Future Optometrists

KERATOMETRY OR OPHTHALMOMETER      Performed with a device called a keratometer or ophthalmometer, keratometry is the measurement of a patient's corneal curvature. As such, it provides an objective, quantitative measurement of corneal astigmatism, measuring the curvature in each meridian as well as the axis. Keratometry is also helpful in determining the appropriate fit of contact lenses. Components of a typical keratometer are illustrated in Fig 1.1. The box "Performing Keratometry" describes the procedure for obtaining measurements with this instrument. Fig 1.1 A typical Keratometer A) Side View B) Rear View (examiner's perspective) PERFORMING KERATOMETRY: 1. Looking through the eyepiece of the keratometer, use the eyepiece to focus the reticle(cross hair) in the same way as for the lensmeter. 2. Adjust the height of the keratometer table or platform so that the patient can comfortably put the chin and forehead on the appropriate rests. 3. Instruct the patient to pl

LENSOMETRY OR FOCIMETER OR VERTOMETER:       Lensometry is a procedure used to measure the prescription of a patient's existing eyeglass lenses or the power of contact lenses. This technique is often called neutralization, but should not be confused with neutralization as the word applies to retinoscopy. Lensometry is performed (usually by the ophthalmic medical assistant) with a specialized instrument knows as a lensometer.        Lensometry measures four principal properties of Lenses:           1. Spherical and Cylindrical power in dioptres.           2. Axes, if the lenses have a cylinder component.           3. Presence and direction of a prism incorporated into the lenses.           4. Optical centers.        Lensometry performed on a patient's eyeglasses before refraction can provide a starting point for the current refraction. This information is also useful in revealing changes in refractive error. Lensometry also serves to confirm that a patient's new glas

EYEGLASS ADJUSTMENTS         Ophthalmic medical assistants are often asked to make minor adjustments to the frames, such as tightening frame screws, measuring optical centers, and for multi-focals, measuring segment heights to ensure that they are properly placed and not a source of patient complaint. FRAME SCREWS:           Plastic frames usually have one screw holding each temple piece to the frame front (Fig 1.1). Most non-rimless metal frames have two screws on each side, one to hold the eyewire (the metal that encircles each lens) together and one to keep the temple piece in place. Fig 1.1 Typical Frame screw for a plastic frame           Loose eyeglass frame screws are a common problem. To adjust or tighten these screws, a jeweler's or optician's screwdriver and a small bottle of clear nail polish are needed. For instructions, see the box " ADJUSTING FRAME SCREWS " ADJUSTING FRAME SCREWS:          1. Tighten the screws with a jeweler's or optic

FITTING IN EYEGLASS FRAMES         Eyeglass Frames comes in a variety of sizes, shapes, styles, and materials, all of which have become influenced by fashion as well as the personal preferences of patients. Naturally, most patients try to choose frames that they feel are becoming to their appearance. However, opticians, ophthalmic medical assistants, and others who help patients choose frames and wear them comfortably also must consider frames from the aspect of their tilt and curve in relationship to the wearer's face, and their overall size and shape (both of which can affect proper peripheral vision), as well as their comfortable fit. Fig 1.1 shows the principal parts of a typical frame. Fig. 1.1. Anatomy of an Eyeglass Frame A) Front View of Frame B) Side View temple piece C) Top view of Frame Front         The pantoscopic angle of an eyeglass frame is the angle by which the frame front deviates from the vertical plane when the glasses are worn on the face. The pa

MEASUREMENT IN FITTING EYEGLASSES - PART II        Previously, we discussed the IPD measurement for distance and near vision. In this blog post, we will discuss how to measure the Vertex Distance and the Base Curve of the Lens. VERTEX DISTANCE:        The distance between the back of an eyeglass lens and the front of the eyeglass wearer's eye is the vertex distance (Fig1.1). A vertex distance of 13.5 mm is considered average, but vertex distance can range from 5 mm to more than 26 mm. The most effective fit for eyeglasses usually is obtained by fitting the frame as close to the eye as possible without the eyelashes touching the lens. Fig 1.1 Vertex Distance        Positioning a patient's eyeglasses at a vertex distance other than that used during refractometry will change the effective power of the lenses. The amount of change depends on the power of the lens. For low-powered lenses, the patient will not notice a difference in vision correction. But for high-powered

EYE ANATOMY GAME Dear All, AAO created 12 interactive models of the Eye. It is very useful for the Optometrist, Ophthalmologist and also for the medical students. Below links are very interactive study mode and gaming modes of the Eye models. All credits to the AAO team. 1. THE EYE AS AN OPTICAL SYSTEM 2.   THE ORBIT 3. THE EXTERNAL EYELID 4. CROSS SECTION OF THE EYELID 5. THE LACRIMAL APPARATUS 6. PLACE THE LAYERS OF CORNEA IN CORRECT ORDER 7. THE UVEAL TRACT 8. THE RETINA AND ITS JUNCTION WITH THE OPTIC DISC 9. THE VISUAL PATHWAY 10. STREAK MOVEMENTS 11. ANATOMY OF EXTRAOCULAR MUSCLES 12. BRAINSTEM ANATOMY OF THE CRANIAL NERVES INVOLVED IN EYE MOVEMENT

MEASUREMENTS IN FITTING EYEGLASSES      For eyeglasses to be effective, patients must feel satisfied with the prescription and the overall fit of the lenses of the face. Eyeglasses that fit improperly may cause vision problems. To help determine the source of a patient's dissatisfaction or discomfort with eyeglasses, ophthalmic medical assistants may need to measure interpupillary distance, vertex distance, and the base curves of the lenses.       Interpupillary distance (abbreviated IPD or PD) is the distance from the center of the pupil of the other eye. IPD is important to the laboratory technician who makes eyeglass lenses because it indicates where to place the ground optical centers in the finished lenses so that they lie directly in front of the patient's pupils. The optical center of a lens denotes the point of optimal vision; it is the single point through which light may pass without making being bent or changed (Fig 1.1) Fig 1.1 Relationship of the optical cen