A new lens-holder to facilitate slit-lamp bio-microscopic-aided fundus and gonioscopic examination

Introduction

Fundus examination using a slit-lamp bio-microscope is an integral part of any comprehensive ophthalmic examination. One of the slit-lamp-mounted lenses used is Hruby lens.[1] Slit-lamp mounted lens-holders mainly assisting in the fundus examination[2] and in slit-lamp fundus photography.[3] Goldman's Plano-concave contact lens was also used earlier.[1] However, doubly aspheric noncontact convex lenses of varying Diopters (60D, 78D, and 90D) have superseded the Hruby lens. Gonioscopy is an integral part of office glaucoma evaluation and several gonio-lenses are available that include single mirror, 2-mirror lenses, Goldman 3-mirror lenses, Zeiss 4-mirror lens, and Posner lens. A universal adjustable slit-lamp mounted lens-holder has been described for use with the four-mirror gonioscopy lens.[4] Most of the lenses are either hand-held directly or may have a long handle. All gonio-lenses require some degree of rotation during the examination including the four mirror lens. Several Gonio-lenses are also used for laser procedures requiring a longer duration of use. Some lenses have serrated side edges, providing grip for traction, particularly useful in patients with deep-set eyes or protruding orbital rims. A small section of a Penrose drain facilitates gripping the lens better and reduces the chance of edge getting chipped if dropped accidentally.[5]

Steady mount lens holders do not allow fine tilting of the lens to avoid unwanted reflected glare. Mounting also does not allow ease of use with both hands. They make the slit-lamp bulkier and lesser patient-friendly. Although portable, they occupy space and require set-up time. The handles used for the 4-mirror gonioscopy lenses and Posner lenses require a significant learning curve, are long, bulky and may also be visually threating. These designs also do not allow good lens maneuverability during the manipulation of the patient's lids and during rotation of the lens.

Instrument description

The instrument consists of three parts [Figure 1], an incomplete ring shaped like a tennis racket with its terminal limbs a screw and a key chain with a complete ring on one end to pass the finger through the ring and a hollow bulbous shaft into which the terminal limbs of the ring enclosing the lens are introduced. The screw on the side of the bulbous shaft is tightened which also simultaneously links the ring (Lens) with the key chain. The diameter of the incomplete ring that holds the lens is 26.5 mm. The length of each terminal limb is 8.5–9 mm. The screw measures 9 mm to 10 mm. The diameter of the complete keyring is 25 mm. The length of the bulbous tip is 10 mm. The chain measures 4.5 cm. The entire instrument measures 9.5 cm (95 mm). The components and the steps involved in assembling and using the holder are described in detail in Figures 1–3.

Figure 1.

Components of the new universal lens holder (key chain design). (Ia) represents ring. (Ib) represents the terminal limbs. (Single headed arrow) (II) represents the screw. (Black vertical line) (IIIa) represents shaft (double headed arrow). (IIIb) links the shaft and the ring. (IIIc) represents the ring (A) (Single headed arrow) represents total and (double headed arrow) represents the chain length. (B) Assembled lens holder (C and D)

Figure 3.

Universal lens holder for Zeiss 4 mirror lens. The limbs are introduced in to the shaft. (a) And the screw is tightened (b) the assembled universal lens holder with the 4 mirror lens. (c) The lens is shown suspended (d) and is ready for examination (e)

Figure 2.

Using the universal lens holder for the 90 D lens. The ring encloses the 90 D lens. (a) The lens ready for examination. (b) The lens suspended form the holding finger (c) and the lens with holder in case (d)

Hence, this new but familiar design (Key Chain design) of lens-holder will facilitate slit-lamp bio-microscopic-aided fundus and gonioscopic examination not only for beginners but "also for experienced ophthalmologists" in examining children, uncooperative and elderly patients, and in performing lengthy laser procedures.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.