A clinical case of reimplantation of corneal segments

Objective. To assess the possibility and feasibility of reimplantation of corneal segments, the effect of the height, localization and correct positioning of corneal segments on postoperative visual acuity. Methods. Patient A., 37 years old, first came to the Federal State Autonomous Institution "National Medical Research Center "MNTK "Microsurgery of the Eye" named after academician S.N. Fedorov" with complaints of decreased visual acuity. It is known from the anamnesis that in August 2022, a diagnosis of OU grade 2 keratoconus was made in one of the Moscow clinics, and intrastromal keratoplasty with femtosecond assistance was performed on OU there. The best corrected visual acuity (BCVA) at the time of referral was OD 0.2 sph +2.75 cyl -5.5 ax 90 = 0.7; OS 0.3 sph +6.0 cyl -8.0 ax100 = 1.0; intraocular pressure (IOP) OD = 16 mmHg; OS = 12 mmHg. St.loc: the eye is calm, the cornea is transparent, in the stroma there are 2 corneal segments in the correct position. Other structures are within normal limits. The patient underwent optical coherence tomography (OCT) of the anterior segment (OCT Visante), keratotopogram. According to the diagnostic data, inversion of both corneal segments was detected, ectasia resembling pellucid marginal degeneration was noted on the keratotopogram, but it is impossible to accurately determine the type of ectasia, since the topogram was made with segments already implanted. Recommendation: selection of scleral contact lenses and a follow-up examination in 1 year with repeated diagnostics. A year later, the patient came for a follow-up examination with the same complaints. BCVA at the time of treatment (no deterioration was noted when compared with BCVA at the initial treatment): OD 0.2 sph +2.75 cyl –5.5 ax 90= 0.7; OS 0.3 sph +6.0 cyl –8.0 ax 100 = 1.0; IOP OD = 16 mm Hg, OS = 12 mm Hg. St. loc: the eye is calm, the cornea is transparent, in the stroma there are 2 corneal segments in the correct position. The remaining structures are within normal limits. We repeated the Visante OST and keratotopogram. No changes were found over the year. Recommended: since the patient came to us with an already established diagnosis of "keratoconus", knowing its average statistical forms, we assumed that the segments were in the wrong orientation and along the wrong axis, in connection with which it was decided to reimplant the segments in two stages with a 2-week break in order to close the old tunnels and create new ones for implantation of higher segments. After removal of the segments, no significant changes in visual acuity were noted: OS 0.04–0.05 sph +3.5 cyl –7.5 ax 110 = 0.85. After 2 weeks, we performed a repeat Visante OCT and saw that the tunnels were closed. According to the keratotopogram, the protrusion zone is above the minimum thickness zone, the "crab claw" pattern is signs of pellucid marginal degeneration, although the patient came to us with established keratoconus of the 2nd degree. Reimplantation of corneal segments with creation of new tunnels using a femtosecond laser with integrated OCT at a depth of 375 μm. 2 segments: 350 μm in the zone of greater ectasia and 200 μm in the zone of lesser ectasia with an arc length of 180°. The next day, Visus is OS 0.7 n/c (not corrected). Results. The cylinder and sphere are completely corrected, high BCVA. Conclusions. Reimplantation of corneal segments is possible. The final refractive result is affected by the localization of corneal segments, correctly selected height, correct orientation of the segments. Key words: corneal segments, intrastromal keratoplasty, segment inversion, scleral contact lenses