Tuesday, March 7, 2017

ABSTRACT: Acute corneal epithelial debridement unmasks the corneal stromal nerve responses to ocular stimulation in rats: Implications for abnormal sensations of the eye.

J Neurophysiol. 2017 Mar 1:jn.00925.2016. doi: 10.1152/jn.00925.2016. [Epub ahead of print]
Hirata H1, Mizerska KK2, Dallacasagrande VA2, Guaiquil VH3, Rosenblatt MI3.

It is widely accepted that the mechanisms for transducing sensory information reside in the nerve terminals. Occasionally, however, studies have appeared demonstrating that similar mechanisms may exist in the axon to which these terminals are connected. We examined this issue using the cornea where nerve terminals in the epithelial cell layers are easily accessible for debridement, leaving the underlying stromal (axonal) nerves undisturbed. In isoflurane-anesthetized rats, we recorded extracellularly from single trigeminal ganglion neurons innervating the cornea that are excited by ocular dryness and cooling: low threshold (<2 and="" cooling="" high="" oc="" threshold="">2 oC) cold-sensitive plus dry sensitive (LT-CS+DS and HT-CS+DS) neurons, playing possible roles in tearing and ocular pain. We found that the responses in both types of neurons to dryness, wetness, and menthol stimuli were effectively abolished by the debridement, indicating that their transduction mechanisms lie in the nerve terminals. However, some responses to the cold, heat and hyperosmolar stimuli in LT-CS+DS neurons still remained. Surprisingly, the responses to heat in ~ half of the neurons were augmented after the debridement. We were also able to evoke these residual responses and follow the trajectory of the stromal nerves, which we subsequently confirmed histologically. The residual responses always disappeared when the stromal nerves were cut at the limbus, suggesting that the additional transduction mechanisms for these sensory modalities originated mostly likely in stromal nerves. The functional significance of these residual and enhanced responses from stromal nerves may be related to the abnormal sensations observed in ocular disease. 
Copyright © 2016, Journal of Neurophysiology.

ABSTRACT: The impact of dysfunctional tear films and optical aberrations on chronic migraine.

Eye Vis (Lond). 2017 Feb 21;4:4. doi: 10.1186/s40662-017-0070-1. eCollection 2017.
Shetty R1, Deshpande K1, Jayadev C1, Wadia K1, Mehta P1, Shroff R1, Rao HL1.
Author information
Migraine is a multifactorial disorder with complex neuronal and vascular mechanisms that encompasses a wide clinical spectrum of symptoms, including ocular manifestations. Dry eye disease and dysfunction of ocular somatosensory pathways have been implicated in the pathogenesis. The current study investigates the association between a dysfunctional tear film and ocular aberrations with migraine.
Sixty eyes of 30 patients with migraine and 60 eyes of 30 controls were studied. Dry eye evaluation included Schirmer's test, tear film break-up time, corneal esthesiometry and lipid layer analysis using Lipiview® interferometer. Wavefront aberrations were measured using Optical Path Difference before performing the dry eye evaluation. The intraocular light scatter was quantified using the objective scatter index (OSI) of the optical quality analysis system. Measured parameters were compared between the migraine and the control group using independent sample t-test. Statistical analysis was performed using commercial software. A p value of ≤ 0.05 was considered statistically significant.
There were 19 females and 11 males in each group. Statistically significant difference was found between the two groups with respect to total aberrations (p = 0.049), higher order aberrations (p = 0.009), coma (p = 0.03), spherical aberrations (p = 0.018), Lipiview interferometric coloric units (p < 0.001) and OSI (p < 0.001). Trefoil (p = 0.26) and TBUT (p = 0.398) were not significantly different between both groups.
Ocular aberrations are higher in patients with migraine as compared with controls. Tear film abnormalities add to the aberrations in otherwise asymptomatic patients and may also be associated with migraineous attacks. Treating the ocular surface to obtain a healthy tear film might introduce a potential modifiable factor in the prevention of migraneous attacks.

ABSTRACT: Alterations in Tear Biochemistry Associated with Postanesthetic Chronic Dry Eye Syndrome.

Biochemistry (Mosc). 2016 Dec;81(12):1549-1557. doi: 10.1134/S0006297916120166.
Zernii EY1, Golovastova MO, Baksheeva VE, Kabanova EI, Ishutina IE, Gancharova OS, Gusev AE, Savchenko MS, Loboda AP, Sotnikova LF, Zamyatnin AA Jr, Philippov PP, Senin II.

Perioperative dry eye syndrome (DES) is a common ocular complication of long-term general anesthesia. Chronic DES can lead to permanent damage to the cornea and disturbance of visual function, up to total loss of vision. Here, a relationship between the duration of general anesthesia and the risk of chronic DES in patients was demonstrated. Using an experimental model of perioperative corneal abrasions in rabbits, it was found that introduction of animals to 3-h general anesthesia resulted in clinically significant chronic damage to the cornea in 50% of cases. The development of the complication was not associated with irreversible or long-term impairment of tear secretion, but it was accompanied by a decrease in tear film stability and growth of the total protein content as well as decrease in total antioxidant activity of the tear induced by low molecular weight antioxidants. In addition, anesthesia-induced changes in activity of tear antioxidant enzymes including superoxide dismutase and enzymes providing homeostasis of reduced glutathione (glutathione peroxidase, glutathione-S-transferase, glutathione reductase) were observed. All these alterations were protracted (up to 1-2 weeks) and therefore might account for transition of the perioperative DES into the chronic form. These findings can be useful in the development of novel approaches for the prevention and treatment of chronic forms of DES in the postanesthetic period.

 ABSTRACT: Effect of pulsed laser light in patients with dry eye syndrome.

The objective of this study was to determine the clinical benefits of pulsed light therapy for the treatment of Dry Eye Syndrome (DES) due to the decrease in aqueous tear production (aqueous deficient DES) and/or excessive tear evaporation (evaporative DES) due to Meibomian Gland Dysfunction (MGD).
A study was conducted on 72 eyes corresponding to 36 patients with DES. Out of these 72 eyes, 60 underwent refractive surgery (48 with femtosecond laser, 6 were operated with a mechanical microkeratome, and 6 with refractive photo-keratectomy[RPK], 6 treated with phacoemulsification, and 6 with no previous surgical treatment. Pulsed laser light (Intense Pulsed Light Regulated [IRPL®]) was use to stimulate the secretion of the Meibomian glands during 4 sessions, one every 15 days.
Patients with aqueous deficient DES did not show any improvement. Eyes with no previous surgery and those treated with phacoemulsification and PRK had a favourable outcome. On the other hand, less conclusive results were observed in the eyes treated with excimer laser.
This treatment could be very helpful to treat evaporative DES produced by MGD. On the other hand, it is not helpful for those cases related to an isolated damage in the aqueous phase, or the mucin phase.

Arch Soc Esp Oftalmol. 2017 Feb 28. pii: S0365-6691(17)30034-5. doi: 10.1016/j.oftal.2016.12.018. [Epub ahead of print]
[Article in English, Spanish]
Guilloto Caballero S1, GarcĂ­a Madrona JL2, Colmenero Reina E2.
Author information

Blepharoplasty: An abstract, and perspectives on social media and patient expectations

This abstract is the kind of language that makes me weep and gnash my teeth. Well, at least gnash my teeth:
Upper Eyelid Blepharoplasty: Evaluation, Treatment, and Complication Minimization
Upper eyelid blepharoplasty is one of the most common procedures performed worldwide for both functional and cosmetic indications. There is a high rate of patient satisfaction; however, in this era of social media, patient expectations are higher than ever. Today's digitally savvy patients expect perfect outcomes with no complications and rapid recovery. To achieve optimal results, a careful preoperative evaluation and sound surgical technique is essential for minimizing complications. Here the authors review their approach to the management of the blepharoplasty patient.
Yang P, Ko AC, Kikkawa DO, Korn BS.Semin Plast Surg. 2017 Feb;31(1):51-57. doi: 10.1055/s-0037-1598628. Review.

It's not just because I field so many calls from people who have dry eye after blepharoplasty without having been warned of the possibility this might happen. (For those who aren't familiar with this, a particularly painful form of dry eye can occur after eyelid surgery due to eyelids ending up too short - much more likely to happen when done by a plastic surgeon than an oculoplastic surgeon, the latter being an eye doctor who knows skin and muscle, as opposed to the former, whose knowledge of eyes and the lacrimal system in particular will be much more limited.)

It's just, simply, what it says.

"This era of social media" obviously does not make it MORE incumbent upon a surgeon to screen carefully, use good technique and minimize complications. I presume all surgeons would want to do that whether or not their patient were likely to blab about their results to all their Facebook friends.

Of course, I do get that there is a context here. This is just an intro to what, for all I know (I'm not a subscriber so I don't have the actual study), is probably a thoroughly excellent review of technique.

Nevertheless, this kind of thinking and language... makes me gnash my teeth.

When you talk about patients having expectations of perfect outcomes - where do you think they get them from? You don't think it might have something to do with your glossy brochures, your perfunctory informed consent process and your failure to have serious conversations with them about specific complications that can ensue, including what they mean and how they are managed? 

Surgeons performing elective surgeries have a role to play in setting patient expectations, and they should own it and embrace it. They need to be especially cognizant of the uphill work undoing the effects of slick media upon patient expectations. 

Does sleep position affect dry eye?

Effect of Sleep Position on the Ocular Surface

Alevi D, Perry HD, Wedel A, Rosenberg E, Alevi L, Donnenfeld ED.

Cornea. 2017 Mar 1. doi: 10.1097/ICO.0000000000001167. [Epub ahead of print]

Dry eye disease is a multifactorial disease with numerous well-documented risk factors. However, to date, sleep position has not been associated with this condition. After observing patients in our practice, we believe that the sleep position in some cases may significantly affect dry eye and meibomian gland dysfunction (MGD).
This is a single-centered, cross-sectional, noninterventional, institutional review board-approved, single-masked, nonrandomized study of 100 patients whose complaints were related to dry eye disease and a control group of 25 age-matched asymptomatic patients. Two questionnaires were used: one to analyze patients' sleep habits and the other to assess patients' Ocular Surface Disease Index. Dry eye severity was graded based on the MGD stage, fluorescein corneal staining and lissamine green staining, Schirmer 1 testing, tear osmolarity levels, and clinical examination.
A statistically significant difference was shown with back sleeping compared with left side sleeping using lissamine green staining (analysis of variance, P = 0.005). The Ocular Surface Disease Index score was also found to be elevated in patients who slept on their right or left side (36.4 and 34.1, respectively) as opposed to back sleepers (26.7) with P < 0.05. There was no statistically significant correlation found between the sleep position and degree of MGD.
In addition to current treatment, patients who sleep on their side or face down might see a reduction in dry eye and MGD if they change their sleep pattern to the supine position.
This is an interesting topic... While it doesn't attempt to address the causes, I would imagine it's all about greater exposure, especially if lids aren't fully closing. It would be interesting to know more about the extent to which lubricant and physical barrier protection improve this - comparatively - for the different sleep positions.