How long does the recovery of corneal sensitivity in different corneal regions take after LASEK?

AIM:To determine the corneal sensitivity recovery period after laser-assisted sub-epithelial keratectomy(LASEK)refractive surgery and investigate the effects of ablation depth on it.METHODS:In this study examinations were performed on 90 right eyes of 90 people(34 males and 56 females)with an age range of 20-35 and an average of 22.26±3.8 years old.A sensation of 5 corneal regions,including the center and 4 mid-peripheral regions,i.e.,nasal,inferior,temporal,and superior,each at a distance of 2 mm from the center of the cornea were measured with a Cochet-Bonnet esthesiometer device in 3-time points including before LASEK,1 and 3mo after the surgery,respectively.LASEK was performed on individuals with stabilized myopia of -1.00 to -7.00 diopters and astigmatism of less than 2.00 diopters.Furthermore,the individuals were divided into three groups regarding ablation depth.RESULTS:The highest level of corneal sensitivity before surgery was related to the center of the cornea(59.1±7.76),and the highest level of corneal sensitivity loss was also related to this region.The sensation of all measured corneal regions significantly reduced 1mo postoperatively and returned to their preoperative levels 3mo after surgery(mean of 5 corneal regions in levels of preoperation:58.2±6.48,1mo postoperation:57.3±5.84,3mo postoperation:58.2±5.49;P<0.05).A significant relationship was found between ablation depth and corneal sensitivity changes in the center and temporal regions(P<0.05).CONCLUSION:Corneal sensitivity in myopia and low astigmatism decreases after LASEK and reaches the preoperative level within 3mo.The depth of ablation during surgery affected the recovery of corneal sensitivity.

Neurotrophic factors and corneal nerve regeneration

The cornea has unique features that make it a useful model for regenerative medicine studies. It is an avascular, transparent, densely innervated tissue and any pathological changes can be easily detected by slit lamp examination. Corneal sensitivity is provided by the ophthalmic branch of the trigeminal nerve that elicits protective reflexes such as blinking and tearing and exerts trophic support by releasing neuromediators and growth factors. Corneal nerves are easily evaluated for both function and morphology using standard instruments such as corneal esthesiometer and in vivo confocal microscope. All local and systemic conditions that are associated with damage of the trigeminal nerve cause the development of neurotrophic keratitis, a rare degenerative disease. Neurotrophic keratitis is characterized by impairment of corneal sensitivity associated with development of persistent epithelial defects that may progress to corneal ulcer, melting and perforation. Current neurotrophic keratitis treatments aim at supporting corneal healing and preventing progression of corneal damage. Novel compounds able to stimulate corneal nerve recovery are in advanced development stage. Among them, nerve growth factor eye drops showed to be safe and effective in stimulating corneal healing and improving corneal sensitivity in patients with neurotrophic keratitis. Neurotrophic keratitis represents an useful model to evaluate in clinical practice novel neuro-regenerative drugs.

Ocular surface changes in type II diabetic patients with proliferative diabetic retinopathy

AIM: To detect and analyze the changes on ocular surface and tear function in type II diabetic patients with proliferative diabetic retinopathy(PDR), an advanced stage of diabetic retinopathy(DR), using conventional ophthalmic tests and the high-resolution laser scanning confocal microscopy.METHODS: Fifty-eight patients with type II diabetes were selected. Based on the diagnostic criteria and stage classification of DR, the patients were divided into the non-DR(NDR) group and the PDR group. Thirty-six patients with cataract but no other ocular and systemic disease were included as non-diabetic controls. All the patients were subjected to the conventional clinical tests of corneal sensitivity, Schirmer I test, and corneal fluorescein staining. The non-invasive tear film break-up time(NIBUT) and tear interferometry were conducted by a Tearscope Plus. The morphology of corneal epithelia and nerve fibers was examined using the high-resolution confocal microscopy.RESULTS: The NDR group exhibited significantly declined corneal sensitivity and Schirmer I test value, as compared to the non-diabetic controls(P 【0.001). The PDR group showed significantly reduced corneal sensitivity, Schirmer I test value, and NIBUT in comparison to the non-diabetic controls(P 【0.001).Corneal fluorescein staining revealed the progressively injured corneal epithelia in the PDR patients. Moreover,significant decrease in the corneal epithelial density andmorphological abnormalities in the corneal epithelia and nerve fibers were also observed in the PDR patients.CONCLUSION: Ocular surface changes, including blunted corneal sensitivity, reduced tear secretion, tear film dysfunction, progressive loss of corneal epithelia and degeneration of nerve fibers, are common in type II diabetic patients, particularly in the diabetic patients with PDR. The corneal sensitivity, fluorescein staining scores,and the density of corneal epithelial cells and nerve fibers in the diabetic patients correlate with the duration of diabetes. Therefore, ocular surface of the patients with PDR should be examined regularly by conventional approaches and confocal microscopy to facilitate early diagnosis and treatment of keratopathy.

Effects of Contact Lens Wear on the Corneal Endotnelium and Sensitivity

The corneal endothelium of 38 contact lens wearers(74 eyes) and 74 normal eyes for control was photographed and analyzed with specular microscopy and the graphic processing system.The central corneal sensitivity and thickness were also measured.The results showed that the frequency