LENSES IN OPHTHALMOLOGY

In slit lamp biomicroscopy

Two typesA. Non contact1. Planoconcave lens2. Biconvex lensB.Contact 1. Goldmann three-mirror lens2. Goldmann posterior fundus contact lens3. Panfundoscopic lens4. Mainster lens

A. Non contact1.Hruby lens•Incorporated onto slit lamp•High negative power lens -58.6D•A broad vertical slit beam is first rotated to illuminate the fundus from vertically a straight on oculars•The lens is centered on the cornea a few mm away from the patients eye until fundus comes into view•Image-upright and vertical •Image quality not uniformly good ,blurred at the margins•Used almost exclusively to view the posterior pole

2.Aspherical lenses• 60D,78D,90D• Real ,inverted ,high

quality image • High powered plus lens• Higher power lenses

provide wider fields of view at the expense of magnification

Feature Feature 60D60D 78D78D 90D90D

Magnification Magnification X1.18X1.18 X0.95X0.95 X0.75/0.77X0.75/0.77

Field of viewField of view 76 deg76 deg 84deg84deg 94/95deg94/95deg

Focal lengthFocal length 19mm19mm 15mm15mm 12mm12mm

Clear lens Clear lens apertureaperture

30mm30mm 29mm29mm 19mm19mm

Condensing lenses in IDO

Feature Magnification Field of view Uses

15D 4x 40 deg Examination of posterior pole

20D 3x 45deg General examination of fundus

25D 2.5x 50deg

30D 2x 60deg Shorter working distanceSmall pupils

40D 1.5x 65deg Small children

Retinal laser lenses

Some common characteristics of the laser lenses are:• Concave posterior surface conforming to the corneal

curvature and a flat or convex anterior surface• Planar mirrors allowing observation of the anterior

chamber angle or peripheral retina.• A prism to allow visualization of the mid-periphery of the

retina.• A flange to stabilize the lens and prevent blinking• Knurled edge to facilitate lens manipulation.• Laser lenses generally consist of a conicalpolymethylmethacrylate or aluminium shell• Glass anterior surface, lenticular elements and mirrors.

• Antireflection coatings are usually applied to each optical surface in a laser lens that reduces reflected white light

• The hazard distance is 7 meters for an uncoated lens and 1.6 meters for a coated lens.

• Most laser lenses use broad-spectrum, multilayer,antireflection coatings that reduce reflected light between 400 nm and 700 nm from approximately 4 % to less than 1%

Two types

1. Non contact

2. Contact

a) Lenses with mirrorsa) Goldmann three mirror lens

b) Lenses without mirrorsb) Mainster lens

c) Panfundoscopic lens

Goldmann 3 mirror lenses.

• Centre lens- 64 dioptre lens-for posterior pole

• Trapezoid mirror-retina slightly posterior to equator(73 deg)

• Half round mirror-peripheral retina from equator out to the ora serrata (67 deg)

• Thumb nail mirror-59deg- for AC angle

• Contact surface diameter-12mm

Yannuzzi fundus lens• It is a modification of an earlier

model developed by Krieger in 1966 designed to facilitate macular photocoagulation.

• It has a concave corneal surface which is steeper and of greater diameter, so also has a better optics than a simple Goldman fundus lens.

• The concave corneal surface allows posterior lens pressure to be transmitted to the sclera without distorting the cornea.

• It produces an erect, virtual ophthalmoscopic image located

• in the anterior vitreous humor.

Four mirror contact lens

• 80 deg –region of major vascular arcades

• 76deg-midperiphery and equator

• 67deg-peripheryand vitreous base

• 62deg-ora serrata and iridocorneal angle

Panfundoscopic lens• Rodenstock• Meniscus lens coupled with a

spherical lens located within the same lens holder housing

• Inverted,real,minified image• Located well forward of the ant

surface lens surface• Wide angle view from fovea to

equator• Examination thru Poorly

dilated pupil• Photocoagulation than

diagnostic purpose as image is small and periphery blurred

Mainster lens• 1986• This lens has more field of view

(58%• Greater than Goldman) and a

greater magnification. • Field of view is 14% less than

the Panfundoscope, • The lateral and axial

magnification are better which makes it useful for detecting retinal thickening.

• It has a biconvex, aspherical anterior lens element and a concave lens element to fit the corneal curvature.

• It produces an inverted, real image located in front of its biconvex aspheric anterior lens element

Mainster Standard lens• This lens is designed for focal and

grid laser treatment from the posterior pole to the midperiphery.

• The field of view is 90deg/121deg.• Image magnification is 0.96x.• Laser spot magnification is 1.05x.• High resolution, high magnification of

image allows appreciation of subtle intra-retinal details and retinal thickening.

• for diagnosis and treatment of macular oedema, branch retinal vein occlusion, choroidal neovascular membrane in age-related macular degeneration and presumed ocular histoplasmosis

• .

Mainster wide field lens• This allows a very wide range

of slit lamp magnification to be used.

• It has excellent ophthalmic resolution and image binocularity is maintained across the entire field of view.

• It is used for panretinal photocoagulation in proliferative diabetic retinopathy.

• The field of view is 118deg/127deg.

• Image magnification is 0.68x.

• Laser spot magnification is 1.50 x.

Volk Quadraspheric lens • The preferred wide field fundus laser lens for

diagnosis and treatment of the retina. • The four aspheric surfaces also employ high-

efficiency antireflection coatings thereby improving lens performance by reducing astigmatism across the entire field of view.

• It also enhances visualization through a small pupil.

• It produces an inverted and reversed image.• Its sleek 28.6mm diameter housing• provides a definite advantage over

competitive wide field lensesfor peripheral retinal viewing, reflection displacement and ease of use.

• The laser spot magnification is 1.97x • the image magnification is 0.51x.

Abraham iridectomy lens

• Abraham iridectomy YAG laser lens that consists of a modified Goldmann type fundus lens

• with a 7.50 mm diameter +70 D plano-convex lens bonded to the anterior surface.

• It has an anodized light metal rim, that gives a firm grip on the lens.

• The +70 D button lens helps in condensing the laser energy, so that the procedure can be carried out at lower power settings.

Paymen Capsulotomy YAG Laser

Lens 

• paymen capsulotomy YAG laser lens.

• These are used as devices for ND-YAG laser posterior capsulotomy and anterior vitreolysis.

• Features: • The +30D lens condenses the laser energy

1.Goniolens-Direct

• Koeppe-prototype diagnostic goniolens.

• Richardson-Schaffer-Small Koeppe lens for infants

• Barkan-prototype surgical goniolens

• Swan Jacob-surgical goniolens for operating room.

• Thorpe-surgical and diagnostic goniolens for operating room.

• Layden-for premature infant gonioscopy

• Worth goniolens-Anchors cornea by partial vacuum.

• Sieback goniolens-tiny goniolens which floats on the cornea

Indirect Goniolens

• Two basic designs-

• Goldmann type and

• Zeiss type

Goldmann type

• Truncated cone shaped device which utilizes mirrors to reflect light from iridocorneal angle into the direction of observer

• 3 mirror lens gives both an erect virtual image of the fundus as well as indirect view of angle as in a mirror.

• The small curved front surface does not rest on the cornea ,but instead it vaults over it with a lubricating fluid filling the gap

• Border of front surface rest on sclera

Goldmann type

• Centre lens- 64 dioptre lens-for posterior pole

• Trapezoid mirror-retina slightly posterior to equator(73 deg)

• Half round mirror-peripheral retina from equator out to the ora serrata (67 deg)

• Thumb nail mirror-59deg- for AC angle

• Contact surface diameter-12mm

• View obtained is less than that of Koeppe lens

• Can be used with the patient sitting upright• Single mirror lens with antireflective

coating-laser trabeculoplasty,enables a wider view of angle

• 4 mirror lens available •

• Modified Goldmann type lens• Radius of curvature 8.4mm

• Does not need viscous bridge

• Anti reflection coating

• Can be used for laser trabeculoplasty

Zeiss type

• Uses similar method to Goldmann• But employs prism in place of mirror• 4 symmetrical prisms tilted at 64 deg. allow

visualization of iridocorneal angle in 4 quadrants simultaneously.

• Smaller contact surface diameter [9mm]-rests on cornea without requiring lubricating fluid.

• Allows indentation gonioscopy

Zeiss type

• Original model mounted over a holding fork(unger holder)

• Newer models with attached holding handle-

• Posner 4 mirror-modified Zeiss with attached handle

• Sussmann-hand held Zeiss type

• Thorpe 4 mirror-4 mirror at 62 degrees,requires fluid bridge

Ritch trabeculoplasty lens

• 4 mirrors

• 2 at 59 degrees 2 at 62 degrees

• With a convex lens over one mirror of each set

Trabeculens

• 4 mirror lens at 62 degres

• 30 D convex lens in a hollow tunnel

• Can be used as a diagnostic gonioprism

• Useful in trabeculoplasty and iridectomy

Feature Feature 4 mirror 4 mirror lenslens

Mainster Mainster ultra fieldultra field

Volk Volk super super quad XLquad XL

Volk Volk quadraspquadrasphericheric

Field of Field of viewview

Central Central 30deg30deg

Mirror Mirror 120 deg120 deg

140 deg140 deg 160deg160deg 130deg130deg

MagnificaMagnification tion

< x1< x1 0.530.53 0.520.52 0.530.53

Image Image locationlocation

Ant vitAnt vit AirAir AirAir AirAir

ImageImage Erect Erect mirror mirror imageimage

Complete Complete inversioninversion

Complete Complete inversioninversion

Complete Complete inversioninversion

Feature Feature 4 mirror 4 mirror lenslens

Mainster Mainster ultra fieldultra field

Volk Volk super super quad XLquad XL

Volk Volk quadrasquadrasphericpheric

OpticsOptics DirectDirect IndirectIndirect IndirectIndirect IndirectIndirect

Aperture Aperture diadia

30mm30mm 30mm30mm 30mm30mm 26mm26mm

Lens Lens PlanocoPlanoconcave+mncave+mirrorirror

Concave Concave convex convex ant ant surfacesurface

Concave Concave convex convex ant ant surfacesurface

Concave Concave convex convex ant ant surfacesurface

Surface Surface reflectionreflection

++ ++++++ ++++++ ++++