You can further restrict the substitution within the catalogs by using the glass substitution template, under Tools...Optimization...Glass Substitution Template. Make sure to check the “Use Glass Substitution Template” box; if you do not, then all glasses in the catalog will be considered for substitution, as in the previous exercise.   

The substitution template uses data in the glass catalog such as “relative cost” and “status” to filter the glasses. For example, it if often advantageous to check the “Preferred” option,since Preferred glasses are usually frequently melted glasses, and more likely to be available upon demand.

To see the data or status for a particular glass, open the glass catalog window by clicking Tools...Catalog...Glass Catalog in the main ZEMAX menu.

The glass catalog gives the glass status, which can be Standard, Preferred, Special, Obsolete or Melt. Unless you really need to choose otherwise, always select 'Preferred' glasses only, as these are the lowest cost, most chemically stable, most commonly used etc glasses. 

The glass catalog also lists relative cost (price poer unit weight compared to N-BK7), climate resistance, stain resistance, acid resistance, alkali resistance and phosphate resistance. By using the Glass Substitution Template, you can ensure that the glasses chosen meet other important criteria rather than just optical criteria.