggering factors . in this study
, we report on a patient who underwent lasik after iop had been controlled using topical antiglaucoma medications .
two years later , despite the absence of triggers such as steroid use or a history of previous ocular surgery , ifs developed in association with iop elevation and marked loss of visual function .
a 23-year - old man was diagnosed with glaucoma at an eye clinic in january 2009 based on elevated iop in the right eye , and treatment with an unspecified topical antiglaucoma medication was initiated .
one month later , the patient was informed that the iop had normalized , and he spontaneously terminated the use of antiglaucoma eye drops .
approximately 6 months later , the patient underwent lasik for myopia at a lasik center .
he underwent several medical examinations after lasik , but he did not report glaucoma at that center .
therefore , he had not used any antiglaucoma medication after lasik . in september 2010 , an eye doctor at another clinic measured an iop of 29 mm hg in the right eye and 16 mm hg in the left eye using noncontact tonometer ( nct ) .
topical latanoprost 0.005% ( pfizer inc , new york , ny ) once daily and topical timolol maleate 0.5% twice daily in the right eye were initiated , and the patient was referred to kitasato university hospital for further management .
at the hospital , goldmann applanation tonometry ( gat ) revealed iops of 13 and 14 mm hg , and nct revealed iops of 13.9and 15.2 mm hg in the right and the left eye , respectively .
no opacity or edema was observed in the flap or the interface , and there was no inflammation in the anterior chamber .
funduscopy revealed cup - to - disc ratios of approximately 0.9 in the right eye , along with superior and inferior rim thinning , and 0.7 in the left eye .
an attached referral form indicated that the humphrey field analyzer ( hfa ; carl zeiss meditec inc , dublin , ca ) mean deviations ( mds ) were 25.28  db in the right eye and 1.85  db in the left eye using the swedish interactive threshold algorithm standard 30 - 2 program .
the patient 's medical history revealed that before undergoing lasik , the patient had worn contact lenses to correct 8 diopters ( d ) of myopia , with the assumption that the measured iop of 4 to 5 mm hg was underestimated . on follow - up , the iop in the right eye decreased to 9 to 11 mm hg ( gat ) until december 2010 . on june 6 , 2011 ,
the visual acuity ( va ) of the right eye was hand motion , and gat measurement was impossible because the inner edges of the 2 fluorescein semicircles in the prism head were blurred and irresolvable .
the iop was presumed to be high ( at least 30 mm hg ) based on digital palpation and the positioning of the outer edges of the fluorescein semicircles .
an intravenous mannitol drip was immediately administered , and the iop decreased to 24.0 mm hg , as measured using an nct .
oral acetazolamide ( 500  mg / d and 2 types of antiglaucoma eye drops were prescribed .
pachymetry measurements indicated that the central corneal thickness was 540  m in the right eye and 490  m in the left eye .
the corneal endothelial cell densities were 2414/mm in the right eye and 2521/mm in the left eye .
minimal opacity was detected in the flap interface , and no substantial water gap was observed based on slit - lamp examination ( figure 1 ) ; however , an optically empty space corresponding to an interface fluid pocket was detected using axsun anterior optical coherence tomography ( kitasato university , kanagawa , japan ) .
anterior segment findings for the right eye on july 4 , 2011 . an anterior segment optical coherence tomography image of the right eye .
the arrow indicates a small empty space corresponding to an interface fluid pocket visualized using axsun anterior optical coherence tomography ..
on july 13 , 2011 , a trabeculectomy with mitomycin c ( mmc ) was performed on the patient 's right eye .
this pressure remained stable at 2 mm hg for 1 month ; subsequently , an average iop of 5 mm hg was maintained during the first postoperative year .
after surgery , va improved slightly from the preoperative level of light projection to hand motion .
a temporal island of the visual field , as measured by goldmann kinetic perimetry , remained unchanged after surgery . on july 23 , 2012 , iop was stable at 5 mm hg in the right eye , but was increased to 37 mm hg ( as measured by gat ) in the left eye , accompanied by minimal corneal edema .
systemic acetazolamide ( 750  mg / d ) was prescribed , but was insufficiently effective .
no symptoms of ifs were observed in the right eye ; however , a trabeculectomy with mmc was performed on the patient 's left eye on august 1 , 2012 .
in july 2013 , the iops were 6 mm hg in the right eye and 7 mm hg in the left eye ( as measured by gat ) . at this time point , the right eye va was hand motion , whereas the uncorrected va of the left eye was 1.2 ( 20/16 ) .
a fold was observed on the corneal flap interface in the right eye 2 years postoperatively ; this fold diminished over time , but did not completely resolve .
there were no significant differences between the preoperative and 6-month postoperative hfa md values ( 2.23  db and 2.20  db , respectively ) .
ifs , which is associated with inaccurately low measurements of central iop because of cushioning of the fluid - filled pocket , can result from increased iop secondary to postoperative steroid use or corneal endothelial dysfunction after vitreous surgery or trabeculectomy .
a study of human eye bank corneas reported 2 mechanisms of ifs : increased iop ( the high - iop form of ifs ) and corneal endothelial dysfunction ( the endothelial cell damage form of ifs ) . in the current case ,
no steroid treatment was administered before the onset of ifs , and specular microscopy produced unremarkable findings .
this case was classified as the high - iop form of ifs despite a minimal increase in corneal thickness and opacity under the flap because there was no opacity or edema in the flap itself .
both hamilton et al and kang et al reported that ifs is associated with glaucoma , but the mechanisms underlying ifs differed between these 2 studies .
the former report indicated that iop increased with steroid use , whereas the latter report cited corneal endothelial dysfunction resulting from aggressive surgery and 5-fluorouracil intervention as the possible cause of increased iop .
the case described here may be the first reported instance in which ifs developed because of uncontrolled iop during glaucoma management in the absence of triggering factors such as steroid - induced iop elevation or corneal endothelial dysfunction .
dawson et al classified ifs into stages ranging from 0 to 3 based on the degree of fluid retention in the flap interface . using this staging system ,
the right eye in the current case would be classified as stage 2 ; the left eye would be categorized as stage 1 , which is often referred to as pressure - induced interlamellar stromal keratitis .
owing to this delay , the corneal flap might have been stretched by the interface fluid that had accumulated under the flap . as a result ,
even after the interface fluid was absorbed and the space under the flap decreased , the stretched flap did not recover , leading to shriveling of the flap and the sustained presence of a fold at 2 years after surgery . because the central visual field was lost in the right eye , it was impossible to determine how the corneal fold affected the vision of this patient ; however , if a corneal fold had developed in the left eye , we would predict a delay in visual recovery ( figure 2 ) .
we must investigate the reason why the vision in his right eye was nearly lost .
one reason could be the fact that he stopped seeing a doctor and terminated his use of antiglaucoma medication because he was informed that the iop had normalized . once patients are diagnosed with glaucoma , they must continue to be followed by doctors throughout their lives .
it is possible that the explanation provided by the doctor at the first clinic regarding the disease of glaucoma was insufficient .
another reason could be that lasik was performed on the eye without sufficient information about the probability of glaucoma progression and the difficulty of glaucoma management after lasik .
it is well known that the iop is often underestimated after lasik . in this case , on the first visit to our hospital , iop measurements of 13 mm hg in the right eye and 14 mm hg in the left eye were obtained via gat . given the power of the contact lenses ( 8 d ) before lasik surgery , underestimation by approximately 4 mm hg is thought to occur .
this result suggests that the corrected iop might be approximately 17 to 18 mm hg .
according to the target iop used in the advanced glaucoma intervention study , the iop in this patient first reached the targeted iop .
however , to predict the appropriate iop to be maintained for the management of glaucoma in this case , iop and the visual field should be monitored for a prolonged period .
even if there had been no elevation of iop , reducing the iop might have been necessary in the current case . the determination of whether or not treatment is required should be based on frequent medical evaluation and examination . however , one must consider the possibility of an increase in iop because it is not easy to control iop based on underestimated iop measurements using gat
. cases with normal tension glaucoma are unlikely to develop ifs as occurred in this case because the increase in iop in this case is unusual .
alternatively , in glaucoma cases involving a prior increase in iop , iop can continue to increase during the disease course even if temporary control of iop has been achieved .
if lasik is performed in such cases , the treatment may be insufficient because of underestimation of the typical iop .
in fact , the measurement of iop can become difficult at high - iop levels .
thus , lasik should not be performed on eyes with glaucoma because of the high risk of elevated iop .
 abstractthis study sought to describe a glaucoma patient with interface fluid syndrome ( ifs ) induced by uncontrolled intraocular pressure ( iop ) without triggering factors after laser in situ keratomileusis ( lasik).case report and review of the literature.a 23-year - old man with open - angle glaucoma underwent bilateral lasik for myopia in 2009 . 
 two years later , the patient reported sudden vision loss . 
 the iop in the right eye was not measurable using goldmann applanation tonometry ( gat ) , but was determined to be 33.7 mm hg using a noncontact tonometer . 
 ifs was diagnosed based on the presence of space - occupying interface fluid on anterior segment optical coherence tomography images . after a trabeculectomy was performed , the iop decreased to 10 mm hg , and gat measurement became possible . 
 however , the corneal fold remained visible in the flap interface . 
 six months later , the iop in the left eye increased , and a trabeculectomy was performed during the early stages of this increase in iop . following this procedure , 
 the iop decreased , and visual acuity remained stable.in glaucoma cases that involve a prior increase in iop , iop can continue to increase during the disease course even if temporary control of iop has been achieved . 
 if lasik is performed in such cases , the treatment of glaucoma becomes insufficient because of underestimation of the typical iop . 
 in fact , the measurement of iop can become difficult because of high - iop levels . 
 therefore , lasik should not be performed on patients with glaucoma who are at high risk of elevated iop . 
INTRODUCTION
PRESENTING CONCERNS
CLINICAL FINDINGS
DIAGNOSTIC FOCUS AND ASSESSMENT
THERAPEUTIC FOCUS AND ASSESSMENT
FOLLOW-UP AND OUTCOMES
DISCUSSION