Recovery Of Corneal Sensitivity Research Articles

Comparison of the IntraLase Femtosecond Laser and Mechanical Microkeratome for Laser In Situ Keratomileusis

To compare clinical outcomes between the IntraLase femtosecond laser and the mechanical microkeratome for creating flaps during laser in situ keratomileusis. Nonrandomized clinical trial. The study involved a total of 55 eyes of 30 patients, with 27 eyes of 16 patients comprising the microkeratome group and 28 eyes of 14 patients comprising the IntraLase group. Refractive errors, visual acuity, higher-order aberrations, contrast sensitivity, and corneal sensitivity were compared between the two groups. There were no statistically significant differences between the two groups in terms of refractive errors and postoperative uncorrected visual acuity. There was no loss of best-corrected visual acuity in either group. The higher-order aberrations were similar in both groups (P > .05), except for spherical aberration, which was greater in the microkeratome group (P < .05). In the IntraLase group, the contrast sensitivity value at 12 and 18 cycles per degree under mesopic conditions was significantly improved at three months postoperatively (P < .05). The IntraLase group showed faster corneal sensitivity recovery compared with the microkeratome group, and corneal sensitivity in the peripheral area was nearly normalized at three months postoperatively in the IntraLase group. The femtosecond laser may have advantages over the microkeratome in the flap-making procedure. However, the IntraLase femtosecond laser failed to have significant superiority over the mechanical microkeratome in clinical outcomes, except for faster recovery of corneal sensation, lesser degree of spherical aberration, and some contrast sensitivity value.

Recovery of corneal sensitivity after laser in situ keratomileusis and laser-assisted subepithelial keratectomy

To compare the recovery of corneal sensitivity after laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK). Central corneal sensitivity (CCS) was measured with a Cochet-Bonnet esthesiometer in 59 patients before and 2 weeks, 1, 3 and 6 months after myopic correction by LASIK or LASEK. Among them, 50 patients were treated with LASEK and 9 patients were treated with LASIK. CCS were reduced in the early period time after LASEK and LASIK, but more reduction was seen after LASIK. At every time points, the CCS after LASEK was better than that after LASIK (at 2 weeks, 1 and 3 months P < 0.01, at 6 months P = 0.031). In myopic eyes with less than 6.00 diopters (D), the CCS recovered at 3 months after LASEK (P > 0.05), but it didn't recover at 6 months after LASIK (P = 0.023). In myopic eye with more than 6.00 D, the recovery of CCS was seen at 6 months after LASEK (P > 0.05). Correlations between CCS and ablation depth were found at 3 and 6 months after LASEK (r = 0.419, 0.433, 0.413; P < 0.05), but no correlation was found after LASIK (P > 0.05). Recovery of corneal sensitivity is faster after LASEK than after LASIK. Ablation depth is related to the recovery of corneal sensitivity after LASEK.

The effect of hinge position and depth plate on the rate of recovery of corneal sensation following LASIK

To evaluate and compare the effect of hinge position and flap thickness on recovery rate of corneal sensation after (LASIK). Prospective, randomized clinical study. Forty eyes of 40 patients underwent LASIK to correct myopia ranging from -1.00 to -2.50 diopters. Corneal sensitivity was measured preoperatively and each month after surgery until recovery to preoperative level. The nasal-hinged ACS microkeratome (NH) with depth plates of 130 and 160 microm and the superior-hinged Hansatome microkeratome (SH) with depth plates of 160 and 180 microm were used for corneal flap creation. The eyes were divided into four groups according to the hinge position and depth plate (DP): group 1, NH and 130 microm DP; group 2, NH and 160 microm DP; group 3, SH and 160 microm DP; group 4, SH and 180 microm DP. Corneal sensitivity returned to preoperative level after 3.7 (+/- 0.4), 4.4 (+/- 0.6), 5.4 (+/- 0.8), and 5.8 (+/- 0.9) months, respectively, in groups 1, 2, 3, and 4. Statistically significant differences were found between groups 1 and 2, but not between groups 3 and 4. Corneal sensitivity gradually returned to preoperative levels in all groups. Sensitivity of the hinge area was higher than other areas at every time point. The results suggest that after LASIK, hinge position and flap thickness seem to be important factors in the rate of return of corneal sensitivity. A thin flap with a nasally placed hinge is associated with the most rapid recovery of corneal sensitivity.

Effect of myopic LASIK on human corneal sensitivity

Objective To evaluate the changes in corneal sensitivity after LASIK for the correction of different degrees of myopia. Design Prospective, nonrandomized, comparative self-controlled trial. Participants One hundred two myopic eyes of 58 patients were included in this study. Methods The eyes were divided into four groups: group 1, from −0.75 to −3.75 diopters (D); group 2, from −4.00 to −7.75 D; group 3, from −8.00 to −11.75 D; group 4, from −12.00 to −16.00 D. Corneal sensitivity was measured before and 1, 7, 30, 90, 180, 270, and 365 days after surgery or until full recovery. Main outcome measures The recovery of corneal sensation after LASIK. Results Immediately after surgery, the lenticule was found to be completely anesthetic, and the full recovery varied according to the depth of the ablation. Normal levels of corneal sensitivity, but not full recovery, were found after 90 days in groups 1 and 2 and after 180 days in groups 3 and 4. Full recovery of corneal sensitivity was found after 180 days in groups 1 and 2 and after 270 days in groups 3 and 4. Conclusions After LASIK, corneal sensitivity is decreased at the central and paracentral areas for as long as 9 months. The depth of the ablation seems to be an important factor in the temporary decrease of corneal sensitivity and its recovery.

Effect of Amniotic Fluid in Corneal Sensitivity and Nerve Regeneration After Excimer Laser Ablation

To examine the effect of topical application amniotic fluids on the recovery of corneal sensitivity and nerve regeneration after excimer laser photokeratectomy, excimer laser was applied to 18 rabbits (VISX 20/20, 5 Hz, 7 microns depth: nine rabbits; 100 microns depth: nine rabbits). Human amniotic fluid (AF) was topically applied to the right eyes (AF group), and a balanced salt solution (BSS) was applied to the left eyes (BSS group). Corneal sensitivity was measured by using a Cochet-Bonnet aesthesiometer after weeks 1, 2, 4, 5, 8, and 12. Nerve-regeneration status was evaluated after weeks 2, 4, 5, 8, and 12 by gold chloride staining. Corneal sensitivity was initially subnormal and recovered close to the normal level at week 8. The sensitivity was higher in the AF group than in the BSS control group, except at week 2. Subepithelial nerve regeneration at the laser site was detected both at week 4 in the AF group and at week 5 in the BSS group. There was no significant correlation between the nerve-regeneration state and sensitivity changes. Long striated nerve regeneration from the deep stromal nerve was remarkable at the third month, especially in the BSS group. The BSS group showed more marked scarring of the superficial stroma, compared with the AF group. The nerve regeneration at the scar site was discontinued and delayed. Subepithelial leash nerves in the AF group were more abundant than those in the BSS group. The recovery of sensitivity and nerve regeneration were faster in the AF cornea than in the BSS cornea. These results suggest that the factors in AF helped the recovery of corneal sensitivity, nerve regeneration, and reduced scar formation.

Corneal sensitivity recovery after photorefractive keratectomy (PRK)

Purpose: To establish the pattern of recovery of corneal sensitivity post‐PRK using a non‐invasive aesthesiometer.Methods: Two studies were undertaken. (1) A longitudinal study monitoring the recovery of corneal sensitivity in 10 patients over one year, following a PRK correction of −6D/6mm (correction (D)/ablation diameter (mm)). (2) A transverse study examining corneal sensitivity one year postoperative on 68 patients who underwent various correction procedures: −3D/5mm (n = 16), −3D/6mm (n = 13), −6D/5mm (n = 14), −6D/6mm (n = 12) and −6D/Multizone (n = 13).Results: (1) Corneal sensitivity showed an immediate drop at week 1 (P &lt; 0.05), with a further decline at week 2 (P &lt; 0.05). Sensitivity recovered slowly over the following months. (2) Corneal sensitivity was reduced in the PRK‐treated eyes when compared to normal non‐contact lens wearing eyes (P &lt; 0.01). No specific procedures effect was found.Conclusions 1. The pattern of sensitivity change occurring is: (a) an initial rapid drop, followed by: (b) a slow recovery over 1 years.2. At one year, sensitivity is still below both normal and contact lens wear levels.3. The extent of sensitivity loss is not influenced by the depth of ablation.

Corneal sensitivity recovery after photorefractive keratectomy (PRK)

Purpose: To establish the pattern of recovery of corneal sensitivity post-PRK using a non-invasive aesthesiometer. Methods: Two studies were undertaken. (1) A longitudinal study monitoring the recovery of corneal sensitivity in 10 patients over one year, following a PRK correction of −6D/6mm (correction (D)/ablation diameter (mm)). (2) A transverse study examining corneal sensitivity one year postoperative on 68 patients who underwent various correction procedures: −3D/5mm (n = 16), −3D/6mm (n = 13), −6D/5mm (n = 14), −6D/6mm (n = 12) and −6D/Multizone (n = 13). Results: (1) Corneal sensitivity showed an immediate drop at week 1 (P < 0.05), with a further decline at week 2 (P < 0.05). Sensitivity recovered slowly over the following months. (2) Corneal sensitivity was reduced in the PRK-treated eyes when compared to normal non-contact lens wearing eyes (P < 0.01). No specific procedures effect was found. Conclusions 1. The pattern of sensitivity change occurring is: (a) an initial rapid drop, followed by: (b) a slow recovery over 1 years. 2. At one year, sensitivity is still below both normal and contact lens wear levels. 3. The extent of sensitivity loss is not influenced by the depth of ablation.

Aesthesiometry after Cryo-keratomileusis and in situ Keratomileusis

Objective: Evaluation of corneal reinnervation after cryo-keratomileusis and keratomileusis. Study Design: Retrospective evaluation of corneal sensitivity after cryo-keratomileusis and in situ keratomileusis. The measurements were performed with the Draeger electromechanical optical-controlled aesthesiometer, which is very precise and independent of external changes in temperature and humidity. Three measuring points were on the lenticle and 2 at approximately 1 mm distance from the limbus. Setting: Instituto Barraquer, Bogota, Columbia (South America). Patients: Twelve patients after cryo-keratomileusis and 38 patients after in situ keratomileusis. Results: It was shown that the recovery of corneal sensitivity after cryo-keratomileusis is delayed due to the depth of the keratectomy and freezing procedure compared to in situ keratomileusis.

Retrobulbar Blockade of Somatic, Motor, and Visual Nerves by Local Anesthetics

ABSTRACT Somatosensory, motor, and visual sensory blockade were investigated after retrobulbar injection of 3 m L 2% lidocaine, prilocaine, or mepivacaine plus hyaluronidase (15 U/mL) and naphazoline nitrate (1:20 000) in 90 cataract patients (n = 30 per group). Before injection as well as 20 and 90 minutes after injection, and then every 30 minutes, the quality of the retrobulbar blockade was evaluated in terms of the following factors until full recovery of function: (1) cornea! sensitivity at the three extraincisional quadrants as determined with an esthesiometer; (2) horizontal and vertical motility, and elevation of the lid; (3) visual acuity on an arbitrary score scale ranging from 0 (no light perception) to 6 (visual acuity &gt; 0.05); and (4) the time required for recovery from retrobulbar anesthesia. The data were analyzed by one- (anesthetic) and two-factor (anesthetic and time) analysis of variance. Full somatic recovery of corneal sensitivity occurred within 247 ± 10.2 minutes after lidocaine, within 221 ± 9.2 minutes after prilocaine, and within 280 ± 8.5 minutes after mepivacaine (F = 10.1; P &lt; .0001). Full motor recovery (all muscles) occurred within 290 ± 5.8 minutes after lidocaine, within 258 ± 5.7 minutes after prilocaine, and within 295 ± 4.8 minutes after mepivacaine (F = 13.3, P &lt; .0001) On the average, visual acuity decreased most after mepivacaine and least after lidocaine administration, although the differences between the three anesthetics in this regard were not significant. One patient temporarily lost vision after mepivacaine administration. Overall, the somatosensory and motor blockade were most pronounced after mepivacaine.

Hypersensitivity Following Excimer Laser Ablation Through the Corneal Epithelium

From our preliminary study, we found corneal hypersensitivity after excimer laser. To study the effects of corneal epithelial wound healing on corneal sensitivity, we investigated the recovery of corneal sensitivity following excimer laser and manual epithelial debridement. The corneal epithelium of the right eye of New Zealand white rabbits (n = 19) was manually debrided and the left eye was ablated with the excimer laser (5 Hz, 160 mJ/cm2, 47-micrometer depth). The wound-healing rate was measured up to 46 hours. Corneal sensitivity was measured for 10 weeks. There was no significant difference in the wound-healing rate, but at 36 hours there was a reduction in wound-healing rate of the excimer ablated corneas. In the laser-ablated cornea, sensitivity rapidly increased to a normal level by day 5, and then it continued to increase gradually and reached a maximum at day 42. Thereafter, it retained a higher level than normal up to 10 weeks. There were significant differences in the recovery of sensitivity following excimer ablation and manual debridement. These results show the development of a lasting enhanced sensitivity in the cornea after excimer laser ablation, suggesting the need to conduct further studies of neural plasticity and sensory thresholds following interventions on the corneal surface.

Recovery of Corneal Sensitivity in Grafts Following Penetrating Keratoplasty

Corneal sensitivity was tested in 145 cases of clear corneal transplants using Cochet-Bonnet aesthesiometer. The central area of corneal transplants was found to be either completely anesthetic or markedly hypesthetic even 32 years following corneal transplantation, as exemplified in a patient who had surgery for keratoconus. Age, preoperative diagnosis, contact lens wear, diabetes, or length of postoperative period had no correlation with sensitivity in corneal grafts. In cases with a preoperative diagnosis of failed graft, even the peripheral recipient cornea was found to be relatively hypesthetic. The observations from this study that the central area of corneal graft never recovers normal sensitivity may have significant implications on the epithelial cell integrity of corneal grafts.