In 2019, a 64-year-old female presented for a second opinion regarding a decline in vision associated with pain in her left eye. At the time of her presentation, she was bandage contact lens dependent with a best-corrected visual acuity of 20/200 in her left eye. Her history revealed uncomplicated LASIK for monovision outcome (left eye corrected for near) in 2007. She subsequently underwent cataract surgery in both eyes in 2010.
Following cataract surgery in her left eye, the patient struggled with recurrent corneal erosion syndrome for approximately 1 year. This eventually resolved following treatment with a bandage lens and amniotic membrane graft.
In 2017, however, the patient experienced a decline in vision associated with pain in her left eye. She was treated with prednisolone and sodium chloride drops 4 times a day.
After two years of persistent, intermittent pain and blurry vision, she presented for consultation at the Bascom Palmer Eye Institute, in Miami.
Exam Findings
Examination of the right eye revealed a well-centered, clear LASIK flap and a posterior chamber IOL within the capsular bag. The eye was white and quiet with an uncorrected visual acuity (UCVA) of 20/20.
Examination of the left eye revealed a diffusely edematous cornea with bullous changes over the lower half of the cornea (after removal of the bandage contact lens). Irregular corneal staining with fluorescein was noted in the area of bullous changes.
IOP measurements were 14 mmHg in the right eye and 17 mmHg in the left eye, when measured centrally. When IOP was measured peripherally, the readings were 15 mmHg in the right eye and 27 mmHg in the left eye.
Specular microscopy of the left eye revealed poor endothelial cell architecture (poor quality image, as expected, due to the overlying corneal edema).
Anterior segment (AS)-OCT showed a fluid cleft between the overlying LASIK flap and the remainder of the corneal stroma.
Diagnosis
The patient was diagnosed with interface fluid syndrome (IFS). It occurs when fluid accumulates in the potential space between the LASIK flap and the underlying corneal stroma. IFS is a rare complication that can occur at any time in a patient who has a history of LASIK. It has also been seen after Descemet stripping automated endothelial keratoplasty1 and SMILE.2 The condition can lead to glaucomatous optic neuropathy without intervention, as the IOP may be deceivingly low when measured on the central cornea.
Etiologies for IFS include high IOP (often from postoperative steroid use for corneal edema), Posner-Schlossman syndrome, corneal endothelial decompensation (with or without Fuchs’ endothelial dystrophy), 3-7 and toxic anterior segment syndrome.8
It may be easy to miss an elevation in IOP since central pressure measurements are inaccurate in these patients, making the diagnosis challenging. However, the increasing availability of AS-OCT imaging may facilitate earlier diagnosis and subsequent targeted treatment.5
AS-OCT clearly reveals the classic fluid cleft of IFS beneath the LASIK flap. In addition, specular microscopy is essential in determining the role of underlying endothelial dysfunction in these challenging cases.
When these advanced imaging devices are not readily available, comparison of IOP readings from the central cornea to the peripheral cornea, and to the other eye, can facilitate diagnosis.7-9
Management
When IFS is suspected, initial medical treatment with IOP-lowering agents and avoidance or sparing the use of steroids can help preclude the necessity to progress to surgical intervention,4,5 such as Descemet’s membrane endothelial keratoplasty (DMEK).The longer the course of the corneal edema, the increased incidence of surgical intervention.
The 64-year-old female patient was started on IOP- lowering drops b.i.d. in the left eye, while the prednisolone was decreased to once a day. She was maintained on the bandage contact lens to help manage her discomfort. The corneal edema persisted, and the patient was unable to tolerate any further decrease in the steroid drops despite multiple attempts. She was then scheduled for DMEK surgery in the left eye. Surgery went well, and the patient returned to 20/25 UCVA at postoperative month 1.
Raise Suspicion
Interface fluid syndrome is a rare but potentially visually devastating complication that may occur in patients who have a history of LASIK. It is important to be suspicious of this diagnosis when patients present with corneal edema after LASIK, independent of the time lapse since surgery. CP
References
1. Hurmeric V, Wang J, Kymonis GD, Yoo SH. Persistent lamellar interface fluid with clear cornea after Descemet stripping automated endothelial keratoplasty. Cornea. 2011;30(12):1485-1487.
2. Baudouin TL, Bouheraoua N. Interface fluid syndrome after SMILE surgery. J Fr Ophtalmol. 2021;44(1):e15-e17.).
3. Galal A, Artola A, Belda J, et al. Interface corneal
edema secondary to steroid-induced elevation of intraocular pressure simulating diffuse lamellar keratitis. J Refract Surg. 2006;22(5):441-447.
4. Dawson DG, Schmack I, Holley GP, Waring GO, Grossniklaus HE, Edelhauser HF. Interface Fluid Syndrome in Human Eye Bank Corneas after LASIK. Ophthalmology. 2007;114(10):1848-1859.e1.
5. Goto S., Koh S., Toda R. Interface fluid syndrome after laser in situ keratomileusis following herpetic keratouveitis. J Cataract Refract Surg. 2013;39(8):1267–1270.
6. Jia Z, Zhao S, Wei R, Huang Y, Zhang C, Yang R. Interface fluid syndrome: A potential lifelong complication after LASIK. A case report. Am J Ophthalmol Case Rep. 2018;11:23-25.
7. Shajari M., Rafiezadeh P., Pavlovic I. Management of interface fluid syndrome after LASIK by descemet membrane endothelial keratoplasty in a patient with Fuchs’ corneal endothelial dystrophy. J Refract Surg. 2017;33(5):347–350.
8. Galvis V, Berrospi RD, Tello A, Santaella G. Interface Fluid Syndrome (IFS) following Toxic Anterior Segment Syndrome (TASS): not related to high intraocular pressure but to endothelial failure. Saudi J Ophthalmol. 2019;33(1):88-93.)
9. Ravipati A, Pradeep T, Donaldson KE. Interface Fluid Syndrome after LASIK surgery: retrospective pooled analysis and systematic review. J Cataract Refract Surg. 2023; 49:885–889.
