Biomedical subjects

C Kniestedt

Publications and source records attributed to C Kniestedt.

6 recordsLinked to original sources

PubMed2006

[Dynamic contour tonometry].

Dynamic contour tonometry (DCT) is a new technology for noninvasive and direct measurement of intraocular pressure (IOP); its results are thought to be influenced less than those of other methods by structural characteristics of the eye. The curvature of the pressure sensing device is concave and only slightly flatter than that of the human cornea. The cornea adapts to the curvature of the transducer head, and the sensor in the centre of the adapted area measures the pressure on the other side of the cornea in the force-free range. Studies published so far suggest that DCT is less heavily dependent than applanation tonometry on the biomechanical properties of the cornea . A further advantage of DCT over other forms of tonometry is the capability of dynamic measurements over time. It is also possible to measure both the diastolic and the systolic IOD and determine the difference between the two, i.e. the ocular pulse amplitude (OPA). OPA is an indirect indicator of choroidal perfusion and reflects the condition of the arterial vascular system and the action of the heart. It could be important in the diagnosis and treatment of glaucoma.

Equipment Design↗

PubMed2005

[Tonometry in change. From indentation and applanation to contour adaptation].

The dynamic contour tonometer (DCT) is the first and only noninvasive contact tonometer that is capable of measuring intraocular pressure (IOP) directly and continuously. The touch of the pressure-sensitive tonometer tip induces the cornea to gently assume a shape (contour) which it will naturally assume when pressure on both sides is equal. A force field establishes between tonometer tip and cornea, that corresponds exactly to IOP. A piezoresistive pressure sensor, integrated into the surface of the tonometer tip, precisely measures IOP continuously and therefore also records time-dependent modulations of IOP as "ocular pulse amplitude" (OPA). Dependence of the DCT on biomechanical properties of the cornea is substantially smaller than with traditional tonometers that applanate or indent the cornea.

Cornea↗

PubMed2005

[Pepper spray injuries of the anterior segment of the eye].

BACKGROUND: A wide variety of pepper sprays is currently available and gaining increasing popularity among both professional guardians and amateurs. Adverse side effects to the anterior segment of the eye are known but underestimated. HISTORY AND SIGNS: We present two cases with severe corneal and conjunctival damage after accidental self injury by a pepper spray (Jet Protector Guardian Angel), benzyl alcohol 90.1 %, capsaicinoids 2.6 %). THERAPY AND OUTCOME: Despite immediate and intensive irrigation, a complete epithelial defect, extensive ischemia to the limbus and the conjunctiva and a circular conjunctival chemosis were diagnosed. After slow re-epithelialization in both cases, a neurotrophic superficial keratitis, a reduced corneal sensibility and in one case deep stromal scarring were noted. CONCLUSIONS: Pepper spray application to the eye might result in severe and permanent damage to the corneo-conjunctival tissue which is not adequately addressed in the current literature. From the present case reports arise the discussion whether the irritative and lipophilic capsacin/benzyl alcohol mixture or the pyrotechnical additives nitrocellulose und sinoxide are responsible for the anterior segment injuries.

Administration, Topical↗

PubMed2005

[Cataract and combined cataract/glaucoma surgery as intraocular pressure-reducing procedure in eyes with relative anterior microphthalmos].

PURPOSE: Eyes with relative anterior microphthalmos (RAM) (normal [> 20.0 mm] axial length but disproportionally small anterior segment [horizontal corneal diameter < 11 mm]) often present with increased intraocular pressure. Under these difficult conditions cataract surgery alone or in combination with a glaucoma filtering procedure is often required. PATIENTS AND METHODS: We retrospectively reviewed the records of 71 patients (108 eyes) with RAM in whom cataract only (n = 72) or combined cataract/glaucoma surgery (n = 36) was performed. Preoperative clinical and biometric findings, intraoperative complications and postoperative results (visual acuity and intraocular pressure) were analysed. RESULTS: Median preoperative values were 7.46 mm for corneal curvature, 2.53 mm for anterior chamber depth and 22.44 mm for axial length. The implanted lens had a median 25.0 dioptric power. The IOP was reduced from 15.6 +/- 3.9 mm Hg to 13.5 +/- 3.1 mm Hg with cataract surgery alone and from 22.4 +/- 5.5 mm Hg to 15.4 +/- 4.0 mm Hg with combined surgery. Mean best corrected visual acuity improved from 0.4 +/- 0.2 to 0.79 +/- 0.25 with cataract surgery and from 0.5 +/- 0.3 to 0.81 +/- 0.24 with combined surgery. Intraoperatively only 3 eyes had a rupture of the posterior capsule and postoperatively 2 eyes developed malignant glaucoma in the combined group. CONCLUSIONS: The results show that, in eyes with RAM, cataract surgery alone or in combination with glaucoma surgery can be performed with excellent results and low complication rate if adequate precautions are taken (especially the use of hyperosmotic agents).

Adult↗

PubMed2001

[Ultrasound biomicroscopy diagnosis of traumatic choroid effusion without cyclodialysis].

BACKGROUND: Chamber angle changes due to trauma represent a diagnostic challenge in modern ophthalmology and two examination techniques are compared: gonioscopy which has been used in ophthalmology for almost a century and is still undergoing continuous improvements and ultrasound biomicroscopy (UBM) which was introduced into clinical ophthalmology in 1991. CASE REPORT: We report the case of a 14-year-old boy with ocular trauma caused by a soft gun projectile. Gonioscopy showed a large goniosynechia in the presence of ocular hypotension, therefore, cyclodialysis was suspected. However, a control investigation using UBM showed an intact and circularly attached but anteverted ciliary body behind the synechia, a circular choroidal effusion and an anterior displacement of the iris-lens diaphragm. CONCLUSION: In ocular trauma, UBM may under certain conditions clearly be of a higher diagnostic value than gonioscopy. Therefore, UBM should not only be considered as an additional examination technique in the evaluation of traumatic ocular pathologies but rather as the technique of choice.

Adolescent↗

PubMed2000

[Dysgenetic changes of the angle of the anterior chamber in patients with glaucoma or suspected glaucoma acquired before age 40].

OBJECTIVE: The aim of this study is to determine percentage and degree of dysgenetic changes in the chamber angle in glaucoma suspects and in patients who acquired glaucoma before the age of fourty and to compare the primary classification with the classification after reexamination. PATIENTS AND METHODS: 200 eyes of 104 patients (59 males, 45 females, 0-40 yrs old (median 29) at time of detection) could be examined or reexaminded by gonioscopy and photography with the CGA-1 goniolens. The angles were documented by drawing and by goniophotography. The different features of dysgenesis served to establish a point-scale. RESULTS: Out of 200 eyes in 24 eyes (12%) a slight, in 81 (40.5%) an intermediate and in 49 (24.5%) a severe goniodysgenesis was found. By reexamination the dysgenesis rate rose from 48 to 77%. CONCLUSIONS: The high frequency of dysgenetic changes in the chamber angle of glaucoma patients affected under the age of fourty suggests, that in this age group developmental glaucoma is predominant and has to be separated as a special entity from POAG. Two questions arise: 1. Were these dysgenetic changes overlooked most of the time in the newer genetic studies of patients with GLC1A, or, if not, 2nd: Do glaucoma suspects and patients with open angle glaucomas before the age of 40 with and without dysgenetic changes belong to groups with different glaucoma genes, the "with" to genes IRID 1 and IRID 2 and the "without" to genes GLC1A to GLC1F?

Adolescent↗