An accurate inner diameter measurement.

The inaccurate deflection behavior of the probing system degrades the performance of the diameter-measuring machines. In this experiment, the probing is improved, applying an autocollimator and an angular positioning datum. We have devised this datum using a liquid wedge. A ring gauge is chosen as a workpiece to evaluate the deflection behavior of the probing system. The improved uncertainty of the probing is found as low as 40 nm. Subsequently, the inner diameter of the ring gauge is measured on this experimental setup. By employing a simulation, we aligned the workpiece. The deflections of the stylus are optimized to achieve zero deflection error at the zenith points. Consequently, the swing of the probe at the zenith points is combined with the rectilinear displacement of the workpiece to estimate the inner diameter. The uncertainty of the measurement of the ring gauge is improved up to 140 nm.

Estimation of mean ND: Yag laser capsulotomy energy levels for membranous and fibrous posterior capsular opacification.

INTRODUCTION: Posterior capsule opacification (PCO) is a visually-disabling complication of cataract surgery. OBJECTIVE: To estimate energy levels for capsulotomy in various subtypes of PCO (membranous, fibrous and fibro-membranous). MATERIALS AND METHODS: A total of 215 patients with PCO were randomly selected and evaluated for Nd: Yag laser capsulotomy, after a quiet post-operative course of 3 months.The ocular area was arbitrarily divided into three zones: YAG zone (3mm), Optical zone (6mm) and the peripheral zone (12mm). A colour code was assigned to the subtype of PCO in these zones: fibrous green and membranous blue. The type of PCO in each quadrant of YAG zone was estimated in percentage. RESULTS: The statistic mean values of initial energy levels were 1.80 mJ for membranous PCO, 3.17 mJ for fibrous PCO and 2.73 mJ for fibro-membranous PCO. The mean summated energy levels for membranous PCO was 22.80 mJ for membranous PCO, 80.06 mJ for fibrous PCO and 80.48 mJ for fibro-membranous type. CONCLUSION: Colour coding is extremely helpful for quantification of the type of PCO and in deciding the initial energy level necessary to create capsulotomy. Fibro-membranous PCO required more summated energy despite a lower starting energy. Therefore, we recommend firing the initial shot in fibrous portion in case of fibrous-membranous type of PCO.

High altitude and the eye: a case controlled study in clinical ocular anthropometry of changes in the eye.

Tribal natives of two spatially separate districts of Lahaul-Spiti (mean altitude = 3300 m) and Kinnaur (mean altitude = 1,700 m) in the Himalayan state of Himachal Pradesh have lived for centuries as closed isolated groups, marrying within the local community up to the recent past. Studies on highland natives in the Andes have shown differences in chest diameters, lung volumes, hematocrit, and the like, in those living at high altitudes. We wanted to study whether stay at high altitude for generations confers any change in the ocular anthropometry. No study of this nature is available in the literature. We studied the ocular parameters using Snellen's charts, Standard Royal-Air-Force Rule, A-2,500 Sonomed A-Scan, Goldmann's aplanation tonometer, and S-7,000 Autorefractometer on 50 healthy volunteers at the Indira Gandhi Medical College Out Patient Department at Shimla (mean altitude = 2,100 m). Those living at higher altitudes in Lahaul-Spiti [LS] (n = 10) had significantly wider nose bridge width (p < 0.05); inter-inner canthal distance [IICD] (p < 0.05); inter-outer canthal distance [IOCD] (p < 0.05); and interpupillary distance [IPD] (p < 0.05) than the group living at Kinnaur (n = 40) at lower elevation. The LS group also had narrower palpebral fissure length in the vertical dimension (p = 0.05) and a lower IOP (p = 0.002) than the Kinnaur group. The axial length, lens thickness, and anterior chamber depth were comparable in the two groups. It appears that the eye and its adnexa respond to hypoxia, ultraviolet radiations, and persistent snow cover at high altitude by altering its anthropometry in a subtle but discernible manner. This was a hitherto unexplored area in the literature. Further studies to elucidate and substantiate the findings of the study are indicated.

Effect of in-the-bag intraocular lens fixation on the prevention of posterior capsule opacification.

PURPOSE: To compare the incidence of posterior capsule opacification (PCO) after extracapsular cataract extraction (ECCE) and phacoemulsification and to evaluate the role of posterior chamber intraocular lens (PC IOL) haptic fixation and biomaterial/design in reducing the incidence. SETTING: Postgraduate Institute of Medical Education and Research, Chandigarh, India; Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: This study comprised 278 eyes of 263 patients having ECCE and 318 eyes of 297 patients having phacoemulsification with PC IOL implantation. Posterior capsule opacification leading to a decrease in Snellen visual acuity of 2 or more lines was considered visually significant. The presence of PCO and IOL haptic fixation were evaluated postoperatively using slitlamp biomicroscopy. Haptic position was noted as in-the-bag (B-B), 1 haptic in the bag and 1 in the sulcus (bag-sulcus [B-S]), or both haptics out of the bag (sulcus-sulcus [S-S]). In addition, the rate of visually significant PCO was compared among 3 IOL biomaterials: poly(methyl methacrylate), silicone, and hydrophobic acrylic. RESULTS: Visually significant PCO occurred in 42.45% of eyes having ECCE and 19.18% of eyes having phacoemulsification (P <.001, chi-square test) after a mean follow-up of 2.4 years +/- 0.7 (SD). In both groups, visually significant PCO was significantly less in eyes with B-B fixation than in those with B-S or S-S fixation (P <.001). The rate of visually significant PCO in all eyes in the phacoemulsification group with B-B fixation was low (11.90%) and was significantly lower in eyes with a hydrophobic acrylic IOL (2.22%; P <.05, chi-square test). CONCLUSIONS: In-the-bag PC IOL fixation is required to consistently reduce the incidence of PCO. Thorough removal of lens substance, including hydrodissection-assisted cortical cleanup, and in-the-bag PC IOL fixation seem to be the most important factors in reducing PCO, regardless of surgical procedure or IOL type used. Intraocular lens biomaterial and design also help prevent PCO.

Preoperative topical flurbiprofen-Na+ in extracapsular lens extraction role in maintaining intraoperative pupillary dilatation.

Induction of intraoperative pupillary constriction, is predominantly a prostaglandin mediated process. The most potent antiprostaglandin NSAID, Flurbiprofen was used topically to study its efficacy against the above. In a prospective double blind clinical study, 50 brown eyes undergoing planned E.C.C.E., the pupils were dilated with 10% phenylephrine and 2% homatropine 1%/tropicamide. 25 eyes received 0.03% Flurbiprofen-Na+ eye drops 1/2 hourly starting two hours before surgery. The maintained intraoperative mydriasis in the two groups before anterior chamber entry (stage I) vs at the end of complete cortex wash (stage III) was: in control group (stage I) 8.46 +/- 0.48 mm vs (stage III) 3.56 +/- 0.43 mm (highly SS); in flurbiprofen group (stage I) 8.60 +/- 0.48 mm vs (stage III) 8.01 +/- 0.63 mm (NSS). The pupillary area available for surgical manipulation in the control group was significantly decreased from 56.18 mm2 in state I to 9.94 mm2 in stage III, while in flurbiprofen group it changed insignificantly from 58.05 mm2 in stage I to 50.24 mm2 in stage III. Postoperatively after cataract was observed in 44% eyes of control group as compared to only 8% of eyes of flurbiprofen group. Thus a maintained intraoperative mydriasis in flurbiprofen group led to better E.C.L.E. which is a mandatory prerequisite to preferred and better present day posterior chamber IOL implantation.

Extraorbital use of a disinserted superior oblique as a sling in third nerve palsy: a new single-stage surgical technique.

The management of third cranial nerve palsy is surgical. The usual technique is to correct alignment of the eyes in the first stage, followed by ptosis correction by a sling operation in the second stage. A new single-stage surgical technique involved the disinsertion of superior oblique muscle to bring the eye in a midline position. Simultaneously it is used extraorbitally as a sling to raise the ptotic upper eyelid. Postoperatively a fairly good cosmetic effect was achieved, but the upper eyelid showed a paradoxic aberrant elevation on eso-depression.

Evaluation of combined systemic aspirin and cromolyn sodium in intractable vernal catarrh.

The steroids in vernal keratoconjunctivitis (VKC) are not always effective and may result in glaucoma. Cromolyn sodium inhibits degranulation from mast cells, thus preventing release of prostaglandins and the mediators of inflammation when used topically. Aspirin, which blocks the production of inflammation-producing prostaglandins in mast cells released in VKC, especially prostaglandin D2, was used orally in 11 patients with intractable VKC of mixed type with limbal predominance. The chi 2 test of combined therapy showed a significant improvement in itching, lacrimation, and limbal edema (P less than .005) and improved photophobia, palpebral lesions, and corneal staining (P less than .02) at six weeks.