Jayachandra R. Palakuru

Correlations Among Upper and Lower Tear Menisci, Noninvasive Tear Break-up Time, and the Schirmer Test

PURPOSE To determine the relationships among tear meniscus parameters, noninvasive tear break-up time (NITBUT), and the Schirmer test. DESIGN Experimental study. METHODS Thirty-six subjects were tested on one randomly selected eye. Real-time corneal optical coherence tomography (OCT) was used to image the upper and lower tear menisci during normal and delayed blinking followed by measurement of NITBUT and the Schirmer test. Digital images of the eye were taken for measuring the lid lengths to estimate tear volume in the menisci. RESULTS Compared with normal blinking, significant increases of tear menisci occurred during delayed blinking (post hoc, P < .01). NITBUT was weakly but significantly correlated with the height (r = 0.36; P = .03) and area (r = 0.37; P = .03) of the lower tear meniscus during normal blinks. NITBUT was also correlated with the lower tear meniscus volume (r = 0.45; P < .05) and total tear meniscus volume (r = 0.43; P < .05) during normal blinking. The Schirmer test was not significantly related to any parameters of the tear menisci, volumes, or NITBUT; however, it was negatively correlated with the age of the subjects (r = -0.47; P = .004). The age was negatively correlated with the upper tear meniscus (r ranged from 0.36 to 0.37 for the radius, height, and area, P < .05) measured during delayed blinking. CONCLUSIONS NITBUT appears correlated with the lower tear meniscus during normal blinking, and the Schirmer test appears not correlated with the noninvasively measured tear meniscus.

Dynamic Distribution of Artificial Tears on the Ocular Surface

OBJECTIVE To study the effects of artificial tear viscosity on tear film thickness, upper and lower tear menisci, and tear volume using optical coherence tomography. METHODS The central tear film and tear menisci before and immediately after the instillation of different artificial tears were imaged in 40 eyes of 20 healthy individuals. Carboxymethylcellulose sodium, 1.0% (viscosity, 70 cP), propylene glycol, 0.3%, and polyethylene glycol, 0.4% (10 cP), carboxymethylcellulose, 0.5% (3 cP), and isotonic sodium chloride solution (1 cP) were tested on 2 consecutive days. All measurements, including tear film thickness, the height, radius, and area of the tear meniscus, and the estimated tear volume, were obtained at 0, 5, 20, 40, and 60 minutes after instillation. RESULTS At instillation, all artificial tears and isotonic sodium chloride solution caused an increase in all tear variables (P < .001). Tear film thickness remained significantly elevated for all drops at 5 minutes (P < .001) and returned to baseline at 20 minutes. Other variables returned to baseline at 5 minutes. Comparing the different drops, tear film thickness and lower meniscus variables at instillation were increased with the more viscous drops (P < .05). CONCLUSION Optical coherence tomography demonstrated that all tear preparations, including isotonic sodium chloride solution, increased tear film thickness for at least 5 minutes and other variables immediately after instillation.

Keratoprosthesis: current techniques.

Purpose: To compare and contrast the techniques and results of keratoprosthesis (KPro) using the Cardona device (1975-1985) with those related to the use of the Dohlman-Doane type 1 device (2003-2005). Methods: We conducted a retrospective review of 31 cases of Cardona KPro implanted between 1975 and 1981 and a review of 25 cases of Dohlman-Doane type 1 KPro implanted between 2003 and 2005. Procedures were limited to eyes with a poor prognosis for traditional penetrating keratoplasty. Results: In the Cardona cases, 39% (12/31) of patients achieved a visual acuity of 20/40 or better at some point postoperatively, degrading to 16% (5/31) at the end of the observation period. Fifty percent (15/31) required subsequent surgical revision of the KPro. Sixteen percent of cases (5/31) developed endophthalmitis, and 58% (18/31) developed retroprosthetic membranes. There were 5 dislocations of the prosthesis and an additional 3 frank extrusions (26%). Of the 25 Dohlman-Doane cases, there have been no reoperations, endophthalmitis, dislocations, or extrusions to date (8/15/05). Forty-eight percent (12/25) achieved 20/200 acuity or better, and 12% (3/25) achieved 20/40 or better. Retroprosthetic membranes formed in 3 cases. Conclusion: Although KPro remains a technique to be used in poor prognosis keratoplasty, improvements in the design of the device and surgical technique over the past 30 years have reduced the overall morbidity and severity of complications and improved the prognosis for visual rehabilitation.

Effect of Blinking on Tear Volume After Instillation of Midviscosity Artificial Tears

PURPOSE To determine by optical coherence tomography (OCT) the effect of blinking on ocular surface tear volume after instillation of artificial tears. DESIGN Experimental study. METHODS Normal human eyes (n = 21) were imaged to obtain dimensions of the tear film and menisci during blinking. The imaging was carried out immediately and five minutes after the instillation of 35 microl midviscosity artificial tears (1.0% carboxymethylcellulose; Refresh Liquigel; Allergan, Irvine, California, USA). The exposed ocular surface area and the lid lengths were used to calculate the volumes. RESULTS Immediately after the instillation, total tear volume was increased (P < .001) compared with five minutes after the instillation, with the major increases in the lower tear meniscus volume and tear film volume. After the instillation, blinking caused tear loss in total tear volume because of the decrease of the lower tear meniscus volume (P < .05). In contrast, blinking increased the tear film volume (P < .05). At the end of the eye-opening period, tear film volume decreased and lower tear meniscus volume increased significantly (P < .05), with no significant changes in total tear volume (P > .05). During the blink cycle immediately after the instillation, net loss was evident in tear film volume, lower tear meniscus volume, and total tear volume (P < .05). CONCLUSIONS Blinking plays a crucial role in distribution and removal of instilled tears. When the tear system is overloaded, the increase in blink output helps restore balance.