This series will not only deal with instruments for use in orthoptic / ocular motility clinics / strabismologists' offices but also in those ophthalmologists' offices who are even slightly interested in diagnosing strabismus and other ocular motility disorders. The list for the latter is given first in the following text.

1. List of instruments that are a must for every ophthalmologist who is interested in diagnosing cases of strabismus, amblyopia and related disorders:

1. Vision testing charts including those required for young children, e.g., C, E, animals etc.
2. Maddox Wing
3. Maddox Rod
4. Prisms, if possible the Prism Bars set
5. Diplopia Goggles
6. Wirt's / Titmus stereotest
7. Fixation objects: wooden tongue depressors with small pictures on both ends to attract children's attention, otherwise a pen will do.
8. RAF Near Point Rule
9. Ophthalmoscope with a fixation target like star or small circle
10. Retinoscope
11. Trial set and frame
12. Worth Four Dots Test (may be incorporated in the test types drums etc.)

2. List of additional items for a full scale orthoptic/ strabismologist's / ocular motility clinic:

1. Major amblyoscope, e.g., synoptophore
2. Hess / Lees / Lancaster screen
3. Allen's preschool vision testing cards
4. Neutral density filter
5. Occluders for cover test
6. Bagolini's striated lenses
7. Hallberg's clip-on lens holder
8. Translucent occluder of Spielmann
9. Maddox Cross if there is enough space in the office
10. Maddox Double Rod (binocular)
11. Maddox Rod with prisms (binocular, hand-held)
12. Diploscope
13. Deviometer

NOTE: The items given in the list 2 are optional although one would prefer to have items 1 to 6, particularly the major amblyoscope (e.g., synoptophore), as this instrument gives information that is not available by any other examination. Description and uses of each instrument will be given in future editions of InteRycs.

STRABISMUS SUMMARY SERIES PART XVI

Getting familiar with orthoptic instruments: Part 2

1. Vision testing equipment / charts / projection devices

1. Those for adults and older children: Examples: Snellen's charts (for near and distance) and Logmar charts. It is important to test the distance VA as well as the near VA.
2. Those for preschool children and illiterates:

1. Hundreds and thousands sweets: It can be used as a qualitative test in preverbal children between the ages of 15-20 months. The test is done at if the child tries to pick up a sweet, the VA is at least 6/24 at 1/3^rd of a meter.
2. Stycar Rolling Balls: The test is done at 3 meters. The size of the balls ranges from 3.5 mm to 6 cm. The minimum age limit is 6 months.
3. Catford drum: It has dots of various sizes corresponding to Snellen optotypes. The visual acuity tested with it ranges from 2/60 to 6/6.
4. Sheridan Gardiner test: It is a single optotype test. The child looks at one letter at a time. It tests VA ranging between 6/60 to 6/3. The lower age limit is an intelligent 2 and one 1/2 years old.
5. Sonksen Silver test: The basis of this test is the "crowding phenomenon". It tests linear VA in which the child looks at several letters at a time. In cases of amblyopia the angular VA (with single optotype testing as in Sheridan Gardiner test) is better that the linear VA as in various charts. This is because of the crowding phenomenon found in cases of amblyopia.
6. Kay pictures: Children look at the various pictures and name the object.

3. Those for infants:

1. Fixation preference test
2. Grating acuity test
3. Optokinetic nystagmus (OKN) test
4. Visual Evoked Potentials (VEP)