Ophthalmic practitioners traditionally have invented and modified instruments and equipment to meet special needs and work situations in developing nations.1,2
The indirect ophthalmoscope is an indispensable tool in the ophthalmologists armamentarium. Frequently used in clinical office and surgical ophthalmology, it is less often required but often necessary in field work at rural health facilities. Indirect ophthalmoscopy is nevertheless an important adjunct in rural eye work in developing countries, particularly in ocular morbidity and blindness surveys.
Ocular field surveys often require that eye teams work in remote areas without the benefit of amenities and services, including electricity. Ophthalmic examining instruments and diagnostic equipment which require mainline electrical power are useless in such situations unless a portable electrical generator is available. Likewise, instruments which operate on rechargeable power units have limited usefulness. For field work in remote settings, battery powered ophthalmic instruments are most practical.
It is possible to convert a standard electrical indirect ophthalmoscope to battery power with little effort and a few simple tools. A description follows.
METHODS AND MATERIALS
The indirect ophthalmoscope, powered by mainline 110 volt electrical current through a step-down 6 ? transformer, is converted to a completely portable unit powered by four 1.5 "D" cell batteries. Three indirect ophthalmoscopes, so modified, were successfully used for ocular examinations in the Lower Shire Valley of southern Malawi during a field ocular survey from September to November 1983.
FIGURE 1: Plastic tubing 24 x 3.25 cm diameter, spliced insulated copper wiring to bathtub stoppers and furniture leg floor taps, and the electrical switch connected into one section of wire. Standard electrical tape is pictured at the bottom.
FIGURE 2: The tube assembly with wiring and electrical switch positioned in place with electrical tape. The position of the furniture leg floor taps connected to the insulated copper wiring in bathtub plugs is shown.
FIGURE 3: Four "D" cell batteries, yielding 1.5 volts each, for a total of 6 volts, power the unit. This substitutes for the mainline HOv or 220-24Ov power stepped down through a transformer to 6v. which has been removed.
FIGURE 4: The indirect ophthalmoscope and its portable pack in carrying case.
Necessary supplies are:
* Plastic tubing 24 cm long and 3.25 cm in diameter;
* One roll of 2.0 cm wide electrical tape;
* One small electrical switch;
* Two 20 cm lengths of insulated electrical copper wiring;
* Two rubber bathtub plugs;
* Two metal floor taps (for table and chair legs);
* One 6v electrically-powered indirect ophthalmoscope;
* An awl or similar sharp-pointed instrument (Figure 1).
The step-down transformer (used to convert HOv or 220v current to 6v current) is removed from the electrical wiring of the instrument by cutting the electrical leads just proximal to the transformer. The two exposed insulated wires which remain attached to the indirect ophthalmoscope will be attached to the new portable battery-power pack.
A small hole large enough to admit the insulated copper wire is created in the center of each bathtub stopper with the awl. The 20 cm length of wire is passed through each hole. The ends of both wires are bared by stripping the insulation back 1.0 cm from the end of each. The bared end on the recessed side of the bathtub stopper is then secured to one prong of the furniture floor tap. The tap is then forced through the rubber stopper, and the prongs of the tap are bent over to form a firm, tight grip on the stopper. Repeat this procedure with the second wire, bathtub stopper, and furniture floor tap (Figure 2).
The electrical switch is spliced into one of the wires passing from the rubber bathtub stoppers and floor tap assembly.
The two bathtub stoppers with attached electrical metal contacts close the battery tubing assembly, one at each open end. The furniture leg floor taps become electrical contact points for the four "D" cell batteries (Figure 3). If the stoppers are loose and do not fit firmly against the batteries, then electrical tape can be placed over the stoppers in the ends of the tube assembly to secure the stoppers tightly. The two-way switch may be taped to the body of the tube.
This unit is fully portable and does not require mainline electrical current for operation (Figure 4), making it ideal for use in field conditions in developing nations.
1. Koppert HC, Berkenfeld HH ChM, Folmer HR: Intermediate technology in ophthalmology, Royal Tropical Institute, 1092 AD Amsterdam, The Netherlands, 1985, pp. 3-32.
2. Schwab L, Whitfield R: Appropriate ophthalmic surgical technology in developing nations Ophthalmic Surg, 1982; 13(12):991-993.