Epithelial plugs in radial keratotomy: the origin of incisional keratitis?

CLEAR - Anatomy and physiology of the anterior eye

A key element of contact lens practice involves clinical evaluation of anterior eye health, including the cornea and limbus, conjunctiva and sclera, eyelids and eyelashes, lacrimal system and tear film. This report reviews the fundamental anatomy and physiology of these structures, including the vascular supply, venous drainage, lymphatic drainage, sensory innervation, physiology and function. This is the foundation for considering the potential interactions with, and effects of, contact lens wear on the anterior eye. This information is not consistently published as academic research and this report provides a synthesis from all available sources. With respect to terminology, the report aims to promote the consistent use of nomenclature in the field, and generally adopts anatomical terms recommended by the Federative Committee for Anatomical Terminology. Techniques for the examination of the ocular surface are also discussed.

Delayed infectious keratitis in a patient with radial keratotomy and floppy eyelid syndrome treated with simple interrupted stitches

A 55-year-old male presented with an infectious keratitis in his left eye, affecting one of the incisions of the radial keratotomy he had undergone thirty-four years ago. Suturing the incision with two simple interrupted stitches was key to the resolution of the infection. Floppy eyelid syndrome was also found in this patient. Could this act as a risk factor for infectious keratitis in radial keratotomy? To our knowledge, this is the first reported case describing the association between both conditions, and the second reported case where sutures have been used as an adjuvant treatment in these types of cases.

Biomechanical Simulation of Stress Concentration and Intraocular Pressure in Corneas Subjected to Myopic Refractive Surgical Procedures

Recent advances in the analysis of corneal biomechanical properties remain difficult to predict the structural stability before and after refractive surgery. In this regard, we applied the finite element method (FEM) to determine the roles of the Bowman’s membrane, stroma, and Descemet’s membrane in the hoop stresses of cornea, under tension (physiological) and bending (nonphysiological), for patients who undergo radial keratotomy (RK), photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), or small incision lenticule extraction (SMILE). The stress concentration maps, potential creak zones, and potential errors in intraocular pressure (IOP) measurements were further determined. Our results confirmed that the Bowman’s membrane and Descemet’s membrane accounted for 20% of the bending rigidity of the cornea, and became the force pair dominating the bending behaviour of the cornea, the high stress in the distribution map, and a stretch to avoid structural failure. In addition, PRK broke the central linking of hoop stresses and concentrated stress on the edge of the Bowman’s membrane around ablation, which posed considerable risk of potential creaks. Compared with SMILE, LASIK had a higher risk of developing creaks around the ablation in the stroma layer. Our FEM models also predicted the postoperative IOPs precisely in a conditional manner.

Eye rubbing type and prevalence including contact lens 'removal-relief' rubbing

BACKGROUND

Eye rubbing is commonly associated with keratoconus and may contribute to disease onset and progression. Verbal counselling to avoid rubbing may not be successful and adverse consequences of rubbing, which occurs on contact lens removal may be more serious. This study examines the prevalence of 'removal-relief' rubbing and its potential consequences.

METHODS

Rubbing histories were recorded for contact lens wearing normal and keratoconic patients as well as for normal non-contact lens wearers. Analogue scaled responses were used to identify and compare abnormal rubbing habits.

RESULTS

Contact lens wearing patients (both with and without keratoconus) reported significantly more rubbing before contact lens insertion (p < 0.05) compared to non-contact lens wearers. Eye rubbing after contact lens removal ('removal-relief' rubbing) was found to be significantly more prevalent among contact lens-wearing keratoconic patients compared to contact lens-wearing non-keratoconic patients (p < 0.001 in both cases).

CONCLUSIONS

Rubbing-related trauma occurring before contact lens insertion may predispose the cornea to wound healing activities and greater levels of adverse response to contact lens wear. Such adverse responses could predispose the cornea to greater trauma, which occurs in response to rubbing on removal of contact lenses. Strong counselling to avoid eye rubbing is often not an adequate form of management for a significant number of patients with keratoconus. Evidence of relapses indicates the need for better methods of counselling and for them to be repeated regularly. Apart from keratoconus, any other keratectasia, corneal disease or wound healing (including post-surgical) may increase susceptibility to corneal rubbing trauma. Such cases also appear to warrant counselling on avoidance of rubbing.

Acute hydrops with secondary bacterial keratitis: sequelae of paediatric refractive surgery

A 24-year-old male patient with bilateral high myopia presented to our outpatient department with sudden onset of pain and diminution of vision in his right eye. He had sequentially undergone bilateral trabeculectomy and photorefractive keratectomy at the age of 6 years in both eyes. This was followed by radial keratotomy in right eye at the age of 8 years. The slit lamp examination demonstrated the presence of infiltrates in central cornea with an underlying fluid cleft, along with 14 radial keratotomy scars. Anterior segment optical coherence tomography confirmed the presence of intrastromal cleft in communication with anterior chamber. Bacterial culture revealed coagulase-negative Staphylococcus. The patient was successfully treated with fortified antibiotics in conjunction with the sensitivity report. This case underlines the need for a cautious approach towards refractive surgery in paediatric age group and highlights the long-term sequelae of retreatments in these cases.

Changes in corneal basal epithelial phenotypes in an altered basement membrane

Background

To examine the corneal epithelial phenotype in an altered basement membrane.

Methodology/Principal Findings

Corneas from 9 patients with symptoms of continuous unstable corneal curvature (CUCC) were harvested by penetrating keratoplasty and subjected to histology examination and immunohistochemical staining with transactivating and N-terminally truncated pP63 transcript (ΔNp63), cytokeratin 3 (Krt3), ATP-binding cassette sub-family G member 2 (ABCG2), connexin 43 (CX43), p38 mitogen-activated protein kinases (p38MAPK), activating protein 2 (TFAP2), and extracellular signal-regulated kinase (Erk1/2) monoclonal antibodies. Positive immunostaining with ABCG2, p38MAPK, and TFAP2 monoclonal antibodies was observed in the basal epithelial cells of CUCC patients, and CX43 and ΔNp63 were detected in the full-thickness epithelial cells of CUCC patients.

Conclusions/Significance

Our results indicate that alteration of the corneal basement membrane induces a de-differentiation-like phenotype in corneal basal epithelial cells.

Granular corneal dystrophy manifesting after radial keratotomy

PURPOSE

To report a case of granular corneal dystrophy after radial keratotomy (RK).

METHODS

A 32-year-old man presented with white radial lines in both corneas. He had a history of uncomplicated RK in both eyes 8 years ago. Preoperative refraction had been OD -3.5-0.75 x 180 and OS -3.0-0.5 x 175. The cornea was reported to be clear on postoperative examinations.

RESULTS

Postoperative uncorrected visual acuity was OD 20/30 and OS 20/40. Best-corrected visual acuity was 20/25 in both eyes with OD -0.5-0.5 x 60 and OS -0.75-0.5 x 80. Slit-lamp examination revealed discrete well-demarcated whitish lesions with clear intervening stroma in the central anterior cornea consistent with granular dystrophy. Similar opacities were present within the RK incisions.

CONCLUSIONS

Production and deposition of such abnormal material could be due to keratocyte activation after RK or proliferation and migration of epithelial cells with a tendency to express abnormal keratoepithelin.

Infectious Keratitis After Astigmatic Keratotomy in Penetrating Keratoplasty

PURPOSE

To present 3 cases in 2 patients of infectious keratitis of the astigmatic keratotomy (AK) site in patients who had previous penetrating keratoplasty.

METHODS

History, clinical examination, chart review, cultures, and laboratory results were obtained from 2 patients with infectious keratitis within the donor stroma of their graft after an AK was performed.

RESULTS

One patient had an early infiltrate of the AK site that was culture negative. This cleared with fortified antibiotics, and the patient had a final visual acuity of 20/30-2. The second patient developed 2 late infections, the first with coagulase negative Staphylococcus and the second infection with Pseudomonas aeruginosa. Both of these infections cleared with fortified antibiotics, and the final visual acuity was 20/25. Neither patient developed a rejection episode from the infections, and both grafts survived.

CONCLUSIONS

We report a series of 3 cases of infectious keratitis in 2 patients after AKs in corneal grafts. This, to the best of our knowledge, has not been previously reported. Patients who suffer infectious keratitis after AK in corneal grafts may have good visual outcomes if managed with appropriate antibiotic regimens and closely followed.