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Ind J Ophthalmol ; Advanced Search Users Online: Confidence with confidence intervals. Indian J Ophthalmol ; Click here to view. Uses of the confidence interval. Determining magnitude of the difference. Interpreting a negative study. Related articles Confidence Interval p value. Optical section.

Describe the principles. Focal illuminationAchieved by narrowing the slit beam horizontally or vertically. It permits isolation of specific areas of cornea for observation without extraneous light outside area of examination. Oblique illuminationLight beam is projected from an oblique angle. It is useful for detecting and examining findings in different layers of the cornea. Optical sectionThis is the most important and unique feature of slit lamp achieved by making a narrow slit beam.

Uses include determining depth or elevation of a defect in cornea, conjunctiva or locating the depth of opacity within the lens, etc. What are the types of illumination used for examination? The different illumination in the sequence in which they are used are: i. Diffuse illumination ii. Sclerotic scatter iii. Direct focal illumination iv. Broad tangential illumination v. Proximal indirect illumination vi.

Retroillumination from the iris a. Retroillumination from the fundus viii. Specular reflection. What is meant by diffuse illumination? Diffuse illuminationalso known as wide beam illumination. Principlea wide unnarrowed beam of light is directed at the cornea from an angle of approximately SettingsMicroscope is positioned directly in front of the eye and focused on the anterior surface of the cornea Magnification used is low to medium Illumination is kept at medium to high USES i.

Gross inspection of any corneal scar, irregularities of lid, tear debris, etc. Bulbar and palpebral conjunctiva ii. It can be used with cobalt blue or red free filters. Cobalt blueintroduction of cobalt filter without fluorescein will cause corneal iron rings to appear black, so is useful in detecting subtle fleischners ring in early keratoconus. The cobalt blue filter produces blue light in which the fluorescent dye fluoresces with yellow green color used for evaluating fluorescein staining of ocular surface tissues or the tear film or during Goldmann applanation tonometry.

Red free filterproduces light-green light for evaluation of rose Bengal Staining. Also used to evaluate nerve fiber layer. What is sclerotic scatter? Principle: The optical principle is based on fiberopticsthe total internal reflection of light i. The slit beam is directed at the limbus. The opaque sclera scatters the light and some of the light is directed into the stroma where it travels through the entire cornea by repeatedly reflecting from its anterior and posterior surfaces. In normal corneait creates a glowing limbal halo but no stromal opacity is visible.

When opacity is presentthe internally reflected light is scattered back to the observer outlining the pattern as in Reis-Bucklers dystrophy. Settingsslit lamp is about 15 from the microscope. Slit beam is decentered if full view of cornea is desired. Slit height is set at full and slit width at medium broad.

What is direct focal illumination? It is of 2 types A. Direct focal illumination with broad beam B. Direct focal slit illumination with narrow beam A. Direct focal illumination with broad beam PrincipleSlit lamp light is focused directly on an area of interest. Wider the slit beam, less information is presented to the examiner. Settings Slit beam is approximately 30 from microscope. Slit height is full and slit width is medium broad. Uses: Crumb like deposits of granular stromal corneal dystrophy, stand out in direct focal illumination as they are white, reflect light, have sharp margins and are embedded in clear cornea.

Direct focal slit illumination with a narrow beam i. Principle: Slit lamp is placed obliquely and the slit beam is narrowed. The focused slit creates an optical cross-section of the cornea allowing the examiner to localize the level of opacities within the cornea and to determine corneal thickness.

Settings: Slit lamp is positioned from microscope Slit height is full and slit width is narrow. Movement: Moving the narrow slit systematically across the cornea allows to view serial optical sections and to construct a mental picture of corneal pathology. Uses: Moderately thin slit is used to identify the pigmentation of Krukenbergs spindle on the posterior surface of cornea.

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The narrow slit beam localizes i. The net like opacity in Reis-Bucklers dystrophy to subepithelial area. Extreme thinning in area of descemetocele in cases of herpes simplex keratitis. Focal central thinning of cornea in cases of post keratitis scarring, and keratoconus. What is broad tangential illumination? Principle: The examiner focuses the microscope on an area of interest and swings the slit beam far to the side at an extremely oblique angle so that the light sweeps tangentially across the surface of cornea. This enhances surface details by shadowing.

Settings: Slit beam is from microscope Slit height is narrow to one half and slit width is very broad. Uses Highlights irregularities on anterior corneal surface i. Corneal intraepithelial neoplasia ii. Sterile stromal ulcers iii. Calcific band keratopathy with holes iv.

Diffuse punctate epithelial keratopathy Highlights irregularities on posterior corneal surface, e. What is proximal indirect illumination? It combines features of both sclerotic scatter and retroillumination PrincipleA moderately wide slit beam is decentered and placed adjacent to an area of interest. Light travels through corneal stroma by internal reflection as it does in sclerotic scatter and accentuates the pattern of opacity. SettingsSlit lamp is about 15 from microscope Slit height is full and slit width is moderate UsesHighlights the internal structures of corneal opacity Enables the identification of details within the opacity, e.

What is retroillumination of iris? Give its uses. Retroillumination of the iris can be of two types i. Direct ii. Indirect Direct retroillumination of the iris PrincipleThe slit beam reflects from the surface of the iris and illuminates the cornea from behind and accentuates the refractive properties of corneal pathology. It allows detection of abnormalities not apparent in direct illumination.

For example, epithelial basement membrane fingerprint lines Settings Slit lamp is separated by from microscope Slit height is reduced and slit width is medium. Indirect retroillumination of the iris Principle: The slit beam is decentered so that it hits the iris near the pupil adjacent to the area of interest in the cornea. Microscope is adjusted so that the area of interest is viewed at the edge of the path of light reflected from iris marginal retroillumination or against the adjacent black pupil indirect retroillumination.

Settings The beam can be decentered to allow viewing of object of interest over dark edge of pupil. Slit height is reduced to eliminate background scatter and slit width is narrow to medium. What is retroillumination from fundus? Principle: Slit beam is placed nearly co-axial with microscope and rotated slightly off axis so that it shines in through margin of pupil.

This allows the red light reflected from the ocular fundus to pass through cornea to microscope. Settings Slit lamp is aligned co-axial with microscope, then decentred to edge of pupil. Slit height is reduced to one-third to avoid striking the iris Slit width is medium and curved at one edge to fit in the pupil USESThe following abnormalities are seen: i.

Lattice dystrophy ii. Pseudoexfoliation iii. Keratic precipitates iv. Corneal scars v. Meesmanns dystrophy vi. Map-dot fingerprint dystrophy vii. Lens vacuoles viii.

Cataract ix. Corneal rejection lines. What is specular reflection? Principle: It is based on Snells law. When angle of incidence of slit beam equals the angle of observation of microscope, the reflected light from epithelial and endothelial surfaces are viewed. Settings Beam height is full and beam width is narrow Microscope and slit beam are apart Movement Place the slit beam adjacent to reflection of slit lamp filament from surface of cornea corneal light reflex.

Slit beam is moved laterally until it overlaps corneal light reflection. Beam is moved further laterally to edge of corneal light reflection and focus on posterior corneal surface to visualize the paving stone like mosaic of endothelial cells. What specialized examinations can be carried out with the help of slit lamp? Diagnostic examinations: i.

Gonioscopy ii. Fundus examination with focal illumination iii. Pachymetry iv. Applanation tonometry v. Ophthalmodynamometry vi. Slit lamp photography vii.

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Laser interferometry viii. Potential acuity meter test. Therapeutic uses: i. Contact lens fitting. Yag capsulotomy iii. Delivery system for argon, diode and YAG laser as for retinal lasers, peripheral iridotomy, ALT, synechiolysis, suturolysis. Corneal and conjunctival foreign body removal. Corneal scrapings. Intraoperative slit lamp illumination: There is less risk of phototoxicity because a slit light at 5, focused on the macula, provides a fixed illumination of lm, the same as with an intraocular fiber placed at 17 mm from the macula.

Describe optics of slit lamp. Composed of two optical elements: Objective Eyepiece Objective lens consists of two planoconvex lenses. For good stereopsis tubes are converged at an angle of 10 to 15 Microscope uses a pair of prisms between objective and eye piece to re-invert the inverted image produced by compound microscope. Most slit lamps provides a range of accommodation from X6 to X Modern slit lamps use one of the following three systems to produce a range of magnification: i.

Czapskiscope with rotating objectives: a. Oldest and most frequently used. Different objectives are placed on a turret type of arrangement that allows them to be fairly rapidly changed during examination. Haag-Streit model, Bausch and Lomb, Thorpe model. Littmann-Galilean telescope principle: a. Developed by Littmann. Sits between objective and eyepiece lenses and does not require either of them to change.

Provide range of magnification typically 5. It is called galilean system because it utilizes Galilean telescopes to alter magnification. Two optical components are positive and negative lens f. Zeiss, Rodenstock, American optical slit lamp iii. Zoom system a. Allows continuously variable degree of magnification. Nikon slit lamp contains zoom system within objective of microscope and offers a range of magnification from X7 to X How to evaluate tear film with evaluation with the help of slit lamp?

Examination of inferior marginal tear strip can yield information about volume of tears. The tear strip is a line just above lower lid. It is normally 0. When thin or discontinuous, it is an evidence of deficient aqueous tear volume. The following are the parameters i. Beam angle 60 ii. Beam height maximum iii. Beam width parallel piped iv. Filter none v. Illumination low or ambient lighting only vi. Magnification X vii. Another feature seen in dry eye is increased debris in tear film. Bits of mucus, sloughed epithelial cellssuggestive of delayed tear clearance.

Alteration in morphology of conjunctivaconjunctivochalasis. Pathologic signs of Meibomian gland diseaseductal orifice pout or metaplasia white shafts of keratin in orifices , reduced expressibility, increased turbidity and viscosity of secretions. How to measure lesions with slit lamp?

Brightnesslowest intensity setting ii. Slit lamp beamslightly thicker than optical section iii. Illuminating arm directly in front of viewing arm. Focus vertically oriented beam on the lesion to be measured. Vary height of beam till it equals height of lesion. Read the scale. Rotate the bulb housing 90 to orient the beam horizontally and repeat measurement by varying height of beam to measure horizontal dimensions of lesion.

The bulb housing may be rotated less than 90 to perform diagonal measurement. Who invented direct ophthalmoscope? Invented by Von Helmholtz in Explain the procedure for examining with a direct ophthalmoscope. It is ideally performed in a dimly lit room. Patient is asked to look straight ahead at a distant object. Examiner should be on the side of the eye to be examined.

Patients right eye to be examined by the examiners right eye and scope to be held in right hand and vice versa. Examiner should first examine at an arms distance. Once the red reflex is appreciated, the examiner should move close to the patients eye and focus on the structures to be examined. Explain the optics of direct ophthalmoscopy. Principle: In emmetropic patients, the issuing rays will be parallel and will be brought into focus on the retina of the observer. Hence, light from the bulb is condensed by a lens and reflected off a two way mirror into patients eye. The observer views the image of patients illuminated retina by dialling in the required focusing lens.

At what distance is distant direct ophthalmoscopy performed? Performed at 2 feet one arms distance 5. What are the applications of distant direct ophthalmoscopy? To diagnose the opacities in refractive media. Exact location of the opacity can be determined by parallactic displacement. Opacities which move in direction of movement are anterior to pupillary plane and those behind will move in opposite direction. To differentiate between a hole and a mole of iris Mole looks black but a red reflex is seen through hole in iris as in iridodialysis.

To recognise the detached retina or a tumor arising from fundus iv. Bruckners test: In children, refractive error can be assessed by dialing the lens, the power of which will help us focus on the retina clearly. What are the different reflexes seen on distant direct ophthalmoscopy? Red reflex: normal ii. Grayish reflex: retinal detachment iii. Black reflex: vitreous hemorrhage iv.

Oil droplet reflex: keratoconus v. White reflex leukokoria : Retinoblastoma. Retinopathy of prematurity Congenital cataract Toxocariasis Persistent primary hyperplastic vitreous Retinal dysplasias Coats disease Choroidal coloboma. What are the factors determining the field of vision in direct ophthalmoscopy? Directly proportional to the size of pupil ii.

Larger area with least magnification is seen in hyperopes and smaller area with maximum magnification is noted in myopes. Inversely proportional to distance between observed and observers eye iv. Smaller the sight hole of the ophthalmoscope, the better the field of vision 8. What are the parts of direct ophthalmoscope? View aperture iii. Lens power indicator Rekoss disk iv.

Auxillary controlsred free filter, fixation target, slit beam, etc. What is the therapeutic use of direct ophthalmoscope? For xenon laser delivery How will you quantify disk edema using direct ophthalmoscope? The direct ophthalmoscope is first focused on the surface of the disk. The dioptric power by which the disk focusing is clearly noted. Then the ophthalmoscope is used to clearly focus on the adjacent retina. The dioptric power for this manouver is then noted. The difference between the dioptric powers gives the amount of elevation of the disk, i.

In emmetropic eye each diopter of change of focus is equivalent to an axial length of 0. What are the characteristics of the image formed? Vvertical ii. Eerect iii. What are the drawbacks of direct ophthalmoscope? Lack of stereopsis ii. Small field of view iii. No view of retinal periphery What is the magnification of direct ophthalmoscope? Magnification is 15X. What are the advantages of direct ophthalmoscope?

Safe ii. Portable iii. Screening tool iv. Easy technique What are the uses of auxillaries in direct ophthalmoscopy? Full spot-viewing through a large pupil ii. Small spot-viewing through a small pupil iii. Red free filter-change in retinal nerve fiber layer RNFL thickness iv. Identifying microaneurysms and other vascular abnormalities v. Slit-evaluating retinal contour vi. How do you find patients point of preferred fixation?

Reduce illumination intensity and dial in fixation target ii. Ask patient to look into the light in center of target iii. Determine whether the test mark falls on the central foveal reflex or at an eccentric location iv. Ask patient whether the fixed object is seen as straight ahead off or center. Who invented indirect ophthalmoscope IO? Nagel in What is the principle behind indirect ophthalmoscopy? Works on the principle similar to astronomical telescope. The principle is to make the eye highly myopic by placing a strong convex lens in front of the patients eye.

The emergent rays from an area of the fundus is brought to focus in between the lens and observers eye as a real inverted image. What are the different types of condensing lens used in indirect ophthalmoscopy? Planoconvex lens ii. Biconvex lens iii. Aspheric lens 4. What are the advantages and disadvantages of different type of lens? Planoconvex lens Advantage: causes less reflex during examination.

Disadvantage: plane surface of the lens causes troublesome reflexes when held facing the observer, so convex side should face towards the observer. Advantage: i. Helps to obtain less magnification and greater field ii. Minimize aberration iii. Can be used with small pupil and extremely iv. Complicated retinal topography 5. What are the different power of the lenses which could be used as condensing lenses? The various lenses used are: i. It has shorter working distance and is useful when examining patients with small pupil. What is the power of accommodation during the examination? The working distance is approximately one-third of a meter.

This setup enables emmetropic observer to use only 1D of their accommodation to view the image in the condensing lens. Myopes can increase or decrease their plus power to suit their refraction. Presbyopes will need the equivalent of an immediate range add or their addition for near. Hypermetropes will need their distance correction. Where is the image formed in IO? It is formed between the condensing lens and the observer. Compare between different condensing power.

What are the advantages of indirect ophthalmoscopy?

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Larger field of retina can be seen ii. Lesser distortion of the image of the retina iii. Easier to examine if patients eye movements are present or patients with high spherical or refractive power iv. Easy visualization of retina anterior to equator v. It gives a three-dimensional stereoscopic view of the retina vi.

Useful in hazy media because of its bright light and optical property. What are the disadvantages of indirect ophthalmoscopy? This is very less when compared to DO which is 15 times. Indirect ophthalmoscopy is difficult to perform with small pupil. Uncomfortable for the patients due to intense light and scleral indentation. The procedure is more cumbersome, requires extensive practice both in technique and interpretation of the image visualized.

Reflex sneezing can occur due to exposure to bright light. Discuss the relative position of the image formed in emmetropic, myopic and hypermetropic eyes. Emmetropiathe emergent rays are parallel and thus focused at the principal focus of the lens. Hypermetropiathe emergent rays are divergent and are therefore focused farther away from the principal focus. Myopia the emergent rays are convergent and are therefore focused near the lens.

What are the color coding for fundus drawing? For example: i. Optic disk. Lattice degeneration blue hatchings outlined in blue viii. Retinal pigment. How to perform indirect ophthamoscopy? Explain the procedure to the patient ii. The patient should be lying flat on a stretcher without flexion or extension of the neck in a dark room iv. The examiner throws light into patients dilated eye from an arms distance v. Binocular ophthalmoscope with a head band or that mounted on a spectacle frame is employed vi. Keeping eyes on the reflex, the examiner then interposes the condensing lens in path of the beam of light close to the patients eyes and then slowly moves the lens away from the eye until image of the retina is clearly seen.

Patients with sight will then use visual stimuli from his hand for fixation in addition to proprioceptive impulse. This is important in case of blind, monocular or uncooperative patients. The examiner moves around the head of the patient to examine different quadrants of the fundus. He has to stand opposite to the clock hour position to be examined.

For example, to examine inferior quadrant 6 oclock , the examiner should stand towards patients head 12 oclock. The whole peripheral retina upto the ora serrata can be examined by asking the patient to look in extremes of gaze and using a scleral indentor. How to use scleral indentor? It consists of a small curved shaft with a flattened knob like tip mounted on a thimble. It can be held between the thumb and the index finger or it can be placed upon the index or middle finger. The examiner should move the scleral depressor in a direction opposite to that in which he wishes the depression to appear.

Should be rolled gently and longitudinally over the eye surface. What is role of scleral indentation in examination of fundus? Make visible the part of the fundus which lies anterior to the equator. Making prominent the just or barely perceptible lesions of peripheral retina. What are the factors affecting the field of view?

Patients pupil size ii. Power of the condensing lens iii. Size of condensing lens iv. Refractive error v. Distance of the condensing lens held from the patients eye. How to calculate the magnification of image? What is the advantage of X-ray skull in ophthalmology?

AN EYE ON NUMBERS: A READY RECKONER IN OPHTHALMOLOGY

The advantages of plain X-ray skull when compared to other investigations like CT scan are: a. Low cost b. Easy availability and usage c. Preliminary test to detect gross abnormality. What are the important structures in X-ray skull to be looked for in ophthalmology? Most important structure to be looked for is the base of the skull. In this the pituitary fossa is the most important structure.

Other land marks are the Anterior clinoid process Planum sphenoidale Chiasmatic sulcus Tuberculum sellae Floor of the pituitary fossa Dorsum sellae and Posterior clinoids. Occasionally the pituitary fossa is deep and extend more in the vertical direction than in the antero-posterior direction and this has been termed the J-shaped sella and has no pathological significance. When do normal vascular markings of the skull become prominent? Arterial markings in the skull are usually visible as thin wavy lines and may become marked when the external carotid branches supply a vascular lesion like a meningioma or an arteriovenous malformation.

What are the abnormalities to be looked for in plain X-ray skull? Fracture ii. Bone erosion: Local, e. Pagets disease iii. Abnormal calcification: Tumors, e. Midline shift: If pineal gland is calcified v. Signs of raised intracranial pressure: Erosion of posterior clinoids. What are the causes of normal calcification in the X-ray skull? Structures in the midline that produce calcification are: Pineal body Falx cerebri The pacchionian granules, and The labenular commissure. His Selected Work on the Treatment of the of cataract in Europe 22, He was an itinerant couch- 4.

The emergence of the new human er, who travelled across Europe and made cat- eye anatomy and improvements in aract extraction in the central markets of the cataract surgery towns, having around a full audience. Jacques Daviel fig. Sir Nicholas Lloyd Ridley It is unclear how he that the eyes of pilots from the Royal Air Force penetrated the eye or how he removed the lens, who underwent injuries with fragments of PMMA but it is for sure that he used to make a small were well tolerated and were not rejected.

Thus, incision at the level of the conjunctiva and cov- he was inspired to use intra-ocular lenses made er the other eye with a bandage 8. Certainly of PMMA in cataract surgery, to correct apha- there were numerous postoperative complica- kia One year later, Dr. Ridley carried out the mous for his incision on the cornea. In , first intra-ocular lens in the U. The modern era of cataract surgery patients. The artificial intra-ocular lens rehabilitation of patients with cataract, this in- In the 20th century, Sir Nicholas Lloyd Rid- tervention becoming the most common and suc- ley Figure 5 was the first British cessful ophthalmologic surgery The modern technique of phacoemul- cataract.

The extra-capsular extraction of the cataract ECCE Figure 6 with IOL implant of poste- rior chamber consisted in extracting a portion from the anterior part of the capsular bag, the nucleus and the crystalline cortex, leaving the posterior capsule intact Starting from these techniques used at the beginning of the 20th century, the phacoemulsi- fication technique was developed.

In , fig. Kelman , an American Personal collection Dr. In , he received drogel that can be rolled, implanted through a the national medal for technology, from Presi- micro-incision of 1 mm. The creation of a dent George W. The phacoemulsifica- The multifocal IOL provides good vision at far, tion of the nucleus with the help of a probe of intermediate or near distance.

The femtosecond laser - asissted through the irrigation-aspiration technique The small incisions be- rior segment. The ultra-short focused impulses came a standard in phacoemulsification sur- sec do not produce collateral lesions of gery. It results in the formation of plasma, which covery and safe post-surgery results 8.

The force 6. The latest acquisitions in cataract of these cavity bubbles determines the separa- surgery tion of the tissue or its fragmentation The artificial crystalline The cataract surgery assisted by the laser Depending on the material they are made femtosecond is a procedure carried out in two of, there are three types of IOL: rigid non- stages. Immediately or hours after the tion, in order to see the lens, the anterior and laser treatment, the fragmented nucleus under- posterior chambers and the capsular bag through goes phacoemulsification A special vacuum device is This technique seems to be a safe, efficient positioned at the level of the cornea to make and predictable procedure, but other prospec- vacuum in the anterior segment, creating a tive studies will prove the benefits of the clini- pressure of mmHg that does not create cal potential of this technology which is still discomfort or sight loss during the procedure.

The surgeon sets the type of capsulorexis he wants according to the pupil dilatation and the concLUSionS type of nucleus fragmentation according to its Cataract surgery is the most commonly per- toughness. Carrying out capsulorexis by laser formed surgical procedure in the world, which takes between 1.

After the completion technology, which makes this surgery safer and of the laser treatment, the vacuum device from allows patients to heal faster. ISBN: Online , p.

Elgood C. Good Mason J. Volume 3, Baldwin, Cradock, and Joy, London, p. Heister L. Bellan L. Ascaso FJ, Huerva V. The History of Cataract Surgery.

Meaning of "stenopaeic" in the English dictionary

Cataract Surgery, , on-line, Cotallo JL, Esteban M. La catarata en la historia de la humanidad de la prehistoria al siglo XX. Cambridge, Mass, Blackwell Science, Fishman RS. The History of Ophthalmology. Bull Hist Med, , Chan CC.