Advanced epithelial mapping for refractive surgery.

One of the leading challenges in refractive surgery today is the presence of underlying subclinical early-stage keratoconus (KC), which can lead to iatrogenic post laser in situ keratomileusis ectasia. Timely detection of this condition could aid the refractive surgeons in better decision-making. This includes being able to defer refractive surgery in subclinical cases as well as providing treatment for the same in the form of appropriate corneal collagen crosslinking treatments. Corneal topography is considered the gold standard for the diagnosis of corneal ectatic disorders. However, there is a likelihood that topographers are overlooking certain subclinical cases. The corneal epithelium is known to remodel, which may mask underlying stromal irregularities. Imaging and analyzing corneal epithelium and stroma independently will undoubtedly open newer avenues to supplement our understanding of postrefractive surgery outcomes and KC. This review encapsulates the various Optical coherence tomography-based epithelial mapping devices particularly RTVue (Optovue, Fremont, USA) and MS-39 (Costruzione Strumenti Oftalmici, Florence, Italy) in terms of their utility in these conditions. It will help guide the clinician on how including an epithelial mapping in clinical practice can aid in diagnosis, management, and interpretation of outcomes both for refractive surgery as well as KC.

Pupillodynamics and corneal spherical aberrations in a set of Indian cataract patients and its implications for aberrometric customisation of intraocular lenses.

PURPOSE: Assessment of pupil diameter in various light conditions and the corresponding corneal spherical aberrations in a cohort of Indian eyes with bilateral senile cataracts and the possible use of this data in aberrometric customization of intraocular lenses (IOLs). METHODS: In this prospective observational study done at a tertiary eye care centre in India, the selected patients were subjected to measurement of their pupil diameters in scotopic, mesopic, and photopic conditions as well as the corresponding corneal spherical aberrations, using the Sirius Topographer (Costruzione Strumenti Oftalmici, Florence, Italy). Shapiro-Wilk test, Independent t-test, ANOVA with Bonferroni correction on post-hoc testing were used for statistical analysis. RESULTS: 104 eyes of 52 patients were enrolled for the study. The mean age was 53 ± 11.88 years. The mean scotopic, mesopic, and photopic pupil sizes were 4.37 mm (4.11-4.63 mm), 3.92 mm (3.71 mm-4.15 mm), and 3.37 mm (3.18-3.67 mm), respectively. There was a statistically significant difference (P = <0.001) in the mean corneal spherical aberration measured at the 6 mm zone (0.23 ± 0.02 microns) and at the 4 mm zone (0.06 ± 0.01 microns). CONCLUSION: The mean corneal spherical aberration corresponding to the average mesopic pupil size of our patient population was substantially lower than that of the scotopic pupil size and also less than the amount corrected by most of the negative aspheric IOLs. This perhaps indicates the need for customising IOLs based on the spherical aberrations of cornea at the zone corresponding to the mesopic pupil diameter for optimal residual total postoperative spherical aberrations.

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

[This corrects the article DOI: 10.1186/s40662-017-0070-1.].

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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Current review and a simplified "five-point management algorithm" for keratoconus.

Keratoconus is a slowly progressive, noninflammatory ectatic corneal disease characterized by changes in corneal collagen structure and organization. Though the etiology remains unknown, novel techniques are continuously emerging for the diagnosis and management of the disease. Demographical parameters are known to affect the rate of progression of the disease. Common methods of vision correction for keratoconus range from spectacles and rigid gas-permeable contact lenses to other specialized lenses such as piggyback, Rose-K or Boston scleral lenses. Corneal collagen cross-linking is effective in stabilizing the progression of the disease. Intra-corneal ring segments can improve vision by flattening the cornea in patients with mild to moderate keratoconus. Topography-guided custom ablation treatment betters the quality of vision by correcting the refractive error and improving the contact lens fit. In advanced keratoconus with corneal scarring, lamellar or full thickness penetrating keratoplasty will be the treatment of choice. With such a wide spectrum of alternatives available, it is necessary to choose the best possible treatment option for each patient. Based on a brief review of the literature and our own studies we have designed a five-point management algorithm for the treatment of keratoconus.

WaveLight FS200 vs Hansatome LASIK: intraoperative determination of flap characteristics and predictability by hand-held bioptigen spectral domain ophthalmic imaging system.

PURPOSE: To intraoperatively determine and compare the characteristics and predictability of LASIK flaps made by the WaveLight FS200 femtosecond laser (Alcon Laboratories Inc) and Hansatome (Bausch & Lomb) microkeratome using a hand-held spectral domain ophthalmic imaging system (Bioptigen Inc). METHODS: Sixty eyes from 30 patients undergoing bilateral LASIK were prospectively evaluated. Patients were divided into two equal groups to undergo flap creation with either 100-microm femtosecond laser flaps (FS flap group) or 120-microm microkeratome flaps (MK flap group). Flap thickness was measured intraoperatively after creation of the flap but prior to lifting using the hand-held probe of the spectral domain imaging system. Geometry of the flap edge and smoothness of the stromal bed after lifting the flap was also evaluated in all cases. RESULTS: Mean difference between planned and achieved flap thickness in the paracentral region was 2.84 +/- 3.16 mm for the FS flap group and 11.33 +/- 10.27 mm for the MK flap group, whereas in the periphery, it was 5.72 +/- 3.26 mm in the FS flap group and 24.67 +/- 10.35 mm in the MK flap group. The differences between groups were statistically significant (P < 0.001, Kruskal-Wallis test). The edges of the flaps were vertical in the FS flap group and the stromal bed was smoother, whereas in the MK flap group, the edges were more sloping and the stromal bed more irregular. CONCLUSIONS: The WaveLight FS200 femtosecond laser is able to produce planar flaps with a high degree of predictability between the desired and achieved flap thickness. The ability to study the flap characteristics intraoperatively (when flap edema and stromal bed hydration changes have not yet occurred) with the hand-held probe of the Bioptigen imaging system ensures greater accuracy than measurements done postoperatively using other anterior segment optical coherence tomography prototypes.