A prospective multicenter trial of excimer laser phototherapeutic keratectomy for corneal vision loss. The Summit Phototherapeutic Keratectomy Study Group

Excimer Laser Phototherapeutic Keratectomy for Anterior Corneal Opacification After Descemet Membrane Endothelial Keratoplasty

PURPOSE

The aim of this study was to assess the long-term outcome of excimer laser phototherapeutic keratectomy (PTK) for treating remaining anterior corneal opacities after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

This cohort study analyzed 67 eyes of 66 patients undergoing PTK in addition to and after DMEK between 2012 and 2021 at the Department of Ophthalmology, University of Cologne. Patients who were treated by PTK after previous DMEK on the same eye were included. The outcome parameters were best corrected visual acuity (BCVA), changes in refraction, endothelial cell density, corneal densitometry, central corneal thickness, and total corneal higher order aberrations. Patients with visual limitations in addition to anterior opacification were analyzed separately for their visual outcome. Eyes with severe visual limitations that have a very limited visual potential were excluded from the study. In addition, patients with not at least 1 postoperative follow-up examination were excluded from the study.

RESULTS

In this study, 67 eyes of 66 patients met all inclusion criteria. The median follow-up period was 13.1 (quartiles: 4.1; 30.7; interquartile range 26.6) months. The mean (±SD) BCVA improved from (logarithm of the minimum angle of resolution) 0.54 (±0.32) to 0.38 (±0.27) at the first postoperative visit ( P < 0.001) and remained significantly improved at all follow-up examinations compared with preoperative BCVA. Refraction and endothelial cell density did not change significantly after PTK. There was a significant decrease in corneal backscatter in the anterior corneal layer ( P < 0.001), and the total higher order aberration ( P = 0.02) and central corneal thickness were significantly reduced at the most recent postoperative visit ( P < 0.001). No immune reactions were observed.

CONCLUSIONS

Excimer laser PTK after DMEK for persisting anterior corneal opacities has the potential to significantly improve patients' vision without affecting refractive parameters or endothelial cell density.

The effect of EDTA solution on corneal endothelial cells in rabbits

Corneal disease threatens vision globally. Among corneal diseases, calcific band keratopathy has severe effects on vision owing to its unique location. Currently, ethylene diamine tetraacetic acid (EDTA) chelation remains the most important treatment. However, only the safety of low-dose topical EDTA eye drops is well established in humans. Therefore, the purpose of this study was to determine the safe dose range of EDTA for calcific band keratopathy surgery and its toxic effects on rabbit eyes. Rabbits were administered different doses of EDTA solutions (0.50, 0.20, 0.10, 0.05, and 0.01 M) for twenty minutes. In day seven, the rabbits were euthanized and pathological examination was performed for cornea. We found severe corneal edema in 0.50 M group, while milder edema in lower-concentration treated groups. Followed by corneal thickness measurement, the measured values increase to the peak in post-operative three day (0.20 M group) or one day (lower-concentration groups), then decreased. Groups comparison shown significant difference between BSS control group and higher concentration groups (0.20 M and 0.10 M) (P < 0.001) in observation period, but no significance was observed between low concentration and control group in the day seven after surgery (P > 0.05). Confocal microscopy examination suggested, the number of corneal endothelial cells significantly decreased from 3428.6 ± 180.3 cells/mm² to 2808 ± 80.6 cells/mm² in the 0.50 M group, while the lower-concentration groups showed lesser toxic effects on corneal endothelial cells. Finally, our histological examination demonstrated inflammation in each experimental group and dose-dependent, compared with control group. Our study found 0.05 M and 0.01 M EDTA solutions had no obvious toxic effect on the corneal endothelium compared with higher concentration. However, further study of EDTA side effect by clinical trials, and therapeutic effect observation with different concentration are necessary.

Hyperopia-Correcting Phototherapeutic Keratectomy and Its Comparison With Conventional Phototherapeutic Keratectomy

Purpose

To evaluate hyperopia-correcting phototherapeutic keratectomy (HC-PTK) and to compare the visual and refractive outcomes of HC-PTK and conventional PTK.

Methods

This study comprised a total of 72 eyes of 72 consecutive patients who underwent HC-PTK and conventional PTK for granular corneal dystrophy or band-shaped keratopathy. Preoperatively and 6 months postoperatively, we assessed visual acuity, manifest refraction, and mean keratometry, as well as postoperative corneal higher-order aberrations and adverse events in each PTK group, and compared these metrics between the two groups.

Results

LogMAR BSCVA significantly improved from 0.43 ± 0.47 preoperatively to 0.21 ± 0.38 postoperatively in the HC-PTK group (Wilcoxon signed-rank test, p < 0.001). It was also significantly improved from 0.22 ± 0.21 preoperatively to 0.15 ± 0.12 postoperatively in the conventional PTK group (p = 0.031). Mean refraction significantly changed from 0.27 ± 1.55 diopter (D) preoperatively to 0.50 ± 1.77 D postoperatively, in the HC-PTK group (p = 0.313). By contrast, it was significantly hyperopic from −0.15 ± 2.41 D preoperatively to 1.45 ± 2.46 D postoperatively, in the conventional PTK group (p < 0.001). No significant complications occurred in any case during the follow-up period.

Conclusion

Both HC-PTK and conventional PTK showed a significant improvement of BSCVA and no vision-threatening complications at any time in this series. HC-PTK significantly reduced a hyperopic shift in refraction compared with conventional PTK, suggesting its viability for patients requiring PTK, especially in consideration of preventing this hyperopic issue.

Phototherapeutic keratectomy: Indications, methods and decision making

Phototherapeutic keratectomy (PTK) involves treating anterior corneal lesions by superficial corneal ablation using an excimer laser (193 nm). Some of the commonly treated conditions include recurrent corneal erosions (RCE), corneal dystrophies, spheroidal degeneration, keratoconus, and corneal scars. We discuss various techniques of PTK including large area PTK, focal PTK, and multifocal PTK and alternatives to PTK. Masking agents like hyaluronate, methylcellulose, and dextran are recommended to help achieve a better outcome when ablating irregular corneal surfaces. Antifibrotic agents like mitomycin C reduce the chances of recurrence of the disease, apart from minimizing the postoperative scarring. Some of the complications include induced hyperopia and irregular astigmatism, haze, recurrence, and corneal thinning. However, earlier postoperative recovery, possibility of a repeat procedure, and ability to control the depth of ablation make PTK a promising, minimally invasive alternative to keratoplasty in cases with anterior corneal pathologies.

Transepithelial Surface Ablation With Mitomycin C for the Treatment of Chronic Central Corneal Scars Following Adenoviral Keratoconjunctivitis

PURPOSE

To assess visual and refractive outcomes and recurrence rates of subepithelial infiltrates after corneal surface ablation with mitomycin C (MMC) 0.02% for the treatment of chronic corneal scars following epidemic keratoconjunctivitis and to compare these results with a control group receiving only medical treatment.

METHODS

This was a retrospective case series enrolling patients with central corneal scars following epidemic keratoconjunctivitis. Patients were divided into two groups: (1) control with clinical follow-up and refractive correction with glasses or rigid gas-permeable contact lenses when necessary and (2) transepithelial phototherapeutic keratectomy (PTK) with MMC 0.02%, combined with photorefractive keratectomy (PRK) in selected cases (treatment group). Signs and symptoms, corrected distance visual acuity (CDVA) in logMAR units, manifest and cycloplegic refraction, and depth of the corneal opacities were assessed.

RESULTS

Thirty-five eyes of 27 patients (11 men [40.7%] and 16 women [59.3%]) were enrolled, with a mean follow-up of 54.4 ± 19.7 and 27.5 ± 22.8 months in the control and treatment groups, respectively. Mean improvement in CDVA was 0.13 ± 0.17 logMAR (P = .007) in the control group and 0.29 ± 0.24 logMAR (P = .001) in the treatment group. Intergroup comparison showed a greater improvement in the treatment group (P = .041). Mean hyperopic shift induced in the treatment group was +0.46 ± 1.20 diopters. The recurrence rate of subepithelial infiltrates was 77.7% in the control group and 11.7% in the treatment group throughout the follow-up (54.4 ± 19.7 and 27.5 ± 22.8 months, respectively).

CONCLUSIONS

Corneal surface ablation with MMC 0.02% was efficient in treating corneal scars following adenoviral epidemic keratoconjunctivitis, with greater visual improvement in comparison to clinical treatment and a decreased rate of infiltrate recurrence. [J Refract Surg. 2020;36(1):55-61.].

Salzmann nodular degeneration: prevalence, impact, and management strategies

Purpose

This review will summarize the clinical and histological presentation of Salzmann nodular degeneration (SND), its prevalence and risk factors, potential underlying mechanisms, diagnostic tools, management options, and impact on cataract surgery and co-morbid ocular surface diseases.

Method

PubMed review of 44 articles published between 1976 and 2018.

Results

SND is a corneal disease characterized by whitish gray or bluish nodules on the peripheral or central cornea. The clinical presentation of SND is variable and the nodules can be asymptomatic or cause foreign body sensation and/or blurred vision. Histologically, SND appears as subepithelial nodules with thin overlying epithelium, disrupted or absent Bowman’s layer, and activated fibroblasts within the nodule. SND pathogenesis is not fully understood but is thought to involve poor epithelial protection and disruption of the epithelial–stromal interface, allowing for penetration of epithelially derived growth factors into the stroma and subsequent activation of stromal fibroblasts, eventually leading to sub-epithelial deposition of disorganized extracellular membrane components. SND most commonly occurs in Caucasian females in a bimodal distribution, occurring in the fifth or eighth and ninth decades of life. Risk factors for SND include ocular surface diseases and surgery. Surgical intervention is recommended in individuals with symptomatic nodules – primarily superficial keratectomy performed with or without intraoperative mitomycin C, photokeratectomy, and/or amniotic membrane transplantation. These procedures have been successful in removing the lesion and reducing corneal irregularity, but have variable recurrence rates (0–31%).

Conclusion

The pathogenesis of SND is complex and multifactorial. Advances in diagnostic and treatment modalities have allowed for earlier and more accurate diagnosis and effective treatment of SND.

Phototherapeutic keratectomy

Phototherapeutic keratectomy is an excimer laser-based surgical procedure widely performed by corneal surgeons for treating anterior corneal stromal pathologies. Phototherapeutic keratectomy helps by ablating the corneal stroma, thereby improving corneal clarity and smoothening the surface. Transient discomfort and induced hyperopia from corneal flattening are the immediate postoperative concerns. The long-term course is often marked by the recurrence of original corneal pathology and corneal haze formation. Phototherapeutic keratectomy, however, allows for repeat stromal ablation for managing recurrences, as the corneal thickness permits, without affecting the outcome of future keratoplasty. Adjunctive methods such as topical mitomycin-C may be additionally used to reduce recurrence rates. Also, various masking agents such as carboxymethyl cellulose, sodium hyaluronate, and dextran are used in eyes with irregular corneal surface to allow for uniform stromal ablation. Overall, phototherapeutic keratectomy has provided corneal surgeons an additional surgical tool, particularly those residing in developing nations where the availability of donor corneal tissue is an important limiting factor.

Clinical outcomes and time to recurrence of phototherapeutic keratectomy in Japan

To assess the indications, outcomes and time to recurrence of phototherapeutic keratectomy (PTK) for anterior corneal pathology.This study involved 714 eyes of 477 consecutive patients (mean age: 66.0 ± 15.2 years; range: 6-101 years) who underwent PTK as the initial surgical intervention for an anterior corneal pathology. In case of each patient, the cornea treated by PTK, followed up by slit-lamp examination and corrected distance visual acuity (CDVA) testing. Main outcome measures included Slit-lamp findings (1), CDVA (2), patients' complaints (3).The mean follow-up period was 44.0 ± 38.8 months (range: 1-156 months).We treated 376 granular corneal dystrophy (GCD) eyes, 238 band keratopathy (BK) eyes, 23 epithelium attachment disorder eyes, 16 gelatinous drop-like corneal dystrophy (GDLD) eyes, 13 lattice corneal dystrophy (LCD) eyes, and 48 eyes with other corneal diseases. The CDVA significantly improved from LogMAR 0.65 ± 0.61 pre PTK to LogMAR 0.26 ± 0.39 post PTK. A 2 or more lines increase of CDVA was observed in GCD eyes (67.8%), BK eyes (49.2%), epithelium attachment disorder eyes (57.1%), GDLD eyes (87.5%), LCD eyes (76.9%), and other corneal disease eyes (60.4%). The recurrence of BK was rare. GCD recurred slowly. Epithelium attachment disorder eyes remitted simultaneously, and recurred comparatively faster.PTK was proved to be a successful therapy for all 6 corneal disease categories. Disease recurrence after PTK differed among the diseases, and surgeons should recognize the different rates of disease recurrence after PTK surgery.

Management of Complex Epithelial Ingrowth After Laser In Situ Keratomileusis Using Fibrin Tissue Glue

OBJECTIVES

To evaluate the efficacy and safety of adjunctive fibrin tissue glue in the treatment of complex epithelial ingrowth after laser in situ keratomileusis (LASIK).

METHODS

A retrospective review was performed of 12 eyes in 12 patients treated for clinically significant epithelial ingrowth after LASIK with mechanical debridement of the ingrowth and placement of fibrin tissue glue. Primary outcome measurements including recurrence of ingrowth, visual acuity, and manifest refraction were evaluated at each postoperative examination. Changes in higher-order aberrometry were also evaluated.

RESULTS

After epithelial ingrowth removal with adjunctive fibrin tissue glue, 11 eyes (91.7%) had no recurrence of ingrowth at the final follow-up examination. Uncorrected distance visual acuity changed from 20/20 or better in 3 eyes (25%) and 20/40 or better in 6 eyes (50%) preoperatively to 20/20 or better in 5 eyes (41.7%) and 20/40 or better in 10 eyes (83.3%) postoperatively. Nine eyes (75%) gained one or more lines of best-corrected distance visual acuity (CDVA). No eyes lost any lines of CDVA. There was no significant change in mean spherical equivalent (P=0.22) or mean cylinder (P=0.26) before and after surgery. Higher-order aberrations also remained stable with no significant change in root-mean-square error, coma, trefoil, and spherical aberration. There were no complications associated with the treatment.

CONCLUSIONS

Adjunctive fibrin tissue glue seems to be a safe and effective treatment for epithelial ingrowth after LASIK. This therapy may be particularly useful in managing challenging cases of complex or recalcitrant ingrowth.

Band Keratopathy: A Modified Treatment

PURPOSE

The surgical treatment of band keratopathy usually consists of abrasion of the corneal epithelium followed by removal of the subepithelial calcium deposits by means of an ethylenediamine-tetraacetic acid (EDTA) solution. In order to reduce the discomfort and pain that occur after corneal abrasion, the authors developed a modified technique that avoids the abrasion of the epithelium.

METHODS

In three patients (four eyes) with long-standing band keratopathy, the epithelium was detached with a 19% ethanol solution and placed gently toward the limbus, a method also used in laser-assisted subepithelial keratectomy (LASEK). After clearing the anterior stroma with EDTA solution, the epithelial flap is unrolled and a bandage contact lens applied.

RESULTS

Postoperative pain was greatly reduced and after removal of the contact lens no pain was reported.

CONCLUSIONS

This modified epithelium-sparing treatment of band keratopathy shows good results while reducing postoperative pain.

Phototherapeutic keratectomy for recurrent granular dystrophy in postpenetrating keratoplasty eyes

Purpose:

The purpose is to assess the clinical and visual outcome after phototherapeutic keratectomy (PTK) procedure in eyes with prior penetrating keratoplasty (PKP) for granular corneal dystrophy (GCD) and the time of performance of repeat PTK for recurrence.

Methods:

PTK was performed for visually significant recurrence: A reduction in best-corrected visual acuity (BCVA) by >2 lines over BCVA before recurrence was considered as visually significant recurrence. Three eyes had amniotic membrane patch performed with PTK. The main outcome measures were a recurrence of GCD, clinical course, and visual outcome. Intervals between repeat PTK procedures were noted.

Results:

Six patients (n = 10 eyes; males: 4, mean age 39 ± 13.97 years) underwent PTK. The mean pachymetry before first PTK was 527.1 ± 34 microns. The mean duration between PKP and first PTK was 85.1 months (range: 37–108 months). Two and three PTK procedures were done for seven and five eyes, respectively. Mean duration between first and second and second and third PTK was 62.12 ± 34.41 and 42.8 ± 13.54 months respectively. The average cut depth was 43.66 ± 19.57, 75 ± 43.30 and 39 ± 19.79 microns after the first, second and third PTK procedures, respectively. All eyes had a corneal haze. Prefirst PTK mean BCVA was 20/200 and improved significantly after the first two PTK procedures to 20/40 and after the third PTK procedure to 20/32 (P < 0.001). Five eyes had hyperopia. One acute graft rejection was managed successfully at 5 months with medical therapy.

Conclusion:

Multiple PTK procedures can be performed safely with improved visual acuity in grafts without compromising graft survival.

Inhibition of recurrence of epithelial ingrowth with an amniotic membrane pressure patch to a laser in situ keratomileusis flap with a central stellate laceration: a case report

BACKGROUND

Surgical lifting and scraping is a well-known treatment for epithelial ingrowth, but treatment for epithelial ingrowth on the centrally perforated laser in situ keratomileusis (LASIK) flap has not been well studied.

CASE PRESENTATION

We present a patient who had epithelial ingrowth to the backside of the flap through a central LASIK flap laceration with a stellate shape. The patient had undergone uncomplicated bilateral LASIK surgery 3 years before the trauma. Because the epithelial ingrowth was suspected during the first visit 2 weeks after trauma, and definite epithelial ingrowth was noted during the additional 2 week observation period, the ingrown epithelial tissue was removed mechanically with a number 15 blade after lifting of the flap 4 weeks after the trauma. An amniotic membrane overlay was applied over the cornea and was sutured tightly to the episclera to firmly press down the flap to the remaining posterior stroma, to prevent growth of the epithelium again to the backside of the flap. At the last follow-up visit, 5 months after surgery, the patient's visual acuity remained stabilized with no sign of recurrent epithelial ingrowth.

CONCLUSION

These results showed that an amniotic membrane patch can be a useful adjuvant in the treatment of epithelial ingrowth, even on the central stellate laceration of the LASIK flap over the visual axis.

Efficacy of Hyperopic Photorefractive Keratectomy Simultaneously Performed With Phototherapeutic Keratectomy for Decreasing Hyperopic Shift

PURPOSE

To investigate the efficacy of hyperopic photorefractive keratectomy (HPRK) that was performed simultaneously with phototherapeutic keratectomy (PTK) with regard to decreasing hyperopic shift.

METHODS

A total of 63 eyes of 47 consecutive patients with granular corneal dystrophy (GCD) or band-shaped keratopathy (BSK) underwent PTK or PTK + HPRK. PTK alone was performed in 40 eyes (20 GCD and 20 BSK), and PTK + HPRK was performed in 23 eyes (15 GCD and 8 BSK). All patients underwent examinations including uncorrected distance visual acuity, corrected distance visual acuity, refractometry, and keratometry before and at 1, 3, and 6 months after PTK. Medical charts were reviewed retrospectively.

RESULTS

Superficial corneal opacity was successfully removed from all eyes, and uneventful reepithelialization was completed within 7 days after PTK or PTK + HPRK. The average uncorrected distance visual acuity was significantly better in the PTK + HPRK group than in the PTK group preoperatively and at 1, 3, and 6 months postoperatively. The corrected distance visual acuities were similar in both groups preoperatively and postoperatively. The hyperopic change in the PTK group was approximately 1.5 diopters, and that in the PTK + HPRK group was almost zero. There were significant differences in the average changes of the spherical equivalent from preoperation between the PTK and PTK + HPRK groups at all postoperative time points.

CONCLUSIONS

Simultaneous performance of PTK and HPRK can effectively reduce hyperopic shift after PTK and is as safe as PTK alone. It is recommended that HPRK be added to PTK to treat eyes in which hyperopic shift is undesirable.

Predicting transepithelial phototherapeutic keratectomy outcomes using Fourier domain optical coherence tomography

PURPOSE

The aim of this study was to use Fourier domain optical coherence tomography to predict transepithelial phototherapeutic keratectomy outcomes.

METHODS

This is a prospective case series. Subjects with anterior stromal corneal opacities underwent an excimer laser phototherapeutic keratectomy (PTK) combined with a photorefractive keratectomy using the VISX S4 excimer laser (AMO, Inc, Santa Ana, CA). Preoperative and postoperative Fourier domain optical coherence tomography images were used to develop a simulation algorithm to predict treatment outcomes. Main outcome measures included preoperative and postoperative uncorrected distance visual acuities and corrected distance visual acuity.

RESULTS

Nine eyes of 8 patients were treated. The nominal ablation depth was 75 to 177 μm centrally and 62 to 185 μm peripherally. Measured PTK ablation depths were 20% higher centrally and 26% higher peripherally, compared with those for laser settings. Postoperatively, the mean uncorrected distance visual acuity was 20/41 (range, 20/25-20/80) compared with 20/103 (range, 20/60-20/400) preoperatively. The mean corrected distance visual acuity was 20/29 (range, 20/15-20/60) compared with 20/45 (range, 20/30-20/80) preoperatively. The MRSE was +1.38 ± 2.37 diopters (D) compared with -2.59 ± 2.83 D (mean ± SD). The mean astigmatism magnitude was 1.14 ± 0.83 D compared with 1.40 ± 1.18 D preoperatively. Postoperative MRSE correlated strongly with ablation settings, central and peripheral epithelial thickness (r = 0.99, P < 0.00001). Central islands remained difficult to predict and limited visual outcomes in some cases.

CONCLUSIONS

Optical coherence tomography measurements of opacity depth and 3-dimensional ablation simulation provide valuable guidance in PTK planning. Post-PTK refraction may be predicted with a regression formula that uses epithelial thickness measurements obtained by optical coherence tomography. The laser ablation rates described in this study apply only to the VISX laser.

Optical coherence tomography-guided transepithelial phototherapeutic keratectomy for the treatment of anterior corneal scarring

PURPOSE

To report the visual and anatomic outcomes of a novel technique for the management of anterior corneal scarring using optical coherence tomography (OCT)-guided transepithelial phototherapeutic keratectomy (transepithelial PTK).

DESIGN

Retrospective, consecutive case series.

METHODS

The charts of 22 patients with anterior corneal scarring associated with irregularities in the Bowman layer who had undergone transepithelial PTK according to a novel protocol were reviewed. The protocol consisted of a preoperative OCT-measured depth-of-treatment calculation, followed by a dual excimer laser treatment profile set to achieve the desired refractive outcome while eliminating or reducing corneal scarring. The primary outcomes were change in best spectacle-corrected visual acuity (BSCVA) and change in corneal topography indices at 4 months after ablation.

RESULTS

BSCVA (in logMAR) improved from a mean of 0.82 (0.61-1.02; 95% confidence interval) preoperatively to a mean of 0.40 postoperatively (0.19-0.61) (P = 0.0070). All patients gained a minimum of 1 line of BSCVA postoperatively. Preoperative and postoperative corneal topographic indices showed significant improvement in corneal cylinder (P = 0.0173) and projected visual acuity (P = 0.0261) but not in the surface asymmetry index (P = 0.0849) or the surface regularity index (P = 0.0543). Postoperative spherical equivalent averaged 0.78 diopters (0.49-1.07) of error from the intended target refractive outcome. No complications were associated with the treatment, and no patients required or desired subsequent treatment with either repeat PTK or with more invasive surgery such as lamellar or penetrating keratoplasty.

CONCLUSIONS

OCT-guided transepithelial PTK using a dual ablation excimer laser profile can provide favorable results as well as predictable refractive outcomes in the treatment of corneal scarring associated with Bowman layer irregularities. Future investigations are warranted to further validate the technique reported in this study.

Diamond burr superficial keratectomy with mitomycin C for corneal scarring and high corneal astigmatism after pterygium excision

Background

The purpose of this paper is to report the successful treatment of corneal scarring and high corneal astigmatism secondary to previous pterygium surgery with diamond burr superficial keratectomy using mitomycin C.

Methods

Four patients with corneal scarring and high corneal astigmatism related to previous pterygium surgery underwent diamond burr superficial keratectomy with application of mitomycin C. Anterior segment photography and corneal topographic analysis were obtained preoperatively and postoperatively in all patients.

Results

Six months after surgery, corneal astigmatism and corneal aberrations were reduced in all patients. A clear cornea was achieved in all cases. No complications were noted during the follow-up period.

Conclusion

Diamond burr superficial keratectomy with application of mitomycin C is a potentially effective and simple procedure for treating patients with corneal scarring and high corneal astigmatism secondary to previous pterygium surgery.

Phototherapeutic keratectomy

Phototherapeutic keratectomy (PTK) is done regularly for anterior corneal diseases such as corneal dystrophies, corneal degenerations, scars, and band-shaped keratopathy. The various indications include both therapeutic and visual. The aim of this article is to discuss the therapeutic indications for PTK, the specific technique pertaining to a specific etiology, the various other procedures like amniotic membrane graft combined with PTK or PTK being done for recurrences in the grafts, and PTK done before cataract surgery when the anterior corneal pathology coexists with the cataract. Post PTK management such as healing of an epithelial defect, use of steroids in the post PTK period, recurrences of primary disease pathology, and infections, will be discussed. Methods of literature search: A Medline search was carried out for articles in the English language, with the keywords, phototherapeutic keratectomy, band-shaped keratopathy, spheroidal degeneration, scars, bullous keratopathy, and corneal dystrophy. The relevant references are mentioned here.

Phototherapeutic keratectomy for the treatment of corneal opacities after epidemic keratoconjunctivitis

PURPOSE

To assess visual results and compare methods of measuring central corneal thickness (CCT) and corneal opacity thickness (COT) in patients with corneal opacities induced by epidemic keratoconjunctivitis (EKC) and treated with phototherapeutic keratectomy (PTK) using low-dose mitomycin C (MMC).

DESIGN

Prospective consecutive case series.

METHODS

Patients with chronic adenoviral corneal opacity underwent transepithelial PTK with MMC 0.002% for 1 minute. The presence of photophobia, the best spectacle-corrected visual acuity (BSCVA), and the contrast sensitivity were evaluated. CCT measurements were obtained with ultrasound pachymeter (US), ultrasound biomicroscopy (UBM), Scheimpflug tomography (Pentacam Oculus), and optical coherence tomography (OCT Visante). COT measurements were obtained with UBM, Pentacam, and OCT.

RESULTS

Thirty-one eyes of 23 patients, comprising 15 women (65.2%) and 8 men (34.8%), mean age 41.8 years, were enrolled in the study. Duration of visual disturbance was 19.1 ± 14 months. The number of patients with photophobia was reduced from 100% to 29% after surgery. BSCVA improved 2 or more lines in 78% of the patients at 12 months. A hyperopic shift of 1.52 ± 0.91 diopters was achieved. Contrast sensitivity improved in both photopic and mesopic conditions. For each of the instruments, the CCT postoperative mean was significantly smaller than the preoperative measurement (P < .0001) and COT values were significantly reduced in comparison to the preoperative values (P < .001).

CONCLUSION

Improvements in photophobia, BSCVA, and contrast sensitivity were observed in patients treated using excimer laser PTK with low-dose MMC for subepithelial infiltrates.

Combined ethylenediaminetetraacetic acid chelation, phototherapeutic keratectomy and amniotic membrane transplantation for treatment of band keratopathy

PURPOSE

The objective of this study is to evaluate the therapeutic efficacy of ethylenediaminetetraacetic acid (EDTA) chelation and excimer laser phototherapeutic keratectomy (PTK) combined with amniotic membrane transplantation (AMT) for the treatment of band keratopathy (BK).

METHODS

Eleven eyes in ten patients with BK received combined PTK (ablation zone of central 7.0-7.5 mm, depth of 50 microm), EDTA chelation (0.05 M, 3 minutes), and amniotic membrane transplantation using fibrin glue. Preand postoperative best corrected visual acuities, symptom changes, reepithelialization time, cosmesis, recurrence, and complications were analyzed.

RESULTS

Visual acuity improved in three eyes (27.3%) and did not change in eight eyes (72.7%). Symptoms improved in all patients, and the mean reepithelialization time was 10.6+/-5.3 days. The cosmetic results were good in eight eyes (72.7%) and were fair in three eyes (27.3%). During the mean follow-up period of 11.4+/-6.1 months (range, 6 to 23 months), no postoperative complications or recurrences were observed.

CONCLUSIONS

The combination of EDTA chelation, PTK, and AMT is safe and effective for the treatment of band keratopathy.

Amniotic membrane transplant with superficial keratectomy in superficial corneal degenerations: efficacy in a rural population of north India

Aim:

To evaluate the applicability and efficacy of superficial keratectomy with transplantation of preserved amniotic membrane in superficial corneal degenerations in a rural population of Northern India in terms of visual improvement and surface regularization.

Settings:

Peripheral referral center in rural north India.

Materials and Methods:

This was a prospective non-comparative interventional case series where 24 eyes of 20 farmers from peripheral rural areas (M:F = 19:1) with visually significant superficial degenerative disorders (15 eyes with climatic droplet keratopathy one of which was associated with Salzmann nodular degeneration and nine eyes with band-shaped keratopathy) were subjected to amniotic membrane transplantation (single or multiple layer) combined with superficial keratectomy. Subjective and objective outcomes after surgery were evaluated and analyzed and statistical significance of the outcomes in various disorders was evaluated.

Results:

Eighty-eight per cent (21 eyes) had symptomatic relief from distressing preoperative symptoms while postoperative visual improvement by two or more lines was achieved in 23 eyes (96%) over a mean follow-up period of 26.8 ± 10.2 months. The surface irregularity present preoperatively was relieved in 23 cases while postoperative decline of vision with visually significant scarring was seen in one case (4%), which was labeled as failure.

Conclusions:

Amniotic membrane transplant with superficial keratectomy helped achieve subjective comfort, visual rehabilitation and clinical regularization of the corneal surface in superficial corneal degenerations during the mean followup of 26.8 ± 10.2 months in rural setups.

Indications and outcomes of phototherapeutic keratectomy in the developing world

PURPOSE

To analyze the indications and outcomes of phototherapeutic keratectomy (PTK) in the developing world.

METHODS

In this retrospective study, the records of 203 consecutive eyes of 191 patients who had undergone PTK at a tertiary eye care center were evaluated. The parameters assessed were indications of PTK, demographic features, best spectacle-corrected visual acuity (BSCVA), and pachymetry. PTK was done by using a 193-nm Ar-F Excimer laser (Chiron Technolas Keracor 217 C) in a 6-mm optic zone. Patients were followed up for 6 months.

RESULTS

The most common indication of PTK was symptomatic bullous keratopathy (103 eyes). The patients were divided into 2 groups: those with bullous keratopathy (PTK BK) and those with superficial corneal pathologies (PTK CS). In the PTK CS group, the most common indications were Salzmann nodular degeneration (n = 27) and spheroidal degeneration (n = 22). BSCVA improved from 20/222 (0.09) to 20/86 (0.23) in the PTK CS group and 20/384 (0.05) to 20/202 (0.09) in the PTK BK group (P < 0.0001 in both groups). There was a significant decrease in the number of patients with severe symptoms in the PTK-BK (P < 0.0001) and PTK-CS (P = 0.017) groups. The change in BSCVA was significantly related to both pre-PTK BSCVA and pachymetry in PTK-BK.

CONCLUSIONS

PTK is an efficacious treatment modality for symptomatic relief and visual gain in cases with superficial corneal involvement and bullous keratopathy.

Phototherapeutic Keratectomy for Epithelial Irregular Astigmatism: An Emphasis on Map-Dot-Fingerprint Degeneration

PURPOSE

To study the changes in irregular astigmatism in patients with recurrent corneal erosion syndrome due to map-dot-fingerprint degeneration and to demonstrate that both symptomatic and asymptomatic map-dot-fingerprint degeneration/recurrent corneal erosion syndrome may be related to irregular astigmatism, which can effectively be corrected by phototherapeutic keratectomy (PTK) or standard spherical photorefractive keratectomy (PRK).

METHODS

Eleven eyes with irregular astigmatism related to map-dot-fingerprint degeneration/recurrent corneal erosion syndrome with and without changes at the slit-lamp microscope were treated with PTK or spherical PRK, which was performed with a VISX S2 or S4 excimer laser. All eyes underwent videokeratography performed pre- and postoperatively using either the Tomey TMS-2N Topographic Modeling System or EyeSys Technologies Corneal Analysis System 2000.

RESULTS

Mean pre- and postoperative best spectacle-corrected visual acuity (BSCVA) was -0.18 +/- 0.14 logMAR and 0.04 +/- 0.04 logMAR, respectively. This improvement in BSCVA was statistically significant. The mean gain in Snellen lines was 2.4 +/- 2.1. Preoperative corneal videokeratography showed irregular astigmatism with an elevation pattern that was corrected in all eyes despite the fact that no astigmatic photorefractive correction was performed.

CONCLUSIONS

Following PTK, eyes with irregular astigmatism related to map-dot-fingerprint degeneration showed significant improvement in BSCVA and correction of irregular astigmatism as revealed by videokeratography. This study shows that irregular astigmatism can be exclusively of epithelial origin and in some eyes abnormal corneal epithelium may create optical aberrations. This possibility should be taken into account when, for example, wavefront-guided stromal photoablation procedures are being planned.

Excimer Laser Phototherapeutic Keratectomy

Anterior corneal pathology, such as corneal scars and corneal stromal dystrophies, can be visually devastating. Over the past decade, there was a shift in treatment of these conditions from corneal transplantation to phototherapeutic keratectomy (PTK) using the 193 nm excimer laser for visual restoration. We have reviewed the recent literature on techniques for performing and refining PTK and also on various pathologic conditions that can be treated with PTK. The primary indications for PTK include anterior corneal dystrophies, such as lattice, granular, and Reis-Bückler's dystrophy. PTK can produce significant visual improvement in these patients, and corneal transplantation or retransplantation can be delayed. Corneal degenerations, such as Salzmann's nodular degeneration, keratoconus nodules, and climatic droplet keratopathy, also can be successfully treated with PTK. Additionally, anterior corneal scars from such etiologies as trauma, corneal ulcers, and prior refractive surgery can have visual improvement with PTK. In summary, PTK is a powerful tool for the management of anterior corneal pathology. In a properly selected and well-counseled patient, PTK can significantly improve vision and quality of life.

Phototherapeutische Keratektomie (PTK)

The conceptual advantage of phototherapeutic keratectomy (PTK) include the option to remove diseased tissue on a micrometer scale. Although less invasive than other forms of corneal surgery, it remains a surgical procedure which carries inherent risks. In phototherapeutic indications this risk is higher than in otherwise healthy eyes undergoing photorefractive surgery. Potential general complications include wound-healing problems, infection, inflammation, or a recurrence of the underlying disease. More specifically, PTK is associated with unwanted refractive changes, such as a hyperopic shift or an irregular astigmatism. In this review, we discuss these problems along with prevention and treatment strategies in detail.

Salzmann's nodular degeneration of the cornea: a review and case series

Salzmann's nodular degeneration is a rare, noninflammatory, slowly progressive, degenerative condition. Bluish-white nodules raised above the surface of the cornea characterize it. It has usually developed in corneas with a history of phlyctenulosis, trachoma, vernal keratoconjunctivitis, measles, scarlet fever, and various other viral diseases. However, today the majority of cases have been seen without recognized previous keratitis. It is composed of dense irregularly arranged collagen tissue with hyalinization between epithelium and Bowman's layer or beyond. Manual removal, phototherapeutic keratectomy (PTK) with or without the use of topical mitomycin-C, lamellar or penetrating keratoplasty have been used in the treatment of this disease. Salzmann's nodular degeneration does not seem to consist of one clinical entity. In some cases, elevated and pannus-like tissue can be separated easily from the corneal surface leaving Bowman's layer almost untouched. In these eyes, subsequent PTK may be necessary to smooth the surface. Recurrences are rare in these eyes. In contrast, some eyes (often with major peripheral vascularization) are left with deep defects in Bowman's layer and superficial stroma after difficult mechanical removal of nodules. In these eyes, multiple masking/laser ablation procedures are mandatory to acquire a homogenous surface. In our experience, the required laser ablation depth is significantly greater and the best-corrected visual acuity to be expected is reduced in contrast to the eyes with easy removal of the nodules. In these eyes recurrences seem to occur more frequently after treatment. Of 35 eyes documented to have Salzmann's nodular degeneration during the last 15 years in our department, 22 needed PTK treatment. Visual acuity increased from 0.4 to 0.7 on average. As a routine, laser ablation should be combined with previous conventional removal of nodules and excessive pannus tissue. By doing so, lamellar and penetrating keratoplasty techniques are hardly ever required in those eyes.

Excimer Laser Phototherapeutic Keratectomy for Granular and Lattice Corneal Dystrophy: A Comparative Study

PURPOSE

To compare the visual and refractive outcome after excimer laser phototherapeutic keratectomy (PTK) for superficial comeal opacities in granular and lattice dystrophy.

METHODS

Phototherapeutic keratectomy was performed in 62 eyes of 40 patients (granular dystrophy [n = 50] and lattice dystrophy [n = 12]) after epithelial debridement and pannus removal. Data regarding pre-and postoperative best spectacle-corrected visual acuity, changes in spherical equivalent of manifest refraction, Zeiss keratometry, astigmatism, and corneal topography were analyzed and compared between granular and lattice dystrophy. Recurrence, if any, was noted during a mean follow-up of 3.0 +/- 2.7 years.

RESULTS

Best spectacle-corrected visual acuity improved in 79% and 62% of eyes with granular and lattice dystrophy, respectively. Spherical equivalent refraction increased by a mean of 1.3 +/- 1.7 diopters (D) (median: 1.0 D) for granular dystrophy and a mean of 1.0 +/- 1.8 D (median: 0.5 D) for lattice dystrophy. The keratometric central power decreased by a mean of -0.8 +/- 4.3 D (median: -1.6 D) for granular dystrophy and a mean of -0.3 +/- 1.6 D (median: -0.7 D) for lattice dystrophy. No significant changes were noted regarding keratometric astigmatism in either granular or lattice dystrophy. The proportion of "regular" and "mild irregular" keratometry mires increased (39% vs 67% for granular dystrophy and 0% vs 50% for lattice dystrophy). In granular dystrophy, the surface regularity index/surface asymmetry index (SRI/SAI) decreased significantly from 2.14/2.24 preoperatively to 1.31/0.80 postoperatively (P = .006/P = .01). In contrast, decrease of SRI/SAI from 1.97/1.65 preoperatively to 1.35/1.16 postoperatively did not reach statistical significance in lattice dystrophy. Recurrences were observed in 10 (20%) eyes with granular dystrophy and 2 (17%) eyes with lattice dystrophy.

CONCLUSIONS

Our results suggest that PTK may be tried in all patients with superficially accentuated opacities in granular and lattice dystrophy before undergoing a more invasive procedure, such as lamellar or penetrating keratoplasty.

Long-term outcome of excimer laser phototherapeutic keratectomy for treatment of Salzmann's nodular degeneration

PURPOSE

To describe the technique and evaluate the long-term success of excimer laser phototherapeutic keratectomy (PTK) for treatment of Salzmann's nodular degeneration.

SETTING

Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.

METHODS

This retrospective study comprised 22 eyes of 14 patients who consecutively had PTK for superficial corneal opacities in Salzmann's nodular degeneration between January 1990 and November 2003. In all cases, the nodules and as much pannus tissue as possible were removed with a hockey knife. Afterward, the laser ablation (MEL 60 or 70, Carl Zeiss-Meditec) was performed with repeated application of masking fluid to remove further scar tissue and smooth the surface. Intended depth of laser ablation ranged from 10 to 100 microm (mean: 41 microm +/- 43 [SD]).

RESULTS

In 86% of eyes, visual acuity improved after PTK, from 0.4 +/- 0.2 preoperatively to 0.7 +/- 0.3 postoperatively. The mean myopic shift was 1.5 +/- 0.7 diopters [D]. Median refractive cylinder changed from 1.0 D preoperatively to 0.7 D postoperatively. The median surface regularity index/surface asymmetry index (SRI/SAI) of the TMS-1 topography analysis system (Tomey) decreased from 2.0/1.6 preoperatively to 1.2/1.2 postoperatively. In 4 (18%) of 22 eyes, a recurrence had to be treated by repeat PTK during a mean follow-up of 2.0 +/- 1.8 years.

CONCLUSIONS

Results indicate that PTK is an effective and safe procedure for treatment of Salzmann's nodular degeneration. Laser ablation should be combined with prior mechanical removal of nodules and excessive pannus tissue.

Excimer laser phototherapeutic keratectomy in eyes with anterior corneal dystrophies: short-term clinical outcomes with and without an antihyperopia treatment and poor effectiveness of ultrasound biomicroscopic evaluation

PURPOSE

To evaluate the use of high-frequency ultrasound biomicroscopy (UBM) in determining the depth of corneal pathology in eyes undergoing excimer laser phototherapeutic keratectomy (PTK) for primary or recurrent anterior stromal corneal dystrophies. Corneal clarity, visual acuity, and refractive changes in eyes with and without an antihyperopia treatment were also analyzed.

METHODS

Twenty eyes of 14 patients with anterior stromal corneal dystrophies were treated with PTK. Eyes were evaluated pre- and 6-8 weeks postoperatively with slit-lamp biomicroscopy, manifest refraction, keratometry, computerized corneal topography, ultrasound pachymetry, and UBM.

RESULTS

Nineteen of 20 corneas (95%) had greatly improved corneal clarity after PTK. Mean uncorrected Snellen vision improved from 20/102 to 20/69, and best corrected vision improved from 20/62 to 20/38. Nine eyes (45%) improved two or more lines of uncorrected vision, and 13 eyes (65%) improved two or more lines of best corrected vision. Mean change in spherical equivalent was just -0.92 diopters (SD 4.3 diopters); however, the range was large (-13 to +3.88 diopters). UBM measurement of central corneal pathology did not correlate significantly with the actual PTK ablation depth (P = 0.07). The amount of antihyperopia treatment did not correlate with changes in manifest refraction spherical equivalent, keratometry, or computerized corneal topography readings but did correlate with length of time until corneal reepithelialization after PTK (P = 0.003).

CONCLUSIONS

PTK resulted in improvements in corneal clarity and visual acuity in most patients with superficial corneal stromal dystrophies. UBM was not an effective tool to accurately measure the depth of corneal pathology preoperatively. The combined approach of minimizing ablation depth and selective use of an antihyperopia treatment resulted in minimal mean change in spherical equivalent; however, the range was large. PTK is a very good minimally invasive technique to improve vision in eyes with anterior stromal corneal dystrophies.

La photokératectomie thérapeutique dans le traitement de la dystrophie grillagée de type I

PURPOSE

Lattice corneal dystrophy type I is an autosomal dominant corneal dystrophy caused by allelic mutations of the BIGH3 gene. Type I dystrophy is recognized clinically by the characteristic net of linear opacities within the corneal stroma that results from an accumulation of amyloid. This study was designed to evaluate the therapeutic potential of phototherapeutic keratectomy (PTK) for the treatment of lattice corneal dystrophy type I.

PATIENTS AND METHODS

PTK was performed with the Chiron Technolas Chiron Keracor 217c on a series of 19 eyes of 13 patients with lattice dystrophy type I. Mean patient age was 38.9 years. The mean follow-up period was 36 months. Localization of central opacities was determined by analyzing Scheimpflug images. The changes in spherical equivalent and best corrected visual acuity were evaluated at 1, 3, 6, 9, 12, 18, 24 and 36 months.

RESULTS

The central depth of the deposits measured with the Scheimpflug camera was on average 74.14+/-31.03 microm in the primary dystrophies and 30.1+/-10 microm in graft recurrence. We noted a clear improvement in visual acuity, which increased by 0.257+/-0.120 to 0.600+/-0.178 as of the 3rd month and stabilized at 0.684+/-0.257 until the 36th month. A disappearance of repeating ulcerations was observed at month 30. We found a statistically significant correlation (R=0.6776; p=0.0109) between the improvement in vision (in lines) and the depth of opacities (with the Scheimpflug camera). The mean hyperopic shift caused by photoablation (69+/-15 microm) was +0.71+/-1 D at 36 months.

CONCLUSION

These results confirm that PTK is an effective method of managing corneal lattice dystrophy type I.

New treatment for band keratopathy: superficial lamellar keratectomy, EDTA chelation and amniotic membrane transplantation

We report two cases of band keratopathy who were treated with thick amniotic membrane that contained a basement membrane structure as a graft, after ethylenediaminetetraacetic acid chelation with trephination and blunt superficial lamellar keratectomy in the anterior stroma. In each case, basement membrane was destroyed and calcium plaque invaded into anterior stroma beneath Bowman's membrane. The calcified lesions were removed surgically, resulting in a smooth ocular surface, and the fine structures of band keratopathy were confirmed by pathologic findings. After that, amniotic membrane transplantation was performed to replace the excised epithelium and stroma. Wound healing was completed within 10 days. Stable ocular surface was restored without pain or inflammation. During the mean follow-up period of 13.5 months, no recurrence of band keratopathy was observed. This combined treatment is a safe and effective method for the removal of deep-situated calcium plaque and allowing the recovery of a stable ocular surface.

Phototherapeutic keratectomy in Salzmann's nodular degeneration

PURPOSE

To describe the outcome in vision and refraction of phototherapeutic keratectomy (PTK) in Salzmann's nodular degeneration (SND).

METHODS

Five eyes of four patients underwent PTK with the objective of restoring an acceptable refractive status and improving visual acuity. This surgical technique aims to make the nodules level with the corneal surface using an excimer laser.

RESULTS

Best corrected visual acuity (BCVA) improved in all five eyes. Astigmatism was reduced in four eyes and increased somewhat in one. During the observation period one eye suffered a late recurrence that required a penetrating graft.

CONCLUSION

Salzmann's nodular degeneration is a rare disease that is sometimes difficult to diagnose as it has some resemblance to other diseases. The aetiology of the disease is unknown. Phototherapeutic keratectomy is a safe and effective mode of treatment. Recurrences occur with time.

Surgical do's and don'ts of corneal dystrophies

PURPOSE OF REVIEW

Characteristics of corneal dystrophies have been described with regards to such as location in the cornea, morphology, material composition, and recurrence after penetrating keratoplasty. The main goal of this review is to describe the surgical methods in treating corneal dystrophies.

RECENT FINDINGS

Laser in situ keratomileusis (LASIK) has been shown to aggravate corneal deposits in Avellino dystrophy exacerbation LASIK and hence should be avoided. Phototherapeutic keratectomy (PTK) has shown its usefulness in clearing opacities with visual improvement and prevents painful erosion, resulting in delay or postponement of corneal grafting in some corneal dystrophies. Mitomycin-C may be used topically in conjunction with PTK to reduce the recurrence of the opacities. Topical use of antibody to TGF-beta can also be considered to suppress recurrence of corneal opacities after PTK or lamellar keratectomy.

SUMMARY

Clinicians must become more adept at choosing a treatment depending on different genotypes and future studies on treatment of corneal dystrophies should be focused on establishing treatment of categorized corneal dystrophies based on their chromosomal mutation.

Influence of Ablation Parameters on Refractive Changes After Phototherapeutic Keratectomy

PURPOSE

The aim of the current study was to control the hypothetical effects of decreased laser energy delivered to the peripheral cornea during phototherapeutic keratectomy (PTK) and provide quantitative calculation of induced low and high order aberrations.

METHODS

We employed a model eye to simulate the refractive effect of homogeneous laser corneal irradiation, as in PTK, for different laser fluences (range 125 to 225 mJ/cm2) and treatment depths up to 200 microm.

RESULTS

The hyperopic shift induced by the relatively lower energy delivered at the peripheral ablation zone during PTK was proportional to the treatment depth and inversely proportional to the energy fluence. The hyperopic shift calculated using the above ablation parameters was lower compared to previously reported clinical results. Higher order wavefront aberration (total root mean square) changes were of minimal significance for treatment depths up to 200 microm.

CONCLUSIONS

After PTK, a hyperopic shift cannot be attributed to the energy delivery method alone. Modification of laser energy delivery algorithms may only minimize PTK-induced hyperopia.

Management of band keratopathy with excimer phototherapeutic keratectomy: visual, refractive, and symptomatic outcome

PURPOSE

To report on the outcome of excimer phototherapeutic keratectomy (PTK) in the management of band keratopathy.

METHODS

Analysis was performed on patients undergoing PTK for band keratopathy between January 1996 and December 1999. Patients were assessed as to whether the indication for PTK was for visual rehabilitation (visual group) or for ocular surface improvement (nonvisual group). Further data including pre- and postoperative best-corrected visual acuity, pre- and postoperative spherical equivalent (SE), and associated or previous ocular pathology were collected.

RESULTS

A total of 45 eyes of 33 patients underwent PTK for band keratopathy. In the visual group, there were 33 eyes of 22 patients, and in the nonvisual group 12 eyes of 11 patients. The visual acuity was improved or unchanged in 18/33 eyes (55%) of the visual group, while there was loss of one or more lines of acuity in 15/33 (45%). Loss of acuity was attributed to other factors in 11/15 eyes. There was a significant myopic shift (P<0.5) from the mean preoperative SE of +1.42 D (SD+/-3.21 D) to the mean postoperative SE of +0.32 (SD+/-3.26 D). Of the eyes in the nonvisual group, 10/12 (83%) had significant improvement of symptoms.

CONCLUSION

Excimer PTK is an effective procedure in the management of band keratopathy whether it is performed for visual rehabilitation or for ocular surface improvement to prevent erosions. Concurrent pathology is common and may limit the extent of visual improvement postoperatively. Factors associated with the myopic shift seen in this series may be epithelial remodelling, concurrent ocular pathology, or inaccuracy of preoperative refractive data.

Phototherapeutic keratectomy: 12 years of experience

BACKGROUND

Phototherapeutic keratectomy (PTK) has been employed as a surgical tool to treat corneal disease for more than 10 years. The laser has made it possible to remove superficial corneal opacities and thereby restore vision. The 193 nm ultraviolet light separates molecules and splits molecules in biological tissue, thereby ablating it. About 0.25 microm of tissue is ablated by each pulse. The development of the excimer laser technique has been fast. It has principally focused on refractive surgery but has also benefited PTK.

CORNEAL DYSTROPHIES

The ability to delay or postpone corneal grafting in superficial corneal dystrophies represents a very important achievement. Map-dot-fingerprint dystrophy or basal membrane dystrophy is a common indication for PTK. Other dystrophies such as Meesman's, Reis-Bückler's, Thiel-Benke's, granular, macular, lattice and Schnyder's can be treated, although with differing degrees of success and varying rates of recurrence. Subepithelial scarring in Fuchs' dystrophy has been ablated. Other trials have involved the removal of substantial parts of the stroma in order to reduce the load on the endothelium. Recurrent dystrophic changes can likewise be removed from corneal grafts and thus prevent the need for regrafting.

RECURRENT EROSIONS

Laser treatment has made it possible to manage wound-healing problems better after recurrent erosions. Recurrent erosions are the most common indications for PTK: several studies show good and persistent effects with this type of treatment. Persistent epithelial defects of various origins, among them corneal ulcers resulting from allergic disease, can likewise be treated.

SCAR TISSUE

Scars after surgery such as pterygeum excision can be removed. Smooth muscle actin containing fibroblasts in old scars should be given special consideration in PTK. Excimer laser surgery can be successfully combined with conventional surgery to remove excessive scar tissue, Salzmann's nodules and very flaky and coarse band keratopathy. Irregular corneal surfaces following ulcers and injuries pose problems that have so far proved difficult to overcome. Thinning is often seen after bacterial corneal ulcers or after herpes simplex keratitis. A rough or uneven surface can be made smoother by using modulators during treatment by casting a new surface under a hard contact lens (PALM technique), a surface that is then projected into the stroma by laser ablation. Modern techniques linking the excimer laser with computerized corneal topography and wavefront analysis promise to further improve the smoothing capacities of lasers and to increase the quality of optical results.

COMPLICATIONS

The most feared complication of PTK is the postoperative infection. These are rare. Haze is usually not prominent but scar tissue formation of a more persistent type has been noted after laser surgery in eyes with pre-existing surgical scars. Keratectasia has been described after PTK. Failure due to deep opacities or a surface that is too uneven is a more common frustration. This paper reviews advances in excimer laser treatment of corneal disease.

Amniotic membrane transplantation after the primary surgical management of band keratopathy

PURPOSE

To determine the safety and efficacy of amniotic membrane transplantation to restore and maintain a stable corneal epithelium and reduce ocular surface pain after surgical removal of band keratopathy arising from ocular causes.

METHODS

Fifteen patients (16 eyes) from two centers with band keratopathy secondary to ocular causes underwent amniotic membrane transplantation as a graft after surgical removal of calcific deposits with or without the use of ethylenediaminetetraacetic acid. In a prospective, consecutive, uncontrolled case series, the rate of corneal epithelialization and resultant surface stability were recorded over a mean follow-up period of 14.6 months.

RESULTS

Pain from ocular surface instability was the presenting complaint in 14 of 15 (93.3%) patients and resolved in all cases after the procedure even for those who experienced a recurrence of the calcific deposit. Fifteen of 16 eyes (93.7%) achieved epithelialization with a mean time to epithelial healing of 15.2 days. The only eye that failed to heal was subsequently diagnosed with total limbal stem cell deficiency. Visual acuity improved in five of nine (44%) sighted eyes and remained unchanged in four of nine (56%). No patient experienced any major surgical or medical complication after the procedure.

CONCLUSION

Amniotic membrane transplantation represents a safe and effective method to restore a stable corneal epithelium in eyes after primary surgical removal of band keratopathy arising from ocular causes.

Symptoms of dry eye and recurrent erosion syndrome after refractive surgery

PURPOSE

To determine the incidence and severity of patient complaints typical of dry eye and recurrent erosion syndrome after excimer laser refractive surgery and to compare the incidence of these symptoms after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Outpatient university practice.

METHODS

A questionnaire was mailed to 1731 patients who had had primary myopic PRK or LASIK at least 6 months previously. Questions were designed to determine the incidence and character of ocular dryness and recurrent erosion symptoms and their impact on patient satisfaction and willingness to have surgery again. Responses from PRK and LASIK patients were compared.

RESULTS

Responses from 231 PRK patients and 550 LASIK patients revealed an incidence of dryness symptoms in 43% and 48%, respectively (P >.05). Soreness of the eye to touch was reported by 26.8% and 6.7%, respectively (P <.0001). Sharp pains occurred in 20.4% of PRK patients and 8.0% of LASIK patients (P =.0001). Complaints of the eyelid sticking to the eyeball occurred in 14.7% and 5.6%, respectively (P =.0001). All symptoms occurred predominantly on waking. Frequency of eyelid sticking (P <.0005) and sharp pain (P <.005) symptoms, as well as severity of sharp pain symptoms (P <.0001), were significantly greater in PRK patients than in LASIK patients. On a scale of 0 to 10 (10 high), median overall patient satisfaction with surgery was 9 in both groups. Soreness of the eyelid to touch occurred significantly more frequently among patients with symptoms of sharp pains on waking (P <.001) and the sensation of the eyelid sticking to the eyeball (P <.001). Patients with 1 or more symptoms were twice as likely as asymptomatic patients to have a satisfaction score of less than 8 (P <.001).

CONCLUSIONS

Ocular dryness symptoms occurred commonly after PRK and LASIK. Symptoms suggestive of mild recurrent erosions included sharp pains, the sensation of the eyelid sticking to the eyeball, and soreness of the eyelid to touch, a previously unrecognized symptom of this condition. These symptoms occurred commonly after excimer laser procedures but were significantly more common, more severe, and more prolonged after PRK. The presence of these symptoms had a significant effect on patient satisfaction.

Epithelial ingrowth after laser in situ keratomileusis

PURPOSE

To report the incidence and risk factors for clinically significant epithelial ingrowth after laser in situ keratomileusis as well as the recurrence rate and visual outcomes after its treatment.

METHODS

We defined clinically significant epithelial ingrowth as that which required surgical removal. From a cohort of 3, 786 eyes that underwent primary laser in situ keratomileusis from February 1996 to August 1998 and its derivative of 480 eyes that later underwent enhancement laser in situ keratomileusis by one surgeon (R.K.M.), we identified all eyes with clinically significant epithelial ingrowth.

RESULTS

The incidence of significant epithelial ingrowth after primary treatment was 35 (0.92%) of 3,786 eyes. The incidence after enhancement treatment was eight (1.7%) of 480 eyes (p = NS). Fourteen of 43 eyes had a postoperative epithelial defect associated with subsequent development of epithelial ingrowth. Six of 43 eyes had loose epithelium intraoperatively, suggesting epithelial basement membrane dystrophy. Epithelial ingrowth was treated by lifting the flap, scraping the bed and the posterior surface of the flap, and replacing the flap without the use of caustic agents. In 42 of 43 eyes, the epithelial ingrowth under the flap was continuous with the surface epithelium. Clinically significant ingrowth recurred in 10 of 43 eyes after the initial surgical removal.

CONCLUSIONS

Clinically significant epithelial ingrowth is an infrequent complication of laser in situ keratomileusis. We hypothesize that epithelial ingrowth is secondary to postoperative invasion under the flap by surface epithelial cells rather than intraoperative implantation of epithelial cells. Treatment should consist of complete mechanical removal of epithelium from the posterior surface of the corneal flap and keratectomy bed and ensuring tight apposition of the flap with the bed.

Nutrition and the eye

The topic "nutrition and the eye" cannot adequately be covered in a single review article; indeed, dozens of books and hundreds of articles have been written on the subject. This review concentrates on three areas in which specific nutrients are known or theorized to have a major impact on vision and the visual system: vitamin A deficiency; antioxidants and their proposed role in the prevention of age-related cataract and macular degeneration; and nutritional optic neuropathies, including those of the recent Cuban epidemic. In addition, this article touches on nutritional treatments that have been suggested for several less common eye diseases and, finally, considers several less prevalent conditions in which deficiency of or excess exposure to a particular nutrient has been associated with ocular pathology.

Paradoxical response to photorefractive treatment for postkeratoplasty astigmatism

A 42-year-old woman with functionally disabling postkeratoplasty astigmatism in her right eye 3 years after corneal transplantation for keratoconus received photorefractive keratectomy for high astigmatism in that eye. This did not reduce her astigmatism. The procedure was repeated and corneal astigmatism paradoxically increased. The forces within the pseudo-optical ring that cause and maintain astigmatism in corneal transplants may be a significant factor in the unpredictable response of some corneal transplants to excimer photorefractive astigmatism correction.

Corneal Interface Abscess after Excimer Laser in situ Keratomileusis

Laser in situ keratomileusis (LASIK) carries the risk of infection. We report a case culture-negative interface abscess following LASIK that was successfully treated with antibiotics and povidone iodine.