Excimer Laser Phototherapeutic Keratectomy

Manual Superficial Keratectomy Is the First Choice Treatment for Salzmann Nodular Degeneration

PURPOSE

This study aimed to describe the optical and topographic changes after manual superficial keratectomy (MSK) for Salzmann nodular degeneration.

METHODS

This was a descriptive, retrospective study. All patients with a clinical diagnosis of Salzmann nodular degeneration were examined at the Cornea Service of the Instituto Clínico Quirúrgico de Oftalmología (ICQO), Bilbao, Spain, and treated with MSK after presenting ocular discomfort and/or decreased visual acuity. The clinical characteristics (including anterior segment optical coherence tomography and Pentacam topography), treatment regimens, surgical procedures, and outcomes were recorded. Descriptive statistics were constructed using mean ± SD, minimum, maximum, and median. The Shapiro-Wilk normality test was used. The Student t test was used to determine significance.

RESULTS

Ten eyes of 9 patients were included in this study: 6 patients (66.6%) were female and 3 were male (33.3%). The mean age was 62.2 years, and the follow-up time was between 5 and 21 months. The best-corrected visual acuity before MSK was 0.20 LogMAR (median) and improved to 0.10 after the surgical procedure. The mean spherical equivalent was reduced from -0.23 ± 3.39 D preoperatively to -1.3 ± 3.0 D postoperatively. Astigmatism decreased between 0.5 and 3.75 D. Topographic irregularity normalized total root mean square from 11,596.4 ± 6854.01 to 4817.2 ± 2725.68 μm.

CONCLUSIONS

MSK is an effective and safe technique for the treatment of Salzmann nodular degeneration when the Bowman layer is preserved. Anterior segment optical coherence tomography and corneal topography are essential tools for the surgical plan and for the detection of corneal aberrations.

From bench to clinic: Emerging therapies for corneal scarring

Corneal diseases are one of the leading causes of moderate-to-severe visual impairment and blindness worldwide, after glaucoma, cataract, and retinal disease in overall importance. Given its tendency to affect people at a younger age than other blinding conditions such as cataract and glaucoma, corneal scarring poses a huge burden both on the individuals and society. Furthermore, corneal scarring and fibrosis disproportionately affects people in poorer and remote areas, making it a significant ophthalmic public health problem. Traditional medical strategies, such as topical corticosteroids, are not effective in preventing fibrosis or scars. Corneal transplantation, the only effective sight-restoring treatment for corneal scars, is curbed by challenges including a severe shortage of tissue, graft rejection, secondary conditions, cultural barriers, the lack of well-trained surgeons, operating rooms, and well-equipped infrastructures. Thanks to tremendous research efforts, emerging therapeutic options including gene therapy, protein therapy, cell therapy and novel molecules are in development to prevent the progression of corneal scarring and compliment the surgical options currently available for treating established corneal scars in clinics. In this article, we summarise the most relevant preclinical and clinical studies on emerging therapies for corneal scarring in recent years, showing how these approaches may prevent scarring in its early development.

Deep phototherapeutic keratectomy for Schnyder corneal dystrophy

We report a case of Schnyder corneal dystrophy (SCD) treated with deep phototherapeutic keratectomy (PTK). A 33-year-old man presented with a 5-year history of blurred vision and corneal haze in both eyes. Slit-lamp examination revealed needle-like subepithelial crystalline depositions and prominent arcus lipoides bilaterally. Similar clinical findings were observed in the patient's father. A diagnosis of SCD was made on the basis of the clinical presentation. PTK was performed using a multizone, multipass, and shoot and check technique with the WaveLight EX500 excimer laser. After 22 months of follow-up, the best-corrected visual acuity had increased from 0.5 to 0.9 in the right eye and from 0.3 to 0.9 in the left eye. SCD is rare but has a unique ocular presentation, which facilitates the diagnosis. PTK can increase patients' visual acuity and eliminate the need for aggressive management through penetrating keratoplasty or deep anterior lamellar keratoplasty.

Application of piggy-back lens in the correction of severe keratoconus: A case study

OBJECTIVE

This is a case study on the application of a piggy-back lens in the correction of severe keratoconus.

METHODS

From the results of general eye examination, refractive state examination, and corneal morphology examination on the patient, it was determined that corneal protrusion and deformation of the right eye were obvious. The right eye was corrected using a piggy-back lens and the left eye with a rigid gas-permeable contact lens (RGPCL) alone.

RESULTS

The right-eye lens fit well and the lens coverage was good. Both the static and dynamic fit results for the left-eye lens were good. After wearing the glasses for one month, the patient attended a review and stated that the lenses were comfortable to wear. The patient's vision was good after wearing the lenses. No obvious congestion was found in the conjunctiva under a slit lamp. The effects on both eyes of wearing RGPCLs were favorable. The corneal curvature reduced and the corneal thickness only changed to a small degree.

CONCLUSION

For keratoconus patients, application of a piggy-back lens can improve corrected visual acuity, comfort levels, and safety, prolong the wearing time, and enhance the effect of orthokeratology.

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.

Customized Ablation Area PTK as a Technique for Salzmann's Degeneration and Other Focal Stromal Pathologies

PURPOSE

To introduce a customized ablation area photo-therapeutic keratectomy (PTK) technique that uses a preoperatively generated laser ablation profile to accurately match and ablate the area of the pathology.

METHODS

A case of mid-peripheral Salzmann's nodular degeneration causing recurrent epithelial erosion is described. The white-to-white distance, on a slit-lamp image of the patient's eye, was measured by a Placido and dual-Scheimpflug analyzer and used as a scale on a Java-based image processing program to extrapolate the focal corneal pathology's vertical and horizontal dimensions on the corneal plane. The lesion's depth was measured by corneal optical coherence tomography (OCT). Customized ablation area transepithelial PTK, tailored to the exact dimensions of the pathology was then performed in one pass, regionally ablating the area of the pathology only.

RESULTS

Complete epithelial healing was observed by the next day with unaltered visual acuity of 20/20. Corneal OCT performed at 1 and 3 months postoperatively showed near-complete resolution of the lesion. The patient was followed up for a total of 6 months with no reported symptoms of corneal erosions.

CONCLUSIONS

The application of a customized laser ablation area in the treatment of Salzmann's nodular degeneration and other focal stromal pathologies avoids unnecessary epithelial and stromal ablation. This contributes to faster visual recovery and less refractive impact, especially for peripheral lesions. [J Refract Surg. 2020;36(5):340-344.].

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.].

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.

Phototherapeutic Keratectomy: Science and Art

PURPOSE

To describe, with videos, the principles of excimer laser phototherapeutic keratectomy (PTK) for the treatment of corneal scars, corneal surface irregularity, and recurrent corneal erosions.

METHODS

Depending on the pathology in a treated cornea, the epithelium is removed either by transepithelial PTK ablation with the excimer laser or thorough scraping with a scalpel blade. Stromal PTK can be performed with or without photorefractive keratectomy (PRK), depending on the refractive status of both eyes. Residual surface irregularity is treated with masking-smoothing PTK. Typically, 0.02% mitomycin C treatment is applied for 30 seconds to corneas treated with PTK for scars and surface irregularity.

RESULTS

Transepithelial PTK with masking-smoothing typically improves corrected distance visual acuity in the eye even if the entire stromal opacity cannot be removed and can be used to debulk surface irregularity to facilitate subsequent therapeutic customized wavefront-guided or optical coherence tomography-guided PTK or PRK. PTK for recurrent erosion is performed after thorough mechanical epithelial debridement of redundant epithelial basement membrane (EBM) with a scalpel and should only include a dusting of excimer laser to remove residual EBM without inducing central irregular astigmatism or damaging limbal tissues. Meta-analyses are provided for PTK treatment for corneal scars, corneal dystrophies, and recurrent corneal erosions.

CONCLUSIONS

Excimer laser PTK is a highly effective treatment for superficial corneal scars, central corneal irregular astigmatism, and recurrent corneal erosions unresponsive to medical treatment or mechanical epithelial debridement alone. [J Refract Surg. 2017;33(3):203-210.].

Clinical and genetic aspects of the TGFBI-associated corneal dystrophies

Corneal dystrophies are a group of inherited disorders localized to various layers of the cornea that affect corneal transparency and visual acuity. The deposition of insoluble protein materials in the form of extracellular deposits or intracellular cysts is pathognomic. Mutations in TGFBI are responsible for superficial and stromal corneal dystrophies. The gene product, transforming growth factor β induced protein (TGFBIp) accumulates as insoluble deposits in various forms. The severity, clinicopathogenic variations, age of the onset, and location of the deposits depend on the type of amino acid alterations in the protein. Until 2006, 38 different pathogenic mutants were reported for the TGFBI-associated corneal dystrophies. This number has increased to 63 mutants, reported in more than 30 countries. There is no effective treatment to prevent, halt, or reverse the deposition of TGFBIp. This review presents a complete mutation update, classification of phenotypes, comprehensive reported incidents of various mutations, and current treatment options and their shortcomings. Future research directions and possible approaches to inhibiting disease progression are discussed.

Excimer laser phototherapeutic keratectomy for the treatment of clinically presumed fungal keratitis

This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK) for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected corneal lesions were completely removed and the clinical symptoms resolved in 41 cases (87.2%). The mean ablation depth was 114.39 ± 45.51 μm and diameter of ablation was 4.06 ± 1.07 mm. The mean time for healing of the epithelial defect was 8.8 ± 5.6 days. Thirty-four eyes (82.9%) showed an improvement in best spectacle-corrected visual acuity of two or more lines. PTK complications included mild to moderate corneal haze, hyperopic shift, irregular astigmatism, and thinning cornea. Six eyes (12.8%) still showed progressed infection, and conjunctival flap covering, amniotic membrane transplantation, or penetrating keratoplasty were given. PTK is a valuable therapeutic alternative for superficial infectious keratitis. It can effectively eradicate lesions, hasten reepithelialization, and restore and preserve useful visual function. However, the selection of surgery candidates should be conducted carefully.

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.

Update on phototherapeutic keratectomy

PURPOSE OF REVIEW

To review all recent publications on the use of phototherapeutic keratectomy (PTK).

RECENT FINDINGS

Recent studies confirm the beneficial outcomes of PTK in a variety of anterior corneal disorder: anterior stromal scars, dystrophies of the corneal epithelium and the anterior stroma, and elevated corneal lesions. They also try to evaluate the biomechanical properties of eyes with granular corneal dystrophy undergoing PTK, in an effort to prevent iatrogenic ectasia. The different genotypes in patients with transforming growth factor, beta-induced linked corneal dystrophies have recently been correlated to the surgical outcome after PTK. An extensive review of recurrent corneal erosion syndrome identified PTK as the most effective treatment. In the developing world, the most common indication for PTK is still bullous keratopathy, as PTK can be successfully used while waiting for penetrating keratoplasty.

SUMMARY

PTK can successfully treat a variety of conditions of the anterior cornea. New studies may further expand its use.