Epikeratophakia for aphakia, keratoconus, and myopia

Clinical outcomes in post-epikeratophakic eyes after removal of epikeratoplasty lenticule

Background

Assessment of the optical outcome and adverse events in post-epikeratopathic eyes after removal of the epikeratoplasty lenticule (EKPL).

Methods

This was a retrospective case-series study of patients who underwent EKPL removal between 2002 and 2020. Ten eyes were included in the analysis. We compared the clinical characteristics of the patients before surgery, 6 months after surgery, before lenticular removal, and after removal, and reported optical or ocular surface complications.

Results

We removed EKPL due to the lenticular opacity in five eyes (50%), intraocular lens (IOL) insertion (n = 4, 40%) after cataract surgery (n = 3) or in aphakic eyes (n = 1), and lenticule-induced irregular astigmatism in one eye (10%). After EKPL removal, the mean refractive power of the cornea (Km) revealed a tendency to increase. Out of nine cases, six cases showed corneal steepening and three cases revealed corneal flattening. When the keratometric readings of pre-epikeratoplasty and post-lenticular removal were compared within the same case, the average difference was 5.1 D ± 4.0 (n = 8). Complications were observed in 3 of 10 cases (excessive corneal flatness, ectatic change, and abnormal epithelial cell ingrowth) after removal.

Conclusions

The surgeon should expect the corneal refractive power to steepen or flatten in some cases with abnormal astigmatism and irregularity. Epikeratophakic eyes may exhibit serious ectatic changes, and abnormal epithelial cell ingrowth after removal of epikeratophakic lenticules.

Pneumatic Dissection for Large-Diameter (9-mm) Deep Anterior Lamellar Keratoplasty in Eyes With Previous Anterior Lamellar Keratoplasty

PURPOSE

To evaluate the surgical and 3-year clinical outcomes of modified big-bubble 9-mm deep anterior lamellar keratoplasty (DALK) in eyes with previous ALK (ALK).

METHODS

In this interventional case series, 21 consecutive eyes with unsatisfactory vision after ALK (superficial ALK n = 9; laser-assisted ALK n = 7; and epikeratophakia n = 5) underwent large-diameter (9-mm) DALK. The surgery involved deep trephination based on the anterior segment optical coherence tomography pachymetry measurement at 9-mm diameter, pneumatic dissection from the base of the trephination and limited stromal clearance of the optical zone (6 mm). Main outcome measures were success rates of pneumatic dissection, best spectacle-corrected visual acuity, and complication rates.

RESULTS

Pneumatic dissection with type 1 bubble formation succeeded in 19 (90%) eyes. In the 2 remaining cases, the 6-mm optical zone was cleared by manual dissection. Perforation occurred in one of the latter cases; no procedure was converted to penetrating keratoplasty. One month after complete suture removal, the preoperative mean best spectacle-corrected visual acuity (0.75 ± 0.23 logMAR) improved to 0.09 ± 0.10 logMAR (P < 0.001) and remained stable up to 3 years after surgery. At the final follow-up, refractive astigmatism was ≤4.5 and <6 D in 20 (95%) and 21 (100%) eyes, respectively. Stromal rejection was observed in 2 eyes (10%) and was treated successfully with steroids.

CONCLUSIONS

Even in eyes with previous ALK, pneumatic dissection can be achieved through a modified DALK technique with a low risk of complications and excellent visual and refractive outcomes.

Ophthalmic use of blood-derived products

There is a wide spectrum of blood-derived products that have been used in many different medical and surgical specialties with success. Blood-derived products for clinical use can be extracted from autologous or allogeneic specimens of blood, but recombinant products are also commonly used. A number of blood derivatives have been used for a wide range of ocular conditions, from the ocular surface to the retina. With stringent preparation guidelines, the potential risk of transmission of blood-borne diseases is minimized. We review blood-derived products and how they are improving the management of ocular disease.

Ten-year follow-up of epikeratophakia for the correction of high myopia

OBJECTIVE

To determine the long-term functional results of epikeratophakia for myopic patients.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Twenty-two patients (32 eyes; average age, 43+/-6 years) who underwent epikeratophakia surgery for high myopia. Mean preoperative myopia was -18.74+/-9.16 diopters (D; range, -7 D to -49 D). Follow-up was 12+/-2 years.

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), change in mean keratometry, visual acuity under glare conditions, BCVA versus potential acuity meter reading, and patient satisfaction with the visual outcome.

RESULTS

Mean preoperative UCVA increased from 20/800+/-20/400 (range, counting fingers-20/400) to 20/80+/-20/200 (range, 20/250-20/32) in 24 eyes. Mean preoperative BCVA of 20/32+/-20/64 increased only in five eyes, whereas six eyes had no change and 18 eyes had a more than one line loss of Snellen BCVA. Mean preoperative keratometry reading decreased from 43.67+/-0.90 D (range, 41.0-46.25 D) to 37.40+/-2.92 D (range, 29.43-47.68 D). In the presence of glare, mean BCVA decreased to 20/100+/-20/100 (range, counting fingers-20/32). Potential acuity meter (PAM) readings were significantly (P<0.05) higher than BCVA. Mean PAM reading was 20/25+/-20/100 (range, 20/100-20/16). Seven patients (11 eyes) were extremely satisfied with the operative result more than 10 years after the operation, whereas four patients (four eyes) were not satisfied at all.

CONCLUSIONS

Epikeratophakia for the correction of myopia improved UCVA significantly, but BCVA decreased. The removal of the lenticules in patients who were not satisfied with their visual acuity was uncomplicated, and acceptable vision could be achieved with either contact lenses or intraocular lens implantation.

Advances in refractive surgery: 1975 to the present

PURPOSE

To review the major advances in the field of refractive surgery occurring over the past 25 years.

METHODS

Literature review.

RESULTS

The major developments in refractive surgery over the past 25 years are reviewed.

CONCLUSIONS

The past 25 years have witnessed great changes in refractive surgery. As a result of advancements in technology, instrumentation, and technique, we have seen improvements in the treatment of all types of ametropias. In this article, we review some of the successes and failures of the past quarter-century.

The future of lamellar keratoplasty

New surgical techniques in lamellar keratoplasty, including phototherapeutic keratectomy, automated lamellar keratectomy, plano-epikeratoplasty, deep anterior lamellar keratoplasty, combined amniotic membrane and limbal transplantation, large-diameter corneoscleral lamellar keratoplasty, and posterior lamellar keratoplasty, have recently become available. These procedures broaden the array of treatments for corneal disorders and may be used as alternatives to penetrating keratoplasty.

Long-term outcome of epikeratophakia

PURPOSE

To assess the long-term outcome of epikeratophakia.

SETTING

National center for pediatric ophthalmology (The Children's Hospital) and ophthalmology department in a regional general hospital (Waterford Regional Hospital), Republic of Ireland.

METHODS

A retrospective clinical review was carried out of 25 eyes (20 patients) with epikeratophakia performed over 10 years. Eyes were assigned to a children's group (Group 1) or an adult group (Group 2), depending on patient age at the time of surgery, and assessed with respect to indication for surgery, visual acuity, condition of the implanted lenticule, complications, refraction, and corneal topography. Histological analysis was performed on 1 removed lenticule.

RESULTS

Mean follow-up of all patients was 7.3 years (median 6.8 years; range 4.0 to 10.0 years). Most eyes (n = 18) were contact lens intolerant. Freeze-dried lenticules were implanted in all cases, and all but 1 had stable visual acuity from the early postoperative period to last follow-up. In Group 1 (n = 10), most eyes had a visual acuity of 6/36 or worse preoperatively with an improvement of 1 or more lines in 4 eyes. In Group 2 (n = 14), at last follow-up most eyes retained good or improved visual acuity by 1 or more lines. Most grafts were clear or had insignificant opacities outside the visual axis. The overall complication rate was 12%, with the most serious complication being significant induced astigmatism requiring removal of 1 epigraft. Mean induced astigmatism was 2.50 diopters (D) (median 2.00 D; range 1.00 to 6.00 D), which was accurately predicted within +/- 1.00 D by corneal topography in 14 of 19 eyes. Histology demonstrated infiltration of the implanted lenticule by host keratocytes.

CONCLUSION

Epikeratophakia, a reversible procedure with a low complication rate, resulted in stable visual acuity with good lenticule condition and minimal induced regular astigmatism after long-term follow-up.

Viability of keratocytes in epikeratophakia lenticules

AIM

To study the influence of cryoprotectant, cooling rate, and warming rate on recovery and viability of keratocytes from corneas for cryolathing.

METHODS

Corneas were frozen at -50 degrees C for 2 minutes either after exposure to 10% dimethyl sulphoxide in Eagle's MEM for 15 minutes at room temperature (about 22 degrees C), or without earlier exposure to the cryoprotectant. Corneas were cooled either rapidly (20 degrees C/min) or slowly (1 degree C/min), and they were warmed either rapidly (> 50 degrees C/min) by direct transfer into medium at 22 degrees C or slowly (< 20 degrees C/min) in air at 22 degrees C. The cryoprotectant was removed by dilution in medium containing 0.5 mol/l sucrose. Recovery of keratocytes was determined by using collagenase digestion to release the cells from the stroma and trypan blue staining. Viability was assessed by the outgrowth of cells from stromal explants in primary tissue culture.

RESULTS

The use of a cryoprotectant before freezing was beneficial, irrespective of the different cooling and warming regimens. Both collagenase digestion and tissue culture revealed that keratocyte survival was improved when corneas were warmed rapidly rather than slowly. The collagenase digestion assay showed an apparently higher recovery of keratocytes after slow cooling (54.3%) than after rapid cooling (34.1%), but no differences in cell viability could be demonstrated by primary tissue culture.

CONCLUSION

Although in these experiments slow cooling apparently provided the best recovery of keratocyte numbers (though not viability), previous work had revealed some disruption of the epithelial basement membrane after slow cooling. If viable keratocytes and good preservation of epithelial basement membrane are considered to be prerequisites for epikeratophakia lenticules then it is suggested that corneas should be prepared for cryolathing by freezing rapidly after exposure to 10% dimethyl sulphoxide and, following cryolathing, they should be warmed rapidly.

Improved preservation of human corneal basement membrane following freezing of donor tissue for epikeratophakia

Current methods for the production of lenticules for epikeratophakia involve rapid freezing, cryolathing, and slow warming of the donor cornea. We have found that this procedure causes structural damage to the epithelial basement membrane in the donor cornea which may subsequently contribute to poor postoperative re-epithelialisation of the implant, leading to graft failure. Endeavouring to overcome these problems, the effects of cryoprotection of donor cornea were investigated, using dimethyl sulphoxide, in conjunction with different cooling and warming rates as part of the protocol for cryolathing. The structural integrity of the epithelial basement membrane zone (BMZ) was then assessed by electron microscopy and by immunofluorescence microscopy using antibodies to types IV and VII collagen, components of the basal lamina and anchoring fibrils respectively, and an antibody to a component of the anchoring filaments. No differences in the pattern of immunostaining for these components were detected, indicating that the composition of the BMZ was unaltered by the different treatment regimens applied. However, electron microscopy showed that preservation of basement membrane ultrastructure was markedly improved when cornea was warmed rapidly rather than slowly, both in cryoprotected and non-cryoprotected tissue. Epithelial cell retention and preservation of stromal architecture appeared superior in cryoprotected samples, while keratocyte structure was heterogeneous throughout the experimental groups. Further work is in progress to assess the efficacy of these protocols in the preservation of keratocyte viability in association with improved basement membrane structure in donor tissue for epikeratophakia.

Long-term results of myopic epikeratoplasty

Twenty-three eyes of 20 patients who had had myopic epikeratoplasty were evaluated and the mean 21-month postoperative results (range: 12 to 47 months) tabulated. Average preoperative myopia was -16.7 diopters (D) spherical equivalent (range: -10 to -33 D), and average postoperative refractive correction was 13 D. Of 22 eyes, 17 eyes (77%) were within 4 D of emmetropia. Preoperative visual acuities without correction were between 2/200 and 20/100 (average = 2/40); postoperative acuities were between 2/200 and 20/20 (average = 20/40). Average preoperative best corrected visual acuity was 20/30. Best corrected visual acuities were unchanged or improved in 82% of cases. Re-epithelialization was complete within an average of seven days (range: three to 16 days) postoperatively except in one case in which the lenticule was removed because re-epithelialization did not occur. Five cases showed progressive loss of lenticular power.

Visual performance after aphakic epikeratoplasty

While good visual acuity and refractive results after epikeratoplasty for aphakia have been reported, particularly for adults and older children, limited detailed information on the nature of the resulting vision is available. We have evaluated the visual performance of seven aphakic subjects corrected by epikeratoplasty by measuring contrast sensitivity, with and without the presence of glare. These results were compared with those for other aphakic corrections, namely spectacles (n = 5 eyes), contact lenses (n = 5 eyes), or intraocular lens implantation (n = 5 eyes). There were statistically significant differences among these four aphakic correction types (p = 0.0330), with a consistent trend for diminished visual performance after epikeratoplasty. Threshold elevations occurred in the presence of glare, but they were not statistically different between the groups (p = 0.1631). Based on these visual assessments, epikeratoplasty does result in statistically significant visual losses. Despite this, it may still offer an acceptable alternative to other managements of the aphakic patient when those others are contraindicated.

The success of penetrating keratoplasty for keratoconus

We report the results, over a 20 year period up to 1989, of 201 penetrating keratoplasties in 198 eyes of 158 patients. The five year graft survival was 97%. A corrected visual acuity of 6/12 or better was attained by 91%. The mean spherical equivalent refraction on removal of sutures was -2.68 Ds and the mean cylindrical correction was -5.56 Ds. The cumulative time to dispensing final refractive correction was 38 months for 90% of patients. Rejection episodes occurred in 20% of grafts and were associated with loosening of sutures and bilateral grafts. Atopic patients (28%) were not at greater risk from rejection. Graft refractive surgery was undertaken in 18% and, of these, 55% achieved 6/12 vision or better with an refractive correction which could be dispensed and tolerated within 6 months.