Ectasia After Corneal Refractive Surgery: A Systematic Review

INTRODUCTION

The incidence of ectasia following refractive surgery is unclear. This review sought to determine the worldwide rates of ectasia after photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) based on reports in the literature.

METHODS

A systematic review was conducted according to modified Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Publications were identified by a search of eight electronic databases for relevant terms between 1984 and 2021. Patient characteristics and preoperative values including manifest refractive spherical refractive equivalent (MRSE), central corneal thickness (CCT), anterior keratometry, postoperative residual stromal bed (RSB), and percent tissue altered (PTA) were summarized. In addition, annual rates of each refractive surgery were determined, and incidence of post-refractive ectasia for each type was calculated using the number of ectatic eyes identified in the literature.

RESULTS

In total, 57 eyes (70 eyes including those with preoperative risk factors for ectasia) were identified to have post-PRK ectasia, while 1453 eyes (1681 eyes including risk factors) had post-LASIK ectasia, and 11 eyes (19 eyes including risk factors) had post-SMILE ectasia. Cases of refractive surgery performed annually were estimated as 283,920 for PRK, 1,608,880 for LASIK, and 96,750 for SMILE. Reported post-refractive ectasia in eyes without preoperative identifiable risk factors occurred with the following incidences: 20 per 100,000 eyes in PRK, 90 per 100,000 eyes in LASIK, and 11 per 100,000 eyes in SMILE. The rate of ectasia in LASIK was found to be 4.5 times higher than that of PRK.

CONCLUSION

Post-refractive ectasia occurs at lower rates in eyes undergoing PRK than LASIK. Although SMILE appears to have the lowest rate of ectasia, the number of cases already reported since its recent approval suggests that post-SMILE ectasia may become a concern. Considering that keratoconus is a spectrum of disease, pre-existing keratoconus may play a larger role in postoperative ectasia than previously accounted for in the literature.

Ocular Response Analyzer

Until recently, corneal biomechanical properties could not be measured in vivo. The ocular response analyzer is a new, noninvasive device that analyses corneal biomechanical properties simply and rapidly. The ORA allows cornea compensated IOP measurements and can estimate corneal hysteresis (CH) and corneal resistance factor (CRF). It is designed to improve the accuracy of IOP measurement by using corneal biomechanical data to calculate a biomechanically adjusted estimate of intraocular pressure. This review critically evaluates the technology and its implications in current day glaucoma management.

Overview of Ultrasound Biomicroscopy

Ultrasound biomicroscopy (UBM) is a high-resolution ultrasound technique that allows noninvasive in vivo imaging of structural details of the anterior ocular segment at near light microscopic resolution and provides detailed assessment of anterior segment structures, including those obscured by normal anatomic and pathologic relations. This review gives an overview regarding the instrument, technique and its applications.

Drug-induced Angle-Closure Glaucoma

Drug-induced angle-closure glaucoma is an important entity for the ophthalmologist as well as the general physician as it represents a preventable cause of potential blindness. This brief review highlights the fact that a high index of suspicion, in a susceptible individual followed by confirmation on appropriate imaging modality (UBM, ultrasound or anterior segment OCT) can alleviate the threat to sight and also help to institute appropriate therapy.

Perspectives on Quality of Life in Glaucoma

Chronic diseases are invariably associated with decreased functioning ability of the individual in one form or the other depending upon the system/organ involved. Disability consequent to the disease is the major factor affecting the patient's physical and psychosocial well-being; in other words, the 'Quality of Life (QOL)'. Besides the disease itself, the treatment and its consequences are also major determinants of QOL of the patients. Globally, glaucoma, which is emerging as one of the leading causes of blindness, is one such chronic ophthalmic disease characterized by a progressive loss of visual function and a potential to cause irreversible blindness, if not treated at an early stage. Patients of glaucoma need to take lifelong medications in order to keep their intraocular pressure within limits. It's impact on the daily life of patients cannot be overexpressed and compounded by the fact that it remains asymptomatic for a considerable time after the disease has set in; has led to new imperatives in diagnosis, treatment and epidemiological and outcome studies. Assessment of the debilitating effect of glaucoma and side effects of its treatment on the emotional and physical QOL of the patient is therefore an important criterion for arriving at the treatment regimen. An extensive literature search was done on Pubmed Central, Pubmed and Google Scholar using the keywords 'glaucoma', 'quality of life in glaucoma', 'management in POAG' and 'QOL assessment tools'. Various tools available for the assessment of QOL, and their advantages and limitations have been reviewed in this article.

Low Vision Aids in Glaucoma

A large number of glaucoma patients suffer from vision impairments that qualify as low vision. Additional difficulties associated with low vision include problems with glare, lighting, and contrast, which can make daily activities extremely challenging. This article elaborates on how low vision aids can help with various tasks that visually impaired glaucoma patients need to do each day, to take care of themselves and to lead an independent life.

MyoRing for Central and Noncentral Keratoconus

Purpose

To demonstrate treatment options for keratoconus using MyoRing intracorneal implant in central and noncentral cones.

Materials and methods

Five eyes with central and noncentral cones were compared in a retrospective study.

Results

In central cones the maximum of the flattening effect is in the corneal center while in noncentral cones the maximum of the flattening is in area of the cone.

Conclusion

No matter where the cone location is the implantation of MyoRing intracorneal implants always results in a regularization of the central cornea.

How to cite this article

Daxer A. MyoRing for Central and Noncentral Keratoconus. Int J Kerat Ect Cor Dis 2012;1(2):117-119.

Optical Coherence Tomography in Glaucoma

The optic disk and the RNFL are the principal sites of apparent glaucomatous damage which precedes glaucomatous visual field alterations. RNFL defects are known to precede detection of visual field defects by approximately 6 years. Accurate early detection and monitoring of ONH and RNFL defects has become the prime focus of effective management of glaucoma. Optical coherence tomography employs low-coherence interferometry to obtain cross-sectional images of the ocular tissues.

This review attempts to critically analyse the applications of both, anterior and posterior segment OCT in glaucoma management.

The Surgical Treatment of Neovascular Glaucoma with Ex-PRESS P-50 Miniature Glaucoma Shunt

Surgical treatment for neovascular glaucoma has evolved from cyclodestructive procedures to full-thickness filtration surgery, to trabeculectomy with antifibrosis drugs and glaucoma drainage implant surgery. The choice of a surgical approach may be influenced by several factors, including the stage of the disease. Many surgeons favor drainage implants when the disease is more advanced or when severe inflammation is present, which would be associated with a poorer prognosis if trabeculectomy were chosen. New devices are being developed to allow surgeons increased control with more predictable postoperative results. One such device, the Ex-PRESS™ mini glaucoma shunt, has undergone changes in design and method of insertion making it more appealing for use in patients requiring IOP-lowering surgery. This report highlights the use of Ex-PRESS mini glaucoma shunt in neovascular glaucoma, surgical technique and summarize pertinent literature on the role of this device in glaucoma surgery.