Background: To determine the average amount of mechanical forces applied to the lids of keratoconus patients during eye rubbing. Methods: Fifty-seven patients (41 male, 16 female, average age 34.8 years) with a clinically and topographically diagnosed keratoconus and a history of eye rubbing were prospectively asked to perform their individual eye rubbing movement on a high-precision balance. The type of eye-rubbing movement and the force applied, represented in newtons (N), were recorded and analyzed. Results: We detected three different types of eye rubbing. Rubbing with the fingertip was most frequent (51%), followed by rubbing with the knuckle (44%) and rubbing with the fingernail (6%). Each type of eye rubbing showed different average forces, with knuckle type eye rubbing applying significantly more force (9.6 ± 6.3 N) on the lids than fingertip (4.3 ± 3.1 N) and fingernail (2.6 ± 3.3 N) types (p < 0,001 and p = 0,016, respectively). Conclusions: There were major variations in the force exerted on the lids, depending on the type of eye rubbing employed. This data will help determine the forces that need to be applied in future experimental eye rubbing models.
Corneal epithelium removal during photorefractive keratotomy (PRK), TransPRK, or corneal cross-linking (CXL) means that patients experience pain and inflammation after the procedure, which need to be carefully managed with topical drug regimens. One highly effective class of topical analgesics is non-steroidal anti-inflammatory drugs (NSAIDs), but these must be used carefully, as their use has been associated with delayed re-epithelialization and, in rare cases, corneal melting. However, our clinical experience has been that the concomitant use of topical corticosteroids obviates this risk. Here, we present a mechanistic explanation for our observations, our TransPRK and epithelium-off CXL protocols, and the postoperative medication regimens where topical NSAIDs are used in combination with topical steroid therapy during the first two postoperative days (where pain and inflammation levels are the highest). We detail the results of a single-center retrospective case analysis that examined eyes that underwent TransPRK (n = 301) or epithelium-off CXL (n = 576). Topical NSAID use in the first two postoperative days to control pain and inflammation after PRK/TransPRK or epithelium-off CXL, when used in combination with topical steroid therapy, does not appear to be associated with corneal melting or delayed epithelial healing. This approach may represent an improvement over current methods of handling post-surgical pain in procedures that require corneal epithelial debridement.
PURPOSE: To present a case of bilateral progressive keratoglobus that was successfully arrested with corneal cross-linking (CXL) applying the sub400 individualized fluence protocol. METHODS: Case report. RESULTS: A 36-year-old man with bilateral progressive keratoglobus and no history of eye rubbing presented with a corrected distance visual acuity (CDVA) of 20/200 in the left eye. Progression in the left eye was confirmed using previously taken corneal topographies and comparing them to high-resolution Scheimpflug imaging, high-speed dynamic Scheimpflug imaging, and anterior segment optical coherence tomography. Epithelium-off CXL was performed in the left eye using individualized fluence that was adapted to the thickness of the corneal stroma immediately prior to irradiation (sub400 protocol). Postoperative follow-up of 32 months showed stabilization of keratometric values and no endothelial cell loss. CONCLUSIONS: The sub400 epithelium-off CXL protocol using individualized fluence may arrest progressive keratoglobus and might represent a novel therapeutic approach for the management of keratoglobus. [ Journal of Refractive Surgery Case Reports. 2021;1(1):e10–e14.]
Corneal cross-linking (CXL) can halt ectasia progression and involves saturating the stroma with riboflavin, followed by ultraviolet-A (UV-A) light irradiation. This generates reactive oxygen species that covalently cross-link together stromal molecules, strengthening the cornea. The ‘Dresden protocol’ left a 70 µm uncross-linked region at the base of the stroma to protect the corneal endothelium from UV damage; however, this limited CXL to corneas ≥400 µm. Approaches made to overcome this limitation involved artificial corneal thickening to ≥400 μm through swelling the stroma with hypo-osmolaric riboflavin, applying riboflavin-soaked contact lenses during UV irradiation or leaving ‘epithelial islands’ over the thinnest corneal regions. The drawbacks to these three approaches are unpredictable swelling, suboptimal stiffening and unpredictable cross-linking effects, respectively. Newer approaches adapt the irradiation protocol to the cornea to deliver CXL that maintains the 70 μm uncross-linked stroma safety margin. The sub400 protocol employs an algorithm that models the interactions between UV-A energy, riboflavin, oxygen diffusion and stromal thickness. It requires only corneal pachymetry measurements at the thinnest point and the selection of the appropriate UV irradiation time from a look-up table to cross-link corneas as thin as 200 µm safely and effectively.
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