Superficial lamellar keratectomy using an automated microkeratome to excise corneal scarring caused by photorefractive keratectomy

Superficial Keratectomy: A Review of Literature

Superficial keratectomy (SK) is the manual dissection of the superficial corneal layers (epithelium, Bowman's layer, and sometimes superficial stroma). SK is done using a surgical blade or diamond burr. Some surgeons use intraoperative mitomycin C 0.02% or amniotic membrane transplantation to improve surgical outcomes. This literature review shows that SK remains an effective method for different indications, including tissue diagnosis, excision of corneal degenerations, dystrophies, scarring, recurrent corneal erosions, and retained corneal foreign body.

Use of automated central lamellar superficial keratectomy in the treatment of chronic pigmentary superficial keratitis in dogs

ABSTRACT Pigmentary superficial keratitis (PSK) is a chronic corneal disorder with different causes, which may include immune-mediated diseases and reactions to ultraviolet rays. This study aimed to evaluate the use of automated central lamellar superficial keratectomy (ACLSK) in the treatment of chronic pigmentary superficial keratitis (CPSK) in dogs. We enrolled 24 animals with CPSK and loss of visual function even after clinical treatment with preserved post-corneal transparent media, and the potential for recovery of visual function after surgical treatment. The microkeratome was positioned on the eye surface, and the central corneal lamellae were obtained after translation. With ACSLC, 21 animals (87.5%) recovered their visual function. In 3 animals (12.5%), the formation of granuloma and posterior central leukoma in the cornea compromised the transparency of the visual axis. This study concludes that ACLSK is a viable surgical alternative for the restoration of visual function in dogs with severe PSK, thus improving their quality of life. The short execution time of this procedure reduces the costs and anesthetic risks.

Corneal epithelial debridement for diagnosis and therapy of ocular surface disease

BACKGROUND

There is a wide range of ocular surface conditions that can be diagnosed or treated with epithelial debridement. The purpose of this study is to analyse the indications, instrumentation and outcomes of corneal epithelial debridement for anterior segment pathology.

METHODS

One hundred and thirty-three eyes of 129 patients with ocular surface disease were treated with epithelial debridement. Different methods were used, appropriate to the specific disease, aetiology and outcome measure.

RESULTS

The mean patient age was 56 years and 81 (60.9 per cent) were male. Sixty-two eyes (46.6 per cent) were undertaken for diagnosis and 71 (53.4 per cent) for therapy. Common indications for diagnostic corneal debridement included infective keratitis 48 (36.1 per cent), neoplasia 14 (10.5 per cent), while those for therapeutic corneal debridement included recurrent erosion 30 (22.5 per cent) and band keratopathy 16 (12.0 per cent). The most common post-operative complication was pain, occurring in all patients to some extent. Band keratopathy was seen to recur in two (12.5 per cent) of the treated eyes and there was a single relapse of recurrent erosion during the follow-up period.

CONCLUSION

The techniques presented can be undertaken in the office rather than a day procedural unit, improving time and cost-effectiveness for the ophthalmologist and patient.

Management of corneal scarring secondary to explosion with excimer laser treatment

BACKGROUND

Improper use of pyrotechnics can result in ocular injuries producing severe vision loss.

CASE

A 20-year-old man had a pyrotechnics device explode in his face, hospitalizing him for 4 days. He was told he needed a corneal transplant and that his vision would be impaired permanently. As an alternative, phototherapeutic keratectomy was performed on each eye to remove as much scar tissue as possible. Photorefractive keratectomy was then used to treat the residual hyperopia and remove more of the scarring.

CONCLUSIONS

The combination of phototherapeutic keratectomy/photorefractive keratectomy proved to be a safe and effective method to treat corneal scarring secondary to explosive trauma and to restore normal vision.

Automated superficial lamellar keratectomy augmented by excimer laser masked PTK in the management of severe superficial corneal opacities

AIM

To assess superficial lamellar keratectomy augmented by excimer laser smoothening with sodium hyaluronate 0.25%, for the management of superficial corneal opacities.

METHODS

Consecutive procedure performed in 14 eyes (13 patients) with an automated microkeratome and excimer laser phototherapeutic keratectomy (PTK) smoothening using sodium hyaluronate 0.25%.

MAIN OUTCOME MEASURES

UCVA, BCVA, pachymetry, degree of haze, ray tracing analysis, and complications. Mean follow up was 12 (SD 1.6) months.

RESULTS

Mean preoperative haze from previous corneal refractive surgeries was 3.5 (SD 0.5) (11/14 cases). In one case, opacity was caused by ocular trauma and in two by infectious keratitis. The mean preoperative UCVA was 0.7 logMAR (0.2 (SD 0.13) decimal value). BCVA was 0.4 logMAR (0.4 (SD 0.17) decimal value). Mean preoperative corneal pachymetry was 508 (SD 62.5) micro m and mean opacity depth measured by corneal confocal microscopy was 115.2 (SD 49.4) micro m. At 6 months, 71.4% of the eyes with previous corneal refractive surgery showed grade I haze or less. Mean postoperative corneal pachymetry at 6 months was 352.36 (SD 49.05) micro m.

CONCLUSIONS

Automated superficial lamellar keratectomy combined with excimer laser PTK smoothening assisted by sodium hyaluronate 0.25% induces a significant improvement of corneal transparency and visual acuity in cases of corneal opacity caused by previous refractive surgery, ocular trauma, and keratitis.

Lamellar Keratectomy Using an Automated Microkeratome

PURPOSE

To evaluate the effectiveness of treating anterior corneal pathology by performing a superficial lamellar keratectomy with an automated microkeratome.

METHODS

Retrospective chart review of 10 eyes (8 patients) seen in a subspecialty referral practice for anterior segment disease. With the use of an automated microkeratome, a lamellar flap was created, which was then surgically excised.

RESULTS

Ten eyes of eight patients were followed for a mean of 5.4 months (range, 4 to 10 months). Subjective visual acuity and/or sensation of ocular irritation improved in 10 of 10 eyes. Mean improvement in Snellen best-corrected visual acuity was 1.8 lines (range, -1 to +3 lines). One patient lost 1 line of Snellen acuity due to progression of a posterior subcapsular cataract. Mean change in spherical equivalent was +0.5 diopters (range, -1.60 to +4.25 diopters), and mean improvement in corneal clarity (1 to 4 scale) was 1.8. Mean preoperative pachymetry was 589.0 microm (range, 507 to 741 microm). Mean postoperative pachymetry was 461.3 microm (range, 370 to 564 microm). Recurrence of pathology (band keratopathy and Salzmann's nodular degeneration) occurred in two patients. In one patient, immunohistochemical staining of corneal tissue from the lamellar dissection confirmed the diagnosis of herpes simplex virus type 1 stromal keratitis, improving the course of postoperative care.

CONCLUSION

Lamellar keratectomy with the use of an automated microkeratome is a safe and effective method for removing superficial anterior corneal opacities. For selected cases, it offers specific advantages over other surgical modalities. In particular, this procedure may induce far less hyperopic shift than would the equivalent amount of tissue removal by performing excimer laser phototherapeutic keratectomy.

Phototherapeutic keratectomy with amniotic membrane for severe subepithelial fibrosis following excimer laser refractive surgery

We report 2 patients who developed subepithelial opacities and myopic regression after photorefractive keratectomy (PRK) and laser-assisted subepithelial keratectomy. Both cases were treated successfully with manual debridement of the epithelium, phototherapeutic keratectomy, and PRK with amniotic membrane application.

Corneal lenticule harvest using a microkeratome and an artificial anterior chamber system at high intrachamber pressure

PURPOSE

To evaluate the safety and accuracy of a manual microkeratome and an artificial anterior chamber used at high intrachamber pressure to harvest corneal lenticules for lamellar keratoplasty.

SETTING

Department of Ophthalmology, University of California, Irvine, California, USA.

METHODS

Forty-seven human eye-bank corneoscleral rims were mounted on an artificial anterior chamber. A manual microkeratome was used to perform lamellar keratectomy at a mean intrachamber pressure of 95.8 mm hg +/- 4.8 (sd). Two thicknesses (300 microm and 360 microm microkeratome heads) and diameters (8.0 mm and 9.0 mm) were attempted, and the resultant lenticules were analyzed by pachymetry and digital photography.

RESULTS

In the 9.0 mm/360 microm group, corneal perforation occurred in 12 of 17 lenticules (71.2%). Except for this group, 24 of 30 corneas (80.0%) showed a less than 0.5 mm deviation from the expected diameter. Neither the horizontal nor the vertical diameter differences were statistically significant (P >.05). The difference between the horizontal and vertical diameters was within +/-0.2 mm in 23 corneas (76.7%). Three (10.0%) corneal beds contained a slightly uneven keratectomy margin.

CONCLUSIONS

This system provided accurate and smooth lenticules for lamellar keratoplasty. The precision and accuracy of the obtained corneal lenticules were better than those in previous reports. However, the 9.0 mm diameter/360 microm thickness head with high intrachamber pressure should not be applied in the clinical setting without further testing. In this laboratory study, a minimal corneal thickness of 588 microm was required to avoid perforation.

Evaluation of a microkeratome-based limbal harvester device for limbal stem cell transplantation

PURPOSE

To assess the cut quality and reproducibility using a novel microkeratome-based limbal harvester.

METHODS

An enlarged microkeratome head and stainless steel blades were coupled with a nitrogen gas-driven turbine (15,000 blade oscillations/min) of a microkeratome. A large, 16-mm-diameter suction ring was attached to the globe. A lamellar sclerokeratectomy using head depths of 170 and 200 microm was performed in human donor research eyes. Obtained lenticule thickness was measured by ultrasound pachymetry and the bed size by planimetry. Histologic and scanning electron microscopy (SEM) analyses of the samples were performed.

RESULTS

Central lenticule thickness was 294 microm (standard deviation [SD] 37) for the 170 head and 277 microm (SD 91) for the 200 head (p = 0.720). Lenticule diameter was larger in the horizontal meridian using the 170 head (12.8 mm [SD 0.8] vs. 11.9 mm [SD 0.7], p = 0.028), but similar in vertical meridian (12.0 [SD 0.6] versus 11.4 mm [SD 0.6], p = 0.093). Histology showed a multilayer epithelial cell pattern at the lenticule periphery. The SEM showed a smooth cut surface in both the stromal bed and the lenticule.

CONCLUSION

Cut reproducibility and quality are similar to those found using standard microkeratomes for corneal lamellar cuts. This system ensures, in a straightforward way, the presence of epithelial cells in the edges of a mechanical sclerokeratectomy for limbal stem cell transplantation.

The evolution of lamellar keratoplasty

Recent advancements in lamellar keratoplasty have two aspects: the refinement in surgical technique, which has improved postoperative visual outcomes and the transplantation of specific tissues of the donor cornea, such as limbal stem cells. Stem cell transplantation has expanded dramatically as a method of ocular surface reconstruction. Long-term prognosis for limbal allograft transplantation has recently been reported, and postoperative treatments including epithelial management and immunosuppression are now major topics to be studied.